Fuels (Oxford AQA IGCSE Physics)
Revision Note
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
Power plant | Average efficiency |
---|---|
Nuclear | 32% - 42 % |
Fossil fuel | 33 % - 45 % |
Hydro | 80 % - 90 % |
Wind farms | 25 % - 45 % |
Solar farms | 15 % - 25 % |
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