Tripod Tryout. Wind-turbine support would be 44 m deep. (Image courtesy of Talisman Energy (UK) LTD.)

Among marine-based renewables, two 5-MW wind demonstration generators 23 kilometers off Caithness are probably the most advanced. But a crop of wave and tidal devices is close behind.

For the wind project, Talisman Energy (UK) Ltd., Aberdeen, with a local utility, has ordered generators that will reach 88 meters above water. Supplier REpower Systems AG, Hamburg, got its prototype up to 5 MW last December.

"We are at the early stages of detail design and selection of subsea structure and foundation arrangements," says Peter Coutts, project manager with Amec Oil & Gas Ltd., Aberdeen. Talisman hired Amec in January for detail design and project management.

In April, the team got proposals from fabricators helping in the selection of support structures in 44 m of sea. A jacket is favored, says Coutts, but a tripod is also an option.

With onshore installations, wind will help Scotland meet government targets of renewables generating 18% of electricity by 2010, rising to 40% a decade later. Peak demand is forecast to rise from 6,240 MW last year to 6,472 MW in 2010. The government also sees potential in wave and tidal generation.

To reinforce Scotland’s attraction, regional government bodies put up most of the $9.5-million cost of the European Marine Energy Center. Opened last August on Orkney Isles, EMEC provides four wave-device test beds 2 km offshore in 50 m of water, with power and data links to shore. Tidal-power test beds are due in operation next year.

Among EMEC’s potential customers is Lunar Energy Ltd., which plans a 1-MW tidal demonstrator next year, says chief executive Simon Meade. After at least 12 months of testing "we will move on to developing an array [of devices]," he adds.

The device, developed by Aberdeen-based Rotech Energy Ltd., is based on an underwater horizontal turbine with no gearbox or support piles. Weighing 1,200 tonnes, a 1.5-MW device would be 27 m long with a 21-m-dia inlet leading to a 16-m-dia five-blade turbine. Click here to view diagram

EMEC's first client is Ocean Power Delivery Ltd., Edinburgh, which got its 750-KW Pelamis wave device on site last August. By undulating, the 120-m-long, 3.5-m-dia, 750-tonne device moves hydraulic rams, which pump oil to turn a generator (ENR 4/7/03 p. 17).

Last year, OPD agreed with Amec and Scottish Power to develop a commercial plant off Scotland, says Max Carcas, OPD’s business development director. The team now needs to see details of the U.K. government’s new Marine Renewable Deployment Fund.

The $80-million fund will support precommercial operations of wave and tidal devices. It will cover 25% of a project’s capital cost above that of a same-size combined-cycle gas turbine, up to $9.5 million. A revenue support payment of $190 per MW-hour will also be made over five years.

Developers are unimpressed by the modest, short-term revenue support. "We need every penny we can get," says Simon Gray, a director of AWS Ocean Energy, Alness, England. Commercial financing is through venture capitalists, who are in short supply, he adds.

AWS trialed a 2-MW pilot wave device off Portugal late last year. "The next step is to build a…preproduction model," says Gray. He hopes to install a test device in 2007. Submerged at least 6 m deep, the device includes a fixed lower cylinder and a moveable one above. Magnets and coils convert cyclical motions to electricity. In a 4.75-MW unit, the 12-m-dia upper cylinder would move 11 m.