A £25 million underwater renewable energy project off Anglesey is about to take a major step forward.

The construction of the concrete base for Swedish firm Minesto’s tidal energy project, which involves the use of ‘kites’ tethered to the sea floor, is almost finished.

Minesto hopes the technology, called Deep Green, will eventually generate 80 megawatts (MW) of electricity, enough to power 70,000 homes.

The kites will be installed in the Holyhead Deep, four miles off the Anglesey coast, and a proposed trial will involve a half-megawatt generator installed and operated next year in order to demonstrate the new technology.

The concrete base, which measures 1,288 cubic metres, is being made by Ruthin-based Jones Bros Civil Engineering UK at Cammell Laird in Birkenhead.

It will be hollow on the inside to allow it to be floated up the River Mersey and across the North Wales coast.

Its cells will then be filled with water in order to lower it to the bottom of the sea. Once there, the device will be secured to a mooring structure. Jones Bros project manager Eryl Evans said: “This is a complex structure that is progressing well and on schedule.

“To add to the challenges, we’re building this foundation 12 metres deep in a dock.

“This has meant all materials and machines including plant have been lifted in by a crane.

“We’re using approximately 465 square metres of concrete and the final structure will weigh close to 1,300 tonnes.

“We’re excited to be a part of what will be a significant maritime renewable energy project in North Wales.”

Minesto secured a 13m Euros (£11.5m) investment from the European Regional Development Fund (ERDF) through the Welsh European Funding Office in May 2015 for the commercial rollout of its Deep Green technology.

It is Minesto’s first commercial-scale tidal energy power plant.

Martin Edlund, CEO of Minesto, said: “We are well positioned to meet time frames and deliverables towards our public funding partners, to demonstrate the unique advantages of the Deep Green technology and to develop this required source of renewable energy.”