Wind Turbine power output is increased ten-fold by careful spacing, and direction of rotation, when compared to existing best practices.
Click image for video surveyGuest post by Roger E. Sowell
Summary: A new study from CalTech shows that wind-turbine spacing, location, and direction of rotation can increase average power output per acre (hectare) by ten-fold, compared to existing best practices. Professor John O. Dabiri of California Institute of Technology (CalTech) published a paper describing the impact on power production of spacing, location, and direction of rotation on vertical-axis wind turbines.
For images and video, see http://dabiri.caltech.edu/research/wind-energy.html
A preprint of the paper is available at http://dabiri.caltech.edu/publications/Da_JRSE11.pdf (675 kB)
VAWT (vertical axis wind turbines) that are spaced approximately 4 diameters apart, with adjacent VAWTs rotating in opposite directions, yield a ten-fold increase in power output per unit of land area, from 2 – 3 Watts per square meter of land, to 21 – 47 Watts per square meter when compared to modern horizontal-axis wind turbines.
This has great implications for new wind-farm projects, especially the economics and environmental impacts. It does not, however, address the Achilles heel of wind power, the intermittency of power production and the need to time-shift power production by some economic means of grid-scale storage and discharge.
From Dr. Dabiri’s paper:
Abstract
Modern wind farms comprised of horizontal-axis wind turbines (HAWTs) require significant land resources to separate each wind turbine from the adjacent turbine wakes. This aerodynamic constraint limits the amount of power that can be extracted from a given wind farm footprint. The resulting inefficiency of HAWT farms is currently compensated by using taller wind turbines to access greater wind resources at high altitudes, but this solution comes at the expense of higher engineering costs and greater visual, acoustic, radar and environmental impacts. We investigated the use of counter-rotating vertical-axis wind turbines (VAWTs) in order to achieve higher power output per unit land area than existing wind farms consisting of HAWTs. Full-scale field tests of 10-m tall VAWTs in various counter-rotating configurations were conducted under natural wind conditions during summer 2010. Whereas modern wind farms consisting of HAWTs produce 2 to 3 watts of power per square meter of land area,
these field tests indicate that power densities an order of magnitude greater can potentially be achieved by arranging VAWTs in layouts that enable them to extract energy from adjacent wakes and from above the wind farm. Moreover, this improved performance does not require higher individual wind turbine efficiency, only closer wind turbine spacing and a sufficient vertical flux of turbulence kinetic energy from the atmospheric surface layer. The results suggest an alternative approach to wind farming that has the potential to concurrently reduce the cost, size, and environmental impacts of wind farms.
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@ur momisugly pofarmer, re spacing on wind turbines and growing crops. True what you wrote, however, this research was done with necessarily small turbines, likely for cost reasons. Also, this was done in a desert north of Los Angeles where very little grows except scrub. My statement, as you quoted above, has more to do with the lush farmland of Kansas, Nebraska, Iowa, where the wind blows over vast areas. Also, as the size of the turbines increases, the spacing will also increase. The photo shows 1.2 kW machines, whereas commercial machines will be more like 1.5 to 5 MW. I suspect a decent-sized farm machine can easily navigate the space.
Roger Sowell says:
July 16, 2011 at 6:23 pm
Some of the comments above, which appear to me to denigrate wind power, ……..
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It’s the ROI (return on investment) , that will kill these contraptions every time.
They suck money (subsidies) out of the economy, in return for higher energy prices.
In an attempt to assuage the guilt pressed upon us, by those all-knowing saints, who only wish to lead us to their promised land.
We must:
1) Trust climate models
2) Forego logical thought
3) Fill in the rest yourselves, I’m tired.
anticlimactic says:
July 16, 2011 at 7:00 pm
If wind turbines ever do become viable as a source of energy I would think it best if all the output was channelled in to systems like Electric Mountain in the UK.
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Thanks for the info on Electric Mountain. From a google search, resulting in several websites, “Electric Mountain” consists of two pumped storage power plants that were built in the 1980’s as grid-wide peak shaving facilities. They buy power from the grid at night (presumedly at a reduced cost), to pump water to upper reservoir and then let the water flow downhill during the day (as needed) producing electricity which they sell back to the grid (presumedly at a higher cost than the night rate).
