Harvard research suggests real-world generating capacity of wind farms at large scales has been overestimated
Cambridge, Mass. – February 25, 2013 – “People have often thought there’s no upper bound for wind power—that it’s one of the most scalable power sources,” says Harvard applied physicist David Keith. After all, gusts and breezes don’t seem likely to “run out” on a global scale in the way oil wells might run dry.
Yet the latest research in mesoscale atmospheric modeling, published today in the journal Environmental Research Letters, suggests that the generating capacity of large-scale wind farms has been overestimated.
Each wind turbine creates behind it a “wind shadow” in which the air has been slowed down by drag on the turbine’s blades. The ideal wind farm strikes a balance, packing as many turbines onto the land as possible, while also spacing them enough to reduce the impact of these wind shadows. But as wind farms grow larger, they start to interact, and the regional-scale wind patterns matter more.
Keith’s research has shown that the generating capacity of very large wind power installations (larger than 100 square kilometers) may peak at between 0.5 and 1 watts per square meter. Previous estimates, which ignored the turbines’ slowing effect on the wind, had put that figure at between 2 and 7 watts per square meter.
In short, we may not have access to as much wind power as scientists thought.
An internationally renowned expert on climate science and technology policy, Keith holds appointments as Gordon McKay Professor of Applied Physics at the Harvard School of Engineering and Applied Sciences (SEAS) and as Professor of Public Policy at Harvard Kennedy School. Coauthor Amanda S. Adams was formerly a postdoctoral fellow with Keith and is now assistant professor of geography and Earth sciences at the University of North Carolina at Charlotte.
“One of the inherent challenges of wind energy is that as soon as you start to develop wind farms and harvest the resource, you change the resource, making it difficult to assess what’s really available,” says Adams.
But having a truly accurate estimate matters, of course, in the pursuit of carbon-neutral energy sources. Solar, wind, and hydro power, for example, could all play roles in fulfilling energy needs that are currently met by coal or oil.
“If wind power’s going to make a contribution to global energy requirements that’s serious, 10 or 20 percent or more, then it really has to contribute on the scale of terawatts in the next half-century or less,” says Keith.
If we were to cover the entire Earth with wind farms, he notes, “the system could potentially generate enormous amounts of power, well in excess of 100 terawatts, but at that point my guess, based on our climate modeling, is that the effect of that on global winds, and therefore on climate, would be severe—perhaps bigger than the impact of doubling CO2.”
“Our findings don’t mean that we shouldn’t pursue wind power—wind is much better for the environment than conventional coal—but these geophysical limits may be meaningful if we really want to scale wind power up to supply a third, let’s say, of our primary energy,” Keith adds.
And the climatic effect of turbine drag is not the only constraint; geography and economics matter too.
“It’s clear the theoretical upper limit to wind power is huge, if you don’t care about the impacts of covering the whole world with wind turbines,” says Keith. “What’s not clear—and this is a topic for future research—is what the practical limit to wind power would be if you consider all of the real-world constraints. You’d have to assume that wind turbines need to be located relatively close to where people actually live and where there’s a fairly constant wind supply, and that they have to deal with environmental constraints. You can’t just put them everywhere.”
“The real punch line,” he adds, “is that if you can’t get much more than half a watt out, and you accept that you can’t put them everywhere, then you may start to reach a limit that matters.”
In order to stabilize the Earth’s climate, Keith estimates, the world will need to identify sources for several tens of terawatts of carbon-free power within a human lifetime. In the meantime, policymakers must also decide how to allocate resources to develop new technologies to harness that energy.
In doing so, Keith says, “It’s worth asking about the scalability of each potential energy source—whether it can supply, say, 3 terawatts, which would be 10 percent of our global energy need, or whether it’s more like 0.3 terawatts and 1 percent.”
“Wind power is in a middle ground,” he says. “It is still one of the most scalable renewables, but our research suggests that we will need to pay attention to its limits and climatic impacts if we try to scale it beyond a few terawatts.”
