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Addressing the risk of solar panel fires

04 March 2024

As solar panel adoption increases, it is important to take steps to mitigate the risk of fires. These include using reputable and registered PV installers, keeping up-to-date of safety regulations, explained Richard Williams

THERE HAS been an increasing number of fire incidents relating to solar panel systems reported worldwide. Between 2020 and 2021 the UK fire service saw a 12% increase, with a further rise in 2022.  

In the US, a series of fires at Amazon destroyed hundreds of solar panels at its Fresno warehouse in California in 2020. The company went on to experience five more similar events over the following 14 months. Walmart too saw seven fires, with one fire in its Indio store resulting in damage estimated at $1m.

In the UK in April 2022, Bristol’s science centre attraction ‘We the Curious’, was damaged by fire reported to have started with rooftop solar panels. The city’s largest PV installation, some 60 panels out of 200 were damaged and the attraction closed, not reopening until 2024. It is reported a flock of birds damaged a panel and triggered a fault in the electrical system, a 0.01% chance of happening according to Building Research Establishment (BRE) report.

The fire safety challenge posed by PV panels

Fighting a PV blaze presents specific challenges. With one of the first tasks to disconnect the building utilities, however, PV panels are unique in that it’s not possible to shut them off like a switch, it takes time for them to de-energise. The inverter can hold a charge and pass electricity back to the PV panels. The conduit leading from the PV panels to an inverter remains live with direct current even after the main service panel has been shut off. During a fire this can have a huge impact when every second counts. So, are such reports impacting confidence and the growth of solar photovoltaic panels?

Last year, primarily due to the energy price crisis and a sustainability drive, the solar power industry saw a significant jump in solar PV installations. According to data from the Microgeneration Certification Scheme (MCS) - the standards organisation for solar energy and heating - 130,596 solar panels were mounted on UK roof tops in 2022. Representing growth in one year previously only experienced in the three years between 2019 to 2021 combined, apart from those years following subsidy changes. These figures include all solar PV systems with a generating capacity of up to 50 kilowatts and registered with the MCS, notably therefore the figure is likely to be even higher, with an increasing number of installations in the UK not registered at all.

It does mean there are over 1.3 million registered solar power installations across the country, two thirds on the ground and the remainder on residential and commercial roofs, generating at least 15GW of solar power in the UK.

PV solar panels promise cost savings in terms of energy bills and are described as the clean and green electric energy. Seen in many a field and roof top, the growth has been most significant in the domestic market, but the energy landscape is changing fast within commercial and industrial now battery energy storage is becoming more cost effective.

A PV system in an industrial context

In essence a PV system on industrial and commercial buildings is essentially the same as a domestic installation, except in size and that most are tied into the utility grid. The PV modules are built from cells and then arranged in strings and arrays, wired together in a series to increase voltage. In a PV array two or more strings are connected in parallel to increase amperage. PV cells produce direct current (DC) power, which needs to be converted into alternating current (AC) power in the inverter. 

With this rise in demand some may be shocked that PV installers are not legally bound to follow the guidelines or obtain accreditations from certifying organisations such as the MCS.

Who is monitoring solar panel safety?

So what controls are in place and who is monitoring safety? The big issue is that anyone can install a solar panel in the UK. Yes, work must be cleared by the local council and the government ‘recommends’ use of a registered electrician, but it’s not a necessity by law. 

As with all electrical installations, electrical incidents may happen, which is why all electricians are qualified and must undertake regular competency and on-going refresher training. The risk of a solar panel catching fire is still very low, but it’s not zero. 

Solar panel fires can be caused by improper installation or maintenance, arc faults and faulty wiring or from extreme weather events, such as hail or lightning, or as suspected in the case in Bristol – birds. 

In the US, one of the biggest issues, has been arc faults. Higher voltages can be prone to arcing.  It arises as you have DC power on the roof which if there is leakage on a cable or connector it faults to earth as it’s a constant current. However, improvements in the latest technology manufactured into the newest panels and micro inverters being produced detect the heat output prior to attaining an arc, the current output is converted to a safer level that considerably reduces these risks. 

Keeping abreast of safety recommendations

It's important to be up to date with these latest improvements in technologies as well as recent safety recommendations and regulations. New solar panels are also more resilient offering an even greater reduction in fire risks. Understanding these products and their installation comes from experience of working in an evolving sector and with experts who can recommend the most appropriate panels and systems for installation. 

It's vital to use reputable and registered PV installers and, like maintaining your car, checks need to be carried out regularly. The first step would simply be to ensure those installing your PV and/or battery storage systems are registered with the MCS, and installation conducted in accordance with IET guidance.  This will verify their competence and the installer is duty bound to use verified products, so ensuring safety and quality.

Following installation PV panels can so easily be neglected and left to deteriorate. With those systems come risks. We need to raise this issue among those who may have installed their systems some 10+ years ago now.  

What steps can you take?

Anyone concerned about their PV systems should seek further advice and consider retrofitting a micro inverter AC system or module level optimisation. Look at the maintenance programme and ensure the system has been checked through periodic testing and by a professional. All installations should address an ongoing operations and maintenance agreement to avoid costly faults. Above all if you suspect any signs of overheating, the first task is to isolate the supply, and call the installer. 

The industry is proactively working on solutions to prevent and mitigate fire hazards. As with all technologies that have been installed by qualified engineers and are maintained and managed, be assured solar PV panels will continue to deliver you clean, cost-effective power, safely.

Richard Williams is founder and MD of Aztec Solar Energy

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