Underwater Kite Harvests Energy From Slow Currents

Could kites be the secret to capturing tidal energy?

2 min read
Underwater Kite Harvests Energy From Slow Currents

A kite with a three-meter wingspan has just started to produce electricity in a pilot project off the coast of Northern Ireland.

The technology, dubbed Deep Green, consists of a wing with a gearless turbine mounted underneath that is tethered to the ocean floor. As the tide flows over the wing, it glides through the water and the turbine rotates. The tether also contains the unit's power and communication cables. For the pilot, there is an offshore control room in the inlet. The kites don't just float along anywhere they please—operators send them along a controlled trajectory to maximize energy output.

Deep Green can take advantage of lower velocity currents than most tidal technologies (less than 2.5 meters per second), according to Minesto, the company that makes the kites. Minesto hopes to field a 3-megawatt array in 2015.

The pilot involves a scaled-down version of Deep Green; the full-size versions have wingspans of between eight and fourteen meters. The eight-meter carbon fiber kite [PDF] has a rated power of 120 kilowatts at a tidal flow of 1.3 meters per second. The version with a 14-meter wingspan has a rated power of 850 kilowatts at 1.7 meters per second.

Although kite arrays could potentially be deployed in more locations than other tidal turbines, all tidal and wave technologies face considerable challenges, such as surviving in harsh, salty waters and being cost-competitive with other renewable energy options.

The first tidal turbine to produce power for a utility in the United States started operating just last year. Other U.S. projects, such as turbines in New York City’s East River, have not been able to withstand the harsh and powerful marine environment.

The United Kingdom is jockeying to solve the technical and cost issues associated with tidal and wave power. The Scottish government has the Saltire Prize, which will award $15.8 million in 2017 to one of the wave and tidal energy companies competing for the prize

Minesto claims it will be able to compete on cost—not only with other renewable energy technologies, but also with conventional energy sources.

Photos: Minesto

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This photograph shows a car with the words “We Drive Solar” on the door, connected to a charging station. A windmill can be seen in the background.

The Dutch city of Utrecht is embracing vehicle-to-grid technology, an example of which is shown here—an EV connected to a bidirectional charger. The historic Rijn en Zon windmill provides a fitting background for this scene.

We Drive Solar

Hundreds of charging stations for electric vehicles dot Utrecht’s urban landscape in the Netherlands like little electric mushrooms. Unlike those you may have grown accustomed to seeing, many of these stations don’t just charge electric cars—they can also send power from vehicle batteries to the local utility grid for use by homes and businesses.

Debates over the feasibility and value of such vehicle-to-grid technology go back decades. Those arguments are not yet settled. But big automakers like Volkswagen, Nissan, and Hyundai have moved to produce the kinds of cars that can use such bidirectional chargers—alongside similar vehicle-to-home technology, whereby your car can power your house, say, during a blackout, as promoted by Ford with its new F-150 Lightning. Given the rapid uptake of electric vehicles, many people are thinking hard about how to make the best use of all that rolling battery power.

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