Industry and researchers are investigating both battery electric vehicles (BEVs) and fuel cell hybrid vehicles (FCHV) for the future of sustainable passenger vehicle technology. While BEVs have clear efficiency advantages, FCHVs have key benefits in terms of refueling time and energy density. This thesis first proposes the concept of a fuel cell range extended vehicle (FCREV) that uses Whole-Day Driving Prediction (WDDP) control, which uses driver destination inputs to determine whether the planned driving trips that day will exceed the useable battery energy capacity. If so, the fuel cell is turned on at the start of the day. The benefit of WDDP control is that a smaller, lower cost fuel cell can be used to greatly extend the driving range, since the fuel cell can charge the battery during both driving and parked periods of the day. Furthermore, this research proposes a fast analytical optimization algorithm for designing a WDDP-FCREV to maximize range on a given drive cycle for a set cost. The results show an optimized WDDP-FCREV can greatly exceed the range of a same-cost BEV, by 105% to 150% for no H2 refueling and by 150% to 250% when H2 refueling is allowed every 4 hours. / Thesis / Master of Applied Science (MASc)

The largest cost in manufacturing PEM fuel cells for automotive applications is due to the bipolar plate. The current graphite material used for the bipolar plate is very brittle and difficult to machine to the rigorous specifications needed for fuel cell stacks. This paper introduces the development of a fuel cell test stand for simultaneous testing of six individual fuel cells. To establish a long-term performance evaluation, the fuel cells incorporate a baseline graphite material that undergoes testing in the fuel cell environment. The graphite is an industry standard material that should not corrode when subjected to continual testing. The baseline model will be used in development of novel composite materials that will be tested under the same conditions for comparison to the graphite. Furthermore, the new materials and applied manufacturing methods could reduce the overall cost of fuel cell stacks in the future. Funding for this project was generously donated by the Virginia Center for Innovative Technology and the National Science Foundation. / Master of Science

Solid oxide fuel cells (SOFCs) represent a much cleaner and more efficient method for harnessing fossil fuel energy than conventional combustion; however, the challenge with making SOFCs mainstream lies in reducing operating costs and staving off their rapid degradation. High cathode polarization remains a bottleneck for lowering operation temperature. On the anode side, supplying SOFCs with hydrocarbon-based fuels poses many problems for systems using state-of-the-art material specifications such as composites of Ni and yttria-stabilized zirconia (YSZ). Various novel materials and surface modifications have been found to mitigate these problems, but more information towards a more profound understanding the role of these materials is desired. In this work, advanced Raman spectroscopic techniques were applied toward this end. Raman spectroscopy was used for the tracking of the evolution of water, carbon, sulfur, and oxygen species as well as new phases at SOFC electrode surfaces following or during exposure to various temperatures, atmospheres, and electrochemical stimuli. This information, coupled with performance data and other characterizations, would help to clarify the mechanisms of anode contamination reactions and oxygen reduction reactions. Knowledge gained from this work would also help to connect electrode modifications with performance enhancement and poisoning tolerance, offering insights vital to design of better electrodes. In addition, lack of adequate Raman signal from certain species, which is one of Raman spectroscopy’s limitations, was addressed. Surface enhanced Raman scattering (SERS) techniques were used in both in situ and ex situ analyses to increase signal yield from gas species and phases that are found only in trace amounts on electrode surfaces. Finally, a more practical thrust of this work was the application of this study methodology and the knowledge gained from it to cells with NASA's bielectrode supported cell (BSC) architecture. These types of cells also offer great prospects for superior specific power density due to their low weight. Ultimately, the goal of this thrust was progress towards achieving optimum performance of SOFCs operating under hydrocarbon fuels.

