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But there are limits that could hold wind back from growing

A new study from Harvard University's School of Engineering and Applied Sciences says that the generating capacity of large-scale wind farms isn't quite as high as scientists previously thought.

The study was led by Harvard applied physicist David Keith, who showed that we may not have access to as much wind power as once thought. Keith is an internationally renowned expert on climate science.

According to Keith's study, individual wind turbines each create a "wind shadow," which is where air is slowed by the drag on the turbine's blades. Wind farms with as many turbines packed into an area as possible but with just the right amount of spacing in between them are optimal for decreasing this drag.

However, the larger these wind farms are, the more they communicate and regional-scale wind patterns are even more important. Keith said previous generating capacity of large-scale wind farms ignored the drags and these wind patterns.

Keith's study said that the generating capacity of large-scale wind farms that are larger than 100 square kilometers could peak anywhere from 0.5 and 1 watts per square meter. Prior estimates put these figures at 2 to 7 watts per square meter.

“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,” said Keith.

But there are limits that could hold wind back from growing. Keith said that if wind were to exceed 100 terawatts, it would have a huge impact on global winds and eventually climate -- which could negatively affect climate more than 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,” said Keith. 

“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. 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.”

Keith concluded that we'll need to find sources for tens of terawatts of carbon-free power "within a human lifetime" in order to stabilize the Earth's climate.

“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," said Keith.

Source: Harvard University

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By Mint on 2/27/2013 11:08:17 AM , Rating: 3
You know what? I'm actually glad, because I'd love to debate the value of wind power with an industry spokesperson.

Regardless of who is correct, the inescapable fact is that America's developable wind energy resources are many times greater than our country's energy needs.
Inescapable fact? So what do you do about filling in the gaps when wind isn't blowing? Don't give me the "interconnected farms" line, because wind is highly correlated across vast geographic regions. Take a look at Europe's total wind output spanning thousands of miles:
Even if they had a perfect grid, they'd still have minimums of <5% capacity factor.

So what's the answer, energy storage? Unless there are fortuitous geographical features for hydro storage like New Zealand, it's too costly. Nothing else can store/release electricity for even double the generation cost. If it could, we wouldn't have peaker plants and so much higher daytime market rates. Nothing is even close to the 1-2c/kWh needed to ignore the variability of wind.

In reality, we use natural gas to fill in the variability of wind, but the problem is that CCGT plants don't run as efficiently ramping up and down instead of just minimizing variation. Even if you believe that combating AGW is worthwhile, this inefficiency means 1kWh of wind doesn't entirely displace the natural gas used by 1kWh of CCGT generation.

That's the problem: You can build 1GW of wind, but variability means you need 1GW of natural gas as well to back it up, and that plant will charge higher rates for not only running inefficiently, but also running at lower capacity factor when it's not needed due to wind generation. Its only savings are fuel cost, or maybe 2-3c/kWh. If wind can't produce power that cheap, then it raises the system-wide cost of generation. Is there any hope of hitting that cost floor? I sincerely doubt it.

I await your reply, Michael Goggin...

By FITCamaro on 2/27/2013 11:26:56 AM , Rating: 2
Logic is not appreciated by those seeking government funds.

By Mint on 2/27/2013 11:53:21 AM , Rating: 2
People will try to deceive whether chasing gov't funds, bank funds, or venture capitalist funds. There's no distinction to be made on the basis of seeking gov't funds, and I don't have a blanket policy against using them to boost promising technology in the early going, especially when there's so much competition around the world.

The problem is that wind and solar simply aren't that promising due to very fundamental issues, and for wind we're way past the early going anyway.

By FITCamaro on 2/28/2013 7:51:58 AM , Rating: 2
I do. It's not their job nor within their authority.

"If you look at the last five years, if you look at what major innovations have occurred in computing technology, every single one of them came from AMD. Not a single innovation came from Intel." -- AMD CEO Hector Ruiz in 2007

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