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Renewable Energy - Power From The Ocean

water tidal wave plant

The potential power of the world's oceans is unknown. Because the ocean is not as easily controlled as a river or water that is directed through canals into turbines, unlocking that potential power is far more challenging. Three ideas being considered are tidal plants, wave power, and ocean thermal energy conversion (OTEC).

Tidal Power

The tidal plant uses the power generated by the tidal flow of water as it ebbs, or flows back out to sea. A minimum tidal range of three to five yards is generally considered

FIGURE 6.9

necessary for an economically feasible plant. (The tidal range is the difference in height between consecutive high and low tides.) Canada has built a small 40-megawatt unit at the Bay of Fundy, with its fifteen-yard tidal range, the largest range in the world, and is considering building a larger unit there. The largest existing tidal facility is the 240-megawatt plant at the La Rance estuary in northern France, built in 1965. Russia has a small 400-kilowatt plant near Murmansk, close to the Barents Sea. The world's first offshore tidal energy turbine near Devon, England, began producing energy in 2003.

Wave Energy

Norway has two operating wave power stations at Toftestallen on its Atlantic coast. These systems were the first significant oscillating water column (OWC) systems and they work like this: The arrival of a wave forces water up a hollow sixty-five-foot tower, displacing the air already in the tower. This air rushes out of the top through a turbine. The rotors of that turbine then spin, generating electricity. When the wave falls back and the water level falls, air is sucked back in through the turbine, again generating electricity. OWCs have been built and tested in Japan, Norway, India, China, Scotland, and Portugal.

A second type of wave energy power plant uses the overflow of high waves. As the wave splashes against the top of a dam, some of the water goes over and is trapped in a reservoir on the other side. The water is then directed through a turbine as it flows back to the sea.

These two kinds of plants are experimental. Several projects are under way in Japan and the Pacific region to determine a way to use the potential of the huge waves of the Pacific. Although considerable progress has been made in the research and development of this technology, several challenging engineering problems remain to be solved.

Ocean Thermal Energy Conversion (OTEC)

Ocean thermal energy conversion, or OTEC, uses the temperature difference between the ocean's warm surface water and the cooler water in its depths to produce heat energy that can power a heat engine to produce electricity. OTEC systems can be installed on ships, barges, or offshore platforms with underwater cables that transmit electricity to shore.

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