Evaluation of power-assist hydraulic and electric hybrids for medium- and heavy-duty vehicle applications
Date
2014
Authors
Wagner, Justin Taylor, author
Bradley, Thomas H., advisor
Bandhauer, Todd M., committee member
Sega, Ronald M., committee member
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Abstract
Under pressure from rising fuel costs, emissions constraints, and new government regulations on medium- and heavy-duty vehicles, hybrid technologies for these classes of vehicles are becoming more prevalent. A variety of technologies have been proposed to meet these requirements including power-assist hybrid electric and hybrid hydraulic systems. Although there has been great discussion about the benefits surrounding each of the technologies individually, no direct comparisons are available on the basis of economics and fuel economy. This study focuses on comparing these power-assist technologies on these bases as well as determines the ability of these technologies to fulfill the newly adopted fuel economy regulations. In order to accomplish this goal, three computational models of vehicle dynamics, thermal behavior and fuel economy were created and validated to simulate the conventional vehicle and hydraulic and electric hybrids. These models were simulated over the Heavy-Duty Urban Dynamometer Driving Schedule, the HTUF Class 4 Parcel Delivery Cycle, and the Orange County Bus cycle. These drive cycles were chosen on their ability to characterize the variety of operating conditions observed in medium- and heavy-duty vehicles. Using these models, cross technology comparisons were constructed comparing commercially available systems, systems with a fixed mass, and systems with a fixed incremental cost. The results of the commercially available systems showed that the Azure Dynamics HEV provided greater fuel economy improvement than the Lightning Hybrids HHV for drive cycle kinetic intensities less than 3.19 miles-1. Although this system showed a cost of fuel savings over the HHV, it was seen that the incremental cost of the HEV exceeded the cost of fuel savings over the HHV. The fixed mass comparison case, which compared vehicles with equal cargo carrying utility, showed similar results to that of the commercially available case. Although the increase in incremental cost for the varying HEV systems designed for the fixed mass case correlated to an improvement in fuel savings, the cost associated with the systems surpassed the savings seen. Lastly, the fixed cost case provided results which were also similar to the commercially available case. Due to the fixed system cost, it was seen that for these systems, the fuel economy benefits and associated cost showed the greatest benefits for the HEV. This study concluded that given the evaluation, the HEV was the only power-assist hybrid technology which could fulfill the regulated fuel economy improvement of 15%. Although the HEV was the only technology which could fulfill the requirements, the HHV showed an improvement upwards of 7% greater than the HEV for the Orange County Bus Drive Cycle.
Description
Rights Access
Subject
electric
medium-duty
hydraulic
hybrid
heavy-duty