Hydrogen diffusion is investigated in a 50 nm film of vanadium and a vanadium superlattice. Diffusion constants for three different temperature and pressure pairs are determined for the 50 nm film. The diffusion constants for the temperature and pressure pairs are determined to be 4.5 $\pm$ 0.1 $\cdot 10^{-5} \text{ cm}^{-2}$ at 463 K and 0.05 H/V, 5.6 $\pm$ 0.1 $\cdot 10^{-5} \text{ cm}^{-2}$ at 463 K and 0.12 H/V and 8.0 $\pm$ 0.2 $\cdot 10^{-5} \text{ cm}^{-2}$ at 493 K and 0.05 H/V. The temperature and concentration dependence of the diffusion constants are determined. A concentration dependence of the diffusion constant is found with a higher rate of diffusion for a higher hydrogen concentration. The activation energy of chemical diffusion is determined to be 0.38 $\pm$ 0.03 eV.

Philosophiae Doctor - PhD / Today fossil fuels such as oil, coal and natural gas are providing for our ever growing energy needs. As the world’s fossil fuel reserves fast become depleted, it is vital that alternative and cleaner fuels are found. Renewable energy sources are the way of the future energy needs. A solution to the looming energy crisis can be found in the energy carrier hydrogen. Hydrogen can be produced by a number of production technologies. One hydrogen production method explored in this study is electrolysis of water.

京都大学 / 新制・課程博士 / 博士(エネルギー科学) / 甲第24974号 / エネ博第470号 / 新制||エネ||88(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー社会・環境科学専攻 / (主査)教授 MCLELLAN Benjamin, 教授 下田 宏, 教授 吉田 純 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

The importance of Hydrogen (H2) in current global energy systems is undeniable. Moving from the energy systems depending on fossil fuel to energy systems that are carbon-free is a necessity, thus solutions such as hydrogen economy is required. Especially after recent geopolitical challenges in Europe which could make the energy acquisition a crucial problem. Liquid organic hydrogen carriers (LOHC) are applicable pathways for transitioning H2 into energy and to avoid the storage and transportation limitations of gaseous and liquid H2. Formic acid (FA) is an attractive alternative for such purposes due to its minimal level of toxicity and its significant volumetric storage capacity for H2. In this study, a Life cycle assessment (LCA) of the supply chain involving the Trans-Atlantic export of energy from Canada to Germany is conducted using formic acid as a LOHC and OxFA process to convert biomass to formic acid. The environmental impacts of all units and processes involved in this supply chain are examined, and the results are compared against other traditional systems for hydrogen production. A sensitivity analysis was also performed to recognize the crucial contributors and assess the processes and units that impose considerable influence on the overall environmental impact. / Thesis / Master of Applied Science (MASc) / Hydrogen (H2) plays a crucial role in transitioning from fossil fuel-based to carbon-free energy systems, a shift highlighted by recent geopolitical challenges in Europe. Liquid organic hydrogen carriers (LOHC) offer a solution for hydrogen storage and transport issues associated with its gaseous and liquid states. Formic acid (FA) is particularly promising as a LOHC due to its low toxicity and high hydrogen storage capacity. This study conducts a Life Cycle Assessment (LCA) of a supply chain that uses formic acid to export energy from Canada to Germany, involving the OxFA process for converting biomass to formic acid. The environmental impacts of all processes in this supply chain are evaluated and compared with traditional hydrogen production methods. Additionally, a sensitivity analysis identifies key contributors and assesses their impact on the overall environmental footprint.

The catalytic decomposition of methane offers an interesting route to obtain a stream of pure COx-free hydrogen and carbon materials in the solid phase with potential applications to improve the viability of the process. In this work, we have studied the kinetics of this process using a silica-supported nickel catalyst in a packed bed reactor. In order to ensure the intrinsic kinetic regime, the effects of external and mass transfer on the overall kinetics were examined at relevant reaction conditions. The external mass transfer was found to affect the kinetics at 500 ⁰C and a space velocity of 80 h–1. The internal mass transfer was found to not limit the kinetics when a catalyst particle size in the range of 1000-2000 µm was used. Within the intrinsic kinetic regime, we found that the reaction order with respect to methane is in the range of 0.77-0.94, the activation energy is 110 kJ mol–1 and the rate determining step is the dissociation of the first C-H bond. In addition, the kinetics of the catalyst deactivation follows a first-order behavior with respect to the activity of the catalyst, with an activation energy of 125 kJ mol–1. At the end of the study, a mathematical model for the best-fit model was found using MATLAB. With the whole set of data, the best fit is obtained with a Langmuir-Hinshelwood type rate law.

