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Rethinking wind power Harvard study shows it to be overestimated
Watts Up With That? ^ | February 26, 2013 | by Anthony Watts

Posted on 02/27/2013 12:57:42 PM PST by Ernest_at_the_Beach

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.

###

A video abstract by David Keith is available for viewing and download here.



TOPICS: Conspiracy; Science; Weather
KEYWORDS: climatechange; fartshavemoreenergy; globalwarming; globalwarminghoax; greenenergy

1 posted on 02/27/2013 12:57:48 PM PST by Ernest_at_the_Beach
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To: SunkenCiv; Marine_Uncle; Fred Nerks; Carry_Okie; blam; Lorianne; Twotone; bigbob; NormsRevenge; ...
Video available,...and very good,...a REAL ENGINEERING LEVEL STUDY

Environmental Research Letters--Are global wind power resource estimates overstated? >/b>

Yes ,...Yes...

2 posted on 02/27/2013 1:09:37 PM PST by Ernest_at_the_Beach ((The Global Warming Hoax was a Criminal Act....where is Al Gore?))
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To: Ernest_at_the_Beach

There is also the fact that building LOTS of turbines causes them to interfere with one another, decreasing the value of the wind farm.


3 posted on 02/27/2013 1:11:01 PM PST by tbw2
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To: Ernest_at_the_Beach

Any farmer with a wind vane could have told them this.


4 posted on 02/27/2013 1:31:22 PM PST by Venturer
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To: Ernest_at_the_Beach

When will the sheeple wake up and realize that the Pied Pipers of Liberal/Progressive/Socialist/Marxist causes have already led us down the wrong alarmist paths many, many times before??


5 posted on 02/27/2013 1:33:24 PM PST by RatRipper (Self-centeredness, greed, envy, deceit and lawless corruption has killed this once great nation.)
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To: Ernest_at_the_Beach

Be careful when libs appear to agree with you.


6 posted on 02/27/2013 1:47:16 PM PST by freekitty (Give me back my conservative vote; then find me a real conservative to vote for)
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To: Ernest_at_the_Beach

Meanwhile, incident solar energy is something like 985 w/m^2. Of course that can’t all be extracted (solar cells are around 15% efficient, and the sun doesn’t always shine), but you’re starting with 1000 times the power density when the sun shines, so the average has to be higher than 0.5 to 1 watt/m^2 given here.

I realize that the number given is an average, but I’m surprised at how low it is compared to solar.


7 posted on 02/27/2013 2:08:04 PM PST by Pearls Before Swine
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