A massive switch over to wind power may actually be worse for global climate systems than current catastrophic levels of greenhouse gas emissions, according to a study conducted by researchers from Harvard University and published in the journal Environmental Research Letters.
"People have often thought there's no upper bound for wind power - that it's one of the most scalable power sources," said researcher David Keith, an international policy expert on climate technology.
But the new atmospheric modeling study found that assumption to be wrong.
The problem is that the energy that windmills "harvest" has to come from somewhere, and where it comes from is the wind's velocity: simply put, the wind blowing through a windmill slows down. This drag, or "wind shadow," is a critical component of wind farm design, as it means that windmills cannot be placed too close to each other and still remain effective.
The new study found; however, that it's not just windmills that have wind shadows - wind farms cast their own, larger shadows, made up of the interactive effect of all the individual windmills. And that means that wind farms cannot be placed too close to each other, either. And the more wind farms you build, the more shadows you create, until you are actually altering wind patterns on a planetary scale.
"One of the inherent challenges of wind energy is that as soon as you start to develop wind farms and harvest the resource, you change the resource, making it difficult to assess what's really available," Adams said.
In practical terms, the study found that although prior studies have estimated the generating capacity of wind megafarms at two to seven watts per square meter, the wind shadow effect actually limits their capacity to only 0.5 to one watt per meter.
Worse than carbon dioxide?
"The real punch line," he said, "is that if you can't get much more than half a watt out, and you accept that you can't put them everywhere, then you may start to reach a limit that matters."
And one thing is clear: putting wind turbines "everywhere" would be devastating for our planet's climate systems.
"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," Keith said.
Sources: Science Daily