Dynamic operation of water electrolyzers: A review for applications in photovoltaic systems integration

This review provides a comprehensive overview of the dynamics of low-temperature water electrolyzers and their influence on coupling the three major technologies, alkaline, Proton Exchange Membrane (PEM) and, Anion Exchange Membrane (AEM) with photovoltaic (PV) systems. Hydrogen technology is experiencing considerable interest as a way to accelerate the energy transition. With no associated CO2 emissions and fast response, water electrolyzers are an attractive option for producing green hydrogen on an industrial scale. This can be seen by the ambitious goals and large-scale projects being announced for hydrogen, especially with solar energy dedicated entirely to drive the process. The electrical response of water electrolyzers is extremely fast, making the slower variables, such as temperature and pressure, the limiting factors for variable operation typically associated with PV-powered electrolysis systems. The practical solar-to-hydrogen efficiency of these systems is in the range of 10% even with a very high coupling factor exceeding 99% for directly coupled systems. The solar-to-hydrogen efficiency can be boosted with a battery, potentially sacrificing the cost. The intermittency of solar irradiance, rather than its variability is the biggest challenge for PV-hydrogen systems regarding operation and degradation.