Role of Liquid Hydrogen Carriers in Deeply Decarbonized Energy Systems

Hydrogen can be valuable for deep decarbonization of electricity systems as well as energy end-uses where direct electricity is challenged. While most hydrogen supply chain analyses focus on storing hydrogen as compressed gas hydrogen (CGH2) storage, hydrogen storage systems with lower capital cost of storage capacity such as liquefied hydrogen (LH2) and liquid organic hydrogen carriers (LOHC) may provide a differentiated value for energy system decarbonization. However, the latter systems have disadvantages (e.g., higher capital cost of charge/discharge capacity, boil-off, high energy requirement for conversion/reconversion) that could impede their deployment. In this study, we expand upon a previously developed electricity-hydrogen infrastructure planning model, DOLPHyN, to explore the value of liquid hydrogen solutions for energy storage and transport in a deeply decarbonized energy system. First, we show that TOL-LOHC (i.e., toluene-based LOHC) and LH2 are beneficial as seasonal energy storage systems, while CGH2 is more suitable for shorter-duration storage (e.g., weekly) cycling. The addition of LH2 and LOHC enables more efficient utilization of deployed electric generation and power-to-hydrogen generation infrastructures. Second, we show that LH2 is more favorable than LOHC for providing long-term storage for the power sector because its primary capital costs and energy penalty for conversion are incurred during charging periods, which typically correspond to when renewable energy is more abundant. Cost effectiveness of LH2 is based on accounting for boil-off rates of large-scale LH2 systems. Third, we show that commercial viability of LOHC is strongly tied to the ability to lower the energetic consumption of the dehydrogenation process as well as its capital cost.