Power housing: Copper wiring stretches from a prototype of a new kind of generator, which was designed with the variability of wind speed in mind.
Exro Technologies
A more efficient generator could convert more of the wind's energy into electricity.
ExRo Technologies, a startup based in Vancouver, BC, has developed a new kind of generator that's well suited to harvesting energy from wind. It could lower the cost of wind turbines while increasing their power output by 50 percent.
The new generator runs efficiently over a wider range of conditions than conventional generators do. When the shaft running through an ordinary generator is turning at the optimal rate, more than 90 percent of its energy can be converted into electricity. But if it speeds up or slows down, the generator's efficiency drops dramatically. This isn't a problem in conventional power plants, where the turbines turn at a steady rate, fed by a constant supply of energy from coal or some other fuel. But wind speed can vary wildly. Turbine blades that change pitch to catch more or less wind can help, as can transmissions that mediate between the spinning blades and the generator shaft. But transmissions add both manufacturing and maintenance costs, and there's a limit to how much changing the blade angle can compensate for changing winds.
ExRo's new design replaces a mechanical transmission with what amounts to an electronic one. That increases the range of wind speeds at which it can operate efficiently and makes it more responsive to sudden gusts and lulls. While at the highest wind speeds the blades will still need to be pitched to shed wind, the generator will allow the turbine to capture more of the energy in high-speed winds and gusts. As a result, the turbine could produce 50 percent more power on average over the course of a year, says Jonathan Ritchey, ExRo's chief technology officer. Indeed, in some locations, the power output could double, says Ed Nowicki, a professor of electrical engineering at the University of Calgary, who has consulted to ExRo.
The generator works on the same principles as many ordinary generators: magnets attached to a rotating shaft create a current as they pass stationary copper coils arrayed around the shaft. In ordinary generators, all of the coils are wired together. In ExRo's generator, in contrast, the individual coils can be turned on and off with electronic switches. At low wind speeds, only a few of the coils will switch on--just enough to efficiently harvest the small amount of energy in low-speed wind. (If more coils were active, they would provide more resistance to the revolving magnets.) At higher wind speeds, more coils will turn on to convert more energy into electricity. The switches can be thrown quickly to adapt to fast-changing wind speeds.
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A design that draws on jet engine technology could halve the cost of generating electricity from wind.
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Has someone already coined a new term, Windergy, for the sector?
Couple this to FloDesign's turbine
Coupled to FloDesign's jet engine-inspired wind turbine, we'll have a game-changing wind power source.
This is a simple engineering improvement which makes a big difference. Often the simple inventions are the ones which have huge impacts.
These new generators (with a 57% increase in electricity generation) make the investment in wind technology so much more attractive.
Thanks
Brian Glassman
Innovation Management Commercialization
AXVC has developed a 98% efficient generator that doesn't use any magnets. One market they are going after is wind generators because they can handle very low wind speeds. Only one of many applications. Press release here.
http://www.axialvectorengine.com/press_release-82.html
I know it's picky of me but Technology Review is a technology magazine. You will therefore understand my disappointment when I run across sentences like this one:
As a result, the turbine could produce 50 percent more power over the course of a year, says Jonathan Ritchey, ExRo's chief technology officer.
What's that quantity we get when we integrate power over time called? And why did neither your reporter nor the CTO of a company that produces generators know it? Has someone, perhaps, been copying text from press releases written by marketing weanies?
You're right, and it's not being picky at all, a technology mag shouldn't make these mistakes.
It seems unlikely to me that this invention will greatly improve energy harvest (yes ENERGY) from wind turbines in high quality wind resources, especially, as mentioned above, for tall megawatt scale turbines that suffer less from wind power variance. Still, even a few percent more energy harvest would be competitive if the generator costs the same (or even less).
The other invention covered on this site, Tubercles, combined with this switch coil generator, could hugely improve the economics of small wind turbines in relatively poor wind resource areas. Like small distributed (eg homeowner) systems.
In my mind though, the biggest potential for wind in the future will still be large megawatt class 3 bladed (perhaps 2 bladed as well) turbines in high wind resource areas like the Great Plains and offshore (a bit further in the future). Both the Tubercles and the switching coil generator inventions would be less radical improvements here than they will be for smaller systems in lower wind resource areas. But the advantage could be very significant still.
