A Danish-Norwegian research group has investigated how fire could propagate in building-integrated photovoltaic (BIPV) facades and has found that the gap distance between the panels and the wall, as well as the presence of combustible materials in the wall's cavity, are key factors.
The research group included academics from Norway's RISE Fire Research AS and Fire Research and Innovation Centre (FRIC), as well as the Danish Institute of Fire and Security Technology (DBI).
“PV modules contain polymers that can ignite,” RISE researcher Reidar Stølen said. “How fast this occurs, and how much of the combustible materials contributing to the fire depends on how big the ignition source is, the distance between the building and the module, and whether the module has glass on both sides, or only on the front.”
“Both facades with living plants and PV modules have many benefits for the environment and can look very nice,” research co-author Janne Siren Fjærestad added. “We believe and hope that many more such facades can be built in the coming years without compromising the fire safety of the buildings.”
In their report, the scientists sought to assess, in particular, which factors increase the ignition hazard, how vertical fire spreads along the facade, and if heat exposure to the building and neighboring buildings contributes to ignition. To answer these questions, the scientists contacted suppliers of both photovoltaic modules and systems for green facades, as well as building owners and researchers working with such systems.
They then conducted 35 experiments, of which 25 included photovoltaic modules and 10 green plant systems.
Their analysis showed that three main factors contribute to propagating fires in PV facades: the distance between the wall and the photovoltaic modules; the presence of PV panels built 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. “With increasing distance, the modules tolerated more heat from the initial fire and released less heat when they ignited. The same effect was found when switching from modules with monofacial glass to modules with bifacial glass. It was found that increasing the cavity distance by 4-5 cm has the same effect as switching from monofacial glass modules to bifacial glass modules.”
The researchers also stressed that it is currently difficult to run tests for classification according to the EN 13501-1 standard, which defines a standardized procedure for the classification of reaction to fire for all construction products. “Photovoltaic modules can also be challenging to test in a good way to provide a relevant classification since the test methods are not adapted to the unique properties of a photovoltaic installation,” they noted.
RISE recently conducted a series of experiments indicating that the distance between solar modules and rooftop surfaces could be a crucial factor in PV system fires. It also investigated how fire could propagate in PV systems deployed on flat roofs.
