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An international research team has analysed which factors contribute to fire accidents on photovoltaic façades and found that the distance between the wall and the photovoltaic modules plays a crucial role. The scientists also pointed out that project developers should carefully consider which combustible materials are embedded in the wall cavity.
A Danish-Norwegian research group has investigated how fire might spread in building-integrated photovoltaic (BIPV) façades and found that the separation distance between the panels and the wall, as well as the presence of combustible materials in the wall cavity, are key factors.
The research group consisted of academics from Norwegian companies RISE Fire Research AS and Fire Research and Innovation Centre (FRIC), as well as the Danish Fire and Safety Technology Institute (DBI).
“PV modules contain polymers that can ignite,” RISE researcher Reidar Stølen told pv magazine . “How quickly this happens and how much combustible materials contribute to the fire depends on how large the ignition source is, the distance between the building and the module, and whether the module has glass on both sides or just on the front.”
“Both façades with living plants and photovoltaic modules have many environmental benefits and can be very beautiful,” added Janne Siren Fjærestad, co-author of the research. “We believe and hope that many more such façades can be built in the coming years without compromising the fire safety of buildings.”
In their report , the scientists sought to assess, in particular, which factors increase the risk of ignition, how vertical fire spreads along the façade, and whether exposure to heat from the building and neighbouring buildings contributes to ignition. To answer these questions, the scientists contacted suppliers of both photovoltaic modules and green façade systems, as well as building owners and researchers working with such systems.
They then conducted 35 experiments, of which 25 involved photovoltaic modules and 10 green plant systems.
Their analysis showed that three main factors contribute to the spread of fires in photovoltaic facades: the distance between the wall and the photovoltaic modules; the presence of photovoltaic panels constructed with glass on one or both sides; and the presence of other combustible materials in the wall cavity.
“Experiments with modules with monofacial glass and the smallest cavity (6 cm) produced the most intense fires,” the group explained. “By increasing the distance, the modules tolerated more heat from the initial fire and released less heat upon ignition. The same effect was observed when switching from modules with monofacial glass to modules with bifacial glass. Increasing the distance between cavities by 4-5 cm was found to have the same effect as switching from modules with monofacial glass to modules with bifacial glass.”
The researchers also stressed that it is currently difficult to perform tests for classification according to EN 13501-1, which defines a standardised procedure for classifying the reaction to fire of all construction products. “Photovoltaic modules can also present a challenge when testing to provide a relevant classification, as the test methods are not adapted to the unique properties of a photovoltaic installation,” they noted.
RISE has recently conducted a series of experiments indicating that the distance between solar modules and roof surfaces could be a crucial factor in PV system fires. It also investigated how fire might spread in PV systems deployed on flat roofs. |
