Secondary Fuels: Electricity And Hydrogen

Question 1

Why are secondary fuels used?

Answer 1

Primary fuels that come directly from the environment rent always in forms that are easy to use

Question 2

Name 2 secondary fuels

Answer 2

Electricity
Hydrogen

Question 3

How is electricity generated?

Answer 3

It involves to conversion of energy from a range of original primary fuels

Question 4

What forms of energy can be directly converted to electricity?

Answer 4

Kinetic energy,chemical energy and light

Question 5

Kinetic energy, chemical energy and light, are the forms of energy that can be directly converted t electricity. What happens with primary fuels that aren’t in these energy forms?

Answer 5

Several energy conversions may be needed to convert energy in a primary fuel to an energy store that an be converted to electricity

Question 6

How can electricity be gained from kinetic energy?

Answer 6

Kinetic energy can spin an electrical conductor with a magnetic field in a generator
This is used directly in wind and wave power

Question 7

In a conventional power station, how is electricity produced from heat energy?

Answer 7

Heat energy boils water, converting it to kinetic energy in high pressure expanding steam which is used to spin turbines which are used to spin generators.

Question 8

What is used to get electricity from light energy?

Answer 8

Photovoltaic cells

Question 9

How is electricity gained from light energy using photovoltaic cells?

Answer 9

Photons of light strike PV cell surface and displace electrons which makes the surface layer negatively charged.
The free electrons can flow along a conductor to the positively charged layer
The moving electrons can be used in electrical appliances

Question 10

How can chemical energy be converted to electricity?

Answer 10

In reactions where one chemical accepts electrons at an electrode, and another releases at another electrode
The electrons flowing between the electrodes can be used to power electrical equipment

Question 11

How are electrochemical cells used in batteries to store energy?

Answer 11

They store chemical energy which can be converted to electricity

Question 12

What is the disadvantage of electrochemical cells in normal batteries?

Answer 12

Once the chemical reactions have taken place to produce the electricity, the battery loses its ability to make more

Question 13

How do rechargeable batteries solve the problems of normal batteries?

Answer 13

They use electricity to reform the chemicals that produce electricity

Question 14

Electrochemical cells are also used in fuel cells. How do fuel cells work?

Answer 14

They use electrochemical cells to store energy in chemicals like hydrogen and alcohols
They wont lose their ability to produce electricity, as long as a supply of fuel is available

Question 15

How do fuel cells containing hydrogen and oxygen work?

Answer 15

Hydrogen releases electrons whilst oxygen accepts them
The resulting ions combine to create water

Question 16

What are the advantages of using electricity?

Answer 16

No pollution is caused when used
It is easy to convert to other energy forms
Transport is easy

Question 17

How is electricity transported?

Answer 17

Conducting cables

Question 18

What are the disadvantages of using electricity?

Answer 18

Converting primary fuel to it isn’t very efficient
It is difficult to store, there are no large scale options currently available
Initial production of it might be polluting

Question 19

Why may it be necessary to transport electricity using a grid of electrical cables?

Answer 19

The location where it is generated might be geographically limiting

Question 20

What are the issues with underground cables for electricity?

Answer 20

Laying them is expensive
The cables need to be cooled, which requires energy to pump the coolant fluid

Question 21

What are the issues with overhead cables for the transport of electricity?

Answer 21

They can cause aesthetic problems in scenic areas
Birds might be killed if they collide with them

Question 22

How is hydrogen an important secondary fuel?

Answer 22

It enables the energy from unreliable and intermittent supplies to be efficiently used because they can be converted to a form that can be stored

Question 23

how is hydrogen as a secondary fuel produced?

Answer 23

By the electrolysis of water using electricity from surplus primary energy sources

Question 24

What are the 2 main methods used to release chemical energy from stored hydrogen?

Answer 24

Combustion to produce heat
Fuel cells

Question 25

How is the combustion to produce heat a use of hydrogen?

Answer 25

The produced is then used to heat buildings,water and industrial processes
Or it used to boil water and create steam to drive turbines and generate electricity

Question 26

How are fuel cells a use of hydrogen?

Answer 26

Hydrogen is involved in the electro chemical process, alongside oxygen, to produce water and also release energy

Question 27

How is the storage of energy as hydrogen helpful?

Answer 27

It addresses the disadvantages of energy resources which are available intermittently

Question 28

Name 4 methods of hydrogen storage

Answer 28

Compressed gas
Liquid
Metal hydride systems
Ammonia

Question 29

How is compressed gas a form of hydrogen storage?

Answer 29

A compresor pump can pump up to 700 times the normal volume into storage tanks

Question 30

What is the disadvantage of compressed gas a form of hydrogen storage?

Answer 30

Energy is required to run the compressor

Question 31

How is liquid a form of hydrogen storage?

Answer 31

Hydrogen is liquified under high pressure at low temperatures

Question 32

What is the disadvantage of liquid hydrogen storage?

Answer 32

Energy is required for refrigeration and to run the compressor

Question 33

How do metal hydride systems store hydrogen?

Answer 33

Hydrogen is absorbed onto the surface of a metal matrix
It allows low pressure hydrogen storage

Question 34

What is the disadvantage of metal hydride systems as hydrogen storage

Answer 34

The storage tanks are larger and heavier than a petrol tank that stores the same amount of energy

Question 35

How is ammonia a form of hydrogen storage?

Answer 35

Surplus primary energy is used to produce ammonia (NH3)

Question 36

What is the disadvantage of ammonia as hydrogen storage?

Answer 36

Some energy required but not as much as other storage techniques
This is because the process doesnt require high pressures or low temps

Question 37

What is the ‘hydrogen economy’?

Answer 37

The proposal that current energy supplies would continue to satisfy current demand and hydrogen used to store surplus energy
It could enable communities to be fuelled renewable from an abundant and convienient store

Question 38

What does the development of a hydrogen economy not require?

Answer 38

Hydrogen to be the main energy source used by consumers

Question 39

What is the difference between hydrogen and other renewable energy resources?

Answer 39

It has a high energy density and could potentially replace fossil fuels for uses like powering vehicles