Test profiles for stationary energy-storage applications

Evaluation of battery and other energy-storage technologies for stationary uses is progressing rapidly toward application-specific testing. This testing uses computer-based data acquisition and control equipment, active electronic loads and power supplies, and customized software, to enable sophisticated test regimes which simulate actual use conditions. These simulated-use tests provide more accurate performance and life evaluations than simple constant resistance or current testing regimes. Several organizations are cooperating to develop simulated-use tests for utility-scale storage systems, especially battery energy-storage systems (BESSs). Some of the tests use stepped constant-power charge and discharge regimes to simulate conditions created by electric utility applications such as frequency regulation (FR) and spinning reserve (SR). Other test profiles under development simulate conditions for the energy-storage component of remote-area power supplies (RAPSs) which include renewable and/or fossil-fuelled generators. Various RAPS applications have unique sets of service conditions that require specialized test profiles. Almost all RAPS tests and many tests that represent other stationary applications need, however, to simulate significant time periods that storage devices operate at low-to-medium states-of-charge without full recharge. Consideration of these and similar issues in simulated-use test regimes is necessary to predict effectively the responses of the various types of batteries in specific stationary applications. This paper describes existing and evolving stationary applications for energy-storage technologies and test regimes which are designed to simulate them. The paper also discusses efforts to develop international testing standards.