Two formal design methodologies, biomimetic design and the Theory of Inventive Problem Solving, TRIZ, were applied to the redesign of a Proton Exchange Membrane (PEM) fuel cell. Proof of concept prototyping was performed on two of the concepts for water management. The liquid water collection with strategically placed wicks concept demonstrated the potential benefits for a fuel cell. Conversely, the periodic flow direction reversal concepts might cause a potential reduction water removal from a fuel cell. The causes of this water removal reduction remain unclear. In additional, three of the concepts generated with biomimetic design were further studied and demonstrated to stimulate more creative ideas in the thermal and water management of fuel cells. The biomimetic design and the TRIZ methodologies were successfully applied to fuel cells and provided different perspectives to the redesign of fuel cells. The methodologies should continue to be used to improve fuel cells.

Two formal design methodologies, biomimetic design and the Theory of Inventive Problem Solving, TRIZ, were applied to the redesign of a Proton Exchange Membrane (PEM) fuel cell. Proof of concept prototyping was performed on two of the concepts for water management. The liquid water collection with strategically placed wicks concept demonstrated the potential benefits for a fuel cell. Conversely, the periodic flow direction reversal concepts might cause a potential reduction water removal from a fuel cell. The causes of this water removal reduction remain unclear. In additional, three of the concepts generated with biomimetic design were further studied and demonstrated to stimulate more creative ideas in the thermal and water management of fuel cells. The biomimetic design and the TRIZ methodologies were successfully applied to fuel cells and provided different perspectives to the redesign of fuel cells. The methodologies should continue to be used to improve fuel cells.

<p>The direct methanol fuel cell or DMFC is emerging as a promising alternative energy source for many applications. Developed and developing countries, through research, are fast seeking a cheap and stable supply of energy for an ever-increasing number of energy-consuming portable devices. The research focus is to have DMFCs meeet this need at an affordable cost is problematic. There are means and ways of making this a reality as the DMFC is found to be complementary to secondary batteries when used as a trickle charger, full charger, or in some other hybrid fuel cell combination. The core functioning component is a catalyst containing MEA, where when pure platinum is used, carbon monoxide is the thermodynamic sink and poisons by preventing further reactions at catalytic sites decreasing the life span of the catalyst if the CO is not removed. Research has shown that the bi-functional mechanism of a platinum-ruthenium catalyst is best because methanol dehydrogenates best on platinumand water dehydrogenation is best facilitated on ruthenium. It is also evident that the addition of other metals to that of PtRu/C can make the catalyst more effective and effective and increase the life span even further. In addition to this, my research has attempted to reduce catalyst cost for DMFCs by developing a low-cost manufacturing technique for catalysts, identify potential non-noblel, less expensive metallic systems to form binary, ternary and quarternary catalysts.</p>

The thermally regenerative fuel cell (TRFC) concept that is analyzed is a polymer electrolyte membrane fuel cell (PEMFC), powered by the electro-oxidation of H2 and the electro-reduction of propiophenone. The main products of this fuel cell should be 1-phenyl-1-propanol and electricity. The 1-phenyl-1-propanol should then be converted back to propiophenone, while hydrogen is regenerated by using waste heat and a metal catalyst (Pd/SiO2). The first objective was to find a compatible polymer that would work as either an ionomer/binding agent and as a membrane in the membrane electrode assembly (MEA) of the TRFC. This was achieved by checking the compatibility of each polymer with 1-phenyl-1-propanol and propiophenone (the alcohol-ketone pair). Catalyst coated gas diffusion layers or catalyst coated membranes were made to test the stability of the polymers in the catalyst bed when exposed to the alcohol-ketone pair. If the polymer was compatible with the alcohol-ketone pair, MEAs were constructed using this polymer. The second objective was to test these MEAs inside a H2/propiophenone fuel cell that would prove the concept of our envisioned TRFC. It was found that the only polymer that was stable in the alcohol-ketone pair was mPBI (m-phenylene polybenzimidazole). The mPBI had to be doped with H3PO4 to enable H+ conductivity. Unfortunately, some H3PO4 leached out of the H3PO4-doped mPBI when in the presence of the alcohol-ketone pair. MEAs that were created using H3PO4-doped mPBI were found to work for H2/air and H2/propiophenone fed PEMFCs. The best performance achieved with the H2/propiophenone powered fuel cell was 6.23 μW/cm2. Unfortunately, the presence of the 1-phenyl-1-propanol product could not be proved by EIS or CV on the fuel cell, or by GC-FID of the cathode effluent. Other unknown products were seen in the GC-FID spectrum of the cathode effluent. Therefore, it is possible that the propiophenone did reduce at the cathode but it produced an unknown product. In conclusion, the viability of the proposed TRFC system was not verified. H3PO4 leaching from the MEA makes it impossible to use H3PO4-doped mPBI as the electrolyte in the final version of the MEA in the TRFC system. / Thesis (Master, Chemistry) -- Queen's University, 2013-04-12 17:16:37.724

