Comparing renewable sources of energy

Energy from plants

Biofuels are fuels made from plant materials. These include biodiesel, made from plant oils, and bioethanol, made by fermenting sugar and wheat.

Advantages and disadvantages of biofuel

Renewable source.Uses land that could be used to grow food.
Less carbon emissions. When burned, they release as much carbon as they absorbed during growth, although some carbon dioxide will be released during production, eg by the tractor.Needs a lot of labour.
Reduce our reliance on fossil fuels.Bioethanol cannot be used in cars without modifying the engine.

Energy from the wind

The process of farming wind as a reusable energy source

Humans have been taking advantage of the wind for thousands of years. Sailing ships and windmills are both examples of wind power.

Even though sailing ships are still used today, the major use of wind is to generate electricity using wind turbines.

The turbine consists of a generator in a nacelle at the top of a high tower. The wind turns the blades of the turbine and these, in turn, spin the generator.

Advantages and disadvantages of wind power

Renewable sourceExpensive to build
Cheap to run (no fuel costs)Visual pollution (spoils the view)
No polluting gases producedNoise pollution (very noisy)
Unreliable (depends on the strength of the wind)

Energy from falling water

Energy in the gravitational store of a body of water held above sea level can be used as the water is allowed to run down pipes containing turbines. There are two ways of doing this:


The process of farming water flow as a reusable energy source

  1. The Moon's gravitational pull lifts the level of the seas twice a day and this is the force that gives us tidal power.
  2. At high tide, the sea is trapped behind a barrage/dam.
  3. The water is allowed to run out through pipes that lead back to the sea.
  4. As the water runs through the pipes it spins turbines that are linked to generators.


The process of using gravity and water to generate electricity

  1. Water is held behind a dam in a lake or reservoir high up a mountain.
  2. Rivers or rainfall fills the reservoir.
  3. When energy is needed, the water is allowed to run down through pipes to another lake lower down the mountain.
  4. As the water runs through the pipes it spins turbines that are linked to generators.
  5. The water can be pumped back up during the night when electricity is cheaper.

Advantages and disadvantages of water power

Renewable sourceVisual pollution (spoils the view)
Cheap to run (no fuel costs)Damage to the estuary habitats
No polluting gases producedDamage to valley habitats by flooding
Very reliableCan block access to ports for shipping
Can be switched on when neededTrapped and rotting vegetation can produce greenhouse gases such as methane

Energy from the Sun

Solar panels absorb solar energy to heat water in a household system

All our energy comes from the Sun. The Sun warms the air and sets up convection currents that causes the wind. This evaporates water from seas and lakes to set up the water cycle to provide the rain that fills the reservoirs. We can also make use of the energy from the Sun directly using solar cells or solar panels.

Solar Panels

The panels are fitted on a roof. Infrared radiation from the Sun shines through the glass lid and heats the water in the pipes.

Solar cells

A solar cell is a circuit component that uses light from the Sun to generate electricity. Many calculators use solar cells, and many houses have panels on their roof. Space probes often use solar cells to generate the electricity they need.

Advantages and disadvantages of solar power

Renewable sourceSolar cells are not very efficient
Cheap to run (no fuel costs)It costs a lot of money to make them more efficient
No polluting gases producedUnreliable as it is not always sunny
Solar cells can generate electricity at the top of mountains when there is no connection to the National Grid