Ever since windmills arrived more than a thousand years ago, engineers have wrestled with how to make them more efficient. As Popular Science observed in December 1923, German manufacturers designed a turbine with blades that revolved around a wheel, which rested on a ball bearing so that they always faced the wind at a right angle. “A breeze barely sufficient to stir the leaves of the trees will set the great wings in motion,” we wrote. And if a gale came, a braking mechanism kept the blades from turning too rapidly.

Now engineers have developed a turbine with blades that bend with the wind to capture more energy. The design also helps to protect the turbine from storm damage. Read more about how it works here.

Slow Growth For High-Power Turbines

When blades started spinning on the first U.S. wind farms in the 1980s, turbines were capable of producing up to a few hundred kilowatts. Today, turbines are 10 times more powerful, but typical capacity has plateaued.

Dots positioned to indicate the number of turbines built each year at each electricity-generation capacity. Time runs from 1980 to 2014, capacity from 0 to 3 in megawatts. The more-powerful turbines have come online in the past decade or so.

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Larger turbine development has leveled off, partly due to cost constraints. Small turbines, while less prevalent, still power homes, farms, and schools.

This article was originally published in the June 2015 issue of Popular Science, under the title “Machines That Follow The Wind.”