The SolarPACES Conference Proceedings cover the proceedings of the international SolarPACES conferences taking place annually.
TIB Open Publishing (Technische Informationsbibliothek (TIB))
Developing a Model for Quantifying Heat Loss From a Molten Salt Thermal Storage System
Thermal energy storage (TES) systems are integral to concentrated solar power (CSP) plants. A major design consideration for TES systems is the tank's storage temperature. The tank cools over time due to heat loss through its boundaries. This paper presents a model for tracking and quantifying heat loss through the tank's floor, walls, and roof. The heat transfer mechanisms incorporated in the model are convection, conduction, and radiation. The performance of the developed model is validated against previous studies and used to understand the effect of the fluid level on tank losses. The model serves as a tool to compare different thermal energy storage (TES) system designs and gain insights into which minimises the heat loss. The paper details the modelling assumptions, methodology, and validation results. The model is intended for comparative assessment during conceptual design, enabling rapid evaluation of TES configurations where relative differences matter more than absolute precision.
Copyright (c) 2026 Mu-een Khan, Stephen R Clark, Craig McGregor https://creativecommons.org/licenses/by/4.0
Multicriteria Comparison of two Different-Nature Fillers for High Temperature Sensible Heat Storage
The most suitable materials for thermal energy storage should combine low cost, high thermal capacity, high charging and discharging velocities, compatibility with the plant components in which they are integrated and, long-term durability. The use of solids to fill packed beds where the heat enters and leaves through a heat transfer fluid (HTF), is a solution that provides satisfactory amounts of energy density at low cost. In this work, two solid materials of different nature were comparatively tested at device level with air as HTF and according to various criteria. Material A is manufactured from recycled waste and tailored to improve its thermal properties, while material B is a natural, cheap and highly available in nature (pebbles). Material B showed significant mechanical strength problems at temperatures above 500 °C. Material A, instead, withstood well temperatures up to 850 °C under operating conditions. The comparative KPI revealed that material B has a slightly higher thermal capacity and a 4% higher energy efficiency than material A. However, these results lost validity after the first-round experiment with material B, since a strong degradation was detected affecting its physical properties and hindering its ability to store heat.
Copyright (c) 2025 Elisa Alonso Romero, Esther Rojas, Antonio Ávila-Marín, Margarita Rodriguez, Rocío Bayón https://creativecommons.org/licenses/by/4.0
TES Model for Hybrid Energy System Analysis
Long-duration energy storage (LDES) is essential for efficiently harnessing renewable energy. While electrochemical energy storage technologies have been increasingly deployed, they often face challenges due to high costs and limited mineral resources. Thermal Energy Storage (TES) offers a promising, cost-effective, and location-independent solution for LDES by storing energy as heat in inexpensive materials. A dynamic TES simulation tool within Flownex was developed to predict the TES outlet temperature for varying inlet conditions within a typical combined heat and power (CHP) system. The application of the dynamic TES model was demonstrated by successfully simulating the transient behaviour of a gas turbine cogeneration system for a 950°C gas turbine inlet temperature and ~18h TES energy storage duration. The model was used to evaluate the economic viability of a TES gas turbine cogeneration system compared to a lithium-ion (Li-ion) battery system for delivering the same output. An economic comparison over a 30-year project lifespan highlights the advantages of TES for LDES.
Copyright (c) 2025 Frikkie Botha, Willem le Roux https://creativecommons.org/licenses/by/4.0
Characterization of a Novel Coating Process to Darken Sand Particles
The use of solid particles in Concentrated Solar Power (CSP) plants can enhance energy conversion efficiency by elevating the working temperature. For this reason, many researchers are exploring various materials such as silica sand and SiC, among others, and methods to enhance the optical properties while cost is reduced. In this context, this study proposes a novel fabrication method based on the Mn2+ diffusion to darken silica sand particles and, therefore, enhancing their absorptivity. Colorimetry analysis reveals that the obtained particles color closely resembles that of the reference material SiC, while morphology analysis, Scanning Electron Microscopy (SEM), and X-Ray Diffraction (XRD) confirm an effective fabrication method.
Copyright (c) 2025 Leonel Mario Cerutti Cristaldo, Minerva Díaz Heras, Juan Carlos Pérez Flores, Jesús Canales Vázquez, José Antonio Almendros Ibáñez https://creativecommons.org/licenses/by/4.0
Development of a new PVt / PCM System for Heating and Power
This study presents a PVt/PCM design that combines heat exchanger and PCM storage to increase power output. The PCM first absorbs sensible heat and when it reaches the melting temperature, it absorbs latent heat and continues to melt. When the phase change is complete, the temperature of the PCM starts to rise. The design consists of a PCM tank under the PV panels and a PCM heat box. In this design-free PVt/PCM system, the thermal efficiency is enhanced by the ability of the PCM to store excess heat during peak radiation periods, and this stored thermal energy can then be released when needed, allowing heat to be used more consistently and efficiently. Energy balance equations were used to determine the thermal energy of the PVt during the summer day in the UK. MATLAB simulations show different heat conduction rates in PCMs. Thermal efficiency measures the system's effectiveness in converting solar energy into useful thermal energy. Incorporating PCM helps maintain PV cell temperatures, preserving electrical efficiency.
Copyright (c) 2025 Tugba Gurler, Taiwo Ayoade Idowu, Sarah Yasir, Zaharaddeen Hussaini, Christopher Sansom https://creativecommons.org/licenses/by/4.0
Progress and Prospects of TES for Central Receiver-Based CSP Plants
This review categorizes the thermal energy storage (TES) technologies—sensible heat, latent heat, and thermochemical storage—and evaluates their development, application, and performance within central receiver-based concentrated solar power plants. This study explores the progression of TES systems, delineating the evolution from technologies such as saturated steam and molten salt, first used in the Eurelios power plant in 1980 as a protective storage solution for 30 minutes, to commercial molten salt storage capacities of up to 15 hours. This study also examines emerging research and development technologies aimed at achieving higher efficiencies and operating temperatures. The objective is to identify technological trends, assess the efficacy of different TES systems, and highlight future directions for research and application.
Copyright (c) 2025 Brenda Hernandez Corona, Matteo Chiesa, Nicolas Lopez Ferber, Ahmad Mayyas, Nicolas Calvet https://creativecommons.org/licenses/by/4.0
Numerical Simulation to Investigate Thermal Stratification in an Energy Storage System Under No-Flow Condition
Thermal energy storage (TES) systems enhance the reliability of intermittent energy sources. The present work examines the thermal stratification in a thermocline storage system during charging and discharging with no fluid flows. With this goal, numerical simulations are performed on a storage tank consisting of a constant temperature heat source and sink. Molten nitrate salts mixture (60 % NaNO3+ 40 % KNO3) is used as storage material as it is thermally stable at higher temperatures (up to 565 °C). The thermocline behaviour of the numerical model is assessed during charging and discharging using constant temperature heating and cooling sources. In the present study, molten salts' lower and upper-temperature limits are 300 °C and 500 °C, respectively. The qualitative behaviour of thermocline formation and propagation during charging and discharging is analysed by temperature contours and axial temperature profiles. Quantitatively, the thermocline behaviour is analysed by two non-dimensional parameters: Stratification number (Str) and Mix number (MIX). It is observed that with a constant temperature heat source and sink, the tank remains stratified throughout the charging and discharging. The charging and discharging rates have been determined, and the results will be helpful in designing a lab-scale thermocline demonstration setup and further study.
Copyright (c) 2025 Kapil Kumar, Shireesh B. Kedare, Manaswita Bose https://creativecommons.org/licenses/by/4.0
JCA Eni ENEA Project: CSP & Thermal Storage
This project is framed inside a three-year-long cooperation between Eni and ENEA. It concerns the development of prototypes, technologies, innovative processes, feasibility studies, scenario analysis, exchanging skills, and know-how. This is coherent with the promotion of joint initiatives in the field of energy production, from renewable sources and those with low CO2 emissions, supercomputing, superconductivity, and circular economy, including innovative processes for waste valorisation and production of biogas, biomethane and biochar. The “CSP & Thermal Storage” has the ambition to exploit solar sources to produce thermal energy according to the energy demand, regardless of the availability of the solar source, through the development of innovative solutions of plants with a programmable production capacity, through the coupling with innovative Thermal Energy Storage (TES) solutions. The objectives of this project are the identification of contexts for using Concentrating Solar Power / Concentrating Solar Heat (CSP/CSH) technology and thermal generation systems coupled to TES, the definition of the "business plan" for the enhancement of these technologies, the identification of partnerships with national and international subjects for the design of industrial solutions in the identified contexts of interest, and the joint participation in competitive tenders through research and development projects that can also lead to the creation, characterisation, and validation of prototype units. As for the energy storage, dynamic modelling of the thermocline and Phase Change Materials (PCM) storage systems is also expected, together with a broad-spectrum analysis of possible applications of CSP/CSH coupled with TES along the entire industrial energy supply chain (e.g.: upstream, downstream, power generation). Of particular importance is the development of TES prototypes to be tested on a molten salt-operated circuit integrating two different PCM systems with an Eni proprietary innovative thermocline TES based on concrete, to facilitate the management of the system and to supply high-quality heat to the user. This system consists of a module able to store 40 kWh of thermal energy by phase change materials (PCM), followed by a concrete module of about 150 kWh and another 40 kWh PCM TES with a higher phase change temperature. The overall operating temperature range of the system is 290÷450°C.
Copyright (c) 2025 Raffaele Liberatore, Francesca Nana, Stefano Cardamone, Tamara Passera, Lino Carnelli, Valeria Russo, Adio Miliozzi, Daniele Nicolini, Giuseppe Petroni, Walter Gaggioli https://creativecommons.org/licenses/by/4.0
Performance Evaluation of FBRs for TCES Based on the CaO/CaCO3 and MnAl2O4/MnAl2O4-δ Systems
The following work presents an analysis of the fluidization conditions and performance of fluidized bed reactors working in the discharge phase for two different systems, namely CaO/CaCO3 and MnAl2O4/MnAl2O4-δ. It is well known that the discharge phase is the most critical one of the process. The two systems have been chosen for their different operating temperatures and fluidization properties, thereby allowing an evaluation of the feasibility of working with fluidized bed reactors under a range of operating conditions. The results show that though the MnAl2O4/MnAl2O4-δ system is capable of achieving a higher efficiency, the total amount of energy released by the solid per unit mass is significantly higher for the CaO/CaCO3 system.
Copyright (c) 2025 Maria Anna Murmura, Valentina Biagioni, Maria Cristina Annesini https://creativecommons.org/licenses/by/4.0
A Simplified Numerical Model to Study the Thermal Behavior of a Cascade LHTES System
To promote the integration of Solar Heat for Industrial processes (SHIP), through the development of innovative cascade Latent Heat Thermal Energy Storage (LHTES) systems, a simplified zero-dimensional model for “shell&tube” LHTES systems that is fast, flexible and sufficiently accurate was set up. This model, programmed in Fortran 90, was developed not only to predict the thermal behavior of a cascade LHTES but also to be usable within a software to evaluate its integration in any plant, including a Concentrated Solar Thermal (CST). The model was validated through a comparison both with a more sophisticated numerical simulation and the experimental results. Finally, the simplified model was applied to a case study to analyse the thermal behavior of a system of three LHTES connected in series
Copyright (c) 2025 Daniele Nicolini, Adio Miliozzi https://creativecommons.org/licenses/by/4.0
Hot Corrosion and Mechanical Performance of Aluminide Coated Austenitic Steel
The present study aims at improving coatings to allow higher operating temperatures – up to 700 °C – while resisting hot corrosion in future heat transfer fluids and storage systems for CSP technology. An aluminide coating was produced onto a 347H austenitic alloy to resist Li-Na-K molten carbonate corrosion at 700 °C. Multiple surface preparations were investigated and, after optimization, a new diffusion heat treatment was selected. A homogeneous 3-layer coating was formed with Al content reaching up to 69 at.% at the top surface. Corrosion was significantly decreased by the coating compared to the uncoated material. After 500h-exposure, a 100 µm-thick multi-layered and non-adhesive alkali elements rich oxide formed at the surface of uncoated 347H alloy. On the contrary, the coated material preserved its morphology and a mix of α-LiAlO2 and γ-LiAlO2 formed on the top coating. From the mechanical perspective, local hardness measurements highlighted a broad variation along the different layers of the coating. 3-point bending tests showed that deformation in the plastic domain was required to cause crack formation. Cracks remained in the two outermost layers of the coating and did not reach the underneath substrate.
Copyright (c) 2025 Loïc Oger, Alina Agüero, Pauline Audigié https://creativecommons.org/licenses/by/4.0
Hybridized Thermal Energy Storage Pilot Plant
An innovative hybridized Thermal Energy Storage (TES) technologies pilot plant at the Iberian Research Centre for Energy Storage Research (CIIAE) in Cáceres (Spain) has been designed by RPow in 2024 and will be built in 2025. The project design enables both individual and simultaneous research about charge-discharge operations based on Molten Salts (MS), Phase Change Materials (PCM) and Sorption. The plant design configuration allows in turn testing with different heat transfer fluids (HTF, initially Helisol5A) and thermoregulating fluids (nano-capsules or micro-capsules). Researching object belong to prototyping (TRL’s 4-5) and demonstration (TRL’s 6-7). Moreover, the early research carried out about desired functionalities during the engineering definition has made it possible a TES management identification, searching for a thermal integration between the different technologies. This strategy has provided an increased overall efficiency during the expected researching tests along the plant lifetime and the future exploration of real applications and synergies between the TES systems at different temperature stages from 30 – 565 ºC.
Copyright (c) 2025 Rafael Pérez Santana, Adrián Blindu, Patricia Santamaria Prado, Ángel Martínez Quesada, César Martín-Montalvo Sánchez https://creativecommons.org/licenses/by/4.0
Evaluation of Alternative Base Materials for Mitigation of Stress Relaxation Cracking in Thermal Energy Storage Tanks
Concentrating solar power (CSP) plants with thermal energy storage (TES) face challenges related to stress relaxation cracking (SRC) in molten hot salt tanks. While alloy 347H stainless steel (SS) is commonly employed due to its stress corrosion cracking (SCC) resistance and sufficient mechanical properties, it suffers from SRC in the weld region. This study explores alloy 1.4910 as a potential alternative, known for its superior creep strength and molten salt corrosion resistance. Thermomechanical testing using a Gleeble® 3500 physical simulator reveals promising results for alloy 1.4910 heat affected zone (HAZ) and 16-8-2 filler (ER16.8.2) fusion zone (FZ), with no cracking observed within a 22-hour test period at elevated temperatures ranging from 600 to 800°C and initial true stress conditions of 650 MPa (0.174 strain) for HAZ and 460 MPa (yield strength) for FZ. In contrast, alloy 347H HAZ and matching filler FZ experienced cracking within a few hours at 800°C. Metallurgical characterization and fractography are additionally conducted on cross welded 1.4910 samples with 16-8-2 filler and thermomechanical Gleeble® samples.
Copyright (c) 2025 Timothy Pickle, Joel Harvey, Theodore Vassi, Ravi Vishnu, Paul Janiak, Andy Backhouse, Sergio Davila, Bruce Leslie, Kurt Drewes, Zhenzhen Yu https://creativecommons.org/licenses/by/4.0
An Update on the Cost Comparison of Chemical and Thermal Storage for Power Generation in Namibia
Based on a previous study, this paper presents a new cost comparison between chemical and thermal energy storage application in power generation [1]. Despite the methodology of the analysis remaining the same as the previous study, the existing cost input data used in the previous study is updated with new cost input data derived from the latest bids received in the Battery Energy Storage System Project procured by Namibia Power Corporation in 2023. The study was derived from an electricity supply challenge within the Southern African Power Pool (SAPP). The unique mismatch between the supply and demand of electricity has caused extreme price variations during peak and off-peak periods. The objective of the study was to determine a suitable economical solution to counterbalance the effect of the extreme price variations. Following this cost comparison analysis, it can be inferred that thermal energy storage has become increasingly financially viable compared to chemical storage for power generation.
Copyright (c) 2025 Arno Pfohl, Ernst Krige, Benedictus Mingeli https://creativecommons.org/licenses/by/4.0
Increasing the Collaboration on Thermal Energy Storage Systems in SolarPACES TCP
This paper presents, mainly, the just recently launched collaboration topics in the Thermal Energy Storage Working Group (TES WG) of the SolarPACES task III. These topics are four: one dealing with the main issues related to molten salt loops, like for example, with the reliability of equipment and instrumentation used in this type of hydraulic loops; another in relation to TES tanks issues, like for example, the identification of failures at high temperature and solutions to implement in the tank design; another focussed on corrosion issues of structural materials used in molten salt loops and on how different coatings can be used for that, and finally another topic focussed on the used of TES not only by storing energy of a CST plant but of other non-dispatchable renewables, like PV or wind, in a Carnot battery.
Copyright (c) 2025 Esther Rojas Bravo, Rocío Bayón, Darío Alfani, Chuncheng Zang, Camila Barreneche, Ángel G. Fernández, Francisco J. Pérez-Trujillo https://creativecommons.org/licenses/by/4.0
Design Features and Material Selection Methodology of High-Temperature Particle-Based Thermal Energy Storage Bin
This study investigates the thermal performance of a proposed design for a particle-based thermal energy storage (PBTES) system. A small-scale TES bin was constructed using masonry materials and a multi-layered structure. The primary objectives were to quantify heat loss through the bin’s wall and to evaluate the thermal conductivity of the insulating material, calcium silicate (CS), at elevated temperatures. Heat transfer rates were measured and calculated using two methods, yielding a minimal discrepancy of 3% between the results. The thermal conductivity of the CS was determined to be 0.115 W/m·K, indicating its effectiveness as a thermal barrier. Additionally, the expansion joint (EJ) layer demonstrated the ability to recover its original thickness after cooling, confirming its utility in relieving stresses resulting from the thermal expansion of the inner layers. These findings support the scalability and efficiency of the proposed PBTES system design.
Copyright (c) 2025 Nader Saleh, Shaker Alaqel, Rageh Saeed, Eldwin Djajadiwinata, Hany Al-Ansary, Abdelrahman El-Leathy, Syed Danish, Zeyad Al-Suhaibani, Sheldon Jeter https://creativecommons.org/licenses/by/4.0
Thermal Wave Flow Meter for Molten Salts Flow Measurements
Flow measurements in molten salt are. Flow rate measurement using a thermal wave flow meter is a simple and reliable flow rate measurement not limited only to molten salts. The present study focuses on verifying and analyzing the thermal wave flow meter. Several flow meter settings were tested in order to evaluate flow meter accuracy and reliability. The flow meter was verified on a testing loop with water where an electromagnetic flow meter was used for a reference. First tests showed sensitivity of flow meter on heat pulse length and accuracy of peak location searching for a time delay evaluation.
Copyright (c) 2025 Jan Škarohlíd, Tomáš Kořínek, Radek Škoda https://creativecommons.org/licenses/by/4.0
Numerical Analysis on the State of Charge of an Ultra-High Temperature Latent Heat Thermal Energy Storage System
Ultra-high temperature thermal energy storage (UHTES) and conversion is an emerging field of technology that enables much higher energy densities (>1 MWth) and conversion efficiencies than conventional thermal energy storage technologies. Our research group of Solar Energy Institute is currently developing a novel latent heat thermophotovoltaic (LHTPV) battery that utilizes Si-based alloys to store either surplus renewable electricity or concentrated sunlight in the form of latent heat at temperatures close to 1200 ºC and convert it back to electricity on demand. Determining the State of Charge (SoC) of this ultra-high temperature thermal battery is imperative to regulate its real-time operation and optimize its performance. However, using of several sensors within the storage system –as mainly done in low temperature phase change materials (PCMs) to quantify their SoC - becomes costly and challenging for this range of operating conditions. This study presents a numerical method, which is used to get an understanding of the physical processes taking place during the LHTPV operation and capture comprehensive data of time varying flow variables that can be difficult to record during real-time operation. Our results indicate that we can describe the system’s SoC by measuring the time-varying temperature at its sidewalls and the input/output heat flux values, without the need of knowing beforehand the thermophysical properties of the used materials. Based on these variables we can define several indicators that can help us obtain a better understanding of the required physical signals to be measured in order to determine its SoC, during real-time operation.
Copyright (c) 2025 Myrto Zeneli, Alejandro Datas https://creativecommons.org/licenses/by/4.0
Hybridization of Concentrated Solar Power With Wind and PV to Meet the Self-Consumption Requirements
This paper explores the hybridization of Concentrated Solar Power (CSP) plants with wind and photovoltaic (PV) technologies to meet self-consumption demands in two distinct locations: Calama (Chile) and San José del Valle (Spain). We evaluate various hybrid configurations under two primary scenarios: one where excess energy cannot be utilized or fed into the grid, and another where electric heaters are used to transfer excess energy to thermal storage systems. Our findings reveal that hybrid plants significantly reduce the LCOE and increase the Capacity Factor (CF) compared to standalone CSP plants, with optimal configurations varying by location due to differences in climatic conditions. In Calama, wind energy plays a crucial role, whereas in San José del Valle, a combination of PV and wind is more effective. Additionally, the use of electric heaters to store surplus energy enhances system efficiency. This study underscores the viability and efficiency of hybrid CSP plants, especially when adapting to regional climatic and geographic characteristics, providing a compelling case for their implementation in diverse locations.
Copyright (c) 2026 José A. López-Álvarez, Miguel Larrañeta, Sara Moreno-Tejera, J.M. Delgado-Sanchez, Isidoro Lillo-Bravo, Manuel A. Silva-Pérez https://creativecommons.org/licenses/by/4.0
Simulation and Sensitivity Analysis of a Solar Driven Trigeneration System With Thermal Energy Storage
In the joint European project Thermal Energy Storage for On-demand Solar Trigeneration (TES4Trig), an innovative solar driven CCHP (Combined Cycle Heat and Power) system was investigated. The main components of the CCHP system are an Organic Rankine Cycle (ORC) coupled with an Ejector Cooling Cycle (ECC), a solid-state thermal energy storage (TES) syfstem as well as a parabolic trough collector (PTC) field. The system will be demonstrated on-site at the Lavrio Technological and Cultural Park (LTCP) in Attica, Greece [1]. Simulation results of the system for supplying energy to the administrative building of the LTCP are presented. Furthermore, a simulation for a scaled-up system was carried out for a hospital in Heraklion. The results show that the scaled-up system can deliver 10 % of the electricity demand and 39 % of the heat demand with the ORC cycle. The ECC cycle covers 15 % of the cooling requirement. By that, a load factor of 81.4 % over a year is achieved. This can be further optimized by considering other PTC field variables and TES capacities. From an energy perspective, it can be concluded from the results that a TES4Trig system for large electricity, heating and cooling consumers such as a hospital has great potential for the future. It is preferable that the consumer has a continuous energy consumption to maximize system utilization.
