Analysis of a three-band spectrum splitting photovoltaic-photothermal driven SOEC hydrogen production system

To achieve cascade conversion of the full-spectrum solar energy and the complementary production of hydrogen from electric and thermal energy, this study proposes a new solar three-band spectrum-splitting photovoltaic-photothermal driven SOEC hydrogen production system. Three-band spectrum-splitting of solar spectrum is conducted basing on the different light energy qualities, which are used for photovoltaic and concentrated heat collection, then the electrical and thermal energy are input into SOEC system. This study develops a thermodynamic model of a solar spectrum splitting and SOEC system, and it investigates the coupled effects of SOEC parameters, including operating temperature and current density, and solar spectrum splitting parameters, including concentration ratio and spectrum splitting wavelength, on the system solar-to-hydrogen energy efficiency. After optimizing the parameters, the maximum efficiency achieved 47.38% within the investigated conditions, and the energy efficiency increase by 5–7 percentage points compared with non-splitting system. The system was further optimized by combining the S-CO₂ Brayton cycle, which makes the spectrum splitting wavelength more stable, improves the efficiency of photovoltaic cells by 10 percentage points after the spectrum splitting and increases the energy efficiency under low-temperature SOEC conditions. The spectrum-splitting system also showed advantages in economic performance compared to non-splitting system on the levelized cost of hydrogen. This study provides guidance for the combination of solar spectrum splitting with hydrogen production.