Wind turbines bring to mind blue skies and a near limitless supply of clean energy. In many areas, wind farms dot the landscape on unused farmland or in desert areas. Not everything about wind power is completely environmentally friendly however, even if the power they provide is.
The large rotor blades that spin to create electricity are made of fiber reinforced plastic because it's light and keeping the weight of rotor blades down increases the turbine's efficiency. So what's the problem? The material in the blades is nearly impossible to reuse or recycle.
There is a solution however, at least at one research facility. In Germany, at the Fraunhofer Institute for Machine Tools and Forming Technology IWU in Chemnitz, researchers are considering metal as a material for rotor blades, specifically steel. Together with the Free University Brussels (VUB), the team is working on the HyBlade project, studying aerodynamics and possible manufacturing processes to see if steel blades could be a better option.
Marco Prohl, a researcher at Fraunhofer stated that steel blades could be superior to plastic fiber blades in many ways. "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. 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 can also be made faster if a production line can be developed to run continuously. A steel rotor blade can theoretically be created approximately every 30 seconds, compared to plastic blades that take hours to form.The differences in how each of the blades is produced are why steel blades come together so much faster. Rather than multiple steps of creating a mold, injecting resin and applying fiber mats and then waiting for it to harden in an oven, the steel blade process is much like that in the auto industry. A flat sheet of metal is folded, welded with a laser, shaped with a specially designed tool and pressure filled with oil and water.
Prohl explained, "The fact that we're shaping the blade from the inside out lets us compensate for any inaccuracies in previous steps. 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."
A single blade has already been produced and engineers are now working on an entire rotor assembly. Once created, it will be tested in a small wind farm on the coast of Belgium. If successful, one of the most efficient and clean forms of energy available could become even more streamlined and environmentally friendly.
Watch the video below for a basic understanding of how wind turbines generate electricity.
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