Clean Renewable Energy
Tidal

The generation of electricity from tidal waves is similar to hydroelectric power generation. Barrages are built at the bottom of a tidal basin. The tidal basin fills during high tides and empties during low tide through a turbine which will turn an electric generator to produce electricity.

How it works

Tidal turbines are similar to wind turbines and are arranged underwater in rows and work best during strong tides. Even though they capture more energy they are heavier and costlier to build. They do not interfere with migration paths and are therefore the least environmentally damaging of tidal power technologies.

For tidal power to work successfully there must be a tide difference of at least 16 feet. There are only a few places on Earth with this type of tidal range for example France. Tidal power converts the energy of tides into electricity. Tides are more predictable than wind and solar energy. Tidal power is inexhaustible and is a renewable energy source because the Earth's tides are caused by the gravitational interaction with the moon and sun and the Earth's rotation which is an ongoing process.

Tidal power can be classified under two main types: tidal streams systems - Make use of the kinetic energy of moving water to power turbines.
It costs less and a lower ecological impact compared to barrages. Tidal lagoons - are constructed as self contained structures, not fully across an estuary and have lower cost and lower impact. Tidal stream generators can provide significant power at low tidal flow velocities.

Advantages

• Tidal power is free and the only cost incurred is the building of the power plant.
• No greenhouse gasses or other waste products are produced.
• No fuel is needed.
• Electricity production is reliable.
• Maintenance is cheap.
• Tides are predictable.
• Offshore turbines and vertical axis turbines are inexpensive to build and do not have a large impact on the environment.    

Disadvantages

• It is very expensive to build a barrage across an estuary and it affect a very wide area.
• The environment is affected for many miles upstream and downstream.
• It affects the birdlife especially those that rely on the tide to uncover the mud flats so that they can feed.
• The barrage across the estuary will cause sediment accumulation affecting the ecosystem and the operation of the barrage.
• The salinity inside the basin will decrease thus affecting the ecosystem.
• Some fish are unable to escape the water's speed near a turbine and will be sucked through resulting in high fish mortality.
• There are few suitable sites for tidal barrages.
• Tidal power only provides power for about 10 hours each day that is during high tides and low tides.

References

Wikipedia Contributors (2009) Tidal Power [online] (20 March 2009)
Available at: http://en.wikipedia.org/w/index.php?title=Tidal_power&oldid=279085394
Accessed 21 March 2009

Matthew Hick (2007) Ocean Tidal Power as Renewable Energy[Online] (1 March 2007)
Available at: http://www.freearticles.co.za/environment/ocean-tidal-power-as-renewable-energy.html
Accessed 18 March 2009

Treehugger, 2008,Hydro Power Without the Dams: Ontario Invests in Free Flow Underwater Turbines [Online](14 April 2008)
Available at http://www.treehugger.com/files/2008/04/verdant-power-free-flow-underwater-turbines-hydro.php
Accessed 18 March 2009

Background Image:
James Balog, 2007, Mer De Glace Glacier[electronic image]
Available at: http://www.environment.nationalgeographic.com
Accessed 27 February 2009

Also See:

The case of the missing
carbon |
Can the Sahara power
Europe? |
Glossary of important
terms |
What you can do |

Cross section of a tidal turbine