Solar photovoltaic–thermal hydrogen production system based on full-spectrum utilization

Full-spectrum high-temperature water electrolysis enables efficient conversion from solar to hydrogen. However, the supply of electric and thermal energy derived from solar energy does not match the demand for electric and thermal energy in high-temperature water electrolysis, resulting in significant energy losses within the system. In this study, a solar photovoltaic-thermal hydrogen production system based on full-spectrum utilization is proposed. The concentrated sunlight is divided into two parts based on wavelength. Longer-wavelength sunlight is directed to the reactor, where it is converted into thermal energy to directly supply the endothermic water electrolysis reaction. Shorter-wavelength sunlight is directed to photovoltaic cells to generate electrical power for the reaction. To achieve a match between the supply and demand of electric and thermal energy, system parameters are optimized for the proposed system. The results demonstrate that the mismatch losses of the proposed system are reduced by 42.8 percentage points compared to a conventional photovoltaic water electrolysis system. The proposed system achieves a solar-to-hydrogen efficiency of 39.0% under optimum conditions with a cutoff wavelength of 1000 nm, surpassing that of photovoltaic water electrolysis and water-splitting thermochemical cycle systems by 19.0 and 21.6 percentage points, respectively. Based on the proposed method, the solar-to-hydrogen efficiency can be improved.