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Fuel Cell engines have been proposed as alternatives to the internal combustion engine in transportation applications. The dynamics of the fuel cell engine and subsystems are not well understood but play an important role in the proposed application. This study assesses the operation of an indirect methanol fuel cell powertrain from a dynamics perspective and identifies resulting limitations of the system. Relevant data from an indirect methanol fuel cell bus powertrain is presented and discussed. Identification of dynamically limiting processes allows researchers and fuel cell manufacturers to focus on sub-systems that can improve the response times during transient operation. Better understanding also allows for development of control and enhancement methods to mitigate the difficulties associated with the dynamic response of indirect methanol fuel cell vehicles.

Fuel cell engines are expected to deliver greater efficiency and lower emissions than conventional powertrains during operation. However, the projected efficiency and emission benefits of using fuel cell derived power can be significantly reduced if the fuel consumed and emissions produced during start-up and shutdown procedures are included in the analysis of the overall drive cycle. For this reason, an investigation of the drive cycle including the fuel consumed, power required, and emissions produced during the start-up and shutdown of an operational, heavy duty methanol-fueled fuel cell bus has been performed. The fuel consumed and emissions generated during start-up and shutdown were measured and combined with steady operation values to allow mission equivalent fuel mileage and emission outputs to be computed. The results show that the start-up and shutdown contributions can be significant and should be included in fuel efficiency and emission projections.

The shutdown process of an operational phosphoric acid fuel cell transit bus has been investigated. The bus employs a hybrid arrangement of a 50 kW Phosphoric Acid Fuel Cell (PAFC) engine in parallel with Nickel-Cadmium batteries on a 30-foot heavy-duty transit bus chassis manufactured by Bus Manufacturing Inc. The bus uses methanol as the primary fuel, which is processed through a steam-reformer to produce hydrogen used in the fuel cell. Rapid cooling of PAFC power plants will induce component damage. Shutdown of the fuel cell bus is defined as the time that is required for the controlled reduction from operating temperatures within the fuel cell stack and reformer to minimize component degradation. While in general fuel cell vehicles produce low emissions and are very efficient while operating, shutdown of the fuel cell bus represents a significant time requirement, power and fuel consumption, and considerable pollutant emissions with no usable output power.

The start-up process of an operational phosphoric acid fuel cell transit bus has been investigated. The bus employs a hybrid arrangement of a 50 kW Phosphoric Acid Fuel Cell (PAFC) engine in parallel with Nickel-Cadmium batteries on a 30-foot heavy-duty transit bus chassis manufactured by Bus Manufacturing Inc. The bus uses methanol as the primary fuel, which is processed through a steam-reformer to produce hydrogen used in the fuel cell. Start-up of the fuel cell bus is defined as the time that is required to heat up the fuel cell and sub-components to operating temperatures and to establish operating flow conditions. While in general fuel cell vehicles produce low emissions and are very efficient while operating, start-up of the fuel cell bus represents a significant time requirement, power and fuel consumption, and considerable pollutant emissions with no usable output power.

A parametric study was made to compare the potential benefits and liabilities of powering various surface transportation systems with fuel cells. It was found that while the potential fuel savings are greatest for automobiles and light trucks, economics and packaging considerations favor initial applications in locomotives, long distance trucks, and buses. It was further shown that for the alternative fuels likely to be used, infrastructure requirements also favor the commercial vehicles over the personal vehicle. However, the potential benefits to energy conservation and atmospheric pollution reduction are so great that major efforts should continue to adapt fuel cells and alternative fuels to personal vehicles as well as commercial vehicles.

This paper is a summary of the Jet Propulsion Laboratory assessment of advanced electric and hybrid vehicles for potential development by the early 1990s, The primary objective of the assessment was to recommend subsystem research priorities based on a comparison of alternatives as part of complete vehicle systems with equivalent performance. The assessment included evaluations of candidate technologies as well as technical and economic comparisons of vehicle systems for specified missions. The availability of nonpetroleum fuel was also addressed, and preference analyses were used to help evaluate the relative merits of the competing systems.

Using a combination of test results and computer simulations, power and energy requirements for two vehicle types have been projected. These requirements were separated to be provided by two power sources: one for long-term energy and the other for supplementary power for acceleration. On this basis, it is shown that many combinations of sources may be utilized to meet a particular mission. The accompanying fuel is determined on the basis of available energy density, which depends on both the fuel type and the conversion device.

A diesel-electric hybrid bus has been developed at the University of Florida. The drive system is a series hybrid with two lead-acid batteries and a diesel-driven three phase alternator. It was designed with the aid of a computer simulation program, and has undergone three evaluation phases since the initial construction phase. All results to date have confirmed the feasibility of the system including apparent significant advantages in the areas of exhaust emissions and fuel consumption.