Copyright (c) 2026 Spiros Alexopoulos, Zahra Mahdi, Johannes Sattler, Mohamed Elbadawi, Konstantinos Braimakis, Sotirios Karellas, Dimitrios Tziritas, George M. Stavrakakis, Dimitris Bakirtzis, José Bautista, Alejandro Zapata Ballestero, Stefan Bonleitne, Cristiano Teixeira Boura, Ulf Herrmann https://creativecommons.org/licenses/by/4.0
System-Level Assessment of Green Hydrogen Production via SOEC-Solar Thermal Integration
This study investigates the integration of third-generation (Gen3) Concentrated Solar Power (CSP) systems with Solid Oxide Electrolysis Cells (SOEC) for green hydrogen (gH2) production in the Atacama Desert, Chile. A 100 MW CSP plant coupled with SOEC systems of varying capacities is modeled to optimize hydrogen production using thermal storage particles at 780°C. The analysis focuses on the techno-economic performance, highlighting the importance of Thermal Energy Storage (TES) capacity. Results indicate that optimal gH2 production occurs with around 10 hours of TES, beyond which additional storage offers minimal benefits. The findings demonstrate that asymmetrical capacity integration between CSP and SOEC systems is economically advantageous, particularly when maintaining a capacity ratio (CR) between 0.01 and 0.2. This integration can potentially exceed the energy demands of the region’s copper mining industry, contributing to significant reductions in fossil fuel reliance and promoting the commercialization of surplus hydrogen.
Copyright (c) 2026 Ignacio Javier Arias, Felipe G. Battisti, Armando Castillejo-Cuberos, José Alfonso Romero-Ramos, Loreto Valenzuela, Luis Francisco González-Portillo, José Cardemil, Rodrigo Escobar https://creativecommons.org/licenses/by/4.0
A Comparative Analysis Between Ceramic and Metallic Receiver Designs
The outlet temperature targets for Gen 3 Concentrating Solar Power (CSP) systems pose a significant challenge to the structural reliability of high-temperature metallic materials. Advanced ceramics are a promising option due to their high temperature strength and low thermal expansion. However, challenges such as limited ductility and fabrication issues need to be addressed. Before tackling manufacturing challenges, CSP developers must determine the viability of high temperature ceramic components in system design, considering factors like plant operating life. This paper presents a comparative design analysis of tubular external receivers constructed from a high temperature nickel-based superalloy, A740H and a monolithic ceramic material, commercial SiC, using srlife, an open-source receiver evaluation and life prediction tool. Results indicate that A740H receivers can achieve a 30-year service life if the flux is limited to 450 kW/m², which may not be economically viable. In contrast, the Weibull 3-parameter model estimates a service life exceeding 30 years for SiC receivers, even at a much higher flux limit of 1000 kW/m².
Copyright (c) 2025 Bipul Barua, Pawan Chaugule, Mark C. Messner, Dileep Singh https://creativecommons.org/licenses/by/4.0
Design Data for Alloy 282 High Temperature Concentrating Solar Power Components
New design rules for high temperature concentrating solar power metallic components have been proposed recently. These rules are to be used in conjunction with the Section III, Division 5 rules of the ASME Boiler & Pressure Vessel Code and include three design by analysis options. In this paper, we report the corresponding design data for a nickel-based high temperature alloy – Alloy 282. The current Alloy 282 Code Case includes some basic material properties such as Young’s modulus, Poisson’s ratio, thermal properties, yield strength, tensile strength, and allowable stress So. However, a complete design check for high temperature components requires additional material data including allowable stress Sm, isochronous stress-strain curves, minimum-stress-to-rupture, fatigue diagrams, and creep-fatigue damage envelope. We construct these design data from the available material data in the literature and data generated recently at Idaho National Laboratory. We also develop an inelastic constitutive model for use with the design by inelastic analysis method.
Copyright (c) 2025 Bipul Barua, Mark C. Messner, Michael D. McMurtrey https://creativecommons.org/licenses/by/4.0
Investigation on the Injection of Exhaust Air Into Cavity Receivers
Concentrating solar thermal (CST) systems stands out as a promising renewable energy technology, leveraging radiative heat transfer to convert solar irradiance into thermal energy. Central receiver systems (CRS), a form of CST, demonstrate potential for diverse industrial applications due to their ability to operate at high temperatures. However, optimizing their efficiency remains a challenge, particularly regarding the utilization of air as a heat transfer fluid (HTF). This study investigates the impact of exhaust air reinjection on the performance of cavity receiver systems in CST. Previous research has explored similar concepts, but gaps remain in directly modeling exhaust air return, especially in the context of cavity receivers. Using a finite element method (FEM) model this research examines various parameters affecting exhaust air injection, including injection ring height and outlet air flow velocity. Results indicate a dependency between exhaust air reinjection velocity, total mass flow rate, and the air return ratio (ARR). Higher injection velocities, coupled with increased mass flow rates, lead to greater exhaust air loss and lower ARR values. Through parametric analysis, insights are gained into the geometry parameters crucial for optimizing ARR and enhancing receiver efficiency. The highest ARR of greater than 95% is achievable when the air is injected close to the aperture in the radial directions and the fluid velocity is minimized through lower flowrates or increased inlet boundary area. These findings contribute to advancing the understanding and design of cavity receiver systems for improved renewable energy utilization.
Copyright (c) 2025 Koda Boldt, Aidan McConnehey, Todd Otanicar https://creativecommons.org/licenses/by/4.0
Model Sensitivity Analysis of Lifetime Predictions for Generation 3 Particle-sCO2 Heat Exchangers
A sensitivity analysis is performed to determine which variables play a first order role in determining the lifetime of particle-sCO2 heat exchangers. A symmetric half-plate geometry based on a hypothetical 16.7 MW commercial scale particle-sCO2 diffusion bonded IN617 heat exchanger is studied. A reduced-order modelling approach is presented and the steady-state and transient thermal and mechanical performances under nominal Generation 3 concentrated solar power operating conditions are compared against the fully featured model. The defeatured model shows the ability to accurately predict the thermal performance and mechanical lifetime at a fraction of the computational cost, making it a viable option for analysing commercial scale systems. Seven of the model input variables are then parameterized using a Latin Hypercube Sampling method and up to 128 different realizations are simulated. The transient stress results are linearized along stress classification lines in the header ports and used to predict the number of cycles to failure due to fatigue and creep. Sobol indices are generated to relate the cycles to failure to the independent variables studied. The results show that the uncertainty in the creep cycles to rupture data dominates the variation in lifetime predictions.
Copyright (c) 2025 Christopher Bowen, Matthew Sandlin https://creativecommons.org/licenses/by/4.0
CFD Study on a Breadboard Receiver With Inserted Spiral Structures and Sodium as Coolant
In this work CFD studies about tubular CSP (Concentrated Solar Power) receivers with heat fluxes of more than 4 MW/m2 and liquid sodium as heat transfer medium are presented. A significant improvement of heat transfer conditions is achieved by using spiral type ribs at the inner pipe walls. Furthermore, a comparison of receivers made of Inconel 690 and Niob is shown.
Copyright (c) 2025 Michael Böttcher, Joachim Fuchs https://creativecommons.org/licenses/by/4.0
Hedging Risk in Techno-Economic Assessment for CSP Plants Through Synthesis of One-Minute Irradiance Series
For the proper sizing of a solar plant, thorough simulations are performed to obtain the optimum configuration for the optimization objective, such as to minimize the Levelized Cost of Energy. These simulations consider the use of a Typical Meteorological Year, that condenses in a single year the long-term meteorological characteristics. These data sets are often derived from satellite estimates and validated against ground measurements taken over a shorter period of time. One issue with these data sets is concerned with temporal resolution, as they are limited by the capacity of the satellite to resolve phenomena on a temporal scale. This results in a loss of high-frequency detail that could affect the techno-economic design and assessment of a solar plant, creating uncertainty in the expected performance when compared to ground data, thus increasing project risk. This work explores the effect of applying a temporal downscaling technique to generate one-minute estimates of ground radiation from hourly satellite data in the reduction of uncertainty in technical and economic key performance indicators. A Concentrated Solar Power plant of 100MWe and 12 hours of storage is studied and results are compared to determine the extent to which temporal downscaling allows to hedge estimation of performance and in turn, risk. Results show that while the most significant source of uncertainty is the estimation error inherent to the satellite procedure, temporal downscaling allows for a reduction of 2.1% in LCOE estimation, showing that a relatively simple post-processing procedure allows for a measureable reduction in investment risk.
Copyright (c) 2025 Armando Castillejo-Cuberos, Ignacio Arias, José Cardemil, Rodrigo Escobar https://creativecommons.org/licenses/by/4.0
Simulation of a Hybrid Concentrated Solar and Biomass-Fuelled Trigeneration System for Residential Applications
Solar technologies stand out as effective solutions for decarbonising the building sector. Among them, Concentrated Solar Power (CSP) systems offer the advantage of delivering flexible and dispatchable power. However, hybridisation with other renewable energy sources is often pursued to extend the operational hours. Therefore, this study investigates the complementarity of solar energy with biomass combustion within a small-scale hybrid trigenerative plant. More precisely, the proposed system consists of a 240 kWth peak thermal power Linear Fresnel Reflectors solar field combined with a 130 kWth back-up biomass boiler to supply heat to a 20 kWel/100 kWth Organic Rankine Cycle (ORC) unit for the provision of cooling, heating and electric power to 10 apartments. The hybrid plant also integrates thermal energy storage tanks and a battery energy system to increase the solar energy self-consumption and reduce the intervention of the grid. The performance of the hybrid system is analysed through an advanced simulator developed by the authors in MATLAB/Simulink considering the components’ inertia. The results reveal an increment in solar energy self-consumption achieved by exploiting the low solar irradiance to bring the latent heat thermal energy storage into its melting range, thereby extending ORC operation into nighttime hours. More precisely, the system meets the entire annual thermal demand for space heating, cooling and domestic hot water through renewable sources, consuming 2.25 tons of biomass. Electric demand coverage, instead, reaches up to 81% with the inclusion of a 60 kWhel battery energy storage system.
Copyright (c) 2025 Luca Cioccolanti, Greta Lombardi, Luca Del Zotto, Pietro Elia Campana https://creativecommons.org/licenses/by/4.0
Techno-Economic Study of a Hybrid CSP-CPV Plant in Tower Configuration
Despite being a mature technology, CSP plants with thermal energy storage (TES) are unable to achieve the levelized cost of electricity (LCOE) values of commerical PV plants. The high costs of the tower, heliostat field, and thermal energy storage (TES), among other factors, hinders the achievement of such values. In this study, we present a multi-tower plant with two solar concentration technologies: each tower features a cavity thermal receiver (coupled to a molten salt TES and a power block) and a concentrated photovoltaic (CPV) receiver. The shared investment costs of the solar field and the tower may allow to obtain more competitive economic indicators. This study goals to analyze the techno-economic feasibility of the hybrid solution by evaluating the LCOE and the Cost of Valued Energy (COVE) of different system configurations (e.g. 4, 8 and 12 h of TES). Optimal system configurations reach a LCOE and a COVE of 56.8 €/MWh and 61.9 €/MWh, respectively. Highly favorable results compared to the values obtained for a conventional tower CSP plant with molten salts TES: 106.05 €/MWh, and 90.27 €/MWh. In conclusion, the present study proves the tecno-economic viability of a multi-tower plant hybridizing two solar concentrating technologies: thermal and concentrated photovoltaics.
Copyright (c) 2025 Alicia Crespo, Marta Murkowska, Maitane Ferreres, Anders N. Andersen, Gregor Bern, Diego Caro, Desideri Regany, Joan I. Rosell, Jerome Barrau https://creativecommons.org/licenses/by/4.0
A Hybrid CSP-PV System for Sustainable Energy in a Chilean Mine: A Case Analysis
Chile, a global leader in copper production, faces increasing energy demands in its mining sector, particularly in the northern regions, where the country’s major mining operations are located alongside its vast solar potential. Reliable and continuous power supply is critical for these operations. In alignment with the country’s ambitious target to decarbonize its energy sector by 2050, innovative renewable energy solutions are required. This study examines the design and feasibility of a hybrid Concentrated Solar Power (CSP) and photovoltaic (PV) system, intended to deliver 150 MW of base-load electricity to a mining operation near La Serena, Chile. The proposed system integrates a parabolic trough CSP plant with molten salt thermal storage and a bifacial PV array equipped with 1-axis tracking. A custom simulation model based on PySAM is used to assess the technical and economic performance of the hybrid system, focusing on the use of HELISOL XLP® as the heat transfer fluid in the CSP component. The results demonstrate that the hybrid system achieves a 70% capacity factor and a levelized cost of energy (LCOE) of 84.39 USD/MWh, outperforming standalone CSP plants. Furthermore, the hybrid configuration enhances energy dispatch efficiency and reduces the overall LCOE, positioning it as a competitive solution for meeting industrial energy demands in Chile. The findings underscore the potential of hybrid CSP-PV systems to significantly lower energy costs while ensuring a stable power supply. This study contributes to Chile's renewable energy transition and provides valuable insights into the role of hybrid systems in supporting the decarbonization of energy-intensive industries, offering a scalable model for global applications and for further optimization and cost reduction of this kind of energy supply.
Copyright (c) 2025 Frank Dinter, Juan Manuel Gonzalez, Carlos Felbol, Francisco Moraga https://creativecommons.org/licenses/by/4.0
Optimal Design of Hybrid Solar Power Systems: A Case Study in the Chinese Market
The global energy industry is shifting towards a net-zero energy system to achieve climate neutrality, leading to significant growth in distributed renewable energy generation. This reshapes market dynamics and presents challenges in balancing supply and demand, increasing the risk of midday oversupply and variability in renewable generation, potentially compromising grid reliability. Concentrated solar power (CSP) offers a viable solution for grid decarbonization by integrating large-scale renewables and providing ancillary services like peak shaving and load shifting, frequency control, and energy storage, complementing the intermittent supply of photovoltaics (PV). The synergy between low-cost PV and dispatchable CSP fosters a resilient and sustainable system. Demonstration projects, especially in China, emphasize the relevance of hybrid CSP systems. CSP plants are built alongside large-scale PV installations to address the growing challenges associated with the electrical grid. The study explores hybridizing high-performance collectors, specifically Ultimate Trough (UT) collectors using molten salt as a heat transfer fluid, with PV to identify optimal solar field sizing and operational strategies. The techno-economic optimization framework integrates in-house cost models with thermodynamic and optical models derived from the System Advisor Model (SAM). A case study in Shichengzi, China, evaluates a hybrid CSP + PV plant with integrated thermal storage. High-performance collectors and better synergy in UT and PV production profiles lead to a 17% and 35% reduction in the power purchase agreement (PPA) price compared to conventional large aperture troughs not optimized for molten salt operation and linear Fresnel devices. This research supports informed decision-making and design solutions for sustainable and economically viable renewable energy production.
Copyright (c) 2025 Gabriele Furlan, Axel Schweitzer, Fabian Gross, Alf Oschatz https://creativecommons.org/licenses/by/4.0
Comparative Techno-Economic Analysis of Different Parabolic Trough CSP Plants for the Italian Market
The objective of this study is to present updated estimates of the cost of concentrated solar power (CSP) projects that are relevant for the current Italian market. To this end, a comparative techno-economic analysis of different CSP plant types based on parabolic trough (PT) collectors was conducted, considering various scenarios with respect to heat transfer fluids, location and storage size. The scenarios were defined in accordance with a number of requirements, including the utilization of technologies produced in Europe (in alignment with the EU's Net-Zero Industry Act), the availability of performance and cost data from existing literature, and/or the authors' own experience, as well as the eligibility for incentives according to the initial drafts of the new support measure. The analysis employed two distinct modelling tools, developed by ENEA and DLR, respectively. These offered varying levels of detail in the description of the plant behavior. Thus, cross-checking of the results was enabled. Additionally, insights were gained concerning the impact of the chosen modelling approach on performance assessment.
Copyright (c) 2025 Walter Gaggioli, Marco D'Auria, Valeria Russo, Simona De Iuliis, Luca Turchetti, Jürgen Dersch, Michael Wittmann, Tobias Hirsch, Jana Stengler https://creativecommons.org/licenses/by/4.0
Techno-Economic Analysis on Optimum Size of a Heliostat for High-Temperature Applications
This study investigates the impact of heliostat size on the levelized cost of heat (LCOH) and explores the trade-off between performance and cost for a baseline 160 MWth concentrating solar thermal (CST) tower system at high temperatures (565°C – 1550°C). The analysis assumes blackbody radiation for thermal losses at the receiver and employs ray tracing to assess optical losses in the heliostat field. A surrogate cost model is used to break down component costs for a specific commercial heliostat design (i.e., SunRing), considering volume production and operations and maintenance (O&M) costs to determine installation costs. The results indicate that heliostat size significantly affects the LCOH at different temperatures, with installation costs being a crucial factor in determining the optimal heliostat size. These installation costs vary by temperature and plant size due to power requirements and volume production considerations. The results motivate ongoing research to further refine the cost model and explore the projects of different sizes.
Copyright (c) 2025 Ahmed Gamil, Alexander Zolan, Chad Augustine, Guangdong Zhu, Kenneth Armijo https://creativecommons.org/licenses/by/4.0
Design and Optimisation of a Modular PV-CSP Hybrid Plant
This study investigates the design and optimisation of a hybrid plant comprising an array of 30 MWac PV-CSP modules. Each module integrates a PV system, a power tower CSP with thermal energy storage, and a gas-fired generator for backup power. This configuration aims to leverage the benefits of both PV and CSP technologies while addressing the challenges associated with large-scale CSP systems, such as high upfront costs and lengthy construction periods. A Python-based application was developed to optimise and simulate a modular PV-CSP hybrid plant. This application integrates existing software with custom computational and financial models to generate performance and economic metrics. These metrics were used to compare a single 120 MWac plant with a modular plant comprising 4 x 30 MWac modules that are constructed sequentially. The large-scale plant demonstrates better economic performance across all investigated metrics. The modular layout enables earlier revenue generation; however, it has a higher total installation cost than the large-scale plant. These findings highlight the possible economic advantages of constructing single large-scale systems rather than integrating several small-scale systems.
Copyright (c) 2025 Benjamin Gardiner, Stephen Clark, Craig McGregor https://creativecommons.org/licenses/by/4.0
Application of Molten Salt Electrical Heaters to Increase the Flexibility of CSP Plants’ Power Block
The transforming grid profiles require concentrated solar power (CSP) plants to operate in a dispatchable and flexible manner; however, the allowable minimum load of the power block exerts a limitation on the operation range. This study proposes using molten salt electrical heaters to lower the minimum electricity output of CSP plants. In this regard, three configurations of the molten salt electrical heaters, 1) in parallel to the receiver, 2) in parallel to the hot tank, and 3) in series to the receiver, are investigated with six grid and three revenue scenarios. The system is assessed for Fuerteventura. The findings validate that the application of the molten salt electrical heaters, particularly through Configurations 1 and 3, enhances a) the flexibility characteristics of the CSP plant with up to a 10.2% increase in demand coverage factor, an 84.6% decrease in start-up instances, and a 41.4% increase in operating hours; and b) economic performance with up to a 35.7% increase in gross profit.
Copyright (c) 2025 Eylül Gedik, Johannes Werner, Manfred Wirsum https://creativecommons.org/licenses/by/4.0
Hydrogen Production by Means of Small-Scale Multi-Tower CSP Plants Based on sCO2 Power Cycles and Solid Oxide Electrolysers
Concentrated Solar Power can play a relevant role in the decarbonization of the energy sector as it can integrate cost-competitive Thermal Energy Storage, allowing for dispatchable electricity generation. Furthermore, there has been a notable increase in hydrogen demand over the past decade, with most of it being produced using fossil fuels, entailing a large contribution in CO₂ emissions. In this context, the Italian Research Project of National Relevance MUSIC aims to demonstrate the potential of small-scale multi-tower concentrated solar power plants with sodium as heat transfer fluid that are thermally and electrically integrated with a solid oxide electrolyzer to produce green hydrogen and electricity. The objective of this study is to evaluate the performance of a 2 MWel plant for hydrogen production located in Sicily, Italy, by means of numerical models specifically developed to accurately simulate the plant components. A parametric analysis on the number of modules has been carried out and the results show that plants characterized by a smaller field achieve higher optical efficiencies and a lower auxiliary consumption of the HTF pump, at the expenses of lower receiver and piping thermal efficiencies. A maximum yearly solar to hydrogen efficiency of 16.6% was achieved, which largely exceeds the one of conventional PV + PEM systems, proving the potential of the technology.
Copyright (c) 2026 Simone Girelli, Marco Ficili, Dario Alfani, Paolo Colbertaldo, Ettore Morosini, Giancarlo Gentile, Marco Astolfi, Marco Binotti, Paolo Silva https://creativecommons.org/licenses/by/4.0
Characterisation of the Wind Convection Losses in Plain and Ribbed Tubes of Solar Central Receivers via Tube-Resolved CFD Simulations
Convective losses due to wind affect the thermal efficiency of external central receivers of solar power towers (SPT), but their full characterization is still an unresolved question. Furthermore, detailed assessment of these convective losses in new designs, such ribbed tube central receivers, is nearly inexistent. The aim of this study is (a) to parameterize the wind convection coefficient and its local distribution in all the tubes and panels of an external central receiver, and (b) to compare the wind convection coefficients in conventional plain tube receivers and in ribbed tubes receivers designed to enhance heat transfer from the tube wall to the heat transfer fluid (HTF). To gain a detailed understanding of the complex heat transfer phenomena involved, this work is entirely developed through Computational Fluid Dynamics (CFD) simulations in a three-dimensional (3D) domain that describes all the absorber tubes in the receiver. Overall results of the simulations are practically validated against experimental results available in the literature [1].
