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The energy resources in our environment can be classified as renewable or non renewable.
Non-renewable resources take millions of years to be made and replaced. Oil, coal and gas are examples of non-renewable resources that are being used more quickly than they are being formed. These resources are therefore limited in supply - that is there is not enough to continue using them indefinitely. In fact we are able to calculate an estimate for the time left using these reserves. The estimations of time vary around the world as developed countries on average use more fossil fuels and at a faster rate. In response to the limitations on our use of fossil fuels there has been more research on alternative or renewable energy sources to replace the traditional oil, coal and gas fuels.
Renewable sources of energy are those that can be made and replaced quickly such as solar, hydro and wind energy. The time it takes for the energy to be replaced varies from seconds for solar, hours for wind and up to months or years for crops or plantation forests. The continual replacement of these energy sources means that for human use they are unlimited in supply.
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