Thus the UK grid does have about 2000 MW from these two plants (during the day) that act as “spinning reserve” for the variations in windpower generation. Perhaps as anticlimatic suggests it would be better to have pumped storage facilities where all the windpower was used to pump the water to the higher reservoir, with a separate set of turbines used to generate the electricity as the water flows downhill. Of course if the wind didn’t blow for several days…..
@ur momisugly Stas Peterson says:
July 16, 2011 at 8:39 pm
“I have frequently traveled through the California “wind valley” windmils near Palm Desert on I-10. Most times only one or two of hundreds are operating.”
That is utter BS – maybe it was a slow day, or maybe there wasn’t much power demand at the time, but while it is common for some not to be turning (often based on how they are positioning) to write that 1 or 2% of them are actually in use is rubbish.
Need to read Renewable Energy without the Hot Air by Mackay. There are not enough mountains in the UK to pump up the water to use pumped storage to make wind farms viable.
@Stas Peterson
So, what is wrong with importing power? Is there some law that requires every state to produce every single commodity in-state? Are you equally angry with the Northeastern states for importing hydroelectric power from Canada? How about the Cook nuclear power plant on Lake Michigan, and in Michigan, that supplies power to Indiana? How do you feel about manufacturing cars? California is the single largest automobile market in the US, yet manufactures almost zero cars in-state. Aren’t you incensed that cars are imported into California? Are you also outraged that California doesn’t have sufficient fresh water within its own boundaries, and must import water from the Colorado River? If not, why then are you so outraged over importing electricity?
Re the imported coal power, that will be ceased in a few years because California’s legislature (rightly or wrongly) passed a bill that was signed into law that prohibits importing any power from a source that has a higher heat rate than that of a modern combined cycle gas turbine plant.
Re you not seeing many wind-turbines operating, that is not surprising considering the wind blows mostly at night in the mountain passes containing the wind turbines. British experience with wind turbine capacity factor has to do with their local wind conditions, and has zero bearing on the realities of wind power in California. As cited above, California’s wind turbines generate on average at about 22 percent of rated capacity.
oldengineer
“I’m not sure why VAWTs lost out to HAWTs. The VAWT problems all sound like engineering problems that could be over come.”
I’m guessing the very long unsupported axle subjected to flexing for every rotation of every blade would have something to do with it. The problem could be reduced and the expected life increased to a very long time by beefing up the axle, but the problem remains. Fatigue of the axle is much easier to deal with for a much shorter axle supported at both ends as in a horizontal design.
Roger Sowell:
“Re the imported coal power, that will be ceased in a few years because California’s legislature (rightly or wrongly) passed a bill that was signed into law that prohibits importing any power from a source that has a higher heat rate than that of a modern combined cycle gas turbine plant.”
Am wondering how they intend to filter out the unacceptable electricity.
47 watts per square metre! That equates to a temperature of -103C (MINUS 103 celcius).
Heck, my back yard radiates more than that even in the winter.
I’m sure the wind power critics recall how “perfectly” the coal fired generating plants operated last winter in Texas, and how the natural gas fired backups to those “perfect” coal fired plants reacted “perfectly” in response to the failure of those “perfect” coal fired plants.
While wind power can be stalled because of a lack of wind, it usually does not last more than a few hours, and it does not cover a large region so the next farm over can still be operating. If one unit out of 50 is out for mechanical repairs it is no big deal, and the repairs can happen quickly with spare parts on hand and the unit started back up within hours.
Coal fired plants sometimes have to limp along at significantly less than full capacity for months because they cannot be taken completely out of service for the days required to compete needed repairs. To repair some equipment the whole unit has to be taken down and there cannot be spare parts for every thing. It takes 16 hours to bring a coal plant back into service from a cold stop, and that’s after whatever time it takes to take the unit out of service, find out what parts are needed get those parts shipped in, and complete the repairs.
Wind isn’t perfect, but nothing else is either.
I am quite stunned at the quoted 20+% of rated capacity for wind production in California is being hailed as some kind of super achievement.
