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.
APPLICATIONS OF TIDAL POWER
Small-scale tidal mills were used in the Middle Ages for grinding corn. The barrages which are built can be used as a means to cross the estuary with much greater ease. The main application of tidal power is as an additional means of generating renewable, sustainable energy which does not affect the environment in a negative way.
ADVANTAGES
It is very cheap to maintain
There is no waste or pollution
Very reliable
We can predict when tides will be in or out
The barrage can help to reduce the damage of very high tidal surges or storms on the land
DISADVANTAGES
It changes the coastline completely and the estuaries are flooded so any mud flats or habitats that birds or animals live on are destroyed
Initial building cost is very expensive
Water is not replenished, it cannot flow away so any dirt or pollution lingers around the coast much longer
Silt builds up behind the barrage
Disrupts creatures’ migration in the oceans
Needs a very big piece of sea to be cost effective
Not many sites suitable for this kind of power generation; building the barrage
Only produces power for about 10 hours of the day