Energy storage power supply function test standard

Can FEMP assess battery energy storage system performance?

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.

How is energy storage capacity calculated?

The energy storage capacity, E, is calculated using the efficiency calculated above to represent energy losses in the BESS itself. This is an approximation since actual battery efficiency will depend on operating parameters such as charge/discharge rate (Amps) and temperature.

What are the KPIs of a battery system?

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).

How do you evaluate efficiency and demonstrated capacity of a Bess sub-system?

Evaluate Efficiency and Demonstrated Capacity of the BESS sub-system using the new method of this report. Compare actual realized Utility Energy Consumption (kWh/year) and Cost ($/year) with Utility Consumption and Cost as estimated using NREL’s REopt or System Advisor Model (SAM) computer programs.

What are the KPIs of a PV system?

The KPIs reported are Availability (% up-time) and Performance Ratio (PR). If the PV system output was zero or less than 5% of the model estimate, then the time interval was counted as “unavailable.” For hours when the PV system was “available,” the measured energy delivery was divided by a reference yield to calculate PR.

What is the maximum energy accumulated in a battery?

The maximum amount of energy accumulated in the battery within the analysis period is the Demonstrated Capacity (kWh or MWh of storage exercised). In order to normalize and interpret results, Efficiency can be compared to rated efficiency and Demonstrated Capacity can be divided by rated capacity for a normalized Capacity Ratio.