Tidal energy can be harnessed in two ways. 1) Impound the water at high tide and release it through a turbine at low tide. 2) Harness the tidal current with the underwater equivalent of wind turbines Underwater turbines use tidal flows. |
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Atlantis Resources Corporation was founded in Singapore but developed its technology in Australia where it has been operating its own dedicated tidal power test facility in San Remo, Victoria, since 2006. |
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Biostream"BioSTREAMTM employs a patented oscillating hydrofoil system to extract energy from .. current speed of 2.5m/s or greater, . An onboard computer continually adjusts the angle of the hydrofoil (fin) relative to the oncoming flow such that the tail and fin system develops a swimming motion. The energy transferred by this side-to-side motion is converted to electricity by O-DriveTM modules installed on the BioSTREAMTM." |
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Underwater kitesDeep Green produces electricity from underwater kites.
Deep Green claims the following advantages:
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Tidal barrageThese work rather like a hydro-electric scheme, except that the dam is much bigger. A huge dam (called a "barrage") is built across a river estuary. When the tide goes in and out, the water flows through tunnels in the dam. The ebb and flow of the tides can be used to turn a turbine, or it can be used to push air through a pipe, which then turns a turbine. Large lock gates, like the ones used on canals, allow ships to pass. If one was built across the Severn Estuary, the tides at Weston-super-Mare would not go out nearly as far - there'd be water to play in for most of the time. But the Severn Estuary carries sewage and other wastes from many places (e.g. Bristol & Gloucester) out to sea. A tidal barrage would mean that this stuff would hang around Weston-super-Mare an awful lot longer! Also, if you're one of the 80,000+ birds that feeds on the exposed mud flats when the tide goes out, then you have a problem, because the tide won't be going out properly any more. |
Top: the the Dam for the tidal power plant on the estuary of the Rance River, Bretagne, France Bottom: Artists impression of typical tidal barrage. |
Tidal barages are not new. England had at least one in Roman times. At one time there were 750 tide mills on the shores of the Atlantic, in England, Wales, Ireland, France, and USA. The diagram below is of a mill in 787 AD. Top right: Moulin maree brehat Bottom right: Eling tide mill is open to the public. It was mentioned in the Domesday Book in 1086 AD. |
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Tidal power for Darwin
Tenax Energy has identified three locations in Australia that meet these requirements. They are: Banks Strait, Tasmania |
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Tidal power in UKFrom tidal barrages you can reasonably expect you can get 15% of UK electricity needs, that’s a very solid number,” co-author Dr Nicholas Yates from the National Oceanography Centre told BBC News. “On top of that there is a 5% tidal stream figure, and with future technological development that is likely to be an underestimate in my view. Artist impression of barrages on the Severn UK Source This proposal has been refused on environmental grounds. |
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Tidal lagoonsThe damming of a bay can cause too many environmental changes, so it may be better to make an artificial lagoon in shallow water. Tidal lagoons are created by building a ring-shaped sand-core breakwater . Turbines mounted are mounted within the wall. When the tide moves in and out, the wall holds water back, and once it reaches a certain level, gates are opened and the water flows through the turbines, producing electricity. The project would need subsidies of £156 per MWh (15.6 p/kWh ) - similar to the subsidy on nuclear power. http://www.tidallagoonswanseabay.com/ The Guardian Subseaworld |
Tidal lagoon planned for Swansea Wales. |
An Idea with pumped hydroIt would be more profitable to wait for low and high tide, then buy power from the grid to pump water in or out of the impounded water. For example, if the tide is 2 metres, then the pumps may be able to pump in another 0.5 metres at high tide, or reduce the level by that much at low tide. Then at the opposite tide there is 2.5 M of fall to generate electricity. Five times the energy less losses. To be self contained the lagoon could be run with a pumped hydro. Excess power can be stored by pumping water up a nearby hill into a storage dam. This can then generate power on demand, including when it is needed to pump water in or out during the turn of the tide. The water flow may even be able to turn the turbine/pumps directly. The maths to calculate the optimum conditions should be lots of fun. |