GCSE Design and Technology AQA (8552) Unit 2: Energy Generation

Fossil Fuels

• Fossil fuels are formed from the fossilised remains of plants and animals over millions of years
• Coal, oil and gas are extracted through mining and drilling
• Fossil fuels are considered a finite resource as they take a few million years to form, and humans are using them significantly faster than the environment can replace.
• They are relied upon for power generation because they are effective and they are a cheap source of energy
• Extraction of fossil fuels can disrupt the environment, especially open cast mining.

Energy Generation

• Fossil fuels can be burned to superheat water under pressure, which in turn, drives turbines
• Chemical energy from fuel is turned into heat, in the form of superheated steam
• The steam drives turbines, converting heat to kinetic energy
• Kinetic energy drives the shaft which spins an electricity generator, converting kinetic energy to electricity
• The electrical energy is transferred to the National Grid by pylons, where it is used.

Fracking

• Fracking involves drilling into layers of shale rock deep in the earth to release pockets of gas
• Water, sand and chemicals are injected into a well in order to force gas up
• The water pressure creates fissures in the rock which open up areas with gas
• Sand stops the fissures from closing up, and allow the gas to flow into the well pipe
• Chemicals can contaminate nearby water tables used for drinking, and have done in the past
• People can become ill from drinking contaminated water

Renewable Energy Sources

• Renewable alternatives to fossil fuels include wind, solar, tidal, biomass and hydroelectric
• These are classified as renewable as they are replaced easily without much damage to the environment

Wind Turbines

For:

• Low maintenance
• Clean energy
• Higher winter output
• Low cost energy

Against:

• Only works when windy
• Eyesore to some
• Hazard to birds
• Noise

Solar Energy

• The Sun produces a constant stream of solar energy that reaches Earth
• In just one hour it provides enough energy to power the world for one year

Photovoltaic (PV) Cells

• Light photons hit the PV cell which allows electrons to flow creating an electric current
• PV cells are used for solar panels.

Advantages:

• Low maintenance
• Clean energy
• Relatively low-cost

Disadvantages:

• Seasonal fluctuations
• No power generated at night
• Complex positioning issues

Tidal Energy

• The rise and fall of the tide forces water through turbines which drive generators to produce electricity

Advantages:

• Clean energy
• High efficiency
• Low maintenence

Disadvantages:

• Construction is expensive
• Very few suitable locations
• Low power output compared to others

Hydroelectric Power (HEP)

• Hydroelectric power is a very reliable and controllable energy source
• The set-up costs are financially and environmentally expensive
• Vast areas need to be flooded to create reservoirs
• People who live locally will have to be moved to a safer location, and those who are not in danger of flooding may complain of noise

Biofuel and Biomass

• Biofuel and biomass are created from organic matter which is burned to generate power
• Biomass fuels include food and farm waste, compost and wood chips or compressed pellets
• Biomass is considered to be carbon neutral as the carbon dioxide released when burnt are equivelant to the amount of carbon dioxide absorbed by the plants used to create biofuels

Nuclear Power

• Nuclear power accounts for over 11% of the world's electricity
• This is not a renewable energy source as uranium supplies are limited as fossil fuels
• Nuclear power provides an abundant, reliable supply of clean energy
• It is unpopular with some campaigners as the nuclear waste created is dangerous and there is a risk of major catastrophe like the Fukushima disaster in Japan