Energy on planet earth

1
Energy on planet earth

• Sources of energy on earth?
• Surface
• Solar radiation
• Extra solar radiation (very very small)
• Very well understood
• Core
• Radioactive decay of earths core elements (up to
  90)
• Core cooling (left over gravity) (5-10)
• Gravity (friction between elements of different
  density) (5)
• Latent heat from expansion of cooling materials
  (small)
• Not so well understood!

Source www.physorg.com/news62952904.html
2
2 more obscure sources?

• Earths rotation
• Coriolis effect trade winds and ocean currents
• Moon
• Tides

3
Thermhaline current global conveyor belt

• Color key is NOT temperature!

4
Radioactive heating of earths core

• Radioactivity involves the decay of unstable
  nuclei of atoms
• In the earths core, these are mainly Uranium,
  Thorium and Potassium
• Potassium is also the main source of human
  radioactive exposure
• Earth core total heat generation estimated30 -
  44 TW (1 TeraWatt 1012 Watts)
• Radioactive component measured in 2005 through
  antineutrino detection by KamLAND (Japan)24 TW
  
• 10 TW 1990 global fossil fuel use

Sources http//athene.as.arizona.edu/lclose/teac
hing/a202/ NewScientist, July 27 2005
5
Radioactive decay chains
Radioactive decay of heavier nucleiFrom
http//commons.wikimedia.org
6
Some solar numbers

• Sun mass 2 x 1030 kg 333 thousand earth
  masses
• Sun radius 7 x 108 meters 100 x earths
  radius
• Sun-Earth distance 150 x 109 metersroughly
  2000 x earths radius
• Density 1.4 tonnes / cubic meter 25 as
  dense as the earth
• Surface temperature 5778 KelvinEarth surface
  temp 287 Kelvin (14 Celsius)
• Power radiated (Luminosity) 3.851026 W

7
Solar radiation on earth

• Total power radiated 3.851026 W
• Power density at earths orbit 1367 W/m2
  SOLAR CONSTANT
• Actually not a constant, increased by 30 over 3
  billion years of life on earth!
• Stability of climate during this time is one
  basis of Gaia hypothesis.
• Average power density at earth upper atmosphere
  342 W/m2
• Because of earth is rotating sphere, divide solar
  constant by 4.
• Reaching the ground 240 W/m2
• Total 122 PW 122 x 1015 Watts
• Compared to 30-44 TW from earth core heating

8
Spectral qualities of solar radiation

• Light (or radiation) is characterized by
  wavelength/frequency (colour) and intensity.
• Spectrum is the shape of the intensity vs.
  wavelength
• Wavelength and frequency are directly related to
  each other
• wavelength (speed of light) / frequency
• speed of light 299792458 meters / second
• Higher frequency gt higher energy
• Higher wavelength gt lower energy
• Black body radiation means the relation between
  the wavelength and the intensity are determined
  by the temperature of the radiating object alone
• All objects at the same temperature have the same
  black body spectrum.
• Solar spectrum is Black body radiation at 5800
  Kelvin

9
Perfect black body
The most perfect black body radiation ever
measuredThe cosmic microwave background
radiation at 2.725 Kelvin
1 / wavelength
10
nanometer 10-9 meter
Source http//en.wikipedia.org/wiki/Solar_radiati
on
11
Energy distribution of solar spectrum
Wavelength (nanometer 10-9 meter) Percentage of total energy
lt 300 X-rays and gamma rays 1.2
300-400Ultra-Violet 7.8
400-700Visible 38
700-1500Infrared 38.8
gt 1500Microwaves, Radio waves 12.4
12
Source Nasa ERBE
13
Global radiation flows
Source Smil, General Energetics
14
Uses for all this radiation

• 300 Kelvin planet water is liquid!
• Visible light energy which can be used by
  autotrophs

15
Solar radiation and core heatSecondary
phenomena energy sources

• Wind, tornadoes, hurricanes, jet streams (in part
  due to earths rotation)
• Waves, ocean currents (in part due to earths
  rotation)
• Tides (due to moon)
• Earthquakes, volcanic eruptions, tsunamis
• Global water cycle (rain, snow, rivers, glaciers,
  erosion)
• Requires 40 PW (third of solar radiation)
• Geothermal energy

16
Global water cycle flows
Units W/m2 (I think)
Source Smil, Energies
17
Global Wind Flows
Source Smil, Energies
18
Wind and extractable energy
Power (Watts)
Source Smil, Energies
19
Thoughts on global energy processes

• Small number of primary sources (sun, moon,
  rotation, core heat)
• Energy is transferred and reused in many ways
  once it reaches the lithosphere-atmosphere
• Movement of masses (tectonic plates, water, ice,
  crust, air)
• Transfer of temperatures (water, absorption and
  re-radiation of light, volcanic eruptions and
  geothermal processes)
• Sorting of matter based on density.
• Life on earth is based on taking advantage these
  energy various energy flows.

