Landscape view to Stroma Island from John O'Groats harbour

MeyGen tidal power project poised to feed Scottish Highland electricity grid

Image credit: Getty images, image source

The MeyGen tidal power demonstration project will be a world first, feeding in to a Scottish Highland electricity grid that will have received an upgrade unprecedented since hydropower’s heyday in the middle of the last century.

Sited in the Pentland Firth in northern Scotland, the MeyGen tidal power project is the world’s first commercial-scale tidal energy scheme. The breakthrough of first electricity from the flagship scheme is expected in late 2016, with supply to the grid scheduled for early 2017.

Phase 1A of the scheme comprises four 1.5MW turbines in the Inner Sound - a sea channel between the Caithness coast and the island of Stroma. The Inner Sound forms part of the powerful Pentland Firth where the Atlantic meets the North Sea.

The power of strong currents here makes it an ideal place for tidal generation. Yet the area has harsh weather and extreme sea conditions, even in the Inner Sound, where the tidal race can be very fast, at up to about four metres per second. Nearby sea hazards include the ‘Merry Men of Mey’ - dangerous and unpredictable sea conditions that can reach across the firth to Orkney - and the Swilkie, a powerful whirlpool off Stroma from where Norse legend declared that the oceans’ salt originates.

In the UK, there is a huge estimated energy resource of 29TWh per year available in tidal currents, of which 11TWh are in the Pentland Firth. By comparison, all of the UK’s nuclear power plants generated about 64TWh of electricity in 2015.

Intermittent electricity production has been viewed as a problem for wind, wave and solar power as the sun doesn’t always shine and the wind doesn’t always blow. These renewable energy sources have traditionally been used in combination with more controllable power sources like coal and nuclear plants, although now the potential to use batteries to store renewable energy is starting to come to fruition.

In order to help exploit tidal and wave power, Orkney’s European Marine Energy Centre (EMEC) was set up in 2003 - its first wave test site opened in 2004. The centre was the world’s first real sea test centre for marine energy devices. Developers using the facilities at EMEC are testing electrical generation and investigating how equipment can be installed, operated and maintained in challenging weather and sea conditions.

Amongst the companies using EMEC are Andritz Hydro Hammerfest and Atlantis Resources, both of which are supplying turbines for the MeyGen project. Atlantis has other tidal power work at the Fundy Ocean Research Centre for Energy in Canada, the UK Energy Technologies Institute Tidal Energy Converter Project, Daishan in China, Mundra in India and San Remo in Australia.

The Crown Estate owns almost the entire seabed around Scotland and, back in 2010, awarded a tidal power lease for the Inner Sound to MeyGen. At that time, it was a joint venture between Atlantis, International Power and Morgan Stanley. That year, the Crown Estate had announced successful bidders for what was the world’s first commercial wave and tidal leasing round, for 10 other sites in the Pentland Firth and Orkney waters.

The 1.2GW power generation proposed by developers comprised one half wave power and one half tidal current power. With the addition of the Inner Sound, the 11 Pentland Firth and Orkney waters projects have a total potential power capacity of 1.6GW. The original preferred bidder for the Inner Sound withdrew from the lease competition at a late stage, resulting in a re-tender of the lease.

The Inner Sound was “one of the most contested areas” in the leasing round, according to the Crown Estate.

Funds for MeyGen Phase 1A are £51.3m from the Scottish government through Scottish Enterprise and Highlands and Islands Enterprise (HIE), the UK Department of Energy and Climate Change (DECC), the Crown Estate and Atlantis Resources. Of the total package, £17.5m is in the form of senior project finance funding, comprising a £7.5m project finance debt facility from Scottish Enterprise’s Renewable Energy Investment Fund (REIF) administered by the Scottish Investment Bank, and £10m of funding from the Crown Estate.

A further £13.3m is provided in the form of direct grants to MeyGen, made up of £10m from the DECC Marine Energy Array Demonstrator scheme and £3.3m from HIE. The balance of £20.5m is provided as cash equity investment into Tidal Power Scotland Holdings, the holding company of MeyGen, which has been established to invest in MeyGen and other tidal power projects in Scotland. Of this equity investment, £10.8m is from Atlantis, with REIF providing £9.7m equity. After equity funding, Atlantis’s holding in MeyGen will be 86.5 per cent and Scottish Enterprise’s holding, as a new shareholder, 13.5 per cent.

Andritz’s turbines are designed to generate electrical energy from water currents with a speed above one metre per second and depths between 35m and 100m. Some of the turbine parts can move independently to make best use of the currents, and the turbine shape is streamlined to work more easily in the water.

Although ocean currents move slowly relative to typical wind speeds, they can be used to produce a great deal of energy because seawater is about 800 times more dense than air. The tidal water force is also far more predictable than wind.

Yet in storm conditions, this force can cause problems. Even 20m below the surface, some of the large waves that storms bring can be powerful enough to break a turbine.

The turbines have to be designed to withstand not only these storm forces, but also the chance that they might hit when the turbine has not positioned itself at exactly the right angle to the current. This means they have to be able to stand up to extreme tidal forces.

The Inner Sound of Pentland Firth is recognised as one of the most challenging and highly active sites of tidal flow, with high wave-frequency; it requires careful engineering, manufacturing and assembly to ensure that the technology deployed is able to operate and perform within its environs.

