How BESS work

BESS (Battery Energy Storage Systems)

Battery Energy Storage Systems (BESS) work by storing excess energy generated from renewable sources such as solar and wind, for later use. The energy is stored in batteries, which are charged when the energy generation is high and discharging the energy when it is needed, such as during peak energy demand periods or when renewable energy sources are unavailable. BESS can improve grid stability and support integration of renewable energy sources into the grid. They can also provide various services such as frequency regulation and peak shaving.

How battery energy storage systems work

The main components of a Battery Energy Storage System (BESS) include:

  1. Battery cells: This is the core component of the BESS, where the energy is stored and discharged. There are different types of battery cells available, including Lithium-ion, Lead-Acid, and Sodium-Sulfur, each with its own advantages and disadvantages.

  2. Inverter: This device converts direct current (DC) from the battery into alternating current (AC) for use in the grid.

  3. Control system: This includes software and hardware that monitor and manage the operation of the BESS, including charging and discharging the battery, ensuring grid stability, and optimizing the energy flow.

  4. Power electronics: This includes DC-DC converters, AC-DC converters, and DC-AC inverters that regulate the flow of energy between the battery and the grid.

  5. Safety systems: This includes various systems such as fire suppression, cooling, and ventilation, to ensure the safe and reliable operation of the BESS.

  6. Energy management system (EMS): This is a software platform that helps manage the operation of the BESS by monitoring energy flow, forecasting demand, and optimizing the use of stored energy.

Battery cells

Battery Energy Storage System (BESS) battery cells are the core component where energy is stored and then discharged as needed. There are several types of battery cells used in BESS, including:

  1. Lithium-ion (Li-ion) batteries: These are widely used due to their high energy density, long cycle life, and relatively low self-discharge rate.

  2. Lead-acid batteries: These are widely used due to their low cost and mature technology, but have relatively low energy density and short cycle life compared to Li-ion batteries.

  3. Sodium-Sulfur (NaS) batteries: These are high-temperature batteries that offer high energy density and long cycle life, but are relatively expensive and require specialized handling due to the use of molten sodium.

  4. Flow batteries: These batteries store energy in two tanks, with the flow of a liquid electrolyte determining the flow of energy. They have long cycle life and can be quickly charged and discharged, but are relatively expensive.

The choice of battery cells depends on various factors such as the specific energy requirements, cost, and environmental conditions of the BESS.

Inverters

The inverter is a critical component of a Battery Energy Storage System (BESS), as it converts direct current (DC) from the battery cells into alternating current (AC) for use in the grid. There are several types of inverters used in BESS, including:

  1. Grid-tied inverters: These inverters are designed to synchronize with the grid frequency and voltage and provide AC power to the grid.

  2. Stand-alone inverters: These inverters are designed to operate independently of the grid and provide AC power to a local load.

  3. Bidirectional inverters: These inverters can both receive and send energy to the grid, allowing the BESS to both charge and discharge the battery.

The choice of inverter depends on various factors such as the grid connection type, the required power output, and the cost of the inverter. It is important to choose an inverter that is compatible with the battery cells and control system of the BESS to ensure efficient and safe operation.

Control System

The control system of a Battery Energy Storage System (BESS) is responsible for managing the operation of the BESS, including charging and discharging the battery, ensuring grid stability, and optimizing the energy flow. The control system typically includes:

  1. Battery Management System (BMS): This monitors the state of charge (SOC), state of health (SOH), and temperature of the battery cells and manages their safe operation.

  2. Energy Management System (EMS): This system optimizes the energy flow between the battery and the grid, including forecasting energy demand, scheduling battery charging and discharging, and ensuring grid stability.

  3. Grid Control System: This system monitors and controls the BESS’s connection to the grid, ensuring compliance with grid codes and regulations, and providing grid services such as frequency regulation and peak shaving.

The control system uses various sensors and actuators to monitor and control the BESS and communicates with the grid and other components of the BESS through a communication network. The control system software is typically developed using real-time operating systems and programming languages such as C++, Python, and MATLAB. The choice of control system depends on the specific requirements of the BESS and the grid connection, and must be carefully designed to ensure reliable and efficient operation.

