The prospective buyers of the Anglesey Aluminium site have plans for a biomass power station and fish farm which they say could create up to 400 jobs.
Lateral Power also plans to use soiled water from the fish farm and CO2 from the power plant to feed greenhouses where food will be grown.
A spokesman said it would be a "template for the future".
The biomass station will be part of an eco park, which the Welsh government calls an innovative development.
It is early days for the plans, but the announcement of Lateral Power as the preferred bidder is seen as a step forward for job creation.
"Our vision is to provide not only sustainable electricity for the UK power grid but also healthy, freshly grown food products for local and regional cities, reducing the need for imported food and a large carbon footprint," said Lateral Power's chief executive officer, Sean McCormick.
He said he believed the plant at Holyhead would be "one of the largest biomass power stations and the largest combined aquaculture facility in the world".
"The Anglesey Aluminium site is perfectly located for the purpose, having one of the best deep-water harbours in the UK, excellent rail links on the site and connections straight onto the UK power grid.
"We see the Anglesey eco park as a template for the future, and we are incredibly excited at the prospect of now taking it to the planning stage," he said.
The smelting company closed its works at Holyhead two years ago with the loss of nearly 400 jobs.
The Anglesey Aluminium site has been on the market with offers invited in the region of £10m.
Anglesey Aluminium's owners Rio Tinto, the Welsh government and Anglesey council have all had a say during the competitive process.
Business and Enterprise Minister Edwina Hart called the plan "a great example of an innovative new development".
"It will not only provide sustainable electricity for the UK power grid but will also include hi-tech aquaponic centres to produce fresh fish and vegetables," she said.
Ms Hart welcomed the potential to create jobs there.
'Teetering on the brink'
"When Anglesey Aluminium stopped smelting aluminium in 2009 it was a huge loss to the economy of the island.
"With the plans for the eco park and the leisure resort [which was announced earlier this year] there could now be over 1,000 long-term jobs on the way for local people and their families," she said.
Anglesey assembly member and Plaid Cymru leader Ieuan Wyn Jones said Lateral Power would be a "financially secure partnership of a number of companies".
"Four hundred new jobs is fantastic news for the island of Anglesey and couldn't come at a better time as these jobs are sorely needed here," he said.
"We're teetering on the brink of another recession and only by investing in jobs will we avoid another one."
Anglesey council said the eco park was just the type of development the Anglesey energy island programme was designed to attract.
"This is a time of exciting new opportunities to lay a solid foundation for the future of Anglesey, and we look forward to being part of that," said council leader Bryan Owen.