Exergy and Carbon Flow in Natural and Human Systems

Transcription

1 Exergy and Carbon Flow in Natural and Human Systems Richard Sassoon Global Climate & Energy Project GCEP Annual Research Symposium New Research Directions in a Rapidly Evolving Global Energy Landscape September 30 - October 2, 2009 STANFORD UNIVERSITY

2 The Technology Challenge Historical Emission Historic Data Data ed a portfolio of new ologies to achieve these ions 30 while meeting g energy demands. Emissions (GT CO 2 ) Needed Reductions Peak 1990 Levels 80% decrease from We need a portfolio of new technologies to achieve these CO 2 emissions reductions while meeting growing energy demands. 2

3 Motivation for Exergy Analysis As As we consider future energy technology choices for for addressing this challenge, we need: a consistent basis for for comparing energy resources and and their their conversions in in terms of of their their thermodynamic potential; and and an an understanding of of the the impact they they will will have on on the the global carbon cycle. Exergy and carbon maps can serves as as a useful data source in: in: Determining new new research directions Formulating future energy policies Educating the the public 3

4 Concept of Exergy Exergy Exergy is is the the useful useful portion portion of of energy energy that that allows allows us us to to do do work work and and perform energy energy services. Energy Energy is is conserved, but but exergy exergy is is not. not. Chemical Fuel Vehicle Propulsive Work Hot Exhaust Gases Exergy Exergy is is available only only in in materials and and flows flows we we call call resources and and is is converted into into exergy exergy carriers carriers convenient to to use use in in our our homes, homes, vehicles, and and factories Exergy Exergy is is calculated from from thermodynamic properties of of a substance relative relative to to the the properties of of a reference environment 4

5 Components of Exergy and Carbon Data Data in the maps are of three types: Data in the maps are of three types: Carriers 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. Transformations 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. Accumulations are stores of exergy and/or carbon, measured in units of joules and grams, respectively. Maybe primary resources or intermediate stores 5

6 What resources can we use? Exergy flow of planet Earth (TW) 6

7 Renewable Global Exergy Flows Human Use of Energy (15 TW) Solar Wind Ocean Thermal Gradient Waves Terrestrial Biomass Ocean Biomass Geothermal Heat Flux Hydropower Tides Exergy sources scaled to average consumption in 2004 (15 TW) From Hermann, 2006: Quantifying Global Exergy Resources, Energy 31 (2006)

8 Global Exergy Stores Exergy (ZJ) 0 Geothermal Energy* Deuterium tritium (from Li) Uranium Thorium Coal Gas Hydrates Oil Gas Yearly Human Consumption From Hermann, 2006: Quantifying Global Exergy Resources, Energy 31 (2006)

9 Global Exergy and Carbon Flows Source: W. Hermann, GCEP Systems Analysis Group

10 Global Carbon Flows from Energy Service Sectors of the Human Energy System (Mg C/s) Electricity Services, 105 Agriculture and Forestry, 190 Heating and Cooking, 52 1 MgC/s = 31.5 MtonneC/yr) Material Processing and Manufacturing, 153 Resource Production, 21 Transportation, 59 10

11 Global Carbon Emissions versus Process Exergy Destruction Log (Carbon Emissions (MgC/s)) Food Cooking Non Metallic Mineral Indoor Air Heating Processing Metabolism Petroleum Refining Manufacturing Metal Purification Electricity from Methane Food Processing Chemical Production Aircraft Chemical Production Liquid Fuel Electricity Shipping Water Heating Electricity from Solid Biofuel Charcoal Production Ethanol Production Pipeline Transport Solid Waste Conversion Lighting Natural Gas Processing Paper Prodduction Agriculture Electricity from Coal Forestry Road and Rail Oil and Gas Extraction Heating and Cooking Electricity Services Log (Process Exergy Destruction (TW)) Agriculture & Forestry Resource Production Transportation Materials Processing 11

12 Relative Fractions of Global Exergy Destruction and Carbon Flows Electricity - Coal 100% Electricity - Solid Biofuel Electricity - Methane Electricity - Liquid Fuel Electricity - Coal Water Heating 75% Food Processing Food Cooking Percent Contribution 50% 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 25% Coal Mining Natural Gas Processing Petroleum Refining Pipeline Transport Oil and Gas Extraction 0% Process Emissions (Gt-C/year) Exergy Destruction (TW) Shipping Aircraft Road and Rail 12

