Ch 5: Macrogeneration

Question 1

Which fossil fuel as of 2019, does the UK currently rely on very heavily?

Answer 1

Natural gas

Question 2

Which fossil fuel does the UK intend to phase out by 2025?

Answer 2

Coal, due to the highly polluting nature of the coal.

Question 3

What are the percentages of fossil fuels used for energy?

Answer 3

42% natural gas
18% nuclear
5% coal
18% wind
6% biomass

Question 4

What are the 4 stages of the fossil fuel power plant?

Answer 4

1. Combustion of the fuel
2. Evaporation of water
3. Steam used to turn a turbine
4. Condensing in the cooling towers

Question 5

Recall stage 1 (combustion of the fossil fuel).

Answer 5

The fuel is combusted to release the chemical energy, specifically releases the thermal energy.

Question 6

Recall stage 2 (evaporation of water).

Answer 6

The thermal energy extracted is used to heat the water in the furnace. The temperature of the water increases considerably, and it evaporates at 100 C into steam. The steam is ejected from the furnace to the steam turbine.

Question 7

Recall stage 3 (steam used to turn the turbine).

Answer 7

The steam, which is high velocity water molecules, collides with the fins of the steam turbine causing it to turn. There is energy lost from these molecules and thermal so the steam will exit with a lower temperature. This hit steam is now sent to the cooling towers.

Question 8

Recall stage 4 (condensing in the cooling towers).

Answer 8

The hot steam from the turbine enters the cooling towers where there is energy loss so the steam turns back to water. This cold liquid is then re circled back to the furnace and the process is repeated.

Question 9

What is the disadvantage of cooling towers?

Answer 9

There is energy lost and ejected into the atmosphere as they pass through the cooling towers so this reduces the efficiency. The efficiency is around 40%. A new method, Combined Heat and Power (CHP) aims to capture the lost energy and use it to heat buildings.

Question 10

What is the definition of direct renewable energy sources?

Answer 10

These renewable energies take energy from a renewable source such as wind or waves in the ocean and can convert this into electrical energy directly.

Question 11

What are some examples of direct renewable energy sources?

Answer 11

• Wind
• Hydroelectric
• Wave
• Tidal

Question 12

What is the definition of indirect renewable energy sources?

Answer 12

These take energy from a renewable energy such as the sun using a physical characteristic of the material being used and convert this energy into electrical energy.

Question 13

What are some examples of indirect renewable energy sources?

Answer 13

• Solar PV
• Biomass

Question 14

What are the energy changes involved in generating electricity from wind? (Going down for each stage in order)

Answer 14

Wind = Ke
Hub = Ke of blades
Gearbox = Ke of high speed shaft
Generator = electrical energy

Thermal and sound energy is lost from each progressing stage.

Question 15

What are the energy changes involved in generating electricity from solar? (Going down for each stage in order)

Answer 15

Sun = radiant
PV panel = electrical energy

Thermal and sound energy losses at the progressing stage

Question 16

What are the energy changes involved in generating electricity from hydroelectric? (Going down for each stage in order)

Answer 16

Dam = GPE
Moving water = Ke
Turbine = Ke
Generator = electrical energy

Thermal and sound energy lost at each progressing stage

Question 17

What are the energy changes involved in generating electricity from tidal? (Going down for each stage in order)

Answer 17

Behind tidal barrier = GPE
Moving water = Ke
Turbine = Ke
Generator = electrical energy

Thermal and sound energy lost at each progressing stage

Question 18

What are the energy changes involved in generating electricity from wave? (Going down for each stage in order)

Answer 18

Sun = radiant energy from sun produces wind with Ke
Waves = Ke of wind causes Ke of waves
Wave generator = Ke
Generator = electrical energy

Thermal and sound energy lost at the last 2 progressing stages

Question 19

What are the energy changes involved in generating electricity from biomass? (Going down for each stage in order)

Answer 19

Biomass fuel = chemical energy
Burning fuel = thermal energy
Steam = thermal energy (thermal loses)
Turbine = Ke (thermal and sound loses)
Generator = electrical energy (thermal and sound loses)

Question 20

How is electricity distributed through the National Grid?

Answer 20

The electricity produced in the power station is at 22kV.
A step-up transformer steps-up the voltage to between 275kV and 400kV.
The electricity can now be sent across the National Grid through the transmission lines.
A step-down transformer then reduces the voltage to 33kV for industry, and 11kV for distribution.
It is reduced to 240V for use in homes.

Question 21

Why is a step-up transformer used in the National Grid?

Answer 21

A step-up transformer increases the voltage, but this is done to reduce the current to a minimum. Minimising the current to reduce energy loses before transferring electricity across the grid is the disk of the step-up transformer.

Question 22

What is the definition of a SMART Grid?

Answer 22

A computer-controlled electricity network that switches input from one energy source to another as demand for energy varies on the grid.

Question 23

What are the key requirements in a SMART grid?

Answer 23

1. Predict demand - the grid will have a network of intelligent meters in the National Grid to accurately predict demand.
2. Measuring output from renewables - need intelligent meters to detect the output from renewables across the National Grid.
3. Adapting non-renewable power outputs - the electricity provider must establish the demand for electricity all day. The outputs must be monitored constantly, so that the additional contributions from fossil fuel power plants can be calculated. This info can then be sent to power stations to increase or decrease output.
4. Exporting or Importing to other nations - there is a possibility that there will be extra electricity produced, so this can be exported to other nations and also can be reversed so they can receive electricity is needed.

Question 24

What are the benefits of a SMART Grid?

Answer 24

• Maximise renewables
• Minimise fossil fuels
• Control electricity demand

Question 25

Why are the traditional methods of electricity transfers not reliable?

Answer 25

Renewable sources of energy are becoming more common to use.

Question 26

What are inter-connectors?

Answer 26

An electrical cable that joins 2 nations together, used to export electricity.

Question 27

What are the environmental benefits of inter-connectors?

Answer 27

1. Electricity can be exported to other nations when production exceeds the demand. The importing nation then reduces fossil fuel use.
2. Connections to nations such as Norway facilitates storage of renewable energy by means of sod pumped hydro. They can be stored and used when needed so it reduces the use of fossil fuels.

Question 28

What are the economic benefits of inter-connectors?

Answer 28

1. Enables nations to import energy from other nations . Which will drive down costs.
2. A nation’s fuel security is increased greatly.

Question 29

What does CHP stand for?

Answer 29

Combined Heat and Power

Question 30

What is another name for CHP?

Answer 30

Cogeneration

Question 31

What is the disadvantage of traditional power plants?

Answer 31

There is a loss of energy into the atmosphere (cooling towers) and thermal and sound energy. This reduces the efficiency of the power plants to 40%

Question 32

What does CHP do?

Answer 32

CHP aims to increase the efficiency of these power plants by using the thermal energy in the steam, which is lost to the surroundings (cooling towers). This can be turned to water and used to heat houses.

Question 33

What are the advantages of CHP?

Answer 33

1. Efficiency can exceed 80%.
2. Located close to end user so transmission losses are reduced.
3. Carbon emissions are reduced.
4. Energy bills are minimised.