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Tides come in

The use of tidal energy for generating electricity is moving ahead rapidly around the world, and the potential for expansion is significant, with the emphasis being on tidal current turbines, although some tidal barrages are also being developed or planned – for example, various barrage and lagoon scheme are still under consideration for the Severn estuary. A decision on which to go for should emerge later this year.

The global potential is quite large. Trade network Tidal Today’s second annual ‘Tidal Summit’, held in London last November, heard from a speaker from the Fraunhofer Institute for Wind Energy and Energy System Technology (IWES) who relayed some estimates of tidal energy potentials: China: 50 TWh p.a; Ireland: 10 TWh; UK: 31 TWh; France: 10 TWh; Norway: 3 TWh; US: 115 TWh. The big ones, in terms of capacity, included Canada: >40 GW and South Korea: 1000 GW.

In terms of tidal turbine development and deployment, the UK still leads the pack, with Marine Current Turbines’ 1.2 MW Seagen in Strangford Narrows to be followed soon by a 10MW tidal farm off Anglesey – MCT has just got £4.8 m from Siemens, EDF Energy, HighTide and others for the next stage. Meanwhile, the European Marine Energy Centre (EMEC) on Orkney is providing key test facilities for UK devices and systems from overseas. It has the world’s only grid linked tidal test facilities – five open sea births, with 11 kv, 5 MW subsea cables. And, as the Crown Estate noted at the Summit, Scotland has 25% of the available European tidal potential – Pentland Firth and Orkney Waters contain six of the top-10 UK tidal sites. Crown Estates seem to have been taking their time assessing these, but are about to announce site licenses for selected projects. So prospects for the future look good.

One of the leaders of the new projects is Open Hydro’s novel ‘open centre’ rim generator turbine, which was tested at EMEC. There are plans for deployment off Alderney and in the bay of Fundy. Next up, Atlantis Resources Corp, the international marine energy company, is to test its AK-1000 tidal turbine at EMEC this summer. Tidal Today reported that the AK-1000 has been designed specifically for harsh marine environments. It features what are claimed to be the world’s most efficient blades – 18 meters rotor diameter – and has minimal moving parts. It should be capable of generating 1 MW of power in a 2.6 m/s tidal current. The company says that it will award contracts associated with the deployment supporting over 100 UK jobs. The AK-1000 will be its second grid-linked turbine. Its Nereus turbine in San Remo, Australia, first deployed in 2006, still continues to generate power for the grid.

The US is also active in the field. The summit heard updates on Verdant powers seven turbine projects in New York’s East River, and there are several other North American projects, including the Canadian ‘Clean Current’ ducted rotor, which is now being developed in conjunction with Alstom. At the summit it was reported that ‘in September 2006, clean current installed a 3.5 m diameter, 65 kW demonstration unit at race rocks, BC, Canada,’ and that ‘performance met or exceeded expectations’. On-going testing is now being carried out, with a view to installation in the Bay of Fundy.

There’s also a lot happening in South Korea – who seem likely to become the world leader. Developer Voith Hydro noted that tidal range (barrage) projects in planning/execution included Shiwa: 254 MW; Garorim Bay 520 MW; Incheon Bay: 1320 MW, and that the Korean Ministry of Knowledge Economy estimates tidal current potential at 470 MW. Voith are installing 100 MW of its 500–1000 kW propeller type turbine at Jindo, Jeollanamdo Province and there’s also a project involving the UK’s Lunar Energy ducted-rotor system.

But not everyone was quite so positive. RWE npower told the summit that costs and financing were still issues. There was an ‘immature market so commercial costs are not yet apparent’ and ‘utilities won’t loss lead demo projects for uncertain future market – demo projects must promise stand alone economic returns’. There were also ‘inadequate support mechanisms’. And there was a ‘massive offshore wind potential’, whereas tidal ‘has a fair way to go’. Consultants Douglas Westwood evidently felt similarly: they told the summit that it cost about ‘£60 m to take a device through to commercialization’ and felt that the ‘forecast of 41 MW installed capacity by 2013 may be missed’, and that without proper support, tidal might only provide ‘1% of UK power generation capacity by 2030’.

Fortunately, in February the UK government finally got its support system working and has allocated £22 m from its new Marine Renewable Proving Fund (MRPF), to six projects, two wave systems (Osprey and Pelamis) and four tidal current projects – using new turbines from Atlantis, Voith, MCT and Hammerfest Strom UK.

The MRPF is managed by the Carbon Trust, which notes that all of the devices receiving MRPF funding will be deployed in UK waters, and will stimulate supply chain opportunities associated with construction and deployment of these technologies, with over 75% of the funding released through the MRPF going to the UK supply chain.

The MRPF aims to accelerate the development of marine energy devices to the stage when they can qualify for the Government’s existing, but so far unused, £42 m Marine Renewables Deployment Fund (MRDF) support scheme and, ultimately, be deployed on a commercial scale, with support from the Renewables Obligation. MCT’s Seagen has in fact managed to jumped straight to that, after several years of grant aided and independent development, and is now getting 2 ROCs/MWh for its 1.2 MW unit in Strangford Narrows. The new MRPF money means that it, and the other developers, can now get moving on new projects.

In addition to those already mentioned, there is quite a range of projects at the starting gate, or at least under development, with some novel UK designs emerging. Scottish projects are well represented, with for example the Scotrnewables’ floating device and TidalStream Ltd.’s unique tidal turbine platform design – Triton. But Wales is also in the race, with Swanturbines’ Cygnet, developed at Swansea University, and Tidal Energy DeltaStream device, which is to be put through trials at Ramsey Sound, near St Davids.

Humberside is also figuring strongly. For example, following tests on models at the University of Hull, a full-scale prototype of Neptune’s ducted vertical-axis turbine ‘Proteus’ device is being tested in the Humber Estuary at Hull. Pulse Tidal’s hydrofoil device is also under test in the Humber. Its 100 kW test rig currently feeds power to a chemicals company on the banks of the river. Tidal Today reported that it is to receive a grant of €8 m from the EU’s technology research and development fund (Framework Programme 7) to enable the company to begin work immediately on developing its first fully commercial tidal energy generator – a 1 MW unit, to be commissioned in 2012.

Not all of the many new tidal current devices emerging will succeed or get sufficient funding to prove themselves. But there is a mood of pioneering enthusiasm, with developers like Pulse Tidal’s chief executive Bob Smith, being very positive about the future: ‘We have developed an economic way to recover predictable, renewable energy from the tides and are entering a young market predicted to be worth at least £6 bn annually in electricity sales’. He added: ‘The Pulse system is expected to match the cost of offshore wind after only 100 MW has been installed. In the future tidal energy is set to surpass wind as the most economic and predictable source of offshore power.’

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