Table 4. Hybrid Propulsion Systems
Hybrid Related Systems Manufacturer/Integrator Motor and Internal Gear
BAE Systems (HybridDrive® propulsion system) Type: AC Induction, high-power density
Horsepower: 250 hp continuous (320 hp peak) Torque: 2,700 lb-ft @ 0 rpm Type: Permanent magnet Horsepower: 160 hp continuous Type: Sealed lead acid, Hawker XT, 2 enclosures, 23 modules each, roof mounted Voltage: 520-700 VDC
Diesel Baseline Buses at Mother Clara Hale The diesel buses at Mother Clara Hale depot are Orion V high floor buses, but from a newer bus order than those at West Farms, model year 1999. The diesel buses have DDC Series 50 diesel engines retrofitted with a DPF. These diesel buses are approaching their six to eight year rebuild and two of the ten diesel baseline buses have had the rebuild. One of those buses selected for this study (number 6014) was essentially out of service for four of the 12 month study period. This vehicle has been removed from the evaluation because of this lack of usage.
Hybrid and Diesel Baseline Vehicle Differences The diesel buses are a few model years older than the hybrid buses. Although the hybrid buses are of model year 2002 configuration, they did not go into service until 2004. The diesel buses are high floor and the hybrid buses are low floor. The engines in the buses are also different. The hybrid buses have a Cummins ISB engine and the diesel buses have a DDC Series 50 engine. The Cummins engine is smaller and has significantly lower peak torque. The hybrid engine is intended to be rebuilt at five years of service and then replaced at eight or nine years of service. The hybrid buses have regenerative braking and a slightly smaller diesel fuel tank. The hybrid buses also cost about $95,000 more than the baseline diesel buses. The next order of hybrid buses in NYCT had a hybrid cost approximately $150,000 more than what a “new” standard diesel bus might cost.
DDC Series 50 Diesel and CNG Engine In 2004, DDC discontinued the Series 50 diesel and CNG engine platform. For years, the diesel Series 50 engine has been the workhorse of the transit industry. DDC reported to customers that the Series 50 diesel engine platform could not meet the next round of emissions regulations and was being discontinued in preference to Mercedes Benz engines provided by DDC’s parent company, DaimlerChrysler AG. With the removal of the Series 50 engine product, DDC essentially gave the U.S. transit market for 40-foot buses to Cummins and Caterpillar (and Deere Power Systems for CNG buses).