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Hydrogen Fleet Experiences
Unitrans Moves Passengers With CNG
Last Updated: August 22, 2007
Unitrans, a student-run transit system that serves the University of California at Davis and the City of Davis, currently operates 27 compressed natural gas (CNG) transit buses, five CNG shuttle buses, two electric light-duty vehicles, 11 medium- and heavy-duty CNG vehicles, and four light-duty CNG-powered vehicles. Unitrans is among the first fleets in the nation to develop a transit bus that will operate on a hydrogen/CNG mixture; the company plans to begin testing by the end of 2007. Two hundred student employees and 14 career employees run the system, which transports 20,000 passengers each weekday (more than 3 million annually). About 95% of Unitrans' mileage is driven by alternative fuel buses.
Unitrans currently has its own CNG fueling station and plans to complete a new hydrogen/CNG refueling station, as well. "CNG compressors and related equipment are best protected from the elements within an enclosed structure. Completing the planned blended hydrogen/CNG fueling station has been very difficult because local safety personnel have required a wide array of safety elements that were not anticipated during the planning phase," explains General Manager Geoff Straw. "It seems that we're establishing new protocols due to the unique nature of the project. For this reason, the hydrogen compressor had to be located outside the existing CNG compressor/equipment building, which has delayed completion of the project for the past two years."
In addition to the CNG/hydrogen start up challenges, Straw indicated that "the technological learning curve was steep for our technicians. In fact, many of my peers in the transit industry and I are having difficulty finding trained compressed-fuel technicians." Two additional factors have surfaced in the process of operating a CNG fleet. Planning has had to include the increased capital costs of operating CNG vehicles due to the 15-year life of the vehicle's CNG fueling tanks. "We have two options when the CNG tanks have reached their maximum operational life. We can replace the tanks (about $75K per vehicle) or replace the vehicle entirely, both of which require large amounts of funds. With a conventional diesel vehicle, we can replace old/dirty engines with newer/cleaner diesel engines and the bus can operate for a much longer time with little financial investment." Another important factor is the limited number of CNG engine manufacturers in the transit market. Straw indicates that "some of us who have invested in CNG infrastructure are concerned about future pricing and support."
Despite these challenges, Unitrans is committed to clean technology and has selected CNG as its fuel of choice. "The low per-mile fuel cost of natural gas is attractive. It's a proven technology and we've had 12 years of experience with it." says Straw.
Contact Unitrans at http://unitrans.ucdavis.edu/ or Geoff Straw at gdstraw@ucdavis.edu.
