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Actual vs. rated wind power

07/14/2008 1:06 PM

I heard at a conference recently that wind farms actually only produce (on an annualized average) about 20% of their advertised capacity. Therefore, a 10 MWh installation will actually only produce 2MWh. It was also pointed out that 80% of this production was in the middle of the night in the winter months. However, the peak power requirements in this particular region was in the middle of the day in the summer months. Another problem I can see is that transmission capacity must be reserved for this 20 MWh, regardless of when it comes online.

Any thoughts or comments?

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#1

Re: Actual vs. rated wind power

07/14/2008 2:14 PM

That's interesting stuff. I live in a high flat region of the midwest US where they recently put in several new winds farms over the paost ten years. I hear there's more to come. Average annualized? i'd think the whole mess of them are way to new to calculate a return. As soon as you get close to getting an assesment they build more. I don't see what they're hurting. There's probably a down side, but i don't know.

30 miles to the South, there's a mile of coal cars that come form the Powder River Valley every ten minutes. Continuously. Makes me wonder for how long?

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#2
In reply to #1

Re: Actual vs. rated wind power

07/14/2008 11:03 PM

Given a 20% annualized return, I suspect the coal cars are safe for a long time. Anyway, the coal is probably shipped to China where they consume it without pollution concerns.

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#3

Re: Actual vs. rated wind power

07/15/2008 2:29 AM

Be careful of the sources you quote. I am currently at the National Renewable Energy Laboratory in Golden, Colorado attending a two-week intensive training on sustainable energy. The consensus among the instructors, all of whom have excellent credentials, is that, while wind is not a panacea (nothing is), it is by far the best source for replacing fossil fuel generated electricity to date. Twenty percent of rated capacity is absolute bogus. How would the manufacturers survive in a competitive market if the output of their machines were not as they claimed? Business is booming for large wind here in the States, so believe me when I say that wind farm developers and utility companies can be very picky about the product they choose. They do their homework. They seek out information from existing wind farms. This is a multi-billion dollar industry. They can't afford to spend their money frivolously. Go visit your local wind farm and take a tour. Ask questions. Get real information.

As for the peak production issue, there are certainly areas in which 80% of the winds blow at night during off-peak hours. There are also locations in which the wind blows best during peak demand. How about offshore wind? Does your source mention the continuous diurnal flow patterns for those farms? Probably not, if the information comes from whom I think it does.

Yes, there is opposition to wind energy, mostly by groups who are tied to fossil fuel industry. Their strategy? Feed false information about the technology to the NIMBY groups in places like Cap Code, MA. You don't think the oil and coal industries are a little concerned about being kicked off of their energy pedestals after a century and a half of dominance? Never mind that they peddle a dirty, finite resource. It's all about losing the bottom line.

I say again: please consider your source.

WindGenMan

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#4
In reply to #3

Re: Actual vs. rated wind power

07/15/2008 4:38 AM

Hi WindGenMan,

I beg to differ!

Here in the UK it has been found that wind power is not as effective as first thought! The problem being that during the winter months we have weeks of still air, and this is in the period when we need the most power to heat homes and cook our food. During the last three weeks here in the central part of England where I live, there has not been enough wind to turn a single wind generator, and as the cost of constructing and placing these things is enormous we are loosing out!!!

Here in the UK we are commited to producing power by renewables by 50% within 2020, and because of this we are looking at other ways than wind turbines to produce power! These include wave, tide and barrages accross two of our largest rivers. One of these barrages was first thought of in 1976, it is the Severn Barrage spanning accross a river mouth that is 21 miles wide! This could produce enough power to power 5 large cities, they main problem there has been the ecological destruction of important bird sites. But now this barrage has got the go-ahead.

Don't get me wrong, wind power has it's place, but it is very unreliable at the best of times.

Spencer.

PS. These days here in the UK they have had to increase the amount of trains as more and more commuters have abondond their cars, including me!

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#5
In reply to #3

Re: Actual vs. rated wind power

07/15/2008 8:04 AM

I agree with you.It is oil cos. who want you buy crude @$144/barrel. Otherwise Mr.Bush will become pauper.

