WelltoWheels Analysis of VehicleFuel Systems

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Well-to-Wheels Analysis of Vehicle/Fuel Systems

• Michael Wang
• Center for Transportation Research
• Argonne National Laboratory
• Workshop on Modeling The Oil Transition
• Washington, DC, April 20-21, 2006

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Well-to-Wheels Analysis of Vehicle/Fuel Systems
Covers Activities for Fuel Production and Vehicle
Use
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WTW Analysis for Vehicle/Fuel Systems Has Been
Evolved in the Past 20 Years

• Historically, evaluation of vehicle/fuel systems
  from wells to wheels (WTW) was called fuel-cycle
  analysis
• Pioneer transportation WTW analyses began in
  1980s
• Early studies were motivated primarily by
  battery-powered EVs
• Recent studies are motivated primarily by
  introduction of new fuels
• Transportation WTW analyses have taken two
  general approaches
• Life-cycle analysis of consumer products
• Transportation fuel-cycle analysis
• Most transportation studies have followed the
  fuel-cycle analysis approach
• For transportation technologies, especially
  internal combustion engine technologies, the
  significant energy and emissions effects occur in
  
• The fuel usage stage
• The fuel production stage

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The GREET (Greenhouse gases, Regulated Emissions,
and Energy use in Transportation) Model Includes
Energy and Emissions

• Since 1995, DOE has been supporting GREET model
  development at Argonne
• The GREET model
• Includes emissions of greenhouse gases
• CO2, CH4, and N2O
• VOC, CO, and NOx as optional GHGs
• Estimates emissions of five criteria pollutants
• Total and urban separately
• VOC, CO, NOx, SOx, and PM10
• Separates energy use into
• All energy sources
• Fossil fuels (petroleum, natural gas, and coal)
• Petroleum
• The GREET model and its documents are available
  at Argonnes GREET website at http//www.greet.anl
  .gov
• The new GREET version 1.7, together with its user
  manual, was released in November 2005

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GREET Includes More Than 90 Fuel Production
Pathways from Various Energy Feedstocks
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Petroleum Refining Is the Key Energy Conversion
Step for Gasoline and Diesel
WTP Efficiency (US) Gasoline 80 Diesel
82
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Key Issues for WTW Analysis of Petroleum Fuels

• Recovery and refining of unconventional crudes
  are more energy and emission intensive
• Canadian oil sands
• Venezuelan heavy, sour crude
• US shale oil
• Better quality for fuel products is demanded in
  the U.S.
• Gasoline sulfur content of 30 ppm or less
• On-road diesel sulfur content of 15 ppm or less
• Ethanol is replacing MTBE as a gasoline additive
• Energy and emission differences between ethanol
  and MTBE
• Production of gasoline blend stock for ethanol
  vs. MTBE
• LP simulations of petroleum refining indicate
  that lowered sulfur contents in gasoline and
  diesel have minimal effects on energy and
  emissions
• But, use of unconventional crudes could
  significantly deteriorate energy and emissions of
  gasoline and diesel

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WTP GHG Results Show That Oil Sands Operations
Are Carbon-Intensive
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Production and Compression Are Key Steps for
Gaseous H2 Production
G.H2 gaseous H2 LNG liquefied natural gas NA
North American nNA non-North American NG
natural gas
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Resource and Infrastructure IssuesResult in Many
Potential H2 Pathways

• Key stages affect H2 WTW results
• H2 production
• H2 compression for gaseous H2
• H2 liquefaction for liquid H2
• Produced from natural gas via steam methane
  reforming (SMR) now, and in the foreseeable
  future
• Over 90 H2 is currently produced in this way
  worldwide
• Carbon emissions from H2 production plants
• Central or station SMR production
• Could reduce or avoid expensive distribution
  infrastructure
• But production emissions move close to urban
  areas
• Some amount of central SMR CO2 emissions can be
  potentially sequestered
• Energy and emission effects of electrolysis H2
  depend on electricity sources
• Fossil fuel-based electricity has huge amount of
  CO2 emissions for H2 production
• Renewable electricity, such as hydro, wind, and
  solar, has zero CO2 emissions
• Gasification for H2 production
• Coal CO2 and criteria pollutant emissions, but
  CO2 can be potentially sequestered
• Biomass criteria pollutant emissions
• Nuclear H2 has zero air emissions, but nuclear
  waste will continue to be an issue

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Ethanol WTP Pathways Include Activities from
Fertilizer to Ethanol at Stations
Agro-Chemical Production
Agro-Chemical Transport
Corn Farming
Woody Biomass Farming
Herbaceous Biomass Farming
Corn Transport
Woody Biomass Transport
Herbaceous Biomass Transport
Ethanol Production
Electricity (Cellulosic Ethanol)
Animal Feed (Corn Ethanol)
Transport, Storage, and Distribution of Ethanol
U.S. WTP Efficiency Corn-based EtOH 60
Cellulosic EtOH 41
Refueling Stations
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Key Issues for WTW Analysis of Bio-Ethanol

