A catastrophic fire at what would be the UK's biggest solar farm could see the air filled with toxic gas as far as six miles away, an expert in biochemical engineering has warned.

Dr Bruno Erasin says a blaze at a huge battery storage unit forming part of the planned development on the outskirts of Faversham would pose a “significant risk” to the surrounding population.

He has now urged government planning chiefs to order the solar park be built no closer than 15km from the nearest home.

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Currently, a number of houses back onto the 1,200-acre site in Graveney, which would contain 880,000 solar panels and a number of battery units to store the energy they generate.

Dr Erasin says evidence shows a fire at the storage site - which covers 25 acres itself - could be explosive, difficult to control and send toxic hydrogen fluoride into the air.

Humans exposed to the toxic gas in high doses can suffer serious burns and serious damage to their respiratory systems.

With the exact size of the proposed Cleve Hill battery yet to be revealed, Dr Erasin has modelled his data on a 10,000kWh storage system.

In his report - based on hydrogen fluoride being released from a fire for an hour - he says concentrations in the air 4.5km away could be 2,444 times higher than derived domestic exposure limits.

Even 10km away, data modelling predicts readings 55 times higher.

Dr Erasin writes: “There are well-documented significant risks associated with large-scale energy storage units, including the risk of fire, and leaching of heavy metals into the environment during catastrophic events.

“In 2018 AIG Energy Industry Group reviewed lithium-ion battery energy storage systems and commented that ‘battery fires are often very intense and difficult to control. They can take days or even weeks to extinguish properly’.

“Based on this preliminary assessment using various scenarios and assumptions, it is concluded that the risk to human health in a catastrophic fire event of a 10,000kWh battery storage system is very significant and in my opinion not acceptable to potentially expose a large number of residents in the close vicinity of the proposed development at Cleve Hill Solar Park.

“The population both in the easterly direction of the development and westerly/south westerly direction of the development may be exposed to unacceptable risks including residents at Seasalter, Graveney, Faversham and Whitstable.”

As well as the risks of a fire, Dr Erasin’s report talks of the potential disastrous effects of severe flooding at the site.

In it he says there is the potential to release dangerous levels of copper and nickel into the water should the unit be submerged at 20 inches for between 12 and 24 hours, harming surrounding wildlife and fauna.

While developers plan to install a protective bund around the site, Dr Erasin says these have failed in previous cases.

He writes: “Based on this preliminary scenario, which would have to be further developed and verified, a preliminary conclusion can be drawn that the proposed battery storage systems at the Cleve Hill Solar Park could cause a foreseeable and significant environmental risk.”

Lut Stewart, whose garden is just 10 metres away from the solar farm site, says Dr Erasin’s findings are “extremely concerning”.

"Battery fires are often very intense and difficult to control. They can take days or even weeks to extinguish properly" - Dr Bruno Erasin

“Of course we’re worried,” she said. “Given the concentrations 4.5km away, it would be catastrophic for those of us who live in the village.

“I have a small lithium battery in my mobility scooter which I’m not allowed to take on planes because it’s deemed to be explosive, so I don’t like to think of what could happen on a 25-acre site full of them. We’d have no hope.”

Dr Erasin’s report has been submitted to the Planning Inspectorate, which is considering the application for the solar park as part of a Development Consent Order, given its size and national significance.

Such a process removes planning powers from the local authority, with the Inspectorate instead making a recommendation to the energy secretary, Greg Clark, who will make a final decision.

Dr Erasin says the Inspectorate should not ignore the likelihood of catastrophic events such as fires and floods, given the 40-year operational period of the solar park.

The Faversham Society has also called for an Issue Specific Hearing to address concerns about the battery energy storage site.

Cleve Hill Solar Park Ltd says it is working on the battery storage plans with Swiss firm, Leclanché SA - a world leader in the industry.

A spokesman said: “Both the developers and the Swiss battery specialist put the safety of communities and their workforce at the heart of their designs and believe it is absolutely right to be scrutinised on the safety of the development.

“Cleve Hill Solar Park Ltd and Leclanché are designing an Outline Safety Management Plan which will be consulted on with the Kent Fire and Rescue Department and further assessed by the Planning Inspectorate as part of the ongoing examination for the scheme.”

Daniel Föhr, vice-president of system enginerring at Leclanché, added: “As a battery system manufacturer with over 100 years’ experience of providing high-quality energy storage solutions internationally, we design every solution to ensure we achieve the very highest levels of safety for both people and the wider environment.”

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