The link Roger posted shows a peak power demand of around 31000 MW, or 31 GW – and installed wind capacity is supposed to be 3100MW or 3.1GW. Curiously then, the installed capacity of wind generation within CA is thus around 10% of required peak demand – and THIS capacity is actually working at roughly say 25% efficiency (according to other posters), meaning that in REAL terms, CA wind is producing around 2.5% of CA power demands? And this is supposed to be good? To my mind, assuming I have interpreted the figures correctly, the wind capacity and its actual production are a drop in the proverbial ocean! I hope the capital costs were worth it!
I am not against wind power but on an industrial scale it is simply not very economical in my opinion because of the requirement to cover periods of non-production. In my opinion, unless it is combined with very efficient storage systems, i.e. hydroelectric dams – it simply cannot provide enough power to be able to ‘switch off’ any single coal or nuclear genset.
Reading the quoted 22% of rated capacity sounds all well and good – but it’s peanuts in terms of the actual power demand! It would be more realistic to quote the real renewable generation figures to the general public – i.e, 2.5% of actual power requirements!
as a slight aside – I note that the graph on that CSIRO link shows a difference of demand to Available resources of something around 10000MW – I am wondering what that is made up as presumably CA must have some hydro stashed away somewhere, or else some bloody big batteries! Either that or they have coal/nuclear gensets on standby or at reduced capacity? Just curious.
old engineer says:July 16, 2011 at 6:41 pm
I have never understood why pumped storage for load leveling has never been used with wind turbines. Pumped storage has been used for over 100 years around the world for load leveling.
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According to Wikipedia, there’s 21,000 MW of pumped storage in the US.
http://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity
The big Tehachapi wind farm is close to the Castaic lake / Pyramid lake pumped storage facility north of Los Angeles. That facility was built to level the day/night load of L.A. that gets a lot of power from hundreds of miles north (Bonneville), but it makes a nice storage pond for the wind farm.
It isn’t critical that pumped storage be nearby, as high voltage transmission lines are efficient over long distances, but the lines have to exist. It was a dirty little secret for many years that the Tehachapi wind farm couldn’t get the power out, and that SoCal Edison was paying for power not delivered. That’s fixed now with new transmission lines. You also have to remember that pumped storage is about 70% efficient measured from electricity in to electricity out.
It doesn’t really matter that the electricity production per square meter increases ten fold, if you have to put 20 times more windmills. What matters in the end is how much more money you have to spend to get that 10-fold increase in production, or how much energy produces each individual windmill, whose construction and maintenance cost is much more important than that of the land it stands on. That’s what efficiency is all about. Money vs energy, not land vs energy. Less land is only interesting if it means less money spent per kWH obtained.
Bystander:
Clearly, you suffer from reading difficulties. In response to my explanation at July 16, 2011 at 3:25 pm that concludes by saying;
“In other words, wind tubines do not provide any useful electricity to a grid at any time.”
You assert;
“That is a pretty ridiculous statement – if that were the case there would be no instances of wind power contributing energy to the grid (which it clearly does) and no instances of large scale wind deployments (which there clearly are).”
Clearly, you do not know the meaning of the word “useful” (which is very understandable in your case).
For a more full explanation of why electricity from wind turbines to an electricity grid system
(a) increases fuel usage,
(b) emissions and
(c) costs
of electricity supply read
http://scienceandpublicpolicy.org/images/stories/papers/reprint/courtney_2006_lecture.pdf
Richard
cwj says:
“While wind power can be stalled because of a lack of wind, it usually does not last more than a few hours, and it does not cover a large region so the next farm over can still be operating.”
Methinks you need to study some meteorology. Calm is usually due to a more or less stationary high pressure area which is typically several hundred miles in diameter. They also tend to stay around for several days or even a couple of weeks, particularly in winter. Storm systems (that provide too much wind) are usually somewhat smaller and much more mobile.
July 13 (the last day for which figures are available) Wind supplied 7.15% of California’s electricty.
http://www.caiso.com/green/renewrpt/20110713_DailyRenewablesWatch.pdf
That’s Domestic Wind, some wind-generated electricity was imported.
