GCEP Annual Research Symposium
New Research Directions in a Rapidly Evolving Global Energy
LandscapeSeptember 30 - October 2, 2009
STANFORD UNIVERSITY
Exergy and Carbon Flow in Natural and
Human SystemsRichard Sassoon
Global Climate & Energy Project
2
The Technology Challenge
We need a portfolio of new technologies to achieve these CO2 emissions reductions while meeting growing energy demands.
Historical Emission Data
ed a portfolio of new ologies to achieve these ions while meeting g energy demands.
1860
Peak
80% decreasefrom 2000
1990 Levels
1960 2060Em
issi
ons
(GT
CO
2)
10
20
30
Historic Data
Needed Reductions
Historical Emission Data
ed a portfolio of new ologies to achieve these ions while meeting g energy demands.
1860
Peak
80% decreasefrom 2000
1990 Levels
1960 2060Em
issi
ons
(GT
CO
2)
10
20
30
Historic Data
Needed Reductions
3
Motivation for Exergy Analysis
• As we consider future energy technology choices for addressing this challenge, we need:
a consistent basis for comparing energy resources and their conversions in terms of their thermodynamic potential; andan understanding of the impact they will have on the global carbon cycle.
• Exergy and carbon maps can serves as a useful data source in:
Determining new research directionsFormulating future energy policiesEducating the public
• As we consider future energy technology choices for addressing this challenge, we need:
a consistent basis for comparing energy resources and their conversions in terms of their thermodynamic potential; andan understanding of the impact they will have on the global carbon cycle.
• Exergy and carbon maps can serves as a useful data source in:
Determining new research directionsFormulating future energy policiesEducating the public
4
• Exergy is the useful portion of energy that allows us to do work and perform energy services.
• Energy is conserved, but exergy is not.
• Exergy is available only in materials and flows we call resources and is converted into exergy carriers convenient to use in our homes, vehicles, and factories
• Exergy is calculated from thermodynamic properties of a substance relative to the properties of a reference environment
• Exergy is the useful portion of energy that allows us to do work and perform energy services.
• Energy is conserved, but exergy is not.
• Exergy is available only in materials and flows we call resources and is converted into exergy carriers convenient to use in our homes, vehicles, and factories
• Exergy is calculated from thermodynamic properties of a substance relative to the properties of a reference environment
Concept of Exergy
Chemical Fuel Vehicle
Propulsive Work
Hot Exhaust Gases
5
Data in the maps are of three types: Data in the maps are of three types:
Components of Exergy and Carbon Data
•• CarriersCarriers are mediums through which exergy and/or carbon flow through the system.
The flow of exergy and carbon through carriers is measured in units of watts (joules/second) and grams/second, respectively.
•• TransformationsTransformations are processes by which exergy and carbon are passed from one carrier to another.
A loss of exergy is incurred due to inherent inefficiencies of energy conversion but the total mass of carbon is conserved throughout the system.
•• AccumulationsAccumulations are stores of exergy and/or carbon, measured in units of joules and grams, respectively.
Maybe primary resources or intermediate stores
6
What resources can we use? Exergy flow of planet Earth (TW)
7
Renewable Global Exergy Flows
0.1
1
10
100
1000
10000
SolarWind
Ocean Thermal G
radient
Waves
Terrestr
ial Biomass
Ocean Biomass
Geothermal H
eat Flux
HydropowerTides
Exergy sources scaled to average consumption in 2004 (15 TW)From Hermann, 2006: Quantifying Global Exergy Resources, Energy 31 (2006) 1349–1366
HumanUse of Energy(15 TW)
8
Global Exergy Stores
From Hermann, 2006: Quantifying Global Exergy Resources, Energy 31 (2006) 1349–1366
0
1
10
100
1000
10000
100000
Geothermal E
nergy*
Deuterium–trit
ium (from Li)
Uranium
Thorium
Coal
Gas Hydrates Oil
Gas
Yearly Human Consumptio
n
Exer
gy (
ZJ)
9
Global Exergy and Carbon Flows
Source: W. Hermann, GCEP Systems Analysis Group 2004.
