The Ottawa, Canada, City Council has put a planned C$536-million (US$462-million) purchase of new hybrid buses on hold to allow for further study of natural gas buses as an alternative from both a financial and an emissions frame of reference.
City council staff, in its Fleet Emissions Reduction Strategy, had originally recommended the purchase of 226 diesel-electric hybrid buses over the next three years as the mid-term solution in the move to a zero emission transit fleet.
As part of the overall analysis, the staff had assessed Compressed Natural Gas (CNG) as an option and rejected it as too costly in capital investment while providing no emissions advantage as clean diesel and diesel-electric hybrids evolved.
In August 2005, a consortium headed by Enbridge (the operator of Canada’s largest natural gas distribution company), along with Cummins-Westport and Clean Energy presented an unsolicited proposal to the City Manager and Deputy City Manager, Public Works and Services to acquire 226 CNG buses in lieu of the 226 diesel-electric hybrid buses.
The group cited four main reasons for doing so; financial, reliability, environmental, and directional. Their submission noted the high cost and inefficiency of first generation CNG engines, but claimed that second- and third-generation engines altered the financial situation significantly.
After analyzing the information and, according to the staff report, re-visiting the Fleet Emissions Reduction Strategy, Ottawa staff held firm:
The work confirmed the validity of the Fleet Emissions Reduction Strategy, even when using newer information on costs provided by the consortium, and confirmed that the diesel-electric hybrid is the appropriate technology for the mid-term solution.
However, during its 30 November meeting, the city council agreed to an independent cost-shared study (Enbridge will pick up half the cost) comparing the hybrid buses with natural gas buses. The study is due by March 2006.
The Council did commit to buying 63 clean-diesel buses in the interim.
The city had contracted the Hybrid Bus Feasibility Study in fall 2004 to the National Research Council’s Centre for Surface and Transportation Technologies (CSTT), a research and development facility in Ottawa. CSTT provided an independent evaluation of the two commercially available hybrid systems for the Ottawa-specific transit system network (including transitway) and climate (winter): the GM-Allison hybrid drive, and BAE Systems HybriDrive.
Among the findings of the study were the following:
Based on the calculated fuel data, the greatest fuel savings would be realized on routes that are presently served by 60-foot articulated buses. The City should therefore consider operating a mixed fleet of 40-foot and 60-foot hybrid-electric buses, or perhaps exclusively 60 foot buses.
Hybrid systems will not provide sufficient fuel savings on low-stop frequency and high-speed routes or rural routes to offset initial cost.
Given the mechanical and electrical complexity of the two drive systems, CSTT does not recommend purchasing both the hybrid drives as part of a mixed fleet purchase. Training and maintenance costs, already an issue with hybrid buses, could be unnecessarily high. CSTT therefore recommends that the hybrid electric drive should be sourced from a single supplier.
Both the Allison and BAE Systems propulsion units would provide significant fuel and emissions savings on Ottawa bus routes. The Allison hybrid system achieved slightly better performance results based on a series of tests performed on model year 2001 hybrid buses. Additionally, the Allison propulsion system is lighter, displayed lower fuel consumption (albeit statistically not significant), lower predicted life cycle costs (based on limited historical data from other hybrid users) and does not require an external battery conditioning system.
The Allison hybrid drive has the flexibility to be installed in 60-foot articulated buses that currently make up about 25% of the Ottawa transit bus fleet. According to BAE Systems and Orion, the BAE Systems HybriDrive should be available in a 60-foot bus by 2010.
Ottawa City Council: Natural Gas Option in Lieu of Diesel-Electric Hybrid Buses
Ottawa City Council: Hybrid Bus Feasibility Study Report