Ocean Energy Facts

A tremendous amount of energy can be tapped from our oceans. Wave and tidal power are increasingly joining the mix of promising offshore renewable energy resources.

Breaking waves, Tenerife, Canary Islands. Spain.
© Anton Vorauer / WWF

Wave power

Waves are driven primarily by the winds. Capturing this energy is not easy but technology is becoming more readily available.
Wave energy can be converted through:
  • channel systems that funnel the waves into reservoirs
  • float systems that drive hydraulic pumps
  • oscillating water column systems that use waves to compress air within a container
The mechanical power created from these systems either directly activates a generator or transfers to a working fluid, water or air, which then drives a turbine or generator.

Such technologies are still quite expensive, but costs could be reduced drastically with the right scale of development.

Wave power and tidal power are not, however, without environmental concerns. Special care is needed to avoid disruption to the sea area and the risk of pollution to rivers.

Tidal power

Tides are driven primarily by the gravitational pull of the moon. Tidal power works by harnessing ocean tides, especially in narrow river mouths or sea straits, to produce energy.

Tidal streams are converted into electricity by forcing the water through turbines, which activate a generator.

Options include dams, tidal lagoons and tidal stream systems.

Tidal power generators can be expensive to set up. However, they have the potential to deliver cheaper electricity in the long term.

The oldest tidal power plant was set up 1965 on the Rance River in northwestern France with 24, 10MW generators. It has functioned without fail ever since. Other plants exist in Russia, Canada and China.

More recent projects include the SeaGen, a 1.2 MW tidal stream energy convertor, which operates in Strangford Lough in the Irish Sea off Northern Ireland.
Red metal, jointed tubing moving in the sea waves. 
	© Pelamis Wave Power
The world's first commercial wave farm is based in Portugal. It consists of three 750 kilowatt Pelamis wave energy converter machines.
© Pelamis Wave Power
The earliest evidence of using ocean tides for power conversion dates back to about 900 A.D. Early tidal power plants used naturally-occurring tidal basins by filling a dam at high tide and then releasing the water through a waterwheel. The power was typically used for grinding grains into flour.
	© Marine Current Turbines
SeaFlow tidal stream generator prototype with the rotor raised.
© Marine Current Turbines

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