A renewable energy charity has set its sights on harnessing the tides in Swansea Bay to provide power for up to 10,000 homes.
Powerful tides: The tidal lagoon would harness Swansea Bay
The Environment Trust says it is conducting tests to demonstrate the technology behind its plans to create a £30m tidal lagoon just east of the city's docks and marina.
It claims a private investor is already lined up for the first stage of the proposed project, to build a mile-round ring of rock and concrete housing the latest generation of hydro-electric turbines.
The idea is still at an early stage, but the London-based trust has said it hopes to present its engineering report to the Welsh Development Agency by the end of the year.
If the scheme goes ahead and is successful, the charity says it has plans for second project more than ten times the size off Rhyl in north Wales.
The trust has spent £100,000 hiring an independent firm of engineers to test its blueprints for a "two-directional" tidal lagoon, capable of generating up to 30 megawatts of power on both the incoming and outgoing tide.
Energy ring: The mile-round lagoon would contain turbines
Spokesman Jonathan Sills said the man-made construction - designed to be a metre above the water at high tide - would channel water through turbines hidden in its walls.
He said: "It would be a lot less intrusive visually that an offshore windfarm or a barrage like the Cardiff barrage - because it would be a mile offshore, it would by partly submerged all the time.
"We are working with the port authority to ensure that is would not affect navigation. It is about as environmentally benign as you can get."
Mr Sills said the proposed project would pay for itself within ten years, leaving the developer to sell off "free" electricity for decades afterwards.
He added the materials, including sand and rock, would also benefit marine life.
"You are by no means destroying habitats, you are creating them," he said.
He added the charity had plans for a 432 megawatt tidal lagoon at Rhyl, north Wales, but wanted to show that the smaller Swansea scheme could work before pressing ahead with the larger one..
Last week, the first of the 30 turbines in the North Hoyle windfarm at Prestatyn, capable of producing enough power for 50,000 homes, began flowing.