Biofuels are fuels made from plant materials. These include biodiesel, made from plant oils, and bioethanol, made by fermenting sugar and wheat.
|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.|
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.
|Renewable source||Expensive to build|
|Cheap to run (no fuel costs)||Visual pollution (spoils the view)|
|No polluting gases produced||Noise pollution (very noisy)|
|Unreliable (depends on the strength of the wind)|
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:
|Renewable source||Visual pollution (spoils the view)|
|Cheap to run (no fuel costs)||Damage to the estuary habitats|
|No polluting gases produced||Damage to valley habitats by flooding|
|Very reliable||Can block access to ports for shipping|
|Can be switched on when needed||Trapped and rotting vegetation can produce greenhouse gases such as methane|
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.
The panels are fitted on a roof. Infrared radiation from the Sun shines through the glass lid and heats the water in the pipes.
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.
|Renewable source||Solar 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 produced||Unreliable 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|