Small combined heat and power generators have the potential to reduce energy consumption and greenhouse gas emissions of residential buildings. Recently, much attention has been given to these units. To date, the majority of studies in this field have concentrated on the steady operational performance of a specific generator type, and the available computer models have largely been theoretical in nature. <br /><br /> The main goal of this study was to evaluate the performance of the latest combined heat and power generators, when integrated into Canadian residential homes. A fair comparison of four 1 kW (electrical) units was made. The combined heat and power units studied were based on PEM fuel cell, solid oxide fuel cell, Stirling Engine, and internal combustion engine energy converters. <br /><br /> This study utilized recent test data in an attempt to evaluate the most efficient method of integrating the combined heat and power units into residential houses. Start-up, shut down, and load change transients were incorporated into the simulations. The impact of load variations due to building thermal envelope differences and varying building heating system equipment was evaluated. The simulations were evaluated using TRNSYS software. The building heat demands were determined with eQuest hourly building simulation software. <br /><br /> All of the combined heat and power units under study were capable of providing a net annual benefit with respect to global energy and greenhouse gas emissions. The fuel cells offer the highest integrated performance, followed closely by the internal combustion engine and lastly the Stirling engine. Annual global energy savings up to 20%, and greenhouse gas savings up to 5. 5 tonnes per year can be achieved compared to the best conventional high efficiency appliances. <br /><br /> Heat demand influences performance greatly. As the thermal output of the generator unit approaches half of the average building thermal demand, the system design becomes critical. The system design is also critical when integrating with a forced air furnace. Only the PEM fuel cell unit produces clear global energy and emissions benefits when operating in the summertime.

The ever increasing demand of petroleum in the transport sector has led to depletion of low cost/low risk reserves, increased levels of pollution, and greenhouse gas emissions that take a heavy toll on the environment as well as the national economy. There is an urgent need to use alternative energy resources along with an efficient and affordable energy conversion system to arrest environmental degradation. Polymer electrolyte fuel cells (PEFCs) show great promise in this regard - they use hydrogen gas as a fuel that electrochemically reacts with air to produce electrical energy and water as the by product. In a fuel cell electric vehicle (FCEV), these zero tail pipe emission systems offer high efficiency and power density for medium-heavy duty and long range transportation. However, PEFC technology is currently challenged by its limited durability when subjected to harsh and adverse operating conditions and transients that arises during the normal course of vehicle operation. The hydrogen-based fuel cell power train for electric vehicles must achieve high durability while maintaining high power efficiency and fuel economy in order to equal the range and lifetime of an internal-combustion-engine vehicle. The technology also needs to meet the cost targets to make FCEVs a commercial success. In this dissertation, one of the degradation phenomena that severely impede the durability of the system has been investigated. In scenarios where the cell becomes locally starved of hydrogen fuel, “cell reversal” occurs, which causes the cell to consume itself through carbon corrosion and eventually fail. Carbon corrosion in the anode disrupts the original structure of the electrode and can cause undesirable outcomes like catalyst particle migration, aggregation, loss of structural and chemical integrity. A comprehensive study using advanced electrochemical diagnostics and high resolution 3D imaging was performed and a new understanding to extend PEFC life time and robustness, by implementing engineered materials solutions, has been achieved. This will eventually help in making fuel cell systems more efficient, durable and economically viable, in order to better harness clean energy resources.

