Comprehensive report validates early fire detection for solar PV arrays

The Photovoltaic Array Overheat and Fire Detection Report presents the results of rigorous, real-world testing of Thermocable’s own ProReact Linear Heat Detection (LHD) systems, demonstrating their ability to deliver ultra-fast and reliable early warning of overheating and fire hazards in both rooftop and ground-mounted solar PV environments.

This independent study represents a significant milestone for the renewable energy sector, providing actionable insights for safer and more resilient solar infrastructure worldwide.

Scalable and reliable

Thermocable ProReact LHD offers a highly scalable and reliable early fire detection solution for solar PV systems. Fully approved to EN 54 standards and UL listed as a heat-automatic fire detector, ProReact LHD continuously monitors temperature changes along its entire length, enabling early the identification of overheating panels and potential fire risks.

With low installation costs, minimal effort and seamless integration into existing systems, ProReact provides a cost-effective and high-performance alternative to conventional fire detection technologies, in turn enhancing safety, protecting assets and ensuring rapid response to hazardous conditions in PV environments.

Rising importance

As the world shifts towards cleaner energy, solar power has become one of the fastest growing and most accessible renewable energy sources. PV systems are increasingly being deployed on rooftops, integrated into building designs and installed in ground-mounted arrays, particularly so across commercial, industrial and high-value sites.

However, like any electrical system, solar PV installations come with inherent fire risks. Faulty panels, overheated wiring, damaged connectors or poor quality components can lead to system failures, performance degradation and, in some cases, electrical fires. These risks are particularly concerning in sensitive environments such as Data Centres, where a rooftop fire could damage critical infrastructure, disrupt operations and result in significant financial losses.

Rooftop fires also pose unique challenges for emergency response teams. Smoke can be drawn into HVAC systems and spread throughout the building, setting off multiple alarms, triggering evacuations and making it more difficult to locate and contain the source, while giving the fire more time to escalate.

As solar adoption accelerates, it’s essential that fire detection and risk mitigation strategies evolve in step. Proactive and early-stage fire detection is critical not only to safeguard assets and infrastructure, but also to ensure the safety of building occupants and first responders alike.

Common PV fire safety risks

Wiring and electrical failures can result from poor installation, damaged cables or loose connections. These issues may lead to arcing, short circuits and overheating: all common triggers for electrical fires within solar PV systems.

Inverter malfunctions pose a large risk, being responsible for converting DC electricity to AC. When inverters overheat or operate with faults, they can become ignition points.

Battery storage systems add another layer of risk. Batteries can experience thermal runaway, electrical shorts or electrolyte leakage, all of which are potential fire hazards.

Overheating and panel hotspots can develop due to dust, debris or shading that disrupts panel performance. These localised temperature spikes increase the likelihood of fire.

Combustible roofing materials such as wood, bitumen-based products or certain types of insulation can significantly accelerate the spread of fire once ignited, thereby increasing the risk to both the structure and its occupants.

Environmental factors including extreme heat, lightning storms, dust build-up and vegetation debris increase the risk of external ignition.

Environmental conditions

Accessibility and obstructions can render the inspection and maintenance of fire detection equipment difficult. PV panels, mounting hardware and cabling often block or reduce the visibility of traditional detectors like smoke or flame sensors, reducing their sensitivity and effectiveness.

Environmental conditions such as temperature extremes, humidity, dust and debris can diminish the sensitivity and reliability of conventional fire detectors, highlighting the need for robust solutions designed to withstand harsh outdoor environments without compromising performance.

System integration requirements demand fire detection solutions that can seamlessly interface with existing building systems, while in parallel providing easy routine maintenance and ensuring simple retrofitting without disrupting solar PV operation.

Addressing the challenge

Thermocable’s ProReact temperature sensing LHD systems are engineered to address the unique fire detection challenges of solar panel installations. Designed for reliability and precision, they provide comprehensive protection across the entire PV array (including associated cabling, inverters and battery storage systems).

ProReact’s performance has been independently validated in the aforementioned real-world study, confirming its effectiveness in detecting early signs of overheating and potential fire risks in solar PV environments.

*Link to Independent Report

In a series of tests accounting for variations in roof slope, ignition type and location, PV module layout and detector placement, these LHD systems consistently detected fires in less than one minute. The fastest response occurred in just 11 seconds, underscoring LHD’s rapid detection capability.

These findings affirm the reliability of LHD for monitoring beneath and around solar panels, with the globally recognised fire safety research institution concluding: “LHD systems can support early warning detection of a PV-related fire” [ZAG Department for Fire-Safe Sustainable Built Environment, Section for Fire Research and Innovation, About Using Linear Heat Detection Systems in PV-Related Fires, Report No 366/25-560-1-EN, July 2025]

Installation guidance

For PV installations, we recommend positioning the LHD cable along the longitudinal support bars of the metal framework used to mount and angle the solar panels. These structural elements, typically found beneath the panels, provide ideal locations for securing the detection cable, while ensuring optimal fire detection coverage.

When installing a single run, the cable should be routed along the highest longitudinal support bars. This placement takes advantage of the natural chimney effect, where heat rises and accumulates beneath the pitched panels. By situating the cable above the likely ignition point, it will detect abnormal heat or fire events early and accurately.

For enhanced protection, or added redundancy, a double run is recommended. This involves installing one cable along the highest support bars and a second along the lowest support bars. The dual-level approach offers comprehensive vertical coverage and can increase speed and reliability of fire detection across the PV installation area.

In order to secure the cable, we recommend using P-Clips or J-Clips, which are designed to mount directly on to the support bars, spaced at regular intervals of 0.5 to 1.0 metre to ensure the cable remains firmly in place and maintains consistent proximity to potential heat sources.

It’s also important not to over-tension the cable during installation. The cable should have a slight amount of ‘give’ to accommodate thermal movement caused by temperature fluctuations, which helps to preserve long-term performance. By following these guidelines, system installers can ensure that the LHD system is positioned for maximum effectiveness in detecting thermal events within PV systems, in turn providing early warning and helping to mitigate potential fire risks.

Compliance and recommendations

Insurance providers, including FM Global, advocate for line-type heat detection in solar PV installations as part of a fire safety strategy. FM Global’s Property Loss Prevention Data Sheet DS 1-15 Roof-Mounted Solar Photovoltaic Panels recommends installing FM Approved linear heat detection on the roof cover and below the PV modules for early heat anomaly detection.

Similarly, Zurich’s Photovoltaic (PV) Systems on Buildings document recommends LHD as a preferred fire detection option for rooftop PV systems.

Implementing Thermocable’s ProReact LHD is a key measure for improving fire safety in solar PV installations. By understanding the unique risks inherent in solar PV systems and integrating this solution, the likelihood of fire incidents is significantly reduced.  

Thermocable ProReact LHD provides reliable, robust and proactive early fire detection, enhancing the overall protection of solar PV assets. This technology enables rapid early detection of potential hazards and aligns with industry Best Practice (and increasingly stringent insurance-driven project specifications).

Installing Thermocable ProReact LHD enhances the long-term safety, reliability and efficiency of solar energy systems.

*Further information is available online at www.thermocable.com