Environment

Underwater Kites that Could Harness Tidal Power

An underwater kite called ‘Deep Green’ offers a unique new way of converting tidal currents into electrical energy. Find out how…

posted on 01/24/2011
Alka Sharma
Scribol Staff

Deep GreenPhoto: © Anders Jansson

This design might look like any ordinary kite, swooping and diving along. However, it is actually a unique technology which it is hoped will convert ocean tidal currents into energy and produce electrical power miles below the water’s surface around Britain.

Formed in 2007, Swedish Company Minesto, a spin-off from the Saab group, has devised this unique underwater kite, named ‘Deep Green’, which is expected to come into service soon around Britain’s coast. In comparison with other existing methods of energy extraction, Deep Green is not only smaller in size, but is also very cost effective.

low and high tidesPhoto: UNguyinChinaTop Down view of a Dam. Blue and dark red colors indicate low and high tides.

Mechanism: To understand how it works, let us discuss how tides are formed. Tidal currents are produced as a result of the gravitational attraction of the Sun, the Moon and the Earth’s rotation. Because of the varying gravitational pull between these forces, the oceans on each side of the globe rise and then fall back twice in a single day. In short, the greater the variation, the greater will be the tidal electricity generated. The energy extracted from such relative motion is called tidal power and is the only form of such energy in existence.

Deep Green underwater kites are basically tidal turbines with a diameter of one meter. These kites fly up from the ocean floor in a figure eight with a wing span of 12 meters. Each kite has a wing and rudder, which is attached to the bottom by means of a tether. The mechanism works in two phases:

Phase one: A lift force is created when the tide hits the wing, which increases the flow of water into the turbines 10 times faster than the current speed.

Phase two: The kinetic energy generated is then converted to electrical energy.

Minesto’s new technique of generating tidal energy offers a great option for green energy. The concept is quite similar to that of a wind kite. You might think, why didn’t the company simply design something as simple as a wind energy turbine? Well Ted Rosendahl, chief technical officer with Minesto explains: “Water is 800 times denser than air, so kites could produce 800 times more energy. In case of calm waters or small water with low flow velocity, it can produce 500 kW of power.”

“Minesto’s owners are a perfect constellation of industrial companies and entrepreneurial finance companies with strong global networks. We look forward to commercialise our technology with the help of old and new owners,” said CEO Anders Jansson.

Minesto_testPhoto: © Anders Jansson

The company has done several tests so far and has been successful in generating power from the waves. The company has also raised over €2m to finance further tests. The next major technical step is an ocean installation after summer 2011, in Northern Ireland. Ranked as one of the 50 best inventions of 2010 by Time Magazine, we hope that this ocean generator will bring about an energy revolution and soon start contributing as one of the best solutions to increasing worldwide demands for electricity.

Source: 1, 2, 3, 4

Alka Sharma
Scribol Staff