Browsing by Author "Bubna, Piyush"
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Item Design, Operation, Control, and Economics of a Photovoltaic/Fuel Cell/Battery Hybrid Renewable Energy System for Automotive Applications(MDPI AG, 2015-06-09) Whiteman, Zachary S.; Bubna, Piyush; Prasad, Ajay K.; Ogunnaike, Babatunde A.; Zachary S. Whiteman, Piyush Bubna, Ajay K. Prasad and Babatunde A. Ogunnaike; Whiteman, Zachary S.; Bubna, Piyush; Prasad, Ajay K.; Ogunnaike, Babatunde A.Meeting rapidly growing global energy demand—without producing greenhouse gases or further diminishing the availability of non-renewable resources—requires the development of affordable low-emission renewable energy systems. Here, we develop a hybrid renewable energy system (HRES) for automotive applications—specifically, a roof-installed photovoltaic (PV) array combined with a PEM fuel cell/NiCd battery bus currently operating shuttle routes on the University of Delaware campus. The system’s overall operating objectives—meeting the total power demand of the bus and maintaining the desired state of charge (SOC) of the NiCd battery—are achieved with appropriately designed controllers: a logic-based “algebraic controller” and a standard PI controller. The design, implementation, and performance of the hybrid system are demonstrated via simulation of real shuttle runs under various operating conditions. The results show that both control strategies perform equally well in enabling the HRES to meet its objectives under typical operating conditions, and under sudden cloud cover conditions; however, at consistently high bus speeds, battery SOC maintenance is better, and the system consumes less hydrogen, with PI control. An economic analysis of the PV investment necessary to realize the HRES design objectives indicates a return on investment of approximately 30% (a slight, but nonetheless positive, ~$550 profit over the bus lifetime) in Newark, DE, establishing the economic viability of the proposed addition of a PV array to the existing University of Delaware fuel cell/battery bus.Item Modeling, simulation and optimization of fuel cell/battery hybrid powertrains(University of Delaware, 2010) Bubna, PiyushFuel cells have emerged as one of the most promising candidates for fuel-efficient and emission-free vehicle power generation. Fuel cells are typically paired with reversible energy storage devices such as batteries or ultracapacitors to create hybrid electric powertrains. The electrification of the propulsion system and the presence of multiple onboard power sources require optimization of the hybrid system design in order to achieve good performance, high fuel economy, and enhanced component life at low cost. The overall goal of this research is to develop accurate vehicle models and conduct simulations to explore and demonstrate improvements in a fuel cell/battery hybrid bus. The first part of this thesis presents the features incorporated to improve a hybrid powertrain simulation package called Light, Fast and Modifiable (LFM). The improved LFM simulator was validated against test data acquired from various sensors onboard UD’s Phase 1 fuel cell bus, and shown to be a reliable tool to simulate hybrid powertrain performance which could be used to perform design and optimization studies of future fuel cell hybrid systems. This attribute of LFM was then demonstrated by optimizing the fuel cell/battery hybrid power management by introducing a new prediction-based power management strategy. Simulation results for this strategy showed significant improvements in fuel cell system efficiency and reduction in hydrogen consumption compared to a conventional, baseline strategy of charge sustenance. A stable power request which promotes fuel cell durability was also realized with the help of this novel strategy. Finally, the benefits predicted from simulation studies were confirmed through implementation of the proposed strategy in the Phase 1 fuel cell/battery hybrid bus. It was concluded that the prediction-based strategy will lead to energy savings for transit applications. The validated LFM tool was next used to evaluate one approach to reducing battery stress by adding an ultracapacitor module, and thereby enhancing battery lifetime. Simulation of the energy storage performance showed a substantial reduction in battery current-load and energy throughput for the blended storage system, which are two of the contributing factors towards battery degradation. These results have opened up new research directions in which powertrain simulations can help in further evaluation of the blended storage concept and assess its feasibility and usefulness in electric-drive vehicles. Finally, the thermal behavior of the Altairnano LiTi battery, the future battery of UD fuel cell buses, was investigated. Preliminary experiments were conducted to understand the thermal behavior of batteries under typical operating conditions. A model was developed to predict the temperature during charging and discharging of the battery. The findings of this work should prove useful in designing effective and efficient battery thermal management systems.