Tendo em vista a Economia do Hidrogênio e sua infinidade de possibilidades, este trabalho estuda a geração de hidrogênio utilizando a energia solar fotovoltaica. Tendo em vista o consumo mundial de energia crescente, novos métodos de produção energética tem que ser levados em consideração, como o fato do hidrogênio ser um vetor energético de baixo impacto ambiental. Por outro lado, as reservas de combustíveis fósseis não serão capazes de satisfazer essa demanda em longo prazo e seu uso contínuo produz efeitos colaterais, como a poluição que ameaça a saúde humana e os gases de efeito estufa associados à mudança climática. No contexto do Brasil, a eletrólise da água combinada com as energias renováveis e células a combustível seriam uma boa base para melhorar o fornecimento de energia distribuída. Propõe-se, no presente trabalho, produzir hidrogênio por energia renovável, especificamente pelo acoplamento direto de um gerador fotovoltaico a um eletrolisador alcalino de água experimental, concebido localmente. Busca-se entender as características inerentes da interação desses dispositivos, encontrar as eficiências de cada etapa do sistema montado, assim como a eficiência global, adquirindo uma noção mais precisa e prática do uso da energia solar fotovoltaica na alimentação de um eletrolisador. Os resultados experimentais evidenciaram que a transferência da energia do gerador fotovoltaico ao eletrolisador depende fortemente das condições instantâneas climáticas e do modo como estes estão conectados. A interdependência entre variáveis foi reproduzida pelas investigações com destaque para: densidade de corrente no eletrolisador, potencial elétrico, irradiância solar, concentração do eletrólito, área do eletrodo e dimensões da célula eletrolítica. A eficiência do eletrolisador alcançada foi de 21%. A eficiência global (irradiância solar - hidrogênio) foi de 2%. O presente estudo dá subsídios para que seja dimensionado o acoplamento do sistema eletrolisador - gerador FV a partir de uma célula eletrolítica buscando-se minimizar perdas. / In view of the Hydrogen Economy and its endless possibilities, this work studies the hydrogen production using solar photovoltaic energy. With increasing global energy consumption, new methods of energy production have got to be taken into consideration, as hydrogen that it is an energy carrier with low environmental impact. On the other hand, fossil fuel reserves will not be able to meet this demand in the long term and its continuous use produces side effects such as pollution that threatens human health and greenhouse gases which are associated with climate change. For Brazilian energy context, electrolysis combined with renewable power source and fuel cell power generation would be a good basis to improve the distributed energy supply. It is proposed in this paper, to produce hydrogen by a direct coupling of a PV array with an experimental alkaline electrolyzer designed locally. It seeks to understand the inherent characteristics of the interaction of these energy forms, find the efficiencies of each step of the assembled system, as well as the global efficiency, acquiring a more precise notion and practice of the use of solar photovoltaic coupled with an electrolyzer. The experimental results showed that the transfer of energy from the PV array to the electrolyzer depends heavily on instant climatic conditions and how they are connected. The interdependence between variables was reproduced by the investigations, considering especially: current density, electric potential, solar irradiance, concentration of electrolyte, the electrode area and size of the electrolytic cell. The electrolyzer achieved an efficiency of 21%, approximately one-third of a commercial electrolyser efficiency. The overall efficiency (sol-hydrogen) was 2%. The present study gives subsidies to design an electrolyser PV generator system based on a given electrolytic cell seeking low losses.

Tendo em vista a Economia do Hidrogênio e sua infinidade de possibilidades, este trabalho estuda a geração de hidrogênio utilizando a energia solar fotovoltaica. Tendo em vista o consumo mundial de energia crescente, novos métodos de produção energética tem que ser levados em consideração, como o fato do hidrogênio ser um vetor energético de baixo impacto ambiental. Por outro lado, as reservas de combustíveis fósseis não serão capazes de satisfazer essa demanda em longo prazo e seu uso contínuo produz efeitos colaterais, como a poluição que ameaça a saúde humana e os gases de efeito estufa associados à mudança climática. No contexto do Brasil, a eletrólise da água combinada com as energias renováveis e células a combustível seriam uma boa base para melhorar o fornecimento de energia distribuída. Propõe-se, no presente trabalho, produzir hidrogênio por energia renovável, especificamente pelo acoplamento direto de um gerador fotovoltaico a um eletrolisador alcalino de água experimental, concebido localmente. Busca-se entender as características inerentes da interação desses dispositivos, encontrar as eficiências de cada etapa do sistema montado, assim como a eficiência global, adquirindo uma noção mais precisa e prática do uso da energia solar fotovoltaica na alimentação de um eletrolisador. Os resultados experimentais evidenciaram que a transferência da energia do gerador fotovoltaico ao eletrolisador depende fortemente das condições instantâneas climáticas e do modo como estes estão conectados. A interdependência entre variáveis foi reproduzida pelas investigações com destaque para: densidade de corrente no eletrolisador, potencial elétrico, irradiância solar, concentração do eletrólito, área do eletrodo e dimensões da célula eletrolítica. A eficiência do eletrolisador alcançada foi de 21%. A eficiência global (irradiância solar - hidrogênio) foi de 2%. O presente estudo dá subsídios para que seja dimensionado o acoplamento do sistema eletrolisador - gerador FV a partir de uma célula eletrolítica buscando-se minimizar perdas. / In view of the Hydrogen Economy and its endless possibilities, this work studies the hydrogen production using solar photovoltaic energy. With increasing global energy consumption, new methods of energy production have got to be taken into consideration, as hydrogen that it is an energy carrier with low environmental impact. On the other hand, fossil fuel reserves will not be able to meet this demand in the long term and its continuous use produces side effects such as pollution that threatens human health and greenhouse gases which are associated with climate change. For Brazilian energy context, electrolysis combined with renewable power source and fuel cell power generation would be a good basis to improve the distributed energy supply. It is proposed in this paper, to produce hydrogen by a direct coupling of a PV array with an experimental alkaline electrolyzer designed locally. It seeks to understand the inherent characteristics of the interaction of these energy forms, find the efficiencies of each step of the assembled system, as well as the global efficiency, acquiring a more precise notion and practice of the use of solar photovoltaic coupled with an electrolyzer. The experimental results showed that the transfer of energy from the PV array to the electrolyzer depends heavily on instant climatic conditions and how they are connected. The interdependence between variables was reproduced by the investigations, considering especially: current density, electric potential, solar irradiance, concentration of electrolyte, the electrode area and size of the electrolytic cell. The electrolyzer achieved an efficiency of 21%, approximately one-third of a commercial electrolyser efficiency. The overall efficiency (sol-hydrogen) was 2%. The present study gives subsidies to design an electrolyser PV generator system based on a given electrolytic cell seeking low losses.