Copyright (c) 2025 Jose Martín-Martínez, Rafael Pérez-Álvarez, Diego Manuel Martínez-Plaza, Antonio Acosta-Iborra https://creativecommons.org/licenses/by/4.0
Linear Fresnel Ray Tracing Analysis: Southern Italy Plant Optimization Through FresnelSim Algorithm
The goal of maximizing the optical efficiency of a Linear Fresnel Collector is typically addressed through Monte Carlo Ray Tracing simulations. This study introduces FresnelSim, a 3D ray tracing software developed at the University of Genoa, Italy, for the optical analysis of Linear Fresnel Collectors. FresnelSim has been herein used to examine key geometric factors and their impact on a reference plant's producibility, allowing to almost triple the irradiance at the secondary concentrator with respect to a reference base configuration. Through a series of fast parametric simulations, an optimized geometry for such a system is proposed, highlighting to which extent different efficiency indicators are dependent on mirrors’ gap, field length and mirrors’ radius of curvature. Then, an assessment of the effect of the plant’s azimuthal orientation in the range from 0° to 45° is presented, showing that the site’s yearly average producibility is reduced up to 3.3% as an effect of primary mirror alignment. Finally, an analysis of the Compound Parabolic Collector is presented in terms of sub hourly opto-energy efficiency for 3 reference days, resulting in values ranging from 80.9% to 87.4%. Energy flux circumferential uniformity at the absorber tube is evaluated under 6 different incidence angles, highlighting that irradiance uniformity could be further enhanced by a properly defined mirrors’ motion law.
Copyright (c) 2025 Samuele Memme, Marco Fossa https://creativecommons.org/licenses/by/4.0
Multi-Flow Falling Particle Receiver Modeling
Generation 3 Concentrating Solar Power systems use solid particles for heat transfer and thermal energy storage. Particle-based systems use a falling particle receiver with an open cavity where particles flow together as a curtain that is directly exposed to solar radiation absorbed by the particles as they descend. The efficiency of the receiver depends on curtain opacity (influenced by the particle mass flow rate), the average particle temperature, and environmental factors. We present a free-falling particle receiver design that incorporates ten individually controlled valves for precise particle supply management. Each valve is equipped with a slide gate and an actuator, ensuring a consistent mass flow rate. In a uniform mass flow rate curtain, the hottest particles accumulate in the center due to non-uniform flux distribution, leading to higher radiative and advective losses. Accordingly, lower flux levels at the periphery result in lower temperature particles. Our modular valve design enhances receiver efficiency by improving curtain opacity in key areas. The outer valves have the lowest mass flow rate, while the center valves have the highest, allowing more uniform heating. The 10-section model outperforms the 1D model by reaching a maximum efficiency of 85%, compared to 84%.
Copyright (c) 2025 Ahmed Mohamed, Gowtham Mohan, Peter Vorobieff, Nathan Schroeder https://creativecommons.org/licenses/by/4.0
Assessment of Self-Dispatch Strategy in a Concentrating Solar Power System: Impact Analysis on the Chilean Spot Electricity Market
This study investigates the technical and economic impacts of self-dispatch strategies on Concentrated Solar Power (CSP) plants in Chile’s spot electricity market. The PySAM simulation tool was used to model three dispatch scenarios—Marginal Cost-Responsive Dispatch, Daytime Mandated Dispatch, and Continuous Base Load Dispatch—to assess their effects on energy production, load factors, and financial outcomes at the Crucero and Cardones substations. The findings indicate that the Marginal Cost-Responsive Dispatch strategy optimizes revenue by aligning energy generation with periods of higher market prices. This strategy mitigates the adverse financial impacts of zero-marginal-cost periods, which undermine the viability of more rigid approaches like Daytime Mandated Dispatch. Economic analysis shows that only the Marginal Cost-Responsive Dispatch consistently covers annualized capital expenditures (CAPEX), particularly at lower CAPEX levels. In contrast, the alternative scenarios fail to achieve financial sustainability due to forced generation during low-value periods. Consequently, these results underscore the crucial role of dispatch flexibility in enhancing the economic performance of CSP plants. The study suggests that market regulations should be revised to encourage strategies that enable CSP plants to dynamically respond to market conditions, supporting the broader integration of CSP technology into Chile’s energy market. Such adjustments are crucial for advancing the country’s decarbonization goals. Future research should focus on further developing advanced self-dispatch algorithms and hybrid CSP systems to optimize economic outcomes in increasingly dynamic market environments.
Copyright (c) 2025 Francisco Moraga, Carlos Felbol, Maria Teresa Cerda, Frank Dinter https://creativecommons.org/licenses/by/4.0
Modeling Thermochemical Energy Storage in a Solar Power Tower Plant: Dynamic Simulation
This work presents a dynamic model of a novel Concentrated Solar Power plant that integrates Thermochemical Energy Storage with Calcium-Looping and a supercritical CO2 Brayton power block. The aim is to provide a simulation tool to assess annual plant performance under realistic solar conditions. The model was developed using the Modelica language and simulated with OpenModelica. The configuration includes a heliostat field with a Solar Multiple of 1.8, 4 hours of TCES storage, and a 100 MWe sCO2 Brayton cycle. The system effectively manages energy generation and storage through advanced control strategies, including defocusing to prevent overcharging and efficient handling of startup and shutdown phases. A parametric analysis was conducted to identify the optimal configuration, considering SM and storage hours variations. The results indicate that the highest plant efficiency and an LCOE below 110 USD/MWh are achieved with a solar multiple of approximately 2.6 and storage capacities exceeding 16 hours, aligning with ranges considered commercially viable for CSP technologies. However, the system exhibits higher radiation losses at the receiver due to the elevated reaction temperature. Despite this, the study demonstrates the energetic viability of the integrated CSP-TCES system. The findings highlight the potential of the proposed system, although ongoing efforts are aimed at further enhancing the model’s accuracy.
Copyright (c) 2025 Freddy Nieto, Alberto de la Calle, Rodrigo Escobar https://creativecommons.org/licenses/by/4.0
Energy Utilization Factor of Solar Tower Systems
The solar tower system is one of the most promising concentrated solar power technologies that can address climate change issues by meeting energy demand sustainably while mitigating carbon emissions. The mirrors of the solar tower require a large share of the investment cost and occupy 4-8 times the ground compared to the mirror surface area. The share of the plant area cost may become significantly high for regions where the land is not cheap, especially in developing countries. In this study, a parameter named Energy Utilization Factor is introduced to quantify the utilization of the ground area in terms of available solar radiation energy. The variation of the Energy Utilization Factor is studied for a range of design variables without considering any specific dimensions for the heliostat and the receiver. The annual Energy Utilization Factor is seen to have a maximum value within 15 %, indicating the solar tower system is only capable of using one-seventh of the available solar resource on the ground. The maximum achievable Energy Utilization Factor is seen to increase with the tower height, but reduces with latitude. For a given heliostat field, the Energy Utilization Factor is seen to have a direct relationship with the amount of mirror area employed per unit ground area.
Copyright (c) 2025 Indranil Paul, Shireesh Kedare https://creativecommons.org/licenses/by/4.0
Design and Operation of Hybrid CSP-PV-Wind Plants Operating on the Italian Day-Ahead Electricity Market and on the Ancillary Services Market
Concentrating Solar Power equipped with Thermal Energy Storage (TES) allows for dispatchable power production, but the worldwide installed power is still limited due to its higher investment costs with respect to other renewable technologies. A promising option to reduce costs, while keeping a high dispatchability level, is the hybridization of CSP with Photovoltaic (PV) and wind turbine (WT) plants. Hybrid CSP-PV-Wind plants have already shown their capability to achieve higher dispatchability level and lower costs with respect to stand-alone CSP, PV and wind plants. This work investigates the techno-economic optimization of hybrid CSP-PV-Wind plants capable of operating on both the Day Ahead Market (DAM) and the Ancillary Services Market (ASM), assuming different market scenarios. The design and operation of the hybrid plant are co-optimized using the optimization framework developed by Politecnico di Milano and considering the simultaneous participation of such plant to the DAM and ASM Italian markets. Results showed that while a price multiplier of 4 should be applied to the current spot market prices to make the hybrid plant economically viable in the DAM market, a price multiplier of 2 is sufficient for a positive NPV when also the revenues from the ASM market are considered. Moreover, the CSP turn out to be an essential flexibility provider: conversely to the solution combining PV and WT with a battery storage, CSP-based configurations avoid the need for a large battery for the reserve provision, with a significant economic benefit on the plant NPV.
Copyright (c) 2025 Lorenzo Pilotti, Giampaolo Manzolini, Walter Gaggioli, Antonio Guglielmo, Emanuele Martelli, Marco Binotti https://creativecommons.org/licenses/by/4.0
Utilization of Spillage in Solar Particle Power Plants With Concentrating Photovoltaics
Concentrating solar power plants are considered an important contributor to renewable energy supply due to their high efficiency and cost-effective storage. Solar tower systems using solid particles as a heat transfer and storage medium, in combination with concentrating photovoltaics (CPV), promise to reduce the levelized cost of energy. This study evaluates the cost potential from hybridizing solar power plants with CPV modules integrated into the radiation shield of a particle receiver, to capture spillage radiation that is otherwise lost. Simulation results for a commercial configuration case show that the annual electricity production could be increased by up to 12%, with levelized cost of electricity from the CPV part ranging from 0.02 to 0.024 €/kWh. The electric components of the CPV subsystem have by far the highest single component cost contribution, the cooling water loop adds a minor contribution. Further improvement options exist and are discussed briefly. A demonstration test in a real receiver application is currently under preparation in DLR’s solar tower test facility. Six CPV modules will be integrated into the radiation shield of a particle receiver. Solar testing will validate the performance and also provide information about potential dust contamination problems.
Copyright (c) 2026 Reiner Buck, Jens Rheinländer, Werner Bensch, Markus Stetka https://creativecommons.org/licenses/by/4.0
Techno-Economic Assessment of Solar Hybrid System With High-Temperature Heat Pump for Industrial Heat Generation
Solar thermal collectors, high-temperature heat pumps and thermal energy storage are key technologies for industrial decarbonization. The development and installation of these technologies represent a double benefit. First, by using renewable energy sources, it contributes to reducing fossil fuel consumption. Second, their integration can supply heat for industrial processes where other single renewable-based technologies, such as solar, can encounter limitations. This work presents the techno-economic assessment of a solar hybrid system using pressurized water as heat transfer fluid. The system is studied in the Greek electricity market considering prices of 2022. Dispatch strategies and system sizing are identified for optimal techno-economic performance. The main performance indicators investigated are the levelized cost of heat, the operational expenditure, and savings compared to traditional fossil-fuel solutions. The results highlight that the levelized cost of heat is as low as 98 €/MWh with operational cost savings of 23k €/y against traditional non-flexible gas boilers.
Copyright (c) 2025 Mateo Sanclemente Lozano, Silvia Trevisan, Rafael Guedez https://creativecommons.org/licenses/by/4.0
Optical Design and Analysis of a Solar Crucible
A solar crucible was optically designed to be coupled with a Fresnel lens: it is a small size concentrator commercially available. To study the thermal aspects of the system, simple experiments were performed on field, and the results were utilized to set-up a model. Finally, the designed crucible was analyzed using the developed model in order to evaluate the shape of the crucible and its behavior under vacuum or in a protected atmosphere without oxygen.
Copyright (c) 2025 Paola Sansoni, Daniela Fontani, Franco Francini, Maurizio De Lucia , Emanuele Giusti, David Jafrancesco https://creativecommons.org/licenses/by/4.0
Introducing FIVER: An Open-Source Tool to Simulate Heat Transfer in Participating Media and Arbitrary Geometries
Decarbonization of industrial processes operating at above 1000 °C is a major challenge. A promising answer lies in concentrating solar thermal technologies, but current receivers operate at about 600 °C only. New concepts are needed to achieve the target temperatures with good efficiencies, thus enabling commercial deployments. Further advances require that researchers have access to simulation tools treating heat transfer problems in radiatively participating media accurately, which is seldom the case today. Here we present a first effort to bridge this gap, introducing FIVER (FInite VolumE Ray tracer), an open-source Matlab tool for solving transient radiative-conductive heat transfer problems in participating media with spectral properties and complex geometries. FIVER tackles the challenging simulations needed to design the solar receivers of the future, and we hope it will become a valuable tool for researchers investigating concentrating solar thermal receivers and other technologies needed to decarbonize high temperature processes.
Copyright (c) 2025 Charles Wetaski, Sebastian Sas-Brunser, Emiliano Casati https://creativecommons.org/licenses/by/4.0
Techno-Economic Analysis of a Solar Calciner for CO2 Emissions Reduction in the Chilean Cement Industry
Clinker, constituting approximately 72% of cement's composition, is produced through an energy-intensive process that significantly contributes to CO2 emissions. This study explores the integration of a solar calciner into the Chilean cement industry, particularly in the Antofagasta region, which is characterized by high solar energy irradiation, with an annual DNI of 3,250 kWh/m2. This region also accounts for approximately 30% of the country's cement sector energy consumption. In this context, this study evaluates two Concentrated Solar Thermal (CST) scenarios: the Top of Tower (TT) system and the Beam-down (BD) system, assessing their technical and economic feasibility for reducing CO2 emissions in the calcination process. The findings suggest that both CST systems could substantially reduce CO2 emissions in the calciner. However, economic feasibility remains a challenge, primarily due to the low cost of coal, which is the main fuel in the Chilean cement industry. Additionally, the efficiency of the solar calciner is found to be crucial for achieving maximum emission reductions, for the scalability of the technology, and for its future adoption in Chile's cement industry. Although the Levelized Cost of Heat (LCOH) for the proposed plants is currently higher than the coal-fired calciners in which is produced about 90% of current clinker production in Chile, potential reductions in heliostat costs, coupled with an increase in carbon taxes beyond the current value of 5 USD/tCO2, could significantly improve the economic viability of CST plants in Chile's cement industry.
Copyright (c) 2025 Juan Sebastian Zuleta Marin, Gregor Bern, Frank Dinter, Werner Platzer https://creativecommons.org/licenses/by/4.0
Advanced Microchannel Radial Receivers for the Economic Feasibility of Solar Thermal Power Plants
A key aspect for the development of solar thermal technology is to improve cost-competitiveness without compromising efficiency. One of the more expensive items in a solar thermal power plant is the heliostat field, which accounts for 40-50% of the total plant investment. One way to decrease this cost is to reduce the size of the field by improving the efficiency in the thermal exploitation of this concentrated solar radiation. This work presents a novel radial solar receiver design based on compact structures, which allows solar radiation to be absorbed more efficiently by reducing the absorber area and shaping a macroscopic sun trap geometry to reduce heat losses. These compact structures are specially designed to work with pressurised gases, so their coupling to supercritical CO2 power cycles is straightforward. Specifically, the direct coupling to a novel sCO2 cycle is considered, where the heat is supplied in the low-pressure line of the cycle and the CO2 is compressed at low temperature, which reduces the auxiliary consumption, increasing the net efficiency. The advantages of the microchannel radial receiver have been highlighted by a thermo-economic comparison between this receiver and a conventional external receiver, resulting in a significantly lower total plant investment (171 Mio.$ vs. 195 Mio.$). This difference is due to the smaller heliostat field required, due to the improved thermal performance of the novel receiver design compared to the more conventional one.
Copyright (c) 2026 María José Montes, José Ignacio Linares, David D'Souza, Mercedes Ibarra, Eva Arenas, Alexis Cantizano, Marta Muñoz, Rubén Barbero, Antonio Rovira https://creativecommons.org/licenses/by/4.0
Spillage Recovery Devices for High Temperature Air-Based Solar Thermal Receivers
This paper presents the development and implementation of a novel approach to spillage recovery devices (SRDs) for high-temperature air-based solar thermal receivers by Odqa Renewable Energy Technologies Ltd. As concentrated solar thermal systems push towards higher operating temperatures to improve efficiency, spillage becomes a significant technical challenge, increasing both in flux and overall fraction of the incident power. Odqa’s air-based receiver design however, leverages heat recovery and regeneration, allowing spillage to be repurposed rather than wasted. This paper investigates the impact of SRDs on some key CST parameters such as aperture size. The first section explores the sensitivity of receiver performance to SRD integration, while the second details Odqa’s approach to developing such a system for a 100kW receiver prototype. The optimized SRD design, tailored to distinct operational conditions, demonstrates the feasibility of such an approach and their potential use as mechanism to increase the overall performance of CST systems cost.
Copyright (c) 2026 Augustin Wambersie, Mark Loasby , MyeongGeun Choi , Pok-Wang Kwan , Peter T. Ireland , Chiang Churchill Ngai , Joe Baddeley , Katarina Marčeta, Orla Mallon , Aslı Kaya , Dave Mountain , Scott Battams , Ashley Cooper , George Wilson , Kirk Ashley-Morgan , Gediz Karaca https://creativecommons.org/licenses/by/4.0
CFD Investigation of Particle Temperature in Fluidised Bed Solar Receivers
This study investigates the influence of fluidised bed solar receiver geometries and fluidisation velocity on particle temperature distribution and bed performance, with a focus on evaluating the feasibility of using a square shape for fluidised bed solar receivers. The research compares cylindrical and square bed geometries under varying fluidisation velocities to assess their impact on temperature profiles, and overall receiver performance. The results indicate that increasing fluidisation velocity enhances particle mixing and raises mean particle temperatures across both geometries, with the cylindrical bed showing higher mean temperatures at higher velocity. However, the square bed maintains better temperature uniformity, especially at higher velocity, which is advantageous for minimising hot spots and ensuring stable operation. While increased velocities improve bed dynamics and facilitate rapid collection of intermittent solar power, they also require higher pumping power and can lead to greater heat loss. Despite these benefits, further investigation is needed on the square shape, particularly in exploring uneven fluidisation regimes to reduce higher temperatures at the corners. Overall, the findings suggest that square-shaped fluidised beds offer a promising and feasible design alternative for solar receivers, balancing temperature uniformity and operational efficiency.
Copyright (c) 2025 Mustafa Alqudah, Tim Anderson, Alan Brent https://creativecommons.org/licenses/by/4.0
3D-Printed Solar Cavity Receiver for Heating Pressurized Air – A Preliminary Evaluation
High-temperature solar receivers experience non-uniform solar flux, which induces thermal stress in the receiver tubes. This stress is more pronounced in gas solar receivers due to the lower thermal conductivity of gases. To address these limitations, this paper introduces a novel 3D-printed solar receiver featuring a conical cavity and a honeycomb lattice structure. The design integrates a double helix heat exchanger with a tear-drop cross section to reduce thermal stress, enhance optical performance. Manufactured using Direct Metal Printing (DMP) with Nickel superalloy Inconel 718, the receiver is designed for high-temperature and high-pressure applications. Simulation results, conducted using Ansys-Fluent and an in-house code, demonstrate the temperature distribution, pressure drop, and outlet temperature variations as a function of heat flux and air mass flow rate. The findings indicate that the receiver can operate under a maximum heat flux density of 230 kW/m², corresponding to the maximum working temperature of Inconel 718 (1000°C), with minimal pressure drop, making it a promising solution for mitigating thermal stress in solar receivers.
Copyright (c) 2025 Ahmed Muhammad Azmeer, Omar Behar, Bassam Dally https://creativecommons.org/licenses/by/4.0
Development of a Small Punch Test to Evaluate Liquid Metal Embrittlement Susceptibility of 316L Stainless Steel in Liquid Sodium
Liquid sodium is proposed as a heat transfer fluid for solar thermal power receiver designs. It has a long history of use for heat transfer in various industries, with extensive knowledge of its impact on the structural integrity of materials at temperatures ranging from 300 ℃ to 800 ℃. However, the effects at lower temperatures are more poorly understood, which is crucial to studying solar thermal power plant systems. These systems experience diurnal cyclic temperature variation, which causes significant fluctuations in the operating temperature of liquid sodium. Several studies have demonstrated that the susceptibility of metals to Liquid Metal Embrittlement (LME) is highest at temperatures close to the melting point of the liquid metal. Therefore, this study investigates the susceptibility of 316L stainless steel, a common construction material, to sodium induced LME at temperatures between 100 ℃ to 300 ℃ using the Small Punch Test (SPT) method. The test apparatus was validated by using a known embrittling pair of Brass-Galinstan between 10 ℃ to 43 ℃, where the test revealed the expected LME susceptibility of brass. However, no evidence of LME was found in the 316L-sodium pair at temperatures up to 300 ℃.
Copyright (c) 2025 Stuart Bell, Gaurav Vithalani, Richard Clegg, Geoffrey Will, Theodore Steinberg, Rezwanul Haque https://creativecommons.org/licenses/by/4.0
CFD Study of a Sodium High-Flux Receiver Designed for Additive Manufacturing
It has been demonstrated that heat fluxes greater than 4 MW/m2 can occur at high-flux concentrated solar power (CSP) receivers. In the present paper, a receiver design for additive manufacturing processing is proposed using sodium as heat transfer medium. The proposed design incorporates helical structures within the ducts, which facilitate the swirling motion of the sodium and promote the transportation of the colder coolant towards the heated wall. The objective of this configuration is twofold: first, to enhance heat transfer, and second, to mitigate local overheating at the liquid-solid interface of the receiver. The effectiveness of design variations is substantiated by CFD (Computational Fluid Dynamics) investigations.
Copyright (c) 2026 Joachim Fuchs, Alexandru Onea, Michael Böttcher https://creativecommons.org/licenses/by/4.0
Numerical Prediction of the Initial Heating of Granular Material Treatment Using a Solar Rotary Kiln
Recent studies have proposed rotary kilns as solar receivers or reactors for industrial applications and for thermal storage. However, few investigations have focused on the temperature distribution within the particle bed, which is crucial for understanding system performance and developing optimization strategies. This work presents a comprehensive study of a lab-scale rotary kiln coupled with a high-flux solar simulator, examining the initial seconds of heating inert alumina spheres. Experimental data are compared and integrated with a two-dimensional thermo-fluid dynamic model using an Eulerian continuum approach. The model was initially validated for static particle heating and subsequently applied to simulate a rotating case, predicting temperature distribution in the transversal section of the granular bed. The results demonstrate the significant impact of rotation on homogenizing bed temperature and reducing thermal gradients. When the bed core reaches approximately 180°C, the maximum temperature difference between the center and sides is less than 50°C for the rotating configuration, compared to over 110°C for the static setup. This study provides valuable insights into the thermal behavior of rotary kilns as solar receivers, contributing to the optimization of their design and operation for various industrial and energy storage applications.
