The argument over the limits of wind power is heating up.
The crux of the dispute is what happens to the ability of turbines to produce energy when they are deployed on a massive scale. Last fall, there was the report that 4 million turbines could supply half the world’s energy by 2030 and even at that level, performance wouldn’t suffer.
But David Keith of Harvard and Amanda Adams of North Carolina-Charlotte, in their new paper in the journal Environmental Research Letters, say that such estimates vastly underplay the degree to which putting up more and more turbines would slow the wind and trim the production capacity of turbines in their wakes.
“To cite a speciﬁc example,” they write [PDF], “Archer and Jacobson assumed a power production density of 4.3 W m2 yet … production densities are not likely to substantially exceed 1 W m2, implying that Archer and Jacobson may overestimate capacity by roughly a factor of four.”
In fact, Keith and Adams say that the 100 square kilometer wind farms that would be needed in a big-build-out scenario could leave output at a woeful 0.5 to 1 watt per square meter.
This possibility doesn’t mean much for the near-term future of wind; it’s not anywhere near deployed at a scale to cause the impacts being discussed. But wind is among the few renewable energy resources that most scientists think could have a chance of carrying a major part of the electricity load in a low-carbon future – and if Keith and Adams are correct, that could be in doubt.
“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 said in a Harvard release.
A number of researchers have said we could do exactly that. In addition to the (Christine) Archer and (Mark) Jacobson study mentioned, last fall saw another report that said even pulling a massive 438 TW of power from the winds would be “unlikely to substantially affect the Earth’s climate.”
Keith thinks otherwise.
Covering Earth in wind farms, he said, “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.”
(Then again: If this can be made to work, maybe there’s no problem at all?)