Generating Electricity Flashcards
How do most power stations work?
- Water is heated to produce steam
- The steam drives a turbine, which is coupled to an electrical generator.
- This generator converts the kinetic energy to electrical energy and thus generates electricity
How are fossile fuels obtained/what are they?
Long-dead biological material that has been compressed under high pressure to form carbon compounds. Obtained by drilling/mining (coal)
How do gas fire power stations and hyroelectric (HEP) power stations differ from the standard power station model?
In gas-fired power stations, the hot gas drives the turbin directly.
In HEP, the water drives the turbin (grav. potential -> kinetic -> electric)
What is burned in fossil-fuel powered power stations?
Coal, oil, and gas
What is used as fuel in a nuclear power station?
Uranium or plutonium
What is a biofuel?
A fuel obtained from living or recently living organisms
What type of energy source are biofuels?
Renewable
Where does the energy required to drive the turbines/produce steam come from in a nuclear power station?
Not from burning uranium/plutionium!
- The nucleaus of a uranium atom can undergo nuclear fission, releasing thermal energy (and other waste energy)
- There are lots of uranium nuclei, so lots of fission reactions take place, releasing lots of energy
- This energy is used to heat water, turning it into steam which drives the turbine
Complete the sentence:
Biofuels can be used in…
…small-cale, gas-fired power stations
Which releases more energy per kilogram of fuel burnt:
Uranium undergoing fission OR fossil fuels being burnt?
Uranium undergoing fission - it has a higher fuel density per kg
Nuclear power stations do not release any…
…greenhouse gasses, unlike fossil-fuel power stations
What do nuclear power stations produce that other power stations don’t?
Radioactive waste
What are the negatives of radioactive waste
- It’s radioactive
- It must be safely stored for a long period of time
- It can be used to make nukes (which can be bad… depening on your views)
Draw and label a diagram of a fossil-fuel powered power station
Define ‘renewable energy’
Energy from sources that never run out (or will run out in a very, very long time)
How can wind be used to generate electricity?
- Can be used to drive turbines directly
- In a wind turbine, the wind passing over the blades makes them rotate and drives a generator at the top of a narrow tower
What methods of generating electricity use water?
Electricity can be produced from energy obtained from:
- Falling water - HEP
- Waves - Wave power
- Tides - Tidal power
How does HEP work?
- At a HEP, water is collected in a reservoir.
- This water is allowed to flow downhill and turn turn turbines at the bottom of the hill
- In a pumped storage system, surplus electricity is used at times of low demand to pump the water back up the hill into the reservoir
- This means the energy is stored
- At times of high demand, the water can be released to fall through the turbines and transfer the stored grav. pot. to kinetic, and then to electical energy.
How is wave power used to generate electricity?
- We can use the movement of the waves on the sea to generate electricity
- The movement drives a floating turbine that turns a generator.
- Then, the electricity is delivered to the grid system on shore by a cable
How is tidal power used to generate electricity?
- The level of sea around the coastline rises and falls twice each day
- These changes in sea level are called tides (crazy)
- If a barrage is built across a river estuary, the water at each high tide can be trapped behind it
- When the water is released to fall down to the lower sea lever, it drives turbines.
N.B. This works a bit like HEP, except instead of pumping/releasing water from a reservoir, the tides naturally raise the water level and it can then be released.
Why is wave power likely to be less reliable than tidal power?
There will always be two tides a day because the tides are controlled by the Sun and Moon.
However, the waves are controlled by the wind and weather, so on a calm day there might not be as many waves.
How does solar energy travel from the Sun to the Earth?
As electromagnetic radiation (the electromagnetic spectrum)
What do solar cells do?
Transfer solar energy directly into electricity
What are solar cells used to power and why?
Only small devices such as watches and calculators because each cell only produces a small amount of energy.
However, we can join large numbers of cells together to form a solar panel.
What happens to water flowing through a solar heating panel?
It is heated directly by energy from the Sun
What is a solar power tower?
A tower surrounded by mirrors that reflect sunlight onto a water tank at the top of the tower. This produces steam
Draw a labelled diagram of a solar heating panel
Rememember to label the black cover!
How is geothermal energy used to generate electrictity?
- Geothermal energy is produced inside the Earth by radioactive processes which heat the surrounding rock
- In volcanic and other suitable areas, very deep holes are drilled and cold water is pumped down to the hot rocks
- There it is heated and comes back to the surface as steam
- The steam is then used to drive turbines that turn generators, which in turn produce electricity
- In some parts of the world, hot water comes up to the surface naturally and can be used to heat buildings near by
Which energy resources are non-renewable?
Fossil-fuels and nuclear power
When will fossil-fuels run out?
Oil + gas in the next 50 years, although coal much longer
What ways are scientists investigating in order to reduce the environmental impact of using fossil fuels?
- Removing sulfur before burning to prevent sulfur dioxide being produced
- Carbon-capture/re-capture technology to capture CO2 before it is released into the atmosphere from power stations. It would instead be stored in old oil + gas fields
What are the advantages and disadvantages of using coal as an energy source?
- Bigger reserves than other fossil fuels
- Reliable
HOWEVER
- Non-renewable
- Produces CO2, a greenhouse gas (contributes to climate change)
- Produces SO2, causing acid rain
What are the advantages and disadvantages of using oil as an energy source?
- Reliable
- Already have the infrastructure to burn it
HOWEVER:
- Non-renewable
- Produces CO2, a greenhouse gas (contributes to global warming)
- Produces SO2, causing acid rain
What are the advantages and disadvantages of using gas as an energy source?
- Reliable
- Quick start-up time
- Existing infrastructure
HOWEVER:
- Non-renewable
- Produces CO2, a greenhouse gas (causes climate change)
What are the advantages and disadvantages of using nuclear fuel as an energy source?
- No polluting gasses produced
- Reliable
- High energy denisty (energy produced per kg fuel)
HOWEVER:
- Non-renewable
- Produces radioactive waste, which is difficult to dispose of + must be stored for a long time (long half-life)
- Small risk of big nuclear accident
- Slowest start-up time
What are the advantages and disadvantages of using wind as an energy source?
- Renewable
- No polluting gasses produced
- Free
HOWEVER:
- Requires many large turbines - unsightly
- No existing infrastructure
- Not reliable
What are the advantages and disadvantages of using HEP as an energy source?
- Renewable
- No polluting gasses produced
- Reliable in wet areas
- Free
HOWEVER:
- Only works in wet + hilly areas
- Damming areas causes flooding and affects local ecology
What are the advantages and disadvantages of using waves as an energy source?
- Renewable
- No polluting gasses produced
- Free
HOWEVER:
- Can be hazardous to boats/fish
- Not reliable
- No existing infrastructure
What are the advantages and disadvantages of using tidal power as an energy source?
- Renewable
- No polluting gasses produced
- Free
HOWEVER:
- Only a few river estuaries suitable
- Building a barrage affects local ecology + shipping
- No exisiting infrastructure
What are the advantages and disadvantages of using solar power as an energy source?
- Renewable
- No polluting gasses produced
- Reliable in hot countries during the day
- Free
HOWEVER:
- Solar cells only produce small amounts of electricity
- Unreliable in less sunny countries
What are the advantages and disadvantages of using geothermal power as an energy source?
- Renewable
- No polluting gasses produced
- Free
HOWEVER:
- Only economically viable in a few places
- Drilling through large depth of rock is difficult + expensive
- Can also permanently alter local landscape
In Britain, how is energy distributed?
Through the National Grid
What is the National Grid?
The network of cables and transformers used to transfer electricity from power stations to consumers
What types of pylons are used in different areas?
Overhead are used in the countryside
Underground are used in towns and close to homes
What is the voltage of the National Grid and of power stations?
National Grid: 132,000V +
Power stations: 25,000V
How does the National Grid transport energy from power stations to our homes/consumers?
- In power stations, electricity is generated at a particular voltage
- The volatge is then increased by step-up transformers before being transmitted across the National Grid in cables. This is done because high voltage reduces the energy wasted in cables, making the system more efficient
- It would be dangerous to supply electricity to consumers at these high voltages, so step-down transformers are used to reduce to voltage to 230V
What is the base load?
The constant amount of electricity being generated by power stations
Complete the sentence:
The demand for electricity varies…
…during the day and between summer and winter
How can the variable demand for electricity be met?
- Gas-fired power stations can be used because they have a quick start-up time
- Pumped-storage can be used. When demand is low, water can be pumped to the top of reservoirs ready to be released when deman increases
- Renewable sources can be used to suppliment the base load (e.g. turning on wind turbines)
What percentage of different energy sources does the UK use to generate electricity?
46% Gas
31% Coal
16% Nuclear
5% Other fuels + Renewables
1% Oil
1% HEP
What types of energy sources are likely to be used in the future to generate electricity?
- Nuclear power stations
- Fossil-fuel stations using carbon capture
- Renewable sources
