Thermodynamic investigation of spectral splitting hybrid system integrated Cassegrain concentrator and mid/low-temperature solar thermochemical storage

The synergy of hybrid conversion and non-imaging optical concentrating technology is a promising solar energy utilization scheme. In this paper, a novel photovoltaic-thermochemical hybrid system based on Cassegrain concentrator and spectral beam splitting technology is proposed and comprehensively investigated to explore the feasibility of dish concentrator for mid/low-temperature thermochemical storage. The collimated secondary reflected optical path and the special TiO2–Na3AlF6 filter improved the high-density energy flow to be more compatible with the cascade of the PVT module and methanol steam reforming reactor. The features under typical operating conditions, optical control, and variable irradiance performance are analyzed via systematic mathematical methods, including ray tracing, energy flux calculation, energy conversion process, and system evaluation. Results indicate that the satisfactory optical efficiency of 81.1% is obtained by multi-objective optimization, while the average incident angle deviation is considered as a target. By regulating energy transfer through flow strategy, the conversion efficiency of solar products exceeds 42.4%. Meanwhile, the concentration ratio over 600 ensures a solar-exergy conversion capacity of more than 4.2% higher than reference systems under various irradiation, but the cutoff wavelength is not suitable to exceed 500 nm. In sum, the results are anticipated to contribute to improving the applicability of dish concentrators in distributed scenarios and the viability of full-spectrum solar energy absorption.