この論文では従来電力系統から自立的に利用出来る太陽エネルギー及び燃料電池コジェネレーションシステムの徹底的な解析が述べられている。開発した水素マイクログリッドの燃料依存を最小化にする数理モデルを利用し日本社会でのさまざまなシナリオのシミュレーションが行なわれた。こういうシステムの実現性が従来水素燃料供給方法の審査及び日本の中型離島の事例研究で評価された。経済的な分析によって石油の価格が高い遠隔な地域では水素マイクログリッドは競争力があると分かった。 / This thesis presents a thorough analysis on energy supply systems using solar energy and fuel cell cogeneration systems that can operate reliably and independently from the main power grid. A mathematical model to maximize fuel independence for hydrogen micro-grids is developed and simulated for various scenarios in Japanese communities. The viability of implementing such systems is assessed with a review of available hydrogen supply channels, and a study case for a remote Japanese island of medium size. An economic analysis of this study suggests that hydrogen micro-grids are economically competitive for energy supply in remote areas where oil prices are high. / 博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University

This thesis studies preconditions for clean hydrogen energy deployment in energy systems of Spain, Sweden, The UK, and China, considering these countries' geographical, political, and economic peculiarities. Countries' readiness for hydrogen energy uptake assessment is based on a comprehensive analysis of energy systems in selected countries by taking an integrated whole-system approach analyzing hydrogen supply in different infrastructure configurations as well as hydrogen transportation and storage and hydrogen use in the energy ecosystem. The readiness index of each country is evaluated in technological, political, societal, and economic dimensions, which are interdependent and influence not only each other, but the entire outcome of the energy transition phenomena studied in this thesis. The analysis concludes that the political dimension is the dominant one, as the government has the power to steer finance toward a green transition, making the desired change, such as clean hydrogen energy industry formation in the country, happen. Current energy transition entails economic and institutional change and deep industrial restructuring, all of which require specific policy instruments and conditionalities, balancing risks and behaviours in the process of the energy transition. Based on the results of this study, the UK and China have the highest political readiness among the analyzed countries, which also results in their higher economic, technology, and societal readiness levels.

In the area of sustainable energy, a major focus has been to design robust electrocatalysts that can be used for the