Chevron and AC Transit in Comprehensive B20 Biodiesel and GTL Fuel Test
13 October 2007
Chevron and AC Transit, the transit operator for Alameda and Contra Costa counties in California (the San Francisco East Bay area), are conducting a test and evaluation of B20 biodiesel and synthetic GTL (Gas-to-Liquids) diesel. Cummins Engine and Cummins West are also participating in this test.
The statistically valid test will carefully monitor engine performance, emissions, fuel economy, vehicle handling characteristics (acceleration, smoothness of ride, and noise), and the impact of these fuels on lubricants and engine components. The proposed trial is to run for approximately six months, and constitutes one of the most comprehensive operational tests of alternative fuels yet, according to the AC Transit Board of Directors.
The B20 biodiesel is a blend of 80% ultra low-sulfur diesel (ULSD) and 20% soybean-based biodiesel. Chevron’s base fuel is its standard 15 parts per million CARB ULSD, which is comparable to the fuel used by AC Transit throughout its diesel fleet. The GTL fuel is produced by Sasol Chevron, a joint venture between Sasol of South Africa and Chevron.
The six-month test will use 60' articulated diesel buses with Cummins’ ISM 2006 engines deployed in regularly scheduled revenue service. The partners expect that in combination, the test buses will accumulate approximately 415,000 miles during the period, and consume approximately 160,000 gallons of fuel. A set of publicity buses will also circulate on various transbay routes.
Additional data collection and analysis of engine performance and emissions, as well as an assessment of engine wear and tear, will be conducted by Cummins Corporation, with the aid of the vehicle dynamometer at the Cummins West facility in San Leandro. Chevron also intends to survey operators periodically to assess vehicle driveability under the conditions of each fuel type.
Chevron is guaranteeing the quality of the fuel, and Cummins Engine is fully warranting AC Transit’s engines under the terms of this trial program.
Chevron and AC Transit have also worked together on an evaluation of hydrogen-fueled buses.
Resources:
AC Transit Board of Directors GM Memo No. 07-169
- AC Transit to test cleaner-burning fuels, Contra Costa Times 13 October 2007
GTL is around 30% worse in terms of CO2 than normal diesel....its a nightmare fuel, ban it please
Posted by: baldwincng | 13 October 2007 at 08:54 AM
@ baldwincng -
you're right, GTL isn't all that great in terms of well-to-wheels efficiency and hence, CO2 emissions. It does provide an option for bringing to market the portion of the world's natural gas that is too remote for pipelines. The alternative, LNG, cannot be used directly as a general transportation fuel. Instead, you have to let it boil off and compress it into CNG. The well-to-wheels CO2 emissions of that aren't all that great, either, because CNG has to be burnt in a spark ignition engine.
Where natural gas is abundant - Russia, Iran etc. - CNG vehicles ought to be the natural choice. Unfortunately, consumers in those countries can ill afford the expensive composite fuel tanks.
Note that a big piece of GTL production is the Fischer-Tropsch synthesis, which is common to all xTL fuels. A very useful side effect is that any sulfur in the feedstock is separated out in this exothermic step. If and when syngas from waste or dry biomass becomes available in large quantities at reasonable prices, the F-T expertise gained can be used for that. Perhaps the waste heat could be harnessed to dry moderately wet feedstock.
Until then, GTL is at least still better than CTL or OTL (oil sands to liquids).
Posted by: | 13 October 2007 at 10:41 AM
Solution:
Burn and LNG - diesel mix, diesel efficiency, natural gas straight from LNG into the engine (made back into gas of course!). Diesel efficiency but with 70% natural gas.
http://www.cleanairpower.com/
Around 40% better than GTL!!
Posted by: John Baldwin | 13 October 2007 at 12:49 PM
In Argentina I´ve seen 4 years ago long haul heavy trucks equiped with dualfuel (CNG-Diesel not LNG-diesel). For long trips these trucks have to carry a lot of dead-weight in heavy high-pressure steel tanks(charged at 200 Kg/cm2 aprox.2800 psi).
LNG could be a solution, but isolated tanks are very expensive and there´s the problem with high temperatures and the need to vent-off due to pressure rise.
