Performance of a novel hybrid square receiver for high-temperature concentrating photovoltaic-thermal systems using cold-climate-compatible heat transfer fluids

• The thermal and thermodynamic performance of a novel photovoltaic thermal system is. • System performance with cold climate-friendly heat transfer fluids is investigated. • Among the liquid working fluids suitable for cold climates, Therminol®59 gives the best performance. • Air and supercritical CO 2 give almost the same performance at low Reynolds numbers. • Overall efficiencies (thermal and electrical) up to 86% are achievable at optimal conditions. Recent advancements in high-efficiency, high-temperature solar photovoltaic cells have sparked increasing interest in the development of high-temperature, high-concentration ratio concentrating photovoltaic thermal systems for generating high-grade thermal and electrical energy. This study proposes and investigates the performance of a novel square high-temperature CPV/T receiver coupled with a parabolic trough solar collector (PTSC) utilizing both gaseous (compressed air and supercritical CO 2 ) and liquid (pressurized water, Therminol® 59, Marlotherm® LH, and ethylene glycol) heat transfer fluids. In the analysis, a Monte Carlo ray-tracing numerical approach in SolTrace® was employed to compute an uneven heat flux profile, which was integrated with a finite volume CFD code via user-defined functions. The influence of key parameters, including receiver offset from the focal point, rim angle, receiver material thermal conductivity, and Reynolds number, on the system’s optical, energetic, entropy generation, and exergetic performance was evaluated and presented. Results showed that copper significantly reduces the temperature gradients across the square receiver by 74.3% compared to steel. Furthermore, it was observed that a receiver placement offset error within ± 25 mm has a minimal effect on the overall optical performance. Considering operation under cold climatic conditions, Therminol® 59 and ethylene glycol showed better performance, reaching corresponding maximum thermal efficiencies of 52.4% and 52.3%, and electrical efficiencies of 33.8% and 34.9%. Compressed air and supercritical CO 2 give nearly the same performance; however, the performance of air degrades at Reynolds numbers greater than 26 × 10 5 , due to the high pumping work and fluid friction irreversibility.