The tide is high

8th April 2015


Marine current turbines fmt

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Martin Broderick

Marine energy is a predictable source of clean power. Julian Jackson reports on the state of the industry in the UK

At the start of March, an environmental impact assessment scoping report was submitted for a tidal lagoon between Cardiff and Newport. The development is likely to have an installed capacity of between 1,800MW and 2,800MW, which is enough low-carbon electricity to power every home in Wales throughout its 120-year life, according to project leader Tidal Lagoon Power (TLP). The firm also expects to receive planning permission in June for a tidal lagoon in Swansea Bay (see panel, below) and is planning four more across the UK.

TLP is one reason why the UK is leading the world in developing technology to generate marine energy. As well as tidal lagoons, which are akin to conventional hydropower from dams, the marine energy sector also includes wave power and underwater tidal stream turbines. However, projects are at the “in-water testing” or demonstration of prototypes stage. None has yet made the jump to a commercial-scale array.

Choppy waters

The UK is well placed to lead in this sunrise industry. In its marine energy policy paper, Decc stated: “Wave and tidal stream energy has the potential to meet up to 20% of the UK’s current electricity demand, representing a 30GW–50GW of installed capacity.” The six lagoons planned by TLP would be enough to meet 8% of the UK’s total electricity requirement for more than 100 years, claims the company. This potential source of power for the UK is there because the seas around the British Isles are powerful and the tides are predictable. Martin Wright, chair of both Mojo Maritime, which provides services for marine renewables, and the Renewable Energy Association, says: “Tidal power is an enormous opportunity, given its high-energy capture.”

However, the UK industry is at a critical point in its development after being dealt a series of blows, starting with the financial crash of 2008, which reduced investment and made commercial investors risk-averse. This led to Pelamis Wave Power, the Edinburgh company behind the wave energy converters that it had been testing at the European Marine Energy Centre (EMEC), going into administration, and Siemens pulling out of the Strangford Lough twin turbine in Northern Ireland and the Skerries development off Anglesey.

Nonetheless, the UK’s offshore energy industry has abundant skills and plentiful equipment that could be applied in new ways. EMEC (p.40) is based in Orkney and is the world’s foremost offshore testing laboratory for marine energy devices and ancillary equipment, such as foundations, hubs, cables, substations and grid connections. Most casual observers fixate on the turbines, but it is installation, reliability and maintenance in a hostile environment that can be the limiting factors. Unless the devices are very reliable, the costs of raising one from the seabed and replacing a relatively low-cost part could be more than £100,000.

The UK government has pledged to support the industry through contracts for difference (CfD), which have replaced renewables obligation certificates (ROCs) as the main support scheme for renewable energy projects, although no marine-energy projects received support in the first CfDs announced in February. The government recognises that the development of wave and tidal power is still in its infancy, and this is reflected in the CfD “strike price” (amount the generator receives) for these technologies. In December 2013, Decc said the strike price for wave and tidal stream technologies would be £305 per MWh – far more than other renewables would receive – and that 100MW of revenue support tidal generation capacity would be ring-fenced until 2019.

Technical glitches

At the 8th International Tidal Energy summit late last year, there was an air of pessimism, particularly at the difficulty in attracting private investment to move to full-scale commercial arrays. The most significant project at the moment is Meygen in the Pentland Firth, at the north eastern tip of Scotland. Four 1.5MW turbines, using designs by both the Atlantis Resources Corporation and Andritz Hydro Hammerfest, are set to be installed there in 2016 to test which works most effectively.

“The Pentland Firth is one of the best sites in the UK to prove the technology,” says Dan Pearson, chief executive at Meygen. “We hope to deploy 15–16 turbines in the next phase, and grow the project to reach 20–30 turbines in the array in the 2020s.”

