The risk of hail damage to solar modules is greatest if they lay on a flat roof and are placed in a south to west direction. That is the view of researcher Hans de Moel of VU University Amsterdam.
De Moel conducted research with a large group of colleagues, the Royal Netherlands Meteorological Institute and Achmea to gain more insight into hail risks.
Easy to find out
The study investigated several factors: the angle of the solar module, the direction and the size of the hailstones. De Moel presented his research at an online meeting of the Dutch Association of Insurers: “We conducted our research using literature, interviews, analyzes, aerial photographs and damage data, whereby those aerial photographs in particular were of great value. This made it easy for us to find out how many solar modules are mounted on a roof, in which direction and under which angle they are installed. We linked these various factors to the damage and in doing so we were able to determine the vulnerability of solar modules to hailstones of a certain size.”
According to De Moel, damage to solar modules can be divided “very simply” into two types: visible and invisible damage. “With the first you see the impact of the hailstones, but with invisible damage it can take months before the damage is” visible “, for example because the yield of the modules has suddenly decreased, while the cause is not easy to determine.”
The investigation shows that the damage mainly depends on the hail size, the properties of the roof and the direction of the modules. De Moel: “In general, the damage increases as the hailstones are larger. The damage seems to start with stones of about 2 centimeters, including the invisible ones, while the bulk of hailstones above 4-5 centimeters consists of visible damage.”
Flat roof versus corner roof
Finally, De Moel has demonstrated that the properties on the roof influence the damage. “This has to do with the angle of the modules,” explains De Moel. “On a flat roof you have a relatively smaller angle, so the hailstones fall more or less straight on it. The comparison between flat and roofs with an angle shows that that the average percentage of solar modules that broke down was more than 18 percent on flat roofs, compared to 12.6 percent on corner roofs. ”
He emphasizes that the angle of the solar module, however, has less influence on the damage than the direction. “If the solar modules are placed to the west, southwest or south, the chance of damage is almost twice as great as if they point to the southeast. In the first case, the chance is about 16 percent and in the second case,” only ” 8.4 percent. This seems to be mainly due to the predominant wind direction of hail storms (from the southwest). ”
Source: Solar Magazine, 13 july 2020