The research was funded by the Natural Sciences and Engineering Research Council of Canada.
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A video abstract by David Keith is available for viewing and download here.
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If they ever managed to “stabilize” Earth’s climate (or ever claim to), it still – obviously – wouldn’t work. Then we’d get “Oh no! It’s worse than we thought!” – and we’d be back to square one, hyping up the panic because the climate would be seen as “out of control and it’s all our fault!”
This is all so incredibly pathetic.
@Steve and bessaman
>>”…perhaps bigger than the impact of doubling CO2.””
>but would it be a good, bad or indifferent effect on climate?
Well it would kill all of the birds that still fly, I suppose. Does that matter? Perhaps it would cause the evolution of birds that prefer to walk south for the winter.
Wind is a direct part of the planet’s natural heat redistribution system. One thing that has always boggled me is that the same people who are stressing over a few ppm of a beneficial trace gas are so cavalier about the possible repercussions of altering an actual direct part of climate and weather.
Wind farms extract energy from wind. They slow the overall wind speeds, and break up laminar flow of wind currents. They add turbulence. Unlike trees and other natural obstructions that slightly alter ground winds, these things are being built hundreds of feet high where they alter a part of the atmosphere that otherwise would never be interfered with.
The grand windmill experiment has been performed without any apparent consideration to this fact, and apparently no concept of the overall potential for climate alteration. Energy to spin the giant blades comes from energy that was already in use for another purpose. You don’t simply extract energy that is currently performing a function without considering how extracting that energy could potentially alter things. In my opinion the reckless proliferation of wind farms has more potential to have directly harmful “climate” results than any sort of CO2 release,
As kim says above, this is something I’ve been saying for years, but nobody seems to want to listen. I personally don’t see windmills as an icon of clean energy or stewardship or progress, I see them as icons of bad planning, reckless disregard for the environment (and birds), and a horrifying example of bad planning and poor understanding of nature.
As Richard Lindsay points out in the Telegraph article: “The world’s peatlands have four times the amount of carbon than all the world’s rainforests.” http://www.telegraph.co.uk/earth/energy/windpower/9889882/Wind-farms-will-create-more-carbon-dioxide-say-scientists.html
Storage is remains “sustainable” only as long as the peat remains wet and some of the observed effects of wind turbines are the drying effects of the wakes.
It is amusing to read that the potential benefits of wind turbines on crops include drying, warming and stimulating the release of CO2 and its uptake by crops.
http://www.ameslab.gov/news/news-releases/wind-turbines
Any signs of a grassroots movement to save the peat bogs?
The Denver area has poor air quality at times, and as nearly as I can tell by eye-ball measurements, the pollution often drifts north along the front range until it reaches north of Ft. Collins. Here it is swept east by the persistent winds. However, the development of lots of wind energy in southern Wyoming and Northern Colorado may slow this persistent flow. Perhaps, then, air quality in the most populous part of Colorado will interact badly with wind energy?
When we were working at the wind park in Tehachapi we were told that the older turbine field on the Mojave side saw its power output cut by 10% when the new turbine fields up on the top of the ridge were installed.
If you add this to the fact that turbines only produce 30% of their rating……………….
Brooker has an article, “One Day Turning Off The Lights Won’t Be Up To You,” speaking of the folly of shutting down coal powered plants in favor of wind. However in the comments one sees those who are still sure the folly isn’t a folly.
http://www.telegraph.co.uk/earth/energy/9889184/One-day-turning-off-the-lights-wont-be-up-to-you.html
Josh seems to think it is a folly, judging from his cartoon, shown at Bishop Hill
http://www.bishop-hill.net/blog/2013/2/24/energy-just-like-old-times-josh-205.html
CodeTech says:
February 25, 2013 at 1:35 pm
” I personally don’t see windmills as an icon of clean energy or stewardship or progress, I see them as icons of bad planning, reckless disregard for the environment (and birds), and a horrifying example of bad planning and poor understanding of nature.”
