Energy Storage Considerations for High Renewable Power Penetration: A Case Study

A simple model for high penetration wind and solar for the MISO region of North America is used to study the effects of geographical diversity, source diversity, and over-generation on storage capacity requirements. Combining wind and solar generation over a wide geographical region significantly reduces the storage requirements. Further substantial reduction occurs using over-generation of wind and solar and allowing a modest energy deficit to be made up by dispatchable sources. Based on a simple model we found that for 95% of the load energy supplied by wind and solar (with the other 5% supplied by other dispatchable sources) with approximately 10% over-generation approximately 1 day of storage of the average load energy per year of storage is required for energy balance. A simple model to estimate total capital costs is minimized for approximately 15-20% over-generation.