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The proposed tidal lagoon would enclose Swansea Bay with a rock wall incorporating 16 turbines and generating 320MW of electricity. Photo credit: Tidal Lagoon Power

By Richard Sadler

Ambitious plans have been drawn up for a network of "tidal lagoons" around the UK coast that could provide up to a quarter of the country's electricity—and there is potential to roll out the technology in many parts of the world.

Tidal lagoons work by using a wall to capture a body of water in the sea or a tidal estuary pushed in on the rising tide. The water drives turbines as the tide comes in and then, as the tide falls, the turbines are reversed and the energy from the falling tide is harnessed again.

As Geoffrey Chaucer, one of the earliest English poets put it: "Time and tide wait for no man." Unlike with wind and solar, the amount of energy being produced from tides is predictable months in advance and is now being recognized as a major renewable resource.

More Tidal Lagoons

Planning approval has already been given for a £1.3 billion pathfinder project at Swansea Bay, South Wales, described by developers as "a scalable blueprint for a new, global, low-carbon power industry." Another nine lagoons are planned around tidal hotspots in the Severn Estuary and North-West England/North Wales. These would have the potential to generate 25,000MW of electricity—enough to provide 12 percent of the UK's electricity needs.

The company behind the proposals, Tidal Lagoon Power, already has teams working in Northern France and India and is studying opportunities in Mexico and Canada's Atlantic coast. Further tidal lagoon markets may exist in South America, China, South-East Asia and Oceania.

Tidal power is recognized by the EU's Joint Research Centre as a key contributor to the continent's future energy mix. Its main attraction is that, unlike other renewable energy sources, it does not require the wind to blow or the sun to shine.

An oceanographer at Southampton University, Dr. Simon Boxall, said the technology has improved to the point where tidal energy was a "no-brainer," with the latest bi-directional turbines capable of generating power on both incoming and outgoing tides. He said that with sufficient investment it could provide up to a quarter of UK electricity needs within 20 years.

"We can always rely on tides—they come in and they go out and they will continue doing so for thousands of years. Parts of the UK have tidal ranges in excess of 15 meters, so that's a heck of a drop of water and that's happening twice a day—or four times a day when you count the water coming in and going out," said Dr. Boxall.

"The other great advantage is that the tides aren't the same in different locations, so if you've got a network of tidal power stations you are always generating electricity: 24 hours a day, seven days a week," added Dr. Boxall.

In December a former UK energy minister, Charles Hendry, published an independent review, concluding: "Power from tidal lagoons could make a strong contribution to UK energy security, as an indigenous and completely predictable form of supply."

He said the UK was well-placed to take a global lead and with economies of scale and mass manufacture of turbines, turbine housing and other components costs could be substantially reduced.

Cheap Electricity

To be viable the new industry would require subsidies, with a guaranteed premium price for electricity generated. However, Hendry calculated that in the long term tidal lagoons will work out cheaper than wind and "significantly less expensive" than nuclear. And they could go on generating for 140 years—providing clean, subsidy-free energy long after other energy plants have been decommissioned.

The technology is not without its drawbacks. Artificial lagoons can cause increased silting-up of shipping lanes. Tidal estuaries are also important for wading birds, marine mammals and migratory fish and conservation groups have warned that the ecological impacts of tidal lagoons are not well understood and that any roll-out of lagoons in the UK should be conditional on the Swansea project being tried and tested. Backers of the technology say management practices can be adapted to address such concerns—and they point out that lagoons can provide environmental benefits, acting as artificial reefs for marine wildlife.

The UK government is expected to announce a final decision on the Swansea Bay project within the next few months.

Reposted with permission from our media associate Climate News Network.

Scotland, already a renewable energy powerhouse, has launched the first and largest free stream tidal power project in the world.

MeyGen

The MeyGen tidal stream project, operated by Edinburgh-based tidal developer Atlantis Resources Limited, aims to deliver 398 megawatts of energy—harnessed purely from water currents—to the grid.

The goal of the project is to help develop Scotland's marine renewables industry, creating jobs and investment, the Scottish government said. The project is expected to generate around £275 million (about $360 million) for the country's economy.

Tidal stream generators work similarly to wind turbines, but instead of air currents they draw energy from waves. This form of hydropower has incredible promise as a form of carbon-free energy, but progress has been slower than expected. It wasn't until 2014 that the MeyGen project became the world's first large-scale tidal project of its type to successfully reach a funding agreement.

Scotland's First Minister Nicola Sturgeon visited Nigg Energy Park in the Scottish Highlands on Monday to help unveil the array's first turbine. The Scottish government has provided £23 million (about $30 million) to fund the first phase of the MeyGen tidal farm.

"I am incredibly proud of Scotland's role in leading the way in tackling climate change and investment in marine renewables is a hugely important part of this," Sturgeon said. "MeyGen is set to invigorate the marine renewables industry in Scotland and provide vital jobs for a skilled workforce, retaining valuable offshore expertise here in Scotland that would otherwise be lost overseas. Highly skilled operation and maintenance jobs will also need to be carried out locally, providing strong local employment opportunity for rural areas."

According to Maritime Journal, four 1.5 megawatt turbines, weighing nearly 200 tons each, make up Phase 1a of the project. The turbines will stand 15 meters tall and with blades 18 meters in diameter. The turbines will be installed on their foundation structures at Nigg before its eventual deployment to the MeyGen site in Pentland Firth, a strait in the north of Scotland known for its vast and untapped quantities of tidal, wind and wave power.

Former Energy Secretary Ed Davey said in a 2014 statement that "wave and tidal power have the potential to provide more than 20 percent of the UK's electricity needs, and MeyGen could pave the way for future projects in the Pentland Firth."

Atlantis said that it is on track to deliver power to the grid from MeyGen Phase 1a later this year—"a landmark event for the global marine power industry." Once construction of the full array is complete, the MeyGen tidal farm will consist of 269 turbines and generate enough energy to power 175,000 homes in the United Kingdom.

"Today marks an historic milestone not just for Atlantis and our project partners, but for the entire global tidal power industry," Atlantis Resources CEO Tim Cornelius said. "It gives me enormous pride to have reached this juncture after 10 years of tireless work, preparation and planning by everyone associated with this project. This is the day the tidal power industry announced itself as the most exciting new asset class of renewable, sustainable generation in the UK's future energy mix. This is an industry that is creating jobs and Scotland is the undisputed world leader of this high growth sector."

Following the Brexit, a cloud of uncertainty has remained over the UK's climate policy. Scotland has its own climate goals, but the rest of the UK does not.

During Sturgeon's visit to the Nigg Energy Park this week, the first minister called on the UK government to end uncertainty around subsidies for wave and tidal stream projects which is putting the marine sector at risk, the Scottish government said.

"There is no doubt that the eyes of the world are on this project which is why the Scottish government's investment is so crucially important," Sturgeon said. "But it is absolutely vital that the UK government honors its earlier commitment to provide a ring-fenced allocation for marine energy in its renewables support scheme. They must tackle the current uncertainty that exists before they cause irreparable damage to the long-term prospects for the sector."

According to UPI, "The British government last year announced plans to end public subsidies for some parts of the renewable energy sector, defending the move as a way to keep consumer bills low."

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