P1.4 Generating Electricity

Energy sources and Power stations

Non-renewable energy resources

• Coal
• Oil
• Gas 
• Nuclear fuels (Uranium & Plutonium)
• Coal, Oil & Gas are called the fossil fuels
• They will all run out one day
• They all do damage to the environment (CO2, SO2 and CO)

Energy source and Power stations

Renewable energy resources

• Wind
• Waves
• Tides
• Hydroelectric
• Solar
• Geothermal
• Biofuels
• These will never run out
• They cause less damage to the environment than non-renewables
• They don't provide as much energy as non-renewables
• Some of them don't work all the time because they depend on the weather and daylight

Energy sources and Power stations

Energy sources can be burned to drive turbines in Power station                                                                           

• The fuel is burned to heat water to produce steam
• The steam drives a turbine
• The turbine is joined to a generator. When the turbine turns, the generator produces electricity

Energy sources and Power stations

• Instead of burning fuel, a reaction called nuclear fission is used to heat water to make steam to drive turbines
• Nuclear power stations take the longest time of all the power stations to start up
• Natural gas power stations take the shortest time of all the fossil fuel power stations

Renewable Energy Sources

Wind power - arrays of turbines

• Wind turbines are usually put up in windy places like moors or coasts
• Electricity is generated directly from the wind - the wind turns the blades, which turn the generator inside the wind turbine
• The turbines do not release any harmful gases into the atmosphere. There are no waste materials made
• But they do cause visual pollution (spoil the view)
• The can be very noisy (if you are living nearby)
• They can harm/kill birdlife
• No electricity is made when the wind stops
• The start up costs are quite high (land and lots of turbines)
• No fuel costs
• Cheap to run
• Smaller tubines can be used to generate electricity on a smaller scale eg homes, offices

Renewable Energy Sources

Solar cells

• Solar cells generate electricity directly from sunlight
• There is no pollution when they are being used
• In sunny countries solar power is a very reliable source of energy, but only in the daytime
• The set up costs are high, but the energy is free
• Running costs are almost nothing
• Solar power is a useful way to generate electricity in remote places which are not connected to mains supply eg road signs, parking meters
• It is often very difficult or too expensive to connect places that use solar panels to the National Grid. The connection cost is often much greater than the electricity they produce is worth.

Renewable Energy Sources

Hydroelectric Power uses falling water

• Water is trapped by a dam and is then allowed to fall through turbines. The turbines are coupled to a generator which turns to produce electricity
• No gases are released into the atmosphere when the electricity is generated
• No waste materials are produced
• There is visual pollution
• Hydroelectric power can produce electricity when it is needed eg when demand for electricity is high. Pump storage  power stations eg Dinorwig, Wales can be built which will use night time (cheaper) electricity to pump water to a reservoir. The water can then be used to turn a turbine when demand is suddenly high
• It is very reliable 
• Hydroelectric power stations are expensive to set up
• No fuel is needed, therefore running costs are low
• It can be a useful way to generate electricity on a small scale in remote areas

Renewable Energy Sources

Wave power - wave powered turbines

• As waves come in to the shore, their up and down motion can be used to drive a generator
• They do not release any harmful substances into the atmosphere or any other waste
• They do spoil the view
• They can be unreliable - depending on the wind
• The set up costs are high
• There are no fuel costs
• The running costs are very low
• Wave power is not usually used to provide energy on a large scale, but it can be very useful on small islands

Renewable Energy Sources

Tidal Barrages - Dams on river estuaries with turbines in them

• As the tide comes in it fills up the estuary and drives the turbines
• They do not produce any harmful waste
• They do not pollute the atmosphere
• They cause visual pollution
• They change and destroy the habitats of some wildlife
• Tides are reliable - they happen twice a day without fail, and always near to the predicted height
• The height of the tides is not always the same - lower tides will provide a lot less energy than higher tides
• The set up costs are quite high
• No fuel costs
• Very low running costs
• Tidal power can be used to generate electricity on a large scale

Renewable Energy Sources

Geothermal Energy - Heat from Underground

• In some volcanic areas, steam and hot water rise to the Earth's surface
• This steam can be used to drive a turbine which turns a generator
• No pollution
• No waste
• No effect on wildlife habitats

Biofuels - made from plant and waste

• Biofuels are burned to heat up water, produce steam and drive a turbine
• Crops like sugar cane can be fermented to produce ethanol or plant oils can be processed to produce biodiesel
• Biofuels like this are cheap and quick to make
• Small trees like willow and eucalyptus grow quickly and can be harvested regularly to be used as a biofuel 

Energy sources and the Environment

Non renewables are linked to Environmental problems:

• Coal, Oil and Gas release Carbon Dioxide (CO2) into the atmosphere when they are burned. All this CO2 adds to the greenhouse effect and contributes to global warming
• Burning coal and oil releases sulphur dioxide (SO2) which causes acid rain (harmful to plants and wildlife)
• Coal mining spoils the landscape, destroys wildlife habitats and creates visual pollution
• Oil spillages cause serious environmental problems affecting sea creatures and birds
• Nuclear power does not produce any harmful gases
• Nuclear waste is very dangerous/poisonous and is very difficult to store/dump
• The overall cost of nuclear power is high including setting up and decommissioning a nuclear power plant and dealing with waste
• Nuclear power always carries the resk of a major disaster. An explosion at a nuclear power plant can release lots of dangerous, radioactive material into the atmosphere eg Chernobyl

Energy sources and the Environment

Biofuels have their disadvantages too:

• Plants that grow to produce biofuels take in CO2 from the atmosphere as they grow
• When the biofuels are burned, this CO2 is re-released into the atmosphere
• So the overall amount of CO2 in the atmosphere stays the same
• In some regions, large areas of forest have been cleared to make room to grow biofuels, which causes lots of spieces to lose their natural habitats
• Rotting and burning of the plants from these forests also releases CO2 and methane gases

Carbon capture can reduce the impact of CO2

• Carbon capture and storage (CCS) is used to reduce the amount of CO2 released into the atmosphere and help reduce the greenhouse effect
• CCS works by collecting the CO2 from power stations before it is released into the atmosphere
• The captured CO2 can then be pumped into empty gas fields and oil fields
• CCS is new technology that's developing quickly

Electricity and the National Grid

• The National Grid takes electricity takes electricity from power stations to consumers
• A high voltage is used to reduce current and heat loss from cables
• Voltage is boosted up at the power station in order to keep the current low
• Step up transformers are used to boost the voltage to 400 000V
• Step down transformers reduce the voltage to safe levels near the consumer