This report presents an up-to-date description of emerging hybrid-electric drive technology for transit buses in the United States. The technology and its status, benefits, life-cycle costs, and deployment issues are discussed. The report is intended to provide transit agencies with information to compare the emissions and fuel economy expected from hybrid-electric transit buses with those expected from clean diesel or alternatively fuelled buses. The report will be of interest to transit managers, bus manufacturers, operations and maintenance professionals, energy specialists, and others concerned about the deployment of or conversion to hybrid-electric vehicle technology. Hybrid-electric drive systems on transit buses are being aggressively investigated as a means of improving fuel economy, reducing emissions, and lowering maintenance and operating expenses. Several major federally funded research and development projects are testing the viability of these drive systems on buses. In addition, a number of demonstrations are underway or have been recently completed by transit agencies. With the rapid pace of development and improvement of hybrid-electric drive technology, more transit agencies are being asked to evaluate the potential for hybrid-electric drive systems in their fleets. To assist transit managers with this evaluation, this report presents an overview of the emerging hybrid-electric drive technology in the United States. It is intended to provide transit managers with a better understanding of the technology, including benefits, challenges, and life-cycle costs. Under TCRP Project C-10B, research was undertaken by the Northeast Advanced Vehicle Consortium and, through a subcontract, by M.J. Bradley & Associates to provide the following: (1) definitions and descriptions of hybrid-electric drive systems, including all relevant terminology; (2) information about the status of current hybrid-electric transit bus research and development activities underway; (3) a description and status assessment of hybrid-electric transit bus demonstration programs planned or underway at transit systems around the country; (4) a discussion of the benefits of hybrid-electric technology (quantified where possible), including life-cycle cost benefits; (5) a discussion of the issues and risks associated with the deployment of hybrid-electric drive technology; and (6) a method that will enable transit agencies to compare the expected emissions levels and fuel economy of hybrid-electric transit buses with those of clean diesel and alternatively fuelled buses. To achieve the project objectives, the researchers conducted an extensive assessment of the state of hybrid-electric drive technology in U.S. transit systems. This assessment included a literature search of emerging technology, auxiliary power units, electric-drive motors and inverters, energy storage, systems integration, hybrid bus emissions, bus costs, and fuel economy characterisation. The researchers interviewed manufacturers to determine an up-to-date understanding of product plans and market trends for hybrid-electric transit buses and drive systems currently in development or commercially available. Transit agencies that have early experience deploying the technology were surveyed to obtain specifics on current cost/benefit issues as well as the problems, successes, and failures of their deployment programs. Findings are presented in terms of the operational characteristics, acquisition costs, fuel economy, and drive cycle emissions associated with hybrid-electric drive systems relative to conventional diesel- and mechanical-drive systems. The report also presents case study descriptions of hybrid bus demonstration programs in New York City, Los Angeles, and Cedar Rapids. (A)
Abstract