Power systems with high penetrations of solar generation need to replace solar output when it falls rapidly in the late afternoon – the duck curve problem. Storage is a carbon-free solution to this problem. This essay considers investment in generation and storage to minimize expected cost in a Boiteux-Turvey-style model of an electric power system with alternating daytime periods, with solar generation, and nighttime periods, without it. In the most interesting cases, if energy market prices are uncapped, all expected cost minima are long-run competitive equilibria, and the long-run equilibrium value of storage capacity minimizes expected system cost conditional on generation capacities.
Keywords: electricity, storage, solar, renewable, equilibrium