In May 2022, the President of the European Commission, Ursula von der Leyen, announced an ambitious plan to introduce a rooftop photovoltaic (PV) mandate for all public and commercial buildings and all new private buildings from 2027 and 2029 respectively.
This is highly laudable and by default becomes the world’s largest-ever such initiative. It also represents a rapid-fire, knee-jerk reaction from the politicians in Brussels designed to reduce Europe’s dependence on Russian gas. This also represents an effective ‘hedge’ strategy against future energy price volatility. As well, it will no doubt require a degree of additional fine-tuning.
In the event of fire, 27 European nations currently lack a regulatory framework designed to assure ‘rapid-shutdown’ at the level of individual solar panels. String or Central inverters will immediately turn themselves ‘OFF’ and turn alarms ‘ON’ in the presence of fire. However, individual solar panels can continue to produce potentially lethal amounts of DC electricity during the daytime.
This represents a major risk to the health and safety of firefighters, the structure concerned and its contents, including those dwelling therein. If one inadvertently adds water to the mix, the situation is further exacerbated. Current fire-prevention legislation is simply ‘Not fit for purpose’ – ask your local fire brigade. Their crews have become increasing familiar with this class of fire.
Several fires at floating PV installations have been reported around the world in recent years. The initial causes vary. However, firefighters note that such fires are particularly complicated because of the mix of fire, water and electricity, all present at the same time. These are the same issues that complicate the task of extinguishing PV rooftop fires. Water nearby a PV fire is undesirable.
PV solar systems can fail for many reasons ranging from physical damage and component failure to poor manufacture and bad workmanship. The cause of incendiaries can be linked to faults occurring at the level of connectors, junction boxes, DC isolators, heat accumulation commonly known as ‘hot spots’ (provoked by degradation of solar cells and caused by the infiltration of water and oxygen over time), soldering defects and a long list of other causes, cf. Technical note 1 | Lannesolaire.1 In turn, these faults give rise to reduced production of electricity, and instead, production of heat due to increased resistance. The latter is then the source of overheating, arc-faults and/or fire. Examples of such fires will be shown further below.
Thus, a critically important issue is the need for an appropriate legislative framework to accompany any pan-European rooftop mandate.
The group Generali has estimated as recently as 2020 that PV fire is costing the insurance industry in Europe in the vicinity of 100 million Euros per annum.
As in many parts of the world, much of the European continent is densely populated and thus land availability for on-ground solar installations is at a premium. Furthermore, and for good reason, the agricultural lobby is actively trying to minimise access to arable land for on-ground PV installations, none more so than the ‘SCOT’ (Schéma de Cohérence Territorial) at the level of local and regional government here in France.
Rooftop solar installations are expected to play an important role if Europe is to meet its obligations to reduce CO2 emissions in line with the Paris Agreement as adopted in 2015 by some 196 signatories. In Italy, for example, it has been estimated that in order to meet the country’s 2030 objectives of the European Green Deal (an earlier and less ambitious European objective to that cited in this article), the country would require to set aside ‘an area just above 1,000 km2 … to be covered with the PV modules currently on the market, that have a 22% efficiency’.2 Rooftop solar is often coupled with attractive feed-in tariffs and/or advantages for auto consumption. Consequently, rooftop solar has witnessed considerable economic activity in recent years.
However, scant regard is being paid by solar developers, their financiers, EPC sub-contractors, local authorities and/or solar installers concerning the associated PV fire risk, its potential for loss of life and/or material assets. Even in the absence of appropriate legislation, this behaviour is verging on irresponsible and negligent. This situation needs to be redressed.
Australia possesses similarly inadequate legislation to European nations as concerns rooftop solar. In Australia, one in four homes (2.68 million) now have solar modules on their roof. This has resulted in a five-fold increase in PV fires between 2016 and 2021. The Director of REA Global, Michael Mrowka, a large local installer of domestic solar systems has summarised the problem by likening it to a ‘ticking time-bomb’!
