Water electrolysis is one of the first methods used to generate hydrogen and is thus not considered to be a new technology. With advances in proton exchange membrane technology and the global tendency to implement renewable energy, the technology of water electrolysis by implementation of proton exchange membrane as solid electrolyte has developed into a major field of research over the last decade. To gain an understanding of different components of the electrolyser it is best to conduct a performance analysis based on hydrogen production rates and polarisation curves. The study aim was to compare the technologies of membrane electrode assembly with gas diffusion electrode and the proton exchange membranes of Nafion® and polybenzimidazole in a commercial water electrolyser. To determine which of the components are best suited for the process a laboratory scale electrolyser was to be used to replicate the commercially scaled performance. The effect of feed water contaminants on electrolyser performance was also investigated by introducing iron and magnesium salt solutions and aqueous methanol solutions in the feed reservoir. Components to be tested included different PEM types as well as the base component on which the electrocatalyst layer is applied. The proton exchange membranes compared were standard Nafion® N117 and polybenzimidazole meta-sulfone sulfonated polyphenyl sulfone (PBI-sPSU). A laboratory scale electrolyser from Giner Electrochemical Systems was utilised where different components were tested and compared with one another. Experimental results with commercial membrane electrode assemblies and gas diffusion electrodes demonstrated the influence of temperature on electrolyser performance for the proton exchange membranes, where energy efficiency increased with temperature. The effect of pressure was insignificant over the selected pressure range. Comparison of membrane electrode assembly and gas diffusion electrode technologies showed enhanced performance from MEA technology, this was most likely due to superior electrocatalyst contact with the PEM. Results of synthesised Nafion® N117 and PBI-sPSU MEA showed increased performance for PBI-sPSU, but it was found to be more susceptible to damage under severe conditions. The effect of metal cations in the supply reservoir exhibited reduced energy efficiencies and increased specific energy consumption for the test duration. Treatment with sulphuric acid was found to partially restore membrane electrode assembly performance, though it is believed that permanent damage was inflicted on the membrane electrode assembly electrocatalyst. Use of aqueous methanol solutions were found to increase electrolyser performance. It was also found that aqueous methanol electrolysis occurs at lower current densities, whereas a combination of aqueous methanol and water electrolysis occurred at higher current densities depending on the concentration of methanol. / Thesis (MIng (Chemical Engineering))--North-West University, Potchefstroom Campus, 2013.

Water electrolysis is one of the first methods used to generate hydrogen and is thus not considered to be a new technology. With advances in proton exchange membrane technology and the global tendency to implement renewable energy, the technology of water electrolysis by implementation of proton exchange membrane as solid electrolyte has developed into a major field of research over the last decade. To gain an understanding of different components of the electrolyser it is best to conduct a performance analysis based on hydrogen production rates and polarisation curves. The study aim was to compare the technologies of membrane electrode assembly with gas diffusion electrode and the proton exchange membranes of Nafion® and polybenzimidazole in a commercial water electrolyser. To determine which of the components are best suited for the process a laboratory scale electrolyser was to be used to replicate the commercially scaled performance. The effect of feed water contaminants on electrolyser performance was also investigated by introducing iron and magnesium salt solutions and aqueous methanol solutions in the feed reservoir. Components to be tested included different PEM types as well as the base component on which the electrocatalyst layer is applied. The proton exchange membranes compared were standard Nafion® N117 and polybenzimidazole meta-sulfone sulfonated polyphenyl sulfone (PBI-sPSU). A laboratory scale electrolyser from Giner Electrochemical Systems was utilised where different components were tested and compared with one another. Experimental results with commercial membrane electrode assemblies and gas diffusion electrodes demonstrated the influence of temperature on electrolyser performance for the proton exchange membranes, where energy efficiency increased with temperature. The effect of pressure was insignificant over the selected pressure range. Comparison of membrane electrode assembly and gas diffusion electrode technologies showed enhanced performance from MEA technology, this was most likely due to superior electrocatalyst contact with the PEM. Results of synthesised Nafion® N117 and PBI-sPSU MEA showed increased performance for PBI-sPSU, but it was found to be more susceptible to damage under severe conditions. The effect of metal cations in the supply reservoir exhibited reduced energy efficiencies and increased specific energy consumption for the test duration. Treatment with sulphuric acid was found to partially restore membrane electrode assembly performance, though it is believed that permanent damage was inflicted on the membrane electrode assembly electrocatalyst. Use of aqueous methanol solutions were found to increase electrolyser performance. It was also found that aqueous methanol electrolysis occurs at lower current densities, whereas a combination of aqueous methanol and water electrolysis occurred at higher current densities depending on the concentration of methanol. / Thesis (MIng (Chemical Engineering))--North-West University, Potchefstroom Campus, 2013.

