10 Advancements in Environmental Engineering

High-altitude Wind Energy from Kites
In this photo of Makani’s test of Wing 7 in Alameda, California in late 2011, you can see the energy-generating turbines mounted on the structure. ©Makani Power, A. Dunlap, 2011

When we think of harnessing the power of wind to provide electricity, most of us probably think of windmills. Very few think kites. But a San Francisco-area start-up founded in 2006 called Makani Power has been working on using kite-like wind turbines attached to tethers to generate wind power at high altitudes, where there are stronger and steadier winds than we have at ground level. Makani means wind in Hawaiian, incidentally.

The tethers can reach up to 2,000 feet (609.6 meters) above ground, and they're both the suspension method and the method for transmitting power back to the base. The kites themselves are around one hundred feet long and made of carbon fiber. They have four propellers and incorporate sensors and GPS units on the wings that transmit data that can be used to optimize their flight. They actually fly in loops rather than hover. And they are light enough to maintain altitude in winds slower than 15 miles per hour (MPH).

The turbines reportedly have the potential to generate twice as much power, perhaps even more, at half the cost of modern ground-level wind turbines. The costs are competitive with that of coal burning, and take up less space than other power generation methods.

The kites -- still a few years away from commercial availability -- are likely to be used along shorelines, or in the ocean attached to buoys. Makani Power has received funding from Google and the Advanced Research Projects Agency for the Department of Energy (ARPA-E), and it is slated to be acquired by Google X, the laboratory working on projects like Google Glass and self-driving cars.

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