There are different energy resources in the world and the amount of energy stored by them varies greatly. For example, the nuclear energy within 1 kg of uranium contains a very large amount of energy, but the gravitational potential energy stored by many thousands of tonnes of water held back by a dam contains less.
Renewable resources are replenished either by:
A non-renewable energy resource is one with a finite amount. It will eventually run out when all reserves have been used up.
The table below shows the main features of the most common energy resources used today.
|Energy resource||Energy store||Renewable?||Uses||Power output||Environmental impact|
|Fossil fuels (oil, coal and natural gases)||Chemical||Non-renewable||Transport, heating, electricity generation||High||Releases CO2 (causes global warming)|
|Nuclear fuels||Nuclear||Non-renewable||Electricity generation||Very high||Radioactive waste (needs to be disposed of safely)|
|Bio-fuel||Chemical||Renewable||Transport, heating, electricity generation||Medium||'Carbon neutral', so low impact|
|Wind||Kinetic||Renewable||Electricity generation||Very low||Takes up large areas that could be used for farming, some people say windmills spoil the view|
|Hydroelectricity||Gravitational potential||Renewable||Electricity generation||Medium||Local habitats are affected by the large areas that need to be flooded to build dams|
|Geothermal||Internal (thermal)||Renewable||Electricity generation, heating||Medium||Very low|
|Tides||Kinetic||Renewable||Electricity generation||Potentially very high, but hard to harness||Tidal barrages can block sewage which needs to go out to sea|
|Sun||Nuclear||Renewable||Electricity generation, heating||Dependent on the weather and only available during daylight||Very little|
|Water waves||Kinetic||Renewable||Electricity generation||Low||Very low|
Power stations that use fossil fuels or nuclear fuel are very reliable sources of energy. These two types of station provide much of the country’s electricity. They operate almost continuously. When additional power is needed, gas power stations are usually used because they will come on very quickly and start generating electricity almost immediately.
The fuel for nuclear power stations is relatively cheap, but the power stations themselves are expensive to build. It is also very expensive to dismantle, or decommission, old nuclear power stations at the end of their useful life and the highly radioactive waste needs to be stored for millions of years before the natural activity will reduce to a safe level.
Water power, eg tidal and hydroelectricity, is reliable and predictable because of the Moon causing the tides and rainfall filling reservoirs. They can also be used to supply additional demand. But many of the renewable sources are unreliable, including wind and solar energy, and cannot respond to increased demand - sunny and windy weather cannot be guaranteed.
Renewable resources have no fuel costs, but the equipment used is expensive to build.