CU-Boulder leading study of wind turbine wakes
A turbine at the National Wind Technology Center south of Boulder, Colo. (photo courtesy of CIRES) |
While wind turbines primarily are a source of renewable energy, they also produce wakes of invisible ripples that can affect the atmosphere and influence wind turbines downstream — an issue being researched in a newly launched study led by the University of Colorado Boulder’s Julie Lundquist, assistant professor in the atmospheric and oceanic sciences department.
The study, called the Turbine Wake and Inflow Characterization Study, or TWICS, also includes researchers from the National Oceanic and Atmospheric Administration, the U.S. Department of Energy’s National Renewable Energy Laboratory, or NREL, and the Lawrence Livermore National Laboratory in Livermore, Calif.
Scientists and wind energy developers will use results of the study to better understand power production and increase the productivity of wind farms, according to the researchers.
“Today’s massive wind turbines stretch into a complicated part of the atmosphere,” said Lundquist, who also is a joint appointee at NREL. “If we can understand how gusts and rapid changes in wind direction affect turbine operations and how turbine wakes behave, we can improve design standards, increase efficiency and reduce the cost of energy.”
To measure wind shifts and wake behavior, the researchers will monitor a wind turbine at NREL’s National Wind Technology Center in south Boulder, using an instrument developed at NOAA called a high-resolution scanning Doppler lidar. The lidar produces three-dimensional portraits of atmospheric activity and can capture a wedge of air up to 3,280 feet from the ground and 4.3 miles long.
Robert Banta, an atmospheric scientist with NOAA’s Earth System Research Laboratory and a TWICS researcher, has worked with the instrument for several years.
“The wake effect has been modeled in wind tunnel studies and numerical models,” said Banta, “but the atmosphere is different, it’s more variable and complicated.”
Researchers also will use a specialized laser called a Windcube lidar and a sonic detection and ranging system, called a Triton sodar, to measure wind and turbulence. In addition, NREL has installed two meteorological towers, each 135 meters tall, which will be used to measure air temperature, as well as wind and turbulence.
“Even fluctuations in air temperature throughout the day can affect wind turbine wakes,” said Lundquist. “The resulting changes in wake behavior can impact the productivity of wind farms with many rows of turbines, so it’s important to observe them in detail and understand how to minimize their impacts.”
Other TWICS researchers include Yelena Pichugina, Alan Brewer, Dave Brown, Raul Alvarez and Scott Sandberg of NOAA, Neil Kelley and Andrew Clifton of NREL and Jeff Mirocha of Lawrence Livermore National Laboratory.
CU-Boulder graduate students Matt Aitken, Mike Rhodes, Robert Marshall and Brian Vanderwende of Lundquist’s research group also will work on the study.
For more information on the TWICS study and Lundquist’s research visit atoc.colorado.edu/~jlundqui/re.html.
Can’t be true; wind turbines only take up about 1/4 of an acre. That’s still a very low power density. I have a compact electric power source that puts out 1.5 MegaWatts per square metre; simply fabulous, and I have several of them in my house. Actually have a bunch of them right at my feet under my desk.
They are about 4 x 4 cm (0.0016 m^2) and I can get 20 Amps at around 120 Volts out of one. So why would I be interested in wasting a full quarter acre on a wind turbine.
And now I find out that you actually need more like four miles behind them and a km high.
How many times have I said on WUWT that a wind turbine is actually a gas turbine engine, with the heat energy being provided by the sun, miles away from the final turbine impeller; and that you need a vast air duct in front of the turbine to bring the working fluid (air) into the turbine fan, and another big exhaust duct to direct the exhaust working fluid out the back. It takes thousands of acres to run a one MegaWatt solar powered atmospheric turbine engine.
I’ll stick with my compact electric power sources. Somebody claimed that there is some big monster auxilliary component up in the hills somewhere that is wired to my electric power sources; but I’ve never seen it, so what do I care.
But that solar powered air operated gas turbine generator, is supposed to run for free they say, and doesn’t put out much CO2. They do go ape sometimes; and simply cut themselves down with the propellor run amok.
