Swooping a turbine through the sea's currents could be a cheaper way to harness the power of the oceans

As a surfer, I know the power of the sea and also that going with the flow is the only way to survive. And that's what I like about this underwater kite-turbine, being developed by Swedish company Minesto.

They will do the first sea trial in Strangford Lough in Northern Ireland this summer. The kite, which at full size will have a wingspan of 8-14 metres, carries a turbine below it. The kite is tethered by a cable to the sea floor and then "flies" in the tidal stream. It swoops round in a figure-of-eight shape to increase the speed of the water flowing through the turbine tenfold (see company video below), just as sailing boat cuts across the wind to go faster.

That manoeuvre means the kite can generate renewable electricity in tidal streams that would be too slow to drive the first-generation tidal devices, such as the SeaGen turbine also installed in Strangford Loch. The kite has neutral buoyancy, so doesn't sink as the tide turns and the turbine mouth is protected to stop fish flying through.

For those, like me, geeky enough to like the numbers, here they are. Ander Jansson, Minesto's managing director, tells me the kite should work in flows of 1-2.5 metres per second, while first-generation devices need over 2.5m/s. Depending on the location and size of the kites, each will have a capacity of between 150 and 800kW, and be deployed in waters 50-300m deep. The test will be at one tenth scale.

Other second-generation tidal devices include a floating turbine being developed by ScotRenewables in Orkney.

Stephen Wyatt, a marine energy expert at the Carbon Trust, says devices such as kites that exploit lower speed tidal currents would expand the UK's tidal resource by 16%, meaning it could supply about 1% of the UK's current total electricity needs. The Carbon Trust and Invest Northern Ireland will spend £350,000 funding the trials over the next 18 months.

What about the challenges ahead? Wyatt says installing the devices is one of the hardest steps. A boat has to get in to drill the foundations and deploy the kite during the short time while the tide is slack. Jansson says the key challenge will be getting the technology to commercial viability, where it can compete on cost with other ways of generating electricity. He suggests making and installing two turbines, with a joint capacity of 1MW, could cost £1.8-£2m, though he expects fleets of kites to be deployed to benefit from economies of scale.

"The sea is an extremely tough environment and I think this is why the sector has taken some time to develop," says Jansson, speaking from the RenewableUK Wave and Tidal conference. "But it is really starting to kick off now."

One per cent of the UK's electricity may not sound like much, but it's enough to power the city of Newcastle, and I think we need all the clean energy we can get.