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#6
In reply to #5

Re: Actual vs. rated wind power

07/15/2008 10:13 AM

Must every other technical discussion turn into an opportunity to cheap-shot President Bush with unsupported statements? Particularly when Democrats like Clinton also got rich on oil and had extensive relationships in the middle east (e.g., military exercises every year in Saudi Arabia to show support), it seems hypocritical and petty.

If you want to plost left-wing rants perhaps you should go to Daily Kos, MoveOn.org, or the Huffington Post. I come to CR4 to discuss technical issues and solutions, not politics.

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#7
In reply to #6

Re: Actual vs. rated wind power

07/15/2008 10:54 AM

Thanks rutleddc, I agree. My purpose in opening this thread was just to pass along some comments I had heard at a green energy conference and to start a discussion. Politicians come and go, but with fossil fuels, it's all go. We engineers have a duty to think and discuss rationally (which engineers should be able to do) all of our options. Allowing politics to come into the discussion is non-productive and futile.

As I get older I tend to think more and more like my father who hasn't voted in years, because he doesn't want to encourage the bastards.

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#17
In reply to #6

Re: Actual vs. rated wind power

07/15/2008 10:29 PM

Thank you!

milo

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#24
In reply to #5

Re: Actual vs. rated wind power

07/18/2008 4:47 PM

you are off topic and full of political nonsense. Please get a log in and present facts to back up your immoral attitude.

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#18
In reply to #3

Re: Actual vs. rated wind power

07/15/2008 10:32 PM

Great demonstration of Seeing both connotation and denotation of the original question!

milo

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#8

Re: Actual vs. rated wind power

07/15/2008 11:51 AM

I find it hard to believe that anyone savvy enough to fund and construct a wind farm would do so without checking the local conditions. I learned a rule of thumb some 20 years ago, that an average daily wind speed of 14 mph would be sufficient to make wind power generation economical. With the rising cost of more traditional (well, it's a recent tradition) fuels, that may be even lower today. If there's no meteorological data (hard to believe) for a given location, all one needs is an anemometer and a year to spare to find out if your wind farm location choice is a useful one...

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#9

Re: Actual vs. rated wind power

07/15/2008 12:28 PM

Once they have collected the tax credit - do they really need any wind?

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#10

Re: Actual vs. rated wind power

07/15/2008 1:18 PM

I would like to start by saying that when choosing a wind turbine, one must look at the manufacturer's power curve. This curve will show the amount of power that can be produced at certain wind speeds. (check out the bottom of this file for the GE power curve for this model. You will notice that for this particular model the rated power is at a wind speed of 14 m/s. If you want to see the problem, check out this wind map...it's canadian so use your imagination if you aren't one of us. Notice how there is barely any (or no) 14 m/s wind? Where are we to achieve this awesome 3.6 MW of rated power?

I believe this site operates on an average wind speed which would mean, to me, that the average wind speed in my area is 6 m/s (at 80 m high) consistently throughout the year. This is actually a half decent speed; at least it would seem it is since there are 300 or so 1.5 MW turbines cropping up in South-Western Ontario. But, for the wind turbine mentioned above (that probably cost almost 3 million $) only 400 kW would be produced on average...or 3.5 GWh throughout the year. When I look at wind turbines, I always look to see how much power can be produced in my area...especially since these things will rarely if ever reach their rated power output. Of course this isn't 100% right since there is some variability. The turbine could be getting 3.6 MW during the apex of a storm and it could get 0 during the calm after the storm

Also, air is denser when cold and produces more energy per m2 of span...which is why wind power is favoured up in the chilly north or just in winter in general. Solar panels are better in the summer since there is more sunlight but lose some of their output in the winter since the sun is further away. <-- note that I don't have quotes to prove this, but these are things my professors have said in class...

Hope I helped someone, somewhere!

Achilles

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#11

Re: Actual vs. rated wind power

07/15/2008 1:42 PM

FLASH - i just heard a new one today:

There's a guy that wants to fly (like a kite) a multi-prop turbine up to 15000 feet where there's a contant wind. Piping the energy down an umbilicle cable/teather.

Sounds like a good idea to me.

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#12
In reply to #11

Re: Actual vs. rated wind power

07/15/2008 1:53 PM
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#13

Re: Actual vs. rated wind power

07/15/2008 2:26 PM

If the percieved problem is that the wind is not constant, flying turbines aloft, up to constant wind currents could overcome this.

