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

Direct solar hydrogen generation via a combination of photovoltaics (PV) andwater electrolysis can potentially ensure a sustainable energy supply whileminimizing greenhouse emissions. The PECSYS project aims at demonstrating asolar-driven electrochemical hydrogen generation system with an area >10 m 2with 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 siliconheterojunction PV combined with alkaline electrolysis to form one unit aredeveloped on a prototype level with solar collection areas in the range from 64 to2600 cm 2 with the solar-to-hydrogen (StH) efficiency ranging from 4 to 13%.Electrical direct coupling of PV modules to a proton exchange membrane EC totest 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 inves-tigated. In both cases, StH efficiencies exceeding 10% can be maintained over thetest periods used. All the StH efficiencies reported are based on measured gasoutflow using mass flow meters.