Steampunk contraptions.
http://commons.wikimedia.org/wiki/File:Robur_1.jpg
Look,all of these facts about how wind generation is not a
good way to go was known from the start.But what was also
known…. it is a good way to make a fast buck without the least
chance of losing. A sure thing.Win,win.
Alfred
Wind farms are really gas turbine engines. The sun heats the surface (maybe out over the ocean) which causes the air to expand and speed up and it gets ducted into the intake (valley) of the engine to where the fan blades are, ready to get turned, and then exhausted (no doubt colder and slower) into the exhaust duct (next valley). Imagine how huge that engine is !
I wonder what the Temperature drop is for the expanding working fluid (air) as it passes from the front of the turbine wheel, to the rear.
Anyone want to take a wild guess, what the Carnot efficiency of this monster heat engine might be.
Yes clean green renewable solar energy is free, it is just the gathering it up part, and collecting, that you have to pay through the nose for.
And if the wind drops to half your design velocity, well you only lose 87 1/2 % of your generating capacity.
It’s a really well buffered energy source, ideal for delivering a constant stream of cheap energy through thick and thin of weather vacillations.
Farmers learned eons ago how to properly utilise free clean green renewable solar wind energy.
When the wind blows, the multibladed self steering windmill turns, and each rotation, it makes a single pump stroke, and sucks a gallon of water up out of the ground into the horse trough.
So when the wind blows; day or night, the horse trough get filled maybe till it overflows, and if the wind doesn’t blow, well the horses just have to suck it in, and wait till the wind blows again.
It’s a one size fits all, system that works largely untouched by human hand.
Well unfortunately, electric cars; even Teslas, are not horses; and they just can’t suck it in and wait for the wind to blow.
Hey Mr Tesla, they made wind powered ships a long time before they made electric powered ships.
Anyone want to invest in a green sailing car startup; only $150,000 (subsidized) per S model vehicle (S is for sail powered)
“In order to stabilize the Earth’s climate, Keith estimates, the world will need to identify sources for several tens of terawatts of carbon-free power within a human lifetime. In the meantime, policymakers must also decide how to allocate resources to develop new technologies to harness that energy.”
Energy from space environment. So so panel with 20 percent efficency gets 1363 watts of sunlight
so 272 watts of electricity per square meter constantly. Square km is million square meters and a 1000 km square is trillion square meters. No shortage area in areas near Earth can used which has zero effect upon how much energy reaching Earth, and could be far enough away that one could see them [zero impact]. Though one might want them visible and you might want them shading earth- which could also be an option. I think earth having a saturn like ring would nice.
But point is one can have them with zero impact- no one could see without using a telescope and
basical people could unaware of them- unless the putting some effort to find them.
Obviously there would a need for infrastructure on earth to recieve beamed energy- there many possible ways this could be done. One could have something like a space elevator conducting electricity- so big massive and one worry about numerous “environment impacts”. But could have
energy recieve individually and small communities- so sort of like the scale of cell phone towers and individual cell phone type infrastructure.
Point is doable in various ways. And it could be much less impact than solar or wind farms on the Earth surface. And far more economical.
But we are not ready to do this yet, it has to be something which can done within a lifetime, rather than in less than 10 years from now. So within 50 years, if we go in right direction. And longer we don’t move in right direction, then it’s always going to be 50 years into the future.
If we move in right direction 30 years ago, we would be within 20 years of it today. And could done this but we had different priorities.
So what we need first, is a market of electrical power which in the space environment. A electrical market for the space environment. And market forces and competition the price of electricty in orbit can be reduced significantly.
To get a electrical market in space for space, we should probalby start by beginning a market for
rocket fuel in space for space use.
To start a rocket fuel market in space, we need to develop rocket fuel depots in space.
So start with rocket fuel being delivered from Earth to space. Have this rocket fuel in space available for sale to any party needing rocket fuel. So available to NASA and other national space agencies, and available to private satellite industry. So start with NASA as customer, and develop more customers.