Power electronics

Power electronics are a critical component of a Battery Energy Storage System (BESS), as they regulate the flow of energy between the battery cells and the grid. The main types of power electronics used in BESS include:

  1. DC-DC converters: These convert direct current (DC) from the battery cells to the required voltage for use in the grid or for charging and discharging the battery.

  2. AC-DC converters: These convert alternating current (AC) from the grid to DC for charging the battery or for use in the BESS.

  3. DC-AC inverters: These convert DC from the battery to AC for use in the grid or for providing AC power to a local load.

The choice of power electronics depends on various factors such as the voltage and current requirements, the efficiency, and the cost of the electronics. Power electronics must be carefully designed and tested to ensure reliable and efficient operation and to meet grid connection requirements. The power electronics used in BESS typically use semiconductor devices such as diodes, transistors, and thyristors to control the flow of energy.

Safety systems

Safety is a critical concern in the design and operation of a Battery Energy Storage System (BESS), as the high energy stored in the battery cells poses a potential risk in case of failure. To ensure safe operation, BESS typically include several safety systems, including:

  1. Battery Management System (BMS): This monitors the state of charge (SOC), state of health (SOH), and temperature of the battery cells, and manages their safe operation, including disconnecting the battery in case of over-temperature, over-voltage, or over-current.

  2. Fire Suppression System: This system uses fire-retardant materials, fire alarms, and fire suppression systems such as water sprinklers or fire extinguishers to prevent and respond to fires in the BESS.

  3. Ventilation System: This system ensures proper ventilation to dissipate heat from the battery cells and reduce the risk of thermal runaway, a dangerous self-reinforcing thermal reaction.

  4. Ground Fault Detection System: This system detects and isolates ground faults in the BESS, reducing the risk of electrical shock and fire.

  5. Overcurrent Protection: This system protects the BESS components from over-current, reducing the risk of damage and fire.

The safety systems used in BESS must be designed and tested to meet industry standards and regulations, and regular maintenance and testing must be performed to ensure the safety of the BESS.

Energy management system

An Energy Management System (EMS) is a critical component of a Battery Energy Storage System (BESS), as it optimizes the flow of energy between the battery and the grid. The EMS typically includes the following functions:

  1. Energy Forecasting: This function predicts the future energy demand, allowing the BESS to schedule charging and discharging to meet the predicted demand.

  2. Battery Charging and Discharging Scheduling: This function schedules the charging and discharging of the battery to meet the energy demand, ensuring efficient and cost-effective operation.

  3. Grid Stability: This function ensures grid stability by controlling the energy flow between the battery and the grid, providing grid services such as frequency regulation and voltage control.

  4. Power Quality: This function ensures that the power supplied by the BESS meets grid standards, including voltage and frequency stability.

  5. Cost Optimization: This function optimizes the energy flow to minimize the cost of energy, taking into account energy prices, grid connection fees, and other costs.

The EMS communicates with other components of the BESS, such as the battery management system (BMS) and grid control system, to monitor and control the BESS. The EMS software is typically developed using real-time operating systems and programming languages such as C++, Python, and MATLAB, and must be designed and tested to ensure reliable and efficient operation.

Conclusion

A Battery Energy Storage System (BESS) is a critical component of modern renewable energy systems, allowing energy to be stored and used when needed. A BESS typically includes several key components, including the battery cells, inverters, control system, power electronics, and safety systems.

The battery cells store energy, and the inverters regulate the flow of energy between the battery and the grid. The control system manages the operation of the BESS, including forecasting energy demand, scheduling battery charging and discharging, and ensuring grid stability. The power electronics regulate the flow of energy and the safety systems ensure the safe operation of the BESS.

The design and operation of a BESS must be carefully considered, taking into account various factors such as energy demand, grid requirements, safety, and cost. The BESS must be designed and tested to meet industry standards and regulations, and regular maintenance and testing must be performed to ensure reliable and efficient operation. The BESS plays a critical role in enabling the transition to a low-carbon, sustainable energy system, and its continued development is essential for the future of renewable energy.