(Invited) Engineering Modeling of PEM Water Electrolysis: A Survey

The conversion of electric energy into pressurized hydrogen by means of water electrolysis is currently discussed as promising option to handle intermittent electricity supply that occurs with the increasing use of renewable energy sources. Subsequently, this hydrogen could be (1) either reconverted into electricity, or (2) converted into other energetic molecules, such as methane (power to gas) or liquid fuels, or (3) utilized as a feed stock for the chemical industry. Besides conventional alkaline water electrolysis, a water electrolysis technology based on a Polymer Electrolyte Membrane (PEM) is discussed since several years, which is the focus of the present contribution. The particular advantages of PEM water electrolysis are higher attainable current densities, higher voltage efficiency, and higher load flexibility. Current disadvantages include far lower technical maturity, shorter life time, and higher specific costs compared to alkaline water electrolysis. The formulation of appropriate physico-chemical models for solid polymer electrolysis can help to contribute to the solution of the above mentioned problems. In the present contribution state of the art of modelling of solid polymer electrolyzers is summarized and discussed.