Polymer electrolyte membrane (PEM) fuel cells are a promising zero-emission power source for transportation applications. An important tool for advancing PEM fuel cell technology is mathematical modeling. Mathematical models can be used to provide insight on the physical phenomena occurring within a fuel cell, as well as aid in the design of fuel cells by simulating the effect of changes in design or operating conditions on performance. A comprehensive, consistent and systematic general formulation for a mathematical PEM fuel cell model is presented in this thesis. The formulation is developed by considering the fuel cell to be composed of several, co-existing phases. The conservation of mass, momentum, species, and energy are applied to each phase in the fuel cell. The interactions between the phases are modeled by applying a volume-averaging procedure to the conservation equations in each phase. The solution of the governing equations for the general formulation are beyond the scope of this thesis research. Instead, simplifying assumptions are applied to the general formulation in order to reduce the number of governing equations. The cell is assumed to be two-dimensional, steady state and isothermal. As well, the polymer electrolyte is assumed to be impervious to the gas phase and liquid water is assumed to exist only in the gas phase or polymer electrolyte. The numerical solution of the simplified formulation is implemented using the computer language of C++ and the finite volume method. The numerical solution provides details of the transport phenomena within the anode and cathode gas flow channels, electrode backing layers, and catalyst layers, as well as the polymer electrolyte membrane layer. These details include the bulk velocity of the gas phase; the concentrations of the species within the gas phase; the potential and current density in the solid phase and polymer electrolyte; the water content in the polymer electrolyte; and the distribution of reaction rate within the catalyst layers.

The ‘Hydrogen Economy’ is a proposed system where hydrogen is produced from carbon dioxide free energy sources and is used as an alternative transportation fuel. The application of hydrogen on board fuel cell vehicles can significantly decrease air pollutants and greenhouse gases emission from the transportation sector. There must be significant transition of infrastructure in order to achieve the hydrogen economy with the investment required in both production and distribution infrastructure. This research focused on the projected demands for infrastructure transition of ‘Hydrogen Economy’ in Ontario, Canada. Three potential hydrogen demand and distribution system development scenarios were examined to estimate hydrogen fuel cell vehicle market penetration, as well as the associated hydrogen production and distribution. Demand of transportation hydrogen was estimated based on the type of hydrogen fuel cell vehicle. Upon the estimate of hydrogen demand from fuel cell vehicles in Ontario, the resulting costs of delivered hydrogen were investigated. In the longer term hydrogen is expected to be produced by utilizing nuclear heat and a thermochemical production cycle. A brief survey of thermochemical hydrogen production cycles was presented with a focus on S-I cycle. Sequential optimization models were developed to explore the minimum utility energy consumption and the minimum number of heat exchangers. Finally an optimal heat exchanger network for S-I thermochemical cycle was defined by a mixed integer optimization model using GAMS.

The dynamic performance of polymer electrolyte membrane fuel cells (PEMFCs) is of great interest for mobile applications such as in automobiles. However, the length scale of a PEM fuel cell's main components are ranging from the micro over the meso to the macro level, and the time scales of various transport processes range from milliseconds up to a few hours. This combination of various spatial and temporal scales makes it extremely challenging to conduct in-situ measurements or other observations through experimental means. Thus, numerical simulation becomes a very important tool to help understand the underlying electrochemical dynamics and transient transport phenomena within PEM fuel cells. In this thesis research, a comprehensive 3D model is developed which accounts for the following transient transport mechanisms: the non-equilibrium phase transfer between the liquid water and water vapor, the non-equilibrium membrane water sorption/desorption, liquid water transport in the porous backing layer, membrane hydration/dehydration, gas diffusion in the porous backing layer, the convective gas flow in the gas channel, and heat transfer. Furthermore, some of the conventionally used modeling assumptions and approaches have been incorporated into the current model. Depending on the modeling purposes, the resulting model can be readily switched between steady and unsteady, isothermal and non-isothermal, single- and multi- phases, equilibrium and non-equilibrium membrane sorption/desorption, and three water production assumptions. The governing equations which mathematically describe these transport processes, are discretized and solved using a finite-volume based commercial software, Fluent, with its user coding ability. To handle the significant non-linearity stemming from the multi-water phase transport, a set of numerical under-relaxation techniques is developed using the programming language C. The model is validated with experimental results and good agreements are achieved. Subsequently, using this validated model numerical studies have been carried out to probe various transient transport phenomena within PEM fuel cells and the cell dynamic responses with respect to different operating condition changes. Furthermore, the impact of flow-field design on the cell performance is also investigated with the three most common flow channel designs.

