Development of Various Photovoltaic-Driven Water Electrolysis Technologies for Green Solar Hydrogen Generation

Direct solar hydrogen generation via a combination of photovoltaics (PV) and water electrolysis can potentially ensure a sustainable energy supply while minimizing greenhouse emissions. The PECSYS project aims at demonstrating a solar-driven electrochemical hydrogen generation system with an area >10 m(2) with high efficiency and at reasonable cost. Thermally integrated PV electrolyzers (ECs) using thin-film silicon, undoped, and silver-doped Cu(In,Ga)Se-2 and silicon heterojunction PV combined with alkaline electrolysis to form one unit are developed on a prototype level with solar collection areas in the range from 64 to 2600 cm(2) with the solar-to-hydrogen (StH) efficiency ranging from approximate to 4 to 13%. Electrical direct coupling of PV modules to a proton exchange membrane EC to test the effects of bifaciality (730 cm(2) solar collection area) and to study the long-term operation under outdoor conditions (10 m(2) collection area) is also investigated. In both cases, StH efficiencies exceeding 10% can be maintained over the test periods used. All the StH efficiencies reported are based on measured gas outflow using mass flow meters.