Most of the energy we use is obtained from fossil fuels – coal, oil and natural gas.
Once supplies of these fuels are have been used up they cannot be replaced – they are non-renewable.
At current levels of use, oil and gas supplies will last for about another 40 years, and coal supplies for about a further 300 years. The development of renewable sources of energy is, therefore, becoming increasingly important.
The wind is used to turn windmill-like turbines which generate electricity directly from the rotating motion of their blades. Modern wind turbines are very efficient but you would need several thousand to equal the generating capacity of a modern fossil-fuel power station.
The motion of waves can be used to move large floats and generate electricity. A very large number of floats is needed to produce a significant amount of electricity.
Dams on tidal estuaries trap the water at high tide. When the water is allowed to flow back at low tide, it can turn turbines to drive electrical generators. This obviously limits the use of the estuary.
Dams can be used to store water which is allowed to fall in a controlled way that generates electricity. This is particularly useful in mountainous regions for generating hydroelectric power. When demand for electricity is low, spare electricity from a nuclear power station (which has to be run continuously) can be used to pump water back up into the high reservoir for use in times of high demand.
Plants use energy from the Sun in photosynthesis. Plant material can then be used as a biomass fuel – either directly by burning it or indirectly. A good example of indirect use is to ferment sugar cane to make ethanol, which is then used as an alternative to petrol. Waste plant material can be used in ‘biodigesters’ to produce methane gas. The methane is then used as a fuel.
Geothermal power is obtained using the heat of the Earth. In certain parts of the world, water forms hot springs which can be used directly for heating. Water can also be pumped deep into the ground to be heated.
Solar power is energy from the Sun, which itself is powered by nuclear fusion reactions (where the small nuclei of hydrogen atoms join to make larger nuclei that are, in fact, helium and an enormous amount of energy is released.
The Sun’s energy is trapped by solar panels and transferred into electrical energy or, as with domestic solar panels, is used to heat water. The cost of installing solar panels is high, but in sunny countries, solar power is of increasing importance.