Pictures taken of the façade during the test
Image credit: Rise Fire Research, Fire Safety Journal, Creative Commons License CC BY 4.0
Fire safety building standards present a significant challenge and have acted as a barrier to the development of the building-integrated photovoltaic (BIPV) market.
This creates a complex landscape where it becomes vital for manufacturers and suppliers of BIPV products to understand and adhere to a multitude of standards in different markets, and to recognize that the fire safety testing of conventional PV products is already deficient.
With this in mind, a group of scientists at the Norwegian institute Rise Fire Research has developed a fire test for both small and large-scale BIPV facades. “Large-scale system tests of BIPV systems are lacking and this should be requested from more BIPV projects,” Rise researcher, ReidarStølen, told pv magazine. “More experiments in realistic scales would be very interesting to see. So if anyone can share information from other tests of complete systems, this can be a way forward to see which parameters are crucial to designing truly fire-safe BIPV facades.”
In the study “Large- and small-scale fire test of a building integrated photovoltaic (BIPV) facade system,” published in the Fire Safety Journal, Stølen and his colleagues conducted the so-called SP FIRE 105 fire test, which is a large-scale facade test method referenced in the building regulations in Sweden, Norway, and Denmark, on BIPV facade. This test evaluates the fire properties of a facade system regarding flame spread, falling parts, temperature at the eaves, and radiation toward the floor above the burning apartment.
The test was conducted on a photovoltaic facade measuring 4 m × 6 mm based on mounting structures and frames made of aluminum. The scientists used “common” custom-sized BIPB modules with a glass front and a polymer backsheet. Each module was based on a plastic junction box made from polyphenylene ether and polystyrene measuring 116 mm × 110 mm × 22 mm with connecting leads and connectors. “The mass of the modules ranged from 14.1 kg to 5.6 kg including junction box and connecting cables,” the scientists explained. “Most of this mass was glass and aluminum, but approximately 12 % was made from different plastic materials.”
The facade BIPV system was deployed on a timber frame wall with combustible wood fiber insulation covered with gypsum boards. “The distances between the modules were 20 mm horizontally and 40 mm vertically,” the academics specified. “The vertical gaps between the modules were sealed with an aluminum profile, and the horizontal gaps were open.”
The research group developed a fire on the system in three stages. First, they preheated the fire room and facade before the flash-over. They then exposed the two lower rows of modules to large heptane flames and then the flames were propagated in the cavity from the third row to the top of the facade.
The experiment showed that the large heptane fire from the fire room below the facade caused severe damage to the two lowest rows of modules causing all the modules to collapse in a short time. “The highest measured temperatures reached 850 C in the cavity during this stage,” the academics explained. “After the heptane fire had burnt out, the fire was able to propagate self-sustained past the cavity barrier and to the top of the facade causing additional modules to fall down.”
The experiment also demonstrated that flame propagation in the cavity is possible, despite the very limited amounts of combustible material, and that fire was also able to considerably damage glass, glue and aluminum construction. “Sealing the cavity with fire barriers can be challenging if the fire resistance of the surrounding components is compromised,” the researchers said.
The scientists concluded that the test results showed the importance of details in mounting BIPV facades and proper documentation from relevant fire tests of such systems. “Despite complying to IEC EN 61730 and EN 13501-1, the complete facade system failed to prevent modules from falling from the facade and vertically propagating fire in the cavity,” Stølen explained. “The cone calorimeter tests also show that the amount of combustible materials is limited in the modules, but that it ignites quite easily and burns with a high heat release rate.”
In another recent work, RISE researchers conducted a series of experiments indicating that the distance between solar modules and rooftop surfaces could be a crucial factor in PV system fires. A similar study, published by the University of Edinburgh and the Technical University of Denmark, showed similar results. The scientists analyzed fire dynamics and flame spread on the substrate beneath panels. They concluded that the shorter the distance between the panels and rooftop, the higher the probability of larger and more destructive fires.
Author: Emiliano Bellini
This article was originally published in pv magazine and is republished with permission.
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