10
Global Carbon Flows from Energy Service Sectors of the Human Energy System (Mg C/s)
Agriculture and Forestry, 190
Resource Production, 21
Transportation, 59
Material Processing and Manufacturing,
153
Heating and Cooking, 52
Electricity Services, 105
1 MgC/s =
31.5 MtonneC/yr)
11
Global Carbon Emissions versus Process Exergy Destruction
Agriculture
Forestry
Charcoal Production
Oil and Gas Extraction
Aircraft
Road and Rail
Shipping
Pipeline Transport
Chemical Production
Ethanol Production
Metal Purification
Non‐Metallic Mineral Processing
Natural Gas Processing
Food Processing
ManufacturingPetroleum Refining
Paper Prodduction
Metabolism
Solid Waste Conversion
Chemical Production
Indoor Air Heating
Lighting
Food Cooking
Water Heating
Electricity from Coal
Electricity from Methane
Electricity fromSolid Biofuel
Liquid Fuel Electricity
5.80
6.30
6.80
7.30
7.80
10.3 10.8 11.3 11.8 12.3 12.8 13.3
Log (Process Exergy Destruction (TW))
Log (Carbo
n Em
ission
s (M
gC/s))
Agriculture & Forestry
Resource Production
Transportation
Materials Processing
Heating and Cooking
Electricity Services
12
Relative Fractions of Global Exergy Destruction and Carbon Flows
0%
25%
50%
75%
100%
Process Emissions(Gt-C/year)
Exergy Destruction (TW)
Perc
ent C
ontr
ibut
ion
Electricity - Solid Biofuel
Electricity - Methane
Electricity - Liquid Fuel
Electricity - Coal
Water Heating
Food Processing
Food Cooking
Lighting
Indoor Air Heating
Landfill and Solid Waste Conversion
Paper Production
Steam Production
Chemical Production
Manufacturing and Mineral Processing
Ethanol Production
Charcoal Production
Coal Transformation
Coal Mining
Natural Gas Processing
Petroleum Refining
Pipeline Transport
Oil and Gas Extraction
Shipping
Aircraft
Road and Rail
Electricity - Coal
13
Global Exergy Destruction and Carbon Flow in the Electricity Sector
• The electricity sector is dominated by coal in terms of exergy destroyed and carbon emissions.
• The electricity sector is dominated by coal in terms of exergy destroyed and carbon emissions.
0.0
1.0
2.0
Exe
rgy
Des
troye
d (T
W)
Exergy Destruction
0%
50%
100%
Effi
cien
cy (%
)
Process Exergy Efficiency
0
30
60
90C
arbo
n R
elea
sed
(Mg
C/s
)
Carbon Release to Atmosphere
Electricity from Coal
Electricity from Methane
Liquid Fuel Electricity
Electricity from Solid Biofuel
Solar Electricity
Hydroelectricity Conversion
Wind Energy Conversion
Nuclear Pow er Plants
Geothermal Electricity
Tidal Electricity
14
Global Exergy Destruction in the Transportation Sector
0.0
0.5
1.0
1.5
2.0
2.5
Exer
gy D
estro
yed
(TW
)
Road a
nd R
ail
Aircraf
t
Shippin
g
Pipelin
e
Exergy Destruction
• Road and rail accounts for largest destruction of exergy in the global transportation system and this transformation occurs with the lowest efficiency
• Road and rail accounts for largest destruction of exergy in the global transportation system and this transformation occurs with the lowest efficiency
0%
10%
20%
30%
40%
Effic
ienc
y (%
)
Road a
nd R
ail
Aircraf
t
Shippin
g
Pipelin
e
Process Exergy Efficiency
15
Global Carbon Flows in the Transportation Sector
• Road and rail also accounts for greatest CO2 releases in the transportation sector
• Road and rail also accounts for greatest CO2 releases in the transportation sector
0
2
4
6
8
10
C p
er E
xerg
y in
Pro
duct
(Mg
C/s
per
TW
)
Road a
nd R
ail
Aircra
ft
Shippin
g
Pipelin
e
Carbon Release per Exergy in Product
0
10
20
30
40
50
Car
bon
Rel
ease
d (M
g C
/s)
Road a
nd R
ail
Aircra
ft
Shippin
g
Pipelin
e
Carbon Release to Atmosphere
0
10
20
30
C p
er E
xerg
y D
estro
yed
(Mg
C/s
per
TW
)
Road a
nd R
ail
Aircraf
t
Shippin
g
Pipelin
e
Carbon Release per Exergy Destroyed
16
Global Exergy Destruction and Carbon Flows from Agriculture and Forestry
• Although not deployed primarily for energy production, agriculture and forestry represent significant pathways for exergy destruction within the human exergy system