Polymer Electrolyte Membrane Fuel Cells (PEMFC) are promising power generating devices that use an electrochemical reaction to convert the energy from hydrogen fuel into usable electricity. One cell produces a small voltage so many cells are combined in series in order to produce a useful voltage, this configuration is referred to as a stack. Hydrogen is supplied to the anode of the stack in amounts greater than the electrochemical reaction requires to guarantee that enough hydrogen is available for every cell in the stack and to provide enough pressure throughout the cell flow channels for good mass transfer. For reasonable fuel efficiency, the anode outlet gas containing unconverted hydrogen is recycled (or recirculated) back to the anode inlet. PEMFC performance is highest when pure hydrogen fuel is supplied, however, nitrogen at the cathode will permeate through the membrane and accumulate in the anode gas with recirculation. Nitrogen buildup dilutes the hydrogen gas which adversely affects fuel cell performance at the anode. Also, in practical applications hydrogen-rich gas produced from reformed methane, called reformate, is used as the fuel. Reformate contains impurities such as, nitrogen, carbon dioxide, carbon monoxide, and sulfur compounds. This thesis will focus on trace levels of carbon monoxide entering in the hydrogen fuel stream, and the impact of contaminant build-up due to anode recirculation. Carbon monoxide adsorbs readily onto the platinum catalyst sites, called poisoning, thus decreasing PEMFC performance. In efforts to minimize the buildup of impurities and crossed over nitrogen, a portion of the anode outlet gas is periodically and continuously purged to the exhaust. How often the outlet gas is purged depends on a variable called the purge fraction. The purpose of this research is to study the effect of purge fraction on PEMFC performance, measured by the average cell voltage, for a Hydrogenics 10 cell stack. The operating parameters used for testing and the experimental apparatus were designed to mimic a Hydrogenics 8kW Hydrogen Fuel Cell Power Module. A pump connected between the anode outlet and anode inlet form the anode recirculation loop. In Phase 1 of the test program the effect of purge in the absence of carbon monoxide was studied to see if hydrogen dilution from nitrogen crossover and accumulation would cause significant cell voltage degradation. In Phase 2 the effect down to 0.2 ppm carbon monoxide was evaluated. The results showed that nitrogen buildup, in the absence of carbon monoxide, did not significantly penalize the cell performance in the range of purge fractions tested. However, for the same purge fraction but with as little as 0.2 ppm carbon monoxide present, the voltage loss was significant. A discussion of the effect of purge on the impurity concentration and the associated cell voltage degradation is detailed with particular emphasis on carbon monoxide poisoning.

Försvarets Materielverk (FMV) driver sedan 2003 ett bränslecellsprogram med syfte att öka Försvarsmaktens kunskap om bränslecellstekniken (FC-tekniken) och dess potential för framtida applikationer. Arbetet genomförs inom ramen för FM´s ”Dual Use”-program vars mål är att kartlägga potentiella strategiska teknologier för både civila och militära ändamål. En av slutsatserna som FMV drar är att bränsleceller inte nödvändigtvis är det självklara valet för alla studerade applikationer, men att tekniken visar på fördelar som strömförsörjningsfunktion för vissa tillämpningar. FC-tekniken har inneboende egenskaper vilka några innebär fördelar för såväl civila som militära tillämpningar. Särskilda fördelar relevant för militär verksamhet är att de har en låg ljudnivå och hög bränsledensitet vilket innebär potentiellt lägre upptäcktsrisk jämfört med förbränningssystem och betydligt längre drifttid jämfört med motsvarade vikt batterier. Vidare kan de konstrueras att vara bränsleflexibla och utformas för allt ifrån ren vätgas till diesel med hög svavelhalt. Frågan är nu vilka tillämpningar inom FM som faktiskt kan dra nytta av ett strömförsörjningssystem som möjliggör längre drifttid än batterier och samtidigt är tystare än en förbränningsmotor. Syftet med arbetet är att identifiera dessa tillämpningar inom FM där FC-teknikens inneboende egenskaper kan göra den till ett intressant strömförsörjningsalternativ samt precisera hur