Water energy

Like the wind, water can be used to drive turbines directly. There are several ways that water can be used, including waves, tides and falling water in hydroelectric power schemes.

Wave

The water in the sea rises and falls because of waves on the surface. Wave machines use the kinetic energy in this movement to drive electricity generators.

Tides

Huge amounts of water move in and out of river mouths each day because of the tides. A tidal barrage is a barrier built over a river estuary to make use of the kinetic energy in the moving water. The barrage contains electricity generators, which are driven by the water rushing through tubes in the barrage.

Hydroelectric power

Like tidal barrages, hydroelectric power (HEP) stations use the kinetic energy in moving water. Often, the water comes from behind a dam built across a river valley. The water high up behind the dam contains gravitational potential energy. This is transferred to kinetic energy as the water rushes down through tubes inside the dam. The moving water drives electrical generators, which may be built inside the dam.

Advantages

• Water power in its various forms is a renewable energy resource and there are no fuel costs.
• No harmful polluting gases are produced.
• Tidal barrages and hydroelectric power stations are very reliable and can be easily switched on.

Disadvantages

• It has been difficult to scale up the designs for wave machines to produce large amounts of electricity.
• Tidal barrages destroy the habitat of estuary species, including wading birds.
• Hydroelectricity dams flood farmland and push people from their homes.
• The rotting vegetation underwater releases methane, which is a greenhouse gas.