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Environmental Issues
Going Green

By Alan J Hartley

Energy From the Sea.



Wave Power
The seas of the World cover a huge empty expanse across which winds usually blow steadily. The potential energy of these winds is now starting to be tapped by building “Wind Farms” and being an island nation, with a coastline in excess of 11,000 miles long, Great Britain has access to a disproportionate amount of it’s own territorial waters where installations can be made at it’s own discretion. The action of the constant winds on the sea also creates waves affecting an unbelievable mass of water that is in almost constant motion at the surface as the ocean swells rise and fall. All of this moving mass represents an enormous amount of potential, untapped, clean energy that might be harnessed.

Wave energy is not the easiest source of energy to tap, as by it’s very nature, it is constantly changing direction and because of this it is very difficult to design a generating system able to take full advantage of the potential energy and yet strong enough to withstand the constant battering. One “Wave Power” system called Pelamis is showing it’s potential as it has been used to establish a 2.5MW wave farm off the Portuguese coast and more recently another prototype has been tested off the Scottish coast. Pelamis is able to withstand the oceans force by directing itself into the waves like a ship does. The 5 sections of the prototype, which are reminiscent of a snake, have pistons in between them that force fluid under great pressure, in bursts, as the sea rises and falls, into pressure storage accumulators that even out the pulsating pressure into a constant flow to the turbines. These in turn drive a dynamo and produce about 750Kw which is enough power for 500 homes, or a small village, in any conditions and unlike wind farms does not have to be shut down in a storm.

The Wave Hub
There are many other devices for harnessing the power of the sea under development and one problem that they all face is getting the electricity to the shore where it can be used practically. With this in mind “The Wave Hub” has just been established and which provides an area of sea with National Grid connection and planning consent where arrays of devices can be operated over several years for long term testing.

Underwater Turbines
Apart from “Wave Power,” the seas energy can be tapped where there is a strong current as in estuaries. Here turbines like underwater windmills are being tested, but they too have their own problems, as by their very nature they have to be installed underwater on the seabed which makes installation and maintenance difficult. However, because they do not obstruct the tidal flow of water they do not impact on the estuary, but neither do they maximise the water flows potential energy.

Tidal Barrage
In many ways these operate in a similar way to hydro-electric generation systems on dams and indeed some proposed estuary installations would include building a tidal barrage, or dam across the estuary to hold back the seawater and maximise the potential as the tide ebbs and flows. Possible sites include the Humber, Dee, Solway, Severn, Cardiff Bay and further smaller installations upstream on the Severn and Cardiff Bay schemes. The Severn Barrage as it is called and Cardiff bay schemes, each have the potential to supply 5% of the UK’s electricity requirements, but the construction of all of these tidal barrage type of proposals, have as yet, been turned down, because of the impact on the estuary surroundings. Some opponents of the Severn barrage scheme claim that the Severn has such a massive tidal flow, up to 50 feet in height, that a tidal array of underwater turbines would generate just as much power without the environmental damage of a barrage. It is probably because of the general environmental opposition to tidal barrages that there is only one in operation in Europe. The Rance Estuary tidal power station has been in operation in France since 1966, well before people really started considering the damage we are causing to the environment.



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Books By
Alan J Hartley