Influence of rectifiers on the techno-economic performance of alkaline electrolysis in a smart grid environment

Alkaline electrolysis is a mature technology with long lifetimes and high reliability. However, the conventional electroylzer systems are only designed for constant operation at full load. Depending on the employed rectifiers, they show reduced efficiencies in dynamic operation. Recent advances in rectifier and electrolysis systems allow their dynamic operation in a smart grid environment with volatile renewable energy generation. This study investigates the techno-economic benefits of a recently developed process current source in combination with an alkaline electrolyzer, compared to three frequently employed conventional rectifier topologies. The smart grid simulation regards three scenarios with differently scaled electrolyzer units and therefore, varying amounts of surplus energy. Simulation results display an increased amount of annually produced hydrogen from 2250 MWhH2,LHV for the worst conventional system to 3050 MWhH2,LHV for the new process current source, in the scenario with the highest electrolyzer scaling. In this case, a larger electrolysis system results in more partial load operation and here, the process current source outperforms all conventional rectifiers in amount of generated hydrogen as well as in the economic viability. The levelized costs of hydrogen are always more than 0.5 e/kgH2 cheaper, especially in highly dynamic operation.