dessa system kan specificeras. Detta görs genom att svara på följande frågor: För vilka typer av tillämpningar inom FM har FC-tekniken konkurrensfördel? Hur skall specifikationerna för dessa bränslecellsystem formuleras? Uppgiften har lösts dels genom litteraturstudier av resultat och slutsatser av redan genomförda studier och dels genom att intervjua nyckelpersoner i relevanta positioner för de tänkta strömförsörjningssystemen. De tillämpningar som studeras och potentiellt kan ha konkurrensfördel gentemot förbränningssystem och/eller elektrokemisk lagring som t.ex. batterier är strömförsörjning av mobil och portabel utrustning, strömförsörjning av obemannade system, reservkraft, kombinerad kraft- och värmeproduktion (CHP) samt strömförsörjning av avlägsna enheter, dvs. enheter som inte har möjlighet att vara uppkopplade mot det ordinarie elnätet. Genom en utvärderingsprocess valdes två av dessa tillämpningar ut vilka ansågs vara speciellt intressanta att studera i mer detalj; ett mindre batteriladdningssystem på gruppnivå samt ett strömförsörjningssystem för en undervattensfarkost (AUV). Batteriladdningssystemet är avsett för förband som enskilt skall kunna lösa uppgifter i upp till tre veckor utan möjlighet till externt underhåll. Förband som har dessa uppgifter är specialförbanden, arméns jägarbataljon, underrättelsebataljonen samt amfibiekårens kustjägarkompani. Givet en generisk användargrupp, som anses kunna representera samtliga förband, kunde det maximala laddeffektbehovet uppskattas till drygt 80 W vid maximalt rekommenderad laddström. Om en längre laddtid kan accepteras kan dock effektbehovet minskas och likaså batteriladdningssystemets vikt och volym. Batteriladdningssystemet skall kunna hantera en rad olika typer och storlekar av batterier vilket ställer krav på både lämpliga fysiska gränsytor samt en funktion för ”smart laddning”, dvs. att systemet autonomt kan kontrollera hur det aktuella batteriet skall laddas. Då batteriladdningssystemet är avsett att användas i fältmiljö både nationellt och internationellt finns krav på funktion både i låga och höga temperaturer samt okänslighet mot både väta och sand. De kommersiellt idag tillgängliga systemen som potentiellt uppfyller kraven har en systemvikt på ca 12 kg. För den studerade AUV-applikationen gjordes beräkningar för tre olika strömförsörjningsfall; 1) Enbart batterier 2) Enbart ett bränslecellsystem och 3) Ett bränslecellsystem som hanterar baslasten och ett batteripack som hanterar topplasten. Av resultatet att döma finns i den studerade AUV-applikationen, med aktuell driftprofil, möjligen ett behov av hybridisering då denna lösning medför en 20 procentig ökning i drifttid. Mot detta skall ställas den ökade komplexiteten och kostnaden som detta kan medföra. Detta kan härledas till det faktum att topplasten inte skiljer sig markant mot baslasten samt att topplasten utnyttjas under mer än hälften av den totala drifttiden. I ett sådant fall verkar batteriets potentiellt högre förmåga att leverera hög effekt snabbt överskuggas av dess lägre energidensitet jämfört med bränslet. I kravet finns behov av att systemet under kort tid, < 1 min, skall kunna leverera cirka 10 kW då farkosten ”simmar” ut ur torpedtuben. Detta innebär givetvis att någon form av hybridisering är nödvändig. Exempelvis skulle en lösning kunna medge ett uttag av denna effekt under kort tid och som sedan under transitperioden har förmåga att ladda upp batteriet innan detta skall användas under den tid farkosten är fullt operativ. För att klargöra hur en sådan lösning kan utformas behövs detta krav analyseras mer i detalj. Eftersom effektbehovet i driftprofilen ökar relativt lite mellan bas- och topplast (1020 – 1290; +26 %) kommer skillnaden i massa och volym mellan två bränslecellsystem motsvarande bas- och topplast vara relativt liten. Ett något större system som kan hantera både bas- och topplast borde således inte medföra varken en betydligt större massa eller volym. Bränslecellsteknikens generellt höga verkningsgrad vid dellast medför också en hög verkningsgrad vid båda lastfallen. En fortsatt analys av denna lösning bör inriktas på att studera frågor som rör vilken typ av lagring som är lämplig för behovet av ett kortvarigt effektuttag, om denna lösning enbart skall hantera detta effektuttag eller om en större hybridisering av den typ som presenteras i Fall 3 är intressant. Utöver dessa