Electricity can be generated from wind, water, geothermal and solar energy. These energy resources are renewable. All resources have advantages and disadvantages.
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.
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.
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.
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.