PNNL

Abstract

In this work, we describe the benefits and challenges of a green approach to seasonal energy storage using ethanol as a liquid organic hydrogen carrier (LOHC). We evaluate the cycling efficiency of hydrogen release from ethanol (EtOH) to form ethyl acetate (EtOAc) as the spent LOHC and the subsequent regeneration of EtOH from EtOAc catalyzed by a single molecular catalyst, Ru-MACHO, at moderate pressures of H2 at low temperatures. From experimental and computational studies, we were able to minimize catalyst deactivation, to regenerate the active catalyst post reactions, and to establish the energy profile of the deactivation pathway relative to the on-cycle pathway catalyzed by Ru-MACHO. Based upon these findings, we performed a reactor design analysis to determine the footprint of an EtOH-based storage system to provide 200 MWh of energy by storing 5 Mt of H2 . We conclude that the heating and cooling required to maintain H2 partial pressure present a significant engineering challenge for widespread deployment of this system.