resultat har tekniska specifikationer skrivits för respektive applikation. Dessa återfinns som bilagor. / The Swedish Defence Materiel Administration (FMV) has since 2003 been running a fuel cell programme with the purpose to increase the Armed Forces knowledge of fuel cell technology and its potential for future applications. This work has been performed as a part of the Armed Forces "Dual-Use"-programme which goal is to identify potential strategic technologies for both civilian and military purposes. Specific fuel cell technology advantages relevant to military activities are low acoustic and infra red signature and high fuel density which potentially means lower risk of detection compared to combustion systems and notably longer operating times in comparison to batteries. Furthermore, they can be constructed to be fuel flexible and be designed to handle everything from pure hydrogen to high sulphur diesel fuel. The question now is which applications in the Armed Forces that can actually benefit from a power supply system which allows for longer operating times than batteries yet is quieter than a combustion engine. The task has been solved partly by studies of the results and conclusions of already conducted reports and partly by interviewing key personnel in relevant positions for each of the proposed power supply systems. Two applications has been selected to be studied in more detail; a battery charging system and a power supply system for an Autonomous Underwater Vehicle (AUV).  The battery charging system is intended to meet the power supply demands of small ranger or reconnaissance units required to operate independently of other forces for up to three weeks.  The maximum power requirement was calculated to be approximately 90 W at the maximum recommended charge current the radio battery being normative. However, if a longer charge time is acceptable this power requirement could be reduced and along with it the system weight and volume.   For the AUV application three cases were formulated; 1) Only battery power 2) Only fuel cell power 3) Fuel cell power handles base load and battery power handles peak load. The results showed calculated operational times of 11, 20 and 24 hours respectively. In addition to these results, technical specifications have been produced for each application. These are included as attachments.

Polymer electrolyte membrane (PEM) fuel cells are a promising zero-emission power source for transportation applications. An important tool for advancing PEM fuel cell technology is mathematical modeling. Mathematical models can be used to provide insight on the physical phenomena occurring within a fuel cell, as well as aid in the design of fuel cells by simulating the effect of changes in design or operating conditions on performance. A comprehensive, consistent and systematic general formulation for a mathematical PEM fuel cell model is presented in this thesis. The formulation is developed by considering the fuel cell to be composed of several, co-existing phases. The conservation of mass, momentum, species, and energy are applied to each phase in the fuel cell. The interactions between the phases are modeled by applying a volume-averaging procedure to the conservation equations in each phase. The solution of the governing equations for the general formulation are beyond the scope of this thesis research. Instead, simplifying assumptions are applied to the general formulation in order to reduce the number of governing equations. The cell is assumed to be two-dimensional, steady state and isothermal. As well, the polymer electrolyte is assumed to be impervious to the gas phase and liquid water is assumed to exist only in the gas phase or polymer electrolyte. The numerical solution of the simplified formulation is implemented using the computer language of C++ and the finite volume method. The numerical solution provides details of the transport phenomena within the anode and cathode gas flow channels, electrode backing layers, and catalyst layers, as well as the polymer electrolyte membrane layer. These details include the bulk velocity of the gas phase; the concentrations of the species within the gas phase; the potential and current density in the solid phase and polymer electrolyte; the water content in the polymer electrolyte; and the distribution of reaction rate within the catalyst layers.

