Europe’s largest tidal power project has begun in northern Scotland, with the first of its marine turbines starting to produce electricity at the end of 2016.
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Phase 1A of the MeyGen project, involves the installation of four underwater turbines just north of the Scottish mainland during September. They will have a generating capacity of 6MW – enough energy to power more than 3,500 homes. It is the world’s first commercially funded tidal array and is on track to deliver to the grid later this year.
The four 1,000-plus tonne turbine structures are the first of 269 planned for the MeyGen site over the next decade. It will eventually power 175,000 homes.
Installation of the turbines comes as the tidal power industry moves from testing and prototypes to the first arrays of full-scale devices.
And as the fundamentals behind tidal power become better known, this form of power generation is thought more likely to become a viable option for bulk renewable energy. But questions about the extent of UK government’s financial support remain.
Edinburgh based MeyGen is 100% owned by Atlantis Resources, which began testing turbine prototypes in Australia in around 2002. It has since expanded overseas and has work in China, Canada and Scotland.
The MeyGen project kicked off with official testing at the European Marine Energy Centre at Stromness, Scotland in 2010, the same year development rights for the project were granted by the Crown Estate.
September 2014 marked financial close for the £51.8M Phase 1A contracts, partly thanks to funding from from the Department of Energy & Climate Change and from development agencies Scottish Enterprise and the Highlands and Islands Enterprise. The UK government has provided £10M in grants to the project from its Marine Energy Array Demonstrator scheme.
This led to the unveiling of a fully assembled AR1500 Atlantis tidal turbine, developed with US weapons manufacturer Lockheed Martin, at Nigg Energy, 30km north of Inverness.
It is an impressive sight, with a rotor diameter of 18m. A yaw mechanism can turn the turbine through 180⁰ when the tide changes direction. The nacelles themselves contain a generator and gearbox, but the power conditioning equipment is housed onshore.
Atlantis claims that its turbine can generate 1.5MW at water flows of 3m/s, with the tides driving the relatively lightweight composite turbine blades that weigh about 3.5t each. Steel blades of other turbines can weigh about 7t. To gather the maximum amount of energy possible, the angle of the blades on the AR1500 can be altered, and the turbine can pivot 360º on its foundation to align with water flow direction.
The turbines have a “wet mate” capability for making electrical connections underwater. This was developed especially for the MeyGen project, using technology developed by Siemens and proven in the oil and gas industry. But if maintenance is required, it is done out of water.
As part of Phase 1A, three more turbines made by Austria-based Andritz Hydro Hammerfest will be installed. Andritz developed the first ever tidal current turbine with a permanent connection to a public grid, in Norwegian waters in 2004.
Each of the turbines has a 25 year design life. They are equipped with hundreds of sensors. “They’re measuring things like stresses in the blades, rotor deflection – all the stuff that leads to early preventative maintenance,” says Atlantis technology and turbine service director Drew Blaxland. Part of this rationale is to help the industry hone in on an optimal turbine design. “If you go back five to 10 years, everyone’s turbines were wacky and different,” says Blaxland.
At the Inner Sound in the Pentland Firth just south of Stroma Island, the speed at which the North Sea empties into the Atlantic Ocean is clearly visible, even from the surface. The “tidal races” – swirling currents around land masses – are known hazards for sailors.
It is for this reason that the strait was chosen as the ideal site, after tidal flow modelling in 2011. Maximum current speeds are up to 5m/s. It is also the deepest section of the UK’s territorial waters – up to 323m.
The strait is 3.6km at its widest, 2.5km at its narrowest and currents are strong enough for there to be no need for additional earthworks to support the scheme, unlike tidal lagoon power site, mooted for Swansea in Wales.
The turbulent tides in Pentland Firth make lowering the 1,000t-plus structures into the water more difficult. Installation must occur when the tide is weak and changing. Ideally this would also be during neap tides, which occur twice a month when the difference between high and low tides is the least.
The assembled turbine-foundation structures left the dock in Nigg on Cromarty Firth on a jack-up vessel. This travelled 125km to the site, taking 12 hours.
To the lay observer, these tidal power turbines look like wind turbines, but they are vastly different when considering the dimensions and forces at play. Water is 784 times more dense than air, so the turbines move more slowly, but with more power. The blades turn about seven revolutions per minute, as opposed to those of wind turbines which rotate at about 15 to 20 revolutions/min.
The installation team – many using skills acquired from the oil and gas industries – took only 40 minutes to lower the turbine structure and weigh it down with ballast.
Wind speed was a major factor – it had to be less than 17.7km/h. The mean wind speeds for northern Scotland lie between 118.4km/h to 36.8km/h, depending on the month.
As soon as you land it [on the seabed], you connect electrically, and you’re ready to go. Back in the prototyping days, that took a month.
