Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Generating eco-friendly power with metal rotor blades


Wind turbines deliver environmentally friendly electricity. Yet the fiber-reinforced plastics often used in very large rotor blades are almost impossible to recycle. Not so with steel blades: since these are composed of steel, their recyclability exceeds 90 percent. Plus they cost significantly less than comparable plastic blades.

Wind turbines feed eco-friendly power into the grid. To keep their weight down, the majority of larger rotor blades are made from fiber-reinforced plastics. These materials are rarely recycled at present, in part because it is very complicated to do so.

Technology demonstrator: formed from a 1.0 mm steel sheet and featuring integrated, folded reinforcement, the rotor blade was given its final shape with the help of an oil-water mixture.

© Fraunhofer IWU

Researchers at the Fraunhofer Institute for Machine Tools and Forming Technology IWU in Chemnitz are therefore focusing on metal, and especially steel, as a blade material. In smaller installations, the greater weight of the steel blades is inconsequential; as installations get larger, light alloys can be used to keep blade weight down.

Collaborating with colleagues from the Free University Brussels (VUB) in the HyBlade project, Fraunhofer IWU is developing the required aerodynamics as well as the necessary manufacturing process chains.

Manufacturing steel blades offers numerous advantages. “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,” explains Marco Pröhl, a researcher at the 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 can also be produced more quickly. Provided that processes are run in parallel – for instance, that a new metal sheet is fed into the production line as soon as the first blade has completed the first process step – then a completed rotor blade rolls off the conveyor belt roughly every 30 seconds. With fiber-reinforced plastics, the same process usually takes several hours.

Suitable for large-scale and automated manufacturing processes

The primary cause of these differences lies in the manufacturing process. Fiber-reinforced plastic blades often require significant manual processing: first, a suitable mold has to be made for the blades. Depending on the production variant, workers layer fiber mats in this mold, inject resin, and leave the component to harden for several hours in an oven.

This produces two half shells; once their edges have been trimmed, the halves can be glued together. These steps can be performed simultaneously, as in sheet metal blade manufacturing – but that doesn’t make them any quicker. It would take dozens of installations running in parallel to produce plastic blades at the same rate as metal ones.

In contrast, it is easy to automate the manufacturing metal rotors: the processes are similar to those in the auto industry, which means they are suitable for series production. The researchers start with a flat sheet of metal, which they fold using a bending die to give it a typical blade shape. Next, they laser weld the edges to form a closed profile.

After placing the preformed piece in a tool with the desired final shape, the researchers then pump a reusable water-oil mixture into the interior of the blade and put it under several thousand bars of pressure. This is equivalent to the pressure experienced underwater at a depth of many thousands of meters. This effectively inflates the blade, giving 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,” explains Pröhl. “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.”

The researchers have already produced a blade 15 centimeters wide and 30 centimeters long, using it to optimize the individual processing steps. Their next step will be to produce an entire rotor for a vertical axis turbine with 2.8-meter-long blades and a diameter of two meters. Once it is installed at a test site for small wind turbines on the Belgian coast, it will be put through its paces.

Hendrik Schneider | Fraunhofer Forschung Kompakt
Further information:

More articles from Machine Engineering:

nachricht Process-Integrated Inspection for Ultrasound-Supported Friction Stir Welding of Metal Hybrid-Joints
27.09.2016 | Fraunhofer-Institut für Zerstörungsfreie Prüfverfahren IZFP

nachricht Lightweight robots in manual assembly
13.09.2016 | Fraunhofer-Institut für Arbeitswirtschaft und Organisation IAO

All articles from Machine Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>