DISADVANTAGES.

• Building the dam is expensive and time taking
• The dam will change the habitat and landscape upstream, as much more land will be submersed
• The land below the dam is also affected as the flow of water is reduced
• Silt can build up in the dam as the water slows down it does not have enough energy to carry the sand and silt which it was

WHAT IS TIDAL POWER?

Tidal Power is the generation of electrical power through the harnessing of the ebb and flow of the tides.

HOW DOES IT WORK?

A barrage, which is in fact a huge dam, is built across a river estuary or bay. This barrage has gates in it which allow the water to flow into the barrage with the incoming tide. These gates are then closed when the tide begins to go back out. This water which is now trapped inside the barrage is now called a ‘hydrostatic head’. The greater the head the more power can be generated from the outflowing water. There are other gates within the barrage which are now opened; these gates contain hydro-electric generators, very similar to the ones used in Hydropower. These generators are now turned by the outflowing water and power is generated.

The tidal range has to be sufficient in order for this to be a practical means to generate power. This range should be in excess of 5 metres otherwise the power generated is not sufficient.

The main downfall of tidal power generation is the capital needed at the beginning of the project to construct the barrages and the effect on the environment by the change in the water levels. But once the barrages have been built there is a very low maintenance cost. The generators only need changing once every 30 or so years and there is very little work needed to be done.

IS IT RENEWABLE?

Yes, the tides will continue to ebb and flow, thus there will always be power being generated. The water is not used up, it stays in the water cycle, and can therefore be used over and over again without the need for replenishment.