Swansea Bay tidal lagoon to harness British sea power

The twice-daily surge of the Atlantic Ocean on to UK coastlines creates one of the highest tidal ranges in the world. Harnessing this power potential could provide a vast renewable energy source, one that is predictable and more sustainable than other green energy initiatives, according to British company Tidal Lagoon Power.

They are planning to build the world's first tidal lagoon in Swansea Bay, south Wales; expected to cost 1.3 billion pounds ($1.58 billion), but able to generate enough electricity for more than 150,000 homes per year.

The project would involve building a 9.5 km (6 mile) horseshoe-shaped sea wall in Swansea Bay, about 170 miles west of London.

When the tide drops, the difference between water levels inside and outside the lagoon causes water to pass through a bank of bi-directional 23ft diameter hydro turbines to produce electricity. Similarly, when the tide rises, power would be generated as water fills the lagoon.

"Imagine a run-of-river hydro-station in a river but the water being able to run back up the river again," said Mark Shorrock of Swansea Bay Tidal lagoon.

"We'll have a breakwater built out of the sea with turbines in the outer edge of it. Those turbines are capable of turning when you empty the water out of our man-made lagoon and when you fill the water up. So they generate electricity on the flood tide and on the ebb tide. And the big thing that we've got here in Great Britain is these enormous tides, so just 3 hours after high tide the level of the ocean is already 4-and-a-half metres lower than the height of the water in the tidal lagoon; we open the gates in the tidal lagoon, let the water through the turbines, and we generate electricity. It's five Olympic swimming pools… every second, and that generates enough electricity for 155,000 homes per year."

While tidal changes have been harnessed before to generate power, mostly deploying a barrage across a stretch of water, this would be the first to enclose it, effectively creating a man-made lagoon.

Shorrock added that the tidal lagoon would be a long-term solution to meeting some of Britain's energy needs. Solar and wind farms all need to be maintained and repaired, while nuclear plants typically only last around 45 years.

"Once we build the breakwater wall, it's going to be there for the next 120 years. When we put the turbines in there, they're there for the next 120 years. So what's quite interesting about this piece of infrastructure is it's inter-generational. It'll last for the next five generations, producing power throughout its lifetime, working with the rhythm of the tide," Shorrock told Reuters.

It's hoped this 320 megawatt project could act as a template for six much larger projects around the country. If all seven projects were built they could have a total capacity of 17.6 gigawatts, equivalent to around 30 percent of the country's current electricity capacity.

"One of the really striking things about a fleet of tidal lagoons, and our proposal is to start here in Swansea and then build lagoons all around Great Britain, is that there's a tidal time difference around the country. So you can get to 24 hour certain generation from renewables. So that's the biggest difference between tidal power and, say, wind and solar power is that the wind is intermittent and you get the sun during the day. With the tides you always have certain electricity at certain times of the day and then that's staggered at shifts by 40 minutes every day," added Shorrock.

The project was granted a Development Consent Order in 2015 and is currently awaiting a final green-light from the government. Construction of the entire project will take four years, with the first power generated in year three.

Britain needs to invest in major new infrastructure to replace ageing coal and nuclear plants set to close in the 2020s, and also needs to reduce is greenhouse gas emissions to meet its climate targets. — Reuters