It's possible that i didn't complete my thought/comment with the last post.

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#14

Re: Actual vs. rated wind power

07/15/2008 4:56 PM

My understanding of the original comment by "thermo" is that it is in reference to utility scale wind farms. Wind farms are always located in areas in which the average wind speed at hub height are sufficient to drive the turbines at or near their rated capacity the majority of the time. In fact, governing systems on newer turbines are largely used to regulate rotor RPM, because blade designs are remarkably efficient in harvesting energy from the wind. Generator over-speed is more of a challenge in newer machines than is insufficient power output.

But, don't just rely on my--or anyone else's--input in this forum for your information. Start with http://www.nrel.gov/learning.html. Then visit your local wind farm, if you have one, or visit one on the internet.

Again, the best evidence of wind generator technology efficiency is in the economics. The U.S. is a nation where ROI drives investment behavior far more than good intentions. Wind turbines have an excellent payback period, much better than other energy sources available at this time, and there are still very large areas of untapped wind resources around the world. The probability of meeting the most ambitious of renewable energy portfolios standards is extremely high. Unfortunately, as evidenced by the content of this particular forum, ignorance is the by far the biggest obstacle to reducing our dependency on costly, non-renewable energy sources.

WindGenMan

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#15
In reply to #14

Re: Actual vs. rated wind power

07/15/2008 6:53 PM

Thank you "windgenman" for taking the time to enlighten us "ignorant" and unwashed engineers. It is truly unfortunate that, when one who has possession of relevant knowledge and is asked to share it in a forum such as this, that said person adopts a superior attitude and makes such condescending comments. We all recognize your demonstrated authority in all wind-related matters, but just because we wish to reach your Himalyan heights of knowledge is no reason to call us "ignorant". I've always thought that the purpose of this forum is to encourage dissemination of knowledge without bias and thereby, furthering the cause of engineering as a whole.

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#16
In reply to #15

Re: Actual vs. rated wind power

07/15/2008 9:20 PM

Sorry. Not my intention. I am still learning how to respond within this venue without becoming defensive. I deal with a lot of public misinformation about wind in my line of work, which I find very frustrating. I live in California where the grid is pushed to its limit on a daily basis and there has been no new construction of power generation facilities in over 15 years. Many proposed wind farm developments are on hold because of the spread of false information. In the meantime more rolling blackouts are likely.

Thank you for calling me on my arrogance.

WindGenMan

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#19
In reply to #16

Re: Actual vs. rated wind power

07/16/2008 9:20 AM

Don't know if any of my info was wrong, but if it was, I wouldn't mind knowing what I was wrong about (especially since what I wrote was more based on what ive learned over the last 2 years, not just regurgitated oil-crapsense).

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#20
In reply to #19

Re: Actual vs. rated wind power

07/16/2008 1:33 PM

Amen, especially since mine was (mostly) learned 10 times longer ago than yours. I saw no direct refutation or update to my stated figure of 14 mph sustained wind being the typical minimum for efficient, effective power generation. If that HAS changed due to improved technology, I'd like to know about it rather than remain ignorant and spout gibberish...

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#21
In reply to #20

Re: Actual vs. rated wind power

07/16/2008 9:05 PM

I've been trying to address (or "refute" as you call it) all of the issues brought up, but I have also have been attending a workshop, which has limited my time.

Siting a wind farm involve more than just wind maps. Wind maps provide a very general profile of wind energy potential and no developer would rely on such data to site a multi-million dollar project. That would be equivalent to using a globe to find your neighborhood Starbucks. The assessment process involves the use of sensors (i.e. anemometers, wind vanes) and data loggers, plus archived meteorological data obtained from permanent weather stations, to study the wind speed pattern over a several year period. Also measured are air pressure and relative humidity to determine air density trends which, together with the wind speed profile, provide a good analysis of the wind energy potential of a proposed site. This is just a small sample of the work that goes into siting a wind turbine.

