Devil wrote:Tidal energy, on a reasonable scale, usually demands damming of estuaries.
from http://www.bluenergy.com/TidalEnergyPrimer.pdf
The oldest technology to harness tidal power for the gneration of electricity involves building a dam, known as a barrage, across a bay or estuary that has large differences between high and low tides. Water retained behind a dam at high tides generates a power head sufficient to generate electricity as the tide ebbs and water released from within the dam turns conventional turbines.
Though American and Canadian governments considered constructing ocean dams to harness the power of the Atlantic tides in the 1930's, the first commercial-scale tidal generating barrage rated at 240 MW was built in La Rance, France. This plant continues to operate today as does a smaller plant contructed in 1984 with the Annapolis Royal Tidal Generating Station in Nova Scotia, rated at 20 megawatts (enough power for 4,500 homes). One other tidal generating station operating today is located near Murmansk on the White Sea in Russia, rated at 0.5 megawatts.
These first-generation tidal power plants have all withstood the rigors of the marine environment and been in continuous pollution-free operation for many years. But due to the very high cost of building an ocean dam to harness tidal power, and the environmental problems from the accumulation of silt within the catchment area of the dam (which requires regular, expensive dredging), engineers no longer consider barrage-style tidal power feasible for energy generation.
Second-generation, tidal current power production
Engineers have recently created two new kinds of devices to harness the energy of tidal currents (AKA 'tidal streams') and generate renewable, pollution-free electricity. These new devices may be distinguished as vertical-axis and horizontal-axis models, determined by the orientation of a subsea, rotating shaft that turns a gearbox linked to a turbine with the help of large, slow-moving rotor blade. Both models can be considered a kind of underwater windmill. While horizontal-axis turbine concepts are now being tested in northern Europe (the UK and Norway) a vertical-axis turbine has already been successfully tested in Canada. Tidal current energy systems have been endorsed by leading environmental organizations, including Greenpeace, the Sierra Club of British Columbia and the David Suzuki Foundation as having "the lightest of environmental footprints," compared to other large-scale energy systems.
frankthetank wrote:Underwater submarine windmills in the Gulf stream, say off the coast of Florida? The flow of water through there is something like 300 times the volume of the Amazon River.
That would produce some electric current, and would also screw Europes mild climate, if not the worlds.
The wave energy potential in the EU has been estimated conservatively as 120–190 TWh/year offshore and an additional 34–46 TWh/year at near shore locations.
However, these estimations depend on assumptions of technology and energy cost. The actual resource could be a magnitude larger.
Starvid wrote:For a comparison Swedish energy use is 450 TWh/year, of which electricity is 145 TWh. We have very electricity intensive industry
(steel, pulp) so I figure average in Europe is 10 TWh electricity per 1 million people and year. With an EU population of about 500 million electricity use should be roughly 5000 TWh a year. In the most optimistic scenario wave power could supply half of that! In the most pessimistic scenario it will still be 3-5 %, vastly more than wind power will ever contribute.
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