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CPE430 Low Carbon Energy > Introduction and Greenhouse Effect > Flashcards

Introduction and Greenhouse Effect Flashcards

1
Q

Name four low carbon energy sources

A

Fossil fuels with CCS, solar, hydroelectric, wind

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2
Q

Name some low energy carbon sources that aren’t the main four

A

Nuclear, wave, tidal, geothermal, biomass

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3
Q

Why do we depend on fossil fuels so heavily?

A

They have a large power delivery

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4
Q

What is currently the biggest renewable energy source?

A

Hydroelectric

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5
Q

Where do the vast majority of energy sources come from?

A

Directly or indirectly from the sun

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6
Q

How does the energy in fossil fuels come from the sun?

A

Fossil fuels are stored solar energy as they are ancient biomass. The biomass has decayed and transformed over millions of years and stored the energy as carbon.

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7
Q

How much of the energy from the sun is converted in wind energy?

A

1-2%

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8
Q

How does wind power ultimately come from the sun?

A

Areas that receive more solar energy are hotter and the air less dense. This air rises and is replaced by cold air from neighboring regions and this is what causes wind.

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9
Q

How much more solar energy is converted into wind energy than into biomass by all the plants on Earth?

A

50 to 100 times

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10
Q

How does wave power ultimately come from the sun?

A

The wind that has been generated by the sun, generates waves due to the friction of the air moving over the surface of the sea.

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11
Q

How does hydroelectric power ultimately come from the sun?

A

Solar radiation drives the water cycle through evaporation of surface water. The water then falls on higher areas which provides it with the gravitational potential energy needed for hydroelectric power.

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12
Q

What are the three exceptions to energy coming from the sun?

A

Nuclear power, geothermal and tidal power.

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13
Q

How does biomass ultimately come from the sun?

A

Biomass uses solar radiation for photosynthesis by reacting with the chlorophyll in the plants (along with water and CO2) to create sugars that are converted into starch. This is a light-activated chemical reaction that generates high energy HC chains which we can then break down and release the energy from to produce electricity.

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14
Q

Describe where the energy comes from in nuclear power.

A

The energy comes from destruction or change of the fuel itself

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15
Q

Describe where the energy comes from in tidal energy.

A

The gravitational pull of the moon causes high tides when that side of the Earth is closest to the moon. This then drops as the Earth turns and gives tides.

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16
Q

Describe where geothermal energy comes from.

A

The core of the planet is hot because of the gravitational potential energy from the formation of the planet - plus a little bit of nuclear fission which happens to keep the core of the planet warm)

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17
Q

Why are fossil fuels not considered a renewable energy?

A

We are extracting it much faster than it is being made.

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18
Q

How much energy does the sun radiate to the Earth in kwh?

A

1.744x10^14 kwh per hour

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19
Q

How much energy does the sun radiate that reaches the Earth in watts?

A

1.744x10^17 watts

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20
Q

What is the conversion for Mtoe to kWh?

A

1 Mtoe = 1.163x10^10 kWh

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21
Q

What is the average worldwide energy consumption in 2017 in Mtoe and kWh?

A

13511 Mtoe = 1.57x10^14 kWh

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22
Q

How much of our consumed power was derived from fossil fuels in 2017?

A

80-90%

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23
Q

What was the annual energy consumption in 2012 in watts?

A

1.2x10^13 W

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24
Q

What does Mtoe stand for?

A

Mega tonne of oil equivalent

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25
Q

Can the energy from the sun provide us with our current energy demands?

A

Yes, but we are not using it properly.

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26
Q

Define direct radiation

A

When light does not interact with the atmosphere (what you see if you look directly at the Sun)

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27
Q

Define indirect radiation

A

Light that has been scattered in the atmosphere (on a day when you cannot see your shadow, all the radiation has been scattered and no direct radiation reaches you)

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28
Q

Define scattering

A

The term used to describe several processes such as reflection and refraction that can alter the direction that light is travelling

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29
Q

Define absorption

A

Electromagnetic radiation is taken up my molecules in the atmosphere through the transference of the energy to the electrons within the molecules, resulting in the generation of heat.

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30
Q

What emits electromagnetic radiation and what does it depend on?

A

Electromagnetic radiation occurs from all objects, the amount and wavelength depends upon its temperature (eg. the Sun is very hot so emits UV, visible light and IR)

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31
Q

Do hot or cool objects emit shorter wavelengths?

A

Hot objects

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32
Q

What temperature are the Sun and Earth and what wavelengths do they emit?

