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Reducing the Global Warming Impact of the Passenger Vehicle Fleet Harriet Gu Jason Martz Sara Soderstrom Global Warming Reduction via Greening the Automotive Powertrain Objective:

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reducing the global warming impact of the passenger vehicle fleet

Reducing the Global Warming Impact of the Passenger Vehicle Fleet

Harriet Gu

Jason Martz

Sara Soderstrom

global warming reduction via greening the automotive powertrain
Global Warming Reduction via Greening the Automotive Powertrain


To evaluate the impact of passenger vehicles on the feasibility of achieving the Kyoto Protocol standards for CO2 emission reductions

  • Engineering Design
    • Relate fuel efficiency to carbon dioxide production
  • Policy Development
    • Relate fleet composition to total carbon dioxide production
global warming
Global Warming

Figure from

radiative forcings
Radiative Forcings

Data from ME 599 coursenotes

u s greenhouse gas emissions
U.S. Greenhouse Gas Emissions

Figure from

kyoto protocol
Kyoto Protocol
  • Agreement negotiated among 160 industrialized nations
  • Establishes binding greenhouse gas emission reductions
  • Target achievement between 2008 and 2012
  • United States
    • 7% below 1990 emissions
    • Currently 10% above 1990 levels!
    • Under current growth  33% greater than 1990 levels
challenges to kyoto protocol
Challenges to Kyoto Protocol
  • Can targets be met?
    • American Council for Energy-Efficiency Economy
      • Proactive sector involvement
      • Increased R&D efforts
      • Strengthened state programs and policies
      • Focused effort to develop and transform markets for low-carbon energy options
    • American Society of Mechanical Engineers
  • Can sinks (trees, agriculture, etc.) be counted?
    • Reduces U.S. emission decreases to 3-4% below 1990 levels
  • Can tradeable permits be used?
transportation fleet
Transportation Fleet
  • 18% of CO2 emissions are from cars, SUVs, and passenger trucks
  • 201 million vehicles in 1997
  • 1.1% vehicle growth/year
  • 64% automobiles, 36% SUVs & trucks
  • CAFE automobile standards = 24 mpg
transportation ownership and usage
Transportation Ownership and Usage
  • 18.5% of household expenses for transportation (1997)
  • 17.3% of households have 3 or more vehicles (1990)
  • Average travel per vehicle per year = 11,800 miles
  • Average occupancy
    • Automobile 1.6 persons
    • Pickup Truck 1.4 persons
    • SUV 1.7 persons
    • Van 2.1 persons
  • 13.4% of workers carpool (1990)
current us passenger car configuration
Current US Passenger Car Configuration
  • Engines oversized for performance
    • Allow for high accelerations, but …
    • These performance requirements are not required for the majority of the vehicle operation
  • Large vehicle mass
    • Requires larger engine sizes to maintain performance
  • Non-optimal vehicle drag coefficients
    • Vehicle experiences higher drag forces at a given speed
  • High tire rolling resistance
    • Rolling losses due to friction in the tire as it flattens to conform to the road
  • Overall Effect: High vehicle fuel consumption
what does this mean
What Does This Mean?
  • Lower fuel economy means more fuel is consumed to perform a desired task
  • An increase in fuel consumption results in an increase CO2 production
  • Fortunately, organized research is being conducted in order to increase vehicle fuel economy
  • PNGV: Partnership for a New Generation of Vehicles
  • Collaboration between the Federal Gov’t and the Big Three
  • Goal is for each company to produce an 80 mpg family sized sedan concept vehicle by 2004, that has performance, safety and cost characteristics similar to today’s family sedans
pngv goals
PNGV Goals
  • Obtain 80 mpg goal by integrating the following concepts into the auto:
    • Efficient fuel converters, such as fuel cells, turbocharged direct injection diesels, hybrids
    • Better sizing of powertrain components
    • Lighterweight components
    • Bodies with lower drag coefficients
    • Tires with lower rolling resistances
    • Effect: Higher fuel economy
study data goals
Study Data Goals
  • Isolate the effects that powertrain components have on vehicle fuel economy
  • Base study on components and fuels that are available in the near future
  • Model the components in a PNGV type vehicle
  • Maintain constant body and tire characteristics throughout the study, except for baseline vehicle case, which is representative of a contemporary passenger vehicle
  • Study accomplished using Advisor, which allowed for easy substitution of powertrain components within a given vehicle configuration
  • Forward/Backward vehicle simulation developed by NREL
  • Available as freeware at
  • Capable of modeling conventional, fuel cell, electric, and hybrid electric vehicles of all types
  • Allows designers and policy makers to search for an optimal combination of powertrain components, or to simulate existing powertrain components for a given design objective
  • Not an engineering design tool for individual components
simulated powertrain component characteristics
Simulated Powertrain Component Characteristics
  • Spark Ignition Engines
    • Low compression ratios, throttle intake manifold for load control
    • Low thermal efficiencies compared to diesel engines.
  • Diesel Engines
    • High compression ratios, vary equivalence ratio for load control, no throttling
    • More efficient than Spark Ignition
    • Turbocharged
    • NOx and particulate emissions are relatively high
Fuel Cell
    • Uses a fuel reformer to produce H2 from hydrocarbon based fuels
    • Relatively high thermal efficiency at mid and high loads
    • Output energy from the fuel cell is stored in a battery, so the fuel cell can be used in its efficient load regimes
    • Battery powers a DC motor
  • EV1
    • Electric vehicle
    • Stores energy obtained from the electric grid in batteries, limited range
    • Batteries power an electric motor
    • No vehicle emissions, but emissions from powerplant that produced the electricity for the vehicle
Honda Insight
    • Hybrid electric vehicle: Starter/Alternator type
    • Uses a motor/generator in combination with an IC engine. Motor generator used to load the engine to its efficient operating regime, or to suppliment the engine under high load conditions
    • Smaller IC engines can be used as a result of the motor
    • Energy for the motor is stored in batteries
    • Engine cannot be disconnected from the motor gearbox, so both are always turning
GM Precept
    • Parallel hybrid electric vehicle
    • Similar to the Starter/Alternator HEV, except that the engine can be decoupled from the motor/generator
    • Parallel 50 input is a slightly more hybridized parallel vehicle
  • Toyota Prius
    • Similar to Parallel hybrid, except that the vehicle uses a CVT transmission, and has a separate generator and motor
  • SUV
    • Sports Utility Vehicle used to model trucks later in the project, as a performance comparison to cars
backward facing simulation
Backward Facing Simulation
  • Assumes vehicle will meet a given speed trace without violating the performance constraint inputs
  • Advisor contains two different optimization routines for the selection of optimal component configurations
  • PNGV Performance Constraints were used for the comparison of vehicles in the performance study
  • Powertrain components are sized according to the given optimization objective and its constraints
  • The MatLab based bisection optimization routine for minimizing component capacity (power) requirements was used, when necessary for this study
  • Component performance data is contained in a series of lookup tables
Performance data was obtained from steady state tests, conducted by private and public sources
  • Component capacity is linearly scaled by the optimization routine to find an optimal solution
  • This feature allows for the integration of optimally sized components, whose characteristics are based on one original parent component
  • Components that were already close to the PNGV configuration were not optimized
  • The performance of the vehicles was verified to be close to the PNGV vehicles, by running the vehicle through a single load step that outputs vehicle performance, which can be checked against PNGV constraints, in the Simulation Results Screen
forward facing simulation
Forward Facing Simulation
  • Once the size of the powertrain components has been determined, the vehicle is run through a drive cycle to determine fuel economy and emissions
  • Drive Cycles:
    • Combined City/Highway
    • SAE J1711 (for hybrid electric vehicles)
fuel economy co 2 production
Fuel Economy  CO2 Production

