Design of a hemispherical reactor with radiation regulation for efficient solar thermochemical fuel production

Xiaoli Lu, Jiahui Lou, Kai Zhao, Zhenyu Tian, Lisha Liu, Zhongrui Gai and Yong Hao

Applied Energy, 2025, vol. 399, issue C, No S0306261925012401

Abstract: Solar thermochemical cycle (STC) for CO2 splitting offer a promising pathway for sustainable fuel production. The key performance indicator is solar-to-fuel efficiency, which is highly dependent on regulating incident solar radiation and minimizing re-radiation loss during the temperature swing of two-step solar thermochemical cycle. In this study, we propose a hemispherical fixed-bed reactor design incorporating a spectrally-selective transmissive window and a variable iris. This configuration shall facilitate rapid redox cycle with reduced energy losses, thereby enhancing solar-to-fuel efficiency, feedstock conversion, and power output. A comprehensive thermodynamic model is developed to evaluate the reactor's performance under practical operating limits, including low concentration ratios and fluctuating direct normal irradiance (DNI). For a typical ceria-based solar thermochemical cycle operating between 900 °C and 1600 °C, results show that the new window design could reduce re-radiation loss by 72.09 %, increasing solar-to-fuel efficiency from 11.09 % to 12.10 % under a 1700 nm cut-off wavelength and a 40 mm aperture radius (concentration ratio of 3500). The application of the spectrally-selective transmissive coating to quartz window would enable solar-to-fuel efficiencies exceeding 11 % at moderate concentration ratios (1000−3000). The selective coating would also reduce solar mirror area by 38.00 % at concentration ratio of ∼1400, lowering the total cost of solar concentrating system by 33.18 %. Furthermore, multi-objective optimization using NSGA-II identifies optimal trade-offs, achieving simultaneous enhancements in solar-to-fuel efficiency, feedstock conversion, and power output to approximately 11 %, 15 %, and 1 kW, respectively. This innovative reactor window design provides a viable strategy for achieving efficient and rapid solar thermochemical cycle under real on-sun scenarios.

Keywords: Solar fuel; Solar thermochemical cycle; Reactor design; Multi-objective optimization (search for similar items in EconPapers)
Date: 2025
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DOI: 10.1016/j.apenergy.2025.126510

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