James Mountain, sales and marketing director at Fire Shield Systems Ltd, explores the current regulations and best practice informing how lithium-ion batteries are being used for energy storage; from the way they’re manufactured, stored, transported, installed and used, including the implications of their adoption for building design, fire prevention and fire suppression.
The UK’s transition from fossil fuels to renewable energy sources is promoting large scale energy storage adoption. Lithium-ion batteries have a key role to play in our decarbonised future, however, they present unique challenges when it comes to fire safety. Managing these challenges effectively is essential to protect people, businesses, assets and the surrounding environment.
The global shift towards renewable energy sources has resulted in increased reliance on battery energy storage systems (BESSs). A key benefit of these systems is their ability to store energy to smooth out the energy supply from renewable energy systems when power input is low, such as the storage of solar power for nighttime use or wind power for calm weather conditions, for example. This can mean a large quantity of energy is stored within the BESS at any one time, which can present a number of significant fire risks that require unique protection solutions.
The risks for BESSs
BESSs can include a number of different battery types – most notably lithium-ion (Li-ion).
The common fire risks associated with battery storage include:
- Thermal runaway: Often caused by Li-ion battery defects or damage, which results in excess heat, leading to fires or explosions.
- Failure of control systems: Failure in the systems can result in overheating, which can cause fires.
- Hydrogen evolution: For lead-acid batteries, excess hydrogen can increase risk of fires and explosion if suitable ventilation methods are not in place.
More often than not, BESSs use Li-ion batteries as they are well suited to the application, due to their high energy density and ability to fully discharge without impacting the longevity of the battery.
What are the risks associated with Li-ion batteries?
The main risk when using lithium-ion battery technology for BESSs is thermal runaway, where excessive heat keeps creating more heat, which can be caused by internal cell defects, mechanical failures/damage or overvoltage. These causes lead to high temperatures, gas build-up and potential explosive rupture of the battery cell, resulting in fire and/or explosion. Without disconnection, thermal runaway can spread between cells.
When such fires occur, they are often very intense and difficult to control. They can take days or even weeks to extinguish properly, and residual energy in the system can also cause electric shocks even after the fire has been extinguished. As a result of these risks, once a battery is in thermal runaway, it is often contained and left to burn itself out, leading to loss of the whole system.
However, as BESSs are being rapidly adopted across a range of industries and buildings, managing these risks is increasingly challenging. Many buyers – ranging from developers, local authorities and education establishments, through to industrial and commercial building owners – are not experts in energy systems or aware of the potential hazards and dangers the systems pose.
Similarly, site selection is often based on available space, rather than wider considerations around controlling and managing risks effectively. For businesses to protect their people, buildings and assets, buyers must understand the system’s requirements, follow the manufacturer’s guidance exactly and consult expertise where needed.
Several safety standards have been developed internationally for energy storage systems and large format Li-ion batteries. Organisations and companies, such as International Electrotechnical Commission, Underwriters Laboratories, National Fire Protection Association (NFPA) and Verband Deutscher Elektrotechniker, have led the work to develop design, testing and installation requirements. The NFPA’s standard for the installation of energy storage systems is one of the key standards to come out of this work.
The UK’s existing safety guidance for BESSs is covered by a range of regulations and requirements surrounding electrical installation, grid connectivity, product safety and dangerous goods.
Any electrical installation that the public will come into contact with as part of their day to day lives must comply with the Institute of Engineering and Technology’s (IET) wiring regulations (BS 7671).
However, this currently has no separate chapter pertaining to the installation of electrical energy storage systems. For domestic installations, BS 7671 doesn’t incorporate specific requirements or locations for domestic BESSs. In 2017, IET published a further guidance document with a view to set best practice for these installations.
Product safety and dangerous goods regulatory requirements
Each subsystem of the BESS should comply to applicable product safety directives, such as:
- General product safety directive (as applicable)
- Low voltage directive (between 50 and 1,000 V for AC, 75 and 1500 V for DC)
- EMC directive
In addition, dangerous goods regulations require that lithium-ion batteries should be tested according to UN Manual of Tests and Criteria section 38.3 to be able to be transported.
Reducing the risk
Despite legislation surrounding BESS fire prevention and protection existing, it can be challenging to determine exactly how to mitigate the associated fire risk for individual applications.
To make sense of the existing guidance, it can be broken down into three categories – system design, site considerations and fire protection systems.
- System design
A crucial consideration for reducing fire risk in BESSs are the materials used as part of the system itself. For example, the insulation of the container should be made using non-combustible materials where possible. Additionally, the system should include a ventilation system to minimise the risk of overheating.
- Site considerations
Consideration should also be given to the overall design of the site at which the BESS is located, as well as the separation of battery containers and other major equipment, such as transformers, inverters and substations. Where it isn’t possible to keep electrical systems entirely separate, fire walls can be installed.
Fire walls are generally made of concrete or composite materials, positioned between containers to significantly reduce the risk of fire spread. For insurers, fire walls are seen as an excellent fire prevention method, and will often result in lower premiums.
- Fire protection systems
For BESSs, implementing a fire detection and suppression system that is unique to the site and its individual uses and requirements is key for ensuring optimum safety. The system should consider:
- How the batteries will be separated
- The use of dedicated fire areas
- The type of detection and suppression system that should be installed to account for a site’s individual risks
- How these systems should be tested
- Information for firefighters, typically involving the fire service or fire engineering expertise in planning for an emergency response
As the costs for these systems come down and their adoption more widespread, it must be recognised that attention to detail will not just shape the future performance and reliability of such systems, but it will also impact public confidence in their widespread use.