New Wave System Claims Huge Energy per Ton Potential

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Illustration: CorPower

Wave energy could become practical using a system that mimics the human heart, say engineers in Sweden.  The system allows a wave power generator to produce five times more energy per tonne of device for one-third of the cost of competing state-of-the-art technologies, they claim.

Ocean waves could satisfy up to 20 percent of the world’s electricity [pdf] needs if scientists could find a way to harness them, according to London-based nonprofit Carbon Trust. Moreover, ocean waves are more stable and predictable than wind and solar power, making wave energy easier to accommodate on the grid.

However, "there is still no solution to harvest energy from ocean waves that has been proven commercially viable," says Patrik Möller, CEO of CorPower in Stockholm. The challenge lies in developing a device that is strong enough to survive violent storms, while at the same time capable of generating enough power to pay back the costs of such a robust system. "So far wave energy converters have been too large and costly compared to their energy output, which has prevented commercial harvesting," Möller explains.

Now CorPower suggests it may have cracked this challenge. Its device consists of a buoy connected by a mooring line to the seafloor. As the buoy moves up and down with ocean waves, this motion drives a turbine that generates electricity.

The new device is based in part on Swedish cardiologist Stig Lundbäck's research into how the heart works. "Heart muscle can only pump in one direction...the return motion is provided by hydraulically stored energy," Möller says. Using a similar principle, a system of gas springs in the buoy helps it harvest energy when it goes both up and down with the waves.

The buoys are up to 80 percent lighter than ones used in other wave energy systems, which helps them rise and fall easily to better harvest wave energy. These buoys also require less weight to moor them, saving on construction material costs overall.

Furthermore, the buoys are designed so they can reach the greatest heights possible no matter what the height or length of incoming waves. That allows “a large amount of energy to be harvested using a small device," Möller says. Finally, its gear technology allows it to efficiently convert the system's motion to electricity.

A CorPower unit with an 8-meter-wide buoy can generate up to 300 kilowatts in typical Atlantic waters and sells for €500,000 ($570,000), Möller says. A wave energy park with 100 buoys could generate up to 30 megawatts. "Wave power really has great potential when using the right solutions to harvest it," Möller says.

The company plans to demonstrate how well its technology survives and performs with a pilot installation on the open sea in early 2016 in cooperation with Iberdrola Engineering & Construction in Spain and WavEC Offshore Renewables in Portugal, Möller says.

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