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288 OCEAN ENERGY TECHNOLOGIES
MOON
QUARTER PHASE
SOLAR TIDE
LUNAR TIDE
NEAP TIDES
SOLAR TIDE
MOON
FULL OR NEW
LUNAR TIDE
SPRING TIDES
Figure 9.1 The effects of the moon and sun on
ocean tides.
sun are at right angles to each other, lower tidal differences are experienced, which
results in the neap tides (Fig. 9.1).
Tidal Power Generation
The generation of electricity from tides is similar to hydroelectric generation, with the
exception that water flows in and out of the turbines in both directions. Therefore, gen-
erators are designed to produce power when the rotor is turned in either direction.
A tidal power station, known as an ebb-generating system, involves the construction
of a dam, known as a barrage, across an estuary. A number of sluice gates on the bar-
rage allow the tidal basin to fill with the incoming high tides and to exit through the
turbine system on the outgoing tide, referred to as the ebb tide. As mentioned earli-
er, special generators used to produce electricity on both incoming and ebb tides are
also possible.
Tidal power is a technology that makes use of captured energy contained in moving
water mass owing to tides for conversion into electricity. Types of tidal energies