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.

How do you calculate battery efficiency?

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). This must be summed over a time duration of many cycles so that initial and final states of charge become less important in the calculation of the value.

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.

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 to normalize rated capacity compared to rated efficiency?

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. The following steps are proposed for an assessment.

How is metered PV energy delivery compared to a computer model?

That method compared actual metered PV system energy delivery with that of a computer model. The computer model used was the National Renewable Energy Laboratory’s (NREL’s) System Advisor Model (SAM). The KPIs reported are Availability (% up-time) and Performance Ratio (PR).