Tidal and Wave Power

Tidal and Wave Power
Tidal power operates by building a barrier across a river estuary. The tidal flow drives turbines to produce electricity. Europe?s only tidal power station is at Rance in Northern France. Some sites in the U.K could be developed to provide tidal power but the drawback is that these schemes affect the habitat of wildlife such as birds and fish because they alter the tidal currents. Also, barrage will only provide power for about 10 hours per day. Power for the other 14 hours must be provided by other means. Waves possess lots of energy. Experiments with various different designs of generator have proved that waves can provide electricity. However, there are problems in developing and building wave powered generators which are both cheap and efficient, as they must be strong enough to cope with storms while being light enough to work with small waves. If every reasonable project in the UK were to be exploited for tidal power the yield could be over 50 kwh a year representing 20 per cent of the electricity demand in Britain.
About 90 per cent of this potential is at eight large estuaries including Severn, Dee, Morecambe bay, Solway, Humber and Wash IN use == A Barrage 16 kilometres long (which could be built in the Severn Estuary) with 216 large turbines, could generate as much as 8640 MW and supply up to 7% of electricity for England and Wales. It would be extremely expensive to build though, costing around £8000million. It would take seven years to close the barrage to produce first electricity, and a further 2 years before full power output was achieved. The only major tidal power scheme operating anywhere in the world is in the Rance estuary between Dinard and Saint Malo in France , where a barrage with 240 MW of turbines was completed in 1966, as a pilot scheme for a prospective larger barrage across the Mont Saint Michel bay. After some difficulties with the turbines the Rance scheme, it has operated regularly and reliably for 24 years and can now serve over 300,000 people. However, the French have so far not proceeded with the large scheme, preferring to invest instead in nuclear power plants. Having said this though, in 1997, the French embarked on a project that would replace the existing 24 turbines with new ones that would harness power from the tide going both ways. This would be done 1 by 1 over the next ten years so as to not disrupt power to the 90% of Brittany that it serves. [image] (Rance Tidal Power Facility. ½ mile long and 24 turbines. Tides from the Atlantic Ocean (upper part of top photo) are trapped and then released through -?????????????????????????????????- Turbines (right). Exposed dam structure shown during construction (left). social impact Tidal electricity generation would not require waste disposal nor would it result in acidic emissions This means that if it were to replace Coal fired or Gas fired power stations for example, Greenhouse emissions would be greatly reduced. Benefits of having such a structure would be protection of a large length of coastline against storm surge tides (as with the Thames barrier), a road crossing and substantial creation of employment. Views are divided on the environmental impact of a large tidal barrage. Some say it will do irreparable damage to the ecosystem of the estuary while others maintain that it will create an exciting new reserve for water birds, fish and vegetation. Conclusion. The drawbacks of tidal and wave power are that the change in the tidal currents affect the habitat of the seabirds in the area. Also, the fish are affected by the change in the tidal currents. The tidal and wave power stations can only produce ten hours of power in one day of twenty-four hours so they would have to generate the other fourteen hours of power another way which may be quite expensive. But there are also good points about tidal and wave power. One good point is that the power produced is cheap. Also, making the power does not pollute the environment in the same ways that fossil fuels do but as mentioned above, it has other environmental consequences. Waves are a free and sustainable energy resource created as wind blows over the ocean surface. The greater the distances involved, the higher and longer the waves will be. Energy is stored in this way until it reaches the shallows and beaches of our coasts where it is released, sometimes with destructive effects. Key Facts ? Oceans cover three quarters of the earth?s surface and represent a vast natural energy resource in the form of waves. ? The World Energy Council estimates that 2TW of energy could be harvested from the world?s oceans, the equivalent of twice the world?s electricity production. ? In the UK alone it has been estimated that the recoverable wave energy resource exceeds total UK electricity demand ? As a general rule coastlines with an ocean fetch of greater than 400km are suitable, but even greater resources are available between latitudes 300 and 600 in the Northern and Southern hemispheres. ? If less than 0.1% of the renewable energy within the oceans could be converted into electricity it would satisfy the present world demand for energy more than five times over. [image] Relative Global Wave Energy Density Figures in kW/m Source: Wave Energy paper. IMechE, 1991 and European Directory of Renewable Energy (Suppliers and Services) 1991 Wave devices are comprised of two basic elements; a collector to capture the wave energy and a turbo generator to transform the wave power into electricity. 1.The Collector and Oscillating Water Column (owc) The wave energy collectors used in Wavegen?s Limpet and Osprey modules are in the form of a partially submerged shell into which seawater is free to enter and leave. As the water enters or leaves, the level of water in the chamber rises or falls in sympathy. A column of air, contained above the water level, is alternately compressed and decompressed by this movement to generate an alternating stream of high velocity air in an exit blowhole. If this air stream is allowed to flow to and from the atmosphere via a pneumatic turbine, energy can be extracted from the system and used to generate electricity [image] [image] 2.Power Take Off ? The Turbo Generator Wells turbines are used to power the electricity generators. Wells turbines have the unique property of turning in the same direction regardless of which way the air is flowing across the turbine blades. Thus, the turbines continue turning on both the rise and fall of wave levels within the collector chamber. The turbine drives the generator, which converts this power into electricity.

Tidal and Wave Power 8.9 of 10 on the basis of 2599 Review.