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stefan regelous tidal power Tidal-power is the power achieved by capturing the energy contained in moving water mass due to tides. Two types of tidal energy can be extracted: kinetic energy of currents between ebbing and surging tides and potential energy from the difference in height (or head) between high and low tides. The former method - generating energy from tidal currents - is considered much more feasible today than building ocean-based dams or barrages, and many coastal sites worldwide are being examined for their suitability to produce tidal (current) energy.

Tidal power is classified as a renewable energy source, because tides are caused by the orbital mechanics of the solar system and are considered inexhaustible within a human timeframe. The root source of the energy comes from the slow deceleration of the Earth's rotation. The Moon gains energy from this interaction and is slowly receding from the Earth. Tidal power has great potential for future power and electricity generation because of the total amount of energy contained in this rotation. Tidal power is reliably predictable (unlike wind energy and solar power). In Europe, Tide Mills have been used for nearly 1,000 years, mainly for grinding grains.

The efficiency of tidal power generation in ocean dams largely depends on the amplitude of the tidal swell, which can be up to 10 m (33 ft) where the periodic tidal waves funnel into rivers and fjords. Amplitudes of up to 17 m (56 ft) occur for example in the Bay of Fundy, where tidal resonance amplifies the tidal waves.

As with wind power, selection of location is critical for a tidal power generator. The potential energy contained in a volume of water is

E = xMg where x is the height of the tide, M is the mass of water and g is the acceleration due to gravity. Therefore, a tidal energy generator must be placed in a location with very high-amplitude tides. Suitable locations are found in the former USSR, USA, Canada, Australia, Korea, the UK and other countries (see below).

Several smaller tidal power plants have recently started generating electricity in Norway. They all exploit the strong periodic tidal currents in narrow fjords using sub-surface water turbines.

Contents [hide] 1 Dam 1.1 Modes of operation 1.1.1 Ebb generation 1.1.2 Flood generation 1.1.3 Pumping 1.1.4 Two-basin schemes 1.1.5 Tidal turbines 2 Intermittent nature of power output 3 Mathematical modelling 3.1 Physical modelling 4 Environmental impact 4.1 Tidal Energy Efficiency 4.2 Local environmental impact 4.2.1 Turbidity 4.2.2 Salinity 4.2.3 Sediment movements 4.2.4 Pollutants 4.2.5 Fish 4.3 Global environmental impact 5 Economic considerations 6 Resource around the world 6.1 Operating tidal power schemes 6.2 Tidal power schemes being considered 7 See also 8 External links 9 Sources 10 Patents