A

500 nm - short (Sun, 5525 K)

10,000 nm - long (Earth 290 K)

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33
Q

How can you tell how hot a piece of steel is?

A

By its colour

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34
Q

Why does the Earth’s surface cool down quicker on clear nights?

A

Because clouds (containing water) are strong absorbers and emitters of IR radiation

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35
Q

Why are nights colder at higher elevations?

A

There is less atmosphere to act as a ‘blanket’ and limit the amount of radiation leaving Earth.

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36
Q

What are the four parameters that determine scattering and absorption, what are they all a function of, and what do they give us in combination?

A

Refractive index (n), reflectance (R), transmission (T), absorbance (A). They are all functions of wavelength and in combination give us the greenhouse effect.

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37
Q

Define Rayleigh scattering

A

For wavelengths around 10^-4, particles are small compared to the to the wavelength of light

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38
Q

Why is the sky blue and sunsets red?

A

Rayleigh scattering is more effective at scattering shorter wavelengths (blue) so this is what we see during the day. At dusk and dawn when the Sun is further away, the blue light is so scattered by the time it reaches our eyes that all we see is the red that is left.

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39
Q

Define Mie scattering

A

This type of scattering depends on the shape of the molecule that is doing the scattering and occurs in particles about the same length as the wavelength of light (a few 100 nm), eg in fine clouds

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40
Q

Define geometric scattering

A

Occurs when the particle is much larger then the wavelength of light, (greater than 10x the wavelength), eg large water droplets in clouds

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41
Q

Which equations tell us how light is reflected and transmitted at a material interface?

A

The Fresnal equations

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42
Q

What do R, n1, n2, and T refer to in the Fresnal equations at near-normal incident radiation?

A

Reflected, refractive index of reflected radiation, refractive index of transmitted radiation, transmitted

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43
Q

Give the Fresnal equation for reflected radiation for near-normal incidence.

A

R = ((n1-n2)/(n1+n2))^2

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44
Q

Give the Fresnal equation for transmitted radiation for near-normal incidence.

A

T = 1-R

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45
Q

Give the two equations for Beer-Lambert Law

A

Absorbance=epsilon (extinction coefficient) x length x concentration=alpha (absorption coefficient) x length
absorbance = -log10(I/I0)

46
Q

Why is absorbance wavelength dependent?

A

All the energy will be absorbed at some wavelengths and none will be absorbed at others.

47
Q

What wavelengths does the optical spectrum cover?

A

UV-C (300 nm) to visible (400-700 nm) to IR (up to 1100 nm)

48
Q

Which three gases in the atmosphere attribute to the absorption of most visible and IR radiation?

A

Oxygen, ozone and water vapour

49
Q

Why do specific molecules only absorb specific wavelengths?

A

When the light is absorbed the energy is absorbed by a photon that then excites an electron. This excitation can only happen if there is a suitable energy level for the electron to be excited into, which depends on the molecule. This energy is then converted into heat or re-emitted.

50
Q

List the 10 processes that solar energy from the sun goes through.

A 
Atmospheric scattering
Atmospheric absorption
Cloud scattering
Surface reflection
Surface absorption
Surface radiation
Air conduction
Water vapour conduction
Absorption of radiated heat
Atmospheric radiation
51
Q

What is the greenhouse effect a result of and what does it cause?

A

It is a result of the complex wavelength dependent atmospheric absorption and emission effects. Therefore the atmosphere acts like the glass of a greenhouse - it lets light in but not the radiated heat out.

52
Q

Do greenhouse gases absorb visible light or IR radiation?

A

Only IR radiation

53
Q

What is the most significant anthropogenic GHG?

A

CO2

54
Q

Why do we need the greenhouse effect?

A

To keep our climate comfortable

55
Q

Why is water vapour not considered an anthropogenic greenhouse gas?

A

Humans change the amount of water vapour in the atmosphere very little

56
Q

Why have CO2 levels in the atmosphere increased so drastically?

A

Due to the industrial revolution

57
Q

What is the Keeling Curve?

A

It shows atmospheric CO2 concentrations from the Mauna Loa Observatory, Hawaii

58
Q

Why was the Mauna Loa Observatory chosen to measure atmospheric CO2 levels from?

A

It has a high altitude and is located where there is not much industrial activity so gives a good average reading.

59
Q

What causes seasonal variation in CO2 levels and which months are they at their highest and lowest?