The charter of the NREL is to develop better wind turbines. The bulk of the funds being spent in 2010 were related to the wind turbines.
One issue against wind farms is they use a lot of land, 22 acres per turbine. Projecting the growth of wind farms in the west to deliver 20% of the electrical energy on the grid, with 2 MW turbines, the estimated square miles of wind turbines is prodigious, hundreds of square miles covered with towers. However, if the turbines were 10 times larger and could be packed in closer so the wake of one turbine does not drastically affect its neighbor, the impact on the demand for space could be reduced. This research could shed light on how high density the packing of wind turbines can be. However, another thrust of NREL is to develop bigger and better turbines mainly for off land use. I can just imagine the 100GW tower and the impact on the aesthetics of western natural beauty. It would have to be put in the bottom of the Grand Canyon to keep airplanes from colliding with it.
While this research will provide employment, the wind power development community is grasping to hold on to the research support. The problem for NREL is that they are working on the wrong side of the effort to implement wind farms as a source of electrical power. The current technology is not practical because the wind is unpredictable and variable. Consequently, the wind turbines as a source of electricity are also unpredictable and variable. Size doesn’t really matter. Wind technology unlike the grid which has a daily expectation of demand and tries to anticipate peak demand cannot be depended upon to be available at any time let alone at peak demand. The wind farms must have some way to store energy to be practical and most do not have that option available.
“”””” Mark Gibbas says:
April 27, 2011 at 6:15 am
……………………..
Beyond that, I think it is a great idea to study the dynamics of wind power as this should help advance the efficiency. And our planet needs every safe source of power production we can develop, and thus wind energy is extremely needed, along with solar, tidal, hydro, and whatever else we can dream up………………”””””
So are you suggesting that “wind” power is NOT “solar” power. So where is all that free wind energy coming from ?
Why don’t you calculate the Carnot Efficiency of a typical wind power turbine/generator system; and then tell us how you are going to raise that efficiency.
So how come T. Boone Pickens decided to not invest his inestimable Texas wealth in that free energy from wind? Uually, very wealthy people know a good deal when they see one and jump on it to increase theri wealth. Don’t seem to be many wealthy people in the (free) wind power business.
So should the Government; as in we the people, charge these investors for their use of our free wind energy supply; or are we just going to let them build their fans anywhere they want to, and then actually charge us fo the free energy they get.
Considering the proverbial results of the flapping of a butterfly’s wing on the weather, perhaps we should just be grateful that the effects of the number of these monstrosities already out there have not already triggered climatic apocalypse.
There is a much better “iconic image” to go with this post: http://ict-aeolus.eu/images/horns_rev.jpg
It goes with the caption, “Beatiful Photo Shows Wake Effect of Wind Turbines” from this article from Treehugger: http://www.treehugger.com/files/2010/01/offshore-wind-farm-photo-wake-effect.php (Embedded link in article is broken)
Makes a nice comparison with the stock water vapour from “smokestacks” image that accompanies all the “carbon polluter” stories.
The discussion following is interesting for the apparent belief expressed by some that surface level “weather” is not affected by surface level conditions, only upper level. My understanding is the extended wake turbulence produces drying effects for thousands of metres on land with variable consequences for agriculture.
The effects on non-vegetable living downstream environment are also far greater than we hear. The perpetual bird and bat kills are also not the quick surgical slices or pressure wave organ explosions occasionally mentioned. Many die slow agonizing deaths as this paper from the University of Calgary makes clear: http://ucalgary.academia.edu/erinbaerwald/Papers/182008/Incidence_and_Management_of_Live_and_Injured_Bats_at_Wind_Energy_Facilities
More Green Jobs here, obviously.
George Smith @ur momisugly 8:44 am
The numbers I’ve seen are actually 80 acres for a 1.5 MW turbine to prevent turbulent interference between generators. It works out to 4 W/m^2, a very low generating capacity.
Duh.
Since the Wright brothers (using the wind tunnel they invented) invented a VERY efficient propeller and they and others developed airfoil wing shapes, the airfoil shape has been recognized (and used) to make efficient use of propellers and fan blades. Centrifugal airfoil industrial fan blades are even up to 91% efficient (Chicago Blower’s, specifically).
