The idea sounds great: solar cells on the tarpaulin of a truck producing the power for the electric drive of the vehicle. A perpetuum mobile for road use, without CO2 emissions and without increasing the price at the pump. – It would be nice.
Solar cells on truck tarpaulins
It is now certain: Solar cells on truck tarpaulins really work. “The electrical energy generated will be insufficient for the drive,” says Dr. Jonas Sundqvist to dampen euphoria, “but the rolling solar park can certainly make a contribution to the supply for cooling or heating units.”
Dr. Jonas Sundqvist, Group Leader for Thin-Film Technologies at Fraunhofer IKTS
“The rolling solar park can make a contribution to the supply for cooling or heating units.”
The group leader for thin-film technologies at the Fraunhofer Institute for Ceramic Technologies and Systems IKTS has discovered truck tarpaulins as carriers of power generators. It’s obvious: They are out all day and get lots of sun. The research project involves the Fraunhofer Institute for Electronic Nano Systems ENAS, the Saxon Textile Research Institute and a number of companies specializing in textiles. Their common goal: To promote the idea of a solar power plant on two or more axes.
This is made possible by textile, flexible solar cells. “We can produce solar cells on technical textiles by means of various coating processes,” explains Dr. med. Lars Rebenklau from Fraunhofer IKTS. Normally, the wafer-thin layers of a solar cell – including ground electrode, photovoltaic active layer and cover electrode – are applied to glass or silicon. For truck tarpaulins, it is a textile material, more specifically a fiberglass fabric. This has the advantage that it can withstand the 200 degrees Celsius required for coating without any damage.
Attaching a very thin layer to a grater
The processing temperature is just one of many technical challenges. The individual layers of the solar cell are 1 to 10 microns thin, while the robust tarpaulins are extremely rough. But how should you attach an extremely fine and sensitive layer to such a surface? The researchers resort to a trick: they apply a leveling layer of silicone to the textile thus compensating for ups and downs. On the planed surface of the glass fiber fabric, the power-generating layer finds its hold. “Despite its additional function as a small solar power plant, the tarpaulin is hardly heavier,” says Sundqvist. “A 10 percent increase in weight is to be expected.” – That’s about 75 grams per square meter or – depending on the vehicle – not much more than 6 kilograms.
Marketable solar textiles in about 5 years
The Fraunhofer research team has already produced a prototype – of the tarpaulin, not of the truck equipped with it. “We were able to show that our textile solar cell actually works,” says Rebenklau. “Its efficiency is currently 0.1 to 0.3 percent.” The efficiency or effectiveness indicates how much of the captured sunlight the cell can convert into electrical energy. That’s around 20 percent for photovoltaic systems on houses. So there is still room in case of the tarpaulins. At the moment, Fraunhofer IKTS is working on increasing the efficiency to more than 5 percent – at this value the textile solar cell should pay off. If everything works as hoped, it could be launched in about 5 years.
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Solar cells for fixed bodies?
But will the tarpaulins withstand the rough life of a truck? Erik Wirsing, VP Global Innovations at the logistics specialist DB Schenker, is always open for technical innovations. He is also interested in the Fraunhofer project, but is also skeptical: “Tarpaulins are always used where semi-trailers are loaded from the side or from above. You have to open them like a curtain. This means that the solar cells have to be extremely flexible to withstand the constant folding. “However, Wirsing applies the idea of the power generator on wheels in another way:” I can well imagine solar cells for fixed bodies in the future. “