Better Save than sorry: Why Sand and Dust testing matters!
The IEC 60068-2-68:1994: Environmental testing Part 2-68: Test L: Dust and sand Method Lc2 Free blowing dust is a kind of extreme body scrub treatment conducted on photovoltaic modules.
We took our panels to a renowned institute, where they spent four hours (2hours per side) being blown by a mix of dust and sand particles with a diameter of 380µm, at a speed of 18m/s, over a delimited area of the front and back side.
All that in a sauna at 63°C (145,4°F), positioned orthogonally to the sand beam.
Relaxing, isn’t it?
Relaxing, isn’t it?
Not really. Passing this test has its relevance, although it usually goes quite unnoticed, confused among others considered more important. Let’s see why.
- Dust and sand particles of 380µm are classified as medium sand (ISO 14688-1:2017), 95% made of silicon.
- 18m/s corresponds to approx. 65km/h. Just to give you an idea, a haboob (very intense wind carrying mass of dust and sand, typical of desert areas) blows at speeds between 35-100km/h.
In real-life operating conditions, panels are not frequently subjected to this type of stress, so extreme and happening at the same time. However, a product passing such a test is likely to withstand full operation for a long time. First of all, sand and dust are in the air or wind and strike uniformly the entire surface of the panel, both the front than the rear side. Secondly, there may be significant variations in operating conditions depending on the climatic area or type of installation.
This test is performed to evaluate the ability of materials to operate in blowing sand conditions without degrading their performance, effectiveness, and reliability due to abrasion. In this very case backsheet and glass are under special surveillance: the sand that is blown on the module behaves like sandpaper scraping the surface of the front glass and the film on the rear side .
aleo passed this test because, besides other criteria, glass and backsheet showed no evidence of major visual defects, as shown in the pictures below and because the electrical safety of the panel was not compromised.
In May this year, in a Dupont™ study conducted on 3GW power, 9 million panels and 551 installations in North America, Europe, Asia and the Middle East, it was found that 16% of the panels (1,440,000 pieces) had defects due to backsheet aging / wear / abrasion. There was even an increase from 5 to 23% between the fourth and ninth year after installation (www.photovoltaics.dupont.com). The causes would be attributable to the need for manufacturers to lower production costs in order to be more competitive and the consequent use of thinner and thinner layers of polymer film.
But passing this test alone doesn’t mean plants will assure high yields in the long run, if not properly maintained. Indeed, sand and dust sediments, in addition to being potentially hazardous in terms of safety (in extreme cases they can lead to fire if the junction box is not properly sealed), also affect the performance of the panel. Between 2014 and 2015, TÜV Rheinland has calculated losses of up to 3.7% in the case of unmaintained installations (i.e. not regularly cleaned).
What we at aleo will never stop emphasizing is that, here too, the bill of materials plays a key role together with proper maintenance. Since abrasion from dust and sand will never involve only a specific part of the glass or back film, it will be anyway essential to have quality components that can withstand together for a period of more than 25 years.