With an increased push for renewable energy across the globe, the role of energy storage systems has become increasingly critical in ensuring grid stability, enhancing the efficiency of renewable integration, and providing a reliable power supply.
Renewable energy sources are intermittent - the sun doesn't always shine, and the wind doesn't always blow. This intermittency poses a significant challenge for power grid operators to balance supply and demand in real-time. Traditionally, fossil fuel power plants have been used to fill the gaps, but this solution is neither sustainable nor environmentally friendly.
Battery Energy Storage System (BESS) offers a compelling alternative by storing excess energy when production exceeds demand and releasing it when the demand arises. It is beneficial for geographies such as the Middle East and Central Asia, where there is ample potential for solar power combined with a lack of low-cost energy storage alternatives such as pumped hydro storage.
capacity of 152 MWh located in Rajnandgaon, Chhattisgarh (Source: pib.gov.in)
BESS Architecture
BESS is a rechargeable electrochemical Battery Energy Storage System commonly of type lithium-ion batteries, flow batteries, fuel cells, etc. The key components involved are as follows:
- Battery Subsystem: The battery subsystem is the primary energy storage built upon cell batteries assembled in battery modules. The modules are further connected in series and accommodated in rack mounting structures to have a DC bus. The battery racks are connected in parallel to meet the desired energy and power capacities. The battery subsystem is equipped with a Battery Management System (BMS) to ensure the safety and reliability of the batteries during operation, by monitoring key parameters such as State of Charge(SoC), voltage, and temperature.
- Power Conversion Subsystem: The PCS/inverter manages the bidirectional flow of power, converting it between DC and AC for both battery-to-grid and grid-to-battery operations. It includes one or more power conversion modules and a step-up transformer.The number and organization of the power conversion modules are based on cost-efficiency and reliability criteria. The PCS/inverter includes all the necessary switchgear, cables, and circuit breakers to connect to other subsystems (such as auxiliary, control, and protection equipment) to ensure secure and reliable operations.
- Control Subsystem: The BESS control, protection, and communications subsystem coordinates with all the BESS subsystems and equipment and implements all the functions and control algorithms to assure a safe, effective, and efficient operation of the BESS. This includes all the hardware & software components; and communications interfaces for local HMI/SCADA for on-site monitoring, control, protection, and information exchange with remote systems. This ensures proper power exchange with the grid, within the operational constraints.
Use cases for BESS
- Peak Shaving: The excess energy available during the off-peak hours can be utilized to charge BESS, and the stored energy can be consumed during the peak hours to reduce the overall charges associated with the fixed price of energy generation.
- High RE utilization: BESS provides a means to store excess renewable energy, leading to reduced curtailment. This can lead to the overall utilization of renewable energy and smoothing the variations associated with renewable energy supply.
- Frequency Regulation: BESS operates by either charging (absorbing excess energy in over-frequency conditions) or discharging (supplying energy in under-frequency conditions) to correct frequency deviations. It can provide a fast response (in the order of milliseconds) to maintain grid stability.
- Reserve Margin: BESS can be deployed in conjunction with RE to improve the reserve margin of the overall system, thereby reducing dependence on the costly peaker units. Due to its fast response, it can readily provide the required spinning reserve, thereby improving the overall grid resilience to sudden outages.
Conclusion
Despite its advantages, several challenges with BESS must be overcome before it can become the preferred energy storage solution. The main challenges are high initial costs, limited lifecycle and degradation over time, safety hazards, and environmental impacts related to recycling and disposal.
However, several emerging trends and innovations are likely to drive the future of BESS. Important among them are advanced electrochemical materials and technology, leveraging AI and data analytics for an enhanced BMS, efficient power electronics for energy conversion, and integration with renewables, microgrids, and EVs.
Notwithstanding current challenges, ongoing technological advancements and supportive policies are likely to enhance the role of BESS in ensuring stable, reliable, and clean energy.