While there are no working models of WALiD’s rotor blades as of yet, Rapp says many manufacturers have expressed interest in their work. But manufacturing a complete thermoplastic blade will require a massive change in current production methods, which is especially hard to do when producing huge blades. Rapp believes that the technology WALiD developed might be used sooner for smaller blade production.
Meanwhile, researchers at IACMI-The Composites Institute’s National Renewable Energy Laboratory in Denver have manufactured an experimental thermoplastic blade just 9 meters long.
“We can’t go out and build a 70- or 80-meter blade every time we want to innovate with a new material or a new manufacturing process,” says Derek Berry, wind technology area director. Although the laboratory began its research with coupon-level testing, the 9-meter blade is an ideal size to prove that you can scale up to thicker, bigger and more complex parts without going to the large megawatt-size blades, says Berry. “You can get 80 to 90 percent of the way there in understanding how a material will function in the manufacturing process, what type of properties you can get and things like that … . It gives you a huge amount of information on whether you should move forward with that material and that manufacturing process.”
The most aggressive innovation in the experimental blade was the use of a thermoplastic resin system. “Once you form [a thermoset blade] there is no way of going back; it is a chemical process that is irreversible. At the end of that blade life, 20 to 30 years down the road, the only thing you can do with it is put it in a landfill or maybe chop it up and use it for low-grade application,” he explains.
Thermoplastic resin blades, on the other hand, could be recycled. It might even be possible to pull out the fibers and the resin system and reuse them to make new blades or other composite structures.
IACMI’s experimental 9-meter blade was made with Arkema’s Elium® resin system, which has an exotherm in the same range as thermosets. “It is a thermoplastic that works more like a thermoset when it comes to process,” says Berry. That’s significant because it would mean that blade manufacturers would not have to replace their tools and processing pumps.