Electricity, Heat and Grid Services - Investigation of Economic Efficiency of Thermal Storage Power Plants

Energy Resilience in Disruptive Times

Abstract

Thermal storage power plants (TSPP), which integrate high-temperature thermal energy storage and a power-to-heat unit into conventional combined cycle gas turbine (CCGT) or coal power plants, offer a promising solution to increase flexibility and reduce fuel consumption in future energy systems with high shares of renewable electricity. This study investigates the economic performance and operational behaviour of TSPP under different market environments. A linear optimisation model is used to analyse plant operation while participating in the electricity spot market, the automatic Frequency Restoration Reserve (aFRR) market and district heating supply. The results show that stacking these revenue streams significantly improves the economic performance of the plant, with the highest profitability achieved when participating in all three markets simultaneously.

The analysis further examines the influence of fuel price variations on system operation. Even at low fuel prices, the TSPP concept shows an economic advantage compared with a conventional CCGT plant. As fuel prices rise, the utilisation of thermal storage increases and electrified heat increasingly substitutes fuel-based heat generation. At fuel prices above approximately €70/MWh, storage-based operation exceeds fuel-based operation, while above €90/MWh gas turbine operation is largely replaced by storage-driven heat supply. These results demonstrate that integrating thermal storage improves economic performance, enables substantial fuel substitution, and increases power plant resilience against fuel price volatility while maintaining security of supply through the gas turbine.