Energy storage for a high penetration of renewables

This paper explores how the energy storage capacity required by an electric grid increases with the penetration of renewable generation. The paper uses the UK as a case study and aims to quantify the amount and duration of energy storage that the country will need to fully decarbonize its electric supply. The paper also studies the effect that the mix of renewables (wind + solar) has on the storage capacity needed and highlights that a greater mismatch between the generation and demand profiles will require a larger energy storage capacity. Therefore the right generation mix for the region should be used. Results show that the UK will need a storage capacity of approximately 7.63 TWh (4 days) to achieve an overall renewable penetration of 100%. Two important considerations are made: i) the mix between wind and solar is 79-21% and ii) a 5% of over-generation (and curtailment) is allowed. Assuming that the storage capacity is provided by compressed air systems (CAES) and considering the current costs of renewable generation, this scenario attains a levelized cost of electricity of 61 £/MWh. This scenario achieves the lowest possible LCOE despite the fact that 5% of the generated electricity is wasted and still paid-for. If a strict rule of zero-net curtailment was in place, the storage capacity required would almost double (14.93 TWh) and the final cost of electricity would be 2.3% higher.