Physics - Generating electricity Flashcards
Give
three examples of renewable energy technologies
and three non-renewable
Renewable:
hydroelectric
wind power
wave power
tidal power
waste
solar
wood / biomass
Non-renewable:
fossil fuels (oil, gas, coal)
nuclear
What are the advantages and disadvantages of
nuclear energy
Advantages
No CO2, reliable, generate large amounts of electricity and uses small amount of fuel.
Disadvantages
Radioactive waste produced which needs to be stored for a long time, high commissioning and decommissioning costs and risks with terrorism.
What are the advantages and disadvantages of
fossil fuel energy
Advantages:
Generate large amounts of electricity. Can be built in many locations.
Disadvantages:
CO2 (global warming) and SO2 (acid rain for coal) produced, transport of fuel is difficult and getting a secure supply.
What are the advantages and disadvantages of
hydroelectric energy
Advantages:
No CO2, generate large amounts of electricity, no fuel costs and start up time is short.
Disadvantages:
Need to flood large area of land, destroy wildlife habitats and building of large dams.
What are the advantages and disadvantages of
wind energy
Advantages:
No fuel, no air pollution.
Disadvantages:
Eye-sore, unreliable if not windy, generate small amount of electricity.
What are the advantages and disadvantages of
Solar energy
Advantages:
Cheap to install on buildings, fairly reliable, no air pollution.
Disadvantages:
Need a lot of panels to generate large amount of electricity and does not work at night.
What are the advantages and disadvantages of
Geothermal energy
Advantages:
No air pollution, reliable
Disadvantages:
Ground source heating needs large area.
What are the advantages and disadvantages of
biomass energy
Advantages:
Can generate large amount of electricity and carbon neutral.
Disadvantages:
Large areas of land needed to grow trees and plants.
What are the advantages and disadvantages of
wave and tidal energy
Advantages:
Tidal predictable. No air pollution. Tidal could generate large amounts of electricity
Disadvantages:
Wave more unreliable as it depends on the wind. Tidal could cause loss of wildlife areas.
Explain how electricity is generated in a
fossil fuel power station (e.g. coal)
Fuel is burnt, releasing heat
The heat is used to warm up water in a boiler, turning it to steam
The steam turns the blades of a turbine.
The turbine is connected to a generator which then produces electricity.
Explain the purpose and the features of a Sankey diagram
Sankey diagrams summarise all the energy transfers taking place in a process.
They are drawn to scale - the thicker the line or arrow, the greater the amount of energy involved.
Look at the Sankey diagram below, which is of an old fashioned light-bulb (a ‘filament’ bulb).
Describe what it tells you
It shows that most of the energy is transferred as heat
90J of heat is transferred for every 10J of light
This means that it is pretty inefficient in it’s job as a light bulb because only 10J of every 100J (i.e. 10%) is transferred as light!
Energy efficiency
Show how to calculate how efficient an energy transfer process is using the example of a filament light-bulb below:
Filament light-bulb:
For every 100J of electrical energy supplied to the light bulb, 10J is transferred to light energy and 90J to heat energy. How efficient is the light-bulb?
The purpose of a light-bulb is to create light. So any energy which isn’t released as light is wasted.
Filament light-bulbs are very inefficient because they waste a lot of energy supplied as heat. For every 100J supplied, only 10J is transferred as light energy.
What is the
National Grid?
The National Grid is the system of power stations, cables (& pylons), and transformers that supply electrical energy all across the country.
Having a “grid” like this makes electricy supply very reliable because if one power station breaks down others are still supplying the grid.
The only other option to produce electricity is for individual houses to generate their own electricity (e.g. solar panels on the roof; small wind turbines in the garden, etc.)
Explain how the National Grid deals with varying demands on electricity supplies
- Demand for electricity is constantly monitored.
- More power stations can be brought on-line at times when more power is needed.
Some power stations take a lot of time to start-up or increase power (like coal powerstations) but others like hydroelectric power stations can switch on quickly. Electric mountain is an example and can go from off to full power in less than a minute.
Explain this chart
Demand for electricity is low when everyone is asleep.
As people get up for work the demand increases.
Demand is then fairly steady during the daytime as electricity is used in offices and factories.
In the evening demand goes up more as people go home and use electric cookers, heaters, kettles, etc
Correctly label the parts on this picture
- Step DOWN transformer
- High Voltage transmission lines
- Power station
- Consumers e.g. houses, shops, offices, factories
- Step UP transformer
A - Power station
B - Step UP transformer
C - High Voltage transmission lines
D - Step DOWN transformer
E - Consumers e.g. houses, shops, offices, factories
Why is electricity in high voltage transmission cables carried at high voltage and not at the voltages used in homes?
There is a lot of power carried in those cables!
If the electricity was carried at household voltage (about 230 volts) then the current would be really high. The high current would cause lots of heat in the wires which would be wasted energy.
By increasing the voltage (to 400,000 volts for example) then the current would be much much lower and there wouldn’t be the same wasted energy.
Given an equation to show how
power (measured in watts),
current (measured in amps), and
voltage (measured in volts)
are related
Remember the picture below.
Put your finger over one letter and it shows how the other two are related,
so to work out the formula for power, put your finger over P:
P (power) = I (current) x V (volts)
to work out the formula for voltage put your finger over V:
V (voltage) = Power divided by I (current)
etc
What are step-up and step-down transformers for when distributing electricity?
Electricity is distributed at high voltage to reduce the power lost from heat.
Transformers increase or decrease voltage.
Step up transformers increase the voltage of the electricity generated in power stations to the voltage distributed through the National Grid.
Step down transformers reduce the voltage from the National Grid down to 230V for use in homes
