Communicating battery safety

Bloomberg is forecasting a 15-fold increase in energy storage globally by 2030, representing 387 GW/1143 GWh of new energy storage capacity (Figure 1).¹ There are a wide range of storage technologies aiming to meet this demand, including compressed air, thermal energy, and gravity-based storage. However, BESS using lithium iron phosphate batteries (LFP) and nickel manganese cobalt (NMC) technology are predicted to deliver the majority of new storage capacity in the coming decade.

Australia, China, the UK, and the US are among the first movers in battery storage deployments. In the UK, battery storage is expected to deliver 24 GW of its 2030 target of 30 GW installed storage capacity, a ten-fold increase on today’s BESS installed base of 2.1 GW.²

In many regions of the world, governments are advocating for BESS installations and putting ambitious targets in place in order to support the transition to renewable energy sources. However, growing public concern about the safety of lithium-ion-based battery storage projects threatens to delay (or even derail) projects.

The risk of thermal runaway in lithium-ion batteries is well-documented, and much has been learned from previous safety incidents. Tier one BESS manufacturers have invested significantly in incorporating new safety features into hardware and software. International standards have been updated, and testing regimes are more rigorous.

However, despite these efforts, there is still a lack of a comprehensive and industry-wide narrative regarding the safety of large scale battery systems. As a result, it can be a significant challenge to communicate these efforts and reassure local communities, politicians and planning authorities about the safety of grid scale battery systems.

What are the safety risks with battery storage?

The primary risk is fire. The process leading to a lithium-ion battery catching fire is called thermal runaway. Thermal runaway is an uncontrolled exothermic reaction that raises cell temperature and can propagate between cells, occurring when a cell achieves elevated temperatures. Thermal runaway can be triggered by various factors, such as: mechanical and electrical breakdown, thermal failure, and internal/external short-circuiting or electrochemical abuse.

The risks to public safety from a battery unit catching fire are threefold:

• The potential for explosion due to the build-up of flammable gases within a battery unit.
• Fire and the presence of toxic gases in the smoke plume from a fire.
• The contamination of water used to tackle a fire and the possibility of this water getting into local water supplies.

How prevalent are battery safety incidents?

Despite high-profile media reporting, there have been relatively few safety incidents at battery energy storage facilities.

A recent report from Pacific Northwest National Laboratory (PNNL), aimed at educating local planners, cited 14 safety incidents at grid-connected BESS facilities in the US.³ None of the incidents led to a loss of life. For context, there are 491 utility scale projects operational in the US.

In the UK, there are more than 100 grid-connected BESS in operation, with a total energy storage capacity of close to 3 GWh. There has been one reported UK BESS fire that required Fire & Rescue Service (FRS) attendance, in Liverpool, in September 2020. The fire was contained and there was no third-party collateral damage or injury to firefighters or the public. For context, this equates to one incident in almost 550 years of combined operation across UK projects.

How can safe battery energy storage facilities be ensured?

The UK National Fire Chiefs Council (NFCC)⁴ guidance and the National Fire Protection Agency (NFPA)5 international standards have specified requirements on the technology characteristics, design, and operation of utility scale battery energy storage facilities. There is some variation between UK and US guidance, so Clearstone’s battery safety standards merge elements of both to ensure compliance with both and comprehensiveness.

There are a number of standards aimed at ensuring that battery units are designed in a way that minimises the risk of thermal runaway and limits propagation if an incident happens.

One of the key ones is UL 9450a testing. Battery units are fire tested to confirm the effectiveness of fire suppression systems and design features at preventing thermal runaway from spreading from one BESS unit to adjacent ones. UL 9450a certification is a requirement in many jurisdictions and any technology provider under consideration for a project should be able to provide certification and testing data to support it.

Additionally, facility design guidelines include safe distances from battery units to site boundaries, public footpaths, and occupied buildings to ensure that the public is protected in a fire situation, enhancing the safety of the overall BESS.

Gases being given off by battery cells is an early indicator that a thermal runaway event is occurring, so early detection of gases is critical before a build-up can become volatile. A competent battery management system (BMS) and integrated battery assembly will identify, control, and eliminate potential risk scenarios through:

• Monitoring and sensor systems which can detect gases, such as methane and hydrogen.
• Fire detection systems which are industry standard certified, such as NFPA855 or equivalent.
• Ventilation systems which are able to remove flammable gas to prevent a build-up which could result in explosion.
• Temperature and moisture management systems which can maintain the optimum conditions for the batteries.

Thought also needs to be given to water containment in the design of drainage systems. These systems should be able to contain firefighting water on site and isolate it from public water courses and sewers in case of a fire. Once the incident has been safely brought under control, the water will need to be removed and treated.

For project developers who are familiar with design guidelines and technical standards, much of this will be straight forward to incorporate into project proposals. However, assistance may be required with regard to developing a project in collaboration with local fire services, providing risk assessments and emergency response planning.

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