Peter Fraenkel, a co-founder of Marine Current Turbines (MCT) – the firm behind the Strangford Lough project – and a visiting professor at Edinburgh University, believes that many proposed turbine fixtures are too small. At the summit, he argued that, because overhead costs are fixed, bigger arrays make more economic sense. Four turbines in one array have the same fixed costs but quadruple the power, which equals more energy and profit for the operators, he said.

MCT, which was acquired by Siemens in early 2012, installed its SeaGen S1.2MW device in Strangford Lough in 2008. It was the first marine renewable energy project to be accredited by Ofgem as a commercial power station. It has generated more than 10GWh, and can deliver up to 20MWh of electrical energy a day or 6,000MWh a year. This is about the rate of energy capture of a 2.4MW wind turbine.

However, Siemens downgraded its involvement in Strangford Lough last year and wants to sell MCT. “It’s because it’s taking too long for the technology to become commercial, both in terms of the market and the supply chain,” a Siemens spokesperson said. The difficulties of gaining a return on its investment, even with what is clearly a successful design, seemed to be what deterred the German engineering firm from continuing its support.

The supply chain problem is part of the “chicken and egg” nature of the sector: there is no point in investing in docks, specialised vessels, grid connections, and training a workforce if there are no projects for them to work on. This is the dilemma facing Mojo Maritime with its advanced HF4 DP vessel. This is designed to support the most difficult offshore operations. It would cost Mojo £25 million to build but demand for it does not justify that level of investment. But the industry will need it, or something similar, to put turbines in the most powerful currents, where the greatest energy is generated.

Environmental considerations apply to any new technology. The Strangford Lough operating licence required MCT to establish an environmental monitoring plan (EMP) and a number of mitigation measures. Data collection began pre-installation in April 2005 and formed the basis of an environmental baseline report against which to compare all future monitoring during installation, commissioning and decommissioning.

The monitoring focused on three areas: marine mammals, such as seals and harbour porpoises; the effects on the seabed or benthic zone, where many marine organisms live; and tidal flow and energy. The final report, published in 2011, concluded: “The findings of the EMP provide confidence that SeaGen can continue to operate with no likely significant impacts on the marine environment in Strangford Lough.” This suggests that marine arrays are safe to operate and do not have undue effects on the ecosystem.

Overseas competition

Some nations view tidal power positively. In France, GDF Suez and EDF have been awarded €120 million in government grants to develop and test tidal farms off the Cherbourg peninsula in Raz-Blanchard, which has the strongest tidal current in Europe. This area also has the advantages of good grid connections. In Canada, OpenHydro is working on an array in the biggest tidal range in the world, the Bay of Fundy between New Brunswick and Nova Scotia. It plans to install two 16m turbines totalling 4MW later this year. The company says the project has the potential to be one of the world’s first multi-megawatt arrays of interconnected tidal turbines.

These developments leave some wondering whether the UK will drop the ball and relinquish its lead in the sector, as happened with offshore wind, where Germany and Denmark became the major players and now enjoy the consequent economic advantages. Overall, the UK tidal sector has been through rough waters, but the 100MW of ring-fenced finance at £305 per MW provides the industry with a degree of stability, enabling firms to prove their designs and collaborate on developing the infrastructure, grid connections and supply chain to move on to commercial operations. Globally more projects are planned, opening up export markets for UK technologies, operators and skilled workers.

The UK lead could easily be eroded by more proactive nations, however. Some industry commentators feel it is important to get several more projects in the water and generating electricity within the next 18 months to keep up the momentum. Private investors like to see several years of dependable electricity generation before they will fund the move to bigger, commercial projects.

Julian Jackson is a writer on the environment.


Testing facilities

Established in 2003, the European Marine Energy Centre (EMEC) in Orkney is the world’s foremost wave and tidal testing site. The location is an ideal base for testing, with its strong tidal currents, grid connection, sheltered harbour facilities, and maritime and environmental expertise shared by the local community. EMEC’s facilities have attracted marine energy developers from all over the world.