Atlantis director of technology and turbine service Drew Blaxland
Once the turbine structure was in position, 1200t of ballast “blocks” are placed over the turbine structure’s “feet”. These comprise six 200t blocks, two blocks per leg. In total, the installation involves seven lifts.
Blaxland says the time involved for installation, as well as design and manufacture, has been slashed since the prototype days. “As soon as you land it [on the seabed], you connect electrically, and you’re ready to go. Back in the prototyping days, that took a month.”
While the tidal energy sector is in its early days, it has advantages that could see it grow faster than other renewables. Tidal energy production is more predictable than solar or wind energy, although not as consistent or constant as nuclear or gas power.
Attracting much buzz is the mooted £1.3bn Swansea tidal lagoon, which would be a prototype for a £15bn programme of investment in full-size lagoons for west Cumbria, Bridgwater Bay, Colwyn Bay, Newport and Cardiff. These involve installing underwater turbines in a seawall, rather than positioning them on the seabed. Depending on what reports you read, tidal power could eventually meet 10% to 20% of the UK’s electricity demand. A review of this suite of proposed lagoons started in February, focusing primarily on whether they would provide value for money.
The Department for Energy and Climate Change estimates that the UK alone has around 50% of Europe’s tidal energy resource and of that Scotland accounts for around 30%. “If we don’t get a move on, we’re ceding ground to others around the world, like we did with previous technologies such as wind,” says Scotland’s business, innovation and energy minister Paul Wheelhouse. “Everything I’m seeing is indicating we’ll need more power, at lower cost, for energy security, through renewables rather than nuclear.”
Scottish first minister Nicola Sturgeon, has urged Westminister to show more support for renewables. “The next phase is we need to see the promises made by Westminster now delivered. So we can get on to delivering the next phases of this amazing project,” she says.
But there are constraints on manufacturing and construction. It takes about 21 months to create the generators, the main turbine component at a factory in Bristol. Phase 1B is only due to start deploying new turbines in 2018. “The foundations take nine to 10 months to build, and there will be different foundations moving forward. We’ll start buying generators, gearboxes, cables, the front end procurement part of the project, from 1 January, 2017,” says Blaxland.
When up and running, the project will receive operating funds under the UK government’s Contract for Difference (CfD) up to 2021. Under the CfD, energy generators are paid the difference between the “strike price” – an agreed price for electricity reflecting the cost of investing in a low carbon technology – and the “reference price” – a measure of the average market price for electricity in the British market.
Currently, the strike price set for tidal power is £305/MWh, although this is expected to fall. Atlantis says it “is committed to steady price degression… through growth and the consequent benefits of economies of scale”. A report by the Energy Technologies Institute (ETI) suggests that costs will come down to £150/MWh in 2020 to £83/MWh in 2030 to £63/MWh in 2050.
Atlantis chief executive Tim Cornelius has called on the government to stand by its 2014 policy commitment to prioritise subsidies for tidal power schemes with capacities of up to 100MW. “The Danish government made a similar visionary commitment in the early 1980s, securing the on and offshore wind industries which now employ 28,000 workers in Denmark and generate £5bn in exports. The UK could replicate the successes the Danish industry has achieved but only with early support through the CfD – without it, the opportunities will be lost.”
After the Brexit vote, funding for energy projects from the European Investment Bank might be at risk. EIB investments in the UK economy came to €7.8bn (£6.95bn) in 2015, 24% of which was on energy projects.
But Cornelius is optimistic.
“The EIB is only one source of finance. But if it’s not available there will be other sources. The fact of the matter is, there is a lot of money washing around at the moment, and a lot of people want to be involved in high-quality infrastructure projects.”
Rather than look at other countries, such as France, Japan, Canada, Korea and China, as competitors, Cornelius believes Scotland’s renewables sector has strong export potential. “Scotland leads the way with setting policy to encourage investment. We almost get a delegation a month coming across to replicate the way Scotland has done its infrastructure.”
Roy MacGregor is chairman of Global Energy Group, the operator of the renewables assembly site and dock at Nigg. He says it all feels a little bit like the North Sea’s first oil and gas boom.
“I was involved in starting a local workforce in an industry [oil and gas] that was alien to Scotland, but over the 40-odd years became the envy of the world,” he says.
We do need renewables, not just for this generation but for tomorrow’s generation.
Global Energy Group chairman Roy MacGregor
“In many ways, as we start another journey with renewables, it’s like just putting the clock back for me, and looking forward to the prosperity that this industry will give another generation.”
He says that at peak the Nigg yard employed 5,500 people, in early 2016 there were 3,000. On the day New Civil Engineer visited the site, there were significantly less.
“We do need renewables, not just for this generation but for tomorrow’s generation,” says MacGregor.
Phase 1C with a capacity of 74MW is due to be commissioned in 2018, and is currently at the advanced development stage, with consent and grid connection secured. Phase 2 will have a capacity of 312MW. It is under development, due for commission in 2021.