A national laboratory of the U.S. Department of Energy Office of Energy Efficiency & Renewable Energy National Renewable Energy Laboratory Innovation for Our Energy Future King County Metro Transit Technical Report NREL/TP-540-40585 Hybrid Articulated Buses: December 2006 Final Evaluation Results K. Chandler Battelle K. Walkowicz National Renewable Energy Laboratory NREL is operated by Midwest Research Institute ● Battelle Contract No. DE-AC36-99-GO10337 King County Metro Transit Technical Report NREL/TP-540-40585 Hybrid Articulated Buses: December 2006 Final Evaluation Results K. Chandler Battelle K. Walkowicz National Renewable Energy Laboratory Prepared under Task No. FC07.3000 National Renewable Energy Laboratory 1617 Cole Boulevard, Golden, Colorado 80401-3393 303-275-3000 • www.nrel.gov Operated for the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy by Midwest Research Institute • Battelle Contract No. DE-AC36-99-GO10337 NOTICE This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. 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Box 62 Oak Ridge, TN 37831-0062 phone: 865.576.8401 fax: 865.576.5728 email: mailto:[email protected] Available for sale to the public, in paper, from: U.S. Department of Commerce National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 phone: 800.553.6847 fax: 703.605.6900 email: [email protected] online ordering: http://www.ntis.gov/ordering.htm Printed on paper containing at least 50% wastepaper, including 20% postconsumer waste Acknowledgements This evaluation is funded through the Advanced Vehicle Testing Activity, which is managed by Lee Slezak within the FreedomCAR & Vehicle Technologies Program in the U.S. Department of Energy (DOE). All publications on the King County Metro Transit hybrid bus evaluation will be posted on the DOE Office of Energy Efficiency and Renewable Energy Web site. Please see http://www1.eere.energy.gov/vehiclesandfuels/avta. This evaluation conducted at King County Metro Transit (KC Metro) would not have been possible without the support and cooperation of many people. Therefore, the authors wish to thank each of the following: U.S. Department of Energy Lee Slezak NREL Leslie Eudy KC Metro Jim Boon Colleen Duke Bernie Durant Todd Gibbs Ann Gonzales Wayne Hom Lynn Matteoni Jo Merrick George Stites GM Allison Peter Chiang Paul Nama New Flyer Industries Rick Brandenburg Paul Zanetel Caterpillar Dave Bradshaw NC Power Bill Hofer Craig Johnson iii Table of Contents Executive Summary........................................................................................................................v Project Design and Data Collection............................................................................................v Hybrid and Diesel Buses............................................................................................................vi Implementation Experience.......................................................................................................vi Evaluation Results....................................................................................................................vii Emissions Testing......................................................................................................................ix Future Work...............................................................................................................................ix Changes and Additions Since the Interim Report...........................................................................1 Overview.........................................................................................................................................1 Advanced Vehicle Testing Activity............................................................................................1 Host Site Profile—KC Metro Transit.........................................................................................2 Description of the KC Metro Hybrid Transit Bus Project..........................................................2 Project Design and Data Collection............................................................................................8 Vehicle System Descriptions......................................................................................................9 Facility Descriptions.....................................................................................................................14 Implementation Experience..........................................................................................................16 Evaluation Results (12 Months)....................................................................................................18 Route Descriptions....................................................................................................................18 Bus Usage.................................................................................................................................19 Fuel Economy and Cost............................................................................................................21 Maintenance Cost Analysis.......................................................................................................24 Road Call Analysis...................................................................................................................34 Summary of