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.

Can a battery energy storage system use a micro-grid control architecture?

The proposed method adapts the battery energy storage system (BESS) to employ the same control architecture for grid-connected mode as well as the islanded operation with no need for knowing the micro-grid operating mode or switching between the corresponding control architectures.

What is the difference between energy charged and energy discharged?

Energy charged into the battery is added, while energy discharged from the battery is subtracted, to keep a running tally of energy accumulated in the battery, with both adjusted by the single value of measured Efficiency.

What is battery discharging mode?

In discharging mode, the control system is supposed to limit the battery current and avoid over-discharging throughout the time that battery regulates the DC voltage by the control of energy discharge.

What is the difference between charging and discharging?

Generally, with some exceptions, percentage losses are higher at lower current, more consistently for charging than discharging. Some very high losses are found at low SOC (again, with exceptions). For charging, generally the higher efficiencies are achieved at higher SOC and higher current.