BUS STOP AlternativeAlternative NT O ME F E T N FuelFuel R E A R P G Transit Buses E Y D U A N C I I T R E D E M ST A AT ES OF Produced for the U.S. Department of Energy (DOE) by the National Renewable Energy Laboratory (NREL), a U.S. DOE national laboratory Produced by the Center for Transportation Technologies and Systems at the National Renewable Energy Laboratory (NREL), a U.S. Department of Energy national laboratory NREL 1617 Cole Blvd. Golden, CO 80401-3393 NREL/TP-425-20513 35th St. DE96013097 October 1996 Craig Ave. Colucci Pkwy. Printed with a renewable-source ink on paper containing at least 50% wastepaper, including 20% postconsumer waste FinalFinal ResultsResults fromfrom thethe NationalNational RenewableRenewable EnergyEnergy LaboratoryLaboratory VehicleVehicle EvaluationEvaluation ProgramProgram Alt Blvd. A lternative Fuel Transit Buses Final Results from the National Renewable Energy Laboratory (NREL) Vehicle Evaluation Program by Robert Motta, Paul Norton, and Kenneth Kelly, NREL Kevin Chandler, Battelle Leon Schumacher, University of Missouri Nigel Clark,West Virginia University October 1996 The authors wish to thank all the transit agencies that participated in this program. World Wide Web: http://www.afdc.doe.gov Alternative Fuels Hotline: 1-800-423-1DOE Final Results Alternative Fuel Transit Buses Table of Contents Executive Summary . 1 Introduction . 3 Background . 3 Program Objective . 4 Program Design . 4 Data Collected . 6 Reliability. 8 Liquefied Natural Gas. 8 Compressed Natural Gas . 10 Alcohol . 10 Reliability Summary . 10 Fuel Economy . 11 Liquefied Natural Gas—Houston Dual-Fuel Buses . 11 Liquefied Natural Gas and Compressed Natural Gas— Dedicated Spark-Ignited Engines . 12 Alcohol . 12 Biodiesel . 13 Fuel Economy Summary. 13 Cost . 13 Operating Costs . 13 Capital Costs . 18 Emissions. 21 Compressed Natural Gas . 21 Alcohol . 22 Biodiesel . 26 Emissions Summary . 26 Other Considerations . 27 Lessons Learned . 28 Future Plans . 28 Summary and Conclusions . 29 Numbers, Numbers, Numbers . 30 iii Executive Summary Transit buses represent one of the best • Metro Dade, in Miami, Florida (five applications for alternative fuels, which methanol buses with Detroit Diesel have already made significant inroads into 6V92 engines and five CNG buses the transit bus market. As of January 1996, with Cummins L10 engines) approximately 4% of the more than 50,000 • Triboro in New York, New York (five transit buses in the United States surveyed methanol buses with Detroit Diesel by the American Public Transit Association 6V92 engines, and five CNG buses ran on an alternative fuel such as ethanol, with Cummins L10 engines) methanol, compressed natural gas (CNG), • Pierce Transit in Tacoma,Washington (10 or liquefied petroleum gas (LPG). Even CNG buses with Cummins L10 engines) more significant, 1 out of every 5 new • Metropolitan Transit Commission, buses on order is an alternative fuel bus. Minneapolis/St. Paul, Minnesota These numbers do not include electric (five ethanol buses with Detroit trolley buses. Diesel 6V92 engines) The National Renewable Energy Laboratory, • Greater Peoria Transit in Peoria, Illinois with funding from the U.S. Department of (five ethanol buses with Detroit Diesel Energy, initiated a program to study the per- 6V92 engines) formance, reliability, costs, and emissions • Bi-State in St. Louis, Missouri (five 20% of alternative fuel transit buses versus biodiesel blend buses with Detroit conventional diesel buses (controls). The Diesel 6V92 engines) program involved collecting detailed opera- The alternative fuel engines in this program tional and maintenance data from more have only a few years of product develop- than 100 buses at eight transit agencies ment, versus decades for the diesel engine; across the country. A program goal was to however, the results show they are compet- have 10 test buses of each alternative fuel ing very well with diesels in many areas: type, with 10 controls, split between two agencies, operating for 18 months.West Vehicle Reliability. Road calls experi- Virginia University used its transportable enced per 1,000 miles of operation con- chassis dynamometer to measure the emis- stitute one measure of a bus’s reliability. sions from the buses using a Central A road call is defined as any event that Business District (CBD) driving cycle. prevents a driver from completing his or her route and results in a call for a Transit properties involved in the program, backup bus. The program studied total and their alternative fuel buses, were: road calls and those attributable to • Houston Metro, in Houston,Texas engine/fuel system-related components (10 liquefied natural gas [LNG] buses only—the areas most likely to be affected with Detroit Diesel 6V92 pilot ignition by alternative fuel use. The number of natural gas engines) engine/fuel system-related road calls for • Tri-Met, in Portland, Oregon (eight LNG the Tacoma CNG buses is the same as for buses with Cummins L10 dedicated the diesel buses. Most other sites show spark-ignited engines) some reliability