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Biology is a good source of analogies for engineering design. One approach of retrieving biological analogies is to perform keyword searches on natural-language sources such as books, journals, etc. A challenge in retrieving information from natural-language sources is the potential requirement to process a large number of search results. This thesis describes two methods on improving the relevancy of the search results. The first method is inserting metadata such as part- of-speech, word sense and lexicographical data for each word in a natural-language. The second method is categorizing the search results, using WordNet relationships and Wikipedia structures as ontologies. Although this research is still exploratory, initial qualitative observations demonstrate successful identification and separation of biological phenomena relevant to either desired functions or desired qualities. The benefits of embedding metadata are demonstrated through a case study on the redesign of a fuel cell bipolar plate. A prototype was constructed with ability to passively prevent prolonged catastrophic flooding.

Biology is a good source of analogies for engineering design. One approach of retrieving biological analogies is to perform keyword searches on natural-language sources such as books, journals, etc. A challenge in retrieving information from natural-language sources is the potential requirement to process a large number of search results. This thesis describes two methods on improving the relevancy of the search results. The first method is inserting metadata such as part- of-speech, word sense and lexicographical data for each word in a natural-language. The second method is categorizing the search results, using WordNet relationships and Wikipedia structures as ontologies. Although this research is still exploratory, initial qualitative observations demonstrate successful identification and separation of biological phenomena relevant to either desired functions or desired qualities. The benefits of embedding metadata are demonstrated through a case study on the redesign of a fuel cell bipolar plate. A prototype was constructed with ability to passively prevent prolonged catastrophic flooding.

Fuel cell, as an alternative green power source for automobiles and portable electronics, has attracted worldwide attention due to its desirable properties such as high energy density and low greenhouse gas emission. Despite great progress in the past decades, several challenges still remain as obstacles for the large-scale commercialization. Among them, the high cost of Pt-based electrode material is considered as a major barrier, while the life span or stability of electrode catalysts is another concern since the electrocatalysts can be easily poisoned during the fuel cell operation. In order to overcome these issues, nanostructured carbon materials, especially carbon nanotubes (CNTs), are studied as catalyst support. In addition, recent research also suggests that the coupling of a second metal element with Pt can effectively protect the electrocatalysts from being poisoned and thus improve their long-term durability. The objective of the present work was to demonstrate an efficient synthetic method for the preparation of CNTs supported binary PtM (M=Ru, Sn) electrocatalysts. In this project, a polymer wrapping technique along with an in-situ polyol reduction strategy was adopted to decorate well-dispersed binary PtM nanoparticles on the surface of modified-CNTs. The unique nanostructures as well as the excellent catalytic activities of the as-prepared nanohybirds were investigated through a diversity of physiochemical and electrochemical characterization techniques. This fabrication method provided a simple and convenient route to assemble Pt-based catalyst on carbon substrates, which is useful for the further development of high-performance fuel cell catalysts.

Rapidly rising fossil fuel costs along with increased environmental awareness has encouraged the development of alternative energy sources. Such sources include fuel cells, wind, solar and ocean tide power. Among them, fuel cells have received increased interest in the recent years. This is mainly due to their high efficiency, modularity, and simple construction. However, due to their low output voltage and wide variation from no load to full load, a power electronics converter is required to interface the fuel cell with its loads. This dissertation focuses on developing a set of considerations that will assist designers of the power electronics converter in the design and optimization of the system. These design considerations are obtained analytically and verified experimentally and allow obtaining an efficient and stable fuel cell – power converter system. In addition to the design guidelines this dissertation presents new power converter topologies that do not require the use of transformers to achieve a large voltage gain. Further a new modular fuel cell power converter system that divides the fuel cell stack to optimize power generation is proposed. It is shown by means of mathematical analysis and experimental prototypes that the proposed solutions contribute to the reduction of size and cost of the power converter as well to increase the efficiency of the system.

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The application of a decomposition methodology to the synthesis/design optimization of a stationary cogeneration fuel cell sub-system for residential/commercial applications is the focus of this work. To accomplish this, a number of different configurations for the fuel cell sub-system are presented and discussed. The most promising candidate configuration, which combines features of different configurations found in the literature, is chosen for detailed thermodynamic, geometric, and economic modeling both at design and off-design. The case is then made for the usefulness and need of decomposition in large-scale optimization. The types of decomposition strategies considered are time and physical decomposition. Specific solution approaches to the latter, namely Local-Global Optimization (LGO) and Iterative Local-Global Optimization (ILGO) are outlined in the thesis. Time decomposition and physical decomposition using the LGO approach are applied to the fuel cell sub-system. These techniques prove to be useful tools for simplifying the overall synthesis/design optimization problem of the fuel cell sub-system. Finally, the results of the decomposed synthesis/design optimization of the fuel cell subsystem indicate that this sub-system is more economical for a relatively large cluster of residences (i.e. 50). To achieve a unit cost of power production of less than 10 cents/kWh on an exergy basis requires the manufacture of more than 1500 fuel cell sub-system units per year. In addition, based on the off-design optimization results, the fuel cell subsystem is unable by itself to satisfy the winter heat demands. Thus, the case is made for integrating the fuel cell sub-system with another sub-system, namely, a heat pump. / Master of Science

