Topic 8: Energy, power and climate change Flashcards Preview

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Flashcards in Topic 8: Energy, power and climate change Deck (104)
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1

How is thermal energy converted to work?

In principle, thermal energy can be completely converted to work in a single process, but the continuous conversion of this energy into work implies the use of machines that are continuously repeating their actions in a fixed cycle. Any cyclical process must involve the transfer of some energy from the system to the surroundings that is no longer available to perform useful work.

2

Explain what is meant by degraded energy.

Energy that is unavailable to a system because it has been transferred to the surroundings.

3

What happens to energy that is transferred to the surroundings?

It is no longer available to do work.

4

What is a Sankey diagram?

A diagram used to represent energy conversions.

5

In what direction should the main arrow in a Sankey diagram be drawn?

From left to right.

6

What does the main arrow in a Sankey diagram represent?

The energy changes taking place.

7

What does the width of the arrow in a Sankey diagram represent?

The power or energy involved at a given stage.

8

What does the arrow drawn up or down in a Sankey diagram represent?

Degraded energy.

9

Outline the principle mechanisms involved in the production of electrical power. (5)

1. A fuel is used to release thermal energy 2. Thermal energy is used to boil water to make steam 3. Steam is used to turn turbines 4. Motion of the turbines is used to generate electrical energy by rotating coils in a magnetic field 5. Transformers alter the potential difference

10

Identify different world energy sources.

In most instances, the Sun is the prime energy source for world energy. Other cases: - gravitational energy of the Sun and the Moon - nuclear energy stored within atoms - the Earth's internal heat energy

11

What are six renewable energy sources?

  1. hydroelectric
  2. photovoltaic cells
  3. active solar heaters
  4. wind
  5. biofuels
  6. geothermal

12

What are four non-renewable energy sources?

  1. oil
  2. natural gas
  3. coal
  4. nuclear

13

Which four energy sources emit carbon dioxide?

  1. coal
  2. natural gas
  3. oil
  4. biofuels

14

Define: renewable energy source

Energy that comes from resources which are naturally replenished on a human time scale

15

Define: non-renewable energy source

A resource that cannot be replaced when it is used up.

16

Define: energy density

energy density = (energy released by fuel) / (mass of fuel consumed)

17

What is the standard index measurement for energy density?

J kg-1

18

Discuss how choice of fuel is influenced by its energy density.

When the fuel needs to be transported: the greater the mass of fuel that needs to be transported, the greater the cost.

19

What is the energy density of coal?

3.3 X 10J kg-1

20

What is the energy density of oil?

4.2 X 10J kg-1

21

What is the energy density of natural gas?

5.4 X 10J kg-1

22

What was the world's proportional energy consumption of oil in 2003?

38%

23

What was the world's proportional energy consumption of natural gas in 2003?

24%

24

What was the world's proportional energy consumption of coal in 2003?

24%

25

What was the world's proportional energy consumption of nuclear in 2003?

6%

26

What was the world's proportional energy consumption of other resources in 2003?

8%

27

Advantages of nuclear power.

  1. Extremely high energy density – a great deal of energy is released from a very small mass of uranium
  2. Reserves of uranium are large compared to oil
  3. Do not produce carbon dioxide

28

Disadvantages of nuclear power.

  1. Process produces radioactive nuclear waste that is currently just stored
  2. Larger possible risk if anything should go wrong
  3. Non-renewable (but should last a long time)

29

Advantages of wind energy

  1. Very clean production – no harmful chemical by-products

  2. Renewable source of energy

  3. Source of energy is free

30

Disadvantages of wind energy.

  1. Source of energy is unreliable – could be a day without wind
  2. Low energy density – a very large area would be need to be covered for a significant amount of energy
  3. Some consider large wind generators to spoil the countryside because they are ugly and produce a lot of noise