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Problems with the proposed CAFE Standards for 2020

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Problems with the proposed CAFE Standards for 2020

Dennis Silverman

Physics and Astronomy

UC Irvine

- The Senate bill on the new CAFE standards for 2020 mandates a fleet average of 35 miles per gallon (mpg) which includes both cars and small trucks (SUVs, trucks and vans).
- We will show here problems with the single fleet average in actually being able to increase the mpgs of small trucks.

- Some of the present hybrids are even now achieving 50 mpg ratings (Toyota Prius and Honda Accord hybrids).
- For each of those types made by an American automaker, they can preserve the total fleet average by making a 20 mpg SUV or small truck, since ½(50+20)=35 mpg.
- This SUV allowance is even lower than the present 21.5 mpg group average for small trucks.
- One way around this problem is to exclude plug-in hybrids and electric cars from the average.

- Plug-in hybrids are projected to run 40 miles on pure battery power from the charge they acquire from utilities.
- In terms of greenhouse gases, utilities produce the electrical energy more efficiently than the internal combustion engines of present hybrids.
- Priuses that are outfitted as plug-in hybrids are said to obtain 70-75 mpg equivalent.
- Plug-in hybrids are estimated to exceed 100 mpg based on greenhouse gas emissions from utilities, while under the 40 mile all electric range.
- If the electricity is generated by nuclear, hydro, solar or wind power, than the greenhouse gas emissions are essentially negligible, and the effective mpg are well over 100 mpg.
- Because of this, it is hard to provide a single effective mpg for these vehicles. A national average based on the average greenhouse gases for the nation’s electricity supply could be used.

- I haven’t found an explication of how the NHSTA will decide on mpg ratings for plug-ins.
- Present tests are based on something like the first 12 minutes of driving, or the first 12 miles of a drive.
- Since those ranges are covered by the electric charge, even natural gas powered utilities should give and effective mpg of 100 mpg.
- We assume this is included as the vehicle rating, until otherwise specified.
- The average American commute is under 30 minutes or miles. If recharged at work, the electric nature of the plug-in could completely cover a day’s driving.

- We use an example where each plug-in hybrid produced in America is rate as 100 mpg.
- Using the single fleet average, such a hybrid is 65 mpg over the average.
- The average can then be balanced say by three SUVs or small trucks that get
(35 - 1/3(65)) = 35 – 22 = 13 mpg.

- By the time 2020 arrives, and without a wise rating or averaging policy by EPA, each environmentally minded citizen will know that his or her buying a super-efficient plug-in hybrid will be nullified by three purchasers of highly inefficient Hummer type SUVs or giant “small” trucks.
- This inequity should be fixed before the CAFE bill is passed by the full Congress.
- We discuss such fixes in the following slides.

- It is better if SUVs and small trucks have their own average, whatever it is.
- Detroit has proposed a 35 mpg average for cars and a 30 mpg average for SUVs and small trucks. That should be a more safeguarded small truck average that is a real requirement on them.
- However, among the cars, the same unenvironmental countering of plug-in hybrids might occur with cars that are no more efficient than those that get the current 27.5 mpg average.

- Most cars in America drive an average of 15,000 miles per year.
- The gas that is consumed by a car or small truck is given by
fuel = miles driven x (gallons/mile)

- This contains the reciprocal of the miles/gallon ratio currently used.
- For simplicity, let us take this measure of fuel used in a 100 mile trip, and call it the CAFE Fuel Standard
- Then the sample plug-in hybrid at 100 mpg will give a fuel standard of unity:
fuel = 100 miles / (100 mpg) = 1

- The typical vehicle at 35 mpg under the new fuel standard will be rated as
fuel standard = 100 / 35 = 2.86 or approximately 3. (Environmentally it is 3 times as greenhouse gas polluting as the best car available, the plug-in hybrid.)

- This would be the new fuel standard average for a 100 mile trip that Congress or the states could adopt.

- The example had a 100 mpg plug-in hybrid balanced by three 13 mpg SUVs under the 35 mpg average.
- Applying the fuel standard (fs), the 13 mpg SUV will have fs = 100 / 13 = 7.7.
- Under a fuel standard average, the four vehicles above would average
¼ (1 + 3 x (7.7)) = ¼ ( 24.1) = 6.0

not 3.0.

- Take m as the mpg of the gas vehicle.
- For one gas vehicle to balance one plug-in giving an average fuel standard of 3
fs = ½(1+100/m) = 3 implies m = 20 mpg.

- For two gas vehicles balancing one plug-in
fs = 1/3(1+2x100/m) = 3 ; m = 25.

- For three gas vehicles against one plug-in
fs = ¼(1+3x100/m) = 3 ; m = 27 mpg.

- For four gas vehicles balancing one plug-in
fs = 1/5(1+4x100/m) = 3 ; m = 29 mpg.

- From the previous slide, if 20% of the fleet are plug-ins, they are balanced 4 to 1, and the average requirement on gas vehicles is 29 mpg.
- If 25% of the fleet are plug-ins, the average requirement on the gas vehicles is 27 mpg, comparable to the present mpg average on cars.
- The above 3 gas to one plug-in balancing case used in the example with the present mpg averaging method only required gas vehicles to have a 13 mpg average.
- So we conclude that the fuel usage standard comes close to what the Congress intends to occur with enhanced CAFÉ standards.