IGCSE Physics / Energy resources and electricity generation
Wind and water power
Edexcel International GCSE Physics (4PH1), chapter 17: Energy resources and electricity generation, specification point 4.18P. Free lesson.
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Wind and water power transfer energy from moving air or water to a generator. Their output depends on the weather and on having a suitable location.
How a wind turbine transfers energy
Moving air has energy in its kinetic store. It pushes the blades, transferring energy mechanically so they spin. The blades turn the generator, which transfers energy electrically. A wind turbine needs no fuel or steam.
How a hydroelectric dam transfers energy
Water stored high up behind a dam has energy in its gravitational store because it is high up and still. When released, it flows down through pipes. Its energy transfers to the water's kinetic store, then mechanically to the turbine as the water pushes its blades. The turbine turns the generator, which transfers energy electrically.
How tidal barrages and wave power work
A tidal barrage is a dam across an estuary, where a river meets the sea. At high tide, water is trapped behind it and then released through turbines. Wave power uses floating machines near the coast. Waves move parts of the machine up and down to drive a generator. A tidal barrage starts with the gravitational store of trapped water. Tides are predictable and come in and go out about twice a day. Wave power starts with the kinetic store of the waves. Waves depend on the wind, so they are less reliable. Both need the right kind of coast, so they suit only a few places.
Why output depends on weather and place
Wind, hydroelectric and tidal power cannot be built just anywhere. Some also depend on the weather, so they cannot always provide electricity when it is needed. Wind: turbines produce no output when there is no wind and must be stopped in storms. Wind farms need open, windy hills or a site at sea. Hydroelectric: dams need rain to refill them and need a river valley that can be flooded. Tidal: tides are not affected by the weather, but a barrage needs an estuary with big tides. Wind and waves depend on the weather. All these methods need the right place, and wind cannot be switched…
Why wind cannot supply electricity all the time
Wind turbines need wind to keep their blades turning, but the wind does not always blow. Very strong winds also mean turbines must be stopped, so their output depends on the weather and cannot be matched to demand.