| Catching the wave

Tidal energy is a kind of hydropower that converts the energy of the rise and fall of sea levels caused by tidal movements into useful energy. Tides are highly predictable, which makes tidal energy a much more reliable alternative energy source than solar or wind power. It is also one of the cleanest sources of power because it utilizes existing resources and creates no pollution. Tidal power works by harnessing the energy of the tides and converting it into electricity. An enormous dam called a barrage can be constructed across a river estuary, or the mouth of the river. As the tide moves inwards and outwards, the water flows through tunnels in the dam and turns a turbine. Alternatively, large chains of underwater turbines called tidal fences can be built; the movement of the water causes the turbines to generate electricity.

The world’s first fully-fledged tidal station was the Rance Tidal Power Station, which was built on the estuary of the Rance River in Brittany, France in 1966. Other successful tidal power plants exist in Nova Scotia, China, Russia, South Korea and the United Kingdom. More tidal stations have been proposed, or are under construction, but tidal power is still not widely used.

The original kinds of tidal barrages and fences were unproductive, as they did not generate much power and were not cost-efficient. However, tidal power machinery has progressed greatly since its inception; it is now cheaper to produce than nuclear power. Early tidal turbines were not environmentally friendly because organisms often got caught in them, but, modern turbines are completely safe for fish.

Tidal barrages and fences can be very expensive to build, although the price is eventually offset by the low cost of upkeep. Once the turbines have been built, tidal power is completely free. The machinery does not consume fuel and requires very little maintenance. Tidal energy is also more powerful than wind power, as water has a higher density than air and, therefore, can apply more force on the turbines. The environmental impact on the tides is negligible, as research shows the tidal movements change only very slightly with the construction of a barrage or fence. However, tidal barrages can only be built in some locations, as they require a narrow channel, relatively deep water, and a high tidal flow.

There are some environmental issues associated with tidal power that are preventing its widespread use. Some tidal barrages may block sewage and waste from being carried out to sea, which can damage both aesthetics and ecosystems. The power can only be generated when the tide is coming in or going out, so it’s not a continuous energy supply; depending on the area, energy can be generated for only about 10 hours per day. Unfortunately, tidal power stations could have negative impacts on aquatic and shoreline ecosystems – both up and downstream of the power station.

Despite being cost-efficient and relatively stable for the environment, tidal energy is not yet widely used. Engineers and power companies have been examining the great potential for tidal power as a major source of energy in the future. It cannot yet be used as a replacement for fossil fuels, but the construction of more tidal power stations can gradually increase the use of tidal power worldwide.


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