There are different energy sources in the world and the stores of energy associated with them can contain different amounts of energy. For example, nuclear fuel stores can contain very large amounts of energy, while hydroelectric stores tend to contain much less energy.
Some energy sources are renewable, which means they can be replenished and will not run out. Other energy sources are non-renewable, which means they will eventually run out when all their reserves have been depleted (used up).
The table below shows the main features of the most common energy sources used today.
|Energy resource||Energy store||Renewable or non-renewable||Uses||Power output||Impact on environment|
|Fossil fuels (oil, coal and natural gases)||Chemical||Non- renewable||Transport, heating, electricity generation||High||Releases CO2, which contributes to global warming.|
|Nuclear fuels||Nuclear||Non-renewable||Electricity generation||Very high||Produces radioactive waste which needs to be disposed of safely.|
|Biofuel||Chemical||Renewable||Transport, heating, electricity generation||Medium||'Carbon neutral' - little or no effect on the environment. Although growing biofuels can take up land that could be used for farming.|
|Wind||Kinetic||Renewable||Electricity generation||Very low||Turbines take up large areas that could be used for farming. Some people say windmills spoil the view.|
|Hydroelectricity||Gravity||Renewable||Electricity generation||Medium||Local habitats are affected by the large areas that need to be flooded to build dams.|
|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 and heating||Dependant on the weather and only available during daylight||Impact on environment is very low.|