Battery storage fire risk at the planning stage

Battery storage fire safety planning evidence is now the single largest driver of layout on a grid-scale storage application. Determine the separation distances, the firewater supply and the containment volume, and the rest of the site plan follows. Get them wrong and the scheme comes back with a consultation response that cannot be answered without redesign.

Electricity storage in England, other than pumped hydro, is determined by the local planning authority whatever its capacity, so there is no nationally significant infrastructure route for a large battery site. The decision maker is a council planning committee advised by a case officer, a fire and rescue service and, where water is at risk, the Environment Agency.

Why fire dominates the consultation

The hazard is specific. A lithium-ion cell in thermal runaway generates its own heat and oxygen, producing flammable and toxic off-gas before any visible flame, and the event can propagate from cell to module to container. Water cools the surrounding structure but struggles to reach the inside of a pack, so suppression takes a long time and a large volume of water.

That changes what a fire service is assessing. On a conventional building they consider escape and firefighting access. On a storage site there are no occupants, so the questions become whether a fire can be contained within one unit, whether crews can work safely at a distance, what the off-gas plume does, and where the water goes afterwards.

Two points of honesty are worth building into the application. The published evidence base on failure rates in utility-scale installations is still developing, so an application should not lean on comparative statistics. And the design standards most commonly referenced in this field are not British planning documents, which means the application has to explain why the standard it relies on is appropriate rather than assuming the reader accepts it.

Separation distances and site layout

Separation is the primary control, and it works in three directions.

Between containers, so that a fire in one unit does not propagate to its neighbours. Distances are usually justified either by the manufacturer's large-scale fire testing data for the specific product or by reference to a recognised standard, and the application should say which basis it uses and attach the reasoning. A generic "units will be spaced in accordance with manufacturer's recommendations" is not an answer a consultee can assess.

Between the battery compound and the site boundary, which protects whatever lies beyond it. The distances expected increase where there are dwellings, occupied buildings, highways, overhead lines, watercourses or woodland nearby.

Between the batteries and the rest of the plant, including transformers, switchgear, the substation and any control building, so that a battery fire does not take out the equipment needed to isolate it.

Layout detail does a surprising amount of work here. Orienting container doors and vent paths away from each other and away from the boundary, keeping a clear internal ring road, avoiding long unbroken rows, and placing the compound on the part of the site furthest from sensitive receptors are all cost-free at concept stage.

Firewater supply and containment

This is where applications most often fall short, and the two halves are separate questions.

Supply means the volume of water available for firefighting and how it gets to the compound. Rural sites rarely have mains capacity, so the answer is usually a static tank, an open water source with a defined draw-off point, or a combination, with the volume justified rather than asserted and the draw-off point shown on a plan with hardstanding for an appliance.

Containment means what happens to that water once it has been used. Firewater from a battery fire carries contaminants, and allowing it to reach a watercourse or groundwater is a pollution incident. The design response is an impermeable surface under and around the compound, bunding or kerbs that direct flow to a retention feature, a penstock or valve to isolate the site drainage, and a retention volume sized on a stated firefighting duration.

A Drainage Strategy that treats firewater as a design case alongside the 1 in 100 year rainfall event is doing the job properly. One that covers surface water only, with firewater handled in a sentence, invites an objection from both the lead local flood authority and the Environment Agency. Source protection zones and sites draining to a sensitive catchment raise the bar further.

Access and standoff for the fire service

Fire and rescue services ask for access that lets an appliance reach the compound, turn, and stand at a distance from the units while working.

The practical requirements are an access road capable of carrying an appliance in all weather, a width and turning provision suitable for the service's vehicles, a hardstanding position at a stated standoff from the containers, and a second means of access on larger sites where one route could be blocked by the incident itself. Gates need to be openable by the service, and the access needs to remain usable when the site is unmanned, which is almost always.

The internal arrangement matters as much as the road. A compound where every unit can be approached from two sides is defensible. One where units sit in a block with a single aisle is not, and no amount of narrative will change that.

Emergency response planning before determination

A battery safety management plan or emergency response plan is the document that ties the physical design to what happens on the day, and the useful version of it is prepared before determination rather than left to a condition.

It should cover detection and alarm arrangements, remote monitoring and who receives the alarm, the automatic actions on detection including isolation of charging and discharge, the information available to the fire service on arrival, the tactical approach the service is expected to take, the site access arrangements out of hours, off-gas and plume considerations including any advice to nearby occupiers, post-incident management of the damaged units, and the containment and disposal of firewater.

Preparing it early has a procedural benefit. Where the fire and rescue service has reviewed and commented on a draft before the committee date, the officer report can record that engagement, and the condition that follows becomes a formality rather than an unresolved risk. A Fire Safety Strategy to recognised fire engineering standards is fire engineering work and should be prepared or reviewed by someone with the relevant competence.

A distinction worth making in the submission: the statutory fire statement regime applies to relevant higher-risk residential buildings at Planning Gateway One, so a Fire Statement in that formal sense is not what a storage site requires. The evidence is provided voluntarily because the consultee will ask for it, and saying so avoids a validation argument.

The evidence the fire authority expects

Across consultation responses on these schemes, the same list recurs.

1. Product-specific fire test evidence for the proposed battery system, with the separation distances derived from it.
2. A layout plan showing separation distances dimensioned to containers, boundaries, plant and sensitive receptors.
3. The firewater supply volume, source and draw-off arrangement.
4. The containment design, with the retention volume and the isolation arrangement.
5. Access and standoff drawings, with vehicle tracking.
6. A draft emergency response plan, ideally reviewed by the service before determination.
7. Confirmation of the decommissioning arrangements, since the end of life handling of cells is a hazard of its own.

Fire and rescue services are not generally statutory consultees on these applications, though they are consulted in practice on almost all of them, and the position has been under review. Check the current arrangement with the authority rather than assuming either way.

Conditions commonly imposed

Expect conditions requiring the battery safety management plan and emergency response plan to be approved before commissioning, in consultation with the fire and rescue service, and to be implemented and maintained for the life of the development. Expect the firewater containment and isolation details to be approved before the compound is constructed.

Three others are common and worth anticipating. A noise condition, because the thermal management plant runs continuously and a Noise Impact Assessment to BS 4142 is usually required for the nearest dwellings. A decommissioning condition with a scheme to be submitted before the end of the operational period. And a condition tying the installation to the approved battery technology, which is worth negotiating, because products change faster than planning permissions are implemented and an over-tight condition forces a section 73 application later.

You can see which reports an energy storage scheme is likely to need and draft the planning documents from your own site details, then have the fire engineering and containment design prepared by competent professionals.

For specialist technical reports, qualified professional input may be required. This is general guidance, not legal advice, and consultation arrangements for storage schemes continue to develop. Check the current position with your local planning authority and fire and rescue service before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.