Maritime News | Tidal Energy
A pair of sleek, winged machines are “flying” – or at least swimming – beneath the dark waters of the Faroe Islands in the North Atlantic.
Known as “sea dragons” or “tidal kites“, they look like aircraft, but these are in fact high-tech tidal turbines, generating electricity from the power of the ocean. The two kites – with a five-metre (16ft) wingspan – move underwater in a figure-of-eight pattern, absorbing energy from the running tide. They are tethered to the fjord seabed by 40-metre metal cables.
Their 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.
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.
The electricity is sent via the tethering cables to others on the seabed, and then to an onshore control station near the coastal town of Vestmanna.
The technology has been developed by Swedish engineering firm Minesto, founded back in 2007 as a spin-off from the country’s plane manufacturer, Saab.
The two kites in the Faroe Islands have been contributing energy to Faroe’s electricity company SEV, and the islands’ national grid, on an experimental basis over the past year.
Each kite can produce enough electricity to power approximately 50 to 70 homes. But according to Minesto chief executive, Martin Edlund, larger-scale beasts will enter the fjord in 2022.
“The new kites will have a 12-metre wingspan, and can each generate 1.2 megawatts of power [a megawatt is 1,000 kilowatts],” he says. “We believe an array of these Dragon-class kites will produce enough electricity to power half of the households in the Faroes.“
The 17 inhabited Faroe islands are an autonomous territory of Denmark. Located halfway between Shetland and Iceland, they are home to just over 50,000 people.
Known for their high winds, persistent rainfall and rough seas, the islands have never been an easy place to live. Fishing is the primary industry, accounting for more than 90% of all exports.
The hope for the underwater kites is that they will help the Faroe Islands achieve its target of net-zero emission energy generation by 2030.
While hydro-electric power currently contributes around 40% of the islands’ energy needs, wind power contributes around 12% and fossil fuels – in the form of diesel imported by sea – still account for almost half.
Mr Edlund says that the kites will be a particularly useful back-up when the weather is calm. “We had an unusual summer in 2021 in Faroes, with about two months with virtually no wind,” he says.
“In an island location there is no possibility of bringing in power connections from another country when supplies run low. The tidal motion is almost perpetual, and we see it as a crucial addition to the net zero goals of the next decade.“
Minesto has also been testing its kites in Northern Ireland and Wales, where it plans to install a farm off the coast of Anglesey, plus projects in Taiwan and Florida.
Source : BBC News
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