Proton Exchange Membrane Fuel Cells (PEMFCs) present a promising alternative to the conventional internal combustion engine for automotive applications because of zero harmful exhaust emissions, fast refuelling times and possibility to be powered by hydrogen generated through renewable energy. However, several issues need to be addressed before the widespread adoption of PEMFCs, one such problem is the removal of waste heat from the fuel cell electrochemical reaction at high ambient temperatures. Automotive scale fuel cells are most commonly liquid cooled, evaporative cooling is an alternative cooling method where liquid water is added directly into the fuel cell flow channels. The liquid water evaporates within the flow channel, both cooling and humidifying the cell. The evaporated water, along with some of the product water, is then condensed from the fuel cell exhaust, stored, and re-used in cooling the fuel cell. This work produces a system level model of an evaporatively cooled fuel cell vehicle suitable for the study of water balance and heat exchanger requirements across steady state operation and transient drive cycles. Modelling results demonstrate the ability of evaporatively cooled fuel cells to self regulate temperature within a narrow region (±2°C) across a wide operating range, provided humidity is maintained within the flow channels through sufficient liquid water addition. The heat exchanger requirements to maintain a self sufficient water supply are investigated, demonstrating that overall heat exchange area can be reduced up to 40% compared to a liquid cooled system due to the presence of phase change within the vehicle radiator improving heat transfer coefficients. For evaporative cooling to remain beneficial in terms of heat exchange area, over 90% of the condensed liquid water needs to be extracted from the exhaust stream. Experimental tests are conducted to investigate the condensation of water vapour from a saturated air stream in a compact plate heat exchanger with chevron flow enhancements. Thermocouples placed within the condensing flow allow the local heat transfer coefficient to be determined and an empirical correlation obtained. The corresponding correlation is used to produce a heat exchanger model and study the influence different heat exchanger layouts have on the overall required heat transfer area for an evaporatively cooled fuel cell vehicle. A one-dimensional, non-isothermal model is also developed to study the distribution of species, current density and temperature along the flow channel of an evaporatively cooled fuel cell using different methods of liquid water addition. Results show that good performance can be achieved with cathode inlet humidities as low as 20%, although some anode liquid water addition may be required at high current densities due to increased electro-osmotic drag. It is also demonstrated that both good membrane hydration and temperature regulation can be managed by uniform addition of liquid water across the cell to maintain a target exhaust relative humidity.

Solid oxide fuel cells (SOFCs) are the most efficient electrochemical devices to directly convert stored chemical energy to usable electrical energy. The infiltration of ceramic conductors and catalytic metals (e.g. Ni, Pt and Pd) into porous scaffolds that had been pre-sintered onto the electrolyte is regarded as an effective way of promoting the electrode performance via producing nano-scale particles by in-situ sintering at relatively low temperatures. Large-scale fuel cells (5 cm x 5 cm) are prepared with this method and tested to demonstrate its scalability so as to achieve industrial applications. Four configurations are examined in respect of variation in the thickness of cathode, anode and electrolyte to investigate their effect on the infiltration process and electrochemical losses. To further improve infiltration as a method of fabricating high-performance electrodes, much effort is also devoted to optimising and understanding the microstructure of pre-sintered scaffold and its effect on infiltration using image analysis and electrochemical impedance. First, we have prepared the nano-structured electrodes on the 200-μm thick electrolyte-supported planar fuel cell with a 5 x 5 cm dimension. The 8YSZ scaffold is impregnated with La₀.₈Sr₀.₂Cr₀.₅Mn₀.₅O₃ (LSCM) for the anode and La₀.₈Sr₀.₂FeO₃ (LSF) for the cathode. The large planar cell achieved a maximum power density of 116 mWcm⁻² at 700°C and 223 mWcm⁻² at 800°C in humidified hydrogen. Moreover, with the addition of catalyst of 10 wt.% CeO₂ and 1 wt.% Pd, the cell performance reached 209 mWcm⁻² at 700°C and 406 mWcm⁻² at 800°C. Compared to the cell without catalysts, ceria and Pd are efficient in decreasing the electrochemical reaction resistance but making the diffusion resistance more obvious. Second, supported thin electrolytes are prepared by scalable tape casting to reduce the ohmic losses as that in electrolyte-supported cell. The cell with thick LSF-infiltrated support is very efficient in decreasing the ohmic loss thanks to the high solubility of its nitrate precursors in water and fairly high electric conductivity, but the thick cathode causes higher diffusional losses, especially at 800°C. Even though with thinner electrolyte, the ohmic loss from the cell with thick infiltrated anode is comparable to that of 200-μm electrolyte supported cell. The extra ohmic loss can be attributed to the compositional segregation of La₀.₇Sr₀.₃VO₃ (LSV) in the infiltration process in the anode, and lower loading, ca. 25 wt %. A trade-off between the diffusional loss from the cathode and the extra ohmic loss from the thick anode can be achieved by sandwiching the electrolyte between electrodes with identical thickness. A flat large area cell prepared with this method can achieve a high performance of 300 mW cm⁻² and 489 mW cm⁻² at 700°C and 800°C, respectively, if Pd-ceria is added to the anode LSV as catalyst. Third, image analyses and modelling are performed on the constrained sintering of porous thin film on a rigid substrate to study the evolution of pores at different stages. Result shows that both the anisotropy of the pore former/pores in the green body and transport of materials during the sintering process have effect on the orientation of the final microstructure. Specifically, the in-plane orientation of large-scale pores will be intensified during the constrained sintering process, while those small pores whose shape are subjected to materials transport during sintering tend to erect during the constrained sintering process at 1300°C. Fourth, image analyses and semi-quantification are used to predict the correlation between the microstructure and performance of the LSF-infiltrated electrode. Two types of YSZ powders, Unitec 1-μm powder with a broad particle-size distribution having two maxima at ~ 0.1 μm and 0.8 μm, and Unitec 2-μm powder with only one at ~1 μm are selected to fabricate the porous scaffold for infiltration. The porous structure using Unitec 2-μm powder shows finer YSZ grains and a higher boundary length than the 2-μm powder. Ac impedance on symmetrical cells was used to evaluate the performance of the electrode impregnated with 35-wt.% La₀.₈Sr₀.₂FeO₃. At 700°C, the electrode from Unitec 2-μm powder shows a polarization resistance (Rp) of 0.21 Ω cm², and series resistance (Rs) of 8.5 Ω cm², lower than the electrode from Unitec 1-μm powder does. The quantitative study on image indicates that Unitec 2-μm powder is better in producing architecture of high porosity or long triple phase boundary (TPB), which is attributed as the reason for the higher performance of the LSF-impregnated electrode. Finally, oxides of transition metals are doped into the YSZ-infiltrated LSF electrode and the impedances of symmetrical cells are tested to evaluate their effect on the ohmic and polarization resistance. Cobalt oxides are able to reduce the ohmic resistance and polarization resistance only when it is calcined at 700°C, but nickel oxide can reduce both the ohmic and polarization resistance if it is well-mixed and fully reacted with the previously infiltrated LSF. Doping of manganese oxide into LSF-YSZ electrode slightly changes the ohmic resistance but significantly increases the polarization resistance. Detailed analyses of the impact of infiltration process on the impedance data and oxygen reduction process are also presented.

