2024-03-15 15:00:08
New tests carried out by the National Institute of Construction and Civil Engineering of Slovenia have shown that vertical photovoltaic installations offer greater fire safety than conventional diagonal or flat solar panels. The experiment demonstrated, in particular, how quickly a fire can spread under inclined panels.
March 15, 2024 Emiliano Bellini
Researchers from the National Institute of Construction and Civil Engineering of Slovenia (ZAG) have recently carried out a series of tests to evaluate the fire safety parameters of vertical rooftop photovoltaic systems and have found that these installations offer improved parameters compared to arrays. conventional on roof.
For the tests, the scientists used vertical solar modules supplied by the Norwegian specialist Over Easy and the Italian certification body Istituto Giordano. They also used a typical configuration of inclined photovoltaic panels as a reference. Two separate samples were placed at an angle next to the largest roof segment.
In one of them, the expanded polystyrene (EPS) insulation was directly covered by a two-layer bitumen membrane. I also included mineral wool under the EPS to protect the bottoms and have both samples at a similar height. In this case, mineral wool was not considered part of the cover.
In the second build-up, an additional mineral wool-based mitigation layer was placed between the insulation and the top cover. For this configuration, the same roof structure made of bitumen, mineral wool and EPS was used.
The panel used for the traditional setup was a pre-used panel with glass on top and a polymer backsheet mounted on an aluminum mounting system, with dimensions of approximately 1.6m x 1.0m. The vertical panels were also pre-used bifacial panels with glass on both sides and placed on an aluminum mounting system. The dimensions of these panels are 1.6 m x 0.25 m. They were installed at a distance of 0.4 m from each other.
“A wooden manger was used as an ignition source, as recommended by some standards and also because the heat transfer from a burning wooden manger goes in all directions, including all forms of heat transfer,” he explained to pv magazine ZAG fire safety expert Grunde Jomaas. “This creates a fire that is in direct contact with the cover membrane, all of which is considered more challenging than a gas burner or other potential ignition sources, while also being more realistic.”
Cradle locations were chosen to reflect the worst-case scenario for both paneled configurations. For the inclined configuration, the cradle was positioned near the bottom edge of the panel, where the height between the membrane and the back of the panel was 11 cm, to reflect recent discoveries regarding fire spread beneath photovoltaic panels. In the vertical configuration, the cradle was located next to the junction box. In the other configurations, the cradle was placed in the middle of the samples.
“Prior to ignition, the cradles were soaked with 5-6 ml of isopropyl alcohol to ensure rapid and uniform ignition of all parts of the cradles,” Jomaas explained. “After soaking the nativity scenes, the four were lit in less than 5 seconds with a lighter.”
The test showed that the fire in the unmitigated sample was extinguished regarding 12.5 m following ignition, due to deformation of the insulation and the entire EPS being prevented from burning. The fire under the photovoltaic panels was extinguished regarding 15 m following ignition, following the entire inclined panel was engulfed in flames.
“It should be noted that very limited damage was observed in the EPS, even in the case of a larger fire,” Joomas emphasizes. Therefore, the mineral wool provided a very good mitigation layer for this buildup, which might represent a typical buildup for an existing roof where the EPS would need a mitigation layer to prevent its complete involvement.”
According to Jomaas, the comparison of vertical and inclined photovoltaic panels “clearly” demonstrates that inclined panels create conditions that allow fire to spread rapidly through the roof membrane. “In other cases, the materials themselves do not allow the spread of flames,” she explained. “Second, not having a mitigation layer between the roof membrane and insulation prone to heat damage is highly inadvisable, regardless of the type and geometry of the PV panels installed on top.”
“With vertical solar panels, there are no cavities through which fire can spread,” he told pv magazine the CEO of Easy Solar, Trygve Mongstad. “We don’t want to create any panic, normal solar panels are also normally very safe, but it illustrates that there are more benefits to vertical solar panels on flat roofs, and for certain buildings where fire safety is an extra concern, we believe we can provide a good solution.”
The results of the experiment have not been confirmed so far by a third party.
In this link you can see a video of the experiment.
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