Fossil fuels
Fossil fuels include coal, oil and natural gas. They were formed from the remains of living organisms millions of years ago and they release heat energy when they are burned. They are non-renewable. They have chemical energy stored within them.
About three-quarters of the electricity generated in the UK comes from power stations fuelled by fossil fuels. This diagram shows an energy transfer diagram for the generation of electricity from a fossil fuel such as coal.
Advantages of using fossil fuels
- At the moment, fossil fuels are relatively cheap and easy to obtain. This may not always be the case.
- Much of our infrastructure is designed to run using fossil fuels.
Disadvantages of using fossil fuels
- Fossil fuels are non-renewable energy resources. Their supply is limited and they will eventually run out whereas fuels such as wood can be renewed endlessly.
- Coal and oil release sulfur dioxide gas when they burn, which causes breathing problems for living creatures and contributes to acid rain.
- Fossil fuels release carbon dioxide when they burn, which adds to the greenhouse effect and increases global warming. Of the three fossil fuels, for a given amount of energy released, coal produces the most carbon dioxide and natural gas produces the least.
Carbon capture
Carbon capture and storage is a way to prevent carbon dioxide building up in the atmosphere. It is a rapidly evolving technology that involves separating carbon dioxide from waste gases. The carbon dioxide is then stored underground, for example in old oil or gas fields such as those found under the North Sea.
Nuclear power
The main nuclear fuels are uranium and plutonium. In a nuclear power station, nuclear fuel undergoes a controlled chain reaction in the reactor to produce heat - nuclear energy is converted to heat energy:
- heat is used to change water into steam in the boiler
- the steam drives the turbine (heat to kinetic energy)
- this drives the generator to produce electricity - kinetic to electrical energy
Cross-section of a nuclear reactor
Nuclear and geothermal energy are the only energy resources that do not come from the Sun.
Advantages
- Unlike fossil fuels, nuclear fuels do not produce carbon dioxide or sulfur dioxide.
- 1 kg of nuclear fuel produces millions of times more energy than 1 kg of coal.
Disadvantages
- Like fossil fuels, nuclear fuels are non-renewable energy resources.
- Although modern reactor designs are extremely safe, if there is an accident, large amounts of radioactive material could be released into the environment
- Nuclear waste remains radioactive and is hazardous to health for thousands of years, so it must be stored safely.
This waste material can never be used to make a 'nuclear bomb'. It is the fission fragments from a nuclear chain reaction and not fissionable itself.
