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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.

Line-haul truck engines are frequently idled to power hotel loads (i.e. heating, air conditioning, and lighting) during rest periods. Comfortable cabin climate conditions are required in order for mandatory driver rests periods to effectively enhance safety; however, the main diesel engine is an inefficient source of power for this conditioning. During idle, the diesel engine operates at less than 10% efficiency, consuming excess diesel fuel, generating emissions, and accelerating engine wear. One promising alternative is the use of small auxiliary power units (APUs), particularly fuel cell-based APUs. The Institute of Transportation Studies (ITS-Davis) developed an ADVanced VehIcle SimulatOR (ADVISOR)-based model to quantify the costs and benefits of truck fuel cell APUs. Differences in accessories, power electronics, and control strategy between the conventional engine idling and APUequipped systems are analyzed and incorporated into the model.

Recently public agencies have been promulgating idling bans in an effort to mitigate the environmental effects of heavy-duty truck idling. In order to make rational choices, regulators, manufacturers, and consumers will need to compare idling reduction strategies, such as truck stop electrification and auxiliary power units. Truck driver behaviors, such as idling time, idling location, and accessory use will significantly influence the cost-effectiveness of the various technology options. Truck driver attitudes toward idling and idling alternatives will influence adoption of the technologies. A pilot survey of 233 line-haul truck drivers was administered in Northern California as the first step in assessing truck driver behaviors and attitudes related to idling. Initial findings reveal that line-haul truck drivers idle primarily to power climate control.

In the last five years, there have been multiple demonstrations of fuel cell auxiliary power units (APUs) which provide power in lieu of idling of the main vehicle engine. The Institute of Transportation Studies at the University of California Davis has designed and evaluated a retrofitted, proton exchange membrane (PEM) fuel cell APU for powering accessories in heavy-duty truck cabs. The performance objectives for the system were determined based on truck driver feedback and industry design guidelines. The final FC APU system was developed to run for 3 days between refueling at a power output of 1.8 kW. The primary goals were to utilize exclusively commercially available components and to minimize costs. This paper discusses the performance targets, design tradeoffs, and evaluation of the developed system.