And, per Roger’s link, California’s not a particularly good place to put wind turbines. The Midwest is Much better. I think those Iowa turbines are averaging close to 33%.
What makes California strong is, they’re building more, and more Solar to make up for the fall-off of wind during the middle of the day. They’re also doing well with Geothermal. All told, they’re getting close to 14% of their electricty from Domestic Renewables, and that doesn’t include Large Hydro.
No, but he’s translating a German who is using the English word; that’s why the commas in the translation. He meant to use apostrophes: “The `Birds’ The”.
;p
Speaking of German, I wonder if Papageno could have used a couple of these. “Ein Vogelfänger bin ich, ja!”
old engineer says:
July 16, 2011 at 6:41 pm
. . . pumped storage for load leveling . . .
Available water where needed – west Texas? – is one issue.
Building dams is also costly and environmentally unfriendly.
A non-wind effort using pumped water from the Columbia River, and using the water for irrigation, recreation, and so on has been determined to return 13 cents on the dollar.
http://www.yakima-herald.com/stories/2008/12/19/bureau-of-reclamation-says-no-to-black-rock
An actual example of pumped storage can be seen using Wikipedia and Google Earth. Of interest is the “pumped storage” associated with Kinzua (kin-zoo) Dam in northern Pennsylvania. Read about it here:
http://en.wikipedia.org/wiki/Kinzua_Dam
Use these coordinates [ 41.839736 n, 79.002619 w ] to get a better look. Zoom out until you can see the entire reservoir and compare it to the small circular storage basin on the ridge-top to the south.
Maybe my presence affects the weather in some mysterious way — but most of the wind turbines I’ve seen around the world (and I’ve seen a lot of them) were standing still, even where there was an obviously strong wind.
Quite often they are already rusty, and local people usually hate them, for they are hideously ugly, especially when there are many of them.
Now, what should I believe: the socialist fanfare statistics promulgated here by Roger Sowell, or something that I see with my own eyes?
As far as “getting x% from renewables”, it’s full of hidden catches. Like not being available during peak (evening, etc.) demand. Like messing up the distribution system (some places have paid providers not to feed into the grid, it’s so much trouble). Like huge capital costs and airy-fairy unproven maintenance costs and performance. Like huge real estate footprints. Like the remoteness and (previous) beauty of windy places, requiring very long and very hi-tech expensive transmission corridors. Like having a narrow “Goldilocks” wind speed range. Like using about 10X the concrete and steel per MW capacity of conventional or nuclear plant. Etc.
Diffuse and dispersed energy collection is the exact wrong direction for development of societal power supplies.
The only thing that will increase wind turbine output 10x is to get the wind to blow all the time at the optimum speed. Impossible? No that’s what carbon tax will do. (or so the politico’s think).
Someone mentioned Mackay’s book..
Properly its called Sustainable Energy Without The Hot Air or “SEWTHA”
Find it here….http://www.inference.phy.cam.ac.uk/sustainable/book/tex/sewtha.pdf
Its a bit of an epic and written especially for the UK but gives a good idea of the sheer scale of the ‘energy problem’ Its obvious that few politicos have any science or engineering knowledge and simply dont ‘get it’. Recently and more by accident than design, I heard on my car radio Chris Huhne (I think) speaking in Parliament. He kept repeating his assertion that “windmills are ‘beautiful, I think they’re beautiful” (I felt physically sick listening to it and switched it off)
Yes, windmills look big and graceful and suitably huge (when you get up close) and certainly seem to be doing the business but are tiny compared to The Grid. Plus their output goes as the 3rd power of the wind speed. Trying to maintain a steady or constant output would be like doing brain surgery on a grease covered banana slide during an earthquake.
That is what kills them, the constant load variation and flexing destroys bearing and gearboxes and the load variations they feed into the grid does the same for ANYTHING connected to it, right down from multi GW nukes to your own fridge. The stop/start city driving analogy is a very good one. It/they wreck the machinery and drink fuel.
I like the idea of close together – use less ordnance, less risk of collateral damage and civilian casualties. All good!
I’ll wake up in a minute…