Tidal energy is an essentially renewable resource which has none of the typical environmental impacts of other traditional sources of electricity such as fossil fuels or nuclear power. Changing the tidal flow in a coastal region could, however, result in a wide variety of impacts on aquatic life, most of which are poorly understood. Tidal power works because of the Moon's constant rotation around the Earth. This is very convenient because scientist's can predict the electricity production on a daily basis. .
The tides produce the electricity for tidal power by flowing in and out of turbines . A hydrostatic head or adequate water height difference on either side of the turbine.
Tidal energy works from the power of changing tides. Tidal changes in sea level can be used to generate electricity, by building a dam across a costal bay or estuary with large differences between low and high tides. The high tides allow immense amounts of water to rush into the bay. The gates of the dam then shut when water level is at its maximum height. Holes in the bottom of the dam let water (at great speed and pressure) to rush past turbines. The flow of water generates enough power to turn the turbines which creates electricity. The entire process repeats with each high tide.
Two current technologies which are used to harness the kinetic energy of tidal flow:
1) Drag Devices Water wheels :
insufficient compared to other modes of generation
blade speed can not exceed that of the current
2) Lift Devices Turbines :
wind mill technology applied to liquid environment
more efficient then drag devices
refined propeller achieves speeds several times faster then the current
How it works
Tidal power works 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 ster out to sea. A tidal barrage would mean that this stuff would hang around Weston-super-Mare an awful lot longer.
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