13 Global Exergy Destruction and Carbon Flow in the Electricity Sector Exergy Destruction Exergy Destroyed (TW) The The electricity sector is is dominated by by coal coal in in terms of of exergy destroyed and and carbon emissions. 0.0 Carbon Release to Atmosphere Process Exergy Efficiency Efficiency (%) 100% 50% Carbon Released (Mg C/s) 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 0% 0 13

14 Global Exergy Destruction in the Transportation Sector Exergy Destruction Process Exergy Efficiency % Exergy Destroyed (TW) Efficiency (%) 30% 20% 10% 0.0 Road and Rail Aircraft Shipping Pipeline 0% Road and Rail Aircraft Shipping Pipeline Road and and rail rail accounts for for largest destruction of of exergy in in the the global transportation system and and this this transformation occurs with with the the lowest efficiency 14

15 Global Carbon Flows in the Transportation Sector Carbon Release to Atmosphere Carbon Release per Exergy Destroyed Carbon Release per Exergy in Product Road and Rail Aircraft Shipping Pipeline Road and and rail rail also also accounts for for greatest CO CO 2 in the 2 releases in the transportation sector 15 Road and Rail Aircraft Shipping Pipeline C per Exergy in Product (Mg C/s per TW) Carbon Released (Mg C/s) C per Exergy Destroyed (Mg C/s per TW) Road and Rail Aircraft Shipping Pipeline

16 Global Exergy Destruction and Carbon Flows from Agriculture and Forestry Exergy Destruction Carbon Release to Atmosphere Exergy Destroyed (TW ) Carbon Released (Mg C/s) Agriculture Forestry 0 Agriculture Forestry Although not not deployed primarily for for energy production, agriculture and and forestry represent significant pathways for for exergy destruction within the the human exergy system 16

17 Global Exergy Destruction and Carbon Flows for Heating, Lighting, and Cooking Exergy Destruction Indoor Air Heating Water Heating Food Cooking Very Very low low conversion efficiencies 17 Indoor Air Heating Water Heating Food Cooking Lighting Process Exergy Efficiency 12% 8% 4% Carbon Release to Atmosphere 0% Lighting Carbon Released (Mg C/s) Exergy Destroyed (TW) Efficiency (%) Lighting Indoor Air Heating Water Heating Food Cooking

18 Future Analysis Maintain data data with with annual annual updates Deeper Deeper analysis of of exergy exergy destruction and and carbon carbon emissions, e.g.: e.g.: segmented segmented across across geographic geographic regions regions along along specific specific energy energy pathways pathways Define Define future future scenarios and and set set parameters for for technology pathways to to achieve them, them, e.g.; e.g.; sustainable sustainable transportation transportation system system sustainable sustainable electricity electricity delivery delivery system system Develop new new flow flow charts charts for: for: Other Other greenhouse greenhouse gases gases and and materials materials (CH (CH 4, 2 O, particulate matter, etc.) 4, N 2 O, particulate matter, etc.) Global Global warming warming potential potential Add Add time time component to to charts charts to to yield yield a picture picture of of the the level level of of sustainability of of global global energy energy use. use. Develop user user friendly friendly web web interface for for exergy exergy and and carbon carbon flow flow data. data. 18

19 Conclusions The The transition to to energy systems with with much lower GHG emissions is is one one of of the the grand challenges we we humans must face face in in this this century. Carbon is is currently being reintroduced to to the the biosphere through the the human use use of of fossil fuels at at a rate rate far far exceeding its its natural sequestration. Presented methodology for for quantifying and and linking together the the major flows of of exergy and and carbon at at a global level level Can Can identify the the energy conversions with with potential to to significantly impact the the relationship between human exergy use use and and CO CO 2 2 emissions. Data provide a framework for for analyses of of the the impacts of of various technological advances and and policy initiatives that that could enable or or encourage increased exergy efficiency or or new new energy pathways. 19

20 Acknowledgments Wes Hermann I-Chun Hsiao Ljuba Miljkovic A.J. Simon Emilie Hung Paolo Bosshard Jenny Milne Sally M. Benson Lynn Orr 20