PNNL

This report investigates the technical performance of the 1 MW, 3.2 MWh advanced vanadium flow battery energy storage system (FBESS), consisting of two 0.5 MW, 1.6 MWh strings, based on a number of reference performance and use case tests. The FBESS is located on the utility 12 kV distribution system, between the Turner Substation and SEL’s manufacturing facility in Pullman, Washington. Reference performance tests (RPTs) were intended to assess the general technical capability of the FBESS (e.g., stored energy capacity, ramp rate performance, ability to track varying charge/discharge commands, direct current (DC) battery internal resistance). Use case tests were used to examine the performance of the FBESS while engaged in specific grid services (e.g., arbitrage, frequency regulation, balancing, volt ampere reactive (var) support, dynamic peak shaving). The project determined performance metrics that are important for understanding FBESS performance when subjected to field operation for achieving economic benefits from measurements and/or calculations. These metrics were: • RTE with and without rest, with and without auxiliary loads • Auxiliary power consumption • Reference signal tracking • Temperature excursions beyond normal operating range • Parasitic power loss unaccounted by auxiliary load during rest, and • State of charge (SOC) excursions beyond normal operating range. These RPT and use case performance metrics were analyzed using recorded test results. In addition, the results and lessons presented are also beneficial for any task or effort that needs technical assessment on similar and different types of FBESS, and BESS in general, based on technical specifications and/or field deployment results, since the assessment methodology remains the same.