In several recent published studies, Adams and other researchers have explored the issue of turbines stealing energy from the wind, creating drag or a "wind shadow" of air slowed by the spinning blades. Each turbine added to a particular landscape captures less energy. "You reach a point that if you add any more turbines, you get no more energy," Adams said.

Developers of wind farms recognize the risk, so they carefully space turbines to prevent one from robbing wind speed from another. But today's wind farms are small compared to the giant complexes needed to meet a significant slice of the world's energy needs. (See related story: "Sizing Up Wind Energy: Bigger Means Greener, Study Says.")

Adams and colleagues argue that