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Old 05-24-2011, 03:03 AM   #1 (permalink)
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Gas/hybrid buses get lower mileage than diesel

This is from 3 years ago:

Long Beach Transit: Two-Year Evaluation of Gasoline-Electric Hybrid Transit Buses

Long Beach study shows gas/hybrid buses get lower mileage than diesel - AutoBlogGreen

Study Finds Fuel Economy of Gasoline-Electric Hybrid Buses Lower Than That of Conventional Diesel - Green Car Congress

In the meantime, Volvo introduced a diesel/hybrid bus, which is claimed to reduce fuel consumption by up to 30%. Of course, diesel-hybrid technology is more expensive than gas-hybrid or straight diesel, but allows not only lower fuel consumption, but also lower CO2, NOx and soot emissions, which is just as important in an urban environment.

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Old 05-24-2011, 05:07 AM   #2 (permalink)
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Are they accounting for the greater energy content of the diesel fuel?

Electric buses with overhead power lines are far more efficient than diesel.
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Old 05-24-2011, 09:34 AM   #3 (permalink)
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I am surprised they even made gasoline-electric. Really would have guess they were diesle-electric or even CNG-electric.
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Old 05-24-2011, 11:37 AM   #4 (permalink)
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Quote:
Originally Posted by Piwoslaw View Post
Of course, diesel-hybrid technology is more expensive than gas-hybrid...
Why of course? I'd think it'd be just the opposite: bolt the same hybrid parts to a gas engine or a diesel engine, same cost either way.
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Old 05-24-2011, 12:00 PM   #5 (permalink)
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Diesel engines cost more. Still, from a fleet maintenance standpoint, I still would have expected diesel-electric.
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Old 05-24-2011, 12:35 PM   #6 (permalink)
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Its not that the diesel hybrid parts cost more, just the diesel parts. This, in turn, makes the cumulative costs go up.

It was just an irresponsible way to word it, which makes it seem like the better candidate is unbearably expensive.
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Old 05-24-2011, 06:03 PM   #7 (permalink)
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Quote:
Originally Posted by NeilBlanchard View Post
Are they accounting for the greater energy content of the diesel fuel?
Yes ... but it changes the results to the opposite of the original poster's title ... in all 3 posted links the Hybrids are more energy efficient ... see bellow:

In this referenced paper it states:

Quote:
On a volumetric basis, the 24-month average fuel economy for the hybrid buses is 3.35 miles per gallon (mpg)—4.3% lower than that of the diesel buses. This difference is likely due to the lower efficiency of a throttled, spark-ignited engine as well as the lower energy content of a gallon of gasoline versus a gallon of diesel. On an equivalent energy per volume basis, the hybrids had an 8.5% mpg increase.
It goes on to compare based on fuel costs ...

Quote:
During the evaluation period, gasoline at LBT cost an average of $2.49 per gallon and diesel cost an average of $2.29 per gallon. This lower fuel economy, combined with a higher fuel cost for gasoline, resulted in fuel costs per mile being $.74 per mile for the hybrids as compared to $.65 per mile for the diesels.
The Diesel fuel was cheaper per gallon by enough of a margin to keep it cheaper to fuel per mile.

But it goes on to also look at the maintenance costs of the two:

Quote:
The hybrids cost $.31 per mile to maintain while the diesels cost $.54 per mile.
Quote:
The hybrids had brake system maintenance costs that were about 90% less than that of the diesel buses with no relines to date on the hybrids.
The diesel fuel per mile saving are not large enough to compensate for the higher costs to maintain them... although the diesels were older buses ... The hybrids were newer ... a better comparison would have been between two groups of hybrid and diesels that were equally old / used.

- - - - - - -

In this has the same findings and states:

Quote:
NREL looked at the performance of the buses and found that the gas hybrids got 4.3 percent lower fuel efficiency than the conventional diesel buses in the fleet. When the lower energy content of gasoline is factored in, though, the gas hybrid came out 8.5 percent better.
- - - - - - - - - -

Also seems to have the same findings:

Quote:
found that on a volumetric basis, the average fuel economy for the gasoline hybrid buses is 3.35 mpg—4.3% lower than that of the conventionally-powered diesel buses
Quote:
On an equivalent energy per volume basis, the hybrids had an 8.5% mpg increase.
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Old 07-28-2015, 10:35 AM   #8 (permalink)
It's all about Diesel
 
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Gaseous fuels such as CNG or biomethane make more sense for an urban transit bus than gasoline.
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Old 07-29-2015, 05:30 PM   #9 (permalink)
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Quote:
Originally Posted by cRiPpLe_rOoStEr View Post
Gaseous fuels such as CNG or biomethane make more sense for an urban transit bus than gasoline.
Agreed! Urban transit vehicles (a) seldom drive away from home routes to far-away places and (b) always return home to their maintenance depot each night...making "refueling" from a SINGLE location a strong point.
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Old 07-30-2015, 09:55 PM   #10 (permalink)
It's all about Diesel
 
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I usually point biomethane as a possibility to increase the availability of gaseous fuels in the countryside, since it's renewable, can increase the income of farmers and has a lesser impact in the availability of arable land for food and industrial feedstocks compared to ethanol. Then, not just for urban transit, it could also become a viable option for longer intercity routes.

Actually, in some intercity routes in my state, a CNG-powered bus would already make sense, and eventually a hybrid driveline would be interesting to reduce the fuel usage while stopping in certain locations where CNG is still not so easily available.

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