Note: For electric vehicle, fuel efficieny is multiplied by 0.32, the efficiency of the electrical distribution grid.

fleet characterization
Fleet Characterization
  • Predicted miles traveled by automobiles in 2012
  • Determination of 1990 CO2 production by automobiles
policy requirements
Policy Requirements
  • Increase CAFE standards
    • Automobiles  ~57 mpgge
    • Trucks  ~48 mpgge
  • New standards effective 2009
policy feasibility
Policy Feasibility
  • Knowledge/understanding of consequences of global warming
    • Political and corporate acceptance
    • Public awareness and consumer acceptance
  • Oil/gasoline availability and cost
  • Cost of new technology
  • Similar vehicle performance
model uncertainties and weaknesses
Model Uncertainties and Weaknesses
  • Advisor
    • Use of available components in simulations
      • Use of “real” data
      • Data for most recent technology is not available
    • Emission predictions are qualitative at best
    • Optimization routine linearly scaled components
      • Heat transfer, friction don’t scale linearly!
    • Based on steady-state data, not on dynamic performance
  • Fleet characterization
    • Automotive, SUV, and truck growth and use rates assumed constant
    • Vehicle age distribution assumed constant
future considerations
Future Considerations
  • Cost/benefit analysis for automotive changes versus energy consumer changes
  • Effects of economic incentives for carpooling and mass transportation usage
  • Cost analysis for mass transportation development and improvements
    • Mass transport currently takes 2x’s longer!
  • Cost/effect of future technology
  • Kyoto Protocol is a good guideline for initially decreasing CO2 emissions
  • Advisor is a useful tool for designers and policy-makers to explore future vehicle designs
  • Model predictions
    • Improved vehicle technology can lead to achievement of Kyoto Protocol standards
  • Policy incentives are needed
    • CAFE standards: autos  57 mpgge, trucks  48 mpgge
  • Multiple political, consumer, and technological issues will also affect implementation