Professor Tsumoru Shintake of the Okinawa Institute of Science and Technology University thinks wind and solar power are wonderful things. But research in those areas is a crowded field. He wants to investigate other forms of renewable energy, like turbines driven by ocean currents and waves.
Being a nation of islands, Japan is keenly attuned to the problem of erosion. Nearly 30% of its coastline is protected from the ravages of the sea by tetrapods, man-made pyramids that help reduce the power of waves before they reach the shore. Professor Shintake and his team would like to redesign those wave-breaking devices to incorporate small turbines that generate electricity from the power of the flowing water.
“Using just 1% of the seashore of mainland Japan can [generate] about 10 gigawatts [of energy], which is equivalent to 10 nuclear power plants,” Professor Shintake explains. “That’s huge.” It is especially huge in Japan, where nuclear power has a somewhat mixed track record.
Previously, Shintake has spearheaded a project labeled Sea Horse that places turbines tethered to the ocean floor in the middle of ocean currents, but maintaining the equipment is difficult and the cables carrying electricity to shore are problematic. He says his wave power process would be cheaper to install and maintain.
The turbines are designed to withstand the tremendous force that ocean waves can create. Inspired by dolphin fins, the blades that turn the turbines are flexible so they can relieve excess stress. Rigid blades would simply break under the power created by typhoons and the like.
The supporting structure is also flexible. It’s “like a flower,” Shintake explains. “The stem of a flower bends back against the wind,” so the shafts that hold the turbines upright are designed to bend when overwhelmed by strong waves. The turbines are also designed to be safe for the surrounding marine life — the blades rotate at a carefully calculated speed that allows creatures caught among them to escape.
The first experimental turbines are now ready to be installed. They are half-sized versions with blades just about one foot in diameter. The full scale turbines — with blades about 2 feet in diameter — turn a permanent magnet generator. A ceramic mechanical seal protects the electrical components inside from the salt water surrounding it. The normal useful life of each turbine is expected to be ten years or more.
“I’m imagining the planet two hundred years later,” Professor Shintake says. “I hope these [turbines] will be working hard quietly, and nicely, on each beach on which they have been installed.” If the concept proves viable, wave powered generators could be a source of renewable energy for many of the world’s more than 3100 inhabited islands and for coastal areas.
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