The Andritz turbines, built at Ravensburg in Germany, are designed to withstand a wave with a return period of 50 years and a height of 16m. The average power generation per turbine is expected to be 4.4GWh per year.

In 2011, Andritz tested a 1MW tidal turbine at EMEC’s tidal test site, with first energy delivered to the grid in 2012. Its turbines are based on the smaller HS300 turbine, which was installed in Norway as the first tidal power turbine with a permanent connection to the public grid in 2004.

The Atlantis Resources AR1500 1.5MW turbine is designed to withstand the extreme environmental conditions expected in the Pentland Firth and its other planned location in the Bay of Fundy in Canada. Designed by Lockheed Martin, the turbine also has parts that move independently and is designed for long-term use with minimum maintenance.

Atlantis first used its AR1000 tidal turbine at EMEC’s Fall of Warness tidal test site in summer 2011. Prototype testing at EMEC paved the way for the AR1500 to be used in the MeyGen project.

Work on the mainland at Ness of Quoys, next to the Inner Sound, has been completed and includes a power-conversion building that houses a specialised electrical hub, which has been officially handed over to Scottish Hydro Electric Power Distribution (SHEPD). SHEPD installed the electrical equipment needed to allow the project to export electricity to the grid, which is planned for early 2017.

Connection of the MeyGen project to the grid is a major technical milestone for Atlantis and the tidal stream industry. Atlantis said the MeyGen scheme is now the world’s largest energised grid connection of any commercial tidal stream project.

Offshore installation is managed by James Fisher Marine Services and includes the tidal turbines, support structures, ballast and subsea cables. The firm has been given preferred supplier status for a five-year operations and maintenance period for MeyGen Phase 1A. Its specialised HF4 vessel, which will be used for the work, is designed to find and maintain its position in fierce sea conditions up to 10 knots.

The first phase - 86 turbines generating 86MW - could evolve into a second phase producing up to 398MW, depending on how the turbines interact with each other under the water, as well as on securing permission to supply the electricity to the grid.

Phase 1A consists of three Andritz turbines and one Atlantis turbine. The next phase, 1B, is a further 6MW of power from four more 1.5MW turbines. Phase 1B is in the final planning stage with all necessary consents and grid connections in place. Atlantis aims for phase 1B to be commissioned in the last quarter of 2017.

In late September, Scotland’s First Minister Nicola Sturgeon officially unveiled the project at Nigg Energy Park, near Inverness, where the turbines are being joined to their foundations before transport to the north coast. She said: “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.

“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.

“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.

“Yet it is absolutely vital that the UK Government honours 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.”

Atlantis’ MeyGen and Sound of Islay projects are expected to generate around £275m for Scotland’s economy.

Tim Cornelius, chief executive of Atlantis Resources and MeyGen director, said: “Today marks a historic milestone not just for Atlantis and our project partners, but for the entire global tidal power industry. 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.”

He continued: “MeyGen is one of the most exciting and innovative renewable energy developments in the world, making Atlantis the first independent power producer from a tidal array.”

MeyGen has also announced a grid-sharing deal with Lochend Wind Energy, which can use spare capacity in the new MeyGen grid connection when it’s not needed for tidal power. The four-turbine wind farm sits near Gills Bay and adds to the renewable power produced in the area.

The grid connection that MeyGen currently has is limited, and there is no extra capacity until wider grid upgrades are completed over the next few years. However, because of the predictable and cyclical nature of tidal generation, there is an opportunity for other power projects to use the grid at times when MeyGen is not generating maximum power.

This grid-sharing deal is believed to be the first combination of a wind and tidal project of its kind. According to Atlantis, the agreement shows the potential for using existing grid connections by matching different electricity generation patterns.

Cornelius says: “We believe this to be a world first, and to show that the predictability of generation from the tides can also benefit other forms of renewable energy by allowing those generators to accurately forecast and access spare grid capacity.

“Tidal power makes for more efficient grid use and management and we are delighted to have been able to assist a local wind farm in getting connected.”

As part of its work to transmit electricity from the MeyGen project, SHEPD installed a new underground cable at the power conversion building and connected it to a key substation 16km away. MeyGen also has an additional connection to the high-voltage grid with Scottish Hydro Electric Transmission Ltd. (SHETL). This connection will provide enough grid capacity to cover a large part of the remainder of the MeyGen project.

To make use of the boom in renewable energy in the north of Scotland, grid operator SHETL is planning major upgrades in the area that include new power lines and a new substation near the MeyGen site.

These major upgrades, part of the SHETL Caithness-Moray grid reinforcements, are needed to allow the north of Scotland’s renewable energy boom to be beneficial not only in the local area, but to grids throughout Scotland and beyond.

The upgrades are so extensive that they represent the biggest investment in the Scottish Highland grid since the heyday of hydro development in the mid-20th century.

The unassuming Caithness village of Spittal is to become the northern hub of a £1.1bn high-voltage underground and subsea cable system capable of transporting a massive 1,200MW of electricity to a large substation in Moray. Work to install the 113km subsea cable is due to start in 2017.

Tony Scott, project director, Transmission Programmes East, said: “Caithness-Moray represents the largest investment in the electricity network in the north of Scotland since hydro development in the 1950s. Once complete, it will significantly reinforce the country’s transmission network and aid our transition to a low-carbon economy.”

The Caithness-Moray project is scheduled for completion in 2018.

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