Minesto, a technology developer founded in 2007 as a spin-off from Swedish aerospace manufacturer Saab, has launched what it terms 'sea dragons' or 'tidal kites' to generate electricity from marine energy. The tidal turbines look like an aircraft and with a 5 m (16 ft) wingspan, moves underwater in a figure-of-eight pattern, absorbing energy from the running tide. The machines are tethered to the seabed by 40 m metal cables, and movement is generated by the lift exerted by the water flow, just as a plane flies by the force of air flowing over its wings. Other forms of tidal power use technology similar to terrestrial wind turbines, but the kites are something different. The moving 'flight path' allows the kite to sweep a larger area at a speed several times greater than that of the underwater current. This, in turn, enables the machines to amplify the amount of energy generated by the water alone. At an installation in the Faroe Islands, an on-board computer steers the kite into the prevailing current, then idles it at slack tide, maintaining a constant depth in the water column. If there were several kites working at once, the machines would be spaced far enough apart to avoid collisions.
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