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Transport Refrigeration Unit, or TRU, is an example of a diesel emission source that will be regulated in the future. The TRU is used to provide refrigerated space during the transport of fruits, vegetables, meat, pharmaceuticals, beverages, and any other product that needs a temperature controlled environment while being transported. TRUs are used in all modes of transport, on rail cars, on ocean going shipping containers, over the road truck trailers and even on airplane Unit Load Devices. Policy making bodies, understanding the adverse effects of diesel emissions, noise pollution, and fuel consumption have started to pass legislation in an effort to curtail transport diesel emissions. At the local level many states as well as some municipalities have instituted policy designed to eliminate these sources of pollution.

In this paper a model of Trailer Refrigeration Units, TRUs, has been developed to quantify the fuel economy and emissions benefits of alternative power systems. Trailer refrigeration units (TRUs) are refrigeration systems typically powered by a separate diesel engine, and they are used to deliver fresh and frozen food products. The products can be very sensitive to temperature variation and maintaining the proper environment is very important. The diesel engines currently used to power the refrigeration system can contribute to high amount of local emissions at the loading warehouse. A promising future alternative is the use of fuel cell auxiliary power units (APUs). In this paper we have developed a MATLAB/Simulink based modeling of TRUs, and we have used the model to quantify the benefits of alternative power systems. The simulation model consists of an unsteady thermal modeling of TRUs that is coupled to the APU.

This paper compares the merits of operating a direct-hydrogen fuel cell (DHFC) system using a high-pressure air supply (compressor) versus one using a low-pressure air supply (blower). Overall, for the system modeled, it is shown that there is no inherent performance advantage for either mode of operation at the DHFC stack level. However, in practical applications, as will be shown in this paper, a systems analysis (stack and air supply) of power and efficiency needs to be performed. Equivalent PEM DHFC stack peak power values can be obtained using both high-pressure and low-pressure air supply systems. For each air supply configuration, air mass flow and pressure operating conditions can be found that result in an equal value of the oxygen partial pressure at the cathode catalyst layer surface. However, at the system level, the required air supply power needed to achieve the same DHFC stack performance values can be drastically different for high and low pressure operation.

This work presents a method to maximize the net power output of an indirect methanol PEM fuel cell system. This method establishes an operating strategy for the air supply based on the stack, air supply and water and thermal management (WTM) sub-system characteristics - holding anode conditions constant. It is shown that operating strategies based on individual components result in the inefficient operation of the overall system. Inclusion of the WTM modifies the optimal operating conditions for both low and high pressure systems. However the results for high pressure show an efficiency gain through reducing air pressure and increasing airflow, the opposite of what is expected. This work also outlines the components and issues not included and their importance in system operation.

Vehicle manufacturers claim that fuel cell vehicles are significantly more fuel-efficient and emit fewer emissions than conventional internal combustion engine vehicles /1/. A computer model can help to explore and understand the underlying reasons for this potential improvement. In previous published work, the UC Davis Vehicle Model for the case of a load-following Indirect Methanol Fuel Cell Vehicle (IMFCV) has been introduced and discussed in detail /2/. Because of possible technical barriers with load following vehicles, as well as near term cost issues, hybrid fuel cell vehicle concepts are widely discussed as another fuel cell vehicle option. For load following vehicles, the questions of fast start up and fuel processor dynamics in extreme transient situations, (e.g., during phases of hard acceleration) are not totally resolved at this time. For both of these performance issues, a hybrid design could offer at least an interim solution.

Near term (ca. 2005) Fuel Cell Vehicles (FCVs) will primarily utilize Direct-Hydrogen Fuel Cell (DHFC) systems. The primary goal of this study was to provide an analytical basis for including a realistic Compressed Hydrogen Gas (CHG) fuel supply simulation within an existing dynamic DHFC system and vehicle model. The purpose of this paper is to provide a tutorial describing the process of modeling a hydrogen storage system for a fuel cell vehicle. Three topics were investigated to address the delivery characteristics of H2: temperature change (ΔT), non-ideal gas characteristics at high pressures, and the maximum amount of hydrogen available due to the CHG storage tank effective “state-of-charge” (SOC) -- i.e. how much does the pressure drop between the tank and the fuel cell stack reduce the usable H2 in the tank. The Joule-Thomson coefficient provides an answer to the expected ΔT during expansion of the H2 from 5000 psi to 45 psi.

The University of California, Davis FutureTruck team redesigned a 2000 Chevrolet Suburban as a Hybrid Electric Vehicle to meet the following goals: reduce fuel cycle greenhouse gas emissions by 66%, increase vehicle fuel economy to double that of the stock Suburban, meet California's Super Ultra Low Emissions Vehicle standard, and qualify for substantial Partial Zero Emissions Vehicle credits in California. Sequoia meets these goals with an efficient powertrain, improved component systems, and an advanced control system. Sequoia utilizes two independent powertrains to provide Four-Wheel Drive and achieve stock towing capacity. The primary powertrain combines a 1.9L gasoline engine inline with a 75 kW brushless DC motor driving the rear wheels. This powertrain configuration is simple, compact, reliable, and allows flexibility in control strategy. The secondary powertrain employs a 75 kW brushless DC motor to drive the front differential.

Fuel cell engines are expected to deliver greater efficiency and lower emissions than conventional transit bus powertrains in the near future. Although experimental vehicles have demonstrated the emission and efficiency benefits of fuel cell power, the next step toward implementation is widespread fleet demonstrations to prove the technology in the field. In order to aid in the start of new demonstrations and speed fuel cell technology towards the fleet vehicle marketplace, an assessment of the needs, risks, and advantages of using fuel cell power must be obtained from a consumer perspective. It has been assumed that the increased fuel efficiency that is inherent to fuel cell systems will lower operating costs as compared with conventional diesel powertrains. A comparison of two fuel cell buses and a diesel bus was completed in order to quantify the operational cost benefits and identify potential cost deterrents to fuel cell bus implementation.

Yosemite is an advanced hybrid electric vehicle built on the Ford U152 Explorer platform. The University of California, Davis, FutureTruck team designed Yosemite to meet the following objectives: 1 Maximize vehicle energy efficiency 2 Minimize petroleum consumption 3 Reduce fuel cycle greenhouse gas emissions 4 Achieve California Super Ultra Low Emission Vehicle (SULEV) target 5 Deliver class-leading performance The University of California, Davis FutureTruck team redesigned a 2002 Ford Explorer as a Hybrid Electric Vehicle to meet the following goals: reduce fuel cycle greenhouse gas emissions by 67%, double the fuel economy of a stock Explorer, meet California's Super Ultra Low Emissions Vehicle standard, and qualify for substantial Partial Zero Emissions Vehicle credits in California. Yosemite meets these goals with an efficient flexible fuel hybrid powertrain, improved component systems, and an advanced control system.

This paper presents experimental data and an analysis of a proton exchange membrane fuel cell system for electric vehicle applications. The dependence of the fuel cell system's performance on air stoichiometry, operating temperature, and reactant gas pressure was assessed in terms of the fuel cell's polarity and power density-efficiency graphs. All the experiments were performed by loading the fuel cell with resistive heater coils which could be controlled to provide a constant current or constant power load. System parasitic power requirements and individual cell voltage distribution were also determined as a function of the electrical load. It was found that the fuel cell's performance improved with increases in temperature, pressure and stoichiometry within the range in which the fuel cell was operational. Cell voltage imbalances increased with increases in current output.

Several lead-acid battery packs of different manufacture and voltage were evaluated on a performance and life-cycle basis. The battery packs ranged from a small 36 volt laboratory pack to a 320 volt full size U.S. Electricar S-10 truck pack. The influence of the charge algorithm, ambient temperature, and module connection methods for parallel strings on the performance and cycle-life of this laboratory pack was studied. Finally, a survey of presently employed battery management techniques, used in three “production” electric vehicles, was conducted. A standard set of testing procedures for electric vehicle batteries, based on industry accepted testing procedures, were used in the evaluations. The battery packs were evaluated by a combination of constant current capacity tests, cyclical loading to simulate typical EV driving cycles and actual EV driving experience.

The zinc bromine battery is a high energy density sealed battery that utilizes a flowing electrolyte and low cost materials (predominantly plastic) and operates at ambient temperatures. The typical full scale specific energy for this bipolar plate battery is more then twice that of lead acid batteries. The engineering research presented in this paper is the design and construction of a high-voltage, zinc bromine battery for use in an electric vehicle. Specifically, a 390 volt system is being integrated into a US Electricar S10 light-duty truck. The research goal is to show a reliable and practical electrochemical power system that is lighter and provides a longer range and shorter recharge times than lead acid batteries. Results of this study will help determine the applicability and practicality of zinc bromine technology for electric vehicles.

A plug-in, charge-depleting, parallel hybrid powertrain has been developed for a high performance sport utility vehicle. Based on the Ford U152 Explorer platform, implementation of the hybrid powertrain has resulted in an efficient, high performance vehicle with a 0-60 mph acceleration time of 7.5 seconds. A dual drive system allows for four-wheel drive capability while optimizing regenerative braking and minimizing electric motor cogging losses. Design of the system focused on reducing petroleum use, lowering greenhouse gas emissions, and reducing criteria tailpipe emissions. Additionally, this vehicle has been designed as a partial zero emissions vehicle (PZEV), allowing the driver to travel up to 50 miles in a zero emission all-electric mode. High-energy traction battery packs can be charged from the grid, yielding higher efficiencies and lower critical emissions, or maintained through the internal combustion engine (ICE) as with a traditional hybrid vehicle.