Operational experience with a liquid organic hydrogen carrier (LOHC) system for bidirectional storage of electrical energy over 725 h

Hydrogen storage in liquid organic hydrogen carriers (LOHC) enables the utilization of renewable energy in different sectors. In this paper, we describe the operational experience with one single LOHC system for bidirectional electrical energy storage at the kW scale. The system includes a reactor for the hydrogenation and dehydrogenation of LOHC, as well as a fuel cell and an electrolyzer based on polymer electrolyte membrane (PEM) technology. The LOHC used is the substance pair dibenzyltoluene/perhydro-dibenzyltoluene. For dehydrogenation, the upflow operation with common discharge of liquid and gaseous product was found to be the preferred mode of operation. For hydrogenation, it was shown that stable operation is possible also with fluctuating hydrogen production from the electrolyzer. After operating the reactor for 725 h in the hot state, i.e., at temperatures above 150 degrees C, samples of the catalyst and LOHC were taken and analyzed. These showed no signs of serious degradation.