Magister Scientiae - MSc (Chemistry) / The anode catalyst is one of the important parts of the direct alcohol fuel cell (DAFC); it is responsible for the alcohol oxidation reaction (AOR) takes place at the anode side. Pd has been reported to have good alcohol oxidation reactions and good stability in alkaline solution. Better stability and activity has been reported for Pd alloyed catalysts when compared to Pd. Choosing a suitable alcohol also has an effect on the activity and stability of the catalyst. This study investigates the best catalyst with better AOR and the best stability and also looks at the better alcohol to use between glycerol and ethanol for the five in-house catalysts (20% Pd, PdNi, PdNiO, PdMn3O4 and PdMn3O4NiO on multi walled carbon nanotubes) using cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectrometry (EIS) and chronoamperometry. HR-TEM and XRD techniques were used to determine the particle size and average particle size, respectively while EDS used to determine elemental composition and ICP was used to determine catalyst loading. It was observed from LSV that PdNiO was the most active catalyst for both ethanol and glycerol oxidation, and it was the most stable in ethanol while PdMn3O4 proved to be the most stable catalyst in glycerol observed using chronoamperometry. The best alcohol in this study was reported to be glycerol having given the highest current densities for all the inhouse catalysts compared to ethanol observed using LSV. From XRD and HR-TEM studies, particle sizes were in the range of 0.97 and 2.69 nm for XRD 3.44 and 7.20 nm for HR-TEM with a little agglomeration for PdMn3O4 and PdMn3O4NiO.

The direct methanol fuel cell (DMFC) is a very promisingpower source for low power applications. High power and energydensity, low emissions, operation at or near ambientconditions, fast and convenient refuelling and a potentiallyrenewable fuel source are some of the features that makes thefuel cell very promising. However, there are a few problemsthat have to be overcome if we are to see DMFCs in our everydaylife. One of the drawbacks is the low performance of the DMFCanode. In order to make a better anode, knowledge about whatlimits the performance is of vital importance. With theknowledge about the limitations of the anode, the flow field,gas diffusion layer and the morphology of the electrode can bemodified for optimum performance. The aim of this thesis is to elucidate the limiting factorsof the DMFC anode. A secondary goal is to create a model of theperformance, which also has a low computational cost so that itcan be used as a sub model in more complex system models. Toreach the primary goal, to elucidate the limiting factors, amodel has to be set up that describes the most importantphysical principles occurring in the anode. In addition, experiments have to be performed to validatethe model. To reach the secondary goal, the model has to bereduced to a minimum. A visual DMFC has been developed alongwith a methodology to extract two-phase data. This has provento be a very important part of the understanding of thelimiting factors. Models have been developed from a detailedmodel of the active layer to a two-phase model including theentire three-dimensional anode. The results in the thesis show that the microstructure inthe active layer does not limit the performance. Thelimitations are rather caused by the slow oxidation kineticsand, at concentrations lower than 2 M of methanol, the masstransport resistance to and inside the active layer. Theresults also show that the mass transfer of methanol to theactive layer is improved if gas phase is present, especiallyfor higher temperatures since the gas phase then contains moremethanol. It is concluded that the mass transport resistance lower theperformance of a porous DMFC anode at the methanolconcentrations used today. It is also concluded that masstransfer may be improved by making sure that there is gas phasepresent, which can be done by choosing flow distributor and gasdiffusion layer well. Keywords: direct methanol fuel cell, fuel cell, DMFC, anode,model

Planar £gPEM Fuel Cell Stacks are designed and fabricated in-house through a deep UV lithography technique, with SU 8 photoresist used as the microstructure mold for the fuel cell flow channel or bipolar plates when micro electroforming. The fuel cell stacks use a new design which means installing the fuel channel into PMMA, by which the fuel supply channel becomes convenient and simplified. The performance of the stack is measured in different inlets, and the effect of the hydrogen inlets is explained. The experimental results are presented in the form of polarization VI curves and PI curves for the different types of inlet. Furthermore, the influence of the inlets is presented and discussed.