Copyright (c) 2025 Alessandro Gallo, Elisa Alonso Romero, María Isabel Roldán Serrano https://creativecommons.org/licenses/by/4.0
Performance Improvement of Parabolic Trough Collector With Thermal Oil-Based Metal-Oxide Nanofluids
In this study, the effects of using thermal oil-based nanofluids on the parabolic trough collector (PTC) thermal performance are examined. A methodology is developed to predict the thermophysical properties of several combinations of thermal oils and nanoparticles. Specifically, Syltherm 800 and Therminol VP-1 are selected as they are common heat transfer fluids (HTF) to be combined with Al2O3 and CuO nanoparticles. The nanoparticle dispersion volume fractions (φ) are varied from 0.0% to 3.0% with increments of 0.25%. Additionally, it has been performed a parametric case study for a PTC plant, located in Rome to further emphasize the potential effects of using nanofluids in bulk-scale CST systems. The addition of nanoparticles to thermal oils used as HTFs in PTC systems results in a non-linear increase in both dynamic viscosity and thermal conductivity, leading to increased pumping power requirements and a moderate increase in thermal performance. The capacity factor and annual thermal energy are improved within the margins of 1.5% and 4%, respectively; however, these gains were offset by a significant rise in electricity consumption, especially for Therminol VP-1 based nanofluids due to plateau in thermal conductivity and nonlinear rise in dynamic viscosity against increasing volume fraction of nanoparticles. Unlike Therminol VP-1, the addition of nanoparticles has led to enhance the thermophysical properties of Syltherm 800 in the operational temperature range which led to an increase the annual thermal energy and capacity factor experiencing nonlinear increases in both thermal conductivity and dynamic viscosity.
Copyright (c) 2025 Levent Güner, Onur Taylan , A. Alperen Günay https://creativecommons.org/licenses/by/4.0
Optimizing Solar Thermal and Electrical Output Through a Hybrid Fresnel Lens and TEG System
This study demonstrates the successful integration of a Fresnel lens into a hybrid solar cooking and thermoelectric generation system, providing both thermal energy for cooking and electrical power generation. The study analyzed various tank designs to enhance heat transfer, improve heat distribution, and optimize the cooking surface. The best-performing design, featuring an aluminium heat sink with fins, achieved the highest fluid temperature of 54.44°C, with superior heat transfer efficiency and uniform distribution. Other designs using stainless steel and copper showed promise but faced challenges, such as uneven heat spread and inefficient baffle configurations. The findings underscore the critical role of material selection and design optimization in enhancing the thermal performance of hybrid solar systems.
Copyright (c) 2025 Khalifa Aliyu Ibrahim, Zaharaddeen Ali Hussaini, Fergus Crawley, Mounia Karim, Zhenhua Luo, Abdullah Ayed Alrwili, Christopher Sansom, Jonathan Siviter https://creativecommons.org/licenses/by/4.0
Experimental and Numerical Study of the Thermal Behavior of Clips in Concentrated Solar Tower Receivers
In this study, we investigated the thermal behaviour of a guiding support, referred to as a clip, for a tube resembling those used in solar central receivers. The focus is on the clip's heating process, which occurs when molten salt begins to flow inside the receiver tube. This work involves both experimental measurements and numerical simulations of the clip, which can be considered as a fin attached to the tube. Experimentally, we measured the temperature profile of the clip over time and observed that, despite the characteristic decaying exponential shape of the clip, the heat transfer can be approximated as one-dimensional. Moreover, numerical simulations were performed to gain a better understanding of the clip’s thermal response. By comparing the simulation results to the experimental data, we were able to determine the most suitable boundary condition for the clip end, which is attached to the receiver's supporting structure. Furthermore, the experimental data was compared to an analytical solution for the temperature evolution of a fin that took into account the cooling effect of natural convection and radiation, yielding a maximum error of 8%.
Copyright (c) 2025 Marta Laporte-Azcué, María Fernandez-Torrijos, Celia Sobrino, Carolina Marugán-Cruz, Domingo Santana https://creativecommons.org/licenses/by/4.0
On the Accuracy and Computational Load of Fast 1D Models for Solar Receiver Parametric Studies
A big challenge consists in maximizing the thermal efficiency of volumetric solar receivers that are used to collect solar energy and heat-up a heat transfer fluid in renewable energy systems. Parametric studies provide an undisputed aid in early design stages and fast computational models are important to rapidly test novel configurations. In this paper, a comprehensive analysis to assess the accuracy and the computational load of 1D and 3D models compared to relevant literature data is presented. A 1D finite volume model and a 1D explicit model based upon the thermal resistance network are built by solving the solid and fluid energy balances and results are compared to accurate 3D CFD simulations of a solar receiver consisting of a silicon-carbide absorbing structure. The calculated air and solid temperatures are compared to literature findings on a receiver test geometry for different heat transfer fluid velocities. Results show that fast 1D models provide very accurate results with a maximum error of 2%-5% with respect to the reference in a computational time of few seconds, two order of magnitude lower than the one needed by accurate 3D CFD simulations.
Copyright (c) 2025 Carmine Sabia, Simone Zavattoni, Maurizio C. Barbato https://creativecommons.org/licenses/by/4.0
Inverse Heat Transfer Analysis for Estimating Heat Flux in Solar Tower Receivers
Solar power tower plants are utilized to harness solar radiation for large-scale electricity generation. The concentrated solar radiation is absorbed by the central receiver to heat a transfer fluid, which is typically a mixture of 60% sodium nitrate (NaNO₃) and 40% potassium nitrate (KNO₃) to temperatures up to 565°C. Extreme conditions, including high temperatures and variable heat flux, are experienced by these central receivers, necessitating precise thermal measurements to optimize energy production and maintain efficiency. In this paper, an in-house code based on an inverse analysis technique is developed to determine the absorbed heat flux on the surface of the concentrated solar power (CSP) receiver tube, using surface temperature measurements as input. It is found that a single temperature measurement from the frontal part of the tube (0 ≤ θ < 90°) is sufficient for the estimation of the absorbed flux within an acceptable deviation. Additionally, noise is incorporated into the input temperature data to evaluate the reliability of the code under fluctuating conditions typical of real-world applications. The effectiveness of the code in this scenario is demonstrated, reinforcing its potential for practical applications.
Copyright (c) 2025 Vahid Safari, María Fernandez-Torrijos, Antonio Acosta-Iborra, Celia Sobrino https://creativecommons.org/licenses/by/4.0
Opacity Measurement of Particle Curtain of Obstructed Flow Particle Heating Receivers
Understanding particles flow behavior is of paramount importance in designing obstructed flow particle heating receivers (OF-PHR), and one of the important metrics is opacity of the particle curtain. In this work, the opacity is defined geometrically, i.e., ratio of area covered by the particles to the total area of the curtain. Particle curtain opacity of an OF-PHR having a single row obstruction was measured. The obstructions tested were perforated plates with two different holes-arrangements, i.e., parallel and staggered. Plate thickness, hole diameter, and pitch were measured to be 1.38, 2.84, and 4.29 mm, respectively, with angles of 60° between three adjacent holes. Two different fall distances (release point) above the obstruction were tested: 30 mm and 60 mm. The tilt angle and mass flow rate used were fixed, i.e., 0° and 1.91 kg/(s∙m), respectively. The opacity was measured across a region for every 20 mm below the obstruction (0-20, 20-40, 40-60, and 60-80 mm); the opacity encompassing the whole region (0-80 mm; overall opacity) was also measured. It was found that the fall distance affects the opacity a little, i.e., doubling the distance from 30 to 60 mm only increased the opacity by 14.4% (relative change) at most. Parallel and staggered hole arrangement resulted in very close values of particle curtain opacity. Finally, it is concluded that to ensure opacity values to remain equal or greater than 85% throughout PHRs with multiple rows downstream, spacing between the perforate plate should be no greater than 40 mm.
Copyright (c) 2025 Rageh Saeed, Ph.D., Eldwin Djajadiwinata, Ph.D., Nader S. Saleh, Ph.D., Shaker Alaqel, Ph.D., Prof. Hany Al-Ansary, Brantley Mills, Flint Pierce, Prof. Abdelrahman El-Leathy, Dr. Syed Noman Danish, Prof. Zeyad Al-Suhaibani, Dr. Zeyad Almutairi, Dr. Sheldon Jeter https://creativecommons.org/licenses/by/4.0
Techno-Economic Optimization of Falling Particle Receivers for Solar Tower Plants
Solid particle receivers are proposed as the next generation of receivers for solar tower CSP plants as they are able to overcome the temperature limits of solar salts. However, maximizing their performance requires robust design optimization tools. Therefore, this study proposes a methodology for the techno-economic optimization of the design of falling particle receivers for polar-field solar tower CSP plants. Given a specific solar field and location, the optimized design is derived using a parametric approach based on Levelized Cost of Electricity (LCOE) minimization, varying the height and the width of the receiver, as well as, the size of thermal energy storage. Methodology is applied to a 100 MWth solar tower plant in Daggett, California, and the results show that the receiver sized using the proposed approach can achieve LCOE of 80.1 $/MWh that is by 2.2 % lower compared to the LCOE of the receiver sized only through on-design performance maximization.
Copyright (c) 2025 Filip Sobic, Giancarlo Gentile, Marco Binotti, Andrea Giostri, Giampaolo Manzolini https://creativecommons.org/licenses/by/4.0
Active Thermal Insulation – A Possible Option to reduce Thermal Inertia of Cavity Receivers
An Active Thermal Insulation (ATI) is proposed as suitable option to reduce the transient response of high-temperature cavity-type solar receivers. It consists of a straight tubes bundle, embedded in the insulating material, covering the entire receiver length through which the heat transfer fluid (HTF) is fed prior being injected into the cavity. The implications of adding the ATI to the reference absorbing gas solar receiver were evaluated through a series of 3D CFD simulations campaigns. Two key parameters on the ATI design (i.e., tubes number and radial tubes bundle radial position with respect to the cavity axis) were evaluated assuming the receiver operating at both design conditions (nominal incoming concentrated solar radiation) and part-load (reduced incoming input power). For all the CFD simulations performed, an HTF inlet temperature of 700 °C was assumed with a case-dependent mass flow rate tuned to reach 1’200 °C as HTF outflow temperature. The simulations campaign allowed to observe that a HTF pre-heating, between 4% and 6% with respect to the HTF inlet temperature within the ATI, was achieved for all the cases considered. However, despite this, for some cases the receiver efficiency remained unchanged. The ATI resulted to be beneficial on the receiver efficiency if it is operated at full-load and almost irrelevant in the case of part-load.
Copyright (c) 2025 Simone A. Zavattoni, Philipp Good, Gianluca Ambrosetti, Maurizio C. Barbato https://creativecommons.org/licenses/by/4.0
Decarbonizing Industrial Heat – A Comparison of Embodied Carbon for PV and Enclosed Parabolic Trough Systems
Heat accounts for more than half the world’s energy use. The largest user of heat is industry, and the pressure to decarbonize is high. Tendencies to “electrify everything” are seen everywhere, but electric energy is expensive for medium and high-temperature heat generation compared to burning natural gas. Moreover, electric grids are on average still characterized by significant greenhouse gas emissions per kilowatt-hour. But how about PV behind-the-meter, being cost-efficient and well-established in generating electricity? Is PV also the solution for the provision of industrial process heat? To answer this, we investigate the specific embodied carbon for heat production, comparing a PV system with GlassPoint’s enclosed trough concentrated solar thermal system (CST). We exemplarily analyze the case of an industrial process heat consumer in a sunny region to show the difference in embodied carbon, land use, and also give some cost indications. Our results show that this is not the case: Compared to enclosed parabolic trough collectors, PV is characterized by significantly higher embodied carbon values and needs about three times the land and corresponding structures to generate a given amount of heat.
Copyright (c) 2025 Markus Balz, Verena Göcke, Gerhard Weinrebe https://creativecommons.org/licenses/by/4.0
Factor Estimation for Accounting Dynamic Start-Up Effects in Solar Heat Plants Using Quasi-Static Modeling
Solar heat plants represent a promising solution to decarbonize the industry. However, the industry is reluctant to adopt this technology, largely due to concerns regarding the variability of solar resources. Early-stage projects rely heavily on annual simulation models to inform decision-making processes, underscoring the critical need for accurate predictions of solar plant energy yield. To address this, a methodology has been developed to enhance the precision of heat production estimates in annual steady-state modelling by integrating dynamic effects through the introduction of a heat-up factor. This heat-up factor will be dependent on the initial temperature, the DNI conditions, the heat capacitance of the installation, and the chosen control strategy. The findings demonstrate a significant enhancement in the accuracy of steady-state model simulations with the inclusion of the heat-up factor, effectively capturing the dynamic influence on energy consumption during start-up.
Copyright (c) 2025 Magdalena Barnetche, Tim Kotzab, Tobias Hirsch, Robert Pitz-Paal https://creativecommons.org/licenses/by/4.0
Hybrid Concentrated Solar Thermal and Wind Resistive Heating Systems as Key for Competitive Low Emission Industrial Process Heat Generation
Concentrated Solar Thermal (CST) has been addressed as a promising technology for industrial heat decarbonization; however, its use is still limited to low-medium temperature processes (50-250°C). The following analysis explores its feasibility at high temperature employing a parabolic trough solar field with a direct two-tank storage configuration using molten salts both as heat transfer fluid and storage medium, to provide a constant 10 MWTH power to heat up a process fluid to 500°C. Through an economic optimization, various levels of process decarbonization are examined, also including CST hybridization with resistive electric heating powered by photovoltaic and wind energy generation and computing CO2 emissions on a life cycle assessment (LCA) basis. The results indicate that CST is a viable alternative to direct electrification up to 30-50% process decarbonization, while hybrid systems show potential to reduce costs up to 40% at high decarbonization levels. Moreover, although achieving 100% process decarbonization remains still unfeasible, decarbonization levels up to 80-95% appear economically viable when considering up-to-date costs and the forecasted carbon tax.
Copyright (c) 2025 Marco Colombi, Paolo Colbertaldo, Matteo Carmelo Romano, Marco Binotti https://creativecommons.org/licenses/by/4.0
Design of an Air-Fed PTC Solar Field Integrated With a Rock Bed-Based Thermal Energy Storage System
Integrating solar energy to provide heat for industrial processes represents a viable solution aligned with the ongoing energy transition. Parabolic trough collectors (PTCs) are a reliable and mature technology within this context. This study addresses the performance of an industrial air-drying plant integrated with a PTC solar field and a thermal energy storage (TES) system comprising two rock beds operating in parallel. To improve the exploitation of solar radiation, pressurized air was used as the heat transfer fluid for the PTC due to its high temperature limits. A parametric analysis was conducted to evaluate the impact of solar field size on performance, varying both the number of modules in series per string and the number of parallel strings. Results show that the solar fraction (SF) increases with the number of parallel strings, while increasing the number of series modules initially raises the SF to a peak before slightly decreasing. The maximum SF achieved was 85% with a TES volume of 96.24 m³ and a solar field comprising 12 modules in series and 4 parallel strings, resulting in a total collection area of 3450 m².
Copyright (c) 2025 Antonio Cristaudo, Francesco Nicoletti, Francesco Rovense, Walter Gaggioli, Vittorio Ferraro, Natale Arcuri https://creativecommons.org/licenses/by/4.0
A Techno-Economic Comparison of CST and Conventional Cooking Technologies in West Africa
Clean and affordable cooking remains a critical challenge in sub-Saharan Africa, where traditional biomass-based methods create health, environmental, and economic burdens. This study compares the economic viability of Concentrated Solar Thermal (CST) cookers, Fresnel Lens and Parabolic Trough Collector (PTC), with traditional charcoal stoves in rural Nigeria and Ghana using the Levelized Cost of Cooking a Meal (LCCM). While charcoal stoves offer the lowest short-term cost ($0.07628/meal), CST cookers become more economical over time, with the Fresnel Lens achieving an LCCM of $0.1432/meal over a 30-year lifespan. The PTC offers flexibility but has a higher cost due to its advanced design. The study emphasizes the potential health and environmental benefits of CST cookers, along with policy recommendations for overcoming adoption barriers through subsidies and innovative financing.
Copyright (c) 2025 Zaharaddeen Ali Hussaini, Mounia Karim, Khalifa Aliyu Ibrahim, Zhenhua Luo, Christopher Sansom, Tugba Gurler, Johnson Okeniyi, David Akraka, Saifullah Ali https://creativecommons.org/licenses/by/4.0
Evaluation of Flow Patterns for Direct Steam Generation
In solar Direct Steam Generation (DSG) systems, steam is produced directly in the solar field instead of producing it in a steam generator. Liquid water is fed to the solar field and is heated as it flows through the absorber pipes until it starts to evaporate and a two-phase flow develops. The resulting two-phase flow can take various forms, such as slug flow or annular flow, depending on the vapor content and other influencing variables such as the mass flow through the absorber tubes. There are flow patterns that are unfavorable for the operation of a solar thermal system. In particular, a stratified flow with a high vapor content can lead to the formation of dry areas in the upper inner walls of the absorber tube. At these areas, the heat can no longer be sufficiently transferred to the liquid, so that the wall temperature rises and the tubes can become deformed leading to the breakage of the glass cover [1,2,3,4]. In addition, further mechanical loads can be added by the momentum inherent in the slug flow. The annular pattern is a particularly advantageous flow pattern for direct evaporation. In this case, the liquid flows as a ring along the wall through the absorber tube, while the vapor flows inside the liquid. This ensures that the heat is absorbed evenly by the liquid. In the Jordan Optimizing Solar Steam for Industry (JOSSI) project, a measurement campaign was carried out with the aim of recording the two-phase flow patterns within the horizontal absorber tubes and investigating their occurrence under different operating conditions.
Copyright (c) 2025 Navina Konz, Eckhard Schleicher, Mohammed Smeirah, Marwan Mokhtar, Dirk Krüger https://creativecommons.org/licenses/by/4.0
The publication provides an insight into current developments in solar thermal process heat generation. In the first chapter, the experiences with the commissioning of a parabolic trough field at a chemical factory in Turnhout, Belgium are shared. Chapter 2 describes the layout of a parabolic trough field with pressurised water storage at a brewery in Seville, Spain. Finally, there is an overview of developments in solar thermal process heat: The share of concentrating collectors rised in 2023 and more developers signed heat supply contracts, mainly for large-scale solar industrial heat plants.
Copyright (c) 2025 Dirk Krüger, Bärbel Epp, Timo Zippler, Jakob Leicht, Stefan Mehnert, Gregor Bern, Martin Scheuerer, Mark Schmitz, Navina Konz https://creativecommons.org/licenses/by/4.0
Precalciner Geometry Optimization Considering H2O and CO2 Heat Transfer Fluid for Cement Production
The cement industry accounts for 3 – 5% of global CO2 emissions and is difficult to decarbonize due to the high temperature used in the process. The cement raw material requires temperatures up to 900 ℃ for calcination and 1500 ℃ for sintering. Synhelion has developed an absorbing-gas solar receiver which can provide 1500 °C heat to the process via an H2O/CO2 heat transfer fluid to provide fossil-free heating for the preheating and calcination stages. However, very little work has been done to investigate the viability of solar-heated H2O and CO2 gases to efficiently calcine the cement raw meal relative to conventional gas-fired precalciners. The objective of this study is to present an optimized small scale precalciner considering particle suspension, flow dynamics, heat transfer, and thermochemistry of the raw meal when using H2O and CO2 gases. The optimization of the precalciner geometry using a CFD model developed in ANSYS is presented.
Copyright (c) 2025 Javier Martell, Brantley Mills, Nathan Schroeder https://creativecommons.org/licenses/by/4.0
Solar Heat for Commodity Production: Mapping and Comparison With Fossil Fuel and PV
A systematic assessment of concentrated solar thermal (CST) energy and its levelized cost of heat (LCOH) is essential to demonstrate the global potential of CST-energy for decarbonizing industrial heat demand – especially, since time is running out to tackle climate change and a significant part of industrial heat demand can be covered with CST as solar heat for industrial processes (SHIP). For this study, CST-LCOH in dependence of the DNI (direct normal irradiance) are obtained from literature as the annual energy yield changes with DNI and thus, the LCOH changes accordingly. These are mapped for Spain and compared locally with fossil fuel- as well as PV-based heat. A sensitivity analysis is performed for CST-LCOH, varying it by ±10 %, and including an implementation of CO2-taxes of 0, 50 and 100 €/t CO2 for the fossil fuels coal and natural gas. In all cases, if a renewable source is cheaper than fossil fuels, it is overwhelmingly CST. The margin for CST-energy, obtained as the difference of fossil fuel price with CST-LCOH, divided by CST-LCOH and which can also be interpreted as the relative margin from CST-LCOH to -price, reaches in the extreme case 139 % for fossil fuel prices in 2022 and a CO2-tax of 100 €/t CO2.
Copyright (c) 2025 Gkiokchan Moumin, Riccardo Cuneo, Nicole Carina Neumann https://creativecommons.org/licenses/by/4.0
Numerical Modelling of a Solar Thermochemical Heat Transformer for Industrial Heating Applications
Replacing fossil fuel-based industrial heating systems with sustainable alternatives such as solar thermal systems is necessary for achieving sustainable development goals. Often low-concentrated solar collectors are cheaper yet their low-temperature output limits their applications in the industry. The thermochemical heat transformers can be integrated with these collectors to achieve an upgraded output temperature without electricity consumption. Furthermore, these thermochemical systems have an inherent capability of heat storage in chemical bonds thereby mitigating the intermittency issue of solar energy sources. In this research, an innovative packed-bed thermochemical reactor in a closed system configuration is introduced and simulated numerically. The main objective of this analysis is to scrutinize how well the proposed design operates in terms of heat and mass transfer. In this reactor, SrBr2 hydrate is used as the thermochemical material. The study indicates that the proposed design can potentially upgrade the temperature by 100 °C and maintain it at 300 °C for about 40 minutes. This modular design, which can be scaled up easily for large applications, predicts the full conversion of reactions and shows a flexible temperature boost of low-concentrated collectors output.
Copyright (c) 2025 Ramin Roushenas, Marco Ballatore, Artem Sybir, Aldo Cosquillo, Marc Linder, Abhishek K. Singh https://creativecommons.org/licenses/by/4.0
Assessment of Small-Scale Parabolic Trough Collectors for Integration in Industrial Process Heat
This study deals with the preliminary analysis of a small-scale Parabolic Trough Collector (PTC) installed on a rooftop at an industrial complex for the production of process heat. Four scenarios, featuring Heat Transfer Fluid (HTF) outlet temperatures from the PTC of 120°C, 150°C, 200°C, and 250°C, were assessed, varying both collector surfaces and storage capacities; the Levelized Cost of Heat (LCOH) was evaluated for each configuration. The analysis considered data from a commercially available PTC, selected based on a survey among research and industrial partners, and integrated into the System Advisor Model (SAM) libraries. Meteorological data from a North Italian site, characterized by a low annual DNI value, was also considered, assuming this location for the solar plant installation. Economic evaluations employed both literature reviews and real-component purchase price assessments conducted by the partnership. The findings suggest that a LCOH between 4.30 and 4.83 c€/kWh is achievable, with the HTF outlet PTC temperature of 200°C emerging as the scenario allowing for the lowest LCOH due to its balance between the costs of the plant, particularly those related to storage systems, and the thermal energy output.
