Microgrids with high shares of variable renewable energy resources, such as wind, experience intermittent and variable electricity generation that causes supply-demand mismatches over multiple timescales. Lithium-ion batteries (LIBs) and hydrogen (H2) are promising technologies for short- and long-duration energy storage, respectively. A hybrid LIB-H2 energy storage system could thus offer a more cost-effective and reliable solution to balancing demand in renewable microgrids. Recent literature has modeled these hybrid storage systems; however, it remains unknown how anticipated, but uncertain, cost reductions and performance improvements will impact overall system cost and composition in the long term. Here, we developed a mixed integer linear programming (MILP) model for sizing the components (wind turbine, electrolyser, fuel cell, hydrogen storage, and lithium-ion battery) of a 100% wind-supplied microgrid in Canada. Compared to using just LIB or H2 alone for energy storage, the hybrid storage system was found to provide significant cost reductions. A sensitivity analysis showed that components of the H2 subsystem meaningfully impact the total microgrid cost, while the impact of the LIB subsystem is dominated by its energy storage capacity costs. Regarding efficiency, decreased electrolyzer efficiency causes the greatest increase in total system cost, whereas increased fuel cell efficiency has the greatest potential to reduce total system cost. As technologies evolve, the H2 subsystem assumes a greater role (i.e., it is larger and receives/supplies more energy over more hours) compared to the LIB subsystem, but LIB continues to provide frequent intra-day balancing in the microgrid.
