GE researchers have leveraged the tools they developed for aviation blades to improve the infusion process for wind turbine blades. “It sounds simplistic, but it’s quite complex because you are trying to model 40- or 50-meter long blades. You are looking at every material aspect, you are tracking the flow of resins, you are trying to optimize it so that you minimize any defects,” Nath adds.
While GE has experience in automated fiber placement and automated tape layup in the aircraft industry, Nath says it is not yet cost effective for wind because it won’t work in the volumes that the industry requires. But additive manufacturing offers possibilities, especially in tooling. The production of a blade tool can take 10 to 12 weeks, but with additive manufacturing that time could be reduced to a week.
Nath believes, however, that better design tools may play the biggest role in turbine blade improvements. “A wind blade is a combination of the aero structure, the actual structural analysis (the mechanical design) and the performance, because the customer at the end of the day is only interested in the annual energy production,” he says. “These are all conflicting. The aero guy develops a shape, but the manufacturing guys say that’s too expensive. So I think design tools that help us optimize all that are going to be another big innovation.”
Exploring New Materials
Almost all turbine wind blades today are made with thermoset resins, but that could soon change.
In 2013, a group of 11 European research and industry partners launched the WALiD project (Wind Blade Using Cost-Effective Advanced Composite Lightweight Design) to investigate using thermoplastic materials in all the areas of a blade. “We developed new material concepts and processing technologies. At the same time, due to the new process technologies, we were able to modify the design of the blade according to the new material properties,” says Florian Rapp, head of team foam technologies for Fraunhofer Institute for Chemical Technology ICT, Polymer Engineering.
During the four-year project, which ended in January, the WALiD partners developed highly durable thermoplastic foams and composites, a thermoplastic coating with high erosion and UV resistance and an automated fiber placement process for lay-up of hybrid fiber tapes. This resulted in a lighter blade with an improved design and an increase in service life, according to the WALiD website.
The project focus was not on manufacturing a whole blade, but on material definition and process qualification. “We made a lot of characterization regarding mechanical performances on coupon and subcomponent levels,” says Rapp.