An evaluation of the NaS battery storage potential for providing regulation service in California

Sodium sulfur (NaS) batteries can provide energy storage, real-time dispatch, regulation, frequency response, and other essential services to the power grids. This study presents the technical characteristics, modeling approach, methodologies, and results for providing regulation services in the California Independent System Operator (CAISO) market. Two different scenarios were studied and compared: a scenario without intermittent renewable-energy resource penetration (base case) and a scenario with significant renewable-energy resource penetration (including wind) reaching 20% of CAISO's energy supply. In addition, breakeven cost analyses were developed for four cases. Based on the results of the technical and cost analyses, the opportunities for the NaS battery providing the regulation services are discussed, design improvements for the battery's physical characteristics are recommended, and modifications of the regulation signals sent to NaS batteries are proposed.