Costs.....................................................................................................................35 Laboratory Emissions Testing..................................................................................................36 Future Work..................................................................................................................................38 Contacts.........................................................................................................................................39 Acronyms and Abbreviations.......................................................................................................40 Bibliography.................................................................................................................................42 Appendix: Fleet Summary Statistics.............................................................................................44 iv Executive Summary This is the final report to evaluate and compare new diesel and diesel hybrid electric articulated buses operated as part of the King County Metro Transit (KC Metro) fleet in Seattle, Washington. It concludes a 12-month evaluation at KC Metro. The evaluation was completed through the U.S. Department of Energy’s (DOE) Advanced Vehicle Testing Activity (AVTA) by the National Renewable Energy Laboratory (NREL). KC Metro operates bus-only transit service in the 2,134-square-mile Seattle/King County, Washington, area. Its fleet consists of 1,400 standard and articulated buses, trolley buses, and streetcars. KC Metro recently began using 235 new hybrid electric articulated buses that replace an older fleet of 236 dual-mode Breda articulated buses. The Breda buses were specially developed for use in the 1.3-mile Seattle downtown transit tunnel since its opening in 1990. This tunnel was built with light rail in mind but had been used only by the Breda dual-mode buses until the hybrid buses were introduced. The Breda dual-mode buses allowed zero-emission, fully electric propulsion operation inside the tunnel, and diesel engine propulsion outside the tunnel or when the buses were not connected to the electric catenary system.1 Both the diesel and diesel hybrid electric articulated buses at KC Metro were manufactured by New Flyer Industries. The hybrid buses include General Motors’ (GM) Allison EP50 System parallel hybrid propulsion system. This fleet is the largest application of the GM Allison hybrid propulsion system to date. Project Design and Data Collection This evaluation focused on diesel and hybrid diesel buses selected from three of KC Metro’s seven operating depots or bases (see Table ES-1). All 30 of the new diesel articulated buses currently operate from the Ryerson Base depot; they are identical to the hybrid buses except for the hybrid electric propulsion systems. Ten diesel buses were selected from Ryerson Base for detailed evaluation, and 10 hybrid buses were selected from Atlantic Base for comparison. The Ryerson diesel buses and the Atlantic hybrid buses have similar service and duty cycles— downtown service at an average speed of 12.4 mph for Ryerson and 11.6 mph for Atlantic during the first six months of the evaluation period, and 12.3 mph for Ryerson and 10.5 mph for Atlantic during the second six months. This difference is attributed to route changes during the evaluation period. During the first six months of the demonstration, the hybrid buses were operating in the downtown transit tunnel, while during the second six months, the tunnel was closed and all buses drove the surface streets in downtown Seattle. 1 A catenary system features electricity-carrying wires strung above a roadway. Buses and trolley vehicles can obtain access to electric power via poles that touch the catenary wires and provide electricity directly to the electric propulsion system in the bus. Many light rail systems also use a catenary system to provide the light rail vehicle with access to electricity and power for propulsion. v Table ES-1. Summary of Evaluation Sites and Buses Topic Ryerson Base Atlantic Base South Base Number of Buses in Evaluation 10 10 10 Bus Type Diesel Only Diesel Hybrid Diesel Hybrid Evaluation Period April 1, 2005—March 31, 2006 South Base hybrid buses (10 buses) were also selected for study, because that depot was the first to receive the new hybrid vehicles. South Base provided an opportunity to study an early implementation experience with the new technology at KC Metro, as well as to look at longer term potential maintenance and reliability issues that might arise in these oldest of the fleet buses. South Base has a higher operating average speed (19.5 mph for articulated buses in the first six months and then 18.1 mph for the second six months) than the other two depots and should not be used in direct comparison. Data from this depot are therefore provided for reference only. The South Base evaluation results appear in gray type in this report as a reminder that the information is not intended to be directly compared with results from the other two depots. Hybrid and Diesel Buses The New Flyer diesel and diesel-hybrid articulated buses are identical except for the GM Allison EP50 parallel hybrid system. Both types of buses are equipped with Caterpillar (CAT) engines (C9-330 brake horsepower [bhp] maximum, 1,150 ft-lb torque and diesel particulate filters or DPF). The hybrid buses weigh approximately 1,100 lb more