Scaling between areas of electrolyzer electrodes and solar modules achieving over 15 % solar to hydrogen conversion efficiency: Silicon and CIGS

This study aims to maximize the efficiency of solar-to-hydrogen generation systems by optimizing the relative areas of the electrodes and solar modules. The core objective is to identify the optimal balance between these components to achieve the highest energy conversion efficiency. We conducted a series of experiments using lab-scale silicon and copper indium gallium selenide solar modules, along with platinum on carbon and ruthenium dioxide-based electrocatalyst electrodes. By increasing the area of the water-splitting electrodes while decreasing the solar module area, we achieved solar-to-hydrogen conversion efficiencies of 12.30 % for the silicon module and 15.34 % for the copper indium gallium selenide module. Our findings indicate that the optimal ratio between the electrode and solar module areas depends on the type of solar module. To better understand this relationship, we analyzed the normalized current-voltage characteristics of the solar modules, which allowed us to evaluate the system's potential to reach the maximum theoretical efficiency. Additionally, we introduce the concept of coupling effectiveness to quantify how efficiently the integrated system utilizes captured solar energy. In this study, we achieved a coupling effectiveness of 85.7 %, which is the highest value reported to date for similar systems.