Currently there are four turbines in the water under test in the centre’s main grid-connected site. EMEC also boasts smaller areas for non-grid-connected sites. Eileen Linklater, client relationship and marketing manager at EMEC, says: “Often it is too big a leap to go from tank testing to the grid-connected site, which has strong tides. So some companies opt for an intermediate stage at our non-grid connected sites before they are ready for the main site.”

Industry support services that EMEC has tested include cables and cable-laying, and the use of local vessels and labour to install equipment at sea. “The local labour force is highly skilled and experienced in offshore operations,” says Linklater. “We are also testing cable laying systems and electrical connections. EMEC is pioneering a standardised data pod, which can be used to capture data to prove that the turbines are working as expected.”

The development of the pod is because EMEC’s remit includes helping to draw up international standards and verification systems for marine energy equipment. The centre is a participant in the EU Environmental Technology Verification (ETV) scheme, which provides independent confirmation that installations are performing to specification.

EMEC has ambitious plans for the future. It is expanding the number of testing sites with two new ones on the west coast of Scotland. The centre also intends to scale up arrays in the water, and to continue its testing and verification operations, as well as monitoring cabling and data collection systems. Linklater
believes that cable installation and maintenance is an area that has so far been neglected.

As well as EMEC, there is another UK testing site called Wave Hub off Hayle on the north Cornwall coast. It is grid connected and has berths for four devices to test. FloWave, a unique 25m tank at Edinburgh University, is also used to test marine energy technologies. It can simulate a variety of sea conditions and currents, which is ideal for testing designs without hauling them out to sea. Developers can, in effect, prove the efficacy of their projects before deployment at sea.

Swansea Bay’s tidal lagoon

Power from tidal lagoons is really a variation on a hydropower dam. An area of the sea is cordoned off and the water flows through the turbines to generate electricity. This occurs four times a day at predictable times. This technology is mature, to say the least. La Rance in France has been operating for half a century and has just been licensed for a further 50 years. Mark Shorrock, chief executive of Tidal Lagoon Power (TLP), the company behind the proposed lagoons at Swansea Bay and between Cardiff and Newport, claims that the projects are cost effective on a “massive scale”.

The projected tidal lagoon at Swansea would have a 9.5km breakwater, costing £1 billion, generate 320MW of electricity and have a life expectancy of 120 years. TLP says the lagoon will save more than 236,000 tonnes of carbon each year. The location is ideal because the huge tidal range of more than 10 metres allows a significant amount of power to be generated. Aside from Swansea and Cardiff–Newport, TLP has identified four other sites in the UK with good potential, including at Bridgwater Bay in Somerset and on the west Cumbrian coast, north of Workington.

The Swansea project has received £200 million of equity financing – the second £100 million arriving in February 2015 – and expects to raise a further £800 million by July. If approved it could be generating power by 2022. Decc views tidal lagoon power favourably. The Swansea scheme was included in the national infrastructure plan, published ahead of the chancellor’s last autumn statement.

The chancellor announced in his 2015 budget (p.4) that the government and TLP were negotiating on how much financial support the project will receive. The BBC reports that TLP wants £168 per MWh for its electricity (less for the Cardiff–Newport lagoon). A study published last year by consultancy Poyry predicted an average cost of £111 per MWh for tidal lagoons. According to calculations from Decc in 2013, this is comparable to most electricity generation methods, conventional or renewable, and far better than solar – with the exception of electricity from combined-cycle gas turbines.

TLP has worked with a range of stakeholders on its plans for the Swansea lagoon, including the fishing industry and local watersports enthusiasts. A survey of stakeholders received an 86% approval rating, and contrasts with the criticism the proposed Severn Tidal Barrage received. “Swansea is a template,” says Andy Field, TLP’s head of communications. “It will set up a scalable solution, attract investment and involve the UK government and supply chain. I think it will then lead to a rapid deployment of tidal lagoon power worldwide as the technology is proven.”

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