Wind Power Number of the Day: 59.3%
by Michael Graham Richard, Gatineau, Canada on 06.30.08
59.3% -- Albert Betz calculated in the early 20th century that the maximum theoretical efficiency of a wind turbine is 59.3%.
50% -- Currently, modern wind turbines are efficient at about 50%, a very impressive number.
15% -- According to GE, when it entered the wind turbine market in 2002, the average wind turbine was out of commission about 15% of the time.
3% -- Nowadays, wind turbines are down only about 3% of the time. That helps drive the cost of wind power down and get the most out of each turbine. Uptimes can probably be improved even further.
8 -- Electricity produced by a modern wind turbine costs about 8 cents per kilowatt-hour.
5 -- Electricity produced by coal power plants costs about 5 cents per kilowatt-hour, but that is without counting the cost of "externalities" (air pollution, global warming, coal mining, mercury emissions, etc). According to a study by MIT, coal-produced electricity would cost about 8 cents kwh with a carbon tax of $30/tonne.
30% --Worldwide wind power capacity is growing at about %30 per year, and it should pass 100 gigawatts this year.
10,000 -- A farmer from Iowa who gives up 1/10 of an hectare for a wind turbine could earn about $10,000 per year, compared with about $300 for the same area if he/she grew corn for ethanol.
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Source: The Economist.
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8 cents is pretty damn good! Solar's much higher, though in the long term it probably has a bigger potential. thx for this
So our wind turbines today are at 84% of the maximum possible efficiency. Thats is pretty darn good. The price of coal can only go up, too.
And 100 GW of wind would be about 5% of total world electricity usage. Is that 100 GW number based on capacity or on average actual power output of wind turbines? I could put solar panels on my power capable of producing 10 kW of power at full sun in summer that over the course of the year produce an average power of 2-3 kW.
As for the hypothetical farmer mentioned in the last paragraph, I have a question. From the farmer's perspective trying to make money, it might make sense to use some land for wind (depending on the up-front cost and how deep his pockets are), but a more direct comparison to producing crops for ethanol would be production of another storable, transportable fuel. How much would he make if he had a wind turbine and used the power from it to produce hydrogen by electrolysis or methanol/ethanol from water and atmospheric CO2? This is the question for those of us trying to power our cars; yes, they will be PHEV soon, but fuels will still be needed for the non-electric stage and fuels produced by renewable energy would be great.
Hmm, I question that 59% #. I recently read in Popular Science how someone developed a wind turbine that used a string of fans to capture the wind such that the fans did not effect one another. This was developed despite the fact that someone before theorized that the maximum amount of fans you could have was 1. So, this 59% # is also very dubious. I'd have to do more research to find out what's really going on, but I don't really care that much.
That being said, I think the 59% # is reasonable considering how a wind turbine works. It simply doesn't seem possible to completely capture the energy on the wind using a fan.
Mmm, imagine solar power at 50%?
The more I read about wind power, the better it sounds.
8 cents sounds real good per kwhr if your paying 12 cents like we are here in S. W. Indiana, from coal fired plants, wonder where they're getting it for 5 cents, no where around here, TVA probably charges more than that from their dams.
Wow $10,000 compared to $300 per year, I know which one I'd pick. And for once the option generating more earnings is also the one that seems to be one that is ecologically more reasonable.
UP time means percent of the time that a wind mill could be generating electricity if the wind were blowing at the right speed. Number reported is much lower that what I might have expected. A minor point of clarification that totally changes the conclusion one might come to after reading this article. Here's the number that really matters.... Nationwide we have built 10s of thousands of new wind generators over the last decade or so. 10's of thousands more are in the works. Total contribution of wind to what's actually being generated is about 1%. Coal is still at 52%, nuclear at 20% (even though no nuclear power plants have been build for at least 20 years), hydro is about 7 and various fossil fuels like natural gas, propane, and diesel account for the rest. Article also neglects to discuss how many birds are being killed (It's quite a few) and what the impact of noise and landscape degradation is.
"15% -- According to GE, when it entered the wind turbine market in 2002, the average wind turbine was out of commission about 15% of the time."
I have my doubts about this number. It may have been true for the US, where at that time most windturbines still originated from the Californian windrush of the end of the eighties. But I am pretty sure that in Europe, where most windturbines were built after 1995, the average availability was much better.
In other words, without additional information, it is difficult to interpret the meaning of numbers. the suggestion that GE singe-handedly improved the worldwide quality of windturbines is certainly false.
@stradric;
Betz' law is not based on a particular wind turbine design, but on general considorations:
Air particles passing through a windturbine will transfer a part of their kinetic energy to the rotor, which in turn passes this energy to the generator which turns it into electrical energy.
By loosing kinetic energy the air particles, ofcourse, decrease their velocity. If the velocity of the air particles behind the windturbine becomes too low, you would get a "traffic jam" behind the windturbine and more and more of the wind will start too flow around the wind turbine rather than through it. Using some aerodynamic theory Betz used this consideration to get at this percentage of 59%.
This consideration is independent of the design of the wind turbine and therefore also still valid if you would place several rotors in series.
Jimmy,
When a cost of 8cent/kwh is cited for wind or 5cents/kwh for coal, it is usually the cost of generation only.
On top of generation you have distribution costs and a reasonable (or unreasonable) profit for the utility.
"In other words, without additional information, it is difficult to interpret the meaning of numbers. the suggestion that GE singe-handedly improved the worldwide quality of windturbines is certainly false."
I don't think it means that GE did it. Just that the stats comes from them, and that the industry as a whole improved quite a bit in recent years.