A Novel High-Temperature PEM Electrolyzer Resulting In Dramatically Improved Regenerative Fuel Cell System Performance

The most promising energy conversion and storage system for HAAs is the combination of photovoltaic (PV) arrays with a regenerative fuel cell energy storage system. This system uses the PV arrays during the day to power the airship and electronics, while utilizing excess power to split water with an electrolyzer, generating hydrogen and oxygen at high pressures. At night, the stored hydrogen and oxygen are fed to a fuel cell where they are converted to electricity, allowing the HAA to continue operation. The electrolyzer has a significant effect on the specific energy (Wh/kg) of the overall system, affecting the size of the reactant storage based on its operating pressure, and affecting the size of PV arrays needed based on its operating efficiency. The conditions at which the electrolyzer operates, such as temperature and pressure, can also dramatically affect the electrolyzer's balance-of-plant mass and parasitic power requirements. To take advantage of operating at higher temperature and pressure, development of both membrane electrode assemblies and lightweight electrolyzer stack components are needed that can operate at high temperature and pressure. Although there has been much research on high temperature PEM fuel cells, there has been little focus on high temperature PEM electrolysis.