Copyright (c) 2025 Francesco Rovense, Walter Gaggioli, Fabio Grisoni, Marco Rottoli, Maurizio De Lucia, Leonardo Nibbi, Michele Salvestroni, Filippo Cottone https://creativecommons.org/licenses/by/4.0
Acceptance of a Solar Field Composed of Small-Size PTC Applying to Standard ISO 24194
The verification of solar field performance is possible through international standards EN ISO 24194 since 2022 and using results of standard ISO 9806 from the collector testing previously. However, for concentrating solar collectors this verification is not always done by the industry, and the large-size collector efficiency are guaranteed by the contractor from different components separately or a test done in an existing facility.
Copyright (c) 2025 Fabienne Sallaberry, Alberto García de Jalón, Roberto Astiz, Egoitz San Miguel Carrancio https://creativecommons.org/licenses/by/4.0
Summary of Standardization for Concentrating Solar Plants in Industrial Processes
The Solar Heat Integration in Industrial Processes (SHIP) covers a wide range of temperature applications, from low temperature for which need flat plate collectors (FPC) or evacuated tubes collectors (ETC), to high temperature which need larger parabolic-trough collectors (PTC), linear Fresnel (LFR) or solar tower (ST), like the one installed in Concentrating Solar Power (CSP) plants. This paper aims to present a summary of all the existing standards (published or in work process) that should be used in a SHIP plant to regulate and ensure the products used in those renewable energy thermal plants.
Copyright (c) 2025 Fabienne Sallaberry, Alberto Garcia de Jalon, Egoitz San Miguel, Ana María Mariblanca, Sandra Cubero, Loreto Valenzuela https://creativecommons.org/licenses/by/4.0
Evaluating the Potential of Solar Heat Production for the Food and Beverage Industry in Cyprus From 2024 to 2035
The increasing heat demand in Cyprus' F&B industry presents an opportunity to leverage the abundant solar resources of the country as a sustainable alternative to fossil fuels for industrial processes. To project the final energy consumption (FEC) of the national F&B industry from 2024 to 2035, the GDP (PPP) is used as an exogenous variable. A regression model is obtained with an adjusted correlation coefficient (R²) of 85.8%. For the projections, two economic growth scenarios are considered (positive, PEG, [+3%] and negative, NEG, [−1.5%]), combined with two scenarios for solar technology deployment (business-as-usual, BAU, [2%] and large, LTD, [20%]). Additionally, dynamic simulations in TRNSYS are conducted to estimate the annual yield of a model SHIP plant using Parabolic Trough Collectors. The modelled system, consisting of a total collector area of 660 m² and a thermal storage of 30 m³, yielded 4,320 MJ/m² of thermal energy. It was found that solar energy could uptake between 10% and 28% of the FEC for the NEG and PEG scenarios, respectively. Moreover, the solar heat potential ranged between 85 TJ and 444 TJ, which represents between 19,780 m² and 102,800 m² of solar collectors, respectively. Lastly, the projections also analyse the reduction of GHG emissions in 2035 compared with the baseline year (2023), where the NEG-LTD scenario achieved a reduction of 71%; meanwhile, the PEG-BAU scenario presented an increment of 25% in the GHG emissions.
Copyright (c) 2025 Juan Pablo Santana, Antonio Arto Delgado, Abel Climente García, Ivan Acosta-Pazmiño, João Gomes https://creativecommons.org/licenses/by/4.0
Estimation of Industrial Heat Balance Based on Actual Plant Data: A Case Study for Cement Plant
The industrial sector plays a significant role in anthropogenic effect on the environment due to greenhouse gases emissions associated with energy-intensive processes. To advance in the sustainability goals, it is essential to propose new modeling methodologies to assess the yield performance of clean technologies on industrial processes. However, due to the complexity and variety of such processes it is particularly challenging to assess the non-linear performance of industrial process in terms of heat loads, temperature, and others. The present study introduces a novel methodology to configure an estimation model of the heat released by the clinkering process in the cement industry, based only on operational data. Furthermore, a methodology is proposed to evaluate the correlation between the heat of the process and the operational parameters. The result of this methodology provides a function for the heat consumed or released by the chemical reactions of the process, based on the relevant operational parameters. The approach proposes a global specific enthalpy, parameter that represents the response of the process, only through the heat consumed or released by the chemical reactions. A methodology is proposed for evaluating the correlation of operational parameters with the proposed specific enthalpy. The methodology is validated by assessing the pyro-processes in the cement industry, renowned for its high energy intensity and pollution emissions. The proposed methodology could facilitate the evaluation of clean technologies into different industrial processes. This approach can guide industries in identifying opportunities for reducing pollution emissions while optimizing energy efficiency.
Copyright (c) 2026 Ian Wolde, Allan Starke, Alexandre Da Silva, José Cardemil https://creativecommons.org/licenses/by/4.0
Modular Solar Drying and Thermal Energy Storage System Configuration Assessment
Solar drying is an effective method for preserving food and enhancing its characteristics by removing moisture using ambient air and elevated temperatures. This technology, made for harnessing solar energy, offers a sustainable alternative to conventional drying methods, reducing the consumption of fossil fuels. This study investigates the configuration of a solar drying system for kiwi slices, based on flat plate collector (FPC) combined with packed bed thermal energy storage (PBTES) using copper slag as the storage medium. The research assesses both unidirectional and bidirectional configurations of the storage unit flow to determine the effect on the drying process. The analysis is supported on experimental validation of the thermal models for the FPC and PBTES unit, along with the calibration of the drying model using existing data. Results indicate that unidirectional flow provides better outcomes with smaller storage volumes, whereas bidirectional flow may offer superior performance with larger storage volumes. The maximum plant factor obtained was 93.3% for the bidirectional configuration with a solar field size of 10 m2 and storage volume of 3141 lt. A careful calibration of the thermal system is necessary to avoid suboptimal configurations that either underutilize solar energy or risk overheating the product. The use of a bidirectional configuration with solar heat could lead to a better process performance without the need for external heating.
Copyright (c) 2025 Ian Wolde, Matias Molina, Ignacio Calderon-Vasquez, Nicolas Pailahueque, José Cardemil https://creativecommons.org/licenses/by/4.0
Numerical Investigation of Novel Parabolic Trough Receiver Configurations Using Liquid Sodium as Heat Transfer Fluid
This paper conducts a numerical investigation of the performance improvement of a Parabolic Trough Collector (PTC) receiver using Computational Fluid Dynamics (CFD) simulations performed in ANSYS Fluent. The study aims to evaluate novel receiver configurations by comparing a conventional receiver (Case 1) with three innovative configurations (Cases 2, 3, and 4), using liquid sodium as the heat transfer fluid (HTF). The model’s accuracy is validated against experimental data and theoretical expressions from the literature. Simulations are performed across various mass flow rates to assess key parameters, including the Nusselt number, friction coefficient, thermal efficiency, and circumferential temperature difference. The results indicate that Case 3 demonstrates the highest thermal performance among the configurations. Specifically, the novel receiver configurations consistently outperformed the conventional receiver. The Nusselt number increased by 29.84%, 126.1%, and 10%; the friction factor rose by 178%, 305%, and 17%; the thermal efficiency improved by 3.6%, 4%, and 3.4%; and the temperature difference decreased by 4.05%, 13.2%, and 1.31% for Confs 2, 3, and 4, respectively. Additionally, liquid sodium significantly enhanced the thermal performance of the PTC due to its superior thermal properties. These findings underscore the effectiveness of the proposed receiver configurations and the advantages of using liquid sodium as the HTF, offering a promising approach to improving PTC efficiency.
Copyright (c) 2026 Meriem Chaanaoui, Justin Byiringiro https://creativecommons.org/licenses/by/4.0
Measurement of the Density of Biphenyl / Diphenyl Oxide Mixtures at Isobaric Conditions
The density of the eutectic mixture of biphenyl and diphenyl oxide was measured at 12 to 40 bar and up to 400 °C for the first time. An unused quality as delivered and a used quality from a parabolic trough plant were tested. Significant compressibility was observed for both qualities giving rise to density increases of 3% for the unused fluid at 40 bar and 4.8% for the used fluid compared to the technical data sheet of Dowtherm A.
Copyright (c) 2025 Christian Jung, Carsten Spenke https://creativecommons.org/licenses/by/4.0
Enhancing the Thermal Efficiency of Longitudinally Finned Parabolic Trough Solar Receivers
The objective of this study was to investigate the conjugate heat transfer in a longitudinally finned parabolic trough solar thermal receiver tube, taking into account the non-uniform heat flux distribution along the tube circumference. Both smooth and longitudinally finned stainless steel receiver tubes, with Syltherm 800 oil as the heat transfer fluid, were numerically simulated using Ansys Fluent 2023R2 with periodic boundary conditions for Reynolds numbers ranging from 20,000 to 60,000. Two fin configurations were investigated in the study: two fins - of little practical interest but very useful to gain physical insight into the problem - and six fin receiver tubes. In addition, sub-cases within the two- and six-fin configurations were analyzed by varying the position and height of the fins. It was found that fins on the bottom side, exposed to a higher heat flux, mainly enhanced conduction, while fins on the top side mainly enhanced convection by directing higher velocity values toward the bottom side. To reduce hot spots and improve thermal efficiency, fins should be located in higher heat flux areas, and shorter fins on the bottom side and longer fins on the top side are recommended. Finally, the performance evaluation criteria were assessed using both the inner Nusselt number, based on the convective heat transfer coefficient as commonly reported in the literature, and an overall Nusselt number, based on the total heat transfer resistance of the receiver. For the most favorable two-fin and six-fin cases, the maximum temperature in the receiver decreased by a maximum of 16.7 K and 30 K, respectively.
Copyright (c) 2025 Vinod Kumar, Stefano Savino, Carlo Nonino https://creativecommons.org/licenses/by/4.0
Numerical Modelling of Solar Receivers Equipped With TPMS Structures
In this study, two planar high-temperature solar receivers, equipped with Triply Periodic Minimal Surface lattices of Diamond and SplitP, were analysed numerically. These receivers were manufactured and experimentally tested in a previous study. Different RANS turbulence models, including Lag EB κ-ε, κ-ω SST (Menter), and Realizable κ-ε two-layer, were evaluated, and their results were compared with experimental data. A comprehensive validation revealed that the Lag EB κ-ε and κ-ω SST (Menter) models have the smallest deviation from the experimental data. The sample with the SplitP lattice demonstrated superior thermal performance with higher thermal efficiency, higher useful heat, and exhibiting a slightly lower maximum surface temperature and a narrower high-temperature region.
Copyright (c) 2025 Arsham Mortazavi, Hossein Ebadi, Cecilia Piatti, Eleonora Gajetti, Luca Marocco, Laura Savoldi https://creativecommons.org/licenses/by/4.0
Experimental Investigation of Heat Losses in Hydrogen-Doped Parabolic Trough Receivers
This study investigates the impact of hydrogen presence in the annulus space of heat-collecting elements (HCEs) used in parabolic trough solar power plants. Hydrogen, formed during degradation of the heat transfer fluid diphenyl oxide/biphenyl (DPO/BP), can permeate into the annulus and significantly increases heat loss due to enhanced conductive heat transfer. Following the resistance heating method defined tin the technical specification IEC TS 62862-3-3, heat loss measurements were conducted on HCEs before and after hydrogen doping at various absorber temperatures (100–400 °C). Results showed heat losses up to four times higher in hydrogen-doped receivers, reaching 867 W/m at 400 °C, compared to 211 W/m in evacuated units. Uncertainty analysis confirmed measurement reliability. The data confirms hydrogen’s detrimental effect on thermal performance and supports the need for improved hydrogen control in operational solar power plants with parabolic troughs.
Copyright (c) 2025 Loreto Valenzuela, Rafael López-Martín, Carmen M. Amador-Cortés, Christoph Hilgert https://creativecommons.org/licenses/by/4.0
Optimization of Hybrid Renewable Energy System Incorporating Heliostats with Thermal Energy Storage, PV and Battery Storage for Enhanced Energy Flexibility and Reliability
The urgent need for sustainable energy solutions to combat climate change and the growing global energy demand has stimulated the development of renewable energy technologies. Among these, hybrid renewable energy systems (HRES) that combine multiple energy sources promise enhanced efficiency, reliability and flexibility compared to single-source systems. This research focuses on a novel HRES configuration that integrates a concentrated solar power named solar tower with thermal energy storage (TES), photovoltaic modules and battery energy storage systems (BESS) in North Togo. The study aimed to maximize the energy produced, while reducing costs and finally evaluated the environmental aspect saved. We use parametric optimization through SAM to determine the optimum levelized cost of energy and net present value. SAM software was used for heliostat modelling. The single-owner model was used for financial analysis. The results demonstrated the project's financial viability and environmental impact, with an LCOE of $0.14kWh-1 indicating a competitive cost of energy production and an IRR of 14.87% showcasing strong investment returns. A high NPV of $9,307,001 indicated some good interest in the proposed HRES. Furthermore, the significant reduction of 25,815.7513 tons of CO2 emissions highlights the project's substantial contribution to sustainability and carbon footprint reduction.
Copyright (c) 2025 Maklewa Agoundedemba, Chang Ki Kim, Hyun-Goo Kim, Raphael Nyenge, Nicholas Musila https://creativecommons.org/licenses/by/4.0
Validation of Solar Extinction Model at Plataforma Solar de Almería
Solar extinction should be one of the most important factors to select the best locations for solar tower plants. The optical path between the heliostats and the receiver (slant range, SR) very often exceed 1 km. This distance could involve many particles in the atmosphere, which absorb and scatter the reflected solar radiation. Therefore, it is necessary to know the radiative losses due to solar extinction at the location and to have models rigurously validated with experimental data. At PSA there is a database with more than 6 years of solar extinction measurements. These data have been obtained thanks to a solar extinction measurement system developed by The Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT). This database allowed the development of a Typical Solar Extinction Year (TSEY). This TSEY presented an average annual solar extinction value of 6 ± 2 % for a measurement distance of 741.63 m. With this amount of data a model to estimate solar extinction has been validated at PSA. The input data used were the aerosol optical depth (AOD) and the SR. For this purpose, average daily extinction values were estimated with a model. From this new simulated database, a synthetic TSEY was developed in order to compare it with the experimental TSEY. In both cases, the average annual solar extinction values were in agreement with the value of 6 ± 2 % (741.63 m). By this way, the model has been validated and it could be used to estimate solar extinction worldwide.
Copyright (c) 2025 Noelia Simal Pérez, Jesús Ballestrín, MªElena Carra, Jesús Polo, Aitor Marzo https://creativecommons.org/licenses/by/4.0
Enhanced On-Site Characterization of Heliostat Surface via Direct Calculation of Reflected Beam’s Normal Vectors
In this study, the results obtained through the algorithm presented for calculating the surface error will be analyzed. This aims to achieve a more precise characterization of the heliostat surface, independent of external conditions such as environment or solar field configuration. This can be accomplished by acquiring data obtained through HelioscharPlus characterization system, which has been presented in previous works and is distinguished by being based on data measured in real conditions, providing insights into the actual operation of the heliostat. This measurement mode offers the possibility to apply refinement process to the results, crucial for enhancing the accuracy of the characterization and aligning it more closely with real-world conditions.
Copyright (c) 2025 Kontxi Isabel Aginaga Etxamendi, Angel M. Andueza, Adrian Peña-Lapuente, Sonia Escorza, Marcelino Sanchez https://creativecommons.org/licenses/by/4.0
Fast Optical Receiver Surface Characterization
This paper presents an extension of the "Maximum Front Method" for assessing the spatially varying Bidirectional Reflectance Distribution Function on curved surfaces, specifically the receiver of a Solar Tower. The receiver, which links the solar field and the thermal cycle of a ST, operates under high solar concentrations and temperatures. This method is vital for efficient plant operations, enabling regular assessment of the receiver coating quality, early detection of degradation, and facilitating other measurement techniques. The paper discusses the challenges faced with the far field SVBRDF measurement when dealing with complex surfaces, including the trajectory of the light spot, and dealing with distance dependant reference intensity values. These challenges were addressed through a geometric approach and simulations were carried out using blender® to validate the method, showing its effectiveness on cylindrical and structured surfaces. However, accurately determining each component's spatial position was a persistent challenge for the practical demonstration. The paper suggests future research could consider line overlaps to maintain the evaluated area and develop methods to determine pipe positions directly from captured images. In conclusion, this method provides a foundation for solar tower receiver applications to monitor receiver state and improve robustness and efficiency in solar tower operation.
Copyright (c) 2025 Gregor Bern, Sara Zizzania, Moritz Bitterling, Thomas Schmidt https://creativecommons.org/licenses/by/4.0
OpenCSP: Collaborative Code and Data For CSP
We are announcing OpenCSP, an open-source platform including source code, applications, and data to enable collaborative development for the CSP community worldwide, supporting industry, research, and education. OpenCSP includes components of code, data, mechanical designs, tools, and documents, all provided under an open-source license allowing unlimited use. The OpenCSP code development environment is set up to enable collaborative team development of high-quality software, yet OpenCSP welcomes both polished code and rough code-in-progress. The goals of OpenCSP are to accelerate transfer of CSP metrology and analysis tools to industry, provide a resource for businesses supporting CSP, support CSP education, and to provide a community collaborative development environment to enable teams to build new advanced CSP applications more quickly, and to speed their deployment.
Copyright (c) 2025 Randy Brost, Benjamin Bean, Felicia Brimigion, Margaret Gordon, Evan Harvey, Madeline Hwang, Tristan Larkin, Miranda Mundt, Nicholas Phelps, Braden Smith, Carly Tanaka-Lubensky https://creativecommons.org/licenses/by/4.0
High-Resolution Flux Measurement for High-Flux Solar Simulators
Concentrated solar power (CSP) systems impose high demands on individual components such as receivers, optical elements, etc. due to high solar flux. Characterisation of these components often requires measurements under defined, constant conditions, which can be challenging or even impossible in real-world applications due to changes in irradiance, weather conditions, accessibility, tracking inaccuracies, etc. . Solar simulators are used for this purpose, with the challenge of providing sun-like, uniformly distributed and highly concentrated light. This paper presents an approach to automatically investigate the irradiance distribution of concentrated light in a solar simulator. A water-cooled flux meter (thermopile) is used in combination with an XY table to scan the area of interest, resulting in a high-resolution image of the irradiance distribution in the target area. The results are presented and discussed based on measurement data recorded in a real solar simulator. Issues such as sensor area i.e. spatial resolution, light spectrum dependence, temperature influence, and measurement speed are addressed.
Copyright (c) 2025 Richard Felsberger, Armin Buchroithner, Bernhard Gerl, Hannes Wegleiter https://creativecommons.org/licenses/by/4.0
Opto-Electronic Sensor for HTF Early Leak Detection Based on Infrared Absorption
We propose an early leak detection sensor for HTF (Heat Transfer Fluid) leakages by measuring the absorption of infrared radiation by the HTF components. This sensor, that can be installed inside the insulation around ball joints or other elements in a Concentrated Solar Power (CSP) plant, detects leaks by sensing mid-infrared absorption at specific wavelengths. The sensor includes a reference signal to correct for external factors like temperature changes and sensor degradation. Laboratory tests have validated the sensor performance under various conditions. The sensor enhances the sustainability of solar thermal plants by providing early leak detection and is easily adjustable for different HTFs by changing the IR (Infrared) radiation sensing bands.
Copyright (c) 2025 David Izquierdo, Maria Heras, Cristina Pelayo, Adrián Peña, Marcelino Sánchez https://creativecommons.org/licenses/by/4.0
Optical Fiber as Solar Radiation Collector for Radiometric Measurements
The feasibility of using optical fibers as solar radiation collectors in radiometric measurement devices and instruments is discussed, taking into account the various characteristics of the fibers that affect the measurements, with a special focus on numerical aperture. The discussion is supported by various results using the fiber to measure direct normal irradiance.
Copyright (c) 2025 Manuel Jerez, Alejandro Carballar, Joaquín Granado https://creativecommons.org/licenses/by/4.0
Advanced Drone-Based Alignment Measurements for Parabolic Trough Collectors
A novel drone-based measurement method for the automatic quality check of the field assembly of parabolic trough collectors has been developed. The module as well as receiver alignment of entire parabolic trough loops can be measured using commercially available drones equipped with a visual camera and RTK (real time kinematic) positioning. The measurement principle is based on the geometric relations between aperture edges of the parabolic trough collector and the absorber tube line, which both are measured seamlessly along the collector using robust edge detection algorithms. The measurement method replaces hook-rod based measurements of the receiver alignment and total-station based measurements of the module alignment in a fast and fully automated way while keeping high measurement resolution and accuracy. Due to its speed and versatility to measure receivers with and without protective foil and with the collector in arbitrary orientation, the measurement method can be applied in all project phases ranging from solar field construction over commissioning to operation. The paper presents the progress in the development of the method and the results of the validation measurements performed at the parabolic trough collector loop of the molten salt test platform (EMSP) in Évora, Portugal.
Copyright (c) 2025 Andreas Kämpgen, David Helten, Klaus Pottler, Marc Röger https://creativecommons.org/licenses/by/4.0
Torque in the Rotation Axis of a Parabolic Trough Solar Collector due to Wind Loads
Parabolic trough collector (PTC) solar plants are susceptible to episodes of high speed sustained wind or gusts, which can affect their performance due to aerodynamic loads on the collector. In some collector configurations, the axis of rotation of the collector is directly connected to the flexible joint of the collector, so that torque is also transmitted to the rotation and expansion assembly installed at the end of the solar collector assembly. To obtain accurate measurements of the effect of the wind on the axis of rotation of a PTC, a torque sensor and an inclinometer were mounted at the end of a PTC at the Plataforma Solar de Almería (PSA) (Spain). A series of tests were carried out with different wind speeds and directions to verify the performance of the measurement system in dealing with the structural deformation of PTCs due to wind loads.