A

When there is more sunlight available, photosynthesis occurs at a higher rate. This means plants ‘store’ some of the CO2 in the summer months and release it back to the atmosphere in the winter.
Highest - May
Lowest - Sept/Oct

60
Q

What is the general trend shown by the Keeling Curve?

A

Upwards curve with a slowly increasing gradient

61
Q

What can ice cores tell us about historic CO2 levels and how?

A

Ice cores show us that from about 1000 to 1750 CO2 levels were pretty constant, then they rapidly increase. As ice forms, atmospheric air is trapped as bubbles and these are preserved as more and more ice is formed on the top. The deeper the ice the older the air.

62
Q

How much have CO2 levels increased since 1900 and what is this attributed to?

A

30%, fossil fuel combustion and deforestation

63
Q

How long have humans been on Earth?

A

About 250,000 years

64
Q

When were atmospheric CO2 levels last this high?

A

800,000 years ago

65
Q

Where do N2O and CH4 come from?

A

Incomplete combustion, CH4 also from agriculture and decomposition of biomass

66
Q

What are the drivers of increasing global energy demand?

A

Population growth and increase in wealth

67
Q

How did the 2008 global financial crisis affect global energy demand?

A

It slowed the growth of demand as there was a turn down in energy usage

68
Q

Give some examples of aspects of civilization is energy needed for?

A

Housing construction, transporting people and goods, lighting, heating and cooling our homes, communications, industrial production, powering medical diagnostic and research equipment, preparation of food.

69
Q

Where is energy demand increasing the most rapidly and why?

A

‘Rest of the world’ ‘non-OECD’ locations (eg. China, India, Africa), as they work on reaching the standards of living similar to the UK, USA, Canada etc.

70
Q

What is the conversion from kWh to eV?

A

1 kWh = 2.247x10^25 eV

71
Q

How can a near-accurate model of the change in global surface temperature be achieved?

A

By adding together the effect of ‘El Nino’ (the upwelling of the Pacific Ocean causes temporary fluctuations in surface temperature), volcanic aerosols (volcanic eruptions cause dips in surface temperature due to release of sulphur aerosols blocking incoming solar energy by adding to the amount of particles in the atmosphere), incoming solar radiation (varies over a 7 year cycle), and a steadily increasing amount of anthropogenic emissions without which the model would not reflect reality.

72
Q

What temperatures/levels can we measure to demonstrate global warming?

A

Land surface air temperature, sea-surface temperature, marine air temperature, sea level, summer arctic sea-ice extent (this will decrease)

73
Q

What changes can we see on Earth due to global warming?

A

Rising sea levels, global temperature rise, warming oceans, glacial retreat, declining arctic sea ice, shrinking land ice sheets, extreme events, ocean acidification, decreased snow cover

74
Q

What ppm of CO2 in the atmosphere do we need to keep below in order to limit the eventual temperature change to 1.5 degrees?

A

400 ppm

75
Q

Give three examples of the effects of global warming in increasing temperature increase.

A

Coral reef ecosystems extensively and eventually irreversibly damaged, many species facing extinction, sea level rise threatens major world cities inc. London, Shanghai and New York

76
Q

What does THC stand for and what is it?

A

Thermohaline circulation, which is part of the large-scale ocean circulation

77
Q

What four steps will help us fight global warming?

A

Understand what the problem is, assess the possible solutions, make changes that will address the problem, start with the easiest options

78
Q

What is meant when we say we want to target the easy options for reducing CO2 emissions?

A

Capturing CO2 at static sources as you get a bigger win for implementing one piece of technology, or consumers making small changes such as turning of heating and lights when not needed

79
Q

How long would CO2 naturally sit in the atmosphere for?

A

200-300 years

80
Q

List the 9 steps of the carbon cycle

A
  1. Plants absorb CO2 from air to grow, and decompose to release Co2
  2. Iron-rich dust is blown by winds into the ocean and stimulates phytoplankton blooms
  3. Air and sea exchange CO2
  4. Phytoplankton take up CO2 to grow
  5. Zooplankton eay phytoplankton and respire CO2
  6. Some carbon sinks to the depths in the form of decaying biota and fecal pellets
  7. Only a small percentage of the sinking carbon reaches the deep sea. A tiny fraction is buried in the seafloor sediments. Most is recycled back to the surface 100-1,000 years later by the ocean’s circulation.
  8. Over millions of years, carbon in incorporated into rocks or turned into hydrocarbons
  9. Rocks are eventually uplifted onto land and weathered to release carbon to soils and the atmosphere
81
Q

Which step of the carbon cycle are we influencing the most?

