Fuels (Oxford AQA IGCSE Combined Science Double Award)

Fuels

• Fuels are a useful store of energy

• Different fuels are suitable for different purposes and are selected based on a range of factors

  • Ease of storage

  • Energy content

  • Safety

• The three main uses of fuels are:

  • Transport

  • Heating

  • Generating electricity

Transport

• The majority of vehicles in the world are powered by petroleum products such as petrol, diesel and kerosene

  • These resources all originate from crude oil, which is a fossil fuel

  • Liquid petroleum products are easy to store in fuel tanks (such as in petrol stations and vehicles)

  • The energy content of fossil fuels is approximately 30 MJ per kilogram

  • Liquid petroleum products are relatively safe to store and use

Heating

• The majority of heating systems run on fossil fuels

  • Gas central heating systems are the most common, with a gas boiler that heats water through a system of pipes and radiators throughout the building

  • Boilers can also be powered by oil or biofuels

  • Open fireplaces burn wood or coal

• Electric heaters run on electricity

• Log burners burn wood

• Bottled gas can also be used in portable heaters

  • Bottled gas is either propane or butane which are also produced from fossil fuels

Electricity Generation

• Electricity is generated by turning a turbine which turns a generator coil through a magnetic field

  • This induces a potential difference so that a current can flow

• The current is then distributed across the country using a series of cables called The National Grid

• The majority of electricity generation globally uses fossil fuels

  • Burning fossil fuels releases carbon dioxide and sulphur dioxide into the atmosphere

  • Carbon dioxide is a greenhouse gas which contributes to global warming

  • Sulphur dioxide is acidic when dissolved in water and causes acid rain

• Increasingly, nuclear power and renewable energy resources are being used to generate electricity

  • Nuclear energy comes from the fission of uranium or plutonium

  • The energy content of nuclear fuel is approximately 300 000 MJ per kilogram

  • No pollutants are released in fission reactions

  • However, nuclear power plants create radioactive waste that has to be safely disposed of

  • Nuclear waste is buried underground and must remain there for thousands of years

Global electricity generation 2021

Fuel Efficiency

• When a fuel is used, some of the energy is transferred to the surroundings

  • This energy is wasted

• Some fuels are more efficient than others

• Some methods of electricity generation are more efficient than others

• The energy content of nuclear fuel is 10,000 times greater than that of fossil fuels

  • Nuclear fuel releases 300 000 MJ per kg

  • Fossil fuel releases 30 MJ per kg

• Nuclear fission is also almost 8000 times more efficient than fossil fuel combustion

  • Less energy is dissipated to the surroundings in fission than in combustion

  • Therefore, more of the energy released in the reaction is used to generate electricity

• Different types of power plants run at different efficiencies

  • Energy will be dissipated to the surroundings at each phase in the electricity generation process, so the longer the process the more energy is wasted

Average Efficiency of Different Types of Power Plants