Energy resources

Energy resources can be broadly divided into renewable and non-renewable types.

Non-renewable

• Fossil fuels (coal, oil and natural gas) and nuclear fuel are non-renewable because they are used up far faster than they form and so cannot be replaced within a human lifetime.

Renewable

• Biofuels
• Hydroelectric
• Wave
• Tidal
• Geothermal
• Solar
• Wind

Renewable resources are continuously replenished by natural processes, so they will not run out.

Power Stations That Burn Fuel

Most power stations that burn fuel follow the same energy transfer chain:

1. The fuel is burned to heat water in a boiler and produce steam.
2. The steam drives (turns) a turbine.
3. The turbine spins a generator, which produces electrical energy.

Hydroelectric, Tidal, Wave and Wind Power

• Use moving water or moving air to drive turbines directly, without burning fuel or using a boiler.

Solar Cells

• Convert light from the Sun directly into electrical energy, with no moving parts.

Solar Panels

• Use infrared (and other) radiation from the Sun to heat water directly.

Each resource has advantages and disadvantages, which are assessed in terms of renewability, availability, reliability, scale, and environmental impact.

Radiation from the Sun is the main source of energy for all of these resources except geothermal, nuclear, and tidal.

Nuclear Fusion

• The Sun itself releases energy by nuclear fusion, in which light nuclei join (fuse) together to form heavier nuclei.
• Research continues into harnessing fusion on Earth for large-scale electrical generation, but the extreme temperatures and pressures required have not yet been sustained commercially.

Efficiency

Efficiency quantifies how effectively a device transfers energy into useful forms. The same relationship can be written using power instead of energy:

efficiency = (useful energy output / total energy input) × 100% efficiency = (useful power output / total power input) × 100%

No device achieves 100% efficiency because some energy is always dissipated to non-useful (thermal) stores, usually heating the surroundings.