DaimlerChrysler hybrid buses outperform CNG and diesel buses in New York City
The National Renewable Energy Laboratory (NREL), which is part of the US Department of Energy, has been monitoring the performance of three types of buses in New York City for the past year and now has some results to share. They looked at buses powered by conventional diesel drive-trains, compressed natural gas and diesel-hybrids built by DaimlerChrysler. The hybrid buses won out by a huge margin. They had 34 percent better fuel efficiency than the diesels and 60-120 percent better than the CNG buses. The average maintenance cost of the hybrid buses was also 5 percent less than the CNG buses.
The Orion VII buses used a series hybrid design where the diesel engine basically powers a generator as needed and the primary motive force comes from the batteries powering the electric motor. The improved efficiency of the hybrid buses would mean savings of 20,000 gallons of diesel fuel per bus over the 12 year service life of a bus. The stop and go driving pattern of an urban bus is the ideal environment for a hybrid allowing lots of opportunity for regenerative braking to provide maximum efficiency.
[Source: The Auto Channel]
Reader Comments (Page 1 of 1)
Tim 5:27PM (12/01/2006)
A series hybrid... Electric vehicle with a diesel Auxiliary Power Unit. Let's see... It works for ships, trains, busses, trucks, .... Maybe cars? They just can’t seem to work this out. Let’s help them … OK Guys, add more batteries and a plug and you have a PHEV. Use the same, VegOil or bio-diesel APU, Motors, Controllers, Batteries and more throughout all lines. Heck, use the "skateboard" tech you were talking about years ago and just re-tune the motor controller and change the sheet metal for each vehicle type. Talk about economies of scale! Who needs Hydrogen or expensive and complicated "Power Split" transmission device? These things should be less expensive to make than what you're are making now and you could charge more!! Far fewer parts to inventory & distribute, and a mechanic that can work on one can work on them all. This is OLD TECH!!! http://www.autoworld.com/news/GMC/Series_Hybrid.htm
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Howard Lee Harkness 8:29PM (12/01/2006)
The advantage of a series hybrid is that you can spec the engine for the average load, maybe with a small fudge-factor. A diesel, in particular, can be made very efficient and almost maintenance-free if it is designed for a steady load at a constant RPM.
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DB 9:37PM (12/04/2006)
This is great and is an underestimated use for hybrid technology. As the article stated, 20,000 gallons of diesel saved over the bus' 12 year life span. A typical Camry Hybrid driver over 12 years who drives 200,000 miles would probably save about 1500 gallons.
If alot of cities adopt series hybrids, it would decrease the subsidies that are needed in alot of cities for public transportation. Win-win.
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George Krpan 9:38PM (12/01/2006)
It's interesting that the hybrid got better mileage than the diesel. The energy loss of generating the electricity is more than offset by the regenerative braking and the steady load/RPM. I wonder what the contribution of each of these factors are individually.
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CM 3:11AM (12/02/2006)
Interesting to note that they did not compare the Daimler diesel series hybrid bus to the GM Allison diesel "power split" hybrid bus. The ability of "power split" hybrids to transmit part of the power mechanically should mean less conversion loss and even higher efficiency.
Maybe they just don't want to risk embarassing Daimler.
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Jeff 2:37AM (12/03/2006)
But #4, then you're forgetting the steady RPM and load factor. Its a tough call. You're right, why would you go from mechanical energy to electric and back to mechanical and lose a little bit at each step when you could just bypass the electric when convenient. But then you've got your engine having to deal with varying operating conditions, as well as a much more complicated drivetrain. I'm not too sure which is more energy efficient... Series hybrids do leave the door open though, as far as your energy source goes. You could replace that diesel engine with anything that spits out enough current to keep your batteries charged, so series hybrid technology is easily adaptable to fuel cells or wherever we end up going.
It would be very interesting though to see comparable vehicles set up as both series and parallel hybrids and see which is more efficient. Not a very easy test to arrange though.
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Redacted 8:48PM (12/04/2006)
This is promising since Seattle's brand new fleet of diesel hybrids got LESS MPG than the regular diesel ones and they cost a lot more.
http://seattlepi.nwsource.com/transportation/203509_metro13.html
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satanmat 11:17AM (2/28/2007)
Please do not call this set up "hybrid" -- this setup SHOULD be called Diesel-Electric... Just like the trains that have used this setup since the 1950s. This should be the future of our fleets until the "Next big thing"
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