Evaluations of Concepts for the Integration of Fuel Cells in Liquid Organic Hydrogen Carrier Systems

Liquid organic hydrogen carrier (LOHC) systems store hydrogen through covalent bonds. As the release of H2 from the LOHC carrier is an endothermic process, clever heat and system integration of this critical step with the exothermic fuel cell operation is highly desirable. The aim of this study is the evaluation of different configurations of this sequence. The results allow decisions on efficient process options. With respect to energy efficiency, the worst case is electric heating for providing the LOHC dehydrogenation heat. Most favorable, in contrast, is full heat integration between a high-temperature fuel cell and the dehydrogenation unit. Partial combustion of hydrogen for heat provision represents an attractive choice. Alternatively, hydrogen transfer to a CO2-free, organic fuel cell is another interesting option. This includes transfer hydrogenation, for example, conversion of acetone to isopropanol, followed by direct conversion of the latter in a fuel cell. While hydrogen combustion-driven dehydrogenation promises high overall power densities, the hydrogen transfer to an organic fuel represents a very efficient technology.