Commonly asked questions

A Battery Energy Storage System (BESS) is a system that stores electrical energy in batteries and can release that energy for use when needed. BESS units can be connected to the grid, renewable energy sources, or used in off-grid applications. They help balance supply and demand, store excess renewable energy, and provide backup power.

BESS works by charging batteries when there is surplus electricity (e.g., when renewable energy generation exceeds demand) and discharging stored energy when there is a shortage (e.g., during peak demand or when renewable generation is low). The system includes batteries, inverters, and control systems that manage charging and discharging processes.

The most common types of batteries used in BESS are:

• Lithium-ion batteries: These are the most widely used due to their high energy density, efficiency, and declining cost.
• Lead-acid batteries: Traditionally used but now being phased out in favor of lithium-ion for most large-scale applications.
• Flow batteries: These are gaining attention for long-duration energy storage applications because they offer scalability and a longer cycle life.
• Sodium-sulfur and other advanced chemistries: These are used in specialized applications but are less common.

BESS is used in a variety of applications, including:

• Grid stabilization: Supporting grid reliability by balancing supply and demand.
• Renewable energy integration: Storing excess renewable energy (e.g., from solar or wind) and providing it when needed.
• Peak shaving: Reducing demand during peak times to lower electricity costs and emissions.
• Backup power: Providing reliable backup power during outages, especially for critical infrastructure and remote areas.
• Electric vehicle charging: Supporting EV charging stations and managing energy use.

The lifespan of a BESS unit depends on the battery chemistry and usage patterns. Lithium-ion batteries typically last between 10 to 15 years or 3,000 to 5,000 charge/discharge cycles. The overall system's lifespan can also be affected by environmental conditions, maintenance, and operational practices.

Several factors can affect BESS performance, including:

• Battery chemistry: Different chemistries have different energy densities, cycle lives, and efficiencies.
• Temperature: Extreme temperatures can degrade battery performance and lifespan.
• Depth of discharge (DoD): Frequent deep discharges can reduce battery life.
• Charge and discharge rates: High charge/discharge rates can stress the battery and reduce its lifespan.
• Maintenance: Proper maintenance can help maximize performance and longevity.

The key benefits of BESS include:

• Grid reliability: Ensures a stable and reliable power supply by providing backup power and balancing electricity supply and demand.
• Renewable energy integration: Supports the increased use of renewable energy by storing excess generation and making it available when needed.
• Cost savings: Reduces energy costs by storing electricity during off-peak hours and discharging during peak hours, thus reducing demand charges.
• Emissions reduction: Helps reduce reliance on fossil fuel power plants, thereby reducing greenhouse gas emissions.
• Energy independence: Provides backup power during grid outages and supports off-grid applications.

Some of the challenges include:

• Cost: BESS systems can be expensive, particularly for large-scale applications. However, costs are declining rapidly as technology improves.
• Battery lifespan and degradation: Over time, battery performance degrades, reducing capacity and efficiency. Replacing batteries adds to the system's lifecycle cost.
• Recycling and disposal: End-of-life management, including recycling and disposal, can be challenging and needs proper handling to avoid environmental harm.
• Safety: Battery storage systems, particularly lithium-ion batteries, can pose fire and safety risks if not managed properly.
• Grid integration: Integrating BESS with existing grid infrastructure requires careful planning and investment in grid management technologies.

BESS units, especially those using lithium-ion batteries, have inherent safety risks, including thermal runaway, fires, and explosions. However, modern systems are designed with multiple safety features such as advanced battery management systems (BMS), fire suppression systems, temperature controls, and safety standards compliance. Proper installation, maintenance, and operational practices are critical for ensuring safety.

At the end of its life, BESS can be:

• Recycled: Valuable materials like lithium, cobalt, and nickel can be recovered through recycling processes, though recycling infrastructure is still developing.
• Repurposed: Batteries that have reduced capacity but are still functional can be repurposed for less demanding applications, such as residential energy storage or backup power.
• Disposed of: Batteries that cannot be recycled or repurposed need to be disposed of properly, often as hazardous waste, to prevent environmental contamination.

The cost of a BESS depends on the size, battery chemistry, and specific application. For utility-scale lithium-ion systems, costs have been steadily decreasing and can range from $300 to $600 per kilowatt-hour (kWh) for the full system, including installation. The total cost can also vary based on grid integration, regulatory requirements, and maintenance needs.

BESS plays a critical role in renewable energy systems by:

• Storing excess renewable energy: During periods of high renewable generation (e.g., midday solar production), BESS stores surplus energy for later use.
• Balancing supply and demand: By discharging stored energy when renewable generation is low or when demand is high, BESS helps stabilize the grid.
• Enhancing reliability: BESS helps mitigate the intermittency of renewables, ensuring a more reliable and consistent energy supply.

BESS reduces emissions by:

• Enabling greater integration of renewables: By storing renewable energy and reducing the need for fossil fuel generation, BESS helps lower overall emissions.
• Replacing fossil fuel peaker plants: BESS can replace peaker plants, which are typically less efficient and more polluting.
• Optimizing energy use: By shifting energy use to periods of lower emissions (e.g., when renewables are available), BESS helps reduce carbon footprints in both grid and off-grid applications.

The main use cases include:

• Energy arbitrage: Buying electricity during off-peak hours and selling it during peak demand.
• Grid services: Frequency regulation, voltage support, and reserve capacity to maintain grid stability.
• Backup power: Providing backup power during grid outages for homes, businesses, and critical infrastructure.
• Renewable integration: Maximizing the use of renewable energy by storing and dispatching it as needed.

The BESS market is expected to grow rapidly due to the increasing need for grid flexibility, renewable energy integration, and electrification of various sectors (e.g., transportation). Declining battery costs, advances in technology, and supportive government policies are driving this growth. Market projections suggest significant expansion in both utility-scale and residential BESS installations globally over the coming decade.