If there fuel depots in space, the cost of NASA going to Moon or Mars would reduced significantly- like around 1/2 or less the total cost of a program.
Once one has fuel depots in space selling rocket fuel to anyone who wants to buy rocket fuel,
there will be an effort to lower the cost to deliver the rocket fuel to space- this will involve many different kinds of efforts. But one direction which could make sense [is dependent on how much demand there could be for rocket fuel per year] is to mine water in space and convert the water into rocket fuel [Liquid Hydrogen and liquid Oxygen].
To do this requires electrical power. So makers of rocket fuel will be a customer for electrical power. And a modest amount of rocket fuel- say 1000 tonnes per year, would require a lot of electrical power. And having that much electrical power available, allows other customers who need electricity in space for other uses to buy this available electrical energy.
Rocket fuel is also a battery- a way to store electrical power. So if there is a need for huge amounts of electrical power for brief periods of time, an electrical provider making rocket fuel
has the capability of delivering a huge amount of power. Can stop making rocket fuel, use power instead to sell power to another customer, and if customer needs even more power, can use the chemical energy of hydrogen and oxygen to generate even more power.
So making rocket fuel is also electrical energy storage- and the more electrical energy generated results in more available rocket fuel in a shorter time period.
So fuel depots lead to cheaper way of getting anywhere in space, and lead to many different kinds of markets. Such as rocket which act as tugs moving things around in space- rescuing broken satellites, scraping broken satellite. With rocket fuel available space tugs can be reused, so a tug which costs 100 million to make on Earth and launched into space, can do many different things for cost of buying rocket. You can not have taxi or tow truck service if there is no fuel available for these vehicles.
Having a fuel depot on the lunar surface, more than halves the cost to get to the moon and back- 2/3rd of payload of Apollo moon program was getting the rocket fuel to surface, so the crew could leave the Moon. If you already have rocket on the Moon, you don’t need the largest rocket ever made to get you to the Moon [and back]. So with fuel depots, and getting lunar water mining and lunar electrical power market. And one can export lunar rocket fuel to
lunar orbit [another business]. Also one might ship lunar rocket fuel to Mars orbit- low earth orbit may be cheaper to still deliver rocket from Earth. Though new ways to deliver rocket from
earth surface may develop- such as using a large special type cannon. Such as here:
http://en.wikipedia.org/wiki/Quicklaunch
Or one simply can lower costs by specializing “normal rockets” to deliver such payloads.
Point is this doesn’t cost the public anything- it lowers NASA’s cost and enables NASA to
explore space more effective. If you don’t NASA exploring space, one could consider it a
cost- because NASA might do more exploration- it might explore the Moon and Mars in a shorter period of time. Oppose to never getting around to it, as NASA has doing for last 30 years.
Anyways, after you get commercial mining of lunar water and NASA is exploring Mars, it could then take couple decades before we ready to build space systems cheap enough to deliver electrical power to Earthlings.
Windmills take energy out of the system. Sometimes I wonder if enough windmills get built if some of that energy may come from the speed of the Earth’s rotation and increase the LOD. Probably not a good thing.
In the longer term, (2050 and beyond) when we’re talking about multi-terawatts of power and considering the likely evolution of technology, extra-planetary broadcast solar power might seem to be a better bet than wind power.
At least until I finish that cold-fusion reactor in my basement….
– MJM
If the earth’s geography, rotation and atmosphere creates wind, would an earth full of wind turbines slow down wind velocity due to increased drag? And would that increased drag cause the earth’s rotation to slow infintesimally? If the earth’s rotation slowed, would that affect the earth more than a little more carbon dioxide? LMAO!
EW3 says:
February 25, 2013 at 1:17 pm
The production credits go to those who build and operate the wind turbines, not the manufacturer. IIRC there is also a construction subsidy that goes to the owner, not the manufacturers. So how is it that GE, a manufacturer, gets a tax benefit?