• Although not deployed primarily for energy production, agriculture and forestry represent significant pathways for exergy destruction within the human exergy system
0
50
100
150
Car
bon
Rel
ease
d (M
g C
/s)
Agricultu
re
Forestry
Carbon Release to Atmosphere
0.0
2.0
4.0
Exe
rgy
Des
troye
d (T
W)
Agricultu
re
Forestry
Exergy Destruction
17
Global Exergy Destruction and Carbon Flows for Heating, Lighting, and Cooking
• Very low conversion efficiencies
• Very low conversion efficiencies
0.0
0.4
0.8
1.2
Exe
rgy
Des
troye
d (T
W)
Lighting
Indoor A
ir Heati
ngWater H
eating
Food Cookin
g
Exergy Destruction
0
10
20
30
Car
bon
Rel
ease
d (M
g C
/s)
Lighti
ngInd
oor A
ir Hea
ting
Water H
eating
Food C
ookin
g
Carbon Release to Atmosphere 0%
4%
8%
12%
Effi
cien
cy (%
)
Lightin
gInd
oor A
ir Heati
ngWater
Hea
ting
Food C
ookin
gProcess Exergy Efficiency
18
Future Analysis
• Maintain data with annual updates• Deeper analysis of exergy destruction and carbon emissions, e.g.:
segmented across geographic regionsalong specific energy pathways
• Define future scenarios and set parameters for technology pathways to achieve them, e.g.;
sustainable transportation systemsustainable electricity delivery system
• Develop new flow charts for:Other greenhouse gases and materials (CH4, N2O, particulate matter, etc.)Global warming potential
• Add time component to charts to yield a picture of the level of sustainability of global energy use.
• Develop user friendly web interface for exergy and carbon flow data.
• Maintain data with annual updates• Deeper analysis of exergy destruction and carbon emissions, e.g.:
segmented across geographic regionsalong specific energy pathways
• Define future scenarios and set parameters for technology pathways to achieve them, e.g.;
sustainable transportation systemsustainable electricity delivery system
• Develop new flow charts for:Other greenhouse gases and materials (CH4, N2O, particulate matter, etc.)Global warming potential
• Add time component to charts to yield a picture of the level of sustainability of global energy use.
• Develop user friendly web interface for exergy and carbon flow data.
19
Conclusions
• The transition to energy systems with much lower GHG emissions is one of the grand challenges we humans must face in this century.
• Carbon is currently being reintroduced to the biosphere through the human use of fossil fuels at a rate far exceeding its natural sequestration.
• Presented methodology for quantifying and linking together the major flows of exergy and carbon at a global level
• Can identify the energy conversions with potential to significantly impact the relationship between human exergy use and CO2 emissions.
• Data provide a framework for analyses of the impacts of various technological advances and policy initiatives that could enable or encourage increased exergy efficiency or new energy pathways.
• The transition to energy systems with much lower GHG emissions is one of the grand challenges we humans must face in this century.
• Carbon is currently being reintroduced to the biosphere through the human use of fossil fuels at a rate far exceeding its natural sequestration.
• Presented methodology for quantifying and linking together the major flows of exergy and carbon at a global level
• Can identify the energy conversions with potential to significantly impact the relationship between human exergy use and CO2 emissions.
• Data provide a framework for analyses of the impacts of various technological advances and policy initiatives that could enable or encourage increased exergy efficiency or new energy pathways.
20
Acknowledgments
Wes HermannI-Chun HsiaoLjuba MiljkovicA.J. SimonEmilie HungPaolo BosshardJenny MilneSally M. BensonLynn Orr
