May 2017, a massive hailstorm sweeps through the town of Lakewood, Colorado. Hail up to seven centimeters in size damages cars, smashes windows and causes numerous injuries to people and animals. The Colorado Mills Mall had to be closed for a whole year due to the extensive damage.
A few kilometers away from the disaster building, a photovoltaic farm of the National Renewable Energy Lab (NREL) undergoes a test in which it is hit by hailstones of a similar size. Of the 3168 photovoltaic panels, only one was damaged. After the storm had passed, operations continued unhindered.
High-quality photovoltaic modules provide power for years and can withstand high temperatures in summer, freezing temperatures in winter, strong winds and - as you can see - heavy hail.
But what about here? Is hail a real danger? What damage can it cause and how can you prepare for it? How can you recognize hail-proof solar modules?
Solar system - is hail a risk?
The frequency of hail varies from place to place. In some places it occurs quite frequently, while in others, sometimes even nearby, it is rare. The degree of hail risk can be estimated using the map below.
So if your house is in the yellow, orange or red zones, you should probably invest in photovoltaic modules with higher mechanical strength. On the other hand, if you live in the blue zone, you have little to worry about. While you can always be unlucky, the likelihood of damaging hailstorms is very low.
Secondly, hailstones vary in size and hailstorms vary in intensity. And although absolutely no PV panel in the world survives a truly record-breaking hailstorm (a 15 cm diameter hailstone was found in 1970), most hailstorms do not pose a serious threat.
Case studies of photovoltaic farms by TÜV Rheinland
The report "Assessment of PV Module Failures in the Field" - prepared by TÜV Rheinland - states, based on data collected from ground-mounted PV installations: "Lightning, thunderstorms and hailstorms cause a drop in performance in only 10% and appear to reduce the overall performance of the installation by less than 1%."
It is interesting to note, however, that even if the glass remains intact, microcracks can occur in the solar cells during impacts, which in turn can lead to slug marks. However, their occurrence depends on several other factors, including the quality of the EVA film.
Hail resistance of photovoltaic modules
It is important that you as a customer know which panels are hail-resistant. In addition, the manufacturer's statements should be confirmed by external companies. For this purpose, a number of certificates have been developed to determine the minimum hail resistance.
The most important certificate is the international IEC 61215. Panels with this certificate can withstand 25 mm hail falling at a speed of 23 m/s, which corresponds to hail resistance class 2 (a 5-point scale mainly used in Western countries).
All solar modules sold in Germany and the European Union must have this certificate, which means that all solar modules are resistant to hail - at least to a certain degree.
Some manufacturers claim a higher resistance to hail. For example, Selfa claims in the data sheet of its panels to be able to withstand a hail ball of 55mm diameter at a speed of 33.9m/s. Tesla photovoltaic roof tiles, on the other hand, are said to be characterized by class 4 hail resistance.
Hail resistance also correlates with snow load capacity or mechanical resistance to frontal pressure. Outstanding photovoltaic modules in this respect are manufactured by LG, Panasonic, SunPower, REC, Selfa and Solarwatt.
Obviously, hail that is larger than assumed by the certification can cause damage.
So how can you protect yourself against it?
Insurance against hail
The best financial protection for solar system owners is PV system insurance, which covers the cost of repairing damaged modules. It is important to read the insurance conditions, as not all insurance policies protect against hail.
Homeowners with an installation on the roof can easily include the installation in the insurance of the entire building. This is the most cost-effective solution.
Although photovoltaic modules should work for many years without any problems, why not protect yourself completely? Insurance should not be expensive, especially if you have purchased high quality panels.
Does the manufacturer's warranty protect against the effects of hail?
Generally no. The manufacturer's warranty does not cover damage caused by force majeure. Here is an example of a clause from the warranties:
[Damage caused by] acts of nature or acts of God, including, but not limited to, lightning, hail, frost, snow, storms, waves, floods, extremely high temperatures, earthquakes, typhoons, tornadoes, volcanic eruptions, meteorite impacts, earth cracks or landslides [are not covered] - Q Cells warranty terms.