System Components

The following are the key components of a BESS System.

 

Batteries

lithium-ion (Li-ion) batteries are widely used in stationary BESS storage applications.  The U.S. Energy Information Administration (EIA) trends report on the U.S. storage market found that lithium-ion batteries currently represent more than 90% of of the storage market.

Battery Management System (BMS)

The Battery Management System (BMS) is a core component of any Li-ion BESS.  The primary job of the BMS is to protect the battery from damage.  The BMS ensures correct battery cells operate from state of charge, voltage, current, and temperature as well as prevent fires or explosions caused by thermal runaway and combustion.  The BMS also ensures that the battery cells remain balanced at the same state of charge. Any imbalance across the battery bank can cause cells to become stressed which can shorten their service or cycle life.

 

Power Conversion System (PCS) is a Hybrid Inverter

Li-ion battery bank requires an inverter to produce an alternating current (AC).  Some inverters operate bi-directionally, this means power can flow from DC to AC or vice-versa, this enables the ESS to both charge and discharge.

Energy Management System (EMS)

The energy management system handles the controls and coordination of BESS activity. The EMS communicates directly with the PCS and BMS to provide high-level coordination of the various components on-site.  The EMS is responsible to make decisions on when and how to dispatch.  This involves being aware of the BMS and PCS limitations and recognizing when the energy storage system can be used most effectively in the Time-of-use (TOU) window.  The EMS also serves as a single collection point for the performance data of an BESS.  A good EMS will be combined with a robust data collection and presentation platform which enables end-users and responsible parties access to information on a regular basis for system reporting as well as diagnostics.