Charles Q. Choi in Inside Science:
Wind power is often touted as environmentally friendly, generating no pollutants. It is an increasingly popular source of renewable energy, with the United States aiming to produce 20 percent of its electricity by wind power by 2030. Still, there have been questions as to how much energy wind power can supply the world, and how green it actually is, given how it pulls energy from the atmosphere.
To learn more, climate scientist Katherine Marvel at Lawrence Livermore National Laboratory, in Calif., and her colleagues developed a global climate model that analyzed how wind turbines would drag on the atmosphere to harvest energy from winds at the planet's surface and higher altitudes. Historically, people have built wind turbines on the ground and in the ocean, but research suggests kite-borne turbines could generate more power from steadier, faster high-altitude winds.
Adding wind turbines of any kind slows winds, and Marvel and her colleagues found that adding more than a certain amount of turbines would no longer generate more electricity. Still, their simulations suggest that at least 400 terawatts — or 400 trillion watts of power — could be generated from surface winds, and more than 1,800 terawatts could be extracted from winds throughout the atmosphere. In comparison, people globally currently use about 18 terawatts of power.
More here.