8.6 Can power from waves be harnessed as a source of energy?

  • moving water has a huge amount of energy

  • more energy in ocean waves than in rivers BUT, many obstacles to overcome for the power to be harnessed efficiently

    • preventing the devices from being destroyed by the wave force they’re built to harness

    • deployment of complex machines with exposed moving parts to the marine environment —> challenges associated w/ corrosion and biofouling (accumulation of algae and other sea life on machinery)

    • system produces significant power only when large storm waves break against it —> not reliable power, only a power supplement

    • a series of 100 or more of the structures along shore would be required

    • structures can have negative effects on marine organisms that rely on wave energy for dispersal, transporting food supplies, or removing wastes

    • harnessing wave energy might alter transport of sand along coast, causing erosion in areas deprived of sediment

  • offshore wave generating plants more likely to tap into higher wave energy found offshore but more likely to be damaged in large waves and difficult to maintain

  • most promising locations for coastal power generation = where waves refract (bend) and converge i.e. at headlands

  • internal waves are a potential source of energy too

Wave Power Plants and Wave Farms

LIMPET 500

  • LIMPET 500 (land installed marine powered energy transformer) = plant located on Islay, small island off west coast of Scotland that experiences high wave energy potential

    • plant consists of a partially submerged chamber facing the sea

  • how it works:

    • wave approaches, water level inside structure rises, compressing air in the top of the chamber

    • air is expelled through a turbine

    • turbine rotates to generate electricity

    • wave recedes —> water level falls in chamber and air is drawn back into the structure through the turbine

  • two directions of air flow through the turbine, but it’s still designed to continually produce power throughout the wave cycle

  • LIMPET 500 was constructed as a research and test facility

Wavegen - Mutriku

  • Mutriku breakwater power plant in Basque Country, northern Spain

  • world’s only commercially operated wave energy plant

Pelamis Wave Power

  • 2008, completed world’s first wave farm off coast of northern Portugal

  • project uses 3 150-meter-long devices that resemble giant segmented snakes and float half-submerged in the ocean

  • as each segment surges up or down with the crest of an oncoming wave, its hydraulic power plant pumps a biodegradable hydraulic fluid through a turbine, thus generating electricity.

Global

  • about 50 wave-energy projects in development at various sites around the world

  • projects use diff. methods to harness wave power:

    • floats or submerged pistons that move up and down with each passing wave

    • tethered paddles that oscillate back and forth

    • collection of water from breaking waves that go over coastal structures and then using the weight of that water to turn turbines as it moves downhill and returns to the ocean

Global Coastal Wave Energy Resources

  • world currently produces 12 terawatts from wave energy

  • what are the best places to develop additional wave power plants and wave farms?

    • middle latitudes between 30-60 deg N or S causes western coasts of continents to be struck by larger waves than eastern coasts —> western shores are better

CONCEPT CHECK 8.6

(1) discuss some problems that might result from developing facilities for conversion of wave energy to electrical energy.

  • very harmful to marine life who depend on the waves for food, energy dispersal, or removing wastes

  • alter transport of sand along the coast —> erosion in areas with little sediment

  • biofouling: destruction of machinery by algae and other sea life

  • machinery easily destroyed by waves i.e. corrosion

  • system can’t reliably generate power as there have to be large waves for anything to happen, and this is variable depending on atmospheric patterns and the tides

  • a series of 100 or more of the structures along the shore is necessary

  • difficult to maintain

(2) describe the locations and power-generating capability of existing offshore wave power plants and wave farms.

(3) Worldwide, where are the best locations for new wave farms? Explain the oceanographic conditions that make these locations favorable.

  • best locations = middle lats, 30-60 N or S, western coasts, headlands where orthogonals converge

  • west-to-east movement of storm systems = western coasts hit by larger waves than eastern coasts

  • larger waves associated with prevailing westerly wind belt in the southern hemisphere middle lats