Wave

  • Power from the waves uses various dynamics of ocean waves to generate energy: the lifting force (heave), swaying and turning, changing underwater pressure, etc.
  • Key challenges are efficiency, longevity/maintenance, and ability to harvest the electricity to the shore.
  • A major appeal of harvesting wave energy is wave proximity to population centers. More than half of the world's population lives within 125 miles of the ocean; eight of the 10 biggest cities are on the coast. Iceland, the American west coast (especially the Pacific Northwest and Southeast Alaska), Norway, the UK, Argentina, Chile, South Africa, and Southeastern Australia are particularly good sites for high-energy waves. Rusch, 11
  • Waves, unlike tidal, do not rely on site-specific design

Methods of electricity generation

  • Airbags push air back and forth through an underwater wind turbine due to the changing underwater pressure as waves roll overhead. Though there is less energy availability at the ocean floor, the device is well-protected from storms, out of sight, and ship-passable- explored at M3 Wave Energy Systems by Mike Morrow and Mike Delos-Reyes Rusch, 17
  • A buoy fixed to a sliding magnet assembly rises and falls, sliding up and down on a rod containing stationary generator coils– explored at Oregon State University by Annette von Jouanne Rusch, 26
  • A buoy lifting up and down moves a lever arm either above the water or sloped below the water- explored at the University of Edinburgh by Stephen Salter Salter, 400
  • A hinged flap moves horizontally with the wave; the hinge contains a dynamometer. This motion appears to be more efficient than using the heave to move a buoyant object- explored at the University of Edinburgh by Stephen Salter Salter, 401
  • Salter's Duck: built for maximal efficiency in harvesting all of a wave's energy (90% achieved) with a round back to allow for the circular motion of water particles in a wave and a pointed front to allow the water particles to continue their decaying orbitals- explored at the University of Edinburgh by Stephen Salter Salter, 401
  • Hose pump: a hose is held in a fixed position below the water and fastened at the other end to a buoy. As the buoy bobs, the hose extends and narrows, which forces water to move through a turbine- explored by Finavera Renewables in Canada Rusch, 33
  • Wave power by Pelamis (Scotland): semi-submerged articulated structure undulates, pushing hydraulic rams at each joint, which pump fluids through hydraulic motors to generate electricity Lovins, 77, Rusch, 34
  • Wave + hydroelectric power by Aquamarine Power's Oyster (Scotland): a hinged flap connected to the seabed 30m down moves back and forth sideways, pushed by the waves. This drives a hydraulic piston, which shoots high-pressure water to an onshore turbine Lovins, 78, Rusch, 35
  • Wave Dragon (Denmark): essentially a floating hydroelectric dam. Waves crash over into a reservoir, raising the water level above sea level; water drains out through hydroelectric turbines Rusch, 34
  • Oceanlinx (Australia): waves crash water into the device, which pushes air upward through a wind turbine. As the water recedes, it pulls air into the vacuum left behind, spinning the turbine again. There are no moving parts underwater, and the device is stationary and built to break waves, so can be used as a breakwater Rusch, 35
  • Plastic sheets are secured vertically in the ocean from the floor to a bobbing raft; on the down-bob, the sheets bend. Researchers at IIT are experimenting with harvesting the piezoelectric effect from this bending Charlier, 11

Economic viability

  • U.S. Electric Power Institute finds that wave power may be economically viable at 10-20 GW Charlier, 10
  • Idea that waves might power ships for motion is more attractive per power harvested than electricity generation Charlier, 13

Commercialization

  • Ocean Power Technologies (New Jersey) is the first company in the United States to receive a permit to use waves to generate electricity for commercial sale. They plan to deploy a Mark 3 PowerBuoy (heave-based design) off of Reedsport, Oregon for an initial 150 kW Rusch, 65-71

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