Wind turbines are considered "green technology," but the fiber-reinforced plastics they are made from are not so eco-friendly. New research shows steel blades are not only cheaper, but also exceed the plastic's recyclability by as much as 90 percent.
A team of researchers demonstrated the required aerodynamics and manufacturing process chains nessary for the creation of steel wind turbines, Fraunhofer Institute for Machine Tools and Forming Technology (IWU) reported. The researchers showed that even in large machines, light alloys could be used to keep the steel's weight down at functional levels. Using steel for the manufacture of clean energy turbines could come with significant benefits.
"First, it makes turbines significantly more ecological, since more than 90 percent of the steel can be recycled -- so using metal rotor blades makes wind power truly environmentally friendly," said Marco Pröhl, a researcher at the Indiana IWU. "What's more, compared to similar blades made of fiber-reinforced plastic, the cost of rotor blade mass production drops by as much as 90 percent -- and the blades can be manufactured more accurately."
Metal blades could also be manufactured more quickly more quickly than current technology. Through the right manufacturing process could create a new rotor blade every 30 seconds, as opposed to the hours it takes to complete a fiber-rich plastic rotor. To create these steel rotors, the researchers fold a flat sheet of metal using a bending dye to give it a typical blade shape. In the next step they use a laser to weld the edges and form a closed profile. The team then pumps a reusable water-oil mixture is pumped into the blade's interior and it is subjected to several thousand bars of pressure which "inflates" the blade and gives it its final form.
"The fact that we're shaping the blade from the inside out lets us compensate for any inaccuracies in previous steps," Pröhl said. "The geometry ends up perfect after the first production step, with the blades matching the flow profile milled into the tool to within 0.1 millimeters."