The inordinate reliance of the United States on the automobile for transportation causes a number of problems for the nation. Finite supplies of petroleum imported from volatile parts of the world place the economy at risk from price spikes and eventual depletion. Pollution from motor vehicle exhaust has public health and environmental consequences. Many politicians, automotive interest groups, and others advocate for the use of alternative fuels to replace fossil fuels. This paper investigates the advantages and disadvantages of the following: Natural Gas, Ethanol, Biodiesel, Hydrogen Fuel Cells, and Hybrid Gasoline Electric Systems. The paper concludes with a discussion of the problems associated with the automobile that will not be addressed through a movement towards alternative fuels: urban sprawl, transportation equity, environmental degradation, and public health. / Master of Urban and Regional Planning

[pt] Uma célula PEM (membrana de troca de prótons) de 5 kW com reformador foi instalada na PUC-Rio tendo como objetivo a determinação experimental de seu desempenho e de seu potencial de cogeração para aumentar o uso da energia química do combustível. A unidade utiliza um processador de combustível para converter energia do gás natural em um reformado rico em hidrogênio. A célula é totalmente instrumentada fornecendo dados para o cálculo da eficiência global do sistema (eficiência total), eficiência do reformador, eficiência da pilha, eficiência de conversão (DC/AC) e o potencial de cogeração. Este estudo detalha as equações teóricas necessárias para calcular os parâmetros, os conceitos termodinâmicos e eletroquímicos, e experimentalmente, os balanços de massa e energia, comparando os resultados. Foram obtidos dados no regime permanente resultando em eficiências do reformador, da pilha, de conversão e global, junto com os desvios padrões calculados. Também foi comprovado que a energia perdida no reformador e na pilha é praticamente a mesma. Foi mostrado que as degradações de desempenho do reformador e da pilha reduzem a vida útil da célula do conjunto, que também tem uma eficiência abaixo do que foi indicado pelo fabricante. O potencial de aproveitamento da energia química do combustível foi estimado através do cálculo do calor rejeitado pela pilha e através do calor rejeitado pelo reformador dando um valor de 71,3 %. / [en] A 5 kW proton exchange membrane fuel cell (PEMFC) with a reformer has been installed and tested at the Pontifical Catholic University of Rio de Janeiro (PUC-Rio), Brazil, aiming the experimental determination of its performance and co-generation potential to increase the fuel chemical energy usage. The unit uses a fuel processor to convert energy from natural gas into hydrogen rich reformate. The fuel cell is totally instrumented, supplying data for calculating the overall system efficiency (total efficiency), reformer efficiency, stack efficiency, conversion efficiency (DC/AC), and co- generation potential, at previously set up output powers of 2,5 kW. This study details the equations required for calculating the parameters, both theoretically, from thermodynamics and electrochemics points of view, and experimentally, from mass and energy balances, comparing the results. Steady state data were taken, resulting in reformer, stack, conversion and total average efficiencies, together with the calculated standard deviation. It was also found that the energy loss in the reformer and in the stack are approximately the same. It was also showed that the reformer and stack degradation reduce the system life, which also has an efficiency lower what is stated by the manufacturer. The fuel chemical energy usage potential was estimated by calculating the heat rejected by the stack and the heat rejected in the reformer, giving a value of 71,3%.