Data centre solar panel flat roofs – What are the related fire risks and how can you reduce this risk?

According to the IEA¹, data centres consume between 0.9 and 1.3% of the world’s electricity demand, between 220 and 320 TWh. It is therefore not surprising that data centre solar panel (PV) flat roofs are becoming increasingly popular choice to help reduce energy costs and offset carbon dioxide (CO₂) emissions. As with the presence of any electrical plant installed on a datacentre flat roof, the inclusion of solar panels can increase the fire risk due to possible equipment malfunctions.

With regards to the level of risk posed, available international data, according to PV Magazine², suggests that fires caused by rooftop solar power systems are rare. It points to data from Germany that shows that in the 1.4 million solar power installations, only 350 have caught fire. In Japan, just 127 rooftop solar problems that included fire out of 2.4 million installations on domestic properties were reported. A study by the Journal of Building Engineering³ puts the annual fire rate for solar panel roof fires at just under 29 fires per GW.

However, as the number of data centre solar panel (PV) roofs increases, the probability that more may be affected by fire also goes up. This is a fact that has not escaped building insurance providers or the providers and operators of the data centres. Both parties understand that an outbreak of fire on the roof can have hugely disruptive and costly consequences for a data centre, where protecting the building and its contents, and keeping costly downtime (estimated to be £247,000 per hour⁷) to a minimum, is critical to the smooth operation of a 24/7 business model.

In this blog we will look at how the electrical failure of the solar panel flat roof components can result in electrical arcing, creating an area of very high temperature with the potential to act as a source of ignition for surrounding materials on the flat roof.

We will explore what steps can be taken to reduce the risk of fire breaking out and, as risks can never be eliminated completely, we will also look at ways to enhance the specification of the roof build-up to potentially mitigate the damage caused should a fire occur.

What is the main cause of fires on data centre solar PV flat roofs?

Electrical arcing⁴ between conducting parts of the PV system that have become separated, or not correctly connected in the first place, is the main cause of fires on data centre solar roofs. An electric current flows across the gap between the components by ionising the air and the electrical arc created is extremely hot, with a temperature in excess of 6,000 °C. As the current in a PV system is direct (DC) and not alternating (AC), the arc can be sustained and may cause combustion of nearby materials including the waterproof membrane or the PV panels themselves.

There are a number of components within solar panel systems where arcing can occur. A study⁵ of PV related fires carried out for the UK government by Building Research Establishment found that the greatest fire risk, running at about 30% of incidents recorded, was caused by DC isolators. The next biggest risk was attributed to DC connectors, followed by inverters and finally the PV modules themselves. The issues with these components were attributed to poor installation practices in 36% of the PV fires, with system design errors accounting for 10% and 5% because of faulty products.

How can the risks of fire to a data centre solar roof be mitigated?

The best way to address the issues with component failures is to focus on sourcing solar panel systems with proven performance and ensure that they are correctly fitted by experienced installers in line with the manufacturer’s instructions. There are also some specialist products that can add extra protection against arcing by enclosing equipment to shield the rest of the system should a fault develop.

After installation of the solar panels, regular maintenance is needed to check that all components are functioning correctly. If, for example, any damage or wear and tear to the casings protecting connectors is not noticed, it can allow the ingress of moisture leading to electrical faults. Equally, cleaning of electrical connections is important, as any build-up of oxides can increase the temperature of electrical connectors and eventually lead to arcing.

All these steps will significantly reduce the chances of a fire breaking out; however, the risk can never be eliminated entirely.

Why are fire resistant roof boards frequently specified to mitigate the fire risks on data centre solar roofs?

As the probability of the fire risk on a data centre solar is low but never at the desired zero, the critical importance placed on keeping the business free from downtime means that data centres are choosing to specify fire resistant roof boards as part of the roof build-up.

The fire resistant roof boards sit underneath the waterproof layer and above the insulation slowing down any fire spread across the roof surface. They add an extra layer of fire resistance that can help mitigate the effects of the fire and limit damage to the insulation and roof deck below, thereby keeping any impact of the fire on the data centre below to a minimum.

Due to their rigid nature and high compressive strength, specifying fire resistant boards brings with it a bonus, as they can help to mitigate the damaging effects of the foot traffic associated with regular maintenance visits to solar panel flat roofs.

Georgia-Pacific manufactures a range of DensDeck® fire-resistant boards embedded with non-combustible fibreglass mat facers and a gypsum core containing crystalised water incorporated into its structure. DensDeck® Roof Boards are used as part of over 368,000⁶ flat roof assemblies that achieve a Factory Mutual (FM) Class A. The FM fire performance requirements are typically assessed to higher standards than local building regulations and the specification of FM Approved products and systems is often a requirement before building insurance providers will provide insurance cover for data centre solar roofs.

If you would like to find out how specifying DensDeck® Roof Boards as part of data centre solar roofs can help mitigate the risk of a solar panel roof fires and increase the longevity of the roof, please contact us today for advice and support.

¹ Data Centres and Data Transmission Networks – IEA September 2022

² There are – data missing – solar power fires a year – pv magazine August 2019

³ Experimental Study of the Fire Dynamics in a Semi-enclosure Formed by Photovoltaic (PV) Installations on Flat Roof Constructions – Journal of Building Engineering 28 March 2022

⁴ Fault tree analysis of fires on rooftops with photovoltaic systems – Journal of Building Engineering 29 Nov 2021

⁵ Fire and Solar PV Systems – Investigations and Evidence – BRE May 2018

⁶ Audit carried out on 16^th August 2023

⁷ Emerson Network Power (2010) in the US included data from 41 independent, average sized facilities. The study found an average financial loss of $5,600/min and $336,000/hour.