Off the southern coast of Australia, a new effort is under way to capture the energy embedded in ocean swells. Special buoys will be used to convert the sea's waves into a maximum of 62.5 megawatts (MW), or enough to power 10,000 homes, according to an announcement this week from project partners Lockheed Martin and Victorian Wave Partners Ltd. Touted as the world's largest wave energy project, the Australia buoys are still just a drop in the bucket for wave power potential.
The constantly churning oceans that cover most of the Earth offer an inexhaustible source of clean energy. The amount of recoverable energy embedded along the continental shelf of the United States, for example, amounts to almost a third of all the electricity the country uses in one year, according to estimates from the Electric Power Research Institute,
"It's emission-free power and it's located close to where most of the population lives," said Sean O'Neill, president of the Gaithersburg, M-based Ocean Renewable Energy Coalition (OREC).
But the process of harnessing all of that energy, still in its infancy, isn't an easy one. "At this stage, putting equipment in the sea and getting it to work reliably, consistently, during severe storms, is a huge challenge," said Aquamarine Power CEO Martin McAdam. "If anyone tells you otherwise, they haven't done it yet." (See related pictures: "Immense, Elusive Energy in the Forces of Nature.")
Precisely how such a feat could take shape is an open question still to be answered, in the most literal sense: What designs and mechanisms will work best? Beyond "PowerBuoys" in Australia, wave energy proponents are now testing diverse and intriguing ideas for power generators that can even pull double duty for desalination, maritime surveillance, and other exciting applications.
Slithering Scottish "Sea Snakes"
Scotland-based Pelamis Wave Power produces an offshore wave energy converter that looks like a colorful sea snake—and is in fact named for the species Pelamis platurus. But this snake's bite lies in its ability to produce power. (See related pictures: "Nature Yields New Ideas for Energy and Efficiency.")
Anchored 1.25 to 6.2 miles (2 to 10 kilometers) from shore, the Pelamis can naturally spin on a chain to face wave direction like a flag changes orientation on a flagpole. Five floating tube sections are linked by universal joints that flex in two different directions as waves roll down the machine's serpentine length. Each joint houses cylinders that resist the wave-driven movements and pump hydraulic fluid to power onboard generators, sending electricity to shore via underwater cables. The Pelamis can handle dangerous storm swells much like a surfer paddling out to a favorite break: When big waves roll in, it simply passes through and under them.
Pelamis has produced six full-scale machines so far, each rated at 750 kW. Over the past 15 years they have logged more than 10,000 hours at sea while connected to real electrical grids, notably at the European Marine Energy Centre (EMEC), off the west coast of the Orkney mainland.
The company plans to debut its technology commercially with Farr Point Wave Farm, a ten-machine project off the Sutherland coast that is set to produce power by 2017. Pelamis has several other plans currently on the drawing board.
The UK energy supplier E. ON and ScottishPower Renewables each own a Pelamis machine currently in sea testing at the EMEC. Each company has ambitions to develop a wave farm, E.ON's in waters north of EMEC and Scottish Power Renewables' off Marwick Head in Orkney. These operations could link as many as 66 machines each and produce 50MW of power at each location. Pelamis has also partnered with Vattenfall to develop a 10MW wave farm, using up to 14 machines, off the Shetland Islands and is planning another 10MW facility off the west coast of Lewis in the Outer Hebrides. And in Aguçadoura, Portugal, past site of a three-machine Pelamis farm, Companhia da Energia Oceânica SA (CEO) might install as many as 26 machines with a target capacity of 20MW.
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