Chapter 8 - Energy Production Flashcards
1
Q
How does the production of electrical power normally start?
A
With the release of thermal energy from a fuel.
2
Q
What does any cyclical process involve?
A
The transfer of some energy from the system to the surroundings that is no longer available to perform useful work.
3
Q
What is degraded energy?
A
Unavailable energy.
4
Q
What is the main Feature of a Sankey Diagram?
A
They represent the energy flow in a system and are to scale.
5
Q
What is the process for electrical power production?
A
A fuel is used to release thermal energy which is used to boil water and create steam, to then turn turbines. The motion of the turbines is used to generate electrical energy.
6
Q
What is the equation for power and it’s units?
A
Power = energy / time
JS^-1 or W
7
Q
What’s the difference between renewable and non-renewable sources of energy.
A
Renewable sources of energy cannot be used up.
Non-Renewable sources can be.
8
Q
What are examples of Renewable sources?
A
Hydroelectric, photovoltaic cells, active solar heaters, wind, biofuels.
9
Q
What are examples of Non- Renewable sources?
A
Coal, oil, natural gas, nuclear.
10
Q
Are nuclear sources Renewable or not?
A
Nuclear sources (both fission and fusion) consume a material as their source so they are non-Renewable. But the supply available can make the source effectively renewable (fusion).
11
Q
Can fuels be managed in renewable or non-renewable ways?
A
Yes, depending on the strategy. E.g replanting trees the same rate than cutting them down can be renewable.
12
Q
What are all the possible sources of energy on Earth?
A
Sun’s radiation
Gravitational energy of the sun and moon.
Nuclear energy stored within atoms.
Earth’s internal heat.
13
Q
What is specific energy?
A
The energy liberated per unit mass of fuel consumed. Unit is Jkg^-1
14
Q
What is the equation for specific energy?
A
Energy released from fuel / mass of fuel consumed.
15
Q
What’s effects the cost of transporting fuel?
A
The bigger the mass of the fuel the more expensive to transport.
16
Q
What is energy density?
A
The energy liberated per unit volume of fuel consumed. Unit is Jm^-3
17
Q
What is the equation of energy density?
A
Energy release from fuel / volume of fuel consumed
18
Q
What is the comparison of energy sources?
A
Pg.83 of study guide
19
Q
What are the 3 fossil fuels and how are they formed?
A
Coal, oil and natural gas.
They have been produced over 10/100’s of years from accumulation of dead matter.
Its converted to fossil fuels by exposure to high temperature and pressure under the Earths surface.
20
Q
How is coal formed?
A
Formed from the dead plant matter that used to grow in swamps, which was buried and compressed by more plant matter and other substances.
21
Q
How is oil formed?
A
From The remains of microscopic marine life and the compression took place under the sea.
22
Q
How is natural gas formed?
A
Occurs in underground pockets and can also be obtained as the by-product during the production of oil. Can also manufacture gas from coal.
23
Q
What’s the original source of energy for fossil fuels?
A
All fossil fuels were originally living matter, so the original source of this energy was the sun.
24
Q
What is the efficiency of fossil fuels?
A
Table on pg.84 of study guide.
25
What are the advantages of fossil fuels?
High specific energy and energy density.
Relatively easy to transport
Cheap compared to other sources
Power stations can be blurt anywhere with good transport links and water availability.
Use directly in homes for heating
26
What are the Disadvantages of fossil fuels?
Produces pollution and greenhouse gases
Extraction of fossil fuels can damage the environment
Non-Renewable
Coal powered stations need large amounts of fuel.
27
What are the principles of energy production? (Fission)
Nuclear power stations use uranium-235 as fuel
Incoming neutron causes a uranium nucleus to split apart
High temperature and fast moving particles
28
How is a chain reaction caused?
If the neutrons go on to imitate further reactions
29
What is important about the design of a nuclear reactor?
Only one neutron from each reaction goes on to initiate a further reaction
If more reactions took place the chain reaction would run out of control
If less reactions took place the fission reaction would soon stop.
30
What factors influence if the neutron goes on to cause a fission reaction?
Number of nuclei "in the way"
| The speed of the neutrons
31
What is the critical mass of fuel?
As the size of block mass increases so does the chance of the neutron causing a further reaction.
As the fuel is assembled it reaches a point where a chain reaction can occur. (critical mass of fuel is assembled)
32
What does the value of critical mass depend on?
The nature of fuel being used
| The shape of the assembly
33
What has to occur to the neutrons to create reactions in the fission process?
They are moving too fast to make reactions likely, so they have to be slowed down.
