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Wind turbines harness MRI tech

GE Global Research

GE researchers are applying more than 30 years of experience developing superconducting magnets for MRI systems to design an advanced generator for large-scale wind power.

The high-tech magnets in modern MRI systems encountered at the doctor's office may soon generate electricity from the wind, according to researchers at the General Electric Company.

MRI systems are the tube-like contraptions that make images of damaged hearts, torn ligaments, brains, and other body tissues. Instead of X-rays, the images are made with superconducting magnets, which are electromagnets made from coils of superconducting wire.


GE has spent more than 30 years working on the magnets in MRI systems and now thinks they can apply what they've learned to make a more powerful and cost efficient wind turbine. The U.S. Department of Energy recently granted the company's research arm $3 million and two years to get cracking.

The goal is a wind turbine that is close to three times larger than the company's largest model, able to operate in the 10 to 15 megawatt range. One MW can power between 240 and 300 U. S. homes per year, according to the American Wind Energy Association. Most wind turbines in the market are in the 2-4 MW range.

GE's new turbine technology is a direct-drive system where the shaft of the rotor blade connects directly to a low-speed generator that uses permanent superconducting magnets to generate power.

Conventional generators produce magnetic fields made of copper coils, "which are resistive and lossy and produce a lot heat and hard to design with in a compact manner," Kiruba Haran, a manager in the electric machines lab at GE Global Research, explained to me Wednesday.

All direct-drive wind turbines on the market today overcome this problem by using magnets made from rare earth materials. One problem is most easily mined rare earths today are locked up in China.

Superconducting magnets are also more energy dense than rare earth permanent magnets "so the machine tends to be much lighter, more compact, and would enable you to scale up to a much higher megawatt rating in an easier manner," Haran said.

These new direct-drive systems are also considered more robust than traditional systems that connect the rotor shaft to a gearbox, which steps up relatively slow blade speeds of around 50 rotations per minute to the 1,000 rpm range needed by most generators to create electricity.

According to GE, gearboxes work well in turbines currently deployed, but they get too expensive when scaled up to the larger next generation wind platforms eyed by the government and industry mostly due to their heavy, clunky materials and maintenance costs.

The superconducting magnets reduce weight requirements since they are able to generate high magnetic fields without using as much heavy iron. "With the superconductor, we are trying to get the best of both worlds — bring the machine size down and have no gear box," Haran said.

Doing this, however, is a challenge. For one, superconducting magnets operate at temperatures approaching absolute zero. The DOE funding, Haran said, takes away some of the financial risk involved with translating MRI technology to a wind turbine.

"The applications are different," Keith Longtin, a wind technology expert at GE said in a news release, "but the basic technology is the same."

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John Roach is a contributing writer for msnbc.com.