The ‘Hydrogen Economy’ is a proposed system where hydrogen is produced from carbon dioxide free energy sources and is used as an alternative transportation fuel. The application of hydrogen on board fuel cell vehicles can significantly decrease air pollutants and greenhouse gases emission from the transportation sector. There must be significant transition of infrastructure in order to achieve the hydrogen economy with the investment required in both production and distribution infrastructure. This research focused on the projected demands for infrastructure transition of ‘Hydrogen Economy’ in Ontario, Canada. Three potential hydrogen demand and distribution system development scenarios were examined to estimate hydrogen fuel cell vehicle market penetration, as well as the associated hydrogen production and distribution. Demand of transportation hydrogen was estimated based on the type of hydrogen fuel cell vehicle. Upon the estimate of hydrogen demand from fuel cell vehicles in Ontario, the resulting costs of delivered hydrogen were investigated. In the longer term hydrogen is expected to be produced by utilizing nuclear heat and a thermochemical production cycle. A brief survey of thermochemical hydrogen production cycles was presented with a focus on S-I cycle. Sequential optimization models were developed to explore the minimum utility energy consumption and the minimum number of heat exchangers. Finally an optimal heat exchanger network for S-I thermochemical cycle was defined by a mixed integer optimization model using GAMS.

The dynamic performance of polymer electrolyte membrane fuel cells (PEMFCs) is of great interest for mobile applications such as in automobiles. However, the length scale of a PEM fuel cell's main components are ranging from the micro over the meso to the macro level, and the time scales of various transport processes range from milliseconds up to a few hours. This combination of various spatial and temporal scales makes it extremely challenging to conduct in-situ measurements or other observations through experimental means. Thus, numerical simulation becomes a very important tool to help understand the underlying electrochemical dynamics and transient transport phenomena within PEM fuel cells. In this thesis research, a comprehensive 3D model is developed which accounts for the following transient transport mechanisms: the non-equilibrium phase transfer between the liquid water and water vapor, the non-equilibrium membrane water sorption/desorption, liquid water transport in the porous backing layer, membrane hydration/dehydration, gas diffusion in the porous backing layer, the convective gas flow in the gas channel, and heat transfer. Furthermore, some of the conventionally used modeling assumptions and approaches have been incorporated into the current model. Depending on the modeling purposes, the resulting model can be readily switched between steady and unsteady, isothermal and non-isothermal, single- and multi- phases, equilibrium and non-equilibrium membrane sorption/desorption, and three water production assumptions. The governing equations which mathematically describe these transport processes, are discretized and solved using a finite-volume based commercial software, Fluent, with its user coding ability. To handle the significant non-linearity stemming from the multi-water phase transport, a set of numerical under-relaxation techniques is developed using the programming language C. The model is validated with experimental results and good agreements are achieved. Subsequently, using this validated model numerical studies have been carried out to probe various transient transport phenomena within PEM fuel cells and the cell dynamic responses with respect to different operating condition changes. Furthermore, the impact of flow-field design on the cell performance is also investigated with the three most common flow channel designs.

Polymer electrolyte membrane fuel cells (PEFCs) have long been thought of as a promising clean alternative energy electrochemical device. They are lightweight, highly efficient, modular and scalable devices. A fuel such as H2 or methanol that can be readily produced from a variety of sources can be utilized in PEFCs to generate electricity with low or no emissions. Despite these advantages, fuel cell technologies have failed to reach mass commercialization mainly due to short operational lifetimes and the high cost of materials. In particular, the polymer membrane and the catalyst layer have been problematic in reducing the material cost. Currently, platinum is the dominant material used to catalyze fuel cell reactions. However platinum is very expensive and scarce. In order to pursue the mass commercialization of fuel cells, two methods have been proposed: 1) increasing the utilization of platinum to lower the loading required, and 2) replacing platinum completely with a non-precious material. The latter has been suggested to be the long term solution due to the increasing cost of platinum. This thesis explores the elimination of platinum through the use of nanostructured non-precious metal catalysts for polymer electrolyte fuel cells. Several catalysts have been synthesized without the use of platinum that are active for the oxygen reduction reaction (ORR) which occurs at the cathode. Three different synthetic techniques were utilized using different nitrogen precursors. Aside from the different nitrogen precursors, each set of experiments utilize a different approach to optimize the oxygen reduction performance. Different characterization techniques are used to learn more about the ORR on non-precious metal fuel cells. The first experiment utilizes ethylenediamine, a well-known nitrogen precursor for non-precious