Harnessing the Tides: Marine Power Update 2009  

Renewable Energy World has an article on the state of play in the ocean energy market - Harnessing the Tides: Marine Power Update 2009

One hundred and forty-one years ago, the relentless sea off Scotland's coast inspired the following observation from native son and author George MacDonald.

"I climbed the heights above the village, and looked abroad over the Atlantic. What a waste of aimless tossing to and fro! Gray mist above, full of falling rain; gray, wrathful waters underneath, foaming and bursting as billow broke upon billow…they burst on the rocks at the end of it, and rushed in shattered spouts and clouds of spray far into the air over their heads. "Will the time ever come," I thought, when man shall be able to store up even this force for his own ends? Who can tell?"

Today, we can certainly say, "Yes, the time will come." The only question remaining is how long it will be before humankind routinely and widely uses electricity generated from the kinetic power of ocean tides, currents and waves.

If one defines "commercial ocean energy" as several tens of megawatts, the world cannot yet boast a commercial ocean energy installation. Indeed, only two installations of either wave, tidal or in-stream current devices are grid-connected and can generate over 1 megawatt (MW) of power. One is Pelamis Wave Power's 2.25-MW Aguçadoura project off of Portugal's northern coast and the other is Bristol-based Marine Current Turbines' (MCT) SeaGen, a US $20-million commercial-scale tidal-energy project under development in Northern Ireland's turbulent Strangford Narrows. In December, SeaGen boasted the first tidal turbine to hit a capacity of 1.2 MW.

(The biggest exception to commercial ocean energy production is the world's longest running tidal power plant, the 240-MW La Rance, in France. But the plant's barrage technology, which traps water behind a dam and releases it at low tide, has fallen out of favor due to its perceived higher environmental impact than underwater turbines. Nova Scotia has also been operating a 20-MW barrage Tidal Generating Station in the tidal-rich Bay of Fundy since 1984.)

The rest of the world's wave, tidal and current installations, some of which have been in the water as far back as the 1990s, are experimental and prototype units ranging in size from 35 kilowatts (kW) to 400 kW. Because these units operate only intermittently and are not typically connected to any grid, it is not possible to determine their total power generation.

Many of these units are prototype demonstration units for the much bigger installations that are under development and that will begin to realize significant exploitation of the world's ocean energy resource. For example, Ocean Power Technologies Inc. will use the 150-kW PowerBuoy it has been testing since the mid-90s as the "workhorse" for the 270-MW, four-site wave energy plant off California and Oregon coasts that it has partnered with Lockheed Martin to develop, says CEO George Taylor.

And Inverness, Scotland-based WaveGen expects to use 40 units of the 100-kw turbine it just installed off the Island of Islay for a 4-MW farm off of Scotland's Isle of Lewis. Meanwhile, Pelamis says if its 750-kw "sea snake" devices, which were installed last year, make it through the winter, it will put 37 more of them in the water, generating 30 MW.

All of the wave, tidal, ocean and river current power around North America that can be practically extracted could together provide 10% of today's electrical consumption in the U.S., says Roger Bedard, ocean energy leader at the Electric Power Research Institute (EPRI) in Palo Alto, CA. He adds that the total water resource could, it is sometimes said, possibly power the world twice over, but a lot of it is out of reach. "Hudson's Bay, off the Arctic Circle, has HUGE tidal power, but it is thousands of miles from where anyone lives. We have HUGE wave resources off Aleutian Islands, but the same problem," he says.

What will be the "magic" year for large-scale ocean energy deployment? Most developers indicate 2011-2012. Trey Taylor, co-founder and president of Verdant Power, which is moving into the commercial development phase of its 7-year-old Roosevelt Island Tidal Energy project, says the firm aims to have "at least 35 MW" in the water by the end of 2011.

Aquamarine Power has signed a Development Agreement with Airtricity, the renewable energy development division of Scottish and Southern Energy (SSE), aimed at developing sites capable of hosting 1,000 megawatts (MW) of various types of marine energy by 2020.

Under the agreement, the two companies will enter into a 50:50 joint venture to develop wave and tidal energy sites in the UK and Republic of Ireland. Work on the development of the first two sites has already started, with plans to roll out further sites over the next three years.