Non renewable energy resources are the fossil fuels (coal, oil and natural gas) and nuclear       fuels (uranium and plutonium).    Fossil fuels release a lot of heat energy when they are burned.    The Earth’s supply of fossil fuels (coal, oil and gas) and of nuclear fuels is limited.    It will take millions of years to replace the fossil fuels we have used.    Most of the energy used to produce electricity comes from non-renewable fuels, mainly from       fossil fuels.  Generating electricity in a power station (Fuel: Fossil fuels)     Fossil fuels are burned in power stations, the heat released is used to heat water. The steam             produced is used to drive turbines. The turbines then drive generators which produce electricity.  Generating electricity in a power station (Nuclear Fuels: Uranium / Plutonium)    In a nuclear power station, the process of nuclear fission releases thermal energy that is used      to heat water. The steam produced is used to drive turbines. The turbines then drive the       generators which produce electricity.      Remember, nuclear fuel is not burned, it is used to heat water in a "heat exchanger".           More energy is released per kilogram from nuclear fuel than from fossil fuels.