A

We are extracting carbon and releasing it into the atmosphere much faster than would happen naturally

82
Q

How many pentograms of carbon/year are we adding to the atmosphere through coal, oil and gas?

A

6.5

83
Q

Which energy emissions contribute the first and second most CO2 to the atmosphere?

A

Power (24%) followed by industry and transport (14% each)

84
Q

Which non-energy emissions contribute the first and second most CO2 to the atmosphere?

A

Land use (18%) and agriculture (14%)

85
Q

List the following stationary source emissions from highest to lowest emission contributors: Ag processing, cement plants, electricity generation, ethanol plants, fertiliser, industrial, other, petroleum and natural gas processing, refineries/chemical

A

Electricity generation (83%), refineries/chemical (6%), industrial, petroleum and natural gas processing and cement plants, ethanol plants, fertiliser, other, Ag processing

86
Q

Name three assessment tools for identifying potential CO2 sources

A

Continuous emission monitoring, emission factors, emissions estimate equations

87
Q

What information is needed to carry out emissions estimate equations on a coal fired power plant?

A

Coal usage and calorific content - or educated guess work

88
Q

How do we decide which CO2 source assessment method to use?

A

If there is emission data available, use that, if there is not, calcualte it using fuel usage or production data in conjunction with a suitable CO2 conversion factor. It there is no data available, apply an estimate.

89
Q

Which is the fastest growing global fuel?

A

Gas

90
Q

Why is it important western society takes a lead role in reducing CO2 emission reduction?

A

We need to educate developing countries to put into place infrastructure for renewable energies as their energy use expands.

91
Q

By 2030, how much is it expected that emissions in developed and developing countries will increase?

A

Developed: 30%
Developing: 60%

92
Q

What are the two largest contributors to GHG emissions in the US?

A

Coal-fired power plants (27%) and petroleum-based transportation sources (28%)

93
Q

How can we offset unavoidable near-term emissions growth?

A

By beginning to make greater long-term reductions

94
Q

What will happen if the CO2 reduction techniques we employ are not drastic enough?

A

They will only buy us a few years in time and will only delay the accumulation growth

95
Q

Why do we not just cut out fossil fuels completely?

A

We do not currently have the required infrastructure in place

96
Q

Why must we discourage the development of new fossil-fuel processing facilities?

A

A new power station will be in place for 30-40 years so will have a huge long-term impact

97
Q

Give 4 options to minimise GHG emissions

A
  1. Energy efficiency improvements
  2. The shift to less carbon intensive fuels such as nuclear power and renewable energy sources
  3. Reduction of non-CO2 GHG emissions
  4. Changes in land use practices that currently result in global deforestation
98
Q

Which government review concluded that ‘the world has to act now or face devastating economic consequences’?

A

The Stren Review

99
Q

Which White Paper comitted to an 80% reduction in carbon dioxide emissions by 2050?

A

The UK Government Energy White paper

100
Q

For which agreement did members agree to reduce their carbon output as soon as possible and to do their best to keep global warming to well below 2 degrees?

A

The 2015 Paris Agreement

101
Q

What is the IPCC?

A

A special 2018 report that details the impacts of global warming above 1.5 degrees above pre-industrial levels

102
Q

How much could converting to higher efficiency conversion processes cut emissions by?

A

10-30%

103
Q

Why are France’s CO2 emissions so low?

A

They use mainly nuclear energy - 78% in 2008

104
Q

Why are Brazil’s CO2 emissions so low?

A

They use mainly hydroelectric power - 83% in 2004

105
Q

Name a medium term emission decrease solution.

A

CO2 capture and storage (CCS)

106
Q

Name a long term emission decrease solution.

A

Switching to low carbon fuel alternatives - replacement with natural gas, biomass co-firing, renewable energy supplies

107
Q

Which is happening faster - switching to low carbon fuel alternatives or implementing CCS?

A

Switching to low carbon fuel alternatives

108
Q

How does the development of new materials contribute to decrease of emissions?

A

It allows higher temperatures and pressures to be used which increases efficiency.

109
Q

How can using electric cars make carbon capture more feasible?

A

It transfers the CO2 burden back to the power station, where it is easier to capture the large amounts of emissions in one place.

110
Q

What is the optical window of wavelengths?

A

300 nm (UVC) into visible (400-700nm) to infrared (1100 nm)

CPE430 Low Carbon Energy (6 decks)

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