‘If we could change one thing to improve this situation, it would be to mandate rapid shutdown and panel-level monitoring and communication.’3
Since January 2019, the NEC 690.12(B)(2) has been further refined and now requires that ‘Controlled conductors located … on the surface of a building shall be limited to not more than 80 Volts within 30 seconds of rapid shutdown initiation. Voltage shall be measured between any two conductors and between any conductor and ground.’ Some rapid shutdown device manufacturers reduce this figure to 40 Volts. Lower operating voltage works to eliminate the risk of PV-fire and its propagation.
The above guideline is currently totally absent across Europe, and indeed most countries around the world outside the USA. Strings of solar panels continue to be commonplace in rooftop installations. These give rise to 400V to 1,000V and thus a risk of arc fault. Unless specific action is taken, the abovementioned EU initiative will therefore work to exacerbate the potential for rooftop and whole-structure fire in areas where people and their property are housed for extended periods or intermittently.
I would like to quote from an article by J. Foran in the journal International Fire Fighter, published in 2017. It dealt specifically with ‘how legislation, safety and fire training have failed to keep up with the rapid expansion of the (solar) alternative energy sector’:
‘To dispel the myth that voltage alone is not dangerous let’s use the example of a Taser. A Taser produces 50,000 volts, but only 0.0021 amps (105 Watts). Once contact with the body occurs the voltage drops, delivering an actual electrical charge to the body of between 7-26 watts. It will incapacitate an adult but causes no long-term physiological effects. In contrast, a typical domestic solar array will produce anywhere between 4kw (4000 watts) and 6kw (6000 watts) which is lethal…’ (and larger systems can produce still more lethal power).
As part of any solar sales process, US domestic consumers will routinely be made aware of the NEC 690.12 regulations and the need to eliminate the risk of rooftop PV-fire on their own homes.
Popular sentiment is currently supportive of increasing the number of solar projects to help meet more of the world’s future energy needs. These widely held sentiments are pushing numerous private and public sector organisations to undertake projects akin to that unveiled earlier this year in France by the national railway carrier, SNCF, namely, a total of 1.1 million m2 of solar rooftop PV on railway station buildings and nearby as solar-shaded carparking prior to 2030. The first of several public tenders for this programme made no mention of the need for obligatory fire-prevention measures! Elsewhere in France, solar-covered carports or ‘ombrières’ of gigantic proportions have already been installed to protect the vehicles of thousands of workers engaged by car manufacturers, such as, Renault and Peugeot. Ombrières are now a frequent feature at most of France’s larger supermarket chains. These are deployed to help meet rising electricity bills and promote a green, eco-friendly image for the commercial entity concerned. This trend is increasingly seen across all of Europe.
Public sentiment has also prompted some of Europe and the world’s larger energy (oil, gas and electricity) producers and distributers to enter the lucrative Commercial & Industrial (C&I) rooftop solar sector. By doing so, they help create a green, eco-friendly corporate image for themselves and their customers. This is good for business, including the innumerable EPC (Engineering Procurement & Construction) sub-contractors engaged to assist. Today, the C&I rooftop solar marketplace has become highly lucrative and is experiencing healthy growth. Yet, the potential fire hazards continue to be ignored for numerous large and small PV-rooftops.
Multi-Module Micro-Inverters (MMMI) provide a means to reliably avoid PV-fire at an affordable and justifiable cost. They also provide access to operational systems resilience (afforded by inverter redundancy) and high-granularity, real-time performance monitoring of individual solar panels. Not surprisingly, five different manufacturers have released new MMMI products onto the market in H1, 2022, each capable of servicing increasingly higher-powered solar panels. These include: Enphase, APsystems, Hoymiles, Yotta Energy and Generac Grid Services. ‘Rapid shut-down’ systems for individual solar panels can also be accessed via stand-alone devices or DC/DC optimisers. However, these latter solutions expose solar installations to ‘single point of failure’ (in the absence of inverter redundancy) and thus system vulnerability due to their continued dependence upon Central or String inverters.
To conclude, if the European Union and/or the United Kingdom were to introduce appropriate legislation in the realm of PV rooftop fire prevention, other countries around the world may take note and follow suit.
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