Energy Storage Requirements for Achieving 50% Solar Photovoltaic Energy Penetration in California

Posted: August 19, 2016 - 15:00 / CA / Reports

The rapidly declining cost of solar photovoltaic (PV) technology in combination with renewable portfolio standards is driving increased PV deployment in California. However, the variability of the solar resource creates uncertainty about the amount of PV that could be deployed without enabling technologies such as energy storage. A key limiting factor for PV deployment is curtailment, or the PV energy that would need to be rejected by system operators due to the supply/demand balance of the system. Most published analyses of high PV penetration in California to date have focused on PV penetration levels up to about 20%–25% on an annual energy basis. In this paper, we go beyond previous analyses by exploring PV penetration levels of up to 50% in California (with renewable penetration over 66%), and we examine the potential role of storage.

Specifically, we examine the amount of storage that may be required to keep PV curtailment to acceptable levels. The amount of curtailment that is acceptable will depend on many factors, and for this analysis, we aim for a target level of curtailment that will keep the incremental cost of additional PV below the estimated variable cost of a combined-cycle generator in 2030, or about seven cents per kilowatt-hour (kWh). An analysis of the role of storage must consider the evolution of the grid and the likely deployment of various flexibility options. Before evaluating storage, we first consider the impact of increased generator flexibility, demand response, exports, and electric vehicles. We find that these measures can greatly increase the potential penetration of PV; however, even a very flexible power system will likely need additional storage to enable 50% penetration of PV.