A dynamic MEA absorption process model has been developed to study the operability of this process in a dynamic fashion and to develop a control strategy to maintain the operation of the MEA scrubbing CO2 capture process in the presence of the external perturbations that may arise from the transient operation of the power plant. The novelty in this work is that a mechanistic model based on the conservation laws of mass and energy have been developed for the complete MEA absorption process. The model developed in this work was implemented in gPROMS. The process response of the key output variables to changes in the key input process variables, i.e., the flue gas flow rate and the reboiler heat duty, are presented and discussed in this study. In order to represent the actual operation of a power plant, the dynamic response of the MEA absorption process to a sinusoidal change in the flue gas flow rate was also considered in the present analysis. The mechanistic dynamic model was applied to develop a basic feedback control strategy. The implementation of a control strategy was tested by changing the operating conditions for the flue gas flow rate. The controlled variables, i.e., the percentage of CO2 absorbed in the absorber column and the reboiler temperature, were maintained around their nominal set point values by manipulating the valve stem positions, which determine the lean solvent feed flow rate at the top of the absorber column, and the reboiler heat duty, respectively. For the sinusoidal test, the amplitude of the oscillations observed for the controlled variables was smaller than those observed for the open-loop tests. This is because the variability of the controlled variables was transferred to the manipulated variable in the closed loop. The mechanistic dynamic model developed in this process can be potentially used as a practical tool that can provide insight regarding the dynamic operation of MEA absorption process. The model developed in this work can also be used as a basis to develop other studies related to the operability, controllability and dynamic flexibility of this process.

O processo de Impressão à Tela foi desenvolvido neste trabalho para ser aplicável à deposição de camadas catalíticas em eletrólitos utilizados em PEMFC. Inicialmente foram construídos conjuntos eletrodos-membrana (MEAs) de 25 cm2 de área ativa e comparados com outros produzidos pelo método de Aspersão. Os dois métodos produziram MEAs que apresentaram densidades de corrente acima de 600 mA.cm-2 a 600 mV. Foi conduzido um estudo para o aumento de escala do MEA para 144 cm2 de área ativa. Para este fim, foi projetada uma célula para abrigar os MEAs destas dimensões. Neste projeto, o perfil dos canais de distribuição de gás foi desenvolvido através da ferramenta de fluido dinâmica computacional Comsol Multiphysics, sendo que, para o projeto das placas componentes da célula foi utilizado o AutoCAD. Os MEAs de 144 cm2 confeccionados por Aspersão e por Impressão à Tela foram confrontados com MEAs comerciais de iguais dimensões. Estes apresentaram melhor desempenho a 600 mV, entretanto são mais custosos que a solução desenvolvida neste estudo. O novo método apresentou-se adequado para a confecção de MEAs de baixo custo de diferentes geometrias e para a produção de lotes a serem utilizados em pequenos módulos de potência. / The Sieve Printing process was studied in this work to apply the catalyst layers onto electrolytes utilized in PEMFC. Initially, 25 cm2 active area MEAs were built for comparison with others MEAs produced by the Spray technique. The two methods produced MEAs that showed current densities higher than 600 mA.cm-2 at 600 mV. A scaling up study for 144 cm2 of active area MEAs was carried out. For this purpose, a new cell had to be projected for shelter the MEAs in such dimensions. The profile of the gas distribution channels was developed through the computational fluid dynamic tool Comsol Multiphysics. For the design of the bipolar plates of the cell the AutoCAD was used. The 144 cm2 MEAs made by Spray and by Sieve Printing methods were confronted with commercials MEAs ones of equal dimensions. These commercials MEAs presented better performance at 600 mV, however they were more costly than the solution developed in this study. The new method was showed to be adequate to fabricate low cost MEAs of different geometries and to produce any amount of MEAs for small scale stacks (up to 10 kW).

Micro-direct methanol fuel cells (micro-DMFC) can be the power supply solution for the next generation of handheld devices. The applications of the micro-DMFCs require them to have high compactness, high performance, light weight, and long life. The major goal of this research project is to enhance the volumetric power density of direct methanol fuel cells (DMFCs). A performance roadmap has been formulated and showed that patterning the planar membrane electrode assembly (MEA) to 2-D and 3-D corrugated manifolds can greatly increase the power generation with very modest overall volume increases. In this project, different manufacturing processes for patterning MEAs with corrugations have been investigated. A folding process was selected to form 2D triangular corrugations on MEAs for experimental validations of the performance prediction. The experimental results show that the volumetric power densities of the corrugated MEAs have improved by about 25% compared to the planar MEAs, which is lower than the expected performance enhancement. ABAQUS software was used to simulate the manufacturing process and identify the causes of deformations during manufacture. Experimental analysis methods like impedance analysis and 4 point-probes were used to quantify the performance loss and microstructure alteration during the forming process. A model was proposed to relate the expected performance of corrugated MEAs to manufacturing process variables. Finally, different stacking configurations and issues related to cell stacking for corrugated MEAs are also investigated.

