Multiphysics Modeling of a reversible PEM Electrolyzer & Fuel Cell.

Abstract

Electrolyzers are used to produce hydrogen and oxygen from electricity through water electrolysis. If the electricity comes from renewable sources, such as solar energy, the produced hydrogen, denoted as green-H2. Despite often forgotten, electrolyzers also produce pure O2, which has many different uses. E.g., in oxy-combustion processes. The storage and transport systems for H2 are problematic. they require high pressures and are susceptible of leakage and other losses. Hydrogen Fuel Cells use H2 to produce electricity, following the reversed operation than electrolyzers. Fuel Cells have high energy conversion efficiencies. Fuel Cells / electrolyzers with a polymer electrolyte membrane (PEM) are based on a cation exchange membrane that allows the transport of protons. It is possible to create a reversible device that can act as fuel cell or electrolyzer depending on the directions of the electrical and gas currents. A multiphysics model for a reversible PEM Electrolyzer – Fuel Cell has been implemented and solved. The model combines fluid dynamics to model the inflow/outflow of liquid and gasses: water, hydrogen, Oxygen, and Nitrogen. The model considers the relationship between the electrochemical reactions and the external electrical circuit, quantifying the electrical efficiency of the electrochemical device and the relationship with the extent of the reactions. In addition to this, the model addresses the two-directional coupling with temperature. I.e., the model includes the heat source due to activation and ohmic losses and the effect of the temperature on the efficiency of the hydrogen production. Results show that it is theoretically feasible to use reversible electrolyzers – fuel cells devices for the efficient production and utilization of green hydrogen.