How Battery Energy Storage Systems Work
A Battery Energy Storage System works by storing electricity in batteries and releasing it when required — managed by a Power Conversion System, an Energy Management System and cloud monitoring so energy is used at the right time and cost.
Step 1: Electricity is generated or supplied
Electricity can come from solar PV, the grid, a generator, a renewable power plant or a hybrid system. For solar projects, generation peaks during daylight — and a solar system may produce more than the site can use at certain times. Without storage, this energy may be exported, curtailed or underutilised. With BESS, the excess can be stored.
Step 2: The battery stores energy
The battery is the core of the BESS, storing electrical energy in chemical form. Most modern commercial and utility-scale systems use lithium iron phosphate (LFP) chemistry, chosen for its safety profile, long cycle life and suitability for stationary storage. When charging, electricity flows into the battery until the system is instructed to discharge.
Step 3: The PCS converts the electricity
A battery stores DC power, but most buildings, factories and grids use AC. The Power Conversion System (PCS) converts AC to DC when charging and DC to AC when discharging. It is one of the most important parts of a BESS because it controls how energy flows in and out of the battery.
Step 4: The EMS controls the system
The Energy Management System (EMS) is the brain of the BESS. It decides when the battery charges, when it discharges and how the system responds to operating conditions — and can be programmed to:
- Charge the battery when solar generation is high
- Discharge during peak demand periods
- Reduce maximum demand charges
- Avoid overloading the site’s electrical infrastructure
- Support backup-power strategy
- Optimise battery performance
- Detect faults and operating issues
Step 5: The system discharges energy when needed
When the site needs power, the BESS discharges stored energy — during peak demand, evening hours, grid-constraint periods, solar fluctuations or high-tariff periods. For commercial and industrial users this is especially useful for maximum demand peak shaving: when a factory or building hits a demand spike, the BESS discharges to reduce the power drawn from the grid.
Step 6: Cloud O&M monitors performance
Modern BESS projects require continuous monitoring. Through cloud O&M platforms, operators can remotely track state of charge, temperature, charge/discharge activity, PCS performance, fault alerts, energy savings, availability and battery degradation — detecting issues early and reducing site visits.
Why system integration matters
A BESS is not just a battery — it is a complete electrical, software and safety system. The battery, PCS, EMS, transformer, protection and monitoring must work together. Poor integration can lead to underperformance, downtime, safety issues or lower returns, which is why system design and integration are critical.
Frequently Asked Questions
The main function of a BESS is to store electricity and release it when needed.
PCS stands for Power Conversion System. It converts electricity between DC and AC.
EMS stands for Energy Management System. It controls charging, discharging, optimisation and monitoring of the BESS.
Yes. BESS is commonly used with solar to store excess solar energy and improve energy utilisation.
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