Today, an old wind blows anew. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.
It's time for a progress report on windmills: We heard a lot about windmills 10 or 15 years ago. Fields of windmills with propeller blades sprouted up -- mostly in California. Now Robert Thresher and Susan Hock give us an update, and it is promising.
By now those fields of windmills have quietly come to represent an installed capacity of some 1600 megawatts of energy. That's only 1/2000 of America's total energy production. Still, it is enough to supply a typical major city.
When those windmills first went in, in the early '80s, the capital and operating costs came to a pricey 25 cents per kilowatt-hour. They could exist only with government subsidies. By now good engineering has brought the cost down to around 8 cents per kilowatt-hour.
That's still too high to compete on the open market, but the open market is deceptive. Fossil fuel costs are low because we subsidize them invisibly: in health care for lung disease, struggles with Middle East oil-producing countries, and likely costs of coping with global warming. We're borrowing from the future.
Meanwhile wind-power costs keep dropping. We now look for a price of only 4 cents per kilowatt-hour by the year 2000. The modern power-generating windmill began taking form during the 1750s, when engineers added automatic control elements. They invented the fan-tail device for constantly orienting the blades into the wind and blade-reefing devices to change the pitch of blades.
But coal-powered steam engines distracted us. We forgot about windmills except for remote locations -- farms and early railroad stops. So what we've done with windmills in recent years is a direct continuation of what began in the 18th century and continued in airplane propeller design after WW-I.
Today, a typical power generation windmill has a 3-bladed propeller, maybe 80 feet in diameter. It might generate 250 kilowatts. As aerodynamic blade design improves, and as computer control systems become more sophisticated, efficiency also rises. These modern windmills once captured 20 percent of the wind energy passing through them. Now they capture 70 percent. The new generation of windmills will sit on 200-foot towers and produce 500 kilowatts -- 40 times as much as the best 18th-century windmills.
But I sound a warning: All power sources bring mischief when we commit ourselves to them fully. Water wheels exacted such a cost in wood by 1300 that European forests vanished. Our commitment to oil creates worldwide economic havoc. Completely harnessing the wind would tie up huge tracts of land and affect the winds themselves. The wind is filled with promise today. But it'll only fulfill that promise in a diversified energy economy.
I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.
Thresher, R.W., and Hock, S.M., Wind Systems for Elecrical Power Production. Mechanical Engineering, Vol. 116, No. 8, pp. 68-72.