• Key stages affecting WTW GHG results
• Use of fertilizer in farms
• Nitrogen fertilizer
• Lime
• Energy use for farming
• Energy use of ethanol production
• Co-products
• Animal feeds for corn ethanol
• Electricity for cellulosic ethanol
• The debate on energy balance (energy in ethanol
  minus fossil energy used) is NOT meaningful, even
  though most studies concluded positive balance
  for corn ethanol
• Supply of corn ethanol may be limited relative to
  the U.S. transportation fuels market
• In 2005, of the 11.1 billion bushels of corn
  produced, 13 was used for producing ethanol
• In 2005, 4.2 billion gallons of ethanol was used,
  equivalent to 2.8 billion gallon of gasoline
• In 2004, the U.S. consumed 141 billion gallons of
  gasoline and 37 billion gallons of on-road diesel

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Most of the Recent Corn EtOH Studies Show a
Positive Net Energy Balance
Energy balance here is defined as Btu content a
gallon of ethanol minus fossil energy used to
produce a gallon of ethanol
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GREET Includes A Variety of Vehicle and Fuel
Combinations
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Key Assumptions Affecting WTW Results

• WTP assumptions
• Energy efficiencies of fuel production activities
• GHG emissions of fuel production activities
• Emission factors of fuel combustion technologies
• PTW assumptions
• Fuel economy of vehicle technologies
• Tailpipe emissions of vehicle technologies
• Large uncertainties exist in key assumptions
• GREET is designed to conduct stochastic
  simulations
• Distribution functions are developed for key
  assumptions in GREET

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GREET Can Conduct Stochastic Simulations to
Address Uncertainties
Distribution-Based Inputs Generate
Distribution-Based Outputs
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GREET Relies on A Variety of Data Sources
Well-to-Pump Data Sources

• Open literature
• Engineering analysis (such as ASPEN simulations
  for mass and energy balance)
• Stakeholder inputs (collaboration with the energy
  industry)
• The DOE H2A effort for H2 FCV WTW analysis

Well-to-Pump Data Sources

• Fuel economy
• Open literature
• Vehicle simulation with models such as the PSAT
  model
• Tailpipe emissions
• Open literature
• Emission testing results
• EPA MOBILE model
• CARB EMFAC model

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The PSAT Model Was Used to Estimate Fuel Economy
for a 2010 Model-Year Midsize Car
Values in RED are FreedomCAR 2010 Goals.
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Fuel Economy Values of a 2010 Model-Year Midsize
Car from PSAT Simulations
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GREET Takes These Steps to Estimate Vehicular
Emissions

• Emissions of VOC, CO, NOx, CH4, and PM10
• Vehicle technologies are simulated with EPAs
  MOBILE6.2 and CARB EMFAC by assuming their
  meeting of given tailpipe standards
• SOx emissions for each vehicle type are
  calculated from sulfur contained in fuels
• CO2 emissions for each vehicle type are estimated
  from carbon balance
• N2O emissions are based on limited testing
  results CARB and EPA effort on vehicular N2O
  emission testing will greatly reduce tailpipe N2O
  uncertainties

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2010 Model-Year Vehicles Are Assumed to Meet
Stringent Tier 2 Emission Standards Tier 2
Standards (Fully in Effect in 2009, g/mi. for
120K miles)
Assumptions for this analysis Bin 3 for
Gasoline cars Bin 2 for gasoline hybrids
Bin 4 for diesel cars Bin 3 for diesel hybrids
Bin 1 for H2 fuel-cell vehicles
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H2 FCVs with Ethanol or Conventional Electricity
May Increase WTW Total Energy, But
ICE and Hybrid
FCV
FC Hybrid
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Since H2 Is Produced from Non-Petroleum Sources,
H2 FCVs Almost Eliminate Petroleum Use
ICE and Hybrid
FCV
FC Hybrid
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Except for Average Electricity Options, H2 FCVs
Achieve Large GHG Reductions
FC Hybrid
FCV
ICE and Hybrid
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H2 FCVs With Ethanol and Average Electricity
Could Increase Total NOx Emissions, But
FCV
FC Hybrid
ICE and Hybrid
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H2 FCVs With NG, Ethanol, and Renewable
Electricity Reduce Urban NOx Emissions
FC Hybrid
ICE and Hybrid
FCV
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On the Basis of Fuel Cycle and Vehicle Cycle,
Advanced Vehicle Technologies Reduce GHG Emissions
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Outstanding WTW Analysis Issues

• Baseline crude for gasoline and diesel production
• Conventional crude vs. unconventional crude
• How to account petroleum Btus in petroleum use
  calculations?
• Technology advancement over time need to be
  considered
• Vehicle technologies for fuel economy and
  emissions
• Fuel requirements and production technologies
• Transparency should be emphasized in WTW analysis
  and results
• System boundary issues will continue to be
  debated
• WTW analysis includes operation-related
  activities, but usually does not include
  infrastructure-related activities such as
  building of petroleum refineries
• Definition of the boundary for a fuel is a moving
  target
• It is critical to maintain a consistent boundary
  for all fuels
• Absolute values vs. relative changes among
  vehicle/fuel systems relative changes are more
  reliable
• No silver-bullet fuel exists to solve all
  problems, trade-offs among impacts are more
  realistic
• Energy security
• GHG emissions
• Urban air pollution