Energy from Fuels (Cambridge (CIE) O Level Physics): Revision Note

Fossil Fuels

• Fossil fuels are:

  • Coal

  • Natural gas (mostly methane) which is used in domestic boilers and cookers

  • Crude oil which is refined into petrol, diesel, and other fuels

Three Main Fossil Fuels

Fossil fuels: coal, oil and natural gas

• Fossil fuels are formed from the remains of plants and animals 

• Chemical energy stored in fossil fuels originally came from sunlight

  • Energy from the sun was transferred to the chemical energy store of plants by photosynthesis (plants use energy from sunlight to make food)

  • Animals ate the plants and the energy was transferred to their chemical store

Advantages

• The current systems of transport and electricity generation rely heavily on fossil fuels which are generally readily available on a daily basis

• In the past fossil fuels have been reliable for large scale energy production although this is changing as supplies deplete and prices rise

Disadvantages

• It takes millions of years for fossil fuels to form

  • This is why they are considered to be a non-renewable energy resource

  • The increasing demand for a decreasing supply causes prices to increase

  • Fossil fuels are predicted to completely run out within the next 200 years 

• Burning fossil fuels pollutes the atmosphere with harmful gases such as:

  • Carbon dioxide which contributes to the greenhouse effect

  • Sulphur dioxide which produces acid rain

  • Both carbon and sulphur can be captured upon burning preventing it from being released into the atmosphere but this is expensive to do

       

Uses of Fossil Fuels

• Fossil fuels are used for:

  • Transport

  • Generating electricity

  • Heating 

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

• A growing number of vehicles are now being powered by electricity

  • The advantage of this is that while the vehicle is being driven, it produces zero carbon emissions

  • The disadvantage is that when the vehicle is being charged, it is connected to the National Grid, which currently uses a combination of renewable and non-renewable energy sources

Electricity Generation

• Fossil fuels, such as coal and oil, are used to produce energy on-demand when energy is needed

  • This is done by burning the materials when the energy is required

  • When coal is burned, energy is released from its chemical store

• This is used to boil water creating steam

• Steam is forced around the system and this turns a turbine

• The turbine turns coils in a magnetic field in the generator

  • This generates electricity

• The electricity is transferred through a step-up transformer and is carried out of the system by electrical lines

• The steam within the turbine will cool and condense and then be pumped back into the boiler to repeat the process

A coal-fired power station

Electricity generation in a coal-fired power station

• Electricity plays a bigger role in people's lives than ever before

  • With almost 8 billion people in the world, this means the demand for electricity is extremely high

  • To keep up with this demand, a combination of all the energy resources available is needed

• On the downside, the majority (84%) of the world's energy is still produced by non-renewable, carbon-emitting sources

  • This has an enormous negative impact on the environment

  • Currently, scientists are working hard to develop more and more efficient ways to produce electricity using more carbon-neutral energy resources

Pie chart of global energy consumption

Percentage of renewable and non-renewable energy consumption in 2019

Heating

• Most homes in cold countries are fitted with central heating systems

  • These utilise natural gas in order to heat up water which can be pumped around radiators throughout the home

Bio Fuels

• Biofuels are made from plant matter

  • Energy from sunlight is transferred to the chemical store of plants

• Ethanol or methane can be produced and used in place of fossil fuels

  • However, they have only half the energy density of fossil fuels

Advantages

• Biofuel is a renewable resource

• Some vehicles can be powered by biofuel rather than using fossil fuels

• Biofuel is considered to be carbon neutral

• No sulphur dioxide is produced 

Disadvantages

• Crops of biofuel producing plants must be grown which takes time

  • Growing the crops takes a lot of land, and takes resources needed for food production

• Burning biofuels releases carbon dioxide into the atmosphere

  • It is considered carbon neutral because plants take in carbon dioxide when they photosynthesise

Cycle of Carbon used for Biofuel

Plants take in carbon dioxide during photosynthesis, but carbon dioxide is released back into the atmosphere when biofuels are burned

Nuclear Fuel

• Energy stored in the nucleus of atoms can be released when the nucleus is broken in two

  • This is known as nuclear fission

Process of Nuclear Fission

A large nucleus is broken into two smaller nuclei energy is released

• Nuclear power stations use fission reactions to heat water, to turn turbines to generate electricity

Advantages

• No pollution released into atmosphere

• Nuclear reactors are perfectly safe as long as they are functioning properly

  • Stringent checks must be routinely carried out and rigorous safety procedures followed

• Nuclear power stations can generate electricity reliably on a large scale which is available as needed

• There are extensive reserves of fissionable atoms

• A large amount of power is produced from a small amount of source 

Disadvantages 

• Uranium ore found in the ground is used for fission reactions and since there is a finite supply

  • Nuclear power is a non-renewable resource

• Nuclear fuels produce radioactive waste

  • Radioactive waste needs to be stored for thousands of years

  • Safe ways of storing radioactive waste is expensive

• If an accident occurs at a nuclear reactor, radioactive waste can leak out and spread over large areas and cause serious, long term damage to people and objects