Allthough GTL is not optimal is allways better than gas-flaring.
Posted by: Mario | 13 October 2007 at 04:49 PM
This is generally a win, I think, in most areas.
It's an experiment that should promote greater oil-independence, and cleaner-burning fuel in an urban environment.
For those of you worried about CO2, think of it this way: Increasing confidence in GTL fuels will probably increase confidence in BTL fuels, once they are truly implementable.
Posted by: tthoms | 13 October 2007 at 07:33 PM
You'd think the lightweight spun carbonfibre tanks developed for hydrogen could work for CNG, though I guess they are expensive. However I think XTL must increase as ethanol levels out. Not only GTL but BTL with perhaps a tad of coal within an overall cap provided the electrical grid moved to non-coal generation.
Posted by: Aussie | 13 October 2007 at 08:08 PM
Hmmn, They plan to travel 415,000 miles and consume 160,000 gallon of USLD diesel or B20 fuel. That means they anticipate getting 415/160 or 2.59 miles per gallon traveled.
The fleet average of all US cars (not including trucks) was just over 30.0 mpg in the most recent model year available, courtesy of a recent reference by jack.
That means the mean load factor for the bus fleet in metro San Francisco would have to have 11.56 passengers in it throughout its scheduled run; that is assuming that every car had exactly one driver and no others.
But that is not true. If that is true for only two thirds of the cars, and one third have two or more passengers than the bus load factor would would have to climb even higher. If that one third of vehicles for simplification, had had only one passenger beside the driver, (ignoring all vehicles with three or more people, that would drive it up even further), than the load factor would have to climb to 17.4 passengers per bus throughout its scheduled run. Yes for this simple calculation, it requires that number of passengers on the bus throughout its run beginning to end.
Not an empty bus gradually accumulating passengers perhapspeaking at just over 17 just before disgorging them at center city. Nor the obverse of a near full bus, gradually disgorging them until near empty at the end of its run in the suburbs. It is 17.4 or better at at all times, on average, to meet that load factor.
Now I'll concede that rush hour load factors may exceed that, but I'll bet that most bus runs during non rush hour don't have load factors anywhere near approaching 17.4 passengers per bus, through out the run, beginning to end. Most don't approach 11.56 even.
IOW, running mass transit is a waste of energy; never mind operating expenses for buses, drivers and capital expenses for buses, garages, repair shops, et cetera, except during rush hour.
Conventional wisdom is wrong once again. Save the world. We are told to Conserve Energy. To do so, I'd advise that it would save lots of energy to just park the buses and not run them except during rush hours.
That course of action may not be 'politically correct'; but it is also a realistic way to Conserve.
Posted by: | 14 October 2007 at 10:09 AM
Mass transit is immensely more efficient than individual automobiles with one person in each of them, no matter what way you cut it. Unless by "politically correct" you mean "what doesn't defy physics".
Posted by: Jim G. | 15 October 2007 at 08:42 AM
Really!
1 person, 1 25mpg car, 25 mile trip = 1 gallon per person used for the trip.
7 people, 1 3mpg bus, 25 mile trip = 1.19 gallons per person used for the trip.
Look I just defied physics. Please people, think before you post.
Posted by: Joseph | 16 October 2007 at 09:06 AM
In the hilly terrain of San Francisco 3 mpg for a transit bus makes sense. In a flatter environment mileage was closer to 7-8 mpg. As a retired bus driver I know from experience that many routes only have a few passengers each during off peak periods. But during peak periods it was not uncommon to have 30-40+ passengers. Also a 25 mile round trip was a rare event with the average closer to 6 miles. I did have many passengers who drove 25 miles to the end of the route and then ride downtown in order to avoid parking costs.
Posted by: tom deplume | 16 October 2007 at 11:25 AM
Does anyone have current experience with CNG diesel hybrid or LNG diesel hybrid? Is there any value to retrofitting existing Diesel? What's the up and down sides? (Is this a dead conversation, I don't find current information.) I understand propane is not only a POWER enhancer rather, than a price reducer.
Any retro to existing Diesel Engines viable with any alternative fuel, beside the straight bio-diesel replacement?
Posted by: Paul | 03 June 2008 at 09:43 AM