34
What are the 3 components of a nuclear reactor?
Moderator
Control rods
Heat exchanger
35
What does the moderator allow?
Slows down the collisions between nuclei and Neutrons, so further reactions take place
36
What do the control rods do in the nuclear reactor?
They can be introduced or removed in the reaction chamber to control the chain reaction
37
What does the heat exchanger do?
Allows the reactions to occur in the sealed off section. In this section the reactions increase the core temperature and heats the water into steam, which is then used to turn the turbines.
38
What is the diagram for the pressurised water nuclear reactor?
Pg. 85 of the study guide
39
What are the advantages of nuclear power?
High specific energy (lots of energy realised from a small mass of uranium)
Large reserves of uranium compared to oil
40
What are the disadvantages of nuclear power?
Radioactive waste, which is just being stored
Large risk if anything goes wrong
Non-renewable
41
What is enrichment?
Natural occurring uranium contains less than 1% of uranium-235.
Enrichment: the percentage composition is increased to make nuclear fission more likely.
42
What other compound is also capable of sustaining fission reactions?
Plutonium-239 and is formed as a by-product of a conventional nuclear reactor.
43
What is the process to achieve plutonium-239 from uranium-238?
Uranium-238 captures fast moving neutrons to form uranium-239, which then undergoes beta-decay to neptunium-239 and the another beta-decay to plutonium-239.
44
What is reprocessing?
Treating used fuel waste from nuclear reactors and to recover uranium and plutonium and to deal with other waste products.
45
What is a fast breeder reactor?
A design which utilizes plutonium-239
46
What type of nuclear fission produces nuclear weapons?
Uncontrolled fission as it produces huge amounts of energy that is then released.
Nuclear weapons can use both uranium and plutonium as fuel.
47
What are some issues with nuclear weapons?
Moral issues: destructive capability
The consequences of a nuclear war have forced countries to agree to non-proliferation treaties. An attempt to limit nuclear power technologies to a small numbered nations.
Plutonium-239 (used for weapons) is a by-product of uranium .
48
What's the complicated question which comes into play around the topic of nuclear weapons.
Is it right for only some countries to have nuclear capability and prevent other countries from acquiring that knowledge?
49
What are the Health and safety risks with nuclear power?
Uncontrolled nuclear fission would cause an explosion and a thermal meltdown of the core.
Can distribute radioactive material to the surroundings causing many fatalities.
Power stations can be targets for terrorists
Mining operation involves risks due to radioactivity
The transportation of the uranium and the waste needs to be secure.
50
What are fusion reactors?
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They offer (theoretical) power generation without problems of nuclear fission.
Hydrogen is the fuel (is in plentiful supply), and doesn't produce radioactive waste
It's requires high temperatures (same reaction that happens in the sun) to ionise atomic hydrogen into a plasma state.
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51
What are the challenges with fusion reactors?
Maintaining and confining the plasma at a Hugh enough temperature and density for fusion to take place.
52
What does a photovoltaic cell do?
It converts a portion of the radiated energy directly into a potential difference, using a semiconductor.
Only produces a small voltage so can only run small devices that don't need a lot of current/energy.
53
How can you get more voltage and current out of a photovoltaic cell? (Solar cell)
In series it will generate a higher voltage.
| Several in parallel it will provide a higher current.
54
What are the diagrams for the two different types of solar power?
Pg.87 of study guide
55
What is a active solar heater? (Solar panel)
Capture as much thermal energy as possible.
| Produces hot waters which is used domestically to save the use of electrical energy.
56
What are the advantages of solar power?
Clean production
Renewable
Source of energy is free.
57
What are the disadvantages of slower power?
Utilised only in the day
Unreliable (cloudy day)
Need to cover a large area for a significant amount of energy.
58
What is hydroelectric power and the ways to achieve it?
Using the G.P.E of water to generate electrical energy.
Water can gain G.P.E by:
Water cycle and storing rainfall in large reservoirs high up.
Tidal power - trap water at high tide and release at low tide.
Pumping water from low to high reservoirs.
Pumping storage - large scale method to store energy.
59
What is the flow diagram of hydroelectric power?
G.P.E of water ----> K.E water + K.E of turbines ----> electrical energy
60
What are the advantages and disadvantages to hydroelectric power?
Clean production
Renewable
Source of energy is free
Only unitised in certain areas
Construction of dams involves land being submerged under water
61
Where does the kinetic energy of wind come from?
Temperature differences cause pressure pressure differences, due to hot air rising and cold air falling, thus air flows.
62
What is the flow diagram for the energy of a wind turbine?