penalty, but in many 1 Alternative Fuel Final Results Transit Buses cases the causes are either rela- Vehicle Emissions. Emissions tively minor (the buses running were measured on a transportable out of fuel because the driver is chassis dynamometer using the unfamiliar with the vehicle), or CBD driving cycle. appear solvable (fuel filter plug- Natural gas and alcohol buses ging because of fuel quality prob- were shown to have the potential lems at the alcohol sites). to significantly lower particulate Operating Costs. Operating costs matter (PM) and oxides of nitro- of the buses are largely driven by gen (NOx) emissions. With the fuel cost. Fuel cost differ- natural gas, PM emissions were ences versus diesel far outweigh virtually eliminated. any differences in maintenance Test results also showed high costs between the alternative fuel variability in the emissions results and diesel buses. Operating costs from the alternative fuel vehicles. are lowest for the CNG buses, This probably results from the which are approximately equal relative immaturity of the tech- to diesel bus operating costs. nology and from the different Operating costs are the highest maintenance requirements of for the alcohol and biodiesel the alternative fuel engines. buses because of high fuel prices. Investigative emissions testing Capital Costs. Capital costs con- showed substantial reductions sist of the extra cost to purchase in high-emitting vehicles after an alternative fuel bus, and the tune-ups and parts replacements. extra cost (if any) to modify the Both diesel and alternative facilities to fuel, service, and main- fuel technologies have changed tain them. Capital costs are the substantially since we ran our highest for CNG and LNG buses, emission tests. Newer generation and lowest for the alcohol and CNG engines often feature closed- biodiesel buses—inverse to the loop feedback control of air:fuel operating costs. In the future, ratio, which should significantly alternative fuel engine prices are reduce emissions variability expected to decrease as volumes between engines. Newer diesel increase, although whether they engines are electronically man- will be equal to or lower than aged and have lower PM emis- diesel is unclear. sions to meet the latest At the present time, no alterna- Environmental Protection Agency tive fuel combines a low operat- standards. We plan to test both ing cost with a low up-front types of engines in the future. capital cost. Looking to the future, newer, signifi- cantly more advanced alternative fuel engines than those in this pro- gram continue to be introduced, and they promise even better performance. 2 Final Results Alternative Fuel Transit Buses Introduction Background Nevertheless, this information is far superior to none, and often reveals The National Renewable Energy trends that continue to be true Laboratory (NREL) is a U.S. even with newer technology. Department of Energy (DOE) Some people may wonder why we national laboratory; this project was included data on alcohol engines in funded by DOE. this report, as the ethanol and One of NREL’s missions is to objec- methanol engines had been discon- tively evaluate the performance, tinued from production at the time emissions, and operating costs of of this writing. Because this is the alternative fuel vehicles so fleet only study of its kind, we decided to managers can make informed deci- include the information to present sions when purchasing them. an across-the-board comparison of Alternative fuels have made greater alternative fuels. We believed that inroads into the transit bus market documenting the experience with than into any other. Each year, the all the fuels in one report was American Public Transit Association important. We also recently learned (APTA) surveys its members on that one transit authority placed an their inventory and buying plans. order for the ethanol 6V92 engine, The latest APTA data show that so this engine may again become about 4% of the 50,000 transit available. The ethanol information buses in its survey run on an alter- may therefore be more relevant native fuel. Furthermore, 1 in 5 of than we anticipated. the new transit buses that members This report has data and results that have on order are alternative fuel are significantly updated from our buses. This program was designed previous reports, in which we stat- to comprehensively and objectively ed that in some cases (such as with evaluate the alternative fuels in use Miami) the diesel buses started the in the industry. program at a higher mileage In designing a program of this type, (odometer) reading than the alter- our most challenging problem was native fuel buses. The data available providing information on the latest to us were therefore not for compa- products in a short period of time. rable periods in the buses’ life. We Once a new product is introduced, have since received back data on all we must find a suitable fleet that the sites, so comparisons at each has ordered the vehicles, along with site are now made between buses similar diesel controls.