Profit from the power of the tides

Covering more than 70% of the Earth's surface, the ocean is the world's largest untapped source of renewable energy. Sea water 832 times more dense than air is a hugely powerful source of kinetic energy. And unlike, say, solar power, that energy is available at any hour of the day.

However, harnessing the power of the ocean has proved almost comically difficult. Recent experiments have ended in disaster. Last year, for example, a state-of-the-art wave machine sank off the Oregon coast. And after spending millions developing a tidal turbine, Verdant Power suffered a similar fate when New York's East River tore the blades off its 16-foot rotor.

But this hasn't deterred the nascent ocean power industry. Roughly 100 small firms around the world are persevering with their experiments to convert the sea's power to electricity. Many have been encouraged by generous government funding, particularly in Europe. Their efforts divide into chasing three sources of power. First, waves the aim is to harness their up and down motion to generate electricity. Second, tides, where capturing their energy using underwater turbines is the goal. Finally, there's ocean thermal power, generated by temperature differences between the surface and the deep reaches of the ocean.

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The trouble is that none of them have so far come anywhere close to challenging wind or solar power on cost. These are expensive machines to build, notes Brian Baskin in The Wall Street Journal. And the ocean is quick to batter and corrode the machinery and costly undersea cables needed to bring the power onshore. Pelamis, for example, had to raise the equivalent of $77m to launch its floating snakelike tubes. The San Francisco Public Utility Commission put the cost of harnessing the Golden Gate's tides at 85 cents to $1.40 a kilowatt-hour roughly ten times the cost of wind power. By contrast, many solar start-ups need as little as $5 to build a prototype, says Kate Galbraith in The New York Times.

But all this may be about to change. Worldwide venture capital investment in ocean power groups has risen from $8m in 2005 to $82m last year, according to Cleantech Group. Meanwhile, as recent developments in wave-power know-how produces technology that can withstand the brutality of the ocean, big industrials and utilities are piling in.

Last month, Lockheed Martin signed a major engineering agreement with Ocean Power Technologies to develop its PowerBuoy technology. The PowerBuoy bobs up and down on the ocean surface and is tethered to the sea floor with a transmission line. A piston-like structure then moves as the PowerBuoy bobs, driving a generator on the ocean floor, which produces electricity. The operating cost of generating power this way is projected to be just three to four cents/kWh for 100MW plants, according to the company.

So, with the backing of government and big utilities, it may not be long before wave power can compete. We take a closer look at this promising tidal-power pioneer below.

The best bet in the sector

Ocean Power Technologies (Aim: OPT) has received the backing of a number of governments over the last few months. In July, Peter Mandelson announced its participation in a £9.5m wave power grid off the coast of Cornwall. Last month, the firm unveiled an agreement to develop a wave power station in Japan with a consortium that includes oil group Idemitsu Kosan and Mitsui Engineering. That plant will be up and running by 2011, with an initial capacity of ten megawatts, powering 3,000 homes.

The PowerBuoy system has already been deployed in Spain, Australia and the US. The £40m group recently turned a quarterly gross profit of $0.3m and finished the last quarter with total cash and cash equivalents of $80m.

It has a contract order backlog of $6.4m, up 70% on last year. The Cornwall project provided a major boost to its figures. It expects development costs to increase this year as it focuses on improving the PowerBuoy system.

But with the support of the likes of Lockheed Martin, it's on its way to seeing its technology gain serious commercial traction.