metal fuel cell catalysts. Ethylenediamine is deposited onto two different porous carbon black substrates to determine the effectiveness of different porosities in creating active sites for the ORR. Of the two carbon black species, Ketjenblack EC-600JD and Ketjenblack ED-300J, the former was found to be more porous and effective. This result was mainly attributed to the increased surface area of the carbon black which allowed for better dispersion and a greater active site density. In this experiment, the coating of ethylenediamine on carbon black was also refluxed for 3 hours prior to the pyrolysis. It was found that refluxed catalyst samples showed much improved performance than catalyst samples without this procedural modification. The next experiment utilized cyanamide as a nitrogen precursor. Cyanamide was chosen due to its ability to form larger amounts of pyridinic nitrogen on the surface of the catalyst after a high temperature pyrolysis stage. The catalysts were heat-treated at 1000oC and the performance was measured. NH3 was introduced during the pyrolysis, which could remove the excess coating from the carbon surface, and increase the surface area of the catalyst by unblocking the carbon pores. A third modification to the procedure was carried out, where the heat-treated sample was ball-milled, re-coated, and heat-treated again in ammonia conditions to increase the nitrogen functionalities and increase the active site density. The performance was slightly increased from the original heat-treated sample. However due to the decreased surface area, the limiting current density also decreased. It was believed that ball-milling the sample crushed the pores within the catalyst sample, thereby lowering the active surface area and thus the current density. Therefore, the last sample was prepared similarly to the procedure for the third sample, but without ball-milling. This sample had restored surface area and improved ORR performance over all the synthesized catalyst samples – these experiments allowed for important realizations regarding the nature of the Fe-cyanamide-KJ600 catalysts and allowed for a drastic improvement in onset and half-wave potentials from the first catalyst. The final experiment discussed in this thesis describes the work done with 1,2,4,5-tetracyanobenzene and tetracyanoethylene as phthalcyanine precursors for non-precious metal catalysts (NPMCs). Iron(II) acetate was mixed with these phthalocyanine precursors to form polymer sheets of iron phthalocyanine or its monomeric units. By the creation of these polymer sheets of iron phthalocyanine, it allowed for a uniform distribution of iron centres on the surface of the carbon after a heat-treatment step. This allowed for high active site density through the design of these sheet polymers and prevented agglomeration or blockage of active sites which is thought to be a common problem in the synthesis of many NPMCs. Both tetracyanobenzene and tetracyanoethylene as precursors were tested. The tetracyanobenzene catalyst was heat-treated at different temperature ranging from 700-1100oC and characterized through electrochemical tests for the ORR. As an overall conclusion to this work, several catalyst samples were made and different approaches were successfully employed to improve the ORR performance. Of the synthesis treatments utilized to improve performance, each specific catalyst had different parameters to tweak in order to improve ORR performance. With X-ray photoelectron spectroscopy (XPS) analysis, conclusions were also specific to the catalysts structure and synthesis procedure, however quaternary and pyrrolic nitrogen groups seemed to play an influential role to the ORR final performance. Although relative amount of pyridinic nitrogen was not seen to increase with increasing catalyst performance during the studies; it may still play an essential role in the reduction of oxygen on the catalyst surface. The author of this work has not ruled out that possibility. Several recommendations for future work were suggested to broaden the knowledge and understanding of nanostructure non-precious metal catalysts to design a high performing, durable, and low-cost alternative to platinum based catalysts.

The extensive amount of platinum required in order to facilitate the oxygen reduction reaction (ORR) occuring at the cathode of low temperature fuel cells provides cost limitations to the sustainable commercialization of this technology. The development of electrocatalyst materials with either reduced or eliminated platinum dependency is an urgent necessity. The present work investigates the application of nitrogen doped carbon nanotubes (N-CNTs) and their composites as electrocatalyst materials for the ORR. First, N-CNTs are investigated as platinum support materials for proton exchange membrane fuel cells. They were found to result in improved ORR activity in comparison with undoped CNT supported platinum, due to the enhanced catalyst-support interactions and electronic properties induced by nitrogen heteroatoms incorporated into the graphitic structure of CNTs. Second, N-CNTs synthesized from a variety of different precursor materials were investigated as ORR electrocatalysts in alkaline conditions. The influence of the precursor materials was illustrated with improved ORR activity and nitrogen concentration observed for N-CNTs synthesized with precursor materials containing higher nitrogen to carbon contents. Highly active N-CNTs based on ethylenediamine were fabricated into thin, free standing films for use as a stand-alone cathode catalyst layer in an alkaline anion exchange membrane fuel cell. Finally, metal-free N-CNTs were developed and demonstrated to provide promising ORR in the absence of any metal interactions.