PORTLAND, Ore. Harnessing ocean waves could generate as much as 200 megawatts of electricity/kilometer of coast line in various parts of the world, according to the Massachusetts Institute of Technology.
MIT (Cambridge, Mass.) is conducting detailed simulations of proposed wave-powered electricity generators to optimize their performance with the goal of commercial viability.
"Many different techniques have been proposed for generating electricity from ocean waves, but so far they are not efficient enough to generate commercial investments," said MIT professor Chiang Mei. "We are creating detailed models of these techniques to identify what needs to be changed to make them commercially viable."
MIT's first detailed model was of a device being tested at the Technical University of Lisbon in Portugal that guides waves into an oscillating water column (OWC) along the shore. As waves oscillate into and out of the column, they compress and decompress the air above the column. This causes the resulting energy to turn Wells turbine blades, which are shaped like symmetrical airplane wings in the plane of rotation. The blades also are perpendicular to the air stream, permitting them to generate electricity regardless of the direction of air flow.
The current prototype lacked the efficiency needed to attract commercial investors. Now, MIT claims to have made the technique commercially viable by redesigning the system to harness resonant frequency oscillations. Mei's detailed model showed that by changing the diameter of the OWC from about three meters to as big as 20 meters, depending on location, it would be able to generate a resonant response to alternating waves, thereby magnifying the effect and generating enough electricity to attract commercial investors.
The Technical University of Lisbon is now planning a 10-meter version of MIT's design to be installed in the breakwaters at the mouth of the Douro River. The proposed wave-harnessing system would include three large OWCs that generate enough electricity to power 750 homes.
The MIT team next plans to create detailed models of other wave-harnessing techniques in hopes of making them efficient enough for commercialization. According to Mei, different wave patterns in different regions will require different techniques to harness energy. He cautioned, however, that wind and solar power are much further along in their development than wave-power designs, most of which are still more than a decade away from commercialization.