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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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RE: Yet another reason to switch to nuclear
By mjv.theory on 2/27/2013 11:36:36 AM , Rating: 3
My point is, if we rely much more heavily on Nuclear power, we may reduce CO2 emission, but there will be a trade off. There will certainly be an increase in by-products and risk, regardless of the number of safety measures in place, human error is always possible.

The presently prevalent nuclear technology that is based on solid fuel and pressurised water reactors in vunerable to accident and produces meaningful amounts of "waste". Nuclear power based on molten salt reactor technology is orders of magnitude safer, cleaner, more efficient and more easily expanded to replace coal and oil. Large scale wind generation is a bad joke, solar is geographically and time of day limited and the only realistic way to develop a hydrogen economy would be to have a significant increase in nuclear power stations to extract said hydrogen, at which point the hydrogen is unnecessary. MSRs using thorium and/or uranium are cleaner, easier, more scalable and cheaper than oil, coal, natural gas, fusion, wind, wave, tidal and solar.

By chromal on 2/28/2013 12:42:11 AM , Rating: 2
There are a lot of practical problems that have yet to be solved in a production scale molten salt reactor nuclear power plant. Turns out, molten salts are extremely corrosive to metals, moreso when hot. I'm not saying they shouldn't be pursued, developed, and perfected, but they aren't there, yet.

I do agree that the uranium fuel cycle in the US is a problem, if only because it isn't being centrally stored in isolation somewhere.

By johnsmith9875 on 3/4/2013 1:42:54 AM , Rating: 2
Molten sodium has its own problems. One reactor accident occurred when the sodium began depositing gunk on the fuel rods, clogging the cooling channels and eventually the reactor overheated and had to be shut down permanently due to all the damage.

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