Summary
Designing a BESS is not just about choosing a battery. It requires defining its application, power, energy, connection point, operation strategy, safety, degradation and associated electrical studies.
Starting point: the application
The first step in designing a BESS is to define what it is needed for. Designing for backup, peak shaving, arbitration, frequency control, solar integration or compliance with connection requirements is not the same.
The application defines the power, duration, energy reserve, number of cycles, control strategy and availability criteria.
Power and energy
Power is measured in kW or MW. Energy is measured in kWh or MWh. If a project needs to deliver 5 MW for 2 hours, an approximate energy capacity of 10 MWh will be required, without considering margins, losses, degradation or operational restrictions.
In practice, sizing must consider:
- Maximum charging power.
- Maximum discharge power.
- Required duration.
- System efficiency.
- Allowable discharge depth.
- Operational reserve.
- Future degradation.
- Ambient temperature.
- Load growth.
- Endpoint restrictions.
connection point
The connection point determines much of the electrical design. A BESS can be connected to low voltage, medium voltage, subtransmission or transmission. Depending on the voltage level, transformers, cells, switches, protections, measurement, communication, grounding and network operator requirements are defined.
An error at this stage can lead to costly redesigns or delays in project energization.
System architecture
A BESS can be centralized, modular, containerized, installed in an electrical room, with distributed inverters or with centralized PCS. The architecture depends on the size of the project, available space, maintainability, redundancy, environmental conditions and operation strategy.
Wiring routes, access, ventilation, air conditioning, fire detection, sectioning and security zones must also be considered.
Degradation
Batteries lose capacity over time. Degradation depends on chemistry, temperature, number of cycles, depth of discharge and operating strategy.
A serious design must ask:
- How much capacity is needed at the beginning?
- How much capacity is needed at the end of the expected useful life?
- Is initial oversizing required?
- Will there be a replacement or future increase in modules?
- What performance guarantees does the supplier offer?
Security
A BESS concentrates a lot of energy in a compact space. Therefore, security must be integrated from the design. Electrical protections, temperature monitoring, ventilation, early detection, isolation, sectioning, access control, fire protection and emergency protocols must be considered.
electrical studies
Before building or connecting a BESS, studies such as:
- Load flow.
- Short circuit.
- Coordination of protections.
- ArcFlash.
- Harmonics.
- Stability.
- Grounding.
- Voltage and reactive power control.
- Network code compliance evaluation.
common mistake
A common mistake is selecting battery capacity before studying the problem. This can lead to systems that are oversized, undersized, or difficult to connect.
Conclusion
Designing a BESS requires integrating electrical, energy, economic, operational and safety criteria. It's not just about buying batteries, but about designing a system that fulfills a specific function within a real network.
A well-sized BESS is based on operation data, connection limits, safety and electrical studies; This technical base avoids oversizing, undersizing or incorporating unnecessary risks.
If you need to design, evaluate or integrate a BESS system with technical criteria, check out our service. BESS engineering and energy storage.