Wild solar panel record puts fire risk in the spotlight

Photo: Thomas Rasmussen

On 21 April, more than half of Danes’ electricity came from solar panels. But the more solar panels we install, the more fires we will see, says DBI’s expert in solar panel fires, Jens Steemann Kristensen.

Friday 21 April 2023 wasn’t just a sunny day that brought Danes out onto their terraces and balconies. In the hour between 13:00 and 14:00, Danish solar panels broke a record, producing a total of 2,222 MWh, which covered 54% of Denmark’s electricity consumption. Seen over the whole day, 21 April also broke a record with 21% of the power in the grid coming from solar panels.

The record is not only related to the fact that the weather was at its very best but it also stems from the fact that Denmark has significantly expanded its solar capacity in recent years. Denmark installed 720 MW of solar panels in 2021, thus increasing the total capacity by 44% and reaching a total of 2,344 MW.

‘But the more solar power that goes into our sockets, the more fires we will see in solar panels,’ says DBI’s Jens Steeman Kristensen, who has written a PhD about fires related to solar panels.

Larger spread of fire with solar panels

Most recently, in May, a fire broke out in a solar panel-covered roof at a Danish school. Fire technicians have not yet concluded whether the fire originated in the solar panels, but it is certain that the solar panels contributed to the spread of the fire.

Together with his foreign research colleagues, Jens Steemann Kristensen has calculated that 29 fires will occur globally every year for every gigawatt of solar panels installed. Data from Holland, however, indicates a slightly lower risk, as the ratio here is calculated at between 4.3 and 6.6 annual fires per installed gigawatt. This corresponds to the fact that statistically speaking, we will see 10–15 solar panel fires per year in Denmark with the current level of expansion.

Fires can occur due to faults in the solar panels’ electrical systems, among other causes. And once a fire has started, it will spread into the space between the roof and the solar panels. The underside of the panels reflects the heat back down onto the roof, resulting in a greater spread of the flames, which ultimately means that the fire can spread over a large area.

‘This is a problem since solar panels are not part of the building and are therefore not regulated in building codes. Normally, roofs are designed to prevent fire from spreading, but here we have a completely different situation,’ explains Jens Steemann Kristensen.

Better handling of solar roof fires

In addition to the situation being in a regulatory vacuum, there is also little knowledge about how best to deal with a solar roof fire. However, Jens Steemann Kristensen and a colleague have recently started preliminary work on a scientifically sound approach to determining the most appropriate strategies for dealing with this type of fire.

And this work is becoming ever more critical as Danish roofs are increasingly covered with the blue-black panels that generate our green energy.