Transmissions are not sexy but they are essential to many mechanical devices. They allow components that turn at different speeds to work together. For instance, the blades of a wind turbine are not connected directly to the electrical generator inside. A transmission takes the relatively low rotational speed of the blades and steps it up to the higher RPMs needed to spin the generator fast enough to make electricity. Gears are the secret sauce inside any transmission. They are fairly reliable but if one breaks, it can be expensive to repair. And if it is located high on a wind turbine pylon or deep undersea in a wave power device, getting access to it to make a repair can be difficult.
At Texas A&M, doctoral student Matthew Gardner is working on way to replace mechanical gears with magnetic ones. If he is successful, smaller, lighter, and less expensive transmissions that transmit power more efficiently will be the result. His research is being watched carefully by several companies, including ABB, the global technology company headquartered in Switzerland.
Magnetic gears require less maintenance, create less acoustical noise and vibrations and are more durable than mechanical gears. If too much power is applied to a conventional gear, it breaks but when excess power is applied to a magnetic gear, it simply slips with no mechanical damage. In essence, it acts like a clutch built into the transmission that can absorb spikes in the load applied without breaking.
“Magnetic gears drew my interest because they represent a potentially disruptive innovation in the field of electric machines,” Gardner says. “Much of the research in electric machines represents incremental improvements on the technology that has been developed over the last few hundred years.”
One of the projects Gardner is working on is building a transmission for a wave energy generator. Ocean waves can have enormous spikes in energy. The transmission has to be able to absorb high torque loads over and over again reliably. By definition, repairing a broken component that is mounted underwater is a daunting and expensive job. “Our analysis found that using a magnetically geared generator would be about 50 percent smaller, 50 percent lighter and 25 percent less expensive than using a generator without any gearing for this wave energy application,” Gardner says.
In collaboration with the US Department of Energy and ABB, he has constructed a prototype transmission with magnetic gears that can handle up to 4000 newton meters of torque. Most magnetic gearing solutions to date are limited to about 150 newton meters of torque. Converting to pounds feet — the measurement of torque most of us are familiar with — 4000 newton meters is equivalent to 3000 pounds feet — nearly four times more than a Tesla Model S P100D.
“I am excited about the opportunity to make a disruptive change in the field of electric machines,” Gardner said. “Magnetic gears and magnetically geared machines offer the possibility to provide a significant, not just incremental, improvement in systems involving electric machines.” Anything that lowers the initial costs and ongoing maintenance expense of renewable energy systems is a welcome step forward on the road to eliminating carbon and other harmful emissions from fossil fueled generating plants. Lower renewable costs will also make nuclear power unprofitable. With magnetic gears, 100% renewable energy becomes a more realistic possibility.
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