National and global energy resources

Physics · Energy. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.

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The idea

We use energy resources for three main things: transport, generating electricity and heating. The resources are fossil fuels (coal, oil, gas), nuclear fuel, bio-fuel, wind, hydro-electricity, geothermal, tides, the Sun and water waves.

A renewable resource is replaced as fast as it is used, so it will not run out. A non-renewable resource is used faster than it is replaced, so it will run out one day. Fossil fuels and nuclear fuel are non-renewable. All the others are renewable.

To compare resources, think about reliability (can it supply energy whenever it is needed?) and the effect on the environment. Cost and politics also affect which resources a country uses.

Rules to remember

Non-renewable: coal, oil, gas, nuclear fuel. Renewable: bio-fuel, wind, hydro-electricity, geothermal, tides, the Sun, water waves
Burning fossil fuels releases carbon dioxide, which contributes to global warming
Nuclear power releases no carbon dioxide while generating, but leaves radioactive waste that must be stored safely for a very long time
Wind, the Sun and waves depend on the weather, so they are not reliable
Tides are not constant but they are predictable; hydro-electricity can be switched on quickly when needed
Geothermal energy comes from hot rocks underground, heated by the decay of radioactive elements
Most road transport uses petrol and diesel, which are made from oil

Common mistake

Students say nuclear fuel is renewable because it gives out no carbon dioxide. Renewable only means the resource is replaced as it is used; uranium is not, so nuclear fuel is non-renewable.

Worked example

A town wants renewable electricity that it can count on during a calm winter night. Which is the best choice: solar cells, wind turbines or a hydro-electric dam?

All three are renewable, so compare how reliable they are.
Solar cells give no output at night, and wind turbines give no output when the air is calm.
A dam stores water behind it, so the water can be released through the turbines at any time.

Answer: The hydro-electric dam, because its output does not depend on the weather at that moment.

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