One thing is clear now, wind is already very competitive and is going to help a lot in getting large amounts of clean energy, and with all the innovation still going on, it's only getting better.
I went to Exro's website and was surprised that there too there is confusion between energy and Power.
In addition, I think I've some knowledge about electrical motors/generators and this article didn't help me understand Exro's innovation. Maybe it's on purpose, for confidentiality reasons, but it makes it difficult to gauge whether it's a true innovation or not.
From a technical point of view, bigger motors/generators are usually more efficient than smaller, even at low power (this is a major difference with Internal Combustion Engines).
Electrical motors have been used in locomotives for a century now, because they work well in a wide range of speed/torque. One innovation that appeared soon in locomotive motors was to switch coils wiring between parallel and series depending on speed. Is that what Exro is doing?
That being said, it's great that motivated people try to find better technological solutions and especially in the energy sector, which really needs it!
ExRo appears to be working with prototypes of only a few kiloWatts. As you say, going bigger, especially to multi megaWatt scale, means the generator is inherently more efficient already, even at lower speeds. But this innovation is about quickly throttling up or down, and then just for a moment even big generators lose quite a big amount on efficiency. Since the coils can be used individually, a number of coils can operate at peak efficiency when the wind falls, and a number would simply be off. If there are enough coils (and the image shows there are) then it could mean the generator always operates close to peak efficiency even in quickly falling and rising winds.
If the wind turbine is situated in a high wind resource area (and they should be, since that's the economical resource), one would expect less sudden falling and rising of the wind, especially for those big multi megaWatt machines which are tall enough to harvest high and consistent wind speeds.
So it would appear that the advantage wouldn't be as huge as claimed for those turbines. Some big machines in good areas already get more than 40% capacity factor. Would this innovation give 60% or more? It seems unlikely. Perhaps when combined with vortex generators (Whalepower) such high capacity factors could be achieved in really good locations.
40%? at the mouth of a canyon, maybe. or if you cheat like crazy on the specs.
15% is what the local windmill cooperative (www.windshare.org) expected, and 10% is about what they got.
If you do not have substantial wind resource then don't build turbines in your area. Duh.
35-45% is typical for the best wind resources. Since there's so many improvements in the pipeline that increase capacity factor - just read the articles on this site about Whalepower, ExRo, Catch the Wind etc. - it appears a substantial improvement can be had here. And there's of course a continued development towards bigger taller turbines (although it's not moving as fast as in the past). I wondered how much of an improvement it would be in real world performance when all these upgrades are combined.
There's a wind farm in New Zealand that gets close to 50% capacity factor, the world record I think but haven't checked on others recently. But perhaps 50% will be standard in the future with all these upgrades combined.
I don't know why but I think is got to be something really close to this. Nuvinci CVT
http://www.youtube.com/watch?v=kVPjhmTThPo&feature=related
And that will increase the variations needed with the differents wind's speed very quikly.
And I mind something similar to the Nuvinci
Just to clarify--the claim is not that it will produce 50 percent more energy over the course of a year. But that on average, over the course of a year, the power output from the turbine will be 50 percent higher.
Why would this interesting type of variable speed generator not be even more appropriate for recovering kinetic energy for electric automobiles whose axle speed varies constantly?
Why not ust this in HEV / EV's?
Because an existing industry is all ready in place for motors on HEV/EV size. Manufacturing is well understood and they have come down the cost/volume curve.
Yes, EVs and hybrids should be an excellent application since they are throttled a lot, they have large and sudden variance which normally lowers the electric motor's efficiency substantially substantially below peak efficiency.
The EV industry is in it's infancy so I don't see why switching to different traction motors is a big deal cost-wise.
Any application with throttled electric motors should do. Electric motors powering compressors that are throttled regularly etc.
I believe the term is "Wenergy". About the Flo Design concept, it would only hamper this concept. I do think the "Whale Bump" blades would help it. Increasing lift range and power output would keep more of the coils active. Now too that Ocean Based windfarms have been proven to interfere with currents and agitation of the surrounding water that we should fight them with much more aggression. "Wenergy" is to reduce the footprint, not make mud puddles.
