Seasonal Performance of a Photovoltaic Array With Hybrid Battery–Supercapacitor Storage: A Case Study for Botswana

Analysis of Hybrid Energy Storage Performance for Improved Photovoltaic Reliability

Abstract

Durable electrification remains a challenge in Botswana's rural sector, with sparse populations and grid extension costs making decentralised schemes unavoidable. This paper investigates a photovoltaic (PV) array supplying an alternating rural load supplemented with a hybrid battery–supercapacitor energy storage system. A MATLAB/Simulink model was formed from Botswana summer and winter season typical seasonal irradiation and temperature profiles. The PV array was modelled by an equivalent single diode circuit, the battery by an equivalent electrical model with state-of-charge dynamics, and the supercapacitor by an energy equation based on capacitance. The findings illustrate that summer provides greater total PV generation but with lower use efficiency due to afternoon cloudiness and hilly cycling, and lower energy but improved use in clear weather during winter. The battery–supercapacitor system improved system ruggedness: the battery provided long-term energy needs and the supercapacitor substituted for short transients, reducing peak battery current by as much as 80% and reducing hazard from degradation. The results identify Hybrid PV–Battery–Supercapacitor systems to be economically valuable both in enhancing efficiency and reliability for Botswana's rural electrification. Seasonal analysis puts into focus system designs that both mitigate abundance as well as variability of energy, supplemented with optimal storage capacity sizing and load-shifting strategies for the best utilisation of capacities.