Are Battery Energy Storage Systems (BESS) Safe?

We’re pleased that the planning application for a huge 1500 MW battery energy storage system proposed for the Green Belt at Aldenham in Hertsmere Borough has been withdrawn by the developer.

Are large-scale Battery Energy Storage Systems (BESS) safe?  And where should they be located?

The proposed ‘Elstree Battery Energy Storage System’ (BESS) at Aldenham, at 1500 MW, would have been the largest battery system in the UK and among the largest in the world had it been built. But the planning application was highly controversial, attracting over 3,000 objections from local residents, community groups, the Parish Council and others.

Here at CPRE Hertfordshire we submitted our very strong objection to the original application and to subsequent amendments.

Among our concerns, the 12 hectare site is situated within the Green Belt. The proposal would have introduced a significant industrialisation of the Green Belt. And of course ‘the essential characteristics of Green Belts are their openness and their permanence’. (National Planning Policy Framework).

The site is currently open countryside and in productive agricultural use. There is also a well-utilised public right of way running through the site, and the villages of Letchmore Heath, Patchetts Green and Aldenham are all very close to the site. We believe there are no Very Special Circumstances that would justify this development in this particular location.

Safety, fire risk and thermal runaway

In addition to the above concerns, safety is of paramount importance. Specifically the risk of fire and thermal runaway. Thermal runaway is a self-sustaining chain reaction by which the fire spreads.

The BESS would have been comprised of hundreds of lithium-ion batteries, packed closely together in containers. Lithium-ion batteries can ignite or explode, thus initiating thermal runaway. Ignition can result from a number of factors, such as overheating, overcharging, external damage, inadequate ventilation, and electrical faults such as a short circuit or voltage imbalance. And the close proximity of the batteries in a BESS can contribute to the rapid expansion of a fire.

When thermal runaway occurs, toxic chemicals are released including Hydrogen Fluoride and Carbon Monoxide. Release of these chemicals can pose severe risk to emergency response teams and nearby communities, as exposure can lead to organ damage and could ultimately be fatal.

Thermal runaway incidents are not a theoretical concern. One study reported in PV Magazine documented over 50 significant incidents of fires and thermal runaway in BESS between 2018 and 2023. These included events in South Korea, the United States, Europe, and Australia.

One of the notable incidents occurred in Arizona in 2019. A cell defect in a battery at a 2 MW BESS caused thermal runaway, which then caused an explosion with serious injuries to firefighters and destruction of the entire BESS. Read more about this incident in Energy Storage News.

A BESS incident may require nearby local communities to shelter-in-place. In 2023, as reported by local media North Country Public Radio, a fire at a recently-constructed BESS facility in Lyme, New York prompted authorities to issue a shelter-in-place order for residents within a one-mile radius. Concerns included air quality impacts and the release of toxic materials as the fire continued to burn for several days.

Former MP and government minister Maria Miller has raised significant concerns about the safety of large-scale BESS in the UK. She has advocated for these facilities to be classified as “hazardous,” which would require mandatory consultations with the Environment Agency, Health and Safety Executive, and fire services during the planning stages. She has also called for a review of current and planned BESS installations to ensure they do not pose undue risks to residents or the environment, and that they are located appropriately to avoid harm to nearby communities.

The National Fire Chiefs Council (NFCC) has previously issued guidelines regarding BESS safety features. These include provisions for fire service access, water sources, and emergency response plans​. The NFCC is further revising its guidance on managing BESS-related risks to include requirements for safe site locations, expected for publication in 2025.

These efforts reflect a growing acknowledgment of the risks posed by BESS systems and the need to address public safety considerations.

For all of the above reasons, we believe it is very good news indeed that the developer has withdrawn their planning application for a huge BESS in this particular location.

Is there a Battery Energy Storage System (BESS) proposal near you?

Please get in touch to let us know, so we can monitor Hertfordshire BESS proposals through the planning system.