Tidal Power
From Lauraibm
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Tidal power, sometimes called tidal energy, is a form of hydropower that exploits the rise and fall in sea levels due to the tides, or the movement of water caused by the tidal flow. Because the tidal forces are caused by interaction between the gravity of the Earth, Moon and Sun, tidal power is essentially inexhaustible and classified as a renewable energy source. In fact though, the ultimate energy source is the rotational energy of the Earth. The energy of the tides comes at the expense of decreased rotational energy of the planet, and will run out eventually.
Although not yet widely used, tidal power has great potential for future electricity generation and is more predictable than wind energy and solar power. In Europe, tide mills have been used for nearly a thousand years, mainly for grinding grains.
Tidal power can be classified into two types,
- Tidal stream systems make use of the kinetic energy from the moving water currents to power turbines, in a similar way to underwater wind turbines. This method is gaining in popularity because of the lower ecological impact compared to the second type of system, the barrage.
- Barrages make use of the potential energy from the difference in height (or head) between high and low tides, and their use is better established. These suffer from the dual problems of very high civil infrastructure costs and environmental issues.
Modern advance in turbine technology may eventually see large amounts of power generated from the oceans using the tidal stream designs. Arrayed in high velocity areas where natural flows are concentrated such as the west coast of Canada, the Strait of Gibraltar, the Bosporus, and numerous sites in south east Asia and Australia. Such flows occur almost anywhere where there are entrances to bays and rivers, or between land masses where water currents are concentrated.
A factor in human settlement geography is water. Human settlements have often started around bays rivers and lakes. Future settlement may be concentrated around moving water, allowing communities to power themselves with non-polluting energy from moving water.
Energy efficiency
Tidal energy has an efficiency of 80% in converting the potential energy of the water into electricity, which is efficient compared to other energy resources such as solar power or fossil fuel power plants.
Global environmental impact
A tidal power scheme is a long-term source of electricity. A proposal for the Severn Barrage, if built, has been projected to save 18 million tons of coal per year of operation. This decreases the output of greenhouse gases into the atmosphere.
If fossil fuel resource is likely to decline during the 21st, as predicted by Hubbert peak theory, tidal power is one of the alternative source of energy that will need to be developed to satisfy the human demand for energy
