Today, we're going to tilt at windmills. 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.
Don Quixote dwelt in the twilight of the age of chivalry -- in the fourteenth or fifteenth century -- but he was a creature of the late-16th-century author Cervantes. Early in the story, he cries,
Look there, my friend Sancho Panza, where thirty or
more monstrous giants present themselves, all of whom
I mean to engage in battle and slay!
And he points to a very large presence of power-generating windmills dotting the Spanish landscape.
The windmill rapidly came into wide use in Europe during the twelfth century -- 200 years before Quixote and 400 years before Cervantes. A debate has gone on as to whether it was brought to Europe from the Holy Land, or vice versa, by crusaders. The current best guess is that it originated in Northern Europe. The waterwheel had been in wide use for a hundred years when the windmill came along. Windmills were more complicated, and they were at the mercy of the sometimes fickle winds. But they could deliver more power than a waterwheel, and they made it possible to grind grain where there were no streams -- in places like the Dutch lowlands and the Spanish plains.
By 1760 windmills had reached an astonishing level of sophistication. They were equipped with automatic regulators that controlled the speed of rotation, that adjusted the pitch of the fan blades for maximum power at a given wind speed, and that oriented the fan so it always faced directly into the wind. When they were were used for milling, they were equipped with devices that regulated the pressure of the millstones on the grain.
But it was also in the 1760s that Watt developed a vastly improved steam engine. As the 18th century ended, windmill development was abandoned in favor of these new engines. Watt was the Quixote who really slew the windmill.
Of course, windmills didn't go away completely. Today they're still a choice power supply for isolated use where there's no commercial electricity -- for filling cattle watering troughs out on the prairie, for example. They played a large role in opening up the American West.
Lately we've seen a new interest in wind power. Latter-day engineers are concocting a dizzying set of improvements in the hope of using windmills for electric power generation.
But 18th-century windmills remain an almost forgotten glory that might well impress any engineer today. For example, the variable-pitch propellors used in these mills over 200 years ago are an innovation that airplane designers didn't rediscover until the 1930s.
I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.
George, B., Reaping the Wind. American Heritage of Invention and Technology, Vol. 8, No. 3, Winter 1993, pp. 8-14.
Kealey, E., Harvesting the Air: Windmill Pioneers in Twelfth-Century England. Berkeley: University of California Press, 1987, Chapter 7.
Mayr, O., The Origins of Feedback Control. Cambridge, MA: MIT Press, 1970.
Righter, R.W., A Few Words About This Picture. American Heritage of Invention and Technology, Vol. 7, No. 1, Spring/Summer 1991, pp. 28-31.
White, L. Jr., Medieval Technology and Social Change. New York: Oxford University Press, 1966, Chapter 3.
(From the October, 1896, Scribner's Magazine)
Artist's sketch of an actual windmill on the Quixote's plains of La Mancha