A floating island with up to 10,000 homes and shops forms part of an idea to revive a tidal lagoon project in Swansea Bay.
The new scheme - Dragon Energy Island - is seen as a replacement for the failed Swansea Bay Tidal Lagoon which could not get UK government backing.
It is also said to be 30% cheaper than the £1.3bn cost of the previous plan.
Underwater turbines would generate electricity for thousands of homes over a period of 120 years.
Various options are being explored to gain financial backing including from the Welsh Government, which would be responsible for planning and marine licence consents.
Rob Stewart, Swansea Council leader and chairman of the Swansea Bay City Region's task force, said Dragon Energy Island was more ambitious and turned the scheme from an energy project into an infrastructure one.
"An enormous amount of hard work has taken place behind the scenes to develop a new proposal that will generate clean, green power for many generations to come," he said.
Mr Stewart said the lower cost of the lagoon did not include the homes, shops, a solar farm and underwater data centre.
On the floating homes, he added: "This has already been successful in countries like Holland, Germany and Denmark, providing a sustainable solution to issues including population density and climate change."
Councils and other public sector bodies would be invited to buy electricity generated by the lagoon for a set number of years.
Another idea is to convert some of the electricity produced into high-value hydrogen and oxygen for industrial uses.
The previous tidal lagoon project was thrown out last year by the UK government because of its cost, despite getting support from former energy minister Charles Hendry.
An independent report into the new plan said the key question was "whether the ambition to deliver this project aligns sufficiently with the many competing areas to deploy limited public sector resources, and will secure the necessary financial and political support".
The report by Holistic Capital, commissioned by the task force, will be discussed by Swansea Bay City Region's joint committee on 28 May.