It is obvious that wind turbines use the airfoil shape to get what efficiencies they do.
But one thing about airfoils is this: The flow MUST be laminar over both the wind side and the lee side of the blade/wing. ANY disturbance of the laminar flow rapidly diminishes the airfoil’s ability to work efficiently – or in some cases, to work at all (as in when a plane stalls at low speed or is caught in wind shear).
So, though I hadn’t thought about this in this specific regard, the point is obvious. (I DID think of it in terms of ocean current farms, which I think is the greatest untapped energy source on the planet. I don’t have the know-how to figure how close, but ocean turbines, even at only 2-3 knots, can be utilized in repetitive banks (and at different depths, too). I understand ocean currents to be more consistent and aligned than winds, which vary in intensity and direction from moment to moment. Because of this more homogeneous flow, I believe they can be placed fairly close to each other.
With current velocities of only 2-3 knots, much more force (and thus energy) is available than the 12-knot wind turbines are designed for. I’ve read that flowing water at a given speed has 200 times the applied force of wind. So 2-3 knots may not sound like much, but it still affords more force – and it is force>/i> (aided by efficiencies, of course) that delivers wattage. Plus, fish are not in danger, as fish can simply swim around the blades. And there won’t be any ocean turbines self-destructing, either. – or shutting off because the fluid velocity is too high. They would not be restricted as to depth like wind turbines are with height.
Banks can be several turbines across, and several deep can be set every few hundred feet, all along the Gulf Stream or any other consistent ocean current. The same technology that currently exists to convey the electrical power to land from wind farms can be utilized for ocean currents.
Compared to the spacy schemes “green” folks have come up with to create clouds and such, developing this technology would a no-brainer.
And laminar flow over the airfoil/turbine blades is more guaranteed.
philincalifornia says:
April 26, 2011 at 8:40 pm
R. Shearer says:
April 26, 2011 at 7:43 pm
When you live in paradise (i.e., the Boulder area) you don’t owe nobody no explanations! 😉
Mark Gibbas says:
April 27, 2011 at 6:15 am
“Since wind is a free and immediately usable resource, there are no ‘supply costs’ in running a wind farm. Comparatively, fuel based power generation (gas, coal, nuclear) have substantial and continuous fuel costs that over the life time of the plant dwarf the costs of ‘free’ power such as wind.”
Bunkum. You failed to mention the need to build a power generation supply equal to whatever the wind is as a backup in case of no wind. And those back up must be kept running so there is no loss of electricity if switch over is needed. So you pay twice.
Brian H says:
April 26, 2011 at 5:48 pm
Will they also count the bird and bat bodies that pile up in the “wake”?
No, no – bird migrations into wind farms is a good thing, and this experiment will prove it. They’ll see one big echo from an eagle flying into a turbine blade. Then they’ll see two smaller echos emerging from the far side.
Those must be baby birds – right?
“”””” Paul Linsay says:
April 27, 2011 at 10:53 am
George Smith @ur momisugly 8:44 am
The numbers I’ve seen are actually 80 acres for a 1.5 MW turbine to prevent turbulent interference between generators. It works out to 4 W/m^2, a very low generating capacity. “”””””
Well that’s sor of the “how close can you mount twin outboard motors on your boat and have them not interfere with each other. ?” question. What I was referring to was how much clear space do you need in front of the turbine to get clean non-turbulent air coming into the turbine, plaus how much more do you need behind the turbine, so it doesn’t generate a lot of back pressure. That’s a lot more than 80 acres.
The California Altamont Pass wind farm, needs the whole of San Francisco Bay in front of it to duct air into those turbines, and the whole California Central Valley to exhaust the disturbed air behind them.
Try to get a permit to install a smaller wind turbine on the roof of your house.
It’s worse than you think. Ramping up and down to match wind is very hard on large conventional plant, and cuts service lifespan considerably, not to mention greatly increasing costs. Much of the time is spent in lower-efficiency mode during the transitions. Plus they must be kept “warm”, on stand-by, even when not generating power.