Proton exchange membrane fuel cells (PEMFC) and direct methanol fuel cells (DMFC) are attractive power sources as they offer high conversion efficiencies with low or no pollution. However, the most commonly used platinum electrocatalyst is expensive and the world supply of Pt is limited. In addition, the slow oxygen reduction and methanol oxidation kinetics as well as the poisoning of the Pt catalyst at the cathode resulting from methanol permeation from the anode through the Nafion membrane to the cathode lead to significant performance loss. Also, the electrocatalyst utilization in the electrodes also needs to be improved to reduce the overall cost of the electrocatalysts and improve the fuel cell performance. This dissertation explores nanostructured Pt alloys with lower cost and higher catalytic activity than Pt for oxygen reduction in PEMFC to understand the effect of synthesis and structure on the catalytic activity, methanol tolerant Pt/TiOx nanocomposites for oxygen reduction in DMFC, nanostructured Pt-Ru alloys for methanol oxidation in DMFC, and improvement in the utilization of Pt by optimizing the membrane-electrode assembly (MEA) fabrication. From a systematic investigation of a series of Pt-M alloys (M = Fe, Co, Ni, and Cu), the catalytic activity of Pt-M alloys is correlated with the extent of atomic ordering. More ordered Pt alloys exhibit higher catalytic activity than disordered Pt alloys. The higher activity of the ordered Pt alloys is found to relate to various factors including the Pt-Pt distance, Pt: 5d orbital vacancy, {100} planar density and surface atomic configuration. The catalytic activity of the Pt alloys is also influenced by the synthesis method. Low temperature solution methods usually result in smaller particle size and higher surface area, while high temperature routes result in larger particle size and lower surface area but with a greater extent of alloying. Pt/TiOx/C nanocomposites exhibit higher performance than Pt for oxygen reduction in DMFC. The nanocomposites show higher electrchochemical surface area, lower charge transfer resistance, and higher methanol tolerance than Pt. Pt-Ru alloy synthesized by a reverse microemulsion method exhibits higher catalytic surface area than the commercial Pt-Ru. The higher catalytic activity is attributed to a better control of the particle size, crystallinity, and microstructure. Membrane-electrode assemblies (MEAs) fabricated by a modified thin film method exhibit much higher electrocatalyst utilization efficiency and performance than the conventional MEAs in PEMFC. Power densities of 715 and 610 mW/cm2 are obtained at a Pt loading of, respectively, 0.1 and 0.05 mg/cm2 and 90 oC. The higher electrocatalyst utilization is attributed to the thin catalyst layer and a better continuity of the membrane/catalysts layer interface compared to that in the conventional MEAs. / text

Thesis (M. Tech. Engineering: Electrical--Vaal University of Technology) / The air-breathing Direct Methanol Fuel Cell (DMFC) and Zinc Air Fuel Cell (ZAFC)were experimentally studied in a climate chamber in order to investigate the impact of climatic environmental parameters such as varying temperature and relative humidity conditions on their performance. The experimental results presented in the form of polarization curves and discharge characteristic curves indicated that these parameters have a significant effect on the performance of these fuel cells. The results showed that temperature levels below 0ºc are not suitable for the operation of these fuel cells. Instead, it was found that air-breathing DMFC is favored by high temperature conditions while both positive and negative effects were noticed for the air-breathing ZAFC. The results of the varying humidity conditions showed a negative impact on the air-breathing DMFC at a lower temperature level but a performance increase was noticed at a higher temperature level. For air-breathing ZAFC, the effect of humidity on the performance was also found to be influence by the operating temperature. Furthermore, common atmospheric air pollutants such as N20, S02, CO and N02 were experimentally investigated on the air-breathing DMFC and ZAFC. At the concentration of 20 ppm, these air contaminants showed to have a negative effect on the performance of both air-breathing DMFC and ZAFC. For both air-breathing DMFC and ZAFC, performance degradations were found to be irreversible. It is therefore evident from this research that the performance of the air-breathing fuel cell will be affected in an application situated in a highly air-polluted area such as Vaal Triangle or Southern Durban. It is recommended the air-breathing fuel cell design include air filters to counter the day-to-day variations in concentration of air pollutants.