20
Some biology vocabulary

• Biomass mass or energy of organisms (living or
  ex-living) per unit area of land or unit volume
  of water
• Units J/m2 or tonne/hectare
• Phytomass plant biomass (stock)
• Autotroph organism which does not feed on other
  organisms, but relies on chemical, thermal or
  radiation energy in its environment producers in
  the food chain
• Plants, some bacteria
• Heterotroph organism which feeds on organic
  matter created by other organisms consumer in
  the food chain
• Everyone else
• Primary production rate of phytomass production
• Units J/m2/day or tonne/hectare/year
• Secondary production rate of non-plant biomass
  production

21
Troph flow chart
No
Yes
Carbon from CO2?
Autotrophs
Heterotrophs
22
Life on earth

• When? 3.5 billion years ago (Archean era)
• Sun earth 5 billion years old and another 5
  billion to go.
• Who? Prokaryotes Archaea autotrophs
• Lots of CO2 in atmosphere, sequestered to CaCO3
  (limestone)
• Inorganic geochemical processes?
• Early life forms?
• Missing in atmosphere? O2

23
Atmospheric composition
Photosynthesis
Source Smil, Energies
24
Absorption of terrestrial radiation
Peak of earthradiation at 300K
Source Smil, Energies
25
Photosynthesis primary production

• Plant input Carbon dioxide water sunlight
• CO2 H2O light
• Plant output Carbohydrate oxygen water
• CH2O O2 H2O
• Carbon is fixed in plant,
• providing food for heterotrophs
• Oxygen is released intoatmosphere
• Why do plants do it?

26
CO2 Carbondioxide
CH4 Methane
Source J. Siirola, GRC 2006
27
Carbon oxidation states, cont.
28
Efficiency of photosynthesis

• Efficiency of photosynthesis stored chemical
  energy / incident sunlight
• Factors influencing efficiency
• (1) Theoretical constraints
• Only 43 of incident sunlight is
  Photosynthetically Active Radiation (PAR),
  wavelengths 400-700 nm
• Chemical reaction efficiency of carbon
  assimilation is 90
• Quantum probability requirements of light per
  molecule 30
• Total theoretical efficiency 12
• (2) Practical constraints
• Light reflected from transmitted through leaf
  surface 10-25
• Angle of leaf to sunlight is often not 90, often
  not direct sunlight
• Energy costs of respiration (40), rapid rates of
  photosynthesis
• Plant metabolic processes (maintenance, growth,
  reproduction)
• Only get 50 - 2 of best theoretical
  performance
• Total photosynthetic efficiency is 6, most often
  lower

29
Limiting factors of photosynthesis

• Water availability
• C3 and C4 photosynthesis
• C4 in warmer, dryer climates
• Nutrient availability
• Managed ecosystems (agriculture) are more
  productive.

30
Primary production

• Numerous intricacies of photosynthetic
  energetics remain unknown but certainly one of
  the most surprising weaknesses in our knowledge
  of life is our patchy understanding of phytomass
  stores and productivities. Our lack of
  satisfactory appraisal of photosynthesis on
  planetary and ecosystemic scales is more
  troubling than remaining gaps in our biochemical
  understanding.
• Vaclav Smil, General Energetics Energy in the
  Biosphere and Civilization, 1991

31
Accounting for primary production

• Gross primary production GPP total fixation of
  carbon by autotrophs (primary producers)
• Autotrophic respiration RA lost energy
• Heterotrophic respiration RH
• Total ecosystem respiration RE RA RH
• Net Primary Production NPP rate of production of
  new biomassNPP GPP - RA
• Net Ecosystem Productivity NEP GPP RE
• NEP gt 0 Ecosystem is carbon sink
• NEP lt 0 Ecosystem is carbon emitter

32
Trophic Model - Odum
I Input, ingested energy NU not used A
assimilated energy P Production R
Respiration B Biomass G Growth S
Stored Energy E Excreted Energy
Courtesy of Karlheinz Erb
33
Energy Flow through Ecosystems
Courtesy of Karlheinz Erb
34
Ecological Parameters and Succession
Courtesy of Karlheinz Erb
35
The Trophic System of different Ecosystems
Courtesy of Karlheinz Erb
36
The Trophic Net
Courtesy of Karlheinz Erb
37
NPP - Methods of Assessment