Not just bollocks, a total bollox.
Mark Gibbas says:
April 27, 2011 at 6:15 am
“Lastly, do NOT believe the hype from people who claim that wind is not cost effective. It is very much cost effective, because once you build the wind farm, the cost to operate it is very low in that you don’t not have to “dig up wind” in order to run the turbines. Since wind is a free and immediately usable resource, there are no ‘supply costs’ in running a wind farm. Comparatively, fuel based power generation (gas, coal, nuclear) have substantial and continuous fuel costs that over the life time of the plant dwarf the costs of ‘free’ power such as wind.”
Where in the world do you get stuff like this? According to the U.S. wind operators own reports of O&M costs, the O&M cost per Kwh for wind is probably the highest of any technology in the electric power industry. Those blade feathering mechanisms and transmissions are eating their lunch. The capital and fuel costs over a 15 year project life for Combined Cycle Gas Turbines at current natural gas prices is around 4 cents per average Kwh (at the fence). Capital cost alone for a wind turbine over that same 15 year life is over twice that amount and the European data indicates that the price for on-shore wind, including O&M, is 12 cents (U.S.) per average Kwh. European off-shore wind is running 20 cents per Kwh. The average at the U.S trading hubs is under 4.5 cent per Kwh using our current mix of generation. The more solar and wind we add to that mix, the higher the price will go. Unlike the U.S., where the true cost of wind is obscured by backdoor subsidies (investment tax credits; accelerated depreciation; depletion allowances; direct subsidies), to their credit the Europeans are paying the true cost for wind and solar at the fence in the form of hyper-inflated tariffs and the numbers could not be clearer. Economics is NOT a valid argument for either wind or solar, but solar is much much worse in that regard.
Mark Gibbas says:
April 27, 2011 at 6:15 am
“Lastly, do NOT believe the hype from people who claim that wind is not cost effective. It is very much cost effective, because once you build the wind farm, the cost to operate it is very low in that you don’t not have to “dig up wind” in order to run the turbines. Since wind is a free and immediately usable resource, there are no ‘supply costs’ in running a wind farm. Comparatively, fuel based power generation (gas, coal, nuclear) have substantial and continuous fuel costs that over the life time of the plant dwarf the costs of ‘free’ power such as wind.”
Let us continue ….
EVERY power plant of EVERY type is built only after long-term cost-benefit analysis incorporates ALL of those factors from initial design through permitting through fuel through training and paying operators through maintenance, repair, demolition, and site restoration.
The future cost of money, future taxes, future pay raises for future operators, future maintenance, etc … are all factored in. Current fuel cots, expected future fuel costs, etc are included.
And windmills do NOT add up to anything except a loss – UNLESS (big “unless” there!) – you add in government tax-money subsidies. Without constant government money from the rest of the taxpayers to the green lobby, no windmill makes money.
—
Wind turbines- on average worldwide – only deliver 21% – 23% of their RATED output. So, to get the “nameplate” rating of ONE windmill, you need to build 5 windmills.
Worse, winds are notoriously random – but the local winds in one area are going to be essentially identical for that region (winds in any 100 km x 100 km square are going to be the same since weather does not vary), so to get even your 5 windmills running even part of the time, you must build them spread out over several tens of thousands of square kilometers, repeating your 5 windmills every 60 km.
So now you must build not 1 windmill, not 5 windmills and a local distribution center and transformer grid, but 10 groups of 5 windmills and 10 distribution centers.
All of this to get the (unreliable) nameplate power of one windmill – part of the time.
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Classically, I understood the thumb rule for the second windmill was 10 blade diameters between following windmills, and 5 blade diameters between adjacent windmills. So that now needs to be “miles” of distance between rows.
More – MUCH MORE – wasted copper and wasted energy and wasted concrete and wasted money building the high voltage wires to connect all of the windmills together. (Most nowadays are in a single line across the absolute edge of a hill or steep slope above a long valley – what Smith above described as the “natural” turbine input duct. This further limits available sites.)
So – Even ocean based windmills now need to be separated by more space. Money. Money. Money. For nothing – 96 percent of the time.