Yes, I also think this would work well with the Tubercles things. Of course, the advantage isn't totally cumulative for various reasons, but it should be a large effect still.
So the key is Scalable design. A claim region gets the lighter end of the scale. A generator built for an area with higher more consistent speeds would be scaled up. That would make it hard to really say what kind of megawatts to expect.
The point is, I think, that this generator would allow power generation from a wider range of wind speed than those presently available. In areas where wind speed can vary significantly throughout the day, this design, if successful, will take advantage of a larger percentage of the wind energy available by automatically scaling up or down the capacity if the generator with the available wind speed.
Although not explicity stated, i believe this technique amounts to pole switching. Pole switching has been implemented on motors ranging from washing machines to wind turbines for years. The basic concept is to use a high pole count winding configuration at low speeds & a low pole count winding configuration at high speeds. This has the effect of giving the turbines a wider power-speed range than would otherwise be possible without pole switching. I believe that these guys are just doing this electronically instead of of with relay or contactor (mechanical) switches. The "innovation" is more in the circuit than in the machine. The are probably using thyristors to commutate the currents to the proper coils at the opportune times. If this is the approach, I am skeptical that this method is at all defensible as it has been applied elsewhere in many embodiments...
Since the 87% of the land mass of the earth has only Class 2 winds, it would seem logical that wind turbines should be made to perform well in Class 2 winds. After all over 2 Billion people live in these areas.
Power is Equal to the Swept Area of the Rotor blades times the cube of the velocity of the wind, So, P = A x V cubed (add the correction factors)
Larger Rotor Areas will solve that problem, yes?
The problem is that the Cube in the formula comes into play very early. Example; if the force on your 1kW turbine is 20kG at 10mph, and nothing else changes, at 20 mph the force cubes to 8000, yes? 20 x 20 x 20 and if the wind goes to 40mph, 8000 cubed is rather large.
The solution: A rotor blade that can change it's Area, yes? From 100% to nearly 0 to meet the changing wind conditions.
I did that many years ago. WWW.AppropriateEnergy.com will show you how.
All my turbines are rated for Class 2 operation and warranted for Typhoon areas.
PS: Wind turbines are often wrongly called "Wind Generators". To the best of my knowledge three things Generate Wind, The Sun, Politicians, and a good bowl of Beans.
RAB
I have had solar systems in the past, and they do work quite well. The problem with wind generators in my part of the country is electrical storms and the fact that there is no inexpensive way to ground the generator to protect it from lightning strikes, which effectively cooks a wind generator. Sitting on top of a rock on, top of a 30' tower, is not healthy for electronic controls.
Think aluminum/iron/copper rod on top of the nacelle? Why not, just electrically insulate it well enough so the lightning current flows virtually completely to the ground rather than through the wind turbine system.
I bought a little generator on ebay and some wind turbine blades at
windynation
It is pretty fun. I get almost 400 Watts of power in 22 mph wind!
Anyone who likes building stuff should try it. It is really not that hard.
MPPT for small (or large) wind is probably better overall which is already in wind grid tie inverters (Windy boy, Aurora etc.) and the MidNite Solar Classic charge controller for battery based systems. A wind turbine doesn't need to change blade pitch to optimally capture energy from varying wind speeds although it is useful.
Unfortunately, there is a lot missing from this article regarding how wind turbines work, small or large and most magazine articles seem to get power and energy wrong (watts vs. watt-hours).
But one thing for sure, 50% more of 0 is still 0 if you don't put the turbine where there is wind in the first place.
boB
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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SVE
51 Comments
very cool
I'm not sure how well it would do at the megawatt scale power levels as claimed. But I think it would work well at lower level applications like 10's of kilowatts. These frequently occur for small wind turbines and small seawater wave generators. How do they switch the coils in and out? Do they use relays which have low loss or transistors which have higher losses?
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Kevin Bullis
178 Comments
Re: very cool
I believe the plan is to use transistors for smaller turbines and lower power levels, and relays for larger turbines.
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