Summary
A BESS is a battery-based energy storage system. It allows electricity to be stored when it is available and delivered later when the system needs it. In modern electricity projects, this capacity is key to integrating renewables, reducing demand peaks, supporting critical loads and providing greater operational flexibility.
What is a BESS?
BESS means Battery Energy Storage System, or energy storage system with batteries. Although it is often described as a “large battery”, it is actually a complete system that integrates batteries, inverters, transformers, protections, control systems, communications, air conditioning and security elements.
Its main function is to store electrical energy and deliver it later under a defined strategy. It can be charged from the grid, from a solar plant, from wind generation or from another available source. It can then discharge that energy to support a load, inject power into the grid, reduce peak demand, or support a facility.
Power and energy
To understand a BESS there are two essential concepts: power and energy.
Power, measured in kW or MW, indicates how much energy the system can deliver or absorb at an instant. Energy, measured in kWh or MWh, indicates how long you can sustain that delivery.
For example, a 10 MW/20 MWh BESS can deliver 10 MW for about 2 hours. A 10 MW/40 MWh BESS can deliver the same power, but for approximately 4 hours. Therefore, two systems with the same power can solve very different needs.
Main components
A BESS typically includes:
- Batteries: They store energy in electrochemical form.
- BMS: monitors voltage, current, temperature, state of charge and safety conditions of batteries.
- PCS or bidirectional inverter: It converts direct current into alternating current and allows charging or discharging.
- EMS: defines the system operation strategy.
- Transformers and electrical cells: adapt the voltage level to the connection point.
- Auxiliary systems: air conditioning, detection, fire protection, communications, control and monitoring.
Why does it matter?
Electrical systems are changing. Today there is more renewable generation, more power electronics, more demand for operational continuity and more need for flexibility.
A BESS can help:
- Reduce demand peaks.
- Back up critical loads.
- Store solar or wind surpluses.
- Support frequency and voltage control.
- Improve the use of existing electrical infrastructure.
- Increase flexibility in industrial or renewable projects.
Practical example
An industrial plant may have high consumption during certain hours of the day. If those peaks increase electrical costs, a BESS can be unloaded at those times to reduce the demand seen from the grid. This application is known as peak shaving.
In a solar plant, the BESS can store surplus generation during hours of high radiation and deliver it later, when solar production decreases or the energy has a higher value.
common mistake
A common mistake is to think that designing a BESS consists only of defining how many MWh are needed. In reality, the application, load profile, connection point, degradation, operation modes, safety, electrical studies and network operator requirements must be analyzed.
Conclusion
A BESS is a key tool for more flexible, safe and efficient electrical systems. But for it to work correctly, it must be designed with clear technical criteria and not just as an equipment purchase.
In projects with energy storage, the early definition of application, power, duration, connection point and electrical studies allows the solution to be born with technical criteria from its origin.
If you are evaluating the role of a BESS in your infrastructure, review our service BESS engineering and energy storage.