The income statement for GE lists income taxes for the year ending 2011 as over $5 billion, and some previous years as negative and some positive. Having looked at GE’s SEC filings, GE’s taxes as listed on the income statement is actually an allowance for taxes due from it’s divisions. As the taxes of the various units of the corporation are determined, and tax disputes with the IRS are resolved, that tax allowance is adjusted up or down as the case may be. Since one certain year may include resolutions of adjustments from 3 or more years prior, determining the tax payments of GE for any one year is likely not possible for an outsider, and determining the actual tax payments by GE requires a multi-year analysis.
So exactly what is your source for the assertion that GE had a tax bill of $0 ? and exactly what subsidy program directly offsets GE’s taxes?
Also, Natural Gas fired back-up for when the wind does not blow.
Wind farms do not seem to be cost effective.
Any racing yachtsman can tell you the effect of an upwind yacht’s wind shadow on performance of the downward craft.
Something bothering me, might be just ignorance but the windmills take energy out of the wind … the more windmill, the more energy is stripped out … what happens at the other end of the spectrum where that energy was originally destined for ?
Sorry, but “wind is better than coal” not only is no good reason for wind, but in fact, wind
power has far less economic value than electricity produced by any conventional means, including coal. Uncontrollable power simply has little value and obviously cannot replace controllable power,
yet requires controllable backup, which means paying twice for every kilowatt hour of wind you buy
once to the wind provider, and again to the conventional power operator for providing backup,
generating capacity., even during those times when it is not producing anything. The side effect costs of uncontrollable power generation is always given short shrift, if mentioned at all. No matter how much uncontrollable power generation capacity is added to a grid, not one single controllable, conventional power generator can be eliminated.
Any off world solutions ignore the fact we are at the bottom of a very deep gravity well that takes enormous amounts of energy(that we don’t have) to escape.The so called “space station”is so low in orbit it requires 20,000 lbs of fuel a year just to maintain orbit.
Also little details like space being completely deadly to life,etc.
So much easier to build stuff at ground level but I guess that’s not sexy .
Our tech ain’t good enough it’s sad to say,mainly coal powered actually.Get used to this planet.
Efficiency: 21% of faceplate, Netherlands, Germany, England, Scotland. Life 12-15 years, not 20-25 years (Bishop Hill, today). Probable cost reduction with time: <20% (optimistic?).
No wonder the British Government is buying up windfarms now: they have to get the private owners out before they declare bankruptcy, fail to repair or replace the turbines, and claim (loudly) that they got in because of the subsidies, not because windpower was inherently cost-effective and DARNIT, keep those subsidies going! (last especially relevant for those on Peer-owned lands).
Well, David Keith, eh.
This David Keith?
http://www.keith.seas.harvard.edu/AirCapture.html
Only a matter of time before some wind energy supporters discover the connection.
As we all know, in the World of climate science/politics, anyone against my vested interest is obviously trying to benefit their vested interest.
“Each wind turbine creates behind it a “wind shadow” in which the air has been slowed down by drag on the turbine’s blades.”
S’truth!! I didn’t realize the level of understanding by windy engineers was so low! I knew wind energy was a joke but I took for granted that the buffs at least knew that too crowded a wind farm would reduce the efficiency of the downwind turbines. How did it take so long to “discover” this – it even took a Harvard man to realize it. As I mentioned in earlier post, the education system is going to have to asterisk many of the PhDs of this generation. No longer do I take as an authority that the underlying “physics” of things is sound.
Chris4692 says:
February 25, 2013 at 3:11 pm
And I suppose in your world, the auto makers didn’t benefit from the “Cash for Clunkers” program, insulation and window manufacturers didn’t benefit from Energy credits, and farmers don’t benefit from ethanol/fuel mandates.
http://www.nytimes.com/2011/03/25/business/economy/25tax.html?pagewanted=all&_r=0
General Electric’s most recent tax filing was for a credit of about $3 Billion on reported profits of about $14 Billion, if one can believe the article. It also implies GE does benefit from “green credits” on its wind turbine sales.