O processo de Impressão à Tela foi desenvolvido neste trabalho para ser aplicável à deposição de camadas catalíticas em eletrólitos utilizados em PEMFC. Inicialmente foram construídos conjuntos eletrodos-membrana (MEAs) de 25 cm2 de área ativa e comparados com outros produzidos pelo método de Aspersão. Os dois métodos produziram MEAs que apresentaram densidades de corrente acima de 600 mA.cm-2 a 600 mV. Foi conduzido um estudo para o aumento de escala do MEA para 144 cm2 de área ativa. Para este fim, foi projetada uma célula para abrigar os MEAs destas dimensões. Neste projeto, o perfil dos canais de distribuição de gás foi desenvolvido através da ferramenta de fluido dinâmica computacional Comsol Multiphysics, sendo que, para o projeto das placas componentes da célula foi utilizado o AutoCAD. Os MEAs de 144 cm2 confeccionados por Aspersão e por Impressão à Tela foram confrontados com MEAs comerciais de iguais dimensões. Estes apresentaram melhor desempenho a 600 mV, entretanto são mais custosos que a solução desenvolvida neste estudo. O novo método apresentou-se adequado para a confecção de MEAs de baixo custo de diferentes geometrias e para a produção de lotes a serem utilizados em pequenos módulos de potência. / The Sieve Printing process was studied in this work to apply the catalyst layers onto electrolytes utilized in PEMFC. Initially, 25 cm2 active area MEAs were built for comparison with others MEAs produced by the Spray technique. The two methods produced MEAs that showed current densities higher than 600 mA.cm-2 at 600 mV. A scaling up study for 144 cm2 of active area MEAs was carried out. For this purpose, a new cell had to be projected for shelter the MEAs in such dimensions. The profile of the gas distribution channels was developed through the computational fluid dynamic tool Comsol Multiphysics. For the design of the bipolar plates of the cell the AutoCAD was used. The 144 cm2 MEAs made by Spray and by Sieve Printing methods were confronted with commercials MEAs ones of equal dimensions. These commercials MEAs presented better performance at 600 mV, however they were more costly than the solution developed in this study. The new method was showed to be adequate to fabricate low cost MEAs of different geometries and to produce any amount of MEAs for small scale stacks (up to 10 kW).

Les recherches s’inscrivent dans une prospection qui étudie la viabilité de la valorisation du CO2 d’un incinérateur de déchets industriels. Plusieurs licences commerciales existent pour le captage du CO2 dans des gaz de combustion mais il n’existe pas de référence pour le traitement de fumées d’incinérateur de déchets. Les travaux évaluent, à l’aide d’une installation pilote, la viabilité du captage du CO2 en postcombustion par absorption/désorption avec un solvant à 30 % massique en monoéthanolamine (MEA). Tout d’abord, une synthèse bibliographique identifie les verrous technologiques. Puis, le fonctionnement de l’installation est détaillé. Ensuite, une étude paramétrique a évalué les performances de captage du CO2 et la consommation énergétique du pilote. Enfin, des expériences sur une période de 5 jours ont étudié la résistance chimique du solvant face des gaz de combustion. Les travaux de recherche ont permis une première validation du procédé pour un incinérateur de déchets. / This research is part of a survey designed to establish the viability of the CO2 recovery as a raw material from an industrial waste incinerator.. Several commercial licenses are available to capture CO2 in flue gas, but there are no references for incinerators. This work studies with a pilot the post-combustion CO2 capture from incinerator flue gas using absorption/desorption process with 30 %wt monoethanolamine (MEA). A literature review identifies the technology gaps. Then, the pilot setup was described. A parametric study has evaluated the pilot performance for CO2 capture and energy consumption. Finally, Long runs (5 days) have studied the solvent chemical stability in front of incinerator flue gas. The laboratory experiments show that CO2 capture form incinerator flue gas is possible.

The doctoral thesis deals with investigation of the catalysts and ionexchanege membranes for fuel cells H2-O2. The work contains the basic principles of chemical reactions, thermodynamic aspects and kinetic properties in PEM fuel cells.Ion-exchagers based on fluorinated polymer sulfonic acids known as NAFION are used in most cases. These compounds are very expensive. Also a strong corrosive attribute requires platinum as a catalysator. These facts make the membrane fuel cells fully non-competetive with e.g. internal combustion engine in spite of all ecological advantages of this electrical power source. The subject of doctoral thesis is research and development of compounds for the composite electrode materials base on NiOx, Ni-Pd and Raney Ni suitable as catalysts a nd alkaline or bipolar ionexchange membranes for electrochemical fuel cells.