than the diesels, but this does not make a difference in the number of passengers that can be carried because there is not enough standing space on either one to take the bus to the gross vehicle weight rating (GVWR). The GM Allison EP50 parallel electric propulsion system has a drive unit that contains two motors and fits where a standard-size transmission would normally be placed in the bus. Each motor, which can also act as a generator, is capable of 75 kW continuous power and up to 150 kW peak power. This parallel hybrid propulsion system blends both the CAT engine power and the electric motor power to provide propulsion power. The energy storage system for the hybrid electric system consists of nickel metal hydride batteries, and the system operates with regenerative braking (i.e., braking energy is captured back through the motor/generator set and used later for propulsion along with the energy saved in the battery pack). The CAT engine is also capable of charging the energy storage system along with the regenerative braking energy. Implementation Experience New diesel and diesel-hybrid articulated buses were delivered to KC Metro at nearly the same time in May 2004. The 30 diesel buses were onsite and in service at Ryerson Base depot by July 2004. All 235 hybrid buses were delivered and put into service at Atlantic Base and South Base as well as two other depots by early December 2004. KC Metro reported that there were no significant issues in placing the buses into service. It took only a few weeks after each bus was delivered to Seattle. As the new articulated buses were placed in service, the older Breda buses were retired. CAT used a local dealer for warranty support and in troubleshooting problems with these buses. New Flyer made one vi mechanic/technician available on site for KC Metro’s needs. GM Allison also provided onsite technical support as needed. The buses are reportedly doing well; through March 2006, the 235 hybrid buses had operated for 13 million miles and the 30 diesel buses for 1.7 million miles. The hybrid and diesel buses have been operating with only a few significant issues. There have been a few “fleet defects” and “campaigns” of warranty repairs as the manufacturers gained more experience with the KC Metro operation and environment, as well as specific design issues concerning the integration of the bus systems. A “fleet defect” is defined in the contract between the transit agency and the manufacturer as “failures of the same type occurring on multiple buses in an order.” A “campaign” is a repair (typically covered under warranty) that is applied to an entire (or significant portion) of an order of buses. The following list summarizes some of the significant (major) campaigns for the propulsion system of these buses (some of which occurred during the evaluation period of this project): 1. Axle planetary snap rings (8/2004) 2. Allison software upgrade for issues with the inverter and CAT engine software changes (9/2004) 3. Proheat auxiliary coolant heater software change (1/2005) 4. Relocation of the DPF and change of the thermal blanket (2/2005) 5. Allison software upgrade for additional CAT engine software changes and HUSHTM mode hybrid thermal protection (5/2005) 6. Allison software upgrade for removing HUSH mode and a few software enhancements (10/2005) - removal of HUSH mode was at the request of KCM due to 2-year Transit Tunnel shutdown for remodeling. It will be re-activated again in 2007. 7. Voltage regulator retrofit (11/2005) 8. Replacement of turbocharger, heavier usage than expected, using titanium turbocharger parts (1/2006). The problem in item eight above, includes a warranty campaign for the CAT engine turbocharger. This problem, caused by heavier than expected usage, has resulted in a few turbocharger failures and, ultimately, associated DPF failures because of engine oil leaking into the exhaust through the damaged turbocharger. CAT has replaced the turbocharger compressor wheels with components made with titanium to alleviate this issue. April 1, 2005, was chosen as a “clean point” for the evaluation because by then the major campaigns listed above were completed. The evaluation period selected for this report is April 2005 through March 2006. Evaluation Results The evaluation results presented in this report focus on the diesel buses operating from Ryerson Base and hybrid buses operating from Atlantic Base. These two depots were chosen for the evaluation because of their similar duty cycles, as noted earlier. South Base hybrid buses are included in the evaluation only to note some experiences in implementing the first hybrids at KC Metro. The duty cycle of the South Base hybrid buses was significantly different from those at the other two depots. It is not directly comparable and is included in this report for reference only. vii Table ES-2 summarizes the evaluation results presented in greater detail later in this report. Note that South Base hybrid data are presented but not included in the comparison discussion. Regarding maintenance costs, mechanic labor was kept constant at $50 per hour, which is not the actual labor rate at KC Metro. Data in the table column titled “Hybrid Difference” was calculated in this manner: (Result Hybrid Atlantic Base / Result Diesel Ryerson Base—1)* 100% A positive result (+) indicates that the hybrid Atlantic Base result was higher than the diesel Ryerson Base result. A