Progress Towards Commercial Solid Hydrogen Storage Systems

Abstract

Cella Energy has developed an ammonia borane-poly(ethylene oxide) solid hydrogen storage fuel that is being demonstrated as a lightweight high-performance replacement for batteries in a number of premium markets such as powering unmanned aerial vehicles. Cella’s technology will be suitable for the high energy requirements of “green/electric aircraft” replacing carbon fuels for powering on-board systems with a safety factor that exceeds the capability of compressed hydrogen. Development of a viable hydrogen storage system will overcome a critical barrier for the widespread commercialization of hydrogen and fuel cells technologies, an emerging renewable, clean energy industry with potential for growth in stationary, portable, and transportation areas. One of the most promising approaches to achieve high energy density system goals is to store hydrogen as a solid chemical hydride and release the hydrogen thermally, ideally between 80-150°C. The process by which the solid hydrogen fuel will be used is conceptually easy: the fuel is packaged as discrete “pellets” that are in contact with an ignition element such as a heater, insulated, and packed into a cartridge-type container. Combined with the appropriate electronic controls and filters, this is a hydrogen storage fuel system. Several challenges impact the success of these systems significantly. Simply put, in addition to hydrogen, all solid hydrogen fuels release some quantity of toxic impurities on heating, and many fuels expand rapidly and considerably while releasing a large quantity of heat, which imparts mechanical stress on packaging, among other issues. In addition, some volatiles are able to oligomerize in the gas phase, which means that if not trapped before leaving the hydrogen fuel cartridge then there is high probability of clogging fuel lines to the fuel cell based energy conversion system, as well as contamination of the fuel cell stack. This presentation will present an overview of Cella’s efforts to develop solid hydrogen fuel systems, as well as active R&D efforts to understand and optimize solid hydrogen material properties for safe storage and dehydrogenation when fuel is needed.