Good Energy’s information on tidal power
Tides are caused by the gravitational force of the moon (and to a lesser extent the sun) on the earth’s oceans. The moon’s gravitational force attracts water towards it, causing a slight bulge in the areas of water facing it. As the earth rotates, and a different part of its surface faces the moon, water bulges in that area becoming slightly shallower elsewhere.
Tidal power is generated by exploiting this regular rise and fall of seas and oceans around the coast. There are two common methods of harnessing tidal energy.
A tidal barrage with turbines can be built across an estuary or bay. As the tide comes in, water flows through the turbines generating power. When the tide goes out the turbines are turned again, creating more power. Only at high and low tide are the turbines still, although by controlling the flow out it is sometime possible to mitigate this effect. However, barrages like this may have negative effects on the surrounding land and wildlife. They change the natural flow of the bay or estuary and can lead to some areas being underwater for much longer periods which could affect vegetation around the coast, affecting the organisms that depend on it. Water quality and levels of sediment in the bay would change, and fish might be in danger of being killed by turbines. All these changes would affect the types of birds in the area, and they may migrate to other areas with more favourable conditions.
Tidal stream power uses fast-flowing currents – usually round headlands and islands – to turn turbines to generate electricity. These turbines look like mini underwater wind turbines and are relatively small and inexpensive for the amount of tidal power they are able to generate. They’re also easy to decommission and have a low environmental impact as they sit on the sea bed and work with the water flowing naturally past them.
The environmental effects of tidal streams are arguably less severe than those for tidal barrages, though they will of course affect the seabed which could have a knock-on effect on aquatic life in the area.
Both types of tidal power are relatively predictable and reliable sources of renewable energy. Because of the regularity of the tides, unlike the weather, it is easy to predict a timetable for when tidal energy will be generated, even over a long period of time. In fact, the department of Business Enterprise and Regulatory Reform has estimated that 10% of the UK’s electricity needs could be met by tidal power. [BWEA]
The practicalities of tidal power
3000GW of tidal energy is estimated to be available worldwide (World Offshore Renewable Energy Report 2002-2007; DTI).
The strong tidal races around Alderney in the Channel Islands could generate up to 3GW of tidal power – enough to fulfill the island’s electricity requirement and leave surplus for export.
Good Energy and tidal power
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Switching to Good Energy is the first step in supporting tidal power.