M. Tech. (Engineering: Electrical, Department Electronic Engineering, Faculty of Engineering and Technology), Vaal University of Technology, / “If we think oil is a problem now, just wait 20 years. It’ll be a nightmare.” — Jeremy Rifkin, Foundation of Economic Trends, Washington, D.C., August 2003. This statement harmonises with the reality that human civilisation faces today. As a result, humankind has been forced to look for alternatives to fossil fuels. Among possible solutions, fuel cell (FC) technology has received a lot of attention because of its potential to generate clean energy. Fuel cells have the advantage that they can be used in remote telecommunication sites with no grid connectivity as the majority of telecommunication equipment operates from a DC voltage supply. Power plants based on phosphoric acid fuel cell (PAFC) have been installed worldwide supplying urban areas, shopping centres and medical facilities with electricity, heat and hot water. Although these are facts regarding large scale power plants for on-site use, portable units have been explored as well. Like any other fuel cell, the PAFC output power is highly unregulated leading to a drastic drop in the output voltage with changing load value. Therefore, various DC–DC converter topologies with a wide range of input voltages can be used to regulate the fuel cell voltage to a required DC load. An interleaved synchronous buck converter intended for efficiently stepping down the energy generated by a PAFC was designed and developed. The design is based on the National Semiconductor LM5119 IC. A LM5119 evaluation board was redesigned to meet the requirements for the application. The measurements were performed and it was found that the converter achieved the expectations. The results showed that the converter efficiently stepped down a wide range of input voltages (22 to 46 V) to a regulated 13.8 V while achieving a 93 percent efficiency. The conclusions reached and recommendations for future research are presented. / Telkom Centre of Excellence, TFMC, M-Tech, THRIP.

The incorporation of an ejector refrigeration cycle with a high temperature PEM fuel cell (HT-PEMFC) presents a novel approach to combined heat and power (CHP) applications. An ejector refrigeration system (ERS) can enhance the flexibility of a CHP system by providing an additional means of utilizing the fuel cell waste heat besides domestic hot water (DHW) heating. This study looks into the performance gains that can be attained by incorporating ejector refrigeration with HT-PEMFC micro-CHP (mCHP) systems (1 to 5kWe). The effectiveness of the ERS in utilizing fuel cell waste heat is studied as is the relulting enhancement to overall system efficiency. A test rig specially constructed to evaluate an ERS under simulated HT-PEMFC conditions is used to test the concept and verify modeling predictions. In addition, two separate analytical models were constructed to simulate the ERS test rig and a HT-PEMFC/ERS mCHP system. The ERS test rig was simulated using a Matlab based model, while two residential sized HT-PEMFC/ERS mCHP systems were simulated using a Simulink model. Using U.S. Energy Information Administration (EIA) air conditioning and DHW load profiles, as well as data collected from a large residential monitoring study in Florida, the Simulink model provides the results in system efficiency gain associated with supporting residential space cooling and water heating loads. It was found that incorporation of an ERS increased the efficiency of a HT-PEMFC mCHP system by 8 t0 10 percentage points over just using the fuel cell waste heat for DHW. In addition, results from the Matlab ERS test rig model were shown to match well with experimental results. / by Michel Fuchs. / Thesis (Ph.D.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

Pulsing the flow of reactants in proton exchange membrane fuel cells (PEMFC) is a new frontier in the area of fuel cell research. Although power performance losses resulting from water accumulation also referred to as flooding, and power performance recovery resulting from water removal or purging, have been studied and monitored, the nexus between pulsing of reactants and power performance has yet to be established. This study introduces pulsing of reactants as a method of improving power performance. This study investigates how under continuous supply of reactants, pressure increase due to water accumulation, and power performance decay in PEMFCs. Furthermore, this study shows that power performance can be optimized through pulsing of reactants, and it investigates several variables affecting the power production under these conditions. Specifically, changes in frequency, duty cycle, and shifting of reactants as they affect performance are monitored and analyzed. Advanced data acquisition and control software allow multi-input monitoring of thermo-fluid and electrical data, while analog and digital controllers make it possible to implement optimization techniques for both discrete and continuous modes. / by Aquiles Perez. / Thesis (Ph.D.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

