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DFE World: Design & the Global Environment
Photograph of Nature
Air Pollution








1.  a.)  Using the Vehicle Design Module, determine the annual fuel cost for the current Saturn SL1 model with an automatic transmission.  Next, look at the cost of the same vehicle with an ultra-lightweight chassis that reduces the overall vehicle weight by 500 lbs.   If using these new materials added $400 to the cost of the vehicle, how long would it take (assuming an avg driving cycle of 15,000 miles per year) before the consumer gained a financial benefit from purchasing the lighter vehicle?


b.)  At the point in time when the consumer with the lighter Saturn “breaks even” on the vehicle purchase (solution to 1a), how many gallons of gas has he or she conserved relative to the original Saturn configuration?


2.  Go to The National Weather Service forecast page for Ann Arbor to get the current weather conditions.  Determine surface wind speed (m/s), wind direction (degrees, clockwise from North = 0), and stability class (see determination criteria).  Assume a mixing height of 100 meters.  Assume a fleet of vehicles utilizing a manual transmission, CD = 0.385, and vehicle weight of 2625 lbs.  Manually calculate the concentration of carbon monoxide at the Michigan Union due to the U of M Power Plant and vehicles traveling down State Street.  (Assume an ambient CO concentration of 3 ppm).

Power Plant Assumptions:

Location (x(m), y(m))

Effective Stack Height (m)

Wind Speed at Stack Height (m/s)

(911, 1192)



To determine the emission factor of the coal-fired power plant, assume the plant generally emits 0.5 lbs of CO per ton of coal burned.  The heating value of coal is 26 million Btu/ton of coal burned.  Finally, assume the plant capacity is 1 mega-watt, and that the plant is 25% efficient.

The concentrations determined from the Gaussian line source and point source equations for the receptor of interest are additive.

3.  a.)  Assume Ann Arbor's vehicle fleet is composed entirely of fuel cell vehicles (with CD = 0.285 and vehicle weight = 2125 lbs).  This will require a power plant to reform H2 and could have implications that could potentially offset the pollution savings from these low emission vehicles.  A coal-fired power plant will be constructed in the location of the Frieze Building (once it is torn down).  Assume that the same meteorological conditions hold that you determined in part 2.  Now include the H2  reforming power plant with the following parameters:

Location (x(m), y(m))

Effective Stack Height (m)

Wind Speed at Stack Height (m/s)

(508, 1206)



To determine the capacity of this plant, assume that hydrogen cars require 0.35 kW-h/mi.  Assume there are an average of 300 vehicles on the road at any given time.  Assume that all vehicles are traveling on average at 35 mph.  To determine the emission factor of the coal-fired power plant, assume the plant generally emits 0.5 lbs of CO per ton of coal burned.  The heating value of coal is 26 million Btu/ton of coal burned.

Calculate the concentration of CO at three different receptors (of your choice) due to the contribution from vehicles traveling down three different roads (of your choice), due to the hydrogen reforming power plant and due to the U of M power plant.   These three terms are additive.  Display your results in an excel worksheet in a layered bar graph showing the respective contributions (however, you will only have three columns presented in your graph).


b.)  How do your observed pollutant concentrations compare to the National Ambient Air Quality Standards for CO?

4.  A manufacturer’s CAFE is the fleet wide average fuel economy. The averaging method used is referred to as a “harmonic mean”. The regulatory language describes the calculation as: “the number of passenger automobiles manufactured by the manufacturer in a model year; divided by the sum of the fractions obtained by dividing the number of passenger automobiles of each model manufactured by the manufacturer in that model year by the fuel economy measured for that model.”



Production Volume

Vehicle A



Vehicle B



Vehicle C



New Saturn




a.)  Calculate the average fuel economy ratings for the manufacturer’s fleet of vehicles assuming only vehicles A, B, and C are produced.


b.)  The CAFE standards are applied on a fleet-wide basis for each manufacturer; i.e., the fuel economy ratings for a manufacturer's entire line of passenger cars must average at least 27.5 mpg for the manufacturer to comply with the standard. [If a manufacturer does not meet the standard, it is liable for a civil penalty of $5.00 for each 0.1 mpg its fleet falls below the standard, multiplied by the number of vehicles it produces. For example, if a manufacturer produces 2 million cars in a particular model year, and its CAFE falls 0.5 mpg below the standard, it would be liable for a civil penalty of $50 million.]  Using your answer in part (a), determine what (if any) penalty the manufacturer faces in this scenario.


c.)  The company has decided that they will comply with CAFE standards by any means necessary.  One solution involves creating a new Saturn vehicle that will help the company achieve the 27.5 mpg CAFE standards.  Using the Vehicle Design Module determine X and Z (in the table above) for each powertrain option assuming that the sleek, low drag bodystyle will be chosen with a vehicle weight of 2625 lbs.


d.)  In a paragraph or less, discuss environmental concerns associated with the alternative powertrains.

5. Discuss assumptions and uncertainty in the vehicle design aspects and the pollution modeling aspects of this module.  How will one error propagate to further amplify uncertainty?