Copyright (c) 2025 Rafael López-Martín, Loreto Valenzuela, Carmen M. Amador-Cortés https://creativecommons.org/licenses/by/4.0
Simplified Set-Up for Near-Specular Solar Reflectance Measurement
In Concentrating Solar Power (CSP) plants, mirrors are used to redirect solar radiation onto a receiver. More precisely, the solar radiation, diverging with a half-angle of about 4.7 mrad, impinges off-normal on the mirror. Only the radiation reflected within the acceptance angle of the receiver is geometrically intercepted. Therefore, the kind of reflectance relevant for CSP applications can be defined as “near-specular”; it depends on three angles: solar-divergence, incidence on the mirror and detector-acceptance. Actually, the market is lacking of instruments to properly measure the near-specular reflectance. For that purpose only one custom instrument was set-up at a highly specialized laboratory to measure the spectral near-specular reflectance for both clean and soiled mirrors; in the latter more radiation is reflected beyond the acceptance angle. Now, the Work-Package 4 of the “Recommendations for reflectance measurements on soiled solar mirrors” Project funded by SolarPACES aims to cover that gap by outlining a Simplified Set-Up (SSUp) based on commercial components. It can be replicated by anyone having just basic skills in optics. The concept could even be taken by an industrial player to commercialize an engineered version of SSUp.
Copyright (c) 2025 Marco Montecchi, Florian Sutter, Johannes Wette https://creativecommons.org/licenses/by/4.0
3D-Shape Measurement of Parabolic Trough Mirror Panels:
The 3D-shape round-robin initiative aims to compare the main geometric parameters of 3D shape measurements for parabolic-trough mirror panels, assessed using equipment developed and employed by each participating institution: ENEA, F-ISE, DLR, NREL, and SNL. Except ENEA equipment, all the other are based on deflectometry, also call fringe-reflection method. The round-robin is based on circulating 6 trough mirror panels (3 inner and 3 outer) of RP3 dimensions, with a focal length of 1710 mm, between participating laboratories; a simple and rugged supporting fixture together with precise instruction on how to use it have been provided to make the comparison more reliable. ENEA wrote a custom evaluation software for comparing the results. We observe a reasonable agreement among the mean values of the deviations of height and slopes from the ideal parabola: standard deviation better than 0.1 mm, 0.5 mrad and 0.3 mrad for z, slopeX and slopeY, respectively. The agreement is improved when a software realignment procedure for setting the height values on the support points to the expected ideal values is applied. The absolute difference between pairs of evaluators is sometimes greater than the declared experimental uncertainty; investigation into these deviations is still ongoing.
Copyright (c) 2025 Marco Montecchi, Arcangelo Benedetti, Giuseppe Cara, Francisco Torres, Gregor Bern, Marc Röger, Kristina Blume, Tim Schlichting, Eckhard Lüpfert, Devon Kesseli, Guangdong Zhu, Braden Smith, Randy Brost https://creativecommons.org/licenses/by/4.0
The industrial revolution moved society organization from farming communities distributed on the land, self-sufficient in energy and food provided by the sun, to concentrated sources as oil and natural gas. Now there is a reversal of this trend due to the return to the use of solar energy. We produce electricity with PV panels, but we need also heat, and we do not have any way to do so in a distributed way. We propose a model of collecting, storing, and using the energy locally. The first step, collecting, we discuss in this paper. We propose the use of a large Fresnel lens in glass. To mold the lens in glass we use a modified groove design where the vertical step directs the light to the focal point through reflection by a mirror. The angle between facets is large enough to let the glass fill the grooves. We solve the problem of cost by producing the lens in a cylindrical configuration, extruding and calendaring the glass in a commercial plant for textured glass at a cost of $10/m2. The basic unit size can be realized as an assembly of eight 4x8 feet glass panes, collecting what we expect to be 10kW per unit, at a cost of few hundred dollars per unit for the collecting optic. We will capitalize on the know-how on making the receivers for the Parabolic Reflector geometry. This proposal allows solar heating to be affordable by a homeowner, lowers CO2 emissions.
Copyright (c) 2025 Luigi Fornari, Gianluigi Fornari https://creativecommons.org/licenses/by/4.0
Upscaling and Testing of Air-Based Rotary Solar Thermal Receivers for Concentrated Solar Power Applications
Odqa Renewable Energy Technologies Ltd has successfully scaled its air-based rotary solar thermal receiver design from 10kW to 100kW. A 10kW-scale air-based rotary solar thermal receiver was tested in Odqa’s in-house solar simulator facility in late-2022. Learning from the experience, an improved solar thermal receiver rotor geometry has been developed and built, its mechanical design has been proven in a heliostat field test carried out at PROTEAS, The Cyprus Institute. A Predictive Engineering Analytics approach has been developed to predict the thermal performance and for the purpose of upscaling of the solar thermal receiver. As a result, the thermal design for a 100kW-scale solar thermal receiver has been produced, which subsequently was built at Odqa and tested at the SynLight solar simulator facility at the Institute of Solar Research, German Aerospace Center (DLR).
Copyright (c) 2025 Pok-Wang Kwan, Mark Loasby, Augustin Wambarsie, Chiang Churchill Ngai, Peter T. Ireland, Joe Baddeley, Katarina Marčeta, Orla Mallon, Asli Kaya, Dave Mountain, Scott Battams, Ashley Cooper, MyeongGeun Choi, George Wilson, Kirk Ashley-Morgan, Gediz Karaca https://creativecommons.org/licenses/by/4.0
Preliminary Design of S-CO2 Turbomachinery and its Influence on the Performance of an Integrated Solar Combined Cycle
Supercritical CO2 power cycles emerge as the next-generation standard for Concentrated Solar Power technology mainly due to their high efficiency and reduced footprint. This study investigates the role of the S-CO2 turbomachinery in an Integrated Solar Combined Cycle, and performs the design and optimization of the geometries to maximize their efficiency using mean-line models. Centrifugal compressors, axial-flow and radial-inflow turbines have been considered. Various geometries are identified to achieve similar high efficiencies, highlighting the need for additional criteria in selecting the optimal design. For this particular combined cycle, the results also reveal that variations in turbomachinery efficiency have a relatively minor impact on overall cycle efficiency, with turbine efficiency exerting a more decisive influence than compressor efficiency.
Copyright (c) 2026 Eva Arenas, Marta Muñoz, Alexis Cantizano, José Ignacio Linares, María José Montes, Antonio Rovira https://creativecommons.org/licenses/by/4.0
Effect of Compressor Inlet Swirl on Solar Gas Turbine Performance
An investigation of the effect of various compressor inlet guide vane (IGV) setting angles on the thermodynamic performance of a simple single shaft solar-hybrid gas turbine power generation system (SHGT) is presented. The formulation of models for the individual system components is described, with emphasis on the generation of compressor characteristics for various IGV setting angles. Matching of the components in the integrated system model is shown, for the standard single shaft turboshaft configuration as well as several variable rotor speed turboshaft configurations. The estimated fuel consumption, solar receiver effectiveness, and thermal efficiency are compared for the reference system, SHGTs with IGVs, and variable rotor speed SHGT configurations. The results of the performance calculations for a 40 kWe gas turbine engine indicate that a 4.3 % reduction in full-load fuel consumption is attainable with compressor IGVs set at 9° in the direction of the rotor blade rotation, and a reduction of 25.3 % is attainable with independent and distinct compressor and turbine rotor speeds.
Copyright (c) 2025 Matthew Meas, Johan van der Spuy, Andrew Gill https://creativecommons.org/licenses/by/4.0
Comparison of Shell and Tube Heat Exchangers for CO2 and CO2+SiCl4 Mixtures Transcritical Cycles
Concentrated solar power (CSP) plants have great potential for clean energy production, but their electricity cost is higher than that of noncontrollable renewable energy sources. The main ways to lower the electricity cost are equipment cost reduction and plant efficiency increase. Looking at the power unit, the closed supercritical CO2 (sCO2) cycles offer the efficiency advantage over both the steam Rankine and helium Brayton cycles at high turbine inlet temperatures. Further improvement could be achieved by increasing the critical temperatures using mixtures, allowing condensation at temperatures typical for air-cooled condensers. The sCO2 and CO2 mixture cycles are significantly affected by the performance of the recuperative system and require high pressures (comparable to steam cycles). An increase in efficiency compensates for higher complexity in the design and construction of the plant, according to the authors. High thermal power together with high pressures and temperatures demand customized CO2 heat exchanger designs, which makes them a major part of power cycle specific cost. This paper provides a robust technological solution for the implementation of the above cycles in an industrial setup based on shell-and-tube heat exchangers. Based on the thermohydraulic and mechanical design of EMbaffle® Technology, heat exchangers weight reduction can be quantified in the range of 30 to 60% depending on the application, with additional advantages in terms of logistics and installation (footprint, foundations, etc…). Using the CO2+SiCl4 mixture instead of pure sCO2 leads to a lower weight of primary and high-temperature heat exchangers, while the weight of low-temperature heat exchanger increases.
Copyright (c) 2025 Vladimir Naumov, Marta Mantegazza, Michele Doninelli, Gioele Di Marcoberardino, Paolo Iora, Marco Rottoli https://creativecommons.org/licenses/by/4.0
Preface: SolarPACES 2024, 30th International Con-ference on Concentrating Solar Power, Thermal, and Chemical Energy Systems
Renewable energy technologies are a key element in the journey towards sustainable and secure energy systems. They not only help us neutralize our carbon footprint, but also enable us to harness energy sources that are abundant and more evenly distributed globally. In 2023, the participants in COP 28 committed to triple the installed capacity of renewable power by 2030. Also, the International Energy Agency reports that the annual renewable capacity additions marked a step change in 2023 and are expected to steadily increase over the next years. This huge expansion will be led by market-mature technologies like solar PV and on-shore wind, which are expected to make up each year for nearly 95 % of the renewable electricity capacity additions, until 2030. However, as the penetration of renewables approaches 100%, the availability of clean technologies that allow dispatchable production will no longer be an option, but a necessary element for our energy systems to be not only sustainable, but also flexible and resilient. Also, it has now become very clear that full electrification of our energy uses will not be possible in the short term. The “hard-to-abate” sectors, like energy intensive industries and heavy transport, will require alternative approaches to be decarbonized. Today, industry makes up for roughly 30 % of the total world’s energy consumption and industrial processes require 70 % of their energy input as low-, medium- and, mostly, high-temperature heat. Fulfilling this energy demand in a sustainable way is a challenge that will require the use of multiple energy technologies and vectors. This includes hydrogen and other renewable fuels, but also technologies that can directly produce renewable heat. Concentrating solar thermal (CST) technologies possess all the key features to address these challenges. They can be used to produce (or co-produce) high-temperature heat, electricity, hydrogen and other renewable fuels. They can rely on commercially proven long-duration thermal energy storage solutions, which are not based on critical materials and allow flexible and, potentially, round-the-clock operation. Furthermore, they can support the penetration of non-programmable renewables by providing flexibility and ancillary services to the grid. Several challenges still hinder the deployment of CST technologies. Improving the cost-efficiency is among the first priorities. Research and innovation can partly contribute to this aim, but ensuring a stable pipeline of commercial projects is crucial. In turn, in many markets, today this requires well-designed and stable support policies. From October 7th to 11th, 2024, more than 520 experts and delegates from 41 countries gathered at the Auditorium della Tecnica in Rome (Italy), to attend the 30th edition of the SolarPACES Conference. With 42 years of activity since its inauguration in 1982, the conference has become the world’s reference event for the CST community, which now every year provides an excellent forum for research, industry and policy makers to connect, exchange ideas, build networks, showcase cutting edge innovations, and lay the groundwork for new projects. The Conference boasted a very rich technical program with 4 plenary sessions including 8 keynote presentations and a roundtable discussion, 40 technical sessions with more than 220 talks, 244 posters and a technical visit to ENEA Casaccia Research Center, which hosts the most relevant CST-related research infrastructures in Italy. The participants were greeted during the opening session by the Italian Minister of Environment and Energy Security Gilberto Pichetto Fratin, who pointed out how CST is among the key energy technologies identified by the European Union to achieve its ambitious climate goal of carbon neutrality by 2050 and, accordingly, is expected to contribute to the Italian energy mix in the near future as reported in the National Energy and Climate Plan. This volume collects the 177 full papers submitted for the Conference Proceedings. The papers cover all the 16 conference topics that address a wide and exhaustive range of current issues in the field of CST technologies, from the assessment of solar resource, to the deployment of commercial projects. Almost half of the papers focus on one of three key topics, namely “Analysis and Simulation of CSP and Hybridized Systems”, “Thermal Energy Storage Materials, Media, and Systems”, and “Solar Industrial Process Heat and Thermal Desalination”. This clearly reflects the main trajectories that the CST community has been following in recent years towards the future of the technology. The following papers mark another step to improve the technological and economic performance of CST technologies and foster their further deployment. To the authors of these papers, to those who helped in the organization of the Conference, and to all the participants goes my deepest gratitude.
Copyright (c) 2025 Luca Turchetti https://creativecommons.org/licenses/by/4.0
More Efficient Heliostat Fields for Solar Tower Plants: The HELIOSUN Project
Heliostats could represent up to 60% of the investment cost for solar tower plants with more than 100 MWe of power, then reducing the cost of heliostats would have an important cost reduction of the plant. The Heliosun project approaches this cost reduction from three different perspectives. Firstly, an artificial vision system with object recognition is proposed, which allows the closed-loop tracking control of the heliostats. This system, consisting of the installation of a low-cost camera and processor in each one of the heliostats, will eliminate the positioning sensors and improve the tracking accuracy of heliostat, improving the concentrated solar radiation distribution on the solar receiver surface. Moreover, a correct measurement of the atmospheric attenuation suffered by the solar radiation concentrated by the heliostats on its way to the solar receiver, with distances greater than 1500m in large plants, will allow firstly, to perform an adequate selection of those sites with the best characteristics for the deployment of solar tower plants and to optimize the routine operation of the solar plant. Finally, a ray-tracing simulation software, based on OTSun, is intended to be developed, including a more accurate prediction of the behaviour of a solar tower plant with central receiver considering spectral analysis, as well as including all the experimental results presented above. These three approaches will allow to improve the operation of solar tower plants as a whole, optimizing the operation of the solar receiver and the solar field, increasing the technical and economic efficiency of these systems.
Copyright (c) 2026 Jesus Ballestrin, Loreto Valenzuela , Jesús Fernandez-Reche, Ramón Pujol , Gabriel Cardona , José Carballo , Javier Bonilla , Noelia Estrenera-Pedriza, Elena Carra , Noelia Simal , Rafael Monterreal, Aitor Marzo https://creativecommons.org/licenses/by/4.0
Review of the Operational Phase of the South African Concentrated Solar Power Projects
This paper provides an overview of the six Concentrated Solar Power (CSP) projects in operation in South Africa, comprising 500 MW generation capacity. These projects, in addition to the seventh (100 MW) CSP project currently in construction, were awarded under various bid windows of the Renewable Energy Independent Power Producer’s Procurement Programme (REIPPPP) and commenced operations during 2015-2019. Key operational data up to the end of 2023 are presented, as of when the combined cumulative electricity generation by the six CSP projects reached 10.1 TWh. This represents approximately 81% of the sum of the P50 Energy Yield Forecasts (EYFs) in the respective project Power Purchase Agreements (PPAs), and 9.6% of all electricity generated by the REIPPPP projects by the end of 2023, while the CSP projects constitute 8.1% of total installed capacity (6180 MW) as of December 2023. Factors affecting performance are discussed, including meteorology and outages. Consumption of major utilities is also discussed, comparing to expected values or limits.
Copyright (c) 2025 Jacobus van Zyl, Prinavin Perumal, Alberto Cuellar https://creativecommons.org/licenses/by/4.0
Analysis of Solar Heating Integration in a Liquid Metal Reactor for Hydrogen Production
This study analyses the integration of concentrating solar energy with a liquid metal reactor for methane pyrolysis, configured as a vertical column. It compares two irradiation strategies: distributing radiation along the entire column height versus focusing it on the middle section. Parameters such as irradiance, total power, methane mass flow, and residence time are assessed. Both configurations present advantages and disadvantages, but designs achieving very high temperatures are preferred over those prioritizing thermal homogeneity. The findings provide insights for optimizing solar reactors for efficient hydrogen production.
Copyright (c) 2026 Elisa Alonso, Luis Gonzalez-Portillo, Alberto Abánades https://creativecommons.org/licenses/by/4.0
Solar-Driven Biomass Pyrolysis Plant for Negative-Emission Biofuels Production
As part of the Horizon Europe Project PYSOLO, this study focuses on the integration of a 10 MWTH fast pyrolysis plant with a solar tower system equipped with a rotary kiln particle receiver. Heated particles act as a particle heat carrier (PHC) for the endothermic pyrolysis process, enhancing flexibility and allowing continuous operation compared to directly heated solar reactors. The system’s design, techno-economic analysis and storage capacity optimization are performed considering two operation modes, solar-only and hybrid, in which biochar is combusted in absence of solar energy. Results indicate that, due to the rotary kiln flow regime constraints, its tilt angle has to be limited in a range between 0.5-2° to guarantee particles being in rolling mode, thus penalizing the achievable solar field optical efficiency. On the other hand solar-based pyrolysis can achieve carbon efficiencies close to 0.9 and, thanks to the carbon stored in biochar, net negative emissions equal to -27.05 and -19.45 kgCO2/GJOIL respectively in solar-only and hybrid mode. Moreover, as the pyrolysis section has the most relevant cost share, the system optimization pushes to maximise the pyrolysis plant operating hours (and thus the bio-oil production) to reduce the CAPEX impact on the Minimum Fuel Selling Price (MFSP). For this reason hybrid mode results in being the most convenient (i.e: MFSP of 25.71 vs 21.36 €/GJOIL).
Copyright (c) 2025 Muhammad Ahsan Amjed, Marco Colombi, Juan Rincon Duarte, Clarisse Lorreyte, Gkiokchan Moumin, Matteo Carmelo Romano, Marco Binotti https://creativecommons.org/licenses/by/4.0
Design of a Natural Gas Steam Reforming Process for Hydrogen Production Powered by a Solar Furnace
The work involved in this paper has been developed as part of project NEST “Network for Energy Sustainable Technologies" framed in the PE program "Green Energies for the Future". It aims to develop technologies for the conversion and use of renewable sources that should be sustainable, both from an environmental and a social point of view. In particular, the paper shows the design of a process that employs the high temperature heat produced by a solar furnace, realized at Research Centre of ENEA in Portici, to supply a system for the hydrogen production based on the steam reforming natural gas process. In the direction of the decarbonization of the chemical industry, the solar concentration-based plant appears well compatible with the endothermic stage of a reforming based plant, in which the selected hydrocarbon reacts with steam to produce a hydrogen-rich syngas (to be refined in the further purification stages). [1]
Copyright (c) 2025 Carmine Cancro, Mauro Atrigna, Aniello Borriello, Gabriele Ciniglio, Vincenzo Capaldo, Luigi Mongibello, Valeria Palladino, Antonio Ricca https://creativecommons.org/licenses/by/4.0
Modeling of an High-Concentration Solar Reactor for Dry Methane Reforming
Direct solar-powered reforming of methane has the potential to lower the CO2 footprint of reforming and to harvest solar energy with high-efficiency [1]. Combined with bio-sourced feedstock and recycled CO2 to perform dry methane reforming (DMR), this approach can highly decrease methane reforming environmental impact [2]. Using high solar concentration solar towers or parabolic dishes to provide the highly endothermal reaction heat required for DMR, it is possible to reach the temperatures of conventional reformers, ranging from 800°C up to 900°C. At this temperature, radiation losses are such that high solar concentrations approaching 1000x are required to reach high thermal efficiency, making heat flux management highly challenging. Previous work from Université de Sherbrooke experimentally shown the potential for such reactors to operate under high heat flux [3],[4]. The current work presents the modeling approach used to design these reactors and increase the heat flux within the absorption surface, while maintaining reasonable temperature drop within the reactor. Dimensional analysis if first assess that no diffusion limitation occurs within the reactor and the system can be simulated as a plug flow reactor with porous catalyst. Using DMR and RWGS kinetics from literature with 2D modeling in COMSOL Multiphysics, temperature and reaction rates along the reactor are evaluated showing consistency with experimental values. Parametrical analysis shows that optimal catalyst channels width appears to be equal or under 0.5 mm. Finally, it is demonstrated that optimal conversion occurs when around 1/3 of the catalytic bed is covered with metallic conductive fins. Over this value, increased conductivity gains are overpassed by the lowering of catalyst volume within the conduction chamber.
Copyright (c) 2025 Jean-Francois, Emeric Désilets, Nicolas Brissette, Nadi Braidy, Luc Frechette, Mathieu Picard https://creativecommons.org/licenses/by/4.0
High Concentration Optical System for Solar Fuel Production via Cerium Oxide Thermochemical Cycle
The integration of solar energy into hydrogen fuel production marks a key step towards sustainable energy. This study, which is part of a Marie Skłodowska-Curie Action called “TOPCSP”, aims to optimize the design of a concentrated solar power system tailored for high-temperature applications such as thermochemical cycles for hydrogen production. The system features a point-focus tower with compound parabolic concentrators as secondary concentrator to maximize solar radiation capture and to minimize receiver thermal losses, enhancing the efficiency of the solar-to-fuel conversion. Hydrogen is produced through a two-step thermochemical cycle using non-stoichiometric ceria, designed for high efficiency and scalability. Through theoretical modeling and simulations, this work presents an optimal optical configuration that boosts hydrogen production rates and reduces overall system costs.
Copyright (c) 2025 Alejandro González Silvestre, Gioele di Marcoberardino, Marco Binotti https://creativecommons.org/licenses/by/4.0
Waste Biomass Fast Pyrolysis in a Drop-Tube Reactor Using Concentrated Solar Power
Solar-assisted pyrolysis is a sustainable process for the conversion of biomass into bio-oil using renewable solar-thermal energy with potentially zero carbon footprint. The EU’s target of reducing net greenhouse gas emissions to at least 55% by 2030 leads the way to effective measures in limiting carbon emissions for a climate-neutral future. This study focuses on the initial design and development of a drop-tube fast pyrolysis reactor that performs the conversion of waste biomasses into bio-oil at 600°C, by using concentrated solar power. This work is part of the European Union-funded project, Circular Fuels, which focuses on the production of sustainable aviation fuels (SAFs). The numerical CFD simulations were performed using the ANSYS FLUENT 2020 commercial CFD solver for the sizing and design optimization of the experimental solar reactor prototype.
