Wheels turning: The blades of CWind's wind turbine move an internal flywheel and several shafts that attach to small generators within the nacelle. In the lower image, a rubber wheel rolls on the inside wall of a flywheel inside a 65-kilowatt prototype turbine.
CWind
New design does away with the need for a complex gearbox.
A Canadian startup has developed a small prototype wind turbine that uses friction instead of a gearbox to convert wind energy into electricity. CWind, based in Owen Sound, Ontario, recently began work on a larger two-megawatt prototype. The company claims that its "friction drive" system is more efficient and reliable--and less costly to maintain--than conventional wind turbines, which are prone to expensive gearbox failures.
The blades on most turbines use the wind to turn a drive shaft connected to a gearbox. The gearbox manages the rotation of a second shaft that connects to a large electrical generator. The gearbox is the heaviest piece of equipment in a wind turbine's "nacelle" (the section at the top of the turbine tower). It's also a piece that's among the most vulnerable to failure. Sudden wind gusts put the gearbox under tremendous mechanical stress. Over time this can wear down or break the teeth off its metal gears.
CWind's design does away with the gearbox completely. Instead, the drive shaft is connected directly to a large metal flywheel. Hugging the outside of the flywheel are eight smaller secondary shafts, each connected to a 250-kilowatt generator and each lined with several specially designed tires that grip the surface of the flywheel. As the flywheel spins, it engages the generators by turning these tire-lined shafts. "We're using friction. It's not mechanically hard-coupled," says Na'al Nayef, a CWind engineer and co-inventor of the system.
Nayef says the system uses software to control the eight secondary shafts. The tires are also designed to temporarily slip if a wind gust causes the flywheel to suddenly speed up. This feature eases the impact on the generators. Each secondary shaft can also be disengaged from the flywheel if the wind slows down, in effect reducing friction and allowing shafts that are still connected to keep their generators operating at high capacity. Likewise, connecting more shafts, thus adding more friction when the wind increases, will engage idle generators. "We can operate the generators at optimal speed all the time," says Nayef, adding that tests on the smaller, 65-kilowatt prototype show efficiency gains over standard wind turbines of up to 5 percent.
CWind founder Paul Merswolke first pursued the design seven years ago after watching a documentary on the London Eye, a 135-meter-tall Ferris wheel on the bank of the River Thames. He saw that simple truck tires were used as "friction rollers" to turn the Ferris wheel and concluded that the same approach could be adapted for wind turbines. Nayef was brought aboard to come up with a preliminary design, and in 2004 CWind approached energy engineering firm MPR Associates in Washington, DC, for help on building a prototype.
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A practical peace of lateral thinking, a good idea always seems simple after the fact.
This solution would lend itself to water wheels as its another application held up by the need for a large expensive gearbox, the outside rim of the wheel would provide the runner track for the generator tires power take off.
Perhaps this could produce a low cost solution for third world power needs
If the flywheel has a certain mass, wouldn't it partially condition the rate of change of velocity (and thus power output) of the generators?
Also, is the minimum windspeed necessary to begin operation higher, or is the mass of the flywheel/generating system no greater than existing generator/transmission systems? In which case the first query is not relevant.
Friction drive can't be as efficient as gears because of the FRICTION.
In this system, during operation, there is no slip and therefore no energy lost to friction. Friction is why the tires pressed up against the flywheel also turn when it does; that is the source of the name.
The real genius of this device is that if the speed suddenly increases (or decreases for that matter) then the friction coefficient is quickly overtaken and the tires merely slip, rather than coupling the speed change into the generators. A traditional design prevents this from happening with a gearbox - but this is hard on the gearbox, as the article says.
FYI - gears have friction too.
durs, isn't there friction between gears also?
what has happened with the design presented earlier this year which uses coil energizing and no gearbox? this reminds me of a carnival ride.
An ant is a great design, but it is too bad when it enlarges to the one with the size of an elephant
When we disassemble a toy car, we can find almost all parts of transmission are made of plastic gears.
When we enlarge the toy car for 200 times, if the plastic gears still work properly? Th answer is NO.
when the power that th plastic gear transmission is small, the plastic material can afford the stress
and the heat generated during the power transmission can dissipate fast enough, but when the power increases
for hundreds of times, the small contacting area between one pair of gear does not increase so many times and
the stress of the contacting area will be too big for the plastics material, which leads to the failure of plastic gears.
Another factor may influence the transmission is the temperature of the contacting area, when the power is too big,
the plastic material is not good in conducting heat and the temperature of the contacting area may be so high that it
begins to soften the plastic material.
the ratio of CWind may be too small to drive the generator when the wind speed is not high, so the CWind is good only when
the wind speed is high.
When the power increases from 65KW to 1000KW, the surface of tire may melt into solid state and the device fails to work.
Here we need to know how about the efficiency of the transmission between the tire and the flywheel so it is possible to
estimate the temperature of the tire surface.
Some article said the tire of the F1 racing car may slip the car under some situation because of the high temperature
of the tire surface.
The price of the CWind may be another problem, the total price of eight small-size generator may be much higher than that
of a single bigger generator, the cost to synchronize the eight unsynchronous power to the power grid also should be considered.
An ant is a great design, but it is too bad when it enlarges to the one with the size of an elephant.
This was a perfect analysis. Thank you.
Agree with you on the info as presented in the article. The problems with heat and limited slip you specified can be designed around. An outer drum, driving an inner drum with an inflatable boot with friction material attached. This method is already utilized elswhere. Provide torque and speed ramp control via air pressure to segmented boot.
I was thinking that an approach something like an automatic transmission for a car might work, the pressure/velocity of the fluid could be used to determine how many secondary rotors are connected, and pressures/velocities too high wouldn't be channeled to do any work, so gusts wouldn't hurt the equipment coupled to the main flywheel. Then you wouldn't need a computer to run the thing.
Gearbox is a complex part in wind turbine and this new design is expected to reduce cost and improve efficiency of wind turbine.
Dr.A.Jagadeesh Nellore(AP),India
Wind Energy Expert
E-mail: anumakonda.jagadeesh@gmail.com
Manufacturing in the United States is in trouble. That's bad news not just for the country's economy but for the future of innovation.
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SirLanse
71 Comments
Wow a clutch
They invented a clutch.
The turned it inside out, but it is still a limited slip clutch.
Reply