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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 johnsmith9875 on 3/4/2013 1:47:32 AM , Rating: 2
True, solar power is unreliable, the sun only comes out every day.


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