[pt] Essa tese estuda o impacto de mecanismos contratuais no valor de operações de fusões e aquisições e propõe três modelos distintos de avaliação. Ademais, sob a ótica da Teoria dos Contratos, ressaltamos o impacto do comportamento dos agentes nas características das cláusulas utilizadas ou ainda no sucesso da transação. Primeiro, desenvolvemos um modelo para earnouts fornecendo fundamentos para como essa cláusula em particular deve ser estruturada e como seu valor deve ser estimado, especialmente considerando sua similaridade com opções. Além disso, testamos diferentes formatos para o earnout, como opção binária e opção de compra. Segundo, modelamos a cláusula de anti-diluição, a qual proporciona uma proteção adicional para investidores, em especial no contexto de Venture Capital. Anti-diluição tem papel fundamental como seguro para investidores contra rodadas de investimento futuras com valuation abaixo do que fora previamente pago pelo investidor. Por fim, desenvolvemos um modelo de avaliação para preferência de liquidação, a qual também pode ser uma alternativa de garantia para investidores em operações de fusões e aquisições. Preferência de liquidação é tipicamente definida como o direito do investidor em receber seu investimento adicionado de um determinado montante em caso de algum evento de liquidação, em preferência os demais acionistas. Os resultados indicam que os mecanismos contratuais largamente utilizados em operações de fusões e aquisições tem impacto relevante no valor justo da transação. Adicionalmente, os resultados sugerem que os mecanismos contratuais são importantes ferramentas para mitigar o risco para investidores, viabilizando determinadas operações que se tornariam inviáveis, especialmente ao considerarmos a assimetria de informação entre comprador e vendedor. / [en] This thesis studies the impact of contractual mechanisms in MeA valuation deals and proposes three models to evaluate them. Also, under the Contract Theory lens, we draw attention to the parties behavior and its impact on clauses settings or transaction success. First, we develop a model for earnouts and provide the foundation for understanding how they might best be structured and how their value might be estimated, especially considering their similarity to financial options. Furthermore, we also test different features for the earnout, such as binary options and a combination of binary and call options. Second, we model the anti-dilution covenant, which provides additional protection for investors, especially in a venture capital context. Antidilution plays an important role as insurance for venture capitalists against down round, which is a subsequent financing event at a lower valuation. Lastly, we developed a valuation model for liquidation preference, which can be an alternative guarantee for investors in MeA deals. Liquidation preference is typically defined as the right of the investor (usually holding preference shares), to receive its investment amount plus a certain agreed percentage of the proceeds in the event of a liquidation of the company, in preference over the other shareholders. Our findings indicate that the typical legal covenants used in MeA deals have a relevant impact on their fair value and may work as important tools to bridge the gap between the buyer and the seller, especially considering the information asymmetry on this context. On the other hand, depending on the clauses settings, the risk may be too skewed to the seller side, making the deal structure too expensive under his perspective. By testing the model s parameters sensitivity, we provided the inputs the seller needs to evaluate and pursue the optimal contractual terms.

An Active Microscaffold System with Fluid Delivery and Stimulation/Recording Functionalities for Culturing 3-D Neuronal Networks Laura Elizabeth Rowe 215 Pages Directed by Dr. A. Bruno Frazier An active microscaffold system with fluid delivery and electrical stimulation/recording functionalities for 3-D neuronal culture studies is presented. The microscaffolds presented in this dissertation consist of an array of microfabricated towers with integrated microfluidic channels, fluid ports, and electrodes. The microfluidic channels and ports allow for perfusion of nutrients, gas exchange, and biochemical control of the extracellular environment throughout the 3-D culture, while the electrodes allow for active stimulation/recording of the 3-D neuronal network. In essence, the microscaffold serves as an artificial circulatory system to enable 3-D in vitro growth and proliferation of re-aggregate neuronal cell cultures. Increased cell survival on microscaffolds with nutrient perfusion at 14 and 21 days in vitro (DIV) is presented. Additionally, the microtower scaffold is built upon a substrate that is compatible with the Multi Channel Systems preamplifier setup to enable electrical stimulation/recording of the cultured network in a 3-D mutilelectrode array (MEA) environment. Impedance measurements on the functioning microtower electrodes were obtained. The overall goal of this research was to develop a BioMEMS technology to provide neuroscientists with a better investigative tool for studying 3-D in vitro neuronal networks than is currently available.