Dynamic thermal testing of lead-acid batteries for the PREPA battery energy storage system

A test is being carried out to determine the thermal load that will be present in a 20 MW battery energy storage system (BESS) facility being built by the Puerto Rico Electric Power Authority (PREPA). Efforts were made to duplicate, on a smaller scale, the arrangement of the flooded lead-acid cells in the BESS and to generate ambient temperatures typical of Puerto Rico through use of an environmental chamber. A utility energy storage (UES) test cycle for the 12-cell series string was set up based on projected operating parameters scaled from the BESS for frequency regulation and spinning reserve operating modes. Battery temperatures were measured during UES cycling and fit to a thermal model for the system. Cell temperatures increased slowly over a week-long utility cycle and eventually were elevated by 13{degrees}C (23{degrees}F) in the most extreme case observed to date. Temperature increases are expected to be lower in the BESS facility due to a much higher air flow rate than in the test chamber.