Submitted by Maicon Juliano Schmidt (maicons) on 2015-04-24T18:31:32Z No. of bitstreams: 1 Sérgio Aldrighi Raffi.pdf: 650009 bytes, checksum: 4e79b9049a00c613c2000ad34bab0732 (MD5) / Made available in DSpace on 2015-04-24T18:31:32Z (GMT). No. of bitstreams: 1 Sérgio Aldrighi Raffi.pdf: 650009 bytes, checksum: 4e79b9049a00c613c2000ad34bab0732 (MD5) Previous issue date: 2012-04-29 / Milton Valente / O objetivo desta pesquisa foi analisar a política de investimento estatal na geração de hidrogênio no Brasil no período 2002-2010. A partir da metodologia de pesquisa bibliográfica, constatou-se que os investimentos brasileiros em hidrogênio estão direcionados para dois segmentos: gerar energia nas células a combustível para suprir veículos e unidades estacionárias e gerar hidrogênio com o objetivo de produzir um combustível com um menor teor de enxofre. Por fim, a preocupação com o meio ambiente tem suscitado a procura por combustíveis mais eficientes e menos poluentes. Neste sentido, os investimentos estatais brasileiros em hidrogênio estão buscando a redução dos impactos ambientais ocasionados por combustíveis fósseis. / The objective of this research was to analyze the policy of state investment in hydrogen generation in Brazil in the period 2002-2010. From the research methodology literature, it was found that Brazilian investments in hydrogen are directed to two segments: power generation in fuel cells to supply vehicles and stationary units and generate hydrogen with the goal of producing a fuel with a lower content of sulfur. Finally, concern for the environment has raised the demand for more fuel efficient and less polluting. In this sense, the Brazilian state investment in hydrogen are seeking to reduce the environmental impacts caused by fossil fuels.

This thesis concerns the design, implementation and operation of a hydrogen energy storage facility that has been added to an existing renewable energy system at West Beacon Farm, Leicestershire, UK. The hydrogen system consists of an electrolyser, a pressurised gas store and fuel cells. At times of surplus electrical supply, the electrolyser converts electrical energy into chemical energy in the form of hydrogen. This hydrogen is stored until there is a shortage of electrical energy to power the loads on the system, at which point it is reconverted back to electricity by the process of reverse-electrolysis that takes place within a fuel cell. The renewable energy sources, supplying electrical power to domestic and office loads at the site, are photovoltaic, wind and micro-hydroelectric. This work is being carried out through a project, conceived and overseen by the author, known as the Hydrogen and Renewables Integration (HARI) project. The purpose of this study is to demonstrate and gain experience in the integration of hydrogen energy storage with renewable energy systems and, most importantly, to develop software models that could be used for the design of future systems of this type in a range of applications. Effective models have been created and verified against the real-world operation of the system. These models have been largely completed, although some minor details remain unfinished as the are dependant upon studies linked to this one which are yet to be concluded. Subject to some fine tuning that this would entail, then, the models can be used to design a stand-alone, integrated hydrogen and renewable energy system, where only the load profile and weather conditions of a site are known. Significant practical experience has been gained through the design, installation and two years' of operation of the system. Many important insights have been obtained in relation to the integration of the system and the design and operation of its components.

No description available.