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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Don’t VAWTs have their own problems, besides being ugly?
VAWT rated power = 0.0012MW
HAWT rated power – 2.5MW or 3MW.
Is it just me or is this study comparing tiny little toy wind turbines to real full sized ones?
Aren’t Mythbusters usually surprised by the results when they go from models to full size?
They are also much better against avian critters.
Disadvantages:
http://en.wikipedia.org/wiki/Vertical_axis_wind_turbine#Disadvantages_of_vertical_axis_wind_turbines
Pretty cool stuff. I’ve always liked VAWT’s better than HAWT’s for their less clumsy design appearance, but believed them to be less efficient. Clustering them like this study suggests with the counter-rotation on adjacent turbines is a smart move. Now they need to work out how to keep birds away from them and keep the noise down. 30W/m^2 isn’t a lot of power for crowded islands like Britain though, and the intermittent wind problem isn’t going away anytime soon with few places suitable for pumped storage and battery technology too expensive.
DocWat says:
July 16, 2011 at 2:13 pm (Edit)
Don’t VAWTs have their own problems, besides being ugly?
These look quite good I think:
http://www.quietrevolution.com/gallery.htm
Birds produce CO2. CO2 evil. Die Birds Die! (That’s German for “The, Birds, The”)
The vertical axis turbines are less efficient than the current crop of windmills, but their increased density ‘overcompensates’ for this by gleaning the wake of upstream turbines. We get better output per unit of land, but increased density means more turbines, which means more capital cost. We’ll have to wait to see how this scales up in terms of cost/output and nuisance noise generation.
I remember reading about “egg beater” windmills 30-40 years ago. A big practical advantage then was that the generators are at the bottom, where they don’t need to be supported and are easy to service, rather than at the top.
DirkH — By “much better” with birds, do you mean they are better for the birds or do a better job of annihilating them?
I can see a man in the picture. Are these production sized or scaled down?
Zero times 10 is still Zero when the wind don’t blow.
This sounds great.
Then the wind doesn’t blow.
Ten times zero equals zero.
Next?
GE invested in the wrong technology? All those factories they built in China will now have to be re-tooled – oops. No problems though, Obama will just write another check once he gets the credit limit increase.
Tip speeds are much lower with VAWT’s, so noise is less of an issue.
Wind turbines provide intermitent power so when they do operate to produce electricity to a grid they merely displace thermal power stations onto standby (with no reduction to fuel consumption and emissions) or onto part loading (with increased fuel consumption and emissions). The thermal power stations need to keep operating like that until the wind turbines stop operating.
In other words, wind tubines do not provide any useful electricity to a grid at any time.
Ten times nothing useful is nothing useful.
Richard
Hu McCulloch says:
July 16, 2011 at 2:57 pm
“DirkH — By “much better” with birds, do you mean they are better for the birds or do a better job of annihilating them? ”
I said “much better against”. Here in Lower Saxony, there’s an area full of wind turbines, or rather lots of them, for instance two huge concentrations around Kraftwerk Mehrum and near Salzgitter-Lebenstedt and then there’s also the beautiful Innerste valley south of Hildesheim. It’s wind turbine free as, being a narrow valley, not very windy. I saw the most beautiful birds of prey there; a red milan being the most spectacular. Birds i didn’t see near the wind turbine fields. Now, that might all be a coincidence but i’m driving a lot through these regions…
Having just returned from a trip though West Texas, I was appalled by the 5,000+ turbines on every flat spot northwest of Abilene.
They are an abomination and a blight upon our land.
I have never walked through a coal or nuclear power plant, to get an appreciation of our engineering prowess, and the scale of our power production facilities.
I think “the children” should be exposed to the infrastructure that keeps their electronics running, maybe then they will realize the folly of windmills.
There are some crazy numbers being thrown around, here, with no qualification. For example – the following represents delivered power on average, or power capability?
VAWT rated power = 0.0012MW
HAWT rated power – 2.5MW or 3MW
A 2MW turbine that limps along at 7% of capability is producing very little power per acre.
Then there is the density question. It is claimed that a certain acreage is required per generator, as a design goal. This is probably the talked about acreage requirement. Then there is the as-built acreage – what is actually happening in the world of wind farm construction.
Here at Mark Lynas’ blog I link some information regarding the as-built:
http://www.marklynas.org/2011/04/how-much-of-japans-land-area-would-be-needed-to-replace-nuclear-with-wind/
And which I’ll link here as well, as it is interesting to see the differences between what can be done and what is being done.
maybe in conjunction with this new idea wind power may be more usable – I put in tips/notes earlier but don’t know if it’s already been noted anyway – it seems semi appropriate to this thread I think..as it could hold a key to actually being able to use short term/irregular power sources?
http://www.monash.edu.au/news/show/graphite-water-the-future-of-energy-storage
DocWat says:
July 16, 2011 at 2:13 pm
“Don’t VAWTs have their own problems, besides being ugly?”
Yes, the more effective they are per square foot, as in not taking up much space, the less likely they are to be promoted. The two reasons for this that I see are why would government pay subsidies for highly effective and inconspicuous hardware? The second reason is why promote cheap technology that takes no place that bothers no one and that effectively lessen the need for “Big Energy” production?
In my country a singel VAWT for “home use” can generate more ‘an is need for ones need, which the horizontal versions do not, but connecting a VAWT to the grid is discourage through the cost of doing such an “evil” thing, which is supported by the greenies of course what with their seemingly need to tax people to death or what not.
This is a really good piece of work. It shows how we can produce energy just as inefficiently employing only 10% of the real estate previously required.
I hope that in the future wind turbines will bring great scrap prices!
Doug in Seattle,
I work for a Global Enterprise, and I do not like to see this sort of political malarky. Global Enterprises should make money by selling stuff people want, not what governments command.
One of the funniest things I ever saw occurred back in the “eggbeater” experimental days near Palm Springs, CA. DOE had sponsored (thus dooming the outcome from the beginning) construction of a very large vertical axis wind turbine. After innumerable fits and starts, they got the awful thing spinning; REALLY spinning (they must use an induction motor to get the beasts turning, even when the wind is blowing). Then a blade detached from the bottom hub and swung in a 360 degree arc about the axis, severing the support cables. The whole rig came crashing to the ground in a cloud of debris and dust as folks ran for their lives. It was a major “Aw S–t” moment I will never forget!
This counter-rotating efficiency ends when a few among them fail as they are wont to do.