As for the 14 mph wind speed comment, are you speaking of large or small scale wind turbines? With large scale turbines, no developer would even look at a potential wind farm site if the average annual wind speed could not run the generators at or above the rated capacity of the machines. The "rated capacity" of a turbine is derived from the power curve. The rated wind speed is standardized for large turbines so that a particular manufacturer cannot report a higher rated output at a different wind speed to make their machine look better. In addition, the manufacturer must produce a power curve for their product that has been verified by a third party, such as NREL. Siting a wind farm where the annual average wind speed is 14 mph wouldn't make economic sense. But there are numerous sites where the average wind speed is easily 24 to 30 mph. According to the U.S. Department of Energy, based on these wind speeds alone the world's winds could theoretically supply the equivalent of 5,800 quadrillion BTUs (quads) of energy each year--more than 15 times current world energy demand. This figure does not include offshore sites. So, to answer your question, you are right in stating that an average wind speed of 14 mph is not enough to power a wind farm. Theoretically, there are numerous small wind turbines which produce close to their rated output at that speed. However, there is enormous wind energy potential all over the world that can be harvested by current large wind turbine technology. The only "technical" challenges now facing wind turbine manufacturers is that of producing enough turbines to fill current orders. Right now, the waiting list is two years. This fact alone seems testimony enough to the viability of this technology.

for more information on wind please visit:

http://www.awea.org

http://www1.eere.energy.gov/windandhydro/

http://www.nrel.gov/wind/

WindGenMan

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#23
In reply to #21

Re: Actual vs. rated wind power

07/17/2008 11:46 AM

Thanks - update appreciated!

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#22
In reply to #16

Re: Actual vs. rated wind power

07/17/2008 2:52 AM

"I live in California . . . there has been no new construction of power generation facilities in over 15 years."

Well; not exactly. I work for a large municipal utility in Northern California. We recently built a 500MW gas turbine plant that came on line in 2006 with the slim possibility of adding another 500MW to that plant in the future. It remains to be seen whether it will be feasible or not when the carbon policies are finalized.

During the recent relicensing of our hydro project, approval was granted to build a 400MW pumped storage facility. Granted, it will be a few years before construction will take place but the powers-that-be say it will be built.

Also in our portfolio is the addition of 21 3MW Vestas wind turbines to our existing wind farm; the last of which came on line in November 2007. There are plans to expand the capacity of the wind farm further within the next few years (an additional 120MW I think).

I have mixed feelings about the wind turbines. Our peak wind occurs during summer (also our peak load season) but it comes at night when demand is lower. There is no doubt that our wind turbines cannot replace base-load units so, in that respect, I am not a proponent of wind power. I do, however, like the idea that we are planning on using the night-time peak wind in conjunction with the future pumped storage facility. The idea is that we will run the hydro units during the day when everyone is running their air conditioning and demand is high, and then at night use the wind energy to run the water back up the hill when demand is lower. In my opinion, this will be an excellent utilization of wind power.

I can understand the frustration with misinformation. I have always heard (and continue to hear) one of the biggest complaints people have with wind turbines is the noise they create. I had never been near a wind farm until this past January when I received training on our new Vestas turbines. I was quite surprised to find no objectionable noise from any of the machines. I'm sure that different types of turbines have different noise levels but I am equally sure that a majority of the people perpetuating the noise rumor heard about it from a friend who was told about it by some guy who is dating a girl who read about someone who saw it on youtube.

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#25

Re: Actual vs. rated wind power

07/22/2008 12:27 AM

Professionalism please gentlemen. All power generation plants have a nominal power generating capacity called the name plate or rated capacity. All produce less than their rated capacity in real terms due to maintenance and other issues. The degree of underutilization of wind systems is generally greater than that of fuel based systems but this is naturally figured into their cost justifications.

The type of wind turbine also has an effect. Variable pitch prop systems generally have higher efficiencies relative to their rated capacity than non-variable systems, but they are somewhat less efficient at capturing total wind energy available. The real advantage they have is making power that suits the grid.

The very important and somewhat disappointing factor in the cost effectiveness of wind power is the durability, serviceability, and longevity of wind turbines. These are engineering issues that can be with persistence improved. Ignoring the fact that wind turbines only produce power when the wind blows is neither engineering sense nor political sense. I would rate it as non-sense.

As a result I and many others are working on new means.

Best regards,


Mr. Gee

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#26
In reply to #25

Re: Actual vs. rated wind power

07/22/2008 7:58 AM

What are these new means? You piqued my interest!

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#27

Re: Actual vs. rated wind power

07/22/2008 2:36 PM

Less than 27% annualized would cause financial collapse

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