• short term harvest technique - harvest an area
  (quadrats) at short term intervals to get NPP
• PN ? B D C
• where D death, C consumption and
• ? B Bt Bt-1

Courtesy of Karlheinz Erb
38
NPP Correlation with Climate
Courtesy of Karlheinz Erb
39
ANPP of the World Ecosystems
Courtesy of Karlheinz Erb
40
Human Appropriation of Net Primary Production -
Components

• NPP0 NPP of the potential vegetation (i.e.
  absence of human interference)
• NPPact NPP of the actual vegetation
• NPPh Harvest of NPP
• NPPt NPP remaining in ecosystem after harvest
• NPPt NPPact - NPPh
• HANPP NPP0 NPPt NPPt/NPP0
• HANPP NPP0 NPPact NPPh

Courtesy of Karlheinz Erb
41
Human Appropriation of Net Primary Production
Courtesy of Karlheinz Erb
42
Courtesy of Karlheinz Erb
43
Courtesy of Karlheinz Erb
44
NPP and the Carbon Cycle
Courtesy of Karlheinz Erb
45
The Global Carbon Cycle
Courtesy of Karlheinz Erb
46
Heterotrophs

• Heterotrophs eat, breathe, excrete and emit
  energy
• Food ingested, then absorbed or excreted
• Energy costs for basal active metabolism
• Basal functions temperature maintenance, organ
  function
• Activity needed to capture food.

47
Basal metabolic rate Kleibners w3/4 law

• Geometric considerations can explain the ¾
• diameter of limbs goes as mass3/8
• Power output of muscles goes as diameter2
• Power goes as mass3/4

70 kg
Source Smil, General energetics
48
BMR of humans
kcal / day
80 W
50 W
(Harris Benedict, 1919)
49
BMR by organ
Source Durnin 1981 http//www.fao.org/DOCREP/MEE
TING/004/M2845E/M2845E00.HTM
50
Human food energy requirements
Smil, Energies
51
Human BMR vs. gender, age
from Mitchell, 1962
52
Energy costs of motion (food capture)
Source Smil, General energetics
53
Energy cost of human activities
Source Smil, Energies
54
Walking-Biking-Driving (part 2)
Conclusion if you are an average American (or
Swiss) meat-eater,it may be more efficient to
drive a Smart than to walk ...
55
Energy cost of motorized food gathering
USA Person 70 kg, 1 km distance Walking Biking   Sitting (1 minute) Average Car (gasoline) Smart Car (diesel)
Speed (km/h) 5 20   60 60 60
Person Energy used (MJ/km) 0.2 0.1   0.012    
Car Gasoline or Diesel (litre/100km)         9 4.2
Car Gasoline Equivalent (litre/100km)         9 5.4
VEGETARIAN Plant-based energy (MJ/km) 0.3 0.1   0.02    
VEGETARIAN Fossil Energy (MJ/km) 0.8 0.3   0.05    
VEGETARIAN Gasoline Equivalent (litre/100km) 2.0 0.6     9.1 5.5
CARNIVOROUS Plant-based energy (MJ/km) 1.5 0.5   0.09    
CARNIVOROUS Fossil Energy (MJ/km) 1.6 0.5   0.09    
CARNIVOROUS Gasoline Equivalent (litre/100 km) 4.1 1.3     9.3 5.6
3 MJ fossil/ MJ veg.
25 loss crude to gasoline
½ veg½ meat
6 MJ fossil/ MJ meat
56
USA Person 70 kg, 1 km distance Walking Biking   Sitting (1 minute) Average Car (gasoline) Smart Car (diesel)
Speed (km/h) 5 20   60 60 60
Person Energy used (MJ/km) 0.2 0.1   0.012    
Car Gasoline or Diesel (litre/100km)         9 4.2
Car Gasoline Equivalent (litre/100km)         9 5.4
VEGETARIAN Plant-based energy (MJ/km) 0.3 0.1   0.02    
VEGETARIAN Fossil Energy (MJ/km) 0.8 0.3   0.05    
VEGETARIAN Gasoline Equivalent (litre/100km) 2.0 0.6     9.1 5.5
CARNIVOROUS Plant-based energy (MJ/km) 1.5 0.5   0.09    
CARNIVOROUS Fossil Energy (MJ/km) 1.6 0.5   0.09    
CARNIVOROUS Gasoline Equivalent (litre/100 km) 4.1 1.3     9.3 5.6
3 MJ fossil/ MJ veg.
25 loss crude to gasoline
½ veg½ meat
6 MJ fossil/ MJ meat