Renewable energy sources, such as solar and wind, are projected to generate 44% of all power in the U.S. by 2050, which is increasing the need for battery energy storage systems (BESS).1
BESS are electrochemical devices that collect energy from a power grid, power plant or renewable source, hold it, and then discharge that energy later to provide electricity on demand.
“A BESS does not itself create or produce energy, it is a storage system. The energy is produced by other means, including different types of renewable sources. Think of a cellphone – you charge it overnight and then it runs throughout the day off that battery power,” says Stacie Prescott, head of energy for middle and large commercial at The Hartford.
The popularity of BESS is easy to understand: It’s renewable, relatively low cost to install, resilient, efficient and quickly transfers energy from charge to discharge as needed.
“When battery energy storage systems first showed up on the market over a decade ago, they were primarily in power generation settings. We are now seeing them expand to commercial and homeowner operations, as well as in retail, like the large box stores or warehouses, and data centers,” says Kenneth Travers, risk engineering technical manager, property and product at The Hartford.
Despite its benefits, BESS do present certain hazards, including fire risk associated with battery electrolyte chemicals.
What are the Risks of BESS?
There are potential hazards, including electrical-related failures, electrocution, combustible gas release and explosion. Most BESS units today are powered by lithium-Ion batteries. Initially used for smaller electronic products, these batteries have grown in popularity due to their power density advantage. When a BESS relies on lithium-ion batteries, the added hazards of thermal runway are higher.
Other risks include:
- Mechanical Abuse/Damage: This can be caused by the battery pack or package being dropped in the manufacturing process, during shipment or in handling.
- Manufacturing Defect: This can create conditions which may make a particular battery cell prone to short circuit during use.
- Excessive Battery Overcharging: Lithium-ion batteries are prone to overheating which can occur when batteries are left on charging units for an excessive period of time.
- Short Circuits: This condition can be caused by poor design, sub-standard manufacturing, product defect or physical damage.
BESS are susceptible to mechanical and electrical breakdowns, which can render the system non-operational. They can be vulnerable to damage caused by poor handling or improper installation.
“When the lithium-ion batteries are used in BESS, there is an increased risk of thermal runaway which is a phenomenon where the battery itself releases flammable gas when it overheats, or suffers a short circuit, causing the cell to fail and produce excessive heat and combustible gases. The batteries themselves are subject to different types of damage and failure. This failure process is driven by physical damage, manufacturing defects, short circuits and excessive battery overcharge,” says Travers.
Reducing Risk of Fire Loss Due to BESS Misuse
Risk from fires can be reduced by adhering to the National Fire Protection Association NFPA 855 standards for all new BESS installations.
“The industry released NFPA standard 855, in 2020, which apply to the design, construction, operation maintenance and installation of BESS. That standard followed the research from the NFPA’s Property insurance Research Group (PIRG) due to the significant fire hazard with lithium-ion batteries. The goal of these standards is to reduce potential risk associated with the use of Battery Energy Storage Systems,” says Travers.
Best Practices for Installing BESS Containers
- Site all new BESS containers on the exterior of critical buildings, configured at a minimum of 25 feet from the nearest exterior wall or roof overhang and not in line with any building openings such as windows, doors and vents for a horizontal distance of 25 feet from the far edge of the container.
- Place additional BESS containers at a minimum distance of 10 feet between other battery energy storage system units/containers.
- When BESS units must be placed in closer proximity to a critical building or adjacent storage units, enhance the exterior wall to meet a 2-hour fire resistance rated assembly complete with 90-minute fire rated doors or windows.
- When BESS units must be placed in closer proximity to adjacent storage units, provide a 2-hour concrete fire wall between the unit and structure, and extend past each end horizontally by half the width of the largest container and extend vertically above the height of the container by a minimum of 3 feet.
Outfit BESS With Proper Exhaust Ventilation
Install exhaust ventilation to release off-gasses caused by a developing lithium-ion battery fire, and to reduce potential for excessive heat which can lead to thermal runaway–mechanical ventilation of not less than 1 cubic foot per minute.
BESS configured within small rooms, enclosures, or containers where flammable gas can exceed 25% of the lower flammable limit (LFL) should be protected with either explosion suppression or deflagration venting designed and installed within requirements of NFPA 69 Standard on Explosion Prevention Systems and NFPA 68 Standard on Explosion Protection by Deflagration Venting.
Install Proper Detection Systems
It is important to install continuous gas detection within the enclosure which would activate the mechanical exhaust system upon detection of methane, benzene, ethane, ethylene, hydrogen, hydrogen sulfide and carbon monoxide, all of which are common off-gases from an early thermal runaway event.
For larger capacity units, you can integrate smoke and fire detection, in accord with NFPA 72, using very early warning smoke detection (VESDA) or radiant-type detection within the container.
Install Sprinkler Protection Systems
Where strong water supply exists, consider protecting larger BESS capacity units with automatic fire sprinkler protection to enable adequate cooling and reduce the potential for the battery arrays from reaching thermal runaway. Alternatively, some BESS units are now available with a pre-piped deluge sprinkler system with a connection on the unit exterior which enables the responding fire department to connect and provide the water supply for the deluge system.
Where sprinkler protection is not feasible, BESS can be protected with an approved clean agent fire suppression system to control lithium-ion battery fires through reduction of oxygen in an enclosed and unoccupied space.
Follow National Standard Electrical Guidelines
All electrical wiring, lighting and components incorporated within portions of the BESS enclosure should be designed and installed for a hazardous location in accord with Article 500 of NFPA 72, National Electrical Code.
Set Up Proper Inspection For All BESS
Follow NFPA 855 requirements for inspection, testing and maintenance of battery energy storage system units. Assure that each unit is de-energized and a system-off inspection is conducted at least annually on all components within the BESS.
Assure that a system shut-off inspection includes a check of:
- All equipment and components
- Spacing between racks, cabinets and trays
- Equipment grounding conductors
- Battery modules and arrays
- Connections and terminations
- Monitoring and charge control
- Disconnecting means
- Interconnection with other energy sources
“This technology is expanding quickly. Developers and power plant owners all plan to increase utility scale battery capacity over the coming years and the goal is a large one: to reach 30 gigawatts by 2025. Because of this, you must stay educated on how to properly implement and use this technology,” says Prescott.
For more risk management strategies, download our TIPS paper on fire hazards of battery energy storage systems.
1 “EIA projects that renewable generation will supply 44% of U.S. electricity by 2050,” U.S. Energy Information Administration, November 2023
La información proporcionada en estos materiales brinda información general y de asesoría. It shall not be considered legal advice. The Hartford does not warrant that the implementation of any view or recommendation contained herein will: (i) result in the elimination of any unsafe conditions at your business locations or with respect to your business operations; or (ii) be an appropriate legal or business practice. The Hartford assumes no responsibility for the control or correction of hazards or legal compliance with respect to your business practices, and the views and recommendations contained herein shall not constitute our undertaking, on your behalf or for the benefit of others, to determine or warrant that your business premises, locations or operations are safe or healthful, or are in compliance with any law, rule or regulation. Readers seeking to resolve specific safety, legal or business issues or concerns related to the information provided in these materials should consult their safety consultant, attorney or business advisors. All information and representations contained herein are as of November 2023.
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