| Work Detail |
Norwegian scientists have evaluated how BIPV facades can react to a fire after a typical fire test for building facades. They found that flame spread in the wall cavity is possible, despite very limited amounts of combustible material, and that flames can spread throughout the façade very quickly.
Fire safety standards in buildings pose a significant challenge and have acted as a barrier to the development of the building integrated photovoltaic (BIPV) market. This creates a complex landscape in which it becomes vital for manufacturers and suppliers of BIPV products to understand and adhere to a multitude of standards in different markets, and recognize that fire safety testing of conventional PV products is already poor.
With this in mind, a group of scientists from the Norwegian institute Rise Fire Research has developed a fire test for small and large scale BIPV facades. “Testing of large-scale BIPV systems is lacking and this should be requested from more BIPV projects,” Rise researcher Reidar Stølen told pv magazine. “It would be very interesting to see more experiments on realistic scales. So if anyone can share information from other tests of complete systems, this may be a way forward to see what parameters are crucial to designing truly fire-safe BIPV façades.”
In the study “ Large- and small-scale fire test of a building integrated photovoltaic (BIPV) façade system,” published in the magazine Fire Safety Journal , Stølen and his colleagues performed the so-called SP FIRE 105 fire test, which is a large-scale façade testing method referred to in the building regulations of Sweden, Norway and Denmark, on BIPV façades. This test evaluates the fire-retardant properties of a façade system with respect to flame spread, falling parts, temperature at the eaves, and radiation to the floor above the burned home.
The test was performed on a 4 m × 6 mm photovoltaic façade based on aluminum mounting structures and frames. The scientists used custom-sized “common” BIPB modules with a glass front and a polymer backsheet. Each module was based on a 116 mm × 110 mm × 22 mm plastic junction box made of polyphenylene ether and polystyrene with connection cables and connectors. “The mass of the modules ranged from 14.1 kg to 5.6 kg, including the junction box and connecting cables,” the scientists explain. “Most of this mass was glass and aluminum, but approximately 12% was made of different plastic materials.”
The façade BIPV system was installed on a wood-framed wall with combustible wood fiber insulation covered in plasterboard. “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 system fire in three stages. First, they preheated the fire room and façade before flashing. They then exposed the bottom two rows of modules to large heptane flames and then the flames spread in the cavity from the third row to the top of the façade.
The experiment showed that the large heptane fire coming from the fire room located under the façade caused serious damage to the two lower rows of modules, causing them all to collapse in a short time. “The highest temperatures measured reached 850 ºC in the cavity during this stage,” the academics explained. “Once the heptane fire was extinguished, the fire was able to spread in a self-sustained manner beyond the cavity barrier and to the top of the façade, causing more modules to fall.”
The experiment also demonstrated that flame spread in the cavity is possible, despite the very limited quantities of combustible material, and that the fire was also able to considerably damage the glass, glue and aluminum of the construction. “Sealing the cavity with fire barriers can be difficult if the fire resistance of surrounding components is compromised,” the researchers noted.
The scientists concluded that the test results showed the importance of details in the assembly of BIPV façades and proper documentation of relevant fire tests of such systems. “Despite meeting IEC EN 61730 and EN 13501-1 standards, the entire façade system failed to prevent the modules from detaching from the façade and spreading the fire vertically in the cavity,” explained Stølen. “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 rate of heat release.”
In other recent work, RISE researchers conducted a series of experiments that indicated that the distance between solar modules and rooftop surfaces could be a crucial factor in photovoltaic system fires. A similar study, published by the University of Edinburgh and the Technical University of Denmark, showed similar results. The scientists analyzed the dynamics of the fire and the spread of flames in the substrate located under the panels. They concluded that the closer the distance between the panels and the roof, the greater the likelihood of larger, more destructive fires. |