Copyright (c) 2025 Vignesvar Krish Subramani, Sylvain Rodat, Stéphane Abanades https://creativecommons.org/licenses/by/4.0
Technoeconomic Analysis of a Solar Thermochemical Fuel Production Process Using a Packed-Bed Redox Reactor
The production of synthetic liquid fuels at a competitive price is paramount to deploy them at scale in sectors such as the aviation and maritime industries. Solar thermochemical fuel production is a promising pathway to produce such fuels using concentrated solar thermal (CST) driving high-temperature redox reactions, coupled with a gas-to-liquid process. In this work we present a preliminary technoeconomic analysis of a solar fuels plant, utilizing a new fixed-bed countercurrent redox reactor and combining both CST and photovoltaic arrays to supply the required energy. Three case studies are examined: CST-PV hybrid, CST-PV hybrid with energy conversion between heat and electricity, and CST. All cases include a power block that utilizes the exothermic heat of oxidation. A TEA framework, based on reduced order modelling of the redox reactor, is used to correlate design and operating conditions to syngas production rate. Preliminary analysis shows that commercial viability is unattainable for reduction temperatures up to 1500°C, attributable to the low feedstock conversion. When increasing the reduction temperature to 1600°C, levelized costs of hydrocarbon feedstock below $10/gal are attainable. CST-PV hybrid with energy conversion is identified as the most promising configuration between the three configurations examined in this work. While calculated fuel costs are still much higher than those of fossil-based hydrocarbon fuels, several directions are identified that can improve their commercial viability, namely inclusion of thermal energy storage, increasing the overall plant scale, and further optimization of the CST and PV subsystems.
Copyright (c) 2025 Alon Lidor, Zachary Hart, Janna Martinek https://creativecommons.org/licenses/by/4.0
Development of a Concentrating Optics System for a Photoelectrochemical Hydrogen Reactor
Green hydrogen is expected to play a crucial role in achieving net-zero carbon emissions. By supporting the development of photoelectrochemical (PEC) hydrogen production, the technology’s advantages in terms of scalability, low-cost materials, and reduced transmission losses can be utilised. This study presents the design, construction and characterisation of concentrating optics for on-sun testing with a PEC reactor. The optical design incorporates refractive primary optics (linear Fresnel lenses) and reflective secondary optics (stepped lightguide) to produce a scalable line-concentrating system. Ray tracing simulations predicted an optical concentration ratio (OCR) and optical efficiency of 12.5 and 51.3%, respectively. However, experimental testing revealed lower performance, with maximum OCR and optical efficiency of 5.8 and 23.8%, respectively. The greatest contributor to the discrepancy is found to be heightened stray losses in the demonstrated system. The results highlight the importance of precise manufacturing to reliably produce superior optical performance. Despite high losses and sensitivity to misalignment, the optics were successfully coupled with the PEC reactor to produce hydrogen in subsequent on-sun tests, the results contributing to an extended study investigating the up scaling of PEC reactor technology.
Copyright (c) 2025 Arend Moelich, George Creasey, John Willman Rodriguez-Acosta, Anna Hankin, Craig McGregor https://creativecommons.org/licenses/by/4.0
Continuous Solar Hydrogen and Syngas Production in Membrane Reactors
Satisfying the industry's growing demand for sustainable hydrogen requires the rapid development of a diverse mix of hydrogen production technologies. The membrane technology is capable of shifting the thermodynamic limits of water splitting to lower temperatures and thus into a technically feasible range. This thermodynamic limit was determined with respect to possible molar flow parameters and temperature, where biomethane is considered as reducing agent on the permeate side of the membrane or a purge gas dilutes the permeated oxygen concentration. In the second part of this study, a developed thermal model is used to analyse the integration of real solar flux distribution into a membrane stack reactor. To avoid failure of the joined membrane modules, a homogeneous temperature distribution (< 50K) along the reactor body is required. However, the solar flux distribution from a solar system is characterised by a Gaussian-shape with a peak in its centre, which results in the generation of hot spots. Our model consists of a cavity, the reactor and a set of plates, which are used to enhance the temperature distribution in the reactor. It was found that parameters such as the aperture diameter of the cavity, the distance of the cavity to the focal point and the material of the irradiated plates influence the temperature distribution on the reactor stack. An aperture diameter of 55 mm and a distance of 135 mm to the focal point met the temperature requirements of the membrane stack reactor.
Copyright (c) 2025 Nicole Neumann, Juan Pablo Rincon Duarte, Martin Roeb https://creativecommons.org/licenses/by/4.0
Simplified Thermal Analysis of a Concentrated Solar Water-Splitting Photocatalytic System
Photocatalytic water-splitting (PWS) technologies that produce hydrogen are approaching the necessary efficiencies to become a cost competitive alternative to traditional electrolysis. Continuous advancements in the solar-to-hydrogen (STH) efficiencies of PWS materials can be seen globally. This work presents a theoretical investigation into understanding the thermal behavior of a PWS system under concentrated light conditions. Ordinary differential equations (ODEs) were used to theoretically simulate experimental conditions. A python-based code solved the ODEs, the simulated results successfully matched the experimental results reaching an equilibrium temperature of 74.4 °C, which is within the experimental temperature range of 75 °C ± 3 °C reported in literature. The implementation of a simplified thermal model enabled initial analysis of this system. The current model provided a useful tool for assessing various conditions and observing system behavior in a timely manner which can feed into future design decisions of PWS systems.
Copyright (c) 2025 Anthony Pellicone, Patrick Tapping, Woei Saw, Greg Metha https://creativecommons.org/licenses/by/4.0
Volumetric Absorption of Direct and Indirect Radiation in Porous Redox Structures for Solar Fuel Production
In order to reduce the dependency on fossil fuels and thereby the emission of greenhouse gases, the large-scale production of renewable chemical energy carriers plays an important role. Here, the production of green hydrogen via solar thermochemical redox cycles presents a promising pathway. In order to develop and improve reactor concepts that utilize this approach, the usage of numerical models is essential. The volumetric radiation absorption within porous redox structures is often simplified or neglected within such models. Furthermore, the setup of redox structure and radiation source is often limited to the direct collimated irradiation of flat structures. Therefore, a Monte-Carlo ray-tracing model is developed to simulate the volumetric radiation absorption within porous redox structures of different geometries and reactor boundary conditions. In addition to the direct irradiation of a flat geometry with collimated solar radiation, the indirect diffuse irradiation of a cylindrical redox structure is evaluated. The model setup and resulting absorption profiles are presented here and will serve as an input to material models for heat transfer simulations.
Copyright (c) 2025 Louis Thomas, Stefan Brendelberger, Robin Tim Broeske, Martin Roeb, Christian Sattler https://creativecommons.org/licenses/by/4.0
Two-Step Thermochemical Conversion of CO2 Using a Novel Nd1-xSrxMnO3 Perovskite
A two-step thermochemical splitting process of doped and undoped neodymium-based manganite perovskites was investigated using thermogravimetric analysis. The samples were synthesized using a modified Pechini method and characterized by XRD, SEM and EDS analysis before redox testing. The results showed that 40% Sr-doped Nd0.6Sr0.4MnO3 outperformed the other samples, achieving 103.7 µmol-O2/g during thermal reduction and 189.2 µmol-CO/g during thermal oxidation, with a re-oxidation yield of 91.2%.
Copyright (c) 2026 Muhammad Usman, Giovanni Palmisano, Georgios Karanikolos, Stéphane Abanades, Khalid Al-Ali https://creativecommons.org/licenses/by/4.0
Designing and Testing of a High-Temperature Parti-cle Lift for Concentrating Solar Power Applications
The use of solid particles in concentrated solar power (CSP) technologies enables operation at elevated temperatures (approximately 1000°C), resulting in improved thermal efficiencies and reduced costs for CSP applications. However, achieving high-temperature operation in particle-based systems presents significant challenges, as all key components must be rigorously evaluated under elevated temperature conditions. In a particle-based CSP system, a substantial amount of heat loss occurs during the handling of particles. Furthermore, as the system's capacity increases, the height of the tower also rises, leading to prolonged travel times for the particles and consequently greater heat loss. King Saud University and Sandia National Laboratories are collaborating on the design, testing, and risk mitigation of a cost-effective particle lift system (PLS) suitable for high-temperature applications. This paper outlines the design basis, sizing methodology, scaling considerations, and ground testing of two different PLS scales.
Copyright (c) 2026 Shaker Alaqel, Nader Saleh, Nathan Schroeder, Hany Alansary, Jeremy Sment, Felicia Brimigion https://creativecommons.org/licenses/by/4.0
Designing an Integrated CSP-SOE System for Hydrogen Production
This paper presents the design, and simulation of a novel concentrated solar power (CSP) system integration with solid oxide electrolysis (SOE) to generate superheated steam required for efficient hydrogen production. The system comprises of 10 parabolic dish collectors, SiSiC cavity receivers, and a heat exchanger with two components. An evaporator and a superheater collectively achieve a high thermal efficiency of 73%. Computational fluid dynamics (CFD) simulations demonstrated that the SiSiC receiver can maintain an air outlet temperature of 1555K, which is 8% more efficient than a similar design reported in the literature. This would facilitate the generation of superheated steam necessary for the SOE process. A water flow rate of 28.8kg/h directly influences the system's hydrogen production capacity, which reaches 2.56kg/h at optimal conditions. The heat exchanger components were designed using Aspen EDR, while the entire system simulation was conducted using Aspen Plus, demonstrating the system's potential to meet industrial standards for sustainable hydrogen production. This article serves as a good reference in investigating the feasibility of CSP-SOE systems as a promising pathway for large-scale renewable hydrogen production.
Copyright (c) 2025 Abdullah Ayed Alrwili, Khalifa Aliyu Ibrahim, Peter King, Ahmed Ali Aldubayyan, Yousef Lafi A Alshammari, Zhenhua Luo https://creativecommons.org/licenses/by/4.0
CST4ALL - Support to the Activities of the Concentrated Solar Thermal Technology Area of the SET Plan
The Concentrated Solar Thermal Technologies (CST) sector has struggled with high-costs associated with Concentrated Solar Power (CSP) plants in Europe over the past decade. Moreover, CSP has largely been viewed only as a flexibility provider for electricity systems. To address these challenges, the CST4ALL project promotes a range of hybridization and cooperation initiatives at the intersection of CST and other renewable energy technologies, drawing on the work of various European Technology & Innovation Platforms (ETIPs). CST4ALL aligns closely with current EU priorities- such as Smart Sector Integration, Fit for 55, and Clean Energy Transition Partnership (CETP)-as well as national energy strategies. It seeks to offer solutions to pressing issues related to decarbonisation and energy security. The key outcome is a series of workshops engaging both industry and research and development (R&D) communities, fostering interaction among stakeholders at key technology interfaces with the CST sector. By analysing both industrial and R&D perspectives, CST4ALL aims to expand the network of active stakeholders in the CST Implementation Working Group (IWG) under the SET Plan and to raise awareness of CST’s potential role in sustainable energy mix. This paper outlines the project’s main activities to support the European Commission’s cross sector approach – encouraging public and private investment in R&D and establishing the political and regulatory framework needed to implement the new CST Implementation Plan (IP) from October 2022 to March 2024.
Copyright (c) 2025 Yelda Erden Topal, Hande Eryılmaz, Derek Baker, Konstantinos Genikomsakis, Peter Heller, Daniel Benitez, Julian Blanco Galves, Ricardo Sanchez, Luca Turchetti, Simona De Iuliis, Alperen Gunay https://creativecommons.org/licenses/by/4.0
From Global to Local: Learning from Worldwide CSP Successes to Drive Chile’s Solar Power Industry Forward
Concentrated Solar Power (CSP) technology offers a promising solution for enhancing the stability and reliability of renewable energy systems, particularly in regions with high solar resource availability like Chile. However, CSP deployment faces significant challenges, including technological mistrust, high costs, and regulatory barriers that hinder its growth. This study provides an in-depth analysis of global CSP successes and identifies key strategies and challenges relevant to Chile's context through a mixed-methods approach, including a comprehensive literature review and stakeholder interviews with key players in the Chilean CSP industry. The results reveal significant technological, regulatory, and financial barriers to CSP deployment, including issues with thermal energy storage (TES) systems, specifically the failures of molten salt tanks. Despite recent declines in CSP capital expenditures and the potential for further cost reductions, the study highlights the critical need for regulatory reforms and tailored policy support to address current market and technological limitations. Key recommendations include enhancing R&D investments to improve TES reliability, streamlining permitting processes, and fostering public-private partnerships to unlock CSP's full potential. The findings underscore the necessity of strategic incentives and business model innovations to enable the commercial-scale deployment of CSP in Chile, ultimately supporting the country's decarbonization goals and strengthening energy security.
Copyright (c) 2025 Carlos Felbol, Francisco Moraga, María Teresa Cerda, Frank Dinter https://creativecommons.org/licenses/by/4.0
Central Receiver-Based CSP Plants: Trends and Categorization
Central receiver-based concentrated solar power (CSP) systems play a crucial role in solar energy technology, particularly for their ability to operate at higher temperatures than conventional linear concentrators, and for better integration of thermal energy storage in a more direct manner. This paper methodically examines the development and classification of central receiver-based CSP technologies, including power towers, solar furnaces, and beam-down configurations. It aims to emphasize the operational advantages and challenges of these technologies through a literature review. Through an in-depth examination of strategic pathways, including hybridization and co-location, this study reveals critical trends in market deployment frameworks, underpinning the future of CSP integration in the transition to renewable energy solutions.
Hydrogen Production Through Renewable Energies in Areas of High Irradiation Conditions
This study evaluates the operation of a Proton Exchange Membrane (PEM) electrolyzer and an Alkaline Water Electrolyzer (AWE), coupled with Concentrated Solar Power (CSP), Photovoltaic (PV), and Wind Turbine (WT) power plants in a region characterized by high solar irradiance and moderate wind speeds. Each technology is modeled and integrated into fourteen different configurations, seven of which are coupled with a PEM electrolyzer, and the remaining seven with an AWE electrolyzer. Hourly simulations are conducted for one year to determine annual hourly production. Subsequently, the Levelized Cost of Electricity (LCOE) and the Levelized Cost of Hydrogen (LCOH) are calculated for two scenarios: the current state and projections for 2030. Results indicate that the LCOE ranges from 48.19 to 118.18 USD/MWh, while the LCOH varies from 3.56 to 14.13 USD/kg H2. By 2030, these values are projected to decrease to between 38.57 and 87.99 USD/MWh for LCOE and between 2.87 and 8.22 USD/kg H2 for LCOH. However, these LCOH values are still higher than those for grey hydrogen derived from fossil fuels. If reductions in LCOE and electrolyzer investment costs are achieved, green hydrogen could become more cost-competitive. These findings provide critical insights for policymakers considering strategies for green hydrogen production.
Copyright (c) 2025 Roberto Leiva-Illanes, German Amador, Alvaro Cespedes, Cynthia Herrera https://creativecommons.org/licenses/by/4.0
Materials Comparison for Reducing Heliostats Production Costs
The alarming issue of climate change and the necessity to increase the renewable energy stake has become the driving force for cost reduction measures taken in various renewable technologies. Concentrated Solar Power (CSP) is an increasingly attractive solar energy technology that uses heliostats to provide controllable, rapid heating and thermal energy storage (TES) benefits, which can use high temperature fluids (HTF) for higher efficiencies. The cost of installation for a commercial heliostat assuming a production volume of 22,239 heliostats, which represents a solar field aperture area of 1,078,592 m2, is $127/m2, or 136.98 million for the solar field [1]. Around 31% of the cost comes from manufactured parts which include the heavy use of steel, which can be subject to high price volatility, to ensure structural stability under wind load conditions. By studying the structural vibration response for different types of composite materials, a case can be made to switch from the heavy use of galvanized steel to a hybrid or even complete use of composite materials for heliostat construction. This paper presents a structural vibration response comparison between Steel AISI 1020, Glass Fiber Reinforced Polymer (S-Glass and E-Glass), Basalt Fiber Reinforced Polymer, and Carbon Fiber Reinforced Polymer (230, 290, and 395 GPa.) for heliostats structure manufacturing.
Copyright (c) 2025 Javier Martell, Kenneth Armijo, Dimitri Madden https://creativecommons.org/licenses/by/4.0
Expanding the Western U.S. Grid With CSP
As states within the United States respond to future grid development goals, there is a growing demand for reliable and resilient nighttime generation that can be addressed by low-cost, long-duration energy storage solutions. This paper summarizes the findings of a study for the state of California that evaluated how molten-salt tower concentrating solar power (CSP) plants with thermal energy storage (TES) can be utilized to address the goals within the state established by Senate Bill 100. The study found that CSP exhibits deployment potential both in California and in the rest of the Western Interconnection and is utilized primarily to serve nighttime load. The plants are designed to collect and store energy during the day and then are dispatched to produce power at night. The paper presents a technoeconomic analysis that compares the cost of CSP to photovoltaics (PV) plus battery energy storage systems (BESS), provides an overview of capacity expansion modeling performed by NREL, and a screening analysis that identifies CSP siting potential in the U.S.
Copyright (c) 2025 Henry Price, Kyle Kattke, Keith Boyle, Devon Price, Ryan Shininger, Frederick Morse, Alexander Zolan, Sarah Awara, Chad Augustine, Xavier Lara https://creativecommons.org/licenses/by/4.0
Demonstration of a Proof-of-Concept Integrated Skip Hoist-Thermal Energy Storage System
This paper presents the design, construction, and preliminary testing of an innovative skip-hoist particle lift (PL) integrated with a multi-layered cylindrical thermal energy storage (TES) system for particle-based concentrated solar power (CSP) applications. The skip-hoist PL, constructed with stainless steel for high-temperature compatibility, was seamlessly integrated with two TES bins on a 22-m concrete tower. Preliminary testing at ambient temperature confirmed the system’s operational feasibility, paving the way for high-temperature testing and the proposed 1.3 MWe pre-commercial scale-up in Waad Al-Shamal, Saudi Arabia.
Copyright (c) 2025 Nader Saleh, Shaker Alaqel , Eldwin Djajadiwinata , Rageh Saeed , Hany Al-Ansary , Zeyad Al-Suhaibani , Abdelrahman El-Leathy, Syed Danish, Sheldon Jeter https://creativecommons.org/licenses/by/4.0
Current Progress of Activities at EU-SOLARIS ERIC: The European Research Infrastructure Consortium for CSP Technologies
An ERIC, established by a decision of the European Commission, is a legal entity possessing legal personality and full legal capacity acknowledged across all EU Member States. Its primary role is to establish and operate a research infrastructure on a non-economic basis. Under the initiative of Spain, France, Germany, and Cyprus as Members, with Portugal as an Observer, a European Research Infrastructure Consortium (ERIC) has been formed. This consortium, named "European Solar Research Infrastructure for Concentrated Solar Power" (EU-SOLARIS ERIC) is established in accordance with Council Regulation (EC) No. 723/2009 of 25 June 2009. The establishment of an ERIC was sanctioned by the European Commission, as evidenced in Commission Implementing Decision (EU) 2022/2297 of 19 October 2022 [1]. The inaugural assembly of the EU-SOLARIS ERIC took place at the CIEMAT Headquarters in Madrid on 12th January 2023. During this gathering, the General Assembly was officially convened, and the Statutes along with other governing documents were formally endorsed. At the time of composing this document, negotiations for the accession of three additional countries—Greece, Turkey, and Italy—are underway. This paper summarizes the R&D activities carried out during this first year of the ERIC, particularly, we describe the new projects achieved.
Copyright (c) 2025 Ricardo Sánchez, Julián Blanco, Emmanuel Guillot, Gilles Flamant, Manuel Blanco, Daniel Benitez, Marios Georgiou, Nestor Fylaktos, Joao Cardoso, Diogo Canavarro, José Martín, Diego Martinez https://creativecommons.org/licenses/by/4.0
NEWS4CSP Project – New Coatings Approaches to Protect Metallic Materials From Heat Transfer Fluids
The efficiency of Concentrated Solar Power technologies increases with the operation temperature of the power block, which can be achieved using advanced power cycles operating at temperatures ≥650°C. Molten Salt (MS) based HTF have been facing critical challenging issues of severe corrosion and lower specific heat capacity. This paper aims to present the NEWS4CSP project to the CSP scientific community, highlighting the main concepts being pursued and the preliminary results obtained regarding the application of new coatings to increase the anticorrosive protection of structural materials in contact with MS. Two different types of powder coatings (nickel and cobalt alloys) were applied to AISI 430 stainless steel using two coating technologies: High Velocity Oxy-Fuel (HVOF) and Laser Cladding (LC). LC proved to be the most suitable technique of these two coating application technologies. The Co-Cr coating alloy showed good anticorrosive behaviour even after 3000 h of testing. The obtained results are very promising, nevertheless, more studies are needed to optimise its application by LC. These include optimizing the thickness and chemical composition, as well as gaining a deeper understanding of the degradation mechanisms and whether this behaviour is maintained over longer periods.
Copyright (c) 2025 Teresa C. Diamantino, Fátima Pedrosa, Teresa Paiva, Eduardo Silva, Francisco Gonçalves, Renato Monteiro, João P. Cardoso https://creativecommons.org/licenses/by/4.0
SolPOC: A Python Package for Modelling the Optical Coating Used in Solar Thermal Energy Systems
Solar collectors of all types (thermal or photovoltaic, with or without concentration) require one or more surface treatments during their solar radiation conversion. These treatments are made up of thin layers of materials stacked that constitute mirrors, glass panes, thermal absorbers, or cover the junctions of PV cells. To allow all stakeholders in the solar community to easily model the optical behavior of their thin layer stacks we propose our in-house code. SolPOC (Solar Performances Optimization Code) is a Python Package specifically designed to provide a better understanding of coatings, thin film deposition of materials for solar energy applica-tions and especially for Solar Thermal Energy Systems. The package includes a stable and fast method to calculate the spectral reflectivity, transmissivity, and absorptivity of a stack of thin films over the full solar spectrum and maximize the solar performance of the stack by op-timizing its characteristics. SolPOC comes with several optimization methods, a script using multiprocessing pool tools, and a comprehensive database of refractive indices of real materi-als. The code has already produced major scientific advances in research on coatings for solar thermal systems. It is simple to use for non-coder users, automatically saves important results and is freely available on GitHub with a complete documentation and tutorials.
