咩叫TIDAL ENERGY??

Tidal Power is the power of electricity generation 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.

One method of extracting tidal energy involves building a barrage and creating a tidal lagoon. The barrage traps a water level inside a basin. Head is created when the water level outside of the basin or lagoon changes relative to the water level inside. The head is used to drive turbines. In any design this leads to a decrease of tidal range inside the basin or lagoon, implying a reduced transfer of water between the basin and the sea. This reduced transfer of water accounts for the energy produced by the scheme. The largest such installation has been working on the Rance river (France) since 1967 with an installed power of 240 MW, and an annual production of 600 million kWh.

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 corn.

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.

tidal
[5taidl]
adj.
潮汐的, 定時漲落的

tidal
[5taidl]
adj.
潮汐的, 潮水般的
(船只)根據潮汐漲落情況而決定駛離時間的
由于潮水作用的, 定時漲落的
tidal current
潮流
tidal gate
擋潮閘
tidal harbour
潮汐港
tidal power station
潮汐發電站

tidal wave
潮波; 海嘯; [喻](公眾情緒上的)浪潮, 大波動; 激動的民心; (人事上的)大變動
tidally
adv.