Thermodynamic analysis and optimization of photovoltaic/thermal hybrid hydrogen generation system based on complementary combination of photovoltaic cells and proton exchange membrane electrolyzer

Abstract

Solar hydrogen generation from water electrolysis driven by photovoltaic (PV) cell is a promising means of solar energy storage and hydrogen harvesting, which could transform the surplus PV power into a durable energy carrier with high-energy density and without pollution. However, the efficiency of the PV cell is easily decayed in high temperature, which limits the utilization of PV cell. On the other hand, the water electrolysis requires more electricity at low temperature, which influences the energy efficiency, and it needs to be improved from a thermodynamic perspective. This study proposes an efficient, flexible and no-carbon heat and hydrogen cogeneration system with a complementary combination of PV cells and proton exchange membrane (PEM) electrolyzer. This novel system utilizes water flow to decrease the PV temperature and decline the Gibbs free energy in the water electrolysis simultaneously, and the overall solar energy efficiency, exergy efficiency, and solar-to-hydrogen efficiency can reach as high as 62.67%, 20.29%, and 17.29%, respectively. The environmental performances of the system under different operating conditions are also analyzed, and the annual hydrogen generation rate and carbon dioxide reduction rate are as high as 47.52 kg/m2 and 15.91 t/m2, respectively. This novel system provides a convenient and efficient approach for solar energy storage and utilization, which is expected to fundamentally guide the future research and application of solar hydrogen generation.