Copyright (c) 2025 Antoine Grosjean, Pauline Bennet , Thalita Drumond, Amine Mahammou, Denis Langevin, Antoine Moreau, Audrey Soum-Glaude https://creativecommons.org/licenses/by/4.0
Enhancement of Compressive Strength of Perovskite Foams Used for Thermochemical Energy Storage
Reticulated Porous Ceramics (RPCs), also known as ceramic foams are widely investigated for applications in Concentrated Solar Energy (CSE) harvesting, transformation, and storage. However, their inherent shape-related advantages - such as high gas-solid contact area and accommodation of high gas flow rates combined with low pressure drop due to their “open”, thin-struts-structure - are accompanied by low mechanical strength, which hinders large-scale, on-field applications. Foams prepared by the replica method - i.e. via impregnation of “sacrificial” polyurethane (PU) foam templates - exhibit hollow struts of about 100 µm thickness, which limit further their mechanical properties. In this work, an infiltration technique is presented that fills the hollow struts and substantially increases the mechanical strength of such RPC foam structures made of Ca0.9Sr0.1MnO3 (CS10MO), a perovskite composition already identified as very promising for thermochemical storage of CSE. The developed infiltration technique achieves high degrees of infiltration and leads to a substantial increase of mechanical strength, specifically a 217% increase in withstandable compressive stress, from 0.23 MPa to 0.50 MPa. The results show that infiltration of hollow RPC foams can drastically increase the mechanical strength of prepared foam samples, not only making the open porous components for thermal storage devices more rigid and stable, but also increasing the envelope density by adding weight to the component within the same volume. Thereby, the applied infiltration simultaneously increases stability and volumetric storage density of a storage unit that utilizes such open porous foams.
Copyright (c) 2025 Mathias Pein, Asmaa Eltayeb, Artur Lang, Christos Agrafiotis, Martin Roeb https://creativecommons.org/licenses/by/4.0
Selection of Glass Alternative Materials for Manufacturing Heliostat Reflective Facets
Traditional concentrating solar power plants utilize silvered glass reflective facets that account for a significant portion of the total plant cost. Several cost-effective non-glass reflectors have been developed. A majority of these novel reflectors are flexible, which necessitates exploring support structures to maintain their shape during use. This study presents a methodology for evaluating and selecting structural support materials for non-glass heliostat facets. The approach employs analytical models to efficiently screen a large pool of candidate materials based on strength, stiffness, and deflection due to gravity, using an existing glass reflector panel as a reference. During analysis, sandwich panels showed promise as viable support for the reflector. The most promising sandwich panel designs are further investigated using experimental testing. The analytical model predictions are found to align moderately well with physical test results, validating its utility for rapid material selection. The top-performing sandwich panel designs demonstrate the potential for cost savings and increased facet size compared to traditional glass facets. This research provides a framework for evaluating and selecting structural materials for non-glass heliostat facets, enabling improved cost-effectiveness and performance of concentrating solar power systems.
Copyright (c) 2025 Jean Schnaar-Campbell, Craig McGregor, Johann Bredell https://creativecommons.org/licenses/by/4.0
Soiling Measurement Characterisation System Over a PV Solar Field in the Southern Spain
Soiling is one of the main problems that cause power losses in photovoltaic plants. This article presents a method to determine dirt in a photovoltaic plant using three digital cameras and analyzing the average (Red, Green and Blue) RGB values obtained from each of them. The study also incorporates inclined, global, direct and diffuse irradiance data, as well as suspended particle data PM10, PM2.5 and PM1, where the number indicates the size of the particle in µm. In this investigation, three digital cameras were strategically placed to capture images of the panels at regular intervals. From these images, average RGB values ​​were calculated to quantify the level of dirt on the panels. These values ​​were correlated with solar radiation data, the photovoltaic power of the plant and the concentrations of suspended particles. The results demonstrate that analysis of mean RGB values ​​provides a reliable and non-intrusive method for monitoring fouling in PV plants, contributing to more efficient maintenance strategies and an increase in energy production.
Copyright (c) 2026 Joaquín Alonso-Montesinos, Enrique García-Campos, Andrés García-Rodríguez, Verónica Abad-Alcaraz, M. Mar Castilla, Manuel Pérez, José Antonio Carballo, Domingo Álvarez-Hervás https://creativecommons.org/licenses/by/4.0
Advanced Molten Halide Salt Valves Operation Demonstration
To ensure confident molten salt flow operations within Generation 2 concentrating solar power (CSP) and other advanced >700°C molten salt-based power systems, for Gen 3 CSP and Gen 4 Nuclear Energy (NE), an advanced flow control valve is required. This paper investigates development of two molten salt flow control valves (FCV) for operational demonstration of bellows-style and quick-change packing designs. This innovative high-temperature molten salt valve, with nominal operation at 750°C and 11 bar has been demonstrated using FLiNaK and a ternary chloride molten salt. This work details the general design and flow testing of a bellows-seal FCV. This design includes an integrated closed-loop thermal control system to ensure robust design for freeze-thaw cycles. The design of both valves includes advanced thermal management with ceramic fiber (CF) heaters as well as a novel heat pipe valve stem. This investigation details the development of two high-temperature molten salt test systems that tested these valves up to 750°C and at 11 bar operational pressure. The valve test performed within the Flowserve Corp. Villach test loop employed a DOE Gen 3 CSP (20%NaCl/40%MgCl2/40%KCl by mol. wt. %) ternary chloride salt, while the Kairos Power Isothermal batch test system used FLiNaK (LiF-NaF-KF) as the salt chemistry. The results indicated nominal operation for the two valve systems without the heat pipes at 750°C though with the inclusion of the novel valve stem incorporating these, the temperature gradient along the bonnet was reduced by as much as 210°C, to improve thermal management performance and operational reliability.
Copyright (c) 2025 Kenneth Armijo, Aaron Overacker, Dimitri Madden, Jeffrey Parish, Michael Nelson, Ivica Radman, Kyle Brumback, Alan Kruizenga https://creativecommons.org/licenses/by/4.0
Exergy-Based Crossover Salt Tank Protection
In recent decades, renewable energy's share in global energy production has grown, with ambitious goals set for the green transition. Concentrating Solar Power (CSP) is crucial in this shift due to its energy storage and on-demand delivery capabilities, which prevent competition with intermittent sources like wind and photovoltaic (PV) systems. CSP enhances grid stability by providing energy during low production times and storing excess energy as heat. This stored heat, at high temperatures up to 550°C, can be used in industrial processes, including green fuel synthesis. The key components in CSP systems are the salt tanks, which are vulnerable to issues like corrosion, thermal shock, and thermal deformation, as seen in several projects worldwide. These issues are often due to temperature gradients in the tanks, which can cause buckling and fatigue rupture. The study focuses on strategies to minimize these risks, particularly through innovations in Vast's CSP v3.0 design. This includes a modular solar field arrangement to reduce temperature peaks and drops, active control of molten salt flow to match heat carrier fluid (HTF) temperatures, and a robust heat exchanger to buffer temperature changes. An innovative algorithm in the valve system at the molten salt tank inlets further enhances safety by directing hot salt to appropriate destinations, addressing the temperature differential issue that could reduce the equipment lifespan. This study, based on a numerical model of the entire plant and real weather data, tested various configurations to optimize the salt tanks' working conditions.
Copyright (c) 2025 Fabio Aste, Kurt Drewes https://creativecommons.org/licenses/by/4.0
Maintenance Optimization of Parabolic Trough Power Plants Through a Lifetime Simulation Model Validated With Five-Years of Operational Data
Modelling and Simulation of Concentrated Solar Power (CSP) plants is a crucial requirement for future growth and improvement of the technology. In this paper, the development of a functional and reliable model of a Parabolic Trough Collector (PTC) power plant is presented and validated with existing five-year operational data of a 50 MWel plant equipped with seven hours full load thermal storage, located in Spain. A mean absolute error of 2.53% between the simulation and plant data was found when considering net energy generated over the five-year period. Subsequently, an optimized maintenance plan is proposed, and the plant behavior is forecasted. The new maintenance strategy is developed to optimize the mirrors current cleaning schedule, thereby mitigating significant detrimental soiling effects on the optical efficiency while reducing water and fuel consumption. Results show an increase in solar gain by 0.46% and reductions in water usage and fuel consumption by 22.1% and 22.3%, respectively.
Copyright (c) 2025 Sayra Gomez Garcia, Shahab Rohani, Nicholas Chandler, Peter Schöttl, Thomas Kraft, Gregor Bern https://creativecommons.org/licenses/by/4.0
Advancements in Failure Analysis Techniques for Concentrated Solar Power Systems
The reliability of Concentrated Solar Power (CSP) systems is important for continuous energy production due to the extreme environmental and operational conditions they work under. This paper offers a mini review of the latest advancements in failure analysis methods for CSP systems. This paper investigates the main causes of failure that threaten the efficiency and durability of CSP components, such as optical degradation, thermal stress, and fluid degradation. The review highlights important progress in diagnostic and monitoring methods such as thermographic imaging, reflectivity measurement, and fluid characterization, which are essential to identify and prevent these failures. Moreover, this review explores and discuss the use of predictive modelling for proactive maintenance and real-time monitoring of CSP systems. These advancements do not enhance only the predictive maintenance capabilities but also allow to improve the efficiency and durability of CSP plants.
Copyright (c) 2025 Mohamed Guerguer, Sanae Naamane https://creativecommons.org/licenses/by/4.0
Salt Tank Testbed: a Test Site Designed to Replicate Floor Buckles Observed in Commercial TES Tanks
A test site has been designed and is under construction to replicate the buckling failure observed in several in-service storage tanks for nitrate salts operating up to 565°C. In commercial tanks multiple factors have been identified that influence the floors susceptibility to buckling, including: the as-manufactured shape of the floor, high compressive stresses due to thermal gradients and/or friction, fluid inventory and absolute temperature. Based on extensive modeling analysis it was determined that similar buckles can be reproduced in a scaled test tank (approximately 9x smaller than a representative commercial tank design). To buckle the scaled tank a radial thermal gradient is generated in the tank with a low fluid level, the fluid level is then increased while maintaining the thermal gradient; based on the modeling results just one of these cycles can plastically deform the tank floor. The test site which is under con-struction is designed to replicate this damaging cycle at lower temperatures. The goal of test-ing will be to reproduce this damaging cycle and buckle the scaled test tank floor, allowing proper model validation and a methodology for comparing different tank designs at a smaller (and less costly) scale.
Copyright (c) 2025 Luca Imponenti, Nathan Stegall, Bruce Kelly, Hank Price, David Cubel, Sergio Davilla, Ricard Fernandez, Kevin Vila, David Andrews, Bruce Leslie, Kurt Drewes https://creativecommons.org/licenses/by/4.0
Controller Tests for Molten Salt Parabolic Trough Systems with Loop-Wise Control Valves
Concentrated Solar Power systems are used to generate thermal and electrical energy from solar radiation. Molten salt as a heat transfer medium offers the possibility of a higher temperature in the solar field and at the same time the use of direct energy storage. The Évora Molten Salt Platform is a research platform to study molten salt in the solar field on a pre-commercial scale [1]. The use of molten salt requires to adapt control concepts used in thermal oil fields since the temperature rise over the loop and the loop length are different from those of thermal oil. One approach is to use automatic valves in each loop to individually control the temperature at the outlet of each loop. This paper presents controller tests performed at the HPS2 molten salt loop of the Évora Molten Salt Platform for normal operation and start-up mode that provide the basis for an individual loop flow control strategy.
Copyright (c) 2025 Tim Kotzab, Niklas Dicke, Michael Wittmann, Mirko Meyer-Grünefeldt, Jana Stengler, Paula Martins, Pedro Horta, Tobias Hirsch https://creativecommons.org/licenses/by/4.0
Geometric Characterization of Flexible Film Mirrors Parabolic Trough Collectors by 3D Scanning and Receiver Tube Image Analysis
This study presents a methodology for geometrically characterizing the parabolic trough collectors (PTCs) shapes at the Porto Primavera Thermosolar Power Plant (UTPP), located in Brazil, using 3D scanning. The theoretical parabolic profile of the PTCs was compared to the profile obtained from the scanning point cloud, where the deviations identified were presented using a color scale on a 3D map of the solar field. In addition, two point clouds obtained 18 months apart were superimposed to identify changes in the PTCs. The results showed that the northern ends of some PTCs underwent geometric changes, which were attributed to the prevailing winds in the deformed region. In addition, an analysis of the image of the receiving tube on the mirrors was carried, where long-distance photos were taken from in front of the PTCs using a drone to compare the reflection pattern of the receiver tube and identify changes after 18 months of operation that could reduce the ability of the PTCs to direct the sun's rays onto the receiver tubes. The results showed that there were no significant changes in the reflection pattern. Both the 3D scanning and receiver tube image analysis are valuable for geometric characterization and monitoring of large solar fields.
Copyright (c) 2025 Nelson Ponce Junior, Jonas R. Gazoli, Roberto M. G. Velasquez, Osvaldo J. de Souza, Alan R. Nunes https://creativecommons.org/licenses/by/4.0
Real-Time Image Enhanced Data-Driven Digital Twin (Real-TImE 3DT) for Flux Density Measurements
Concentrated solar power (CSP) plants are considered one of the most attractive renewable energy producers (used for green fuel and electric power). Consequently, it is essential to enhance the different elements of their power cycles, especially the central receiver and the heliostat field. To achieve this, flux density measurement (FDM) is highly recommended. In this work, a novel methodology for FDM is presented, based on the usage of real-time data-driven simulation models in parallel with the traditional camera methods for the real-time enhancement of the results. In order to improve the output, a graph neural network is used, giving as a result a Real-Time Image-Enhanced Data-Driven Digital Twin (Real-TImE 3DT). All the data are obtained from a pre-existing data platform, where the signals from the sensors of the power plant are logged and stored. This way, it is possible to operate the model manually, or to let it work automatically with these sensors' outputs. Latencies smaller than 10 seconds are achieved and the results from the digital twin showed coherence, easy handling and great inter-operability with the neural network enhancement. On the AI-enhancement’s side, the suppression of up-to 80% of the inaccuracies can be expected under parametrically semi-controlled conditions. Further work is being performed in Solar Tower Jülich (STJ) in order to contrast these results against real experimental measurements.
Copyright (c) 2025 Sergio Díaz Alonso, Christian Raeder, Kai Wieghardt, Bernhard Hoffschmidt https://creativecommons.org/licenses/by/4.0
AI-Based Generative Geometrical Design of Concentrated Solar Thermal Tower Receivers
An artificial intelligence (AI) aided generative design workflow for the optimization of cavity receivers for concentrated solar thermal (CST) energy systems is presented. The workflow integrates the Non-dominated Sorting Genetic Algorithm III (NSGA-III) with generative design methodologies and optical evaluation through Monte-Carlo ray-tracing in an interoperable way, to optically optimize the geometry of cavity receivers according to a set of objective functions for a given heliostat field. As a demonstrator test case, the workflow is used to provide an optimal geometrical design of a cavity receiver given the Cyprus Institute’s PROTEAS heliostat field. It is shown that the workflow is able to generate unconventional, non-intuitive and efficient receiver designs in an automated manner, which are often not conceived by traditional design approaches.
Copyright (c) 2025 Jorge Moreno García-Moreno, Kypros Milidonis, Mihalis Nicolau, Wojciech Lipinksi https://creativecommons.org/licenses/by/4.0
A method for the design of heliostats considering dynamic wind loads is presented. The transient FEM simulation is based on a CAD model of the heliostat and a pressure distribution time series measured in a wind tunnel. In order to minimise the calculation times, a simplified FEM model is used first to determine the period in which the maximum deformations occur. The stresses can then be determined for this period using a more precise model.
Copyright (c) 2025 Justus Blum, Atli Tobiasson Helmer, Andreas Pfahl https://creativecommons.org/licenses/by/4.0
A concept for the automated installation of heliostats for solar tower power plants was developed with the primary objective of reducing installation costs. Following a discussion on the various types of foundations available for installation, the pile foundation was selected on account of its favourable cost per heliostat. The feasibility of this approach was assessed by calculating the wind loads and the structural stability. Vibratory pile driving was selected as the method for driving the pylons into the ground, as it enables the pile driving of very thin-walled pylons with minimal stress on the component. The installation of a heliostat is a two-step process, involving the piling of the pylons and the subsequent fastening of the concentrator with the tracking device. The fastening is facilitated by thin sheet metal screws, which were determined to be the optimal joining method, considering the requirements. In order to facilitate the efficient transportation of the components and the subsequent installation of several thousand heliostats on the solar field, various installation and material flow concepts were developed and evaluated, with particular attention to the resulting installation cost. Consequently, vehicle concepts for the automatic execution of the two process steps and for the material transport were derived and a design proposal is presented: The first is a heavy tracked vehicle for the purpose of pylon piling, and the second is two smaller vehicles for transporting and assembling the concentrators, with tracking devices.
Copyright (c) 2025 Lars Grobelny, Andreas Pfahl https://creativecommons.org/licenses/by/4.0
A Novel Indoor Approach of Artificial Soiling Deposition: Achieving Desired Soil Density and Uniformity
This work introduces a new indoor method for the artificial soiling of solar reflectors, employing a closed-loop wind tunnel chamber to replicate controlled deposition methods in a laboratory setting. The experimental setup includes dispersing a constant dust amount and allows manipulation of deposition to examine the impact of airflow speeds (1, 3, and 4.5 m/s), dust concentration and various humidity levels. The results show significant improvements of artificial soiling deposition, leading to more uniform deposition on the mirror surfaces and allowing a repeatable test.
Copyright (c) 2025 Ashraf Issalih, Peter King, Mounia Karim https://creativecommons.org/licenses/by/4.0
This study addresses the challenge of reducing costs in concentrated solar power (CSP) systems by developing a novel winch-actuated heliostat design. Building upon previous cable-actuated designs, the proposed heliostat utilises steel cables attached to the reflective surface frame, with a worm gear set to decrease torque demands. Through computer-aided design, prototype development, and wind load calculations, the research demonstrates the potential of this design to significantly reduce heliostat costs while maintaining the required tracking accuracy of 1 mrad. This innovation contributes to efforts to achieve the U.S. Department of Energy's 2030 cost target of $ 50/m² for solar fields, potentially advancing the competitiveness of CSP technology.
Copyright (c) 2025 Rorisang Lekholoane, Stephen Clark, Craig McGregor https://creativecommons.org/licenses/by/4.0
Heliostats are the main cost factor of solar tower plants. To optimize them in terms of cost, it is mandatory to estimate the fabrication cost. A method to do so is presented and applied to a sample heliostat. The sample heliostat that is optimized for low production cost is of 2 m² size. The design already provides a low part-count, an efficient material usage and low-cost purchased parts but is also of high accuracy. A part list of the heliostat is created and every part is analyzed. For production cost optimization, the optimal manufacturing process both from a technical and an economical view has to be determined. Furthermore, the material cost has to be estimated based on the weight and material of the heliostat components. Also cost for control and energy supply has to be considered. Optimizing their cost depends significantly on unit quantities. Higher volumes generally translate to lower development costs, yet component and manufacturing expenses become predominant. The circuit board design proves to be a central point here. Selecting easily accessible, interchangeable components suited for function and longevity, optimizes component and manufacturing costs.
Copyright (c) 2025 Daniel Lenski, Moritz Wirger, Andreas Pfahl https://creativecommons.org/licenses/by/4.0
Hall Effect Focus Control System for Vacuum-Membrane Solar Dish Facets
This study investigates the development and implementation of a novel Hall effect focus control system for sensing and maintaining membrane displacement of vacuum-membrane solar dish facets for small-scale concentrating solar power (CSP) systems. Such a CSP system comprises of 46 individual elliptical vacuum-membrane solar-dish facets, each with a variable focal length dependent on the membrane depth. Previous research identified membrane movement as a significant challenge affecting system performance throughout an operating day, due to changing environmental conditions (especially ambient temperature). In response, a cost-effective and low power consumption focus control system utilizing a Hall effect depth sensing method was developed in the current work and mounted to a single facet. Outdoor experimentation on a single facet demonstrated that the control system successfully reduced membrane displacement within an acceptable 0.069 mm/°C accuracy, which is within the required limit of ±2 mm movement for a minimum 90% intercept factor at the solar receiver. Furthermore, by incorporating temperature effects on the Hall effect linear displacement sensor's magnet, a higher accuracy of 0.036 mm/°C was obtained throughout an operating day. These advancements hold promise for enhancing the efficiency and performance of small-scale CSP systems.
Copyright (c) 2025 Duncan Sean McGee, Willem Gabriel le Roux, Evan D. Humphries https://creativecommons.org/licenses/by/4.0
Modeling and Energetic Analysis of a Supercritical Carbon Dioxide sCO2 Recompression-Organic Rankine Cycle Integrated to a Central Tower Receiver
This study presents a comprehensive thermodynamic model and energetic analysis of a hybrid Concentrated Solar Power (CSP) system incorporating a supercritical carbon dioxide (sCO2) Brayton cycle and an Organic Rankine Cycle (ORC). The CSP system uses a central tower receiver with a fluidized bed of silicon carbide particles and air as the heat transfer medium. Operating at a temperature of 650°C, the system demonstrates a heat transfer coefficient of 411 W/m2K. Key findings highlight the sensitivity of the convective coefficient to gas velocity and the effect of particle mass flow on receiver efficiency. Fuel mass flow reductions of up to 3.7% were achieved through particle mass flow adjustments, while variations in compression ratio and steam turbine inlet temperature affected overall cycle performance and efficiency. The study highlights the potential of such integrated systems to improve thermal efficiency, although further optimization is needed to balance fuel consumption and environmental impact.
Copyright (c) 2026 Jesus Alberto Moctezuma-Hernandez, Judit García-Ferrero , Rosa P. Merchan , J.M. Belman-Flores, Sergio Cano-Andrade, J.M.M Roco https://creativecommons.org/licenses/by/4.0
Angular Extent of the Heliostat Field in Solar Tower
In solar tower systems, the mirrors located on the ground reflect and concentrate the solar radiation on the receiver to increase the enthalpy of the heat transfer fluid. The mirrors can be placed surrounding the tower or limited in a direction, based on which the receiver is chosen to be external or cavity type, respectively. The overall performance of the system largely depends on the choice of the arrangement of the mirrors and the choice of the receiver. In this study, the angular extent of the heliostat field around the tower is studied at different latitudes. The field domain is discretized into square grids. The cosine and the attenuation efficiency are evaluated based on the position of the grid element and the aim point. The receiver aperture is idealized to be the outer surface of a cone and is denoted by the tilt angle. The interception efficiency is predicted with the angle made by reflected radiation on the slanted receiver aperture surface. No specific dimension for the heliostat is assumed and the amount of mirror area is expressed with the help of mirror density, which facilitates the prediction of the shading and the blocking efficiency. The amount of mirror area in each discretized field location is optimized for maximizing the optical performance. The results indicate that, with increased latitude in the northern hemisphere, the heliostat field tends to be limited towards the northern direction.