Three red snakelike devices bobbing in the waves three miles (4.8 kilometers) off the coast of Agucadoura, Portugal, represent the first swell of what developers hope will be a rising tide of wave power projects. Edinburgh-based Pelamis Wave Power, Ltd., (PWP) has since September been working with asset management firm Babcock & Brown, energy provider Energias de Portugal, and Efacec (a Portugese maker of electromechanical devices) on the Agucadoura project. This first phase will cost about $13 million and generate up to 2.25 megawatts. The company hopes to by early next year begin building installing another 25 wave-energy converters to increase the output to 21 megawatts, which is expected to serve the electricity needs of more than 15,000 Portuguese households.

Earth's oceans and rivers, pushed by wind and tugged by the moon and sun, ebb and flow over more than 70 percent of the planet, but only recently have researchers and scientists developed the materials and methods to finally harness some of that kinetic energy. There may not yet be a market for underwater turbines or wave-riding electrical generators designed to use ocean turbulence as a source of renewable energy, but that has not stopped a handful of entrepreneurs from trying to create one.

Although all renewable energy sources—sun, water and wind—suffer from peaks and troughs in productivity, "we consider wave energy to be more predictable than wind," says PWP CEO Phil Metcalf. "You look at the ocean 1,000 miles [1,600 kilometers] out, you'll get a good idea of what to expect over the next 24 to 48 hours. We think it's actually going to be easier to dispatch to the grid."

Pelamis's devices are big red cylindrical tubes, each 426.5 feet (130 meters) long, 13 feet (four meters) in diameter, weighing around 750 tons (635 metric tons), and with a life expectancy of up to 20 years. The tubes are connected by hinges so that they float like a snake in the water. As the tubes' sections rise up and down on the passing waves they tug on the hinges, which are resisted by hydraulic rams that pump high-pressure fluid through hydraulic motors and turn electrical generators to produce electricity. Power derived from the joints on each wave-energy conversion is fed down via a cable to a central undersea export cable, which carries the collective power generated from site to shore.

"Our machine works by reacting against itself," says Max Carcas, Pelamis's business development director. Most other technology developed for harvesting wave power—including Finavera Renewables's AquaBuOY, WaveBob Ltd.'s wave-absorbing buoy and another buoy-mounted generator made by SRI International—absorbs energy from riding the waves as they bob up and down.

Pelamis's tubes work best at a depth of more than 165 feet (50 meters) and roughly 3.7 miles (six kilometers) from the shore, where the waves are strong but a crew can still connect a cable from the tubes to the shore. "Waves lose energy once you get to get to less than half a wavelength depth—typically deep swell waves are 100 to 140 meters (330 to 460 feet) in wavelength—hence why we focus on being out above 50 to 70 meters (165 to 230 feet) of water," Carcas says. The distance off the coastline to get to this depth contour will vary from place to place but typically is two to 15 kilometers (1.2 to 9.3 miles), he adds.

Another approach operates at the bottom of New York City's East River, where in 2006 Verdant Power, Inc., planted six windmill-like turbines—each 16 feet (five meters) in diameter—30 feet (nine meters) below the surface and churning at a peak rate of 32 revolutions per minute to transform strong tidal forces into electricity. Despite a few setbacks—the river's powerful flow damaged the rotors and broke off some of the original fiberglass and steel blades—the company has managed to keep two of the turbines operational, supply electricity to a nearby supermarket and, more recently, attract $8.5 million in funding from sources including the U.S. Department of Energy and the Canadian government to further develop and test its technology.

4 Comments

1. 1. David M. Clemen 05:44 PM 10/20/08

   This article states that the Verdant Power system costs $3600/Kw to install, or approx. three times what regular hydroelectric power costs at $1200/Kw. The article does not state what the Pelamis Wave Power Ltd system costs/Kw.
   First of all, I'm very much in favor of renewable energy, but not at any cost. I think cost is important. Secondly, what is the efficiency of these systems? Efficiency is important because it is directly related to the amount (cost) of the equipment that must be installed to generate a certain amount of electricity. Thirdly, has anyone predicted what the maintenance costs will be in a saltwater environment?

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2. 2. yev 08:14 PM 10/22/08

   Isn`t their more harnestable energy available by farming underwater reserves? Wouldn`t this bring a more economical return?

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3. 3. xjyxjy 07:45 AM 10/23/08

   Right now I think we should focus more on the potential benefits of areas of power generation like those in the article. Initial efforts in any new technology are always expensive and wildly unpredictable - just think of early computers and software! Or cars...
   
   Nowadays we have enormous technical advantages in our knowledge of materials and energy, and an unprecedented capacity for visualizing, designing, and "testing" new machines, and forecasting their performance. Just imagine what Edison, Tesla or Kelvin could have done with all this!
   
   So perhaps it all comes down to marketing, winning public acceptance, and gouging funding out of investors and public coffers.
   
   And the best way to do all this is not to slam current filthy methods of energy production (as necessary as this is!) but to convince millions of people (with more influence than they realize!) of the superiority and benefits of the new technologies. And the certainty of a very good return in terms of money and health in the middle term (say five to fifteen years) and maybe even in the short term (less than five years).
   
   Scientific American has already taken an important step in this direction with its Grand Solar Plan.

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4. 4. yev 08:20 PM 10/25/08

   We have limited ourselves to high tech companies researching solutions for us. Have we considered other alternate technologies to generate power, like solar telsa turbines? Anyone can make one of these and they generate more useable, cheaper, and much easier to produce energy than photovoltaics. Energy that anyone can produce with few simple parts as opposed to a few companies producing expensive solar panels. Any suggestions why researchers research projects few will be able to build?

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