Hydro-electric power is the most common form of generating electricity from water at the moment. Generally what happens is a reservoir is built with a dam in it, a mass of water is held back by the dam, and then suddenly released all at once, sending the water through a turbine at great force.
This kind of system used to be widespread before we started using engines. Hydro-electricity powered things like flour mills and was also used to power machinery. However, these were replaced by engines when fuel to run them was very cheap.
Hydro-electric power is pollution free and safe once it's up and running, although in creating it there can be tremendous disruption and upset to the environment, animals and nearby residents.
Hydro-electric power supplies about 20% of world electricity. Norway produces almost all of its electricity from hydro whilst Iceland and Austria produce over 70% of their electricity requirements from hydro plants. The greatest restriction to large extension of hydro-electric power in the UK is a lack of suitable sites.
Tidal power however works by using the gravitational pull of the moon, which creates tidal rises and falls, to produce energy. A recent inquiry into harnessing tidal power in the Severn Estuary has rejected plans for a multi-million barrage between Weston-super-Mare and Cardiff. The commission’s inquiry said a larger Severn barrage would “do serious damage to the estuary by wiping out around 80% of the ‘inter-tidal habitat’.”
There is a large-scale tidal power scheme on the River Rance near St Malo in France, which helps produce a considerable amount of electricity. Others in Russia, Canada and China have also been very productive and economical.
The third way of getting power from our waters is by using the energy created by waves. This mass of kinetic energy can be captured quite effectively, and the UK is potentially a good location for such an idea. But while other sources of renewable energy – such as wind and solar – have been widely adopted in recent years, wave energy has been slow to take off.
There are several ways of capturing the energy from waves, and some of them, such as building dams or pipes for the water to go up, can be quite expensive, and also could be disruptive to other industry, such as fishing.
Alternative energy sources: