Where does energy comes from?

There are different types of energy resources in the world and the amount of energy stored by them varies greatly. For example, 1 kg of uranium contains a very large amount of nuclear energy, but the gravitational potential energy stored by many thousands of tonnes of water held back by a dam contains less.

Renewable or non-renewable?

A renewable energy resource is one that is being (or can be) replenished as it is used.

Renewable resources are replenished either by:

  • human action - eg trees cut down for biofuel are replaced by planting new trees
  • natural processes - eg water let through a dam for hydroelectricity is replaced through the water cycle

A non-renewable energy resource is one with a finite amount. It will eventually run out when all reserves have been used up.

Different energy resources

Nine different energy resources, fossil fuels, nuclear, bio, wind, hydroelectric, geothermal, tides, sun, water waves; illustrated around a main label.

The table below shows the main features of the most common energy resources used today.

Energy resourceEnergy storeRenewable or non-renewableUsesPower outputImpact on environment
Fossil fuels (oil, coal and natural gases)ChemicalNon-renewableTransport, heating and electricity generationHighReleases CO2 and SO2 (causing global warming and acid rain)
Nuclear fuelsNuclearNon-renewableElectricity generationVery highRadioactive waste (needs to be disposed of safely)
BiofuelChemicalRenewableTransport, heating and electricity generationMediumCarbon neutral so low impact
WindKineticRenewableElectricity generationVery lowTake up large areas that could be used for farming - some people say windmills spoil the view
HydroelectricityGravitational potentialRenewableElectricity generationMediumLocal habitats are affected by the large areas that need to be flooded to build dams
GeothermalInternal (thermal)RenewableElectricity generation and heatingMediumVery low
TidesKineticRenewableElectricity generationPotentially very high, but hard to harnessBuilding barrages has a significant impact on migratory fish and habitats of sea birds - it can also hinder coastal shipping movements
SunNuclearRenewableElectricity generation and heatingDependant on the weather and only available during daylightVery low
Water wavesKineticRenewableElectricity generationLowVery low

Comparing resources

Power stations that use fossil fuels or nuclear fuel are very reliable sources of energy. These two types of stations 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 are reliable and predictable because of the Moon causing the tides and rainfall filling reservoirs. These two 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.