Assessing the role for long-duration energy storage in microgrids considering resilience, energy cost savings, and CO2 emission reductions

<title>Abstract</title> <p> Long duration energy storage (LDES)—an emerging suite of technologies with larger energy capacity and lower per-kWh cost—could be deployed in microgrids to increase energy resilience, reduce energy costs, and mitigate CO ₂ emissions. We analyze the case for three types of LDES—with durations of 8 h, 12 h, and 100 h—and quantify the economics and effect on investment and emissions of adding LDES to microgrids built to protect against long-duration outages. We offer a modeling tool that determines the cost-optimal capacity and operation of distributed energy resources (DERs) in a microgrid and explicitly simulates a microgrid’s capability to ride through routine and long-duration outages. We apply the model to seven commercial customers in southern California, and assess conditions today, in future years with lower DER costs and higher electric rates, and under policies that restrict CO ₂ and pollutant emissions from microgrids. We find that LDES can enhance resilience, pairs with larger solar photovoltaic systems, and increases the supply of clean energy, but that LDES competes with Li-ion storage for the same operational role and in general is not economic under conditions today nor in future years with lower DER costs, nor under policies that restrict emissions and hence benefit solar-plus-storage systems. Results indicate a potential niche case for LDES in microgrids: cases where the customer has load that is diurnal and peaky at midday and requires high-resilience power supply for a smaller subset of total load. </p>