Efficient storage capacity in power systems with thermal and renewable generation

Power systems with high shares of wind and solar power have to balance their intermittent nature. Pumped-hydro storage plants can provide the required flexibility, while thermal backup plants offer an alternative. This paper proposes a capacity planning model to describe the efficient technology portfolio. Drawing on a residual load duration curve, we derive the efficient storage capacity and discuss its dependence on cost parameters, as well as the effect of periods with renewable generation in excess of load. A case study for Germany applies the model and highlights the impact of CO2 prices on storage efficiency.