Ensuring Safe Energy Storage – The U.K. Issues Guidance for Grid-Scale Battery Systems

Introduction

The rapid increase in deployments of lithium-ion battery energy storage systems (BESS) has been accompanied by an increase in incidents involving these units. In response to these events, numerous organizations—both in the U.K. and internationally—have issued standards in an effort to make the energy-storage industry safer.

In an effort to help BESS operators and other stakeholders navigate the terrain where there are so many standards, the U.K. Department for Energy Security and Net Zero has issued Health and Safety in Grid-Scale Electrical Energy Storage Systems (hereinafter “the Guidance”).

The Guidance is intended to distill the various standards and other related documents which have been published relative to BESSs into a concise document which establishes best practices and functional health and safety measures throughout the lifecycle of a BESS. Further, it provides a holistic framework for BESS safety from the origination of the project until decommissioning.

In this article, we will focus on the aspects related to the use of sensors to monitor system health, detection of emerging problems, and finally, effective fire suppression. We will also provide valuable insight into the gold standard of BESS protection based on an integrated system which prevents hazards, detects them at the earliest onset, and provides effective fire suppression when conditions escalate too rapidly for mitigating interventions.

Guidance Scope & Structure

The Guidance is aimed at grid-scale, lithium-ion BESSs (generally defined as installations of 1 MW or greater), with an emphasis on health and safety and the prevention of BESS incidents. It should be noted that the Guidance is non-exhaustive and does not assert itself as a prescriptive document.

The following stages of a BESS lifecycle are covered in the Guidance:

• Design & Planning
  Outlines key considerations for equipment design, site appraisal, risk reduction, and emergency response planning at the early project stage
• Transportation
  Provides guidance on managing health and safety risks during the movement of battery storage equipment between locations
• Installation & Commissioning
  Covers the safe installation, connection, inspection, testing, operator training, and system handover of the BESS, including the post-handover bedding-in period
• Operation & Maintenance
  Details safe operational practices, routine inspection, testing, and the use of a continuous improvement cycle for BESSs
• Decommissioning & End-of-Life
  Describes health and safety measures for permanent system shutdown, removal, site restoration, and regulatory-compliant recycling or disposal

Hazards of BESSs

Appendix B of the Guidance provides a comprehensive listing of BESS hazards. The most predominant hazards and their initiating events are summarized below:

Health & Safety Recommendations

Most of the health and safety recommendations relating to the use of sensors to monitor system health, detection of emerging problems, and fire suppression are found in the Design & Planning section of the Guidance and the respective subsections as described below.

Within the Battery System subsection, a robust monitoring and detection system is recommended which monitors the operating conditions within the enclosure and provides early detection of combustible electrolyte vapors during battery failure.

In the Balance of Plant subsection, monitoring, fire detection, and fire suppression are central components. The Guidance states: “The selection of appropriate equipment for hazard mitigation can have a significant impact on overall system risk.”

A key recommendation is, again, monitoring and detection equipment which alerts operators to emerging hazards. This should include sensors that detect off-gassing from battery modules, heat-detection sensors, and smoke detectors. The sensors should be configured such that operators and/or local emergency services are notified of the developing incident.

In terms of fire suppression, the Guidance advocates that consideration should be given at both enclosure level and the site as a whole. The options listed are water-based fire or aerosol systems. It also notes that “water-based systems are considered more effective than gaseous systems for fires involving battery cell modules.”

The use of water-based fire suppression systems is based on a report from the National Fire Chiefs Council (NFCC) which offers guidance to the U.K.’s fire and rescue services for pre-planning incidents involving BESSs. The use of water-based systems as described in the NFCC document is intended to “help prevent or limit propagation between modules,” and acknowledges that “there is currently no way to extinguish an ESS fire with sprinklers.” So, the premise is to let the affected enclosure burn itself out in a controlled manner.

The NFCC guidance highlights an FM Global report^[i] which asserts that gaseous (clean agent) systems have not been proven effective at extinguishing fires in BESS enclosures and are therefore not a recommended option. The NFCC guidance also places a high value on the use of monitoring and detection sensors to provide early awareness of developing issues.

The Balance of Plant subsection goes on to support the use of sensor-activated ventilation systems to prevent the accumulation of combustible gases within the enclosure. It also promotes security measures such as motion and door sensors that alert operators to unauthorized entry into the enclosure which can compromise the safety of BESS installations.

Emergency Planning is also a major subsection within Design & Planning. It promotes the development of an emergency response plan (ERP) which addresses:

• Fire incidents
• Management of HazMat (e.g., runoff, smoke, etc.)
• Access to the site
• Security incidents

Once an ERP is developed, Emergency Planning advises that it should be shared with local emergency services and a copy maintained on site at all times.

The Operations & Maintenance section, in its subsection Safe Operation, advocates for a robust monitoring and detection system to ensure that operating conditions are safe and to provide early warning for developing problems. It also supports the use of security sensors to guard against unauthorized access.

In the Emergency Response Planning subsection, the guidance recommends that the ERP be regularly reviewed and updated. It also advises that employees should be trained on the ERP and for the testing / inspection of safety equipment such as sensors, alarms, and fire suppression systems.