Solar energy ----> K.E of wind ---> K.E of turbine---> electric energy.
Lots of energy is lost due to friction.
63
What are the equations for the energy produced by wind turbines?
Area swept out by the blades = A = Pi x r^2
Volume of air that passes the turbine in one second = vA
v = wind speed
Mass of air passing through the turbine in one second = vAp
p = density of air
K.E over second = 1/2 Apv^3
64
What would happen if the wind speed doubled?
Not all air can be harnessed, so wind turbines cannot be 100% effective.
Doubling wind speed would increase the available power by 8.
65
What are the advantages and disadvantages of wind power?
Clean production
Renewable
Source of energy is free
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Unreliable
Large area would need to be covered for a significant amount of energy
Spoil the countryside
Noisy
Often far from centres of population
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66
What is the aim with renewable energy sources?
Development with renewables will decrease the dependance on fossil fuels, as they are 90% of the worlds energy consumption.
Dependancy will continue but hopefully decrease with also the development of improving efficiency.
67
What are primary and what are secondary sources of energy?
Primary: fossil fuels - coal, oil, natural gas and renewables
Not convenient for individual users
Secondary: one that can be widely used in society
Electrical energy/ refined fuels (e.g petrol)
68
What is the challenge with secondary sources?
Storing electrical energy as everyday devices (batteries etc) have limited capability, when compared to everyday demands.
Only pumped storage hydroelectric systems are viable large-scale method of storage spare electrical energy for future use.
69
What's the efficiency of a typical storage?
75% which means 1/4 of energy supplied is wasted.
70
What are the three types of thermal energy transfer?
Radiation, convection and conduction.
| In any practical situation will involve more than one of these processes occurring at the same time.
71
What is evaporation?
Faster moving molecules leaving the surface of a liquid that is below its boiling point. It causes cooling.
72
What is conduction?
Energy is transferred without any bulk movement of the substance.
K.E is passed from molecule to molecule.
Faster moving molecules at the hot end pass their K.E to the slower moving ones by intermolecular collisions.
73
What are good and bad insulators?
Poor conductors are thermal insulators.
Metals are good conductors, allowing quick transfers of thermal energy.
Gases (and most liquids) are poor conductors.
74
What is an example of conductors and insulators?
Clothes keep us warm by trapping layers of air.
| Saucepans conduct thermal energy from the source of heat to the food.
75
What is convection?
It can only take place in a fluid.
When a fluid is heated it expands thus its density is reduced. The colder fluid sinks and the hotter fluid rises up. A convection current is created.
76
What are examples of convection currents?
Central heating
| Pilots of gliders and birds use convection currents to stay above the ground.
77
What is radiation?
All objects with a temperature above 0k radiate electromagnetic waves.
It's in the IR part of the electromagnetic spectrum.
Objects at constant room temperature absorb and radiate energy at a constant rate.
If an object is a good radiator then it will also be a good absorber.
It can travel through a vacuum
78
How does a change in colour and surface affect the objects radiation and absorption?
Lighter colour and smooth/shiny surfaces are poor radiators and absorbers
Darker colours and rough surfaces are good radiators and absorbers.
79
What happens if the temperature of an object increases?
Frequency of the radiation increases, thus the total rate of radiation also increases.
80
What is an example of radiation?
The Sun warms up the Earth's surface by radiation
81
What is the perfect emitter called and why?
Black-body radiation because a black object absorbs all of the light energy falling on it.
82
What does a black-body radiation depend on?
Depends on its temperature as at different temperatures there are a range of wavelengths and some are more intense than others.
83
What is the graph that shows the different intensities of different wavelengths?
Violet light has the highest intensity, red light has the lowest.
The area under the graph gives the intensity emitted in that wavelength range.
The total area under the graph is a measure of the total power radiated.
84
What is the equation for the total power radiated?
P = ō AT^4
```
P = total power radiated
ō = Stefan - Boltzmann constant
A = surface area in m^2
T = absolute temperature in Kelvins
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85
Are stars and planets perfect emitters?
No, but their radiation spectrum is approximately the same as black-body radiation.
86
What does Wien's Law state?
The wavelength (max) x T = constant
Wavelength (max) = intensity of the radiation is a maximum - IN METRES
T = temperature of a black-body - IN KELVINS
87
What is the value of the constant in Wien's law?
2.9 x10^-3 m K
88
How can we calculate a value for the surface temperature of a star?
Hot stars give out all frequencies of visible light and so will appear white in cloud
Cooler starts give out lower frequencies of visible light so they will appear red.
