Dpurdy's List: Wave Energy

• Ocean   waves are caused by the wind as it blows across the sea. Waves   are a powerful source of energy.

• How it works

           

  There are several   methods of getting energy from waves.     One of them works like a swimming pool wave machine   in reverse.   At a swimming pool, air is blown in and out of a chamber   beside the pool, which makes the water outside bob up and down,   causing waves.
  At a wave power station, the waves arriving cause   the water in the chamber to rise and fall, which means that air   is forced in and out of the hole in the top of the chamber.   We place a turbine   in this hole, which is turned by the air rushing in and out.   The turbine   turns a generator.

• a floating tube called "Pelamis".  

   

  

   

  This long, hinged tube (about the size of 5 railway   carriages) bobs up and down in the waves, as the hinges bend they   pump hydraulic fluid which drives generators.
• Once you've built a wave power station, the energy is   free, needs no fuel and produces no waste or pollution.
• Not expensive to operate and maintain.
• Needs a suitable site, where waves are consistently   strong.
• Some designs are noisy. But then again, so are   waves, so any noise is unlikely to be a problem.
• Is it renewable?

  Wave   power is renewable.

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• Ocean waves are a tertiary form of solar energy, in that unequal   heating of the Earth’s surface generates wind, and wind blowing over   water generates waves. Despite the fact that nearly 75% of the Earth’s   surface is covered with water, waves are a largely unexplored source   of energy, compared with the progress that has been made in harnessing   the sun and wind.

• ocean waves is long considered substantive kinetic resource

• Waves are generated by wind passing over the surface of the sea. As long as the waves propagate slower than the wind speed just above the waves, there is an energy transfer from the wind to the waves.
• The first known patent to utilize energy from ocean waves dates back to 1799 and was filed in Paris by Girard and his son.^[12] An early application of wave power was a device constructed around 1910 by Bochaux-Praceique to light and power his house at Royan, near Bordeaux in France
• Once the wave energy is captured at a wave source, power must be carried to the point of use or to a connection to the electrical grid by transmission power cables.^[2
• The realistically usable worldwide resource has been estimated to be greater than 2 TW.^[49][50] Locations with the most potential for wave power include the western seaboard of Europe, the northern coast of the UK, and the Pacific coastlines of North and South America, Southern Africa, Australia, and New Zealand. The north and south temperate zones have the best sites for capturing wave power. The prevailing westerlies in these zones blow strongest in winter. Waves are very predictable; waves that are caused by winds can be predicted five days in advance.^{[citation needed]}
• There is a potential impact on the marine environment. Noise pollution, for example, could have negative impact if not monitored, although the noise and visible impact of each design varies greatly.^[5]. Other biophysical impacts (flora and fauna, sediment regimes and water column structure and flows) of scaling up the technology is being studied.^[51] In terms of socio-economic challenges, wave farms can result in the displacement of commercial and recreational fishermen from productive fishing grounds, can change the pattern of beach sand nourishment, and may represent hazards to safe navigation.^[52] Waves generate about 2,700 gigawatts of power

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• Tides are caused by the gravitational pull of the moon and sun, and the rotation   of the Earth. Near shore, water levels can vary up to 40 feet due to tides.  

    

  Dam of the Tidal Power Plant on the Estuary of the Rance River, Bretagne, France

    

  Source: Stock photography (copyrighted)

    

   

  Tidal power is more predictable than wind energy and solar power. A large enough tidal range — 10 feet — is needed to produce tidal energy  economically.
• The United States has no tidal plants and only a few sites where tidal energy could be   produced economically. France, England, Canada, and Russia have much more potential to use this type of energy.
• Tidal turbines are basically wind turbines in the water that can be located anywhere there is strong   tidal flow. Because water is about 800 times denser than air, tidal turbines have to be much sturdier than wind turbines. Tidal turbines are heavier and more   expensive to build but capture more energy.
• Waves are caused by the wind blowing over the surface of the ocean. There is tremendous energy in the ocean waves. It's estimated that the total potential off the coasts of the United States is 252 billion kilowatthours a year, about 6% of the United States' electricity consumption in 2010.  The west coasts of the United States and Europe and the coasts of Japan and New Zealand are good   sites for harnessing wave energy.
• Many more ways to capture wave energy are currently under development. Some of these devices being developed are placed underwater, anchored to the ocean floor, while others ride on top of the waves. The world's first commercial wave farm using one such technology opened in 2008 at the Aguçadora Wave Park in Portugal.

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• Power generation using wave energy is at a much earlier stage of
   development. Wave energy offers more predictable outputs than wind, but in early 2003
   there was only around one megawatt of generating capacity installed worldwide, all of it essentially with demonstration prototypes. Proposed projects are likely to take this to about 6 MW over the next few years. The wave industry is characterised by a wide variety of novel devices
•   

  Can Already Cost Under $.06 per Kilowatt Hour

   

  * Pneumatic devices, such as the oscillating water column (OWC), use wave motion to compress and decompress air, and drive a turbine.

   

  * Float-based devices utilise a buoyant float moving with the waves, reacting against a sea bed anchor in order to harness energy.

   

  * Spillover devices utilise wave height to replenish a reservoir of seawater, which runs a turbine.

   

  * Raft-type devices use the relative motion of adjacent rafts or pontoons to harness wave energy.

   

  * Moving-body devices articulate in the water, inducing motion, which may be used to drive a hydraulic motor.
• Tidal stream devices extract energy from the diurnal flow of tidal currents (caused by the gravitational pull of the moon). Unlike wind and wave power, tidal streams offer entirely predictable output. However, as the lunar cycle is of around 25 hours’ duration, the timing of peak outputs differs by around an hour each day and tidal energy cannot be guaranteed at times of peak demand.
• However, several large grid-connected demonstration projects are expected to enter the water in the near future. Tidal stream is thus a few years behind wave energy.
• Marine Current Turbines is about to field test a submerged 300 kW tidal turbine off Devon in the United Kingdom
• The manufacturers of all these devices expect to deliver
   energy at a cost of 10-14 US cents per kWh, falling to below 6 US cents as
   experience grows and technologies mature

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• What is wave energy?

   

  Waves are generated by the passage of wind across the surface of the sea.  Energy is transferred from the wind to the waves.  Waves travel vast distances across the ocean and at great speed and the energy is concentrated near the water surface.  The energy within a wave is proportional to the square of the wave height.  Therefore a two-meter high wave has four times the power of a one-meter high wave.

   

  The longer and stronger the wind blows over the surface of the sea, the higher, longer, faster and more powerful the sea is.
• Although wave energy is a form of concentrated wind energy, as it has often travelled over large distances it is regularly out of phase with the local wind conditions.  Wave energy can therefore help to balance output variability from other renewable sources and maximise the efficient use of the electricity networks.   Wave energy is also more predictable than many other forms of renewable energy, such as wind or solar, and can be forecast accurately up to five days in advance.
• Wave energy is clean and renewable!  It is one of the last renewable energy forms which mankind has yet to harness, and its potential is huge.
• Wave energy could play a major part in the world’s efforts to combat climate change, potentially displacing 1 – 2 billion tonnes of CO2 per annum from conventional fossil fuel generating sources.

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