The Role of Standards in BESS Fire Protection

Standards play a critical role in ensuring that fire protection for BESS installations is effective, consistent, and aligned with best practices across jurisdictions. They provide the technical foundation for designing, testing, installing, and maintaining systems in a way that mitigates fire risk at every lifecycle stage.

The Guidance provides a comprehensive listing of all applicable standards. The key fire-related standards include:

• NFPA 855 – The National Fire Protection Association’s standard specifically for stationary energy storage systems. It outlines fire safety requirements for location, separation distances, ventilation, gas detection, fire suppression, and emergency planning. NFPA 855 also requires compliance with other key testing standards, including UL 9540 and 9540A.
• UL 9540A – A critical test method used to evaluate thermal runaway and fire propagation behavior in BESS under worst-case failure conditions. The results inform decisions about container spacing, suppression system selection, and hazard zoning.
• IEC 62619 / IEC 62933 – These international standards set electrical and thermal safety requirements for lithium-ion cells and BESS installations, including resistance to overcharge, short circuit, crush, and fire exposure.
• BS EN 60079 – Addresses protection of electrical equipment in explosive atmospheres, relevant where off-gassed flammable vapors may accumulate during battery failure or venting.

UltraSense^™ Sensors & Stat-X^®: The Gold Standard in BESS Protection

The U.K.’s guidance document stands in clear support of a comprehensive monitoring system to provide early warning of developing issues while also advocating for condensed aerosol fire suppression systems. With UltraSense sensors and Stat-X condensed aerosol suppression units, BESS operators can be assured that their battery enclosures are protected by a tiered strategy which provides prevention of problems, early detection should they occur, and an effective fire suppression system.

Prevention

VOC / Temp/ Humidity Sensor

No one would argue that the best way to manage BESS incidents is to prevent them from occurring. This includes being aware of the operating conditions inside of the battery enclosure. UltraSense sensors provide continuous, real-time monitoring of the environment including:

• Temperature
• Humidity
• Dust/ particulates
• Air quality (e.g., corrosiveness))
• Vibration

When conditions reach a predetermined threshold, the system alerts operators to the issue, allowing them to take corrective action long before a more serious problem occurs.

Detection

Photoelectric Smoke Sensor

As important as prevention is, there are other situations—such as module failure and electrical faults—which can develop outside of the prevention parameters. In these scenarios, it is crucial to have a suite of detectors to provide the earliest possible notification of the emerging risk(s). Depending on the system logic, when UltraSense detectors activate, they can self-initiate mitigation measures while also sending alarms to operators and/or maintenance personnel.

UltraSense has almost every possible angle covered with our lineup of detection sensors which include:

• IR thermography to detect the smallest increase in equipment temperature
• Equipment surface temperature
• Volatile organic compounds and hydrogen
• Hydrogen fluoride
• Combustible gases
• Air-aspirating and photoelectric smoke detection
• Water ingress

Motion Sensor

The Guidance also suggests security sensors to guard against unauthorized entry into BESS enclosures. Once again, UltraSense has this covered with the following security sensors:

• Door contact
• Motion
• Noise

Suppression

As suggested in the Guidance, condensed aerosol is emerging as the preferred suppression agent for BESS systems because it directly tackles the fire risks inherent to high-energy, confined environments. Stat-X’s proprietary, potassium-based aerosol extinguishes flames at the chemical level and remains suspended long enough to prevent re-ignition.

Stat-X Condensed Aerosol Generator

Compact and modular, Stat-X units require no plumbing, pressurization, or costly infrastructure upgrades. This allows them to be installed directly inside BESS containers where space is limited and fast, total-flooding suppression is essential. The generators are virtually maintenance-free, have a 15-year service life, and significantly reduce long-term ownership costs.

When integrated with UltraSense detection sensors, Stat-X can be automatically activated at the earliest signs of danger. Beyond performance, Stat-X is exceptionally safe: it is non-conductive, suitable for use around sensitive electrical equipment or occupied areas and carries no ozone-depletion or global-warming potential—ensuring both environmental responsibility and regulatory peace of mind.

In Conclusion

The U.K.’s health and safety guidance for grid-scale BESSs underscores a clear reality: fire is the most critical hazard which operators must address. While design, planning, and operational discipline can reduce risks, effective protection ultimately depends on layered safeguards—comprehensive monitoring, early detection of anomalies, and proven suppression technologies that can stop an incident before it escalates. By aligning with established standards such as NFPA 855, UL 9540A, and IEC 62619, operators can build systems that not only comply with regulations but also safeguard people, assets, and the surrounding environment.

With this in mind, UltraSense sensors and Stat-X condensed aerosol suppression represent the gold standard in BESS protection. UltraSense provides real-time visibility into environmental and operational conditions, detecting thermal, chemical, and mechanical risks at their earliest stage.

When paired with Stat-X, which delivers fast and effective fire suppression in confined electrical environments, operators gain a fully integrated safety net—one that prevents hazards, identifies them the moment they arise, and suppresses fires decisively if they occur. Together, these technologies embody the proactive, standards-aligned approach to fire protection that the U.K. guidance calls for, ensuring that the growth of energy storage is matched by an equally robust commitment to safety.