Proton exchange membrane (PEM) fuel cells are one of the most promising clean energy technologies under development. The major advantages include electrical efficiencies of up to 55 %, high energy densities (relative to batteries), and low emissions. However, the main obstacles to commercialization of PEM fuel cells are related to the limitations of the proton conducting solid polymer electrolytes such as Nafion. These membranes are expensive, mechanically unfavorable at higher temperatures, and conduct protons only in the presence of water, which limits the fuel cell operating temperature to about 80 C. This in turn, results in low fuel cell performance due to slow electrode kinetics and virtually no CO tolerance. The potential operation of PEM fuel cells at higher temperature (above 100 C) can provide many advantages such as improved kinetics at the surface of electrode, which is especially important in methanol and CO-containing reformate feeds, and efficient heat rejection and water management. Another issue above 100 C is the reduction of electrochemical surface area of the electrodes due to shrinkage of electrolyte (Nafion phase) within the catalyst layers. This research work is thus focused on the development of nanocomposite proton exchange membranes (NCPEMs) which are chemically and mechanically more stable at higher temperatures and electrodes which can result into better fuel cell performance. These are composite materials with inorganic acidic nanoparticles incorporated within a host polymer electrolyte membrane such as Nafion. The target operating fuel cell temperature in this work is above 100 oC with relative humidity around 30 to 40 %. To achieve these targets, both theoretical and experimental investigations were undertaken to systematically develop these NCPEMs. Various experimental techniques, namely, TEOM (Tapered Element Oscillating Microbalance), Impedance Spectroscopy, MEA (membrane electrode assembly) testing, Ion Exchange Capacity, Scanning Electron Microscope (SEM), Optical Electronic Holography (OEH), Thermal Gravimetric Analysis (TGA), and Dynamic Mechanical Analysis (DMA) were employed to characterize the NCPEMs. A thermodynamic model was developed to describe sorption in proton-exchange membranes (PEMs), which can predict the complete sorption isotherm. A comprehensive proton transport model was also developed to describe proton diffusion in Nafion/(ZrO2/SO42-) nanocomposite membranes. The conductivity of the in situ sol-gel prepared Nafion/ (ZrO2/SO42-) nanocomposite membranes was accurately predicted by the model as a function of relative humidity (RH) without any fitted parameters. This transport model developed offers a theoretical framework for understanding the proton transfer in nanocomposite membranes and is an insightful guide in systematically developing high proton-conducting nanocomposite. Nafion-MO2(M = Zr, Si, Ti) nanocomposite membranes were synthesized with the goal to increase the proton conductivity and water retention by the membrane at higher temperatures and lower relative humidity (120 C, 40% RH) and also to improve the thermo-mechanical properties. The results obtained are promising and indicate that this is a potentially useful approach for developing PEMs with desirable properties. Finally, commercially available high temperature PBI (polybenzimidazole)-H3PO4 (phosphoric acid) gel membrane fuel cell was investigated in the temperature range of 160-180 C. This system exhibited very good and stable performance in this temperature range.

Solid oxide fuel cell platforms consisting of alternating cellular layers of yttria-stabilized zirconia electrolyte and Fe-Ni metallic interconnects (Fe45Ni, Fe47.5Ni, Fe50Ni) were produced through the co-extrusion of two particulate pastes. Subsequent thermal treatment in a hydrogen atmosphere was used to reduce iron and nickel oxides and co-sinter the entire structure. Issues surrounding this process include the constrained sintering of the layers and the evolution of residual stress between the dense, fired layers. Sintering curves for individual components of the layers were measured by dilatometry to ascertain each materials impact on overall sintering mismatch. X-ray diffraction, scanning electron microscopy and weight loss were utilized to examine phase evolution within the Fe-Ni alloys during reduction. YSZ powders densified above ~1050C and shrinkage was rapid above the sintering temperature. Shrinkage of the interconnect occurred in two stages: reduction and the initial stages of sintering concluded around ~600C, plateauing shortly and continuing at ~900C as pore removal and grain growth ensued simultaneously. Constrained sintering resulted in the formation of remnant porosity within the interconnect layers. Interconnect compositions were chosen in efforts to minimize disparities in thermal expansion with the electrolyte. Residual strains on the surfaces of the layers were measured by x-ray diffraction. Corresponding stresses were calculated using the sin2y method. Grain growth within the interconnect prohibited random planes to be measured so stress measurements were confined to the ceramic layers. Various material properties such as thermal expansion were collected and employed in a modified finite element model to estimate residual stresses in the platform. A method for determining a crucial parameter, the zero stress temperature was outlined and incorporated. Modeled values were found to agree well with XRD values, providing indirect confirmation of the zero stress temperature calculations. Discrepancies were attributed to microcracks found within the layer that arose due to residual stress values surpassing the tensile strength of the zirconia.