negative result (-) indicates that the hybrid Atlantic Base result was lower than the diesel Ryerson Base result. Table ES-2. Summary Evaluation Results (12-month evaluation period) Diesel Hybrid Ryerson Atlantic Hybrid Hybrid Category Base Base Difference South Base Monthly Average Mileage per Bus 2,949 3,096 +5% 3,957 Fuel Economy (mpg) 2.50 3.17 +27% 3.75 Fuel Cost per Mile ($) (@$1.98/gal) 0.79 0.62 -22% 0.53 Total Maintenance Cost per Mile ($) 0.46 0.44 -4% 0.41 Propulsion-Only Maintenance Cost 0.12 0.13 +8% 0.13 per Mile ($) Total Operating Cost per Mile ($) 1.25 1.06 -15% 0.94 Miles Between All Road calls 5,896 4,954 -16% 4,696 Miles Between Propulsion Road 12,199 10,616 -13% 8,547 calls • Bus Usage—The diesel buses at Ryerson Base and hybrid buses at Atlantic Base had essentially the same monthly average mileage per bus; average mileage for the Atlantic Base hybrid buses was only 5% higher. • Fuel Economy—The hybrid buses at Atlantic Base had on average 27% higher fuel economy than the diesel buses at Ryerson Base. This difference ranged from 24% up to 30% during the evaluation period (0.67 mpg difference). • Fuel Cost per Mile—The diesel buses at Ryerson Base used a biodiesel blend of 5% biodiesel (B5) and 95% ultra-low-sulfur diesel (ULSD) costing an average of $2.01 per gallon during the evaluation period. The hybrid buses at Atlantic Base used only ULSD costing an average of $1.98 per gallon during the evaluation period. The fuel cost and fuel economy combined resulted in a fuel cost per mile that was 22% lower (assuming only the ULSD cost of $1.98 per gallon for both) for the hybrid buses at Atlantic Base than that of the diesel buses at Ryerson Base ($0.17 per mile difference). • Total Maintenance Cost per Mile—The hybrid buses at Atlantic Base and the diesel buses at Ryerson Base had similar total maintenance cost per mile; this cost for hybrid buses was 4% lower ($0.02 per mile difference). • Propulsion Only Maintenance Cost per Mile—The propulsion-related systems are transmission, nonlighting electrical (charging, cranking, and ignition), air intake, cooling, exhaust, fuel, engine, electric propulsion, and hydraulics. The hybrid buses at Atlantic Base and the diesel buses at Ryerson Base had similar cost per mile for this category with the hybrid buses being 8% higher ($0.01 per mile difference). • Total Operating Cost per Mile—This category is the sum of the fuel cost per mile and the total maintenance cost per mile. Total operating costs for the hybrid buses at Atlantic viii Base were 15% lower than those of the diesel buses at Ryerson Base ($0.19 per mile difference). • Miles Between All Road Calls—The definition of road call is taken from the Federal Transit Administration (FTA) National Transit Database (NTD). A road call, or revenue vehicle system failure, is defined as a failure of an in-service bus that causes the bus to be replaced on its route or that causes a significant schedule delay. The hybrid buses at Atlantic Base had a 16% lower rate of miles between all road calls than that of the diesel buses at Ryerson Base. • Miles Between Propulsion Road Calls—The rate for hybrid buses at Atlantic Base in this category was 13% lower than that of the diesel buses at Ryerson Base. Emissions Testing Two buses were tested at NREL’s ReFUEL laboratory in Golden, Colorado, in May and June 2005. One bus (vehicle 2899) was from the conventional diesel fleet (from Ryerson Base Depot), and another bus (vehicle 2709) was from the hybrid fleet (one of the 235 hybrids ordered). Both vehicles were tested for fuel economy and emissions performance on identical cycles. Four cycles were tested to determine the variability of fuel economy and emissions: Central Business District 14 (CBD), Manhattan, the Orange County Transit Authority (OCTA), and a custom cycle made up of various King County runs (KCM). Each vehicle was tested multiple times on each run to ensure some level of statistical accuracy. Fuel economy, carbon dioxide (CO ), 2 carbon monoxide (CO), nitrogen oxides (NOx), and particulate matter (PM) were measured. Differences in measurements between the hybrid and the conventional bus are shown in Table ES-3. Table ES-3. Hybrid Bus vs. Conventional Bus Test Results In-use: Manhattan OCTA CBD KCM Atlantic Base Fuel Economy (mpg, % increase) 74.6% 50.6% 48.3% 30.3% 26.8% Fuel Consumption (gram/mi, % reduction) 42.9% 33.7% 32.8% 23.4% 21.2% NOx (gpm, % reduction) 38.7% 28.6% 26.6% 17.8% - PM (gpm, % reduction) 92.6% 50.8% 97.1% Ns - CO (gpm, % reduction) ns 32.0% 48.0% 59.5% - THC (gpm, % reduction) ns ns 75.2% 56.3% - Note: gpm = gallons per mile; mpg = miles per gallon; ns = not statistically significant at 95% confidence level or not enough data to determine; THC = total hydrocarbon. Detailed information on this testing is available later in this report. It will also be available online in the report KCM Transit Emissions (www.nrel.gov/vehiclesandfuels/ahhps/publications.html). Future Work All the new diesel and hybrid articulated buses ordered from New Flyer have been in service since at least December 2004. This final evaluation report provides results from a 12-month evaluation period. The first six months covered in this report included operation of the hybrid buses in the downtown transit tunnel. The second six months of operation were with the transit tunnel closed. The HUSH mode feature of the hybrid buses was deactivated via software in ix