Long-Duration Energy Storage in Reliable Wind and Solar Electricity Systems

Abstract

Several U.S. states mandate zero-carbon electricity systems based primarily on renewable technologies, such as wind and solar. Reliable and affordable electricity systems based on these variable resources may depend on the ability to store large quantities of low-cost energy over long timescales. Long-duration energy storage technologies (10 to 100s of hours) have much cheaper energy storage capital costs than lithium-ion batteries. Multidecadal weather datasets reveal unique long-duration energy storage roles, such as seasonal and multi-year storage, that increase the affordability of electricity from variable renewable energy, informing technology investments and policy. This thesis combines technoeconomic analysis with materials chemistry to advance long-duration energy storage in reliable wind and solar electricity systems. Given short-, mid-, and long-duration energy storage options in wind- and solar-based systems, the addition of long-duration energy storage (such as provided by underground hydrogen storage) reduced total system costs most compared to systems without storage. We analyzed the tradeoff between capital cost reductions and efficiency improvements of hydrogen conversion and storage in different electricity systems with varying levels of dispatchable fossil power and otherwise-curtailed wind and solar generation. In the systems featuring abundant zero-cost electricity (resulting from wind and solar generation exceeding mean demand), hydrogen storage systems were not highly sensitive to an efficient utilization of otherwise-curtailed power, but they were sensitive to capital cost reductions. Electrolyzers paired with seasonal or multi-year hydrogen storage in reliable wind and solar systems may operate infrequently and benefit from times of abundant, otherwise-curtailed, zero-cost electricity to drive electrolysis. The low abundance and price volatility of iridium represents a bottleneck for the scale-up of proton exchange membrane electrolyzers. We synthesized earth-abundant manganese antimony oxide catalysts via a new chemical vapor deposition route and assessed their long-term electrochemical durability. Earth-abundant oxygen evolution electrocatalysts may be suitable replacements for iridium, despite lower activity, in electrolyzers paired with hydrogen energy storage in reliable wind and solar systems.