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April 23, 2014  |  Login
Wave and Tidal Power

This isn't technically a breakthrough, but it's a niche that deserves mention. Here's the story: Right up there with sun and wind on the list of free energy that the earth is kind enough to provide is moving water. Rivers flow continuously and the ocean tides go in and out regularly. This is clean, abundant energy, just waiting to be tapped. And lots of different methods are being tried: buoys anchored to the ocean floor that generate electricity as they rise and fall with the tides, rotor blades turned by ocean tides and river current, and segmented snake-like devices that generate electricity as ocean waves make them undulate. The list goes on, and all sound at least intriguing. But as of this writing none have managed to generate cost-effective power for long periods of time. This last stipulation (longevity) is the deal breaker, because bodies of water are tough environments for machinery.

Waves come at submerged generators from varying angles and speeds, while seawater is corrosive, reducing conventional metals to rust-frozen junk in no time at all. But the lure of all this free power is such that ideas abound, and many are getting a tryout. Among the generators and projects that bear watching:

Breakwater Systems consist of an opening below the water level that is connected to a column of air and water chambers. Breaking waves force water into the opening, altering the air pressure in the column and driving a turbine. British firm RWE Innogy plans to build such a generator off the Scottish coast.

Pelamis Device is a snake-like series of cylindrical, hinged sections generates power when the waves move the sections. In early 2008 Scotland-based Pelamis Wave Power was installing four such generators as part of a Scottish Power-sponsored trial.

PowerBuoy consists of modular, ocean-going buoys (12 feet in diameter and 52 feet long) that rise and fall with waves, creating mechanical energy which is converted into electricity and transmitted to shore over a submerged transmission line. Canadian firm Finavera Renewables is installing its own version of this technology in projects off the coasts of Portugal and North America.

Wave power holds promise because there's so much water energy out there. If one or more of the devices now being tested turn out to be cheap and durable, then wind and solar might face some new competition.


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