This report describes development of an effort to assess Battery Energy Storage System (BESS) performance that the U.S. Department of Energy (DOE) Federal Energy Management Program (FEMP) and others can employ to evaluate performance of deployed BESS or solar photovoltaic (PV) +BESS systems.
For battery systems, Efficiency and Demonstrated Capacity are the KPIs that can be determined from the meter data. Efficiency is the sum of energy discharged from the battery divided by sum of energy charged into the battery (i.e., kWh in/kWh out).
The document provides the basis for the development of homogenized performance metrics and a transparent reporting methodology at cell level, necessary for the reliable benchmarking of battery chemistries.
The scope of the indicator is to consider which part of the total energy required by the building/group of buildings (or by a specific function, such as heating or artificial lighting) and/or the generation from RES, during a certain period, is stored-in and then released from the storage system.
In this rapidly evolving field, while key performance indicators can be readily accessed, the performance evaluation and comparison of battery technologies remain a challenging task, due to the huge variation in the quality and quantity of data reported and the lack of a common methodology.
The proposed method is based on actual battery charge and discharge metered data to be collected from BESS systems provided by federal agencies participating in FEMP's performance assessment initiatives.