Generating Electricity

Question 1

How is electricity generated in a conventional power station?

Answer 1

In most power stations water is heated to produce steam, the steam drives a turbine, which is coupled to an electrical generator that produces the electricity.

Question 2

How is energy generated in a gas-fired power station?

Answer 2

In some gas-fired power stations, hot gases may drive the turbine directly. A gas-fired turbine may be switched on very quickly.

Question 3

What is a biofuel?

What sort of power stations can biofuels be used in?

Answer 3

Biofuels are renewable sources of energy
A biofuel is any fuel obtained from living or recently-living organisms.
Some biofuels can be used in small scale gas-fired power stations.

Question 4

What fuel is used in a nuclear power station?

Answer 4

Uranium

Question 5

How is electricity generated in a nuclear power station?

Answer 5

The nucleus of a uranium atom can undergo a process called nuclear fission, this process releases 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.

Question 6

What is a renewable energy source?

Examples?

Answer 6

Sources of energy that cannot be used up.

Energy from wind waves and tides.

Question 7

How is electricity generated in a wind turbine?

Answer 7

The wind passing over the blades makes them rotate and drive a generator at the top of a narrow tower.

Question 8

What three forms of water can energy be obtained from?

Answer 8

Falling water
Tides
Waves

Question 9

How is electricity generated in a hydroelectric power staion?

Answer 9

Water is collected in a reservoir, this water is allowed to flow downhill and turn turbines at the bottom of the hill.

Question 10

How is surplus electricity used in a pumped storage system?

Answer 10

In a pumped storage system surplus electricity is used at times of low demand to pump the water back up the hill to the top reservoir. This means that the energy is stored. Then at times of high demand the water can be released to fall through the turbines and transfer the stored energy to electrical energy.

Question 11

How can wave power be used to generate electricity?

Answer 11

We can use the movement of 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 onshore by a cable.

Question 12

How can tidal power be used to generate electricity?

Answer 12

The level of the sea around the coastline rises and falls twice each day. These changes in sea level are called tides. 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 level, it drives turbines.

Question 13

How does solar energy from the sun travel through space to earth?

Answer 13

As electromagnetic radiation

Question 14

What does a solar cell do and what type of devices can a solar cell power?

Answer 14

A solar cell can transfer the suns energy into electrical energy, each cell only produces a small amount of electricity. So they are useful to power small devices such as watches and calculators.

Question 15

Large numbers of solar cells are doing together to form what?

Answer 15

Solar panels

Question 16

Water flowing through a solar heating panel is heated directly by which type of energy?

Answer 16

The suns energy

Question 17

How does a solar power tower heat water to produce steam?

Answer 17

A solar power tower uses thousands of mirrors to reflect sunlight on the water tank to heat the water and produce steam.

Question 18

How is geothermal energy produced and how can this be used to turn generators so that electricity is produced?

Answer 18

Geothermal energy is produced inside the Earth by radioactive processes and this heat the surrounding rock. In volcanic or 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 steam is used to drive turbines that turn generators and so electricity is produced.

Question 19

Name three types of non-renewable energy resources.

Answer 19

Coal, oil, gas and uranium

Question 20

When will oil and gas most likely run out?

Answer 20

The next 50 years

Question 21

Name two ways in which scientists are trying to reduce the environmental impact of of using fossil fuels.
What is the abbreviation given to the second method and what does it stand for?

Answer 21

1) Removing sulphur from fuel before burning
2) CCS - carbon capture and storage, involves capturing carbon dioxide before it is released into the atmosphere from power stations and storing it in old oil and gas fields.

Question 22

How is electricity distributed in Britain?

Answer 22

The National Grid

Question 23

What is the National Grid?

Answer 23

The National Grid is a network of cables and Transformers that connect power stations to homes, schools, factories and other buildings. Since the whole country is connected to the system power stations can be switched in or out of the grid according to demand.p

Question 24

Cables in the National Grid are carried long distances across the countryside supported by overhead pylons how are cables different in towns to the countryside cables?

Answer 24

In towns and close to home is the cables are buried underground.

Question 25

What is the voltage of the National Grid and at what voltage do power stations produce electricity?

Answer 25

The National Grid’s voltage is 132,000 V or more. Power stations produce electricity at a voltage of 25,000 V.

Question 26

What does a step-up transformer do to the voltage of the electricity from a power station and why is this done?

Answer 26

A step-up transformer increase the voltage before the electricity enters the national grid. The voltage is increased, because transmission at a high voltage reduces the energy wasted in the cables, making the system more efficient.

Question 27

What does a step-down transformer do to the voltage of electricity before it is supplied to consumers at local sub-stations and why is this done.

Answer 27

A step-down transformer reduces the voltage to 230 V for use in homes, schools and offices because it would be dangerous to supply it to consumers at the very high voltages of the national grid.

Question 28

What is the base load demand?

When does the demand vary?

Answer 28

The constant amount of energy supplied by all power stations in the country.
The demand varies during the day and between summer and winter.

Question 29

How is the variable energy demand met?

Answer 29

Using gas-fired power stations, pumped-storage schemes and renewable energy sources.

Question 30

Which type of power station has the shortest start up time?

Which type of power station has the longest start up time?

Answer 30

Gas-fired power stations have the shortest start up times and nuclear power stations have the longest.

Question 31

What are the advantages and disadvantages of overground (4) and underground (5) cables?

Answer 31

Underground
1) Undergropund are much more expensive.
2) Underground are much more difficult to repair.
3) Underground are difficult to bury where they cross canals.
4) Underground cannot be seen.
5) (normally) No/reduced shock hazzard.
Overground
1) Overground are a hazard to low flying aircraft
2) Overground cables are mire likely to be damaged by weather.
3) Overground cables spoil the landscape.
4) Overground cables produce electric and magnetic fields which may affect people’s health.

Question 32

Outline two advantages and two disadvantages of Nuclear power.

Answer 32

Advantages:
1) No greenhouse gases unlike fossil fuels.
2) Much more energy per kilogram of uranium fuel than from fossil fuel.
Disadvantages:
1) Used fuel rods contain nuclear waste which has to be stored safely for centuries.
2) An explosion in a nuclear reactor could release radioactive material over a wide area, which would affect these areas for many years.

Question 33

Outline four advantages and four disadvantages of renewable energy sources.

Answer 33

Advantages:
1) They will never run out.
2) They do not produce greenhouse gases or acid rain.
3) They do not create radioactive waste products.
Disadvantages:
1) Wind turbines are unsightly and create noise pollution.
2) Tidal barrages affect river estuaries and the habitats of creatures and plants there.
3) HEP schemes need large reservoirs of water, which can affect nearby plant and animal life, habitats are often flooded to create the dam.
4) Solar cells need to cover large areas to generate large amounts of power.

Question 34

Why are renewable energy sources unreliable?

Give one reason why each type of renewable energy is unreliable.

Answer 34

Renewable energy sources are unreliable because the amount of electricity they generate depends on the conditions.
HEP - Upland reservoir could run dry
Wind/Waves - Wind and waves may be too weak on very calm days.
Tidal - Height of the tide varies both on a monthly and a yearly cycle.
Solar - no solar energy at night and it is variable during the day.