Plans to build a £1 billion tidal lagoon in Swansea have moved a step closer to becoming a reality after the UK Government granted the scheme planning permission.
Developers say the proposed six-mile long seawall would feature 16 underwater turbines capable of generating 500 gigawatt hours of electricity per year - enough to power 155,000 homes for 120 years.
The Department of Energy and Climate Change (DECC) has now given its blessing to the scheme - although there remain further hurdles before work on the lagoon can get under way.
As well as sorting out how much of a government subsidy Tidal Lagoon Power (TLP) would receive, there are also environmental concerns to address.
Nevertheless, the DECC's decision is regarded as a significant step forward.
Announcing the decision, Wales Office minister Lord Bourne said: "We need more clean and home-grown sources of energy.
"Low carbon projects like the tidal lagoon in Swansea Bay could bring investment, support local jobs and help contribute to the Welsh economy."
The Swansea tidal lagoon is planned as the first in a series of up to six similar schemes across Wales and England.
Before work can go ahead, developers have to come to an agreement with the UK Government on how much of a subsidy the scheme will receive.
Independent reports have estimated the project may need help from the taxpayer of around £168 per megawatt hour.
And Natural Resources Wales would have to be convinced the scheme would not harm the area's fish population before granting a marine licence.
But Tidal Lagoon Swansea Bay chief executive Mark Shorrock said things were moving in the right direction.
"Wales led the way providing fuel for the industrial revolution," he said.
"We are now entering the era of the climate change revolution - decarbonising our world in time to avoid two degrees of global warming - and Wales can lead the way with this next revolution.
"We see it as a game changer. A social blueprint that paves the way for a fleet of lagoons that can work in harmony with nature."
Officials also say a lagoon would also boost the city's tourism and provide more jobs.
Friends of the Earth Cymru director Gareth Chubb said tidal power could help break the UK's reliance on fossil fuels.
He said: "There are still environmental hurdles to clear, but provided these can be managed and mitigated, tidal lagoons could make a significant contribution.
"Instead of relying on climate-wrecking fossil fuels, it could help us build a clean and safe energy future."