P1.4 Methods we use to generate electricity

The majority of the electricity we use is generated in power stations.

Process

1. Burning fuel which give off heat energy. The heat energy is used to heat water in the boiler. This produces steam
2.The steam turns a turbine
3. The turbine drives a generator
4. The generator generates electricity

Most fuels used in power stations are non-renewable, these include: Coal, Oil, Gasand Nuclear.

One renewable fuel which can be used in power stations is biofuel. Examples include: methane (manure), ethanol (fermented sugar cane), straw and woodchip.

Biofuels are carbon-neutral. This is because the CO2 released when burnt is equal to the amount taken in while growing.

When coal, oil and gas are burnt they produce CO2. This is a greenhouse gas, contributes to global warming and climate change. 

When Coal is burnt it produces sulphur dioxide (SO2) which causes acid rain.
Gas fired power stations have an advantage over oil and coal in that they have avery quick start up time.

Carbon Capture and Storage is a way to prevent carbon dioxide building up in the atmosphere. 

How do we get energy from the nucleus?

The fuel used is either Uranium or Plutonium. The nucleus is unstable because it isextremely large. When a slow moving neutron is absorbed by the nucleus it causes the nucleus to split into two smaller nuclei. This is called nuclear fission.

These neutrons will repeat the process

Nuclear reactors use Uranium or Plutonium to generate heat and turn water into steam. The Uranium is stored in sealed cans in the reactor core. Uranium has an unstable nucleus which can split into two smaller nuclei releasing energy, this is nuclear fission.

• The core of the reactor becomes very hot and this heat energy is transferred to a fluid (the 'coolant') which is pumped through the core 
• The coolant is very hot when it leaves the core and flow to a heat exchanger.
• In the heat exchanger, the heat energy from the coolant is used to turn water into steam
• The steam drives turbines that turn electricity generators

Fossil Fuels

Fuel: Oil, Coal, Natural Gas
Energy released per kg of fuel: 100 kWh
Waste: Non-Radioactive Waste
Pollution: CO2 given off causes global warming. SO2 given off by Coal causes Acid Rain
Reliability: Yes

Nuclear Power

Fuel: Uranium, Plutonium
Energy released per kg of fuel: 1,000,000 kWh
Waste: Radioactive Waste - needs storing safely for many years
Pollution: None - energy released without any burning
Reliability: Yes

The National Grid is a network of cables and transformers that distributes electricity to our homes from distant power stations and renewable energy generators.

A surge in demand is caused for example by a large amount of people that put their kettles on after a popular TV show.

During the night when people are asleep there will be a very low demand because lights/TVs are off and less electricity is used.

The term start-up time means how long it will take power stations to generate electricity.They require a short start-up time.

The National Grid copes with a surge in demand by using pump storage power stations or by using electricity generated by power stations in other countries. When there is a surge in demand the water from the upper lake travels down the pipe, to the turbine, to generate lots of electricity quickly to cope with the surge in demand.

When there is a low demand then water is pumped from the lower lake back to the top.

The National Grid is a network of power stations and cabling that carries electricity around the country.

Step up transformers increase the voltage which means the current can be low. This means that less heat is lost as the current passes through the cable making the National Grid more efficient.

Step down transformers decrease the voltage so that it's safe to use in homes.

Cables - Underground vs. Overhead

Underground - hard to fix, can conduct underground minerals, may harm animals that live underground.

Overhead - spoiling the landscape

Fossil Fuels
Initial Energy: Chemical
Advantages: Reliable, proven technology, no radioactive waste
Disadvantages: produces greenhouse gases, coal causes acid rain, non-renewable, when burned causes global warming

Nuclear
Initial Energy: Nuclear
Advantages: No greenhouse gases, produces more energy, reliable, lasts longer than fossil fuels
Disadvantages: Non-renewable, expensive to get rid of waste, produces Radio-Active waste, stored underground in geologically stable sights

Wind
Initial Energy: Kinetic
Advantages: Renewable, no fuel costs, no greenhouse gases, put in isolated places
Disadvantages: Not always windy

Wave
Initial Energy: Kinetic
Advantages: Renewable, free fuel, no greenhouse gases, there are always waves
Disadvantages: damaged by stormy seas, hard to repair, unreliable, effects boats and marine life

Solar
Initial Energy: Light
Advantages: Renewable, no greenhouse gases, free fuel
Disadvantages: Not always sunny and large areas needed, unreliable, expensive

Tidal
Initial Energy: Gravitational Potential
Advantages: Renewable, no greenhouse gases, free fuel, reliable
Disadvantages: Tide only comes in twice a day, damage sea life, eyesore, stops boats and shipping

Hydroelectric
Initial Energy: Gravitational Potential
Advantages: Renewable, reliable, no greenhouse gases, free fuel, quick start up time, can store energy until needed, no CO2 produced
Disadvantages: damages environment, disrupt river life, flood reservoir, impact of environment and local community

Biofuel
Initial Energy: Chemical
Advantages: Renewable, no greenhouse gases, free fuel, carbon neutral
Disadvantages: only small scale, takes up land, smell

Geothermal
Initial Energy: Nuclear
Advantages: Renewable, no greenhouse gases, free fuel
Disadvantages: Only works in certain places