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AQA A-level Environmental Science > Secondary Fuels: Electricity And Hydrogen > Flashcards

Secondary Fuels: Electricity And Hydrogen Flashcards

1
Q

Why are secondary fuels used?

A

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

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2
Q

Name 2 secondary fuels

A

Electricity
Hydrogen

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3
Q

How is electricity generated?

A

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

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4
Q

What forms of energy can be directly converted to electricity?

A

Kinetic energy,chemical energy and light

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5
Q

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?

A

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

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6
Q

How can electricity be gained from kinetic energy?

A

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

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7
Q

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

A

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.

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8
Q

What is used to get electricity from light energy?

A

Photovoltaic cells

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9
Q

How is electricity gained from light energy using photovoltaic cells?

A

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

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10
Q

How can chemical energy be converted to electricity?

A

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

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11
Q

How are electrochemical cells used in batteries to store energy?

A

They store chemical energy which can be converted to electricity

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12
Q

What is the disadvantage of electrochemical cells in normal batteries?

A

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

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13
Q

How do rechargeable batteries solve the problems of normal batteries?

A

They use electricity to reform the chemicals that produce electricity

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14
Q

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

A

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

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15
Q

How do fuel cells containing hydrogen and oxygen work?

A

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

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16
Q

What are the advantages of using electricity?

A

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

17
Q

How is electricity transported?

A

Conducting cables

18
Q

What are the disadvantages of using electricity?

A

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

19
Q

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

A

The location where it is generated might be geographically limiting

20
Q

What are the issues with underground cables for electricity?

A

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

21
Q

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

A

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

22
Q

How is hydrogen an important secondary fuel?

A

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

23
Q

how is hydrogen as a secondary fuel produced?

A

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

24
Q

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

A

Combustion to produce heat
Fuel cells

25
Q

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

A

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

26
Q

How are fuel cells a use of hydrogen?

A

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

27
Q

How is the storage of energy as hydrogen helpful?

A

It addresses the disadvantages of energy resources which are available intermittently

28
Q

Name 4 methods of hydrogen storage

A

Compressed gas
Liquid
Metal hydride systems
Ammonia

29
Q

How is compressed gas a form of hydrogen storage?

A

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

30
Q

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

A

Energy is required to run the compressor

31
Q

How is liquid a form of hydrogen storage?

A

Hydrogen is liquified under high pressure at low temperatures

32
Q

What is the disadvantage of liquid hydrogen storage?

A

Energy is required for refrigeration and to run the compressor

33
Q

How do metal hydride systems store hydrogen?

A

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

34
Q

What is the disadvantage of metal hydride systems as hydrogen storage

A

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

35
Q

How is ammonia a form of hydrogen storage?

A

Surplus primary energy is used to produce ammonia (NH3)

36
Q

What is the disadvantage of ammonia as hydrogen storage?

A

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

37
Q

What is the ‘hydrogen economy’?

A

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

38
Q

What does the development of a hydrogen economy not require?

A

Hydrogen to be the main energy source used by consumers

39
Q

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

A

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

AQA A-level Environmental Science (45 decks)

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