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Wave and tidal power growing slowly, steadily

Proponents of wave and tidal power have compared the state of this area of the renewable energy sector with the early days of wind power. The technology has great potential but still must prove itself before it can be widely deployed.

Wave energy technology uses the movement of ocean waves to generate electricity from turbines. Wave power differs from tidal power, which is based on extracting energy from tidal movements and the water currents that accompany their rise and fall.

Experts estimate tidal energy’s advantage lies in its predictability. Wave energy could be more abundant than tidal energy while still being less intermittent than wind or solar power.

Conditions along coastlines or on the ocean surface, however, can be hard on wave and tidal installations. Generation assets must be built with operational hazards such as crashing waves, corrosive salt water and other dangers in mind.

Potential
According to the European Marine Energy Centre (EMEC) at Scotland’s Orkney Islands, the best wave climates—with yearly average power levels between 20-70 kW/m of wave front or higher—are where strong storms occur. The extent to which this will prove practical to harness, however, will depend upon the successful development of near-shore and deep-water technologies.

The most energetic wave resources are along the coasts of the Americas, Europe, Southern Africa, Australia and New Zealand.

The EMEC is one of the world’s foremost proving grounds for wave and tidal technologies and has collected more than 100 wave energy concepts, with many still at the research and development stage.

Wave and tidal technologies can be three to four times more expensive than wind power per megawatt, so many installations were developed and supported with government financial backing.

The United Kingdom remains one of the largest state sponsors of wave and tidal power. The U.K. government granted $3.8 million from an $83 million pot created under the Marine Renewables Deployment Fund, which began in 2004.

More than $33 million has been earmarked for a new Marine Renewables Proving Fund with a further $15.7 million going to develop a Wave Hub off Cornwall and $13.2 million for the EMEC.

Setbacks
Scottish firm Pelamis Wave Power, which changed its name in 2007 from Ocean Power Delivery, launched a project in Portugal called the Agucadoura wave farm. The project consisted of three of the company’s P1-A Marine Energy Converters.

In September 2008, the company installed the energy converters 3 miles off the coast of northern Portugal. In mid-November 2008, all units were removed from the ocean when leaks were discovered in the buoyancy tanks.

Compounding Agucadoura’s woes, Pelamis couldn’t get the financial support to re-launch the units after the technical problems were solved. Following the global economic downturn, sponsor Babcock & Brown withdrew from the project.

By March 2009, Agucadoura was taken offline indefinitely with about $13 million spent on the project.

In February, Pelamis won an order from British renewable company E.ON for the next generation of Pelamis Marine Energy Converters, which the company calls the P-2. The machine will be built at PWP’s facility at Leith Docks, Edinburgh, and tested at the EMEC at Scotland’s Orkney Islands.

Projects
Despite the cancelation and scaling back of some projects following the economic crisis, there are still wave and tidal projects taking shape.

In November, Ocean Power Technologies (OPT) won a $61 million grant from the Australian government for a utility-scale project. The company said work on the 19-MW project is expected to begin by the second quarter of 2010. Further funding will be needed to complete the project, the company said.

OPT’s PowerBuoy floats freely with the rising and falling of offshore waves. The resulting motion is converted with a power take-off to drive a generator. The generated power is transmitted ashore via an underwater power cable.

A 10-MW OPT power station would occupy about 30 acres of ocean space. The technology is scalable up to 100 MW, the company said.

In 2008, OPT won a $2-million award from the U.S. Department of Energy (DOE) in support of OPT’s wave power project in Reedsport, Ore. Major portions of the PB150 PowerBuoy will be fabricated and integrated in Oregon. This was the first award for the building of ocean wave energy systems by the DOE, according to the company.

OPT also has worked with the U.S. Navy on its Deep Water Acoustic Distribution System program. The company is supplying its PowerBuoy technology to the project, which is designed to demonstrate the potential of powering sensor networks over wide areas of the ocean.

Irish tidal energy company OpenHydro won a grant of nearly $3 million in October from Sustainable Energy Ireland’s Ocean Energy Prototype Research and Development Programme. The grant will be used to design and develop a 16-meter Open Center Turbine, Subsea Base and Installation Barge.

The turbine is mounted on the seabed below the ocean waves. Invisible from the surface and silent, the turbines generate up to 1 MW of electricity.

Also in 2009, OpenHydro paired with Nova Scotia Power to unveil a 1-MW tidal turbine to be deployed in the Bay of Fundy. The project will serve as part of Nova Scotia’s tidal power test facility. The Open Center Turbine was manufactured in Ireland by OpenHydro. The turbine will rest directly on the ocean floor using a subsea gravity base fabricated by Cherubini Metal Works.

Oysters and Limpets
Aquamarine Power is a wave energy company whose Oyster Wave Energy Converter has been tested and deployed at the New and Renewable Energy Centre near Newcastle, England.

Oyster is an onshore, commercial-scale pumping cylinder that can deliver more than 170 kW of electricity per unit. A full-scale Oyster uses two pumping cylinders and can deliver in excess of its modeled output of 350 kW.

Oyster is designed to capture the energy found in near-shore waves up to depths of 10 to 12 meters. The device combines new technologies with a hydroelectric power generation system. A commercial farm of just Oyster devices (15 MW) could provide clean renewable energy to 9,000 homes. Aquamarine tested the Oyster in summer 2009 at the EMEC. The company also has an agreement with Airtricity, the renewable energy division of Scottish and Southern Energy, to develop sites capable of hosting 1,000 MW of marine energy by 2020 suitable for deployment of Oyster.

Wavegen, a unit of Voith Hydro with its headquarters in Inverness, Scotland, produces a shoreline wave energy conversion unit called Limpet. The technology is in use and has been connected to Scotland’s power grid since 2000.

The technology used is called an oscillating water column. Ocean waves move air in and out of chambers in a breakwater, which in turn drives Wavegen’s turbine, known as the Wells turbine, to generate electricity.

The 18.5-kW modules are meant for use in breakwaters, coastal defenses, land reclamation schemes and harbor walls.

Wavegen teamed up with Npower Renewables in 2006 to plan a wave power plant for the Scottish island Lewis. The Siadar Wave Energy Project earned the approval of the Scottish government in January.

The project will harness power from the Atlantic waves in Siadar Bay to generate up to 4 MW of electricity. The energy produced each year could supply the average annual electricity needs of about 1,500 homes in the Western Isles.

This article was reprinted from Electric Light and Power's December 2009 issue

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