Windless

Solar power and wind power are becoming increasingly used as sources of energy for humanity’s needs. Where we once generated electrical power mostly from burning nonrenewable fossil fuels, atmospheric pollution and global warming have pushed us to begin shifting towards these so-called “green” sources of energy. Neither wind nor solar pollutes the air, and neither contributes to global warming.

Another advantage of both solar- and wind-derived electrical power is that both are essentially inexhaustible. As far as we humans are concerned, there will be no end to solar energy impinging on Earth (at least for another five billion years or so) and we can surely count on the wind to keep blowing. Yes, clouds can obscure the sun temporarily and the breeze may die for a bit, but these are only transient losses. The clouds will soon pass and the wind will pick up again.

But wait a minute. Is the wind really unlimited? Maybe there is just so much energy we can extract from breezes, before we deplete them. I can’t ever see us using up all the bounty of the sun, but isn’t the wind a little more finite? We drain a battery and the flashlight goes dead. The gas tank empties and the car rolls to a stop. Would it be possible to suck all the oomph out of the wind?

This fanciful and rather ludicrous thought popped into my head, some time back while lounging in the tub. In a rather absurd scenario, I imagined a long string of wind turbines, facing bravely into the breeze. The first one spins robustly, taking a little bit of energy from the wind. The next one spins a wee bit slower, as it encounters a wee bit slower wind. On down the line it goes, until the wind just peters out and cannot spin that last turbine. The tilting windmills have killed the wind! Dead calm…no electricity! Of course that’s a ridiculous picture I have painted…or is it?

Just recently I was reading the Winter 2013 issue of Conservation Magazine and came upon an article cleverly titled “Limited Windfall.” It seems that a university research group conducted a study of the density of wind turbines on a wind farm and discovered that, once the number of generators reaches a certain limit in a given area, adding more turbines will yield no additional increase in electrical power. The farm gets saturated; no more power can be sucked from the wind, they found, if the optimum turbine density is exceeded. Their recommendation: determine the density limit for a given area and don’t build any more turbines than that.

Now, that’s not quite the same crisis that I dreamed up in my absurd scenario, but it ain’t that far off! I wonder if someone should do a similar calculation for solar power. I’d hate to think that we might install so many solar arrays that we steal the sunshine and create perpetual night!