“The challenges in technology are really in the blades because they have to get bigger – much faster than cells or spinners do – and they have to get lighter and less costly. We are providing aerospace quality for a commodity price,” he says.
MFG’s customers design most of their blades with E-glass fiberglass, but some request S-glass if they require more stiffness or strength. Although some turbine blade designers are now incorporating carbon fiber into their blades to improve stiffness, using the material causes additional challenges. “It has a much narrower window for manufacture, and it doesn’t like bending at all,” LaFrance adds. Carbon fiber is also conductive, making it more susceptible to lightning strikes, which are the most common source of blade damage.
Developing Design Tools
GE’s Global Research Lab’s research with composite blades in the aviation industry has informed its work in wind turbines. “We have developed manufacturing processes – an understanding of materials and materials’ behavior and design tools,” says Shridhar Nath, technology leader, composites.
He notes that longer blades present logistical as well as materials challenges. As blade size increases, transportation costs become a larger factor. GE is investigating whether a two-piece blade would resolve some of those issues, but that would require blade manufacturers to find ways to join them in the field.
The manufacturing process for such blades would be slightly different. “For example, where do you break the blade up? It places more emphasis on the design aspect; we have to understand what are the loads, what is the wind regime, what are the mechanical issues or the structural issues that go into those?” says Nath. “Those are the challenges that we are addressing and that we are working toward resolving.”
GE is always looking at new glass fibers and resin systems that might reduce weight. “We have had a lot of experience with carbon with our aviation business, and carbon is one-third the density of glass, so certainly that becomes attractive. But it’s a lot more expensive,” he says. “So that’s the tradeoff. What is the investment, what is the value added, what are the tradeoffs between different material systems and design processes?” Another important consideration is the availability of a material, which means checking the supply chain to ensure that potential materials will be available in the quantities that GE requires.