Flashcards in P1 4 Generating Electricity Deck (40):
What is most of the energy you use generated by?
How is electricity generated in coal, oil, gas fired stations?
The burning fuel heats the water in the boiler which produces steam. The steam drives a turbine that turns the electricity generator.
What are coal, oil and gas? What are they made from?
From long-dead biological material
How is electricity produced in some gas-fired power stations?
The natural gas is burned directly in a gas turbine engine and the heated wit produces a powerful jet of hot gases and air which drive the turbine.
What is a biofuel?
Any fuel obtained from living or recently living organisms such as animal waste, wood chip, ethanol, straw .etc.
Give the advantages and disadvantages of a biofuel?
It is renewable
It is carbon neutral
It can take up a large amount of land
What is meant by renewable?
The energy source will never run out.
What is meant by carbon neutral?
The carbon dioxide produced can be balanced out with the carbon taken in
What are the fuels used in a nuclear power station?
What is nuclear fission?
When the nucleus of a uranium atom is unstable and splits into two.
How is the electricity obtained from a nuclear power station?
As there are a lot of uranium atoms, the core becomes very hot.
The energy of the core is transferred by a fluid - coolant and is pumped through the core.
The coolant is very hot when it leaves the core. It flows through a pipe to a heat exchanger and back to the core.
The energy of the coolant is used to turn water into steam and drives turbines to turn electricity generators.
Which releases more energy in a given time - nuclear power stations or fossil fuel stations?
Nuclear power stations (x1000)
How does wind power generate electricity?
The wind turbine is an electricity generator on top of a tall tower. The force of the wind drives the turbine blades around and turns the generator.
How can the power generated increase in a wind turbine?
When the wind speed increases
How does wave power generate electricity?
The wave generator floats on top of the waves and move up and down. This motion turns the generator so generates electricity. A cable between the generator and the shore delivers electricity to the grid system.
How can we generate electricity through hydroelectric power?
When water is collected in a reservoir or in a pumped storage scheme and flows downhill, the water drives turbines that turn electricity generators at the foot of the hill.
How is electricity generated through tidal power?
The tidal power station traps water from each high tide behind a barrage. Then the high tides are released into the sea through turbines and drive the generators in the barrage.
How is electricity generated through the sun?
Solar a are used to convert the sun's energy into electricity.
What are the disadvantages and advantages of solar cells?
Useful where we only need small amounts of electricity or remote places
They are expensive
We need plenty of sunshine/ lots of them
How is electricity generated through geothermal energy?
Energy comes from the energy released by radioactive substance is deep inside the earth. Water is pumped into the hot rocks underground and produces steam to drive turbines and generate electricity.
What are the disadvantages and advantages of fossil fuels?
They do not produce radioactive decay
They let carbon dioxide and other greenhouse gases into the atmosphere which causes global warming
They are non-renewable
They produce sulfur dioxide which can cause acid rain
What can be used to stop carbon dioxide emissions into the atmosphere?
Carbon capture and storage (CCS) old oil and gas fields are used to store carbon dioxide.
What are the advantages and disadvantages of nuclear power?
No greenhouse gases
Much more energy from each kg of uranium
Used fuel rods contain radioactive waste
An explosion can take place and can release radioactive material which can stay for many years.
What are the disadvantages and advantages of renewable energy sources?
They are renewal
They don't produce greenhouse gases
They do not create radioactive waste
They can be used in remote places
Wind turbines are noisy and unattractive
Tidal barrages affect the habitats of creatures and plants there
Hydroelectric schemes can affect habitats
Solar cells are expensive and will need to cover large areas to supply large amounts of power
What is the national grid?
A network of cables and transformers that distributes electricity to out homes from distant power stations and renewable energy generators.
What does The National Grid also contain?
What are the transformers? What are their roles?
Step-up transformers - to step the voltage up to the grid voltage
Step-down transformers - to step the grid voltage down for use at homes and offices.
What does the electrical power supplied to any device depend on?
The appliance's current an voltage.
Which does what? Which transformers raise/lower the current/voltage?
The step-up transformers lower the current and raise the voltage whereas the step-down transformer does vise-versa.
Why is it important to raise the voltage?
So that less current is needed to transfer the same amount of power. Energy losses due to the heating effect of the current is also reduced. More efficient.
State the disadvantages of underground cables.
• More expensive
• Much more difficult to repair
• Difficult to bury where they cross rivers, roads and canals.
What are the disadvantages of overhead cables?
• Spoils landscapes
• Can affect health
• Electric and magnetic fields might affect people
What does the start-up time depend on?
The type if power station
Give the order from shortest to longest start-up time?
Why are renewable energy resources unreliable?
The amount of energy they generate depends on the conditions.
How can a hydroelectric, wind and wave, tidal and solar energy resource be unreliable?
Hydroelectric - upland reservoir could run dry
Wind/wave - can be too weak on calm days
Tidal - height of tides vary on a monthly and yearly cycle
Solar - no solar energy at night and variable during day
How is the variable demand for electricity met?
• Using nuclear, coal and oil-fired power stations to provide a constant amount of electricity.
• Using gas-fired power stations and pumped-storage schemes to meet daily variations in demand and extra demand in the winter.
• Using renewable energy sources when demand is high and renewables are in operation.
• Using renewable energy sources when demand is low to store energy in pumped storage schemes.
What is base-load?
A constant supply of electricity
Which power stations meet the base-load demand?
Coal, nuclear and oil-fired