Hybrid hydrogen production system utilizing photovoltaics, photocatalysis, and thermochemistry for effective full-spectrum solar energy harvesting

Converting solar energy into hydrogen offers a promising solution to address the intermittency of solar power and enable long-term energy storage. However, current methods of hydrogen production through photovoltaic, photocatalytic, and thermochemical processes often fail to consider the distinct energy quality across the solar spectrum, limiting their efficiency. In response, this paper presents an innovative, high-efficiency hydrogen production method that integrates these three processes while optimizing the utilization of solar spectrum energy. The method partitions sunlight into ultraviolet, visible, and infrared spectral bands to respectively drive photothermal catalysis, photovoltaic water electrolysis, and methanol reforming, along with the integration of waste heat recovery for enhanced energy efficiency. To evaluate the system performance, a comprehensive operational simulation is developed and assessment indices for the system’s thermodynamic performance, environmental benefits, and economic performance are established. Additionally, a sensitivity analysis is conducted to investigate the impacts of key parameters on the hydrogen production rate and energy efficiency. The results demonstrate that under rated working conditions, the system achieves a solar-to-hydrogen conversion efficiency of 40.20 %, an energy efficiency of 68.01 %, and an exergy efficiency of 57.52 %, which represents a 21 % improvement in solar-to-hydrogen conversion efficiency compared to standalone photoelectric-based hydrogen production systems. In addition, the production of 1 kg of hydrogen reduces carbon dioxide emissions by approximately 14.06 kg and saves around 5.74 kg of standard coal. In economic terms, the proposed system achieves an annual revenue growth rate of 16.62 % and an annual profit growth rate of 34.75 %, compared to the reference system. The sensitivity analysis further reveals that reducing the second separation wavelength and increasing the methanol reforming temperature can significantly enhance hydrogen production efficiency. This research provides a new approach for realizing the cascade utilization of the full solar spectrum and solar synergistic hydrogen production from fossil fuels.