Ever increasing demand for the petroleum is causing faster than expected oil shortages in the supply and demand balance around the world and furthermore, many specialists in the field of oil production such as Association for the Study of Peak Oil and World Energy Outlook are claiming that the petroleum is around the peak of its production ( Figure 1). Such shortage made the greatest impact on the gasoline price hikes at the gas pump and thus, this impact was felt by the consumers severely and became the greatest motivation for automotive industries to strive to pioneer the researches for the next generation vehicle configurations ranging from HEV, PHEV, Pure EV to FCHEV (collectively noted as xEV). While the great deal of researches has been carried over the last few decades, it is still far from mass productions for consumer use except for the HEV mainly due to the high cost involved with other types of xEV configurations. Therefore, it is critical to design the vehicle to maximize the use of each component at its highest point regardless of any cost scenarios and it is clear that this optimization can only be achieved through the accurate energy balance simulation for a specific target vehicle prior to the actual hardware implementation. In this paper, it is our intention to introduce modified dynamic battery modeling scheme that would provide a more accurate way of simulating the battery behavior when used in the vehicle energy simulation system. Starting from a typical battery dynamic model to predict the voltage given an imposed current request, we have introduced a new scheme to establish the relationship between the voltage and the power (rather than the current) requested by the vehicle simulation system. The proposed scheme handles the power request from the vehicle simulator considering the dynamic battery characteristics and in turn, contributes to the better estimation of the current integrated energy usage and battery SOC level in the given battery dynamic system used in the vehicle energy simulation system.
Due to sharply increasing oil price, tremendous efforts are being made to reduce the dependencies on the petroleum based fuels in the field of automotive power trains. As one of the promising alternatives, fuel cell hybrid system has been studied for many different vehicle types from SUV to low speed vehicle. To establish systematic ways to achieve the optimized system configuration, in this paper, we introduce a methodology which combines energy analysis over typical drive cycles with a parametric sizing study for the various powertrain components as well as supervisory energy management parameters. For a practical and demonstrative implementation of the suggested methodology with a limited resource available at hand, a Neighborhood Electric Vehicle (NEV) for urban transportation is considered for a detailed analysis, design and optimization. Two major supervisory control strategies, namely, charge-sustaining and charge-depleting are carefully investigated to illustrate the versatility of our proposed methodology. Our study shows that the systems could be modeled and optimized either in a charge sustaining case or in a charge depleting case (plug-in hybrid electric vehicle) to meet vehicle purposes and usages, respectively. Not only because of the usage of the FC power system as a range extender for an EV, but also the possibility of using the plug-in configuration with renewable energy generation systems, as a personal eco-system, the proposed plug-in FC-NEV may be a solution for a local urban transportation system in this demanding era of sustainable mobility.
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