Introduction

The environmental goal of decarbonisation reduction has driven Members to look to utilise more renewable forms of energy. There has been an overall increase in the utilisation of photovoltaic (PV) panels which can either be roof or ground based. Although the movement toward developing renewable forms of energy is to be commended, there are several associated risks which need to be understood and carefully managed. UMAL has produced this risk alert which looks to raise awareness of some of the hazards associated with PV to both potential injury to people and damage physical assets.

Research in the UK showed that most fires were caused at DC isolators with a further significant causes being at the Inverter point and the DC connectors. There are a number of areas where fires have been recorded in photovoltaic systems such as cell damage, cabling defects, cell shading, electrical issues such as arc faults, bypass diode faults, earth faults, bridging, lightning strikes and fires spreading from inside the building to the involve the PV arrays.

Other research in the UK, Italy and Germany, for instance, shows that the number of fires related to PVs remains small – less than 1% – of all fire incidents, with the majority on sloping roofs rather than on flat roofs. A significant proportion are also described as “significant” with a number of injuries and trauma also recorded with buildings burned down or badly damaged.

Typical array systems can contain a large amount of combustible polymers in the equipment. Most systems on campus sites are not integrated into the roof, with them placed on top of the roof structure, so are not subject to fire test regimes that occur for roof construction. If selecting plastic support for the PV array the selection should consider the fire prorogation properties of the plastic.

In fire tests it has been shown that full fire propagation can occur within 4 minutes to 12 minutes, depending on the construction of the photovoltaic array.

There are large amounts of UK standards and approved specifications for these systems, which should always be followed, and for which UMAL can give advice.

General Fire and Safety Precautions

• It is important not to increase the fire spread potential of the roof so that if the PV panels are located on combustible roofs, they should be sited on incombustible material fire-resistant barriers to the roof material.
• As they are electrical installations, they would be subject to DSEAR risk assessments if they are sited near any flammable dusts, gases or liquids so they do not become an ignition source for the hazardous materials.
• There should be a Hot Work Permit if any hot works are conducted near the panels.
• Isolation switch locations should be known by the first responders to an incident. Not all systems are equipped with a DC isolator (also known as fire service switches), merely an inverter switch, the latter not turning off the PV arrays.
• Information on the location and system details should be available for Fire Fighters – signage to warn of PV presence on a roof is recommended. The use of lights during a fire can create DC current in the array at night time. Difficulties in firefighting can occur due to fire, water and electricity all being in the same place at the same time.
• The inverters, that create heat during normal use, should be clear of any combustible materials and be well ventilated. As the majority of fires appear to occur in the electrical control equipment areas, fire detection in these areas is essential.
• Sloping roofs can exacerbate the chimney effect under photovoltaic panels and thus have the potential to spread fires more than if the panels are on flat roofs.

• The additional weight of the PV panels should be considered, as this can promote earlier roof collapse during a fire. Structural surveys are recommended to ensure the roof can cope with the additional weight under all circumstances. Note that snow can be trapped under the panels and create additional weight.
• Dry waste and vegetation can become trapped under the photovoltaic panels creating a fuel source should there be a fire, so maintenance/cleaning of the array areas is strongly recommended.
• Ensure bird droppings are removed as soon as possible as these can cause some shading that can produce local hot spots and then fires. Any other materials above the arrays can also cause shading that can lead eventually to fires, even if the material is not in contact with the array. Regular cleaning of panels is thus essential. The major roof fire at the Bristol Museum building in 2022 was reported to have been caused by bird damage to the PV panels.

• Ground based panels can be subject to vandalism and theft – there is copper and aluminium present in the arrays. Suitable security should be arranged, this also to protect persons from being in contact with the live panels, particularly during daylight hours. Weld mesh perimeter fencing to height of 3 metres is recommended – the gates are recommended to be constructed to the same standard and by secured by welded-on high security locking bars and equivalent padlocks, such as to at least the Sold Secure Silver standard. If the PV area is significant additional protection against vehicle attacks should be considered. Monitored CCTV is strongly recommended, with cameras capable of viewing the area in times of darkness.
• The photovoltaic system can be classed as low or high voltage depending on the system, including the Inverter, so that appropriate electrical controls will apply for each system. There is an IET PV Code of Practice that would assist in risk managing this aspect and this Code also includes advice on lightning protection.
• It is recommended that there is a 2.5 metre gap between individual arrays and any fire barrier that goes to roof level, although this gap could be halved if the risk of fire spread across fire compartments is low.
• There are a range of installer qualifications that are recommended as a minimum when choosing an installation contractor. There are also many guidance documents and standards for inspection, testing, commissioning, and maintenance. UMAL can provide details on these.
• Photovoltaic panel installations are subject to the Construction (Design and Management) Regulations 2015, and the Member’s exiting compliance arrangements would apply, with PV construction safety maters included in the Safety Plan and File.
• Fire risk assessments must include their presence as they can contribute to life safety issues, particularly for fire-fighters.
• Safe systems of work should also be created for maintenance or other persons who access PV array areas as these are live electrical risks. The DC cables should be well protected to prevent firefighters or maintenance workers on roofs comping into contact with the live electrical cabling. Apart from fire and electrical risks it is known that surface temperatures of arrays can reach 80⁰C on sunny days.
• High winds can cause the panels to move and so damage the roof. Modern panels are typically designed to withstand winds of 54 m/s (120 mph), but checks should be made at the design stage that the panels will withstand typical winds at the location.

There are large amounts of UK standards and approved specifications for these systems, which should be followed, and for which the UMAL Risk Management team would be happy to assist with and provide guidance.