Unlimited wind

Exactly how much energy we can feasibly pull from the wind has been something of a controversial question in recent years, with some studies suggesting that wind power has its limits. Simulations unveiled this week by scientists in Delaware and California, though, argue that if anything, economics and politics will hold wind development back, rather than geophysical limits.

Wind-power systems work by taking the kinetic energy of wind and turning it into mechanical energy in the turbine to create electrical energy. Laws of physics tell us that the total amount of energy can’t change, so at least a minor slowing of the wind is expected as it passes through the turbine. New research, published Sunday in Nature Climate Change, used a climate model to estimate that limit, both for turbines placed near Earth’s surface—as they are built now—and for high-altitude turbines, such as the kite-like tethered devices currently under development.

They found that the geophysical limit for Earth-based turbines is 428 terawatts or more but a whopping 1873 TW for high-altitude systems. The current global power demand? About 18 TW.  Another study of wind power’s geophysical limits, published in the journal Energy Policy in 2011, arrived at an upper limit of about 1 TW. But Mark Jacobson, a professor of civil and environmental engineering at Stanford, says that “the calculation of 1 TW was literally done with a back-of-the-envelope single-line equation” and didn’t take actual physical properties of turbines or the atmosphere into account.

All such calculations on the limit aside, we need to remember we do not even have enough cement to build so many turbines. To get to even 100 TW of installed capacity would require somewhere around 20 million very large turbines. A somewhat more realistic 4 million turbines could easily supply about half the world’s power.

The new studies also address a separate issue that arises with massive numbers of wind turbines: Can they actually cause climate change? The changes in kinetic energy that result from millions of spinning turbines do have an effect, but significant alterations to global temperature or weather patterns are only likely at “truly absurd extraction rates.”