89
What is intensity and the equation for it?
Power per unit area that is received by the object.
Unit: W m^-2
I = power / A
90
What is thermal equilibrium?
If the temperature of a planet is constant, power being absorbed is at equal rate of energy being radiated.
91
What happens if a planet isn't in thermal equilibrium?
If it absorbs more energy than it radiates its temperature must go up.
If the rate of loss of energy is greater than its rate of absorption then its temperature must go down
92
What is emissivity?
The ratio of:
power radiated per unit area by an object, to the power radiated per unit area by a black body at the same temperature.
It's has no units
Equation on pg.90 of study guide
93
What is albedo?
Some of the radiation received by a planet is reflected straight back into space. The friction that is reflected back is called the albedo.
94
What is Earth's albedo?
It varies daily and depends on the season and latitude.
Oceans have low values and snow has a high value.
The global average 0.3 (30%).
95
What is the equation for albedo?
a = total scattered power / total incident power
96
What is the solar constant?
Amount of solar energy that falls per second on an area of 1m^2 above the Earths atmosphere that is at right angles to the Sun's Rays.
It's average value is 1400 Wm^-2
97
What occurs to the solar radiation on different parts of the Earth's surface?
Regions with different latitudes receive different amounts of solar radiation. It also varies with the seasons as it affects how spread out the rays have become.
98
What does the radiation have to do at different altitudes?
In high latitudes the radiation has to be travelling through greater depth of atmosphere. When it reaches the surface it will spread out over a greater area than in lower latitudes.
99
What is the greenhouse effect?
Short wavelength radiation is received from the sun can causes the Earth's atmosphere to warm up. Earth then emits infa-red radiation (longer radiation) because it is cooler than the sun. Infa-red radiation is then absorbed by gases in the atmosphere and re-radiated in all directions.
100
What are green house gases?
Gases in the atmosphere that absorb infa-red radiation.
The net effect: the upper atmosphere and surface of Earth are warmed.
101
When will the Earth's surface temperature be constant?
When the rate of radiation energy equals the rate of absorption.
The green houses is a natural effect, which without the temperature would be much colder.
The moon is -30 degrees colder than Earth.
102
How is the greenhouse gas methane produced?
Principal component of natural gas
Product of decay, decomposition or fermentation
Livestock and plants produce methane
103
How is the greenhouse gas carbon dioxide produced?
Combustion releases
| Carbon fixation: Plants remove co2 from the atmosphere during photosynthesis
104
How is the greenhouse gas nitrous oxide produced?
Livestock and industries are major sources
| It remains in the atmosphere for long periods of time
105
What is the ozone layer?
Region of the atmosphere that absorbs high energy UV photons which can harm living organisms. It adds to the green house effect.
106
What are chlorofluorocarbons? (CFCs)
Used as refrigerants, propellants and cleaning solvents.
| Deplete the ozone layer
107
Why do greenhouse gases worsen the greenhouse effect?
They absorb infa-red radiation as a result of resonance.
| Natural frequency of oscillations of the bonds within molecules of the gas are in the infa-red region.
108
When does resonance occur in the greenhouse gases?
The driving frequency (from the radiation emitted from Earth) is equal to the natural frequency of the molecule.
If the amplitude of molecules vibrations increases so will there temperature. The absorption will take place at specific frequencies depending on the molecular energy levels.
109
What are some of the main reasons for the increase in global warming ?
Changes in: the composition of greenhouse gases
Intensity of the radiation (maybe a increased solar flare activity)
Cyclical changes in the Earth's orbit and volcanic activity.
110
What is the enhanced greenhouse effect?
Increase in greenhouse effect caused by human activity
2013: IPCC (intergovernmental panel on climate change)
Increased combustion of fossil fuels has released extra CO2 into the atmosphere
111
What is the evidence for global warming?
Ice core in Russian Antarctic base at Vostok has been drilled into and the temperature can be estimated by Isotopic analysis. Air bubbles trapped in the core can be used to measure the atmospheric concentrations of greenhouse gases.
112
What are the effects of global warming?
Reduces ice/snow cover which reduces the albedo, so it increases rate of heat absorption.
Increase in temperature reduces solubility of CO2 in the sea, increasing atmospheric concentration. Also increase the release of CO2.
Increases evaporation and atmospheres ability to hold water vapour.
Deforestation reduces carbon fixation.
113
What's positive feedback?
A small initial temperature increases causes a further increase in the temperature.
114
What is the hope that negative feedback can cause?
Temperature increases can be "corrected" by this process and temperatures may fall in the future.
