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Gravity: Tidal Power
Tides are the result of the Moon pulling on the oceans and seas. The rise and fall of the sea surface has been used on a small scale for hundreds of years.

Many large tidal schemes have been proposed, but few ever built. One of the reasons being the adverse environmental impact such schemes can have on local eco-systems. One successful scheme is at La Rance, in northern France.

Using tidal power to generate electricity

A barrage is built across the mouth of a bay. As the tide comes in, sluice-gates in the barrage are opened to let the sea flood into the bay. Once the tide outside has started to fall, the trapped water is allowed to flow back into the sea, but it has to pass through turbines built into the barrage. The turbines drive dynamos that generate electricity.

Gravity: Water Power
The gravitational attraction of the Earth pulls raindrops down to the surface and then back to the sea. Energy can be extracted from the water as it flows downhill. This can be used to turn machinery or to generate electricity.

Old-fashioned water mills use a wheel fitted with wooden paddles or odd-shaped buckets to convert the energy of flowing water into a turning motion that can drive machinery for such tasks as grinding corn and working bellows.

Using water power to generate electricity
In a hydro-electric power station (HEP station), large volumes of water are stored in a reservoir behind a dam across a mountain valley. When electricity is required, the water rushes downhill through a wide pipe and into a turbine in the power station. It then escapes to a river. The turbine is connected to a dynamo which generates electricity.

Wind Power
Winds are a free source of energy that have been exploited for at least three thousand years by …

There were once over 10,000 windmills across the UK. Most were used to pump water from low-lying land or to grind corn into flour.

Today windmills have a different purpose; they produce electricity. Single large wind turbines generate electricity to supply whole communities, e.g. Shetland Islands, Swaffham (Norfolk).

In some places wind turbines are grouped together and known as wind farms. They are built on exposed sites like the ridges of hills and mountains, or offshore. They supply electricity to the national grid for use all over the country.

Smaller wind turbines, often known as aero-generators, are used to charge batteries for storing energy for use on boats, navigation buoys, remote telephone boxes and even computers in schools.

Is there a working windmill, wind turbine or wind farm near you?

Can you arrange a visit?

What does it produce; flour, electricity, etc, or is it only a visitor attraction?

Who are its customers?

Wind Power Potential
The UK is one of the windiest counties in Europe. Land-based wind-power could generate up to 10% of the UK's electricity. This would require 38,000 wind-turbines. However it is highly unlikely these will ever be achieved, as there are concerns about the noise and visual pollution of wind-turbines in some rural environments. Offshore installations could possibly make up the shortfall and the present UK Government is committed to increasing this potential in the next few years.

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