BESS installations are growing rapidly across the UK. This guide covers thermal runaway prevention, fire detection, suppression, and planning considerations for grid-scale battery storage.. The BESS Revolution Battery Energy Storage Systems are a critical component of the UK's transition to net zero. The National Grid ESO estimates that the UK will need 30 GW of battery storage by 2035 to balance renewable energy supply. However, the fire risks associated with large scale lithium ion battery installations demand specialist fire engineering expertise. UK BESS Fire Incidents Liverpool BESS fire (2020) — Carnegie Road facility, 6 containers involved Newhaven BESS fire (2021) — thermal runaway cascade in container battery system Multiple international incidents — Arizona, South Korea, Australia Frequency : approximately 1 significant BESS fire per 1,000 installations globally Key concern : toxic gas production (hydrogen fluoride) affecting surrounding communities Fire Risk Factors Thermal Runaway Cell failure — internal short circuit, overcharging, or external damage Exothermic reaction — temperature exceeds 150°C, accelerating chain reaction Gas production — electrolyte vaporisation producing flammable and toxic gases Cascade — heat transfer from failing cell to adjacent cells Re ignition — fires can re ignite hours or days after apparent extinguishment Contributing Factors Manufacturing defects — contamination during cell production Charging management — overcharging or charging at extreme temperatures Physical damage — impact, vibration, or water ingress Ageing — degradation increasing internal resistance and failure risk System design — inadequate cooling, insufficient cell spacing Detection Systems Technology What It Detects Response Time Cost Off gas detection Electrolyte vapour 5 15 minutes before thermal runaway Medium Thermal sensors Cell temperature anomalies Real time Low Smoke detection Smoke from cell failure After thermal runaway Low IR thermal imaging Hot spots on container surface Real time High Gas detection (HF) Hydrogen fluoride During/after thermal runaway Medium BMS monitoring Voltage/current anomalies Pre failure Included Suppression Strategy Water Based Systems Most effective for lithium ion battery fires (cooling mechanism) High volume — sustained water application for hours, not minutes Water supply — minimum 20,000 litres per container, 4 hours supply Drainage — contaminated water containment and treatment Environmental — preventing fluoride contaminated runoff Gas Based Systems Limited effectiveness — cannot cool cells below re ignition temperature May suppress flame but thermal runaway continues Not recommended as primary suppression for BESS Emerging Technologies Aerosol suppression — micro particles inhibiting combustion Immersion cooling — submerging cells in dielectric fluid Cell level isolation — physical barriers between individual cells Planning and Siting Separation Distances NFPA 855 (US) — minimum 3m between containers, 30m from occupied buildings UK (emerging guidance) — site specific fire engineering assessment required Environment Agency — pollution prevention requirements for water runoff HSE — COMAH regulations may apply for large installations Planning Conditions Fire risk assessment — submitted with planning application Emergency response plan — agreed with local fire service Environmental impact — toxic gas dispersion modelling Decommissioning plan — safe disposal of degraded batteries Community consultation — addressing public safety concerns Emergency Response 1. Automated shutdown — BMS disconnecting affected modules 2. Notification — automatic fire service alert with BESS specific information 3. Defensive strategy — fire service protecting exposures, allowing controlled burn 4. Toxic zone — establishing hot, warm, cold zones for hydrogen fluoride 5. Sustained cooling — water application for minimum 4 6 hours 6. Environmental protection — bunding and containment of contaminated water 7. Re ignition watch — 72 hour monitoring period post incident Magnus Opifex SEVEN LTD — UK's Leading Fire Safety & Fire Engineering Consultancy 🌐 magnus opifex.co.uk 📞 +44 7486 691724 ✉️ office@magnus opifex.co.uk Founders: Nicoleta Vasile, Baroness of Brattleby — CEO, Lawyer and Barrister, Legal & Administrative Director Alina — Technical Director & Expert Fire Engineer (BEng) Head Office: Ealing Cross, 85 Uxbridge Road, London W5 5BW Magnus Opifex SEVEN LTD delivers engineering led fire engineering, fire risk assessments, CFD modelling, and building safety consultancy across the United Kingdom and internationally. With over 20 years of combined experience and a UK portfolio spanning healthcare, residential and infrastructure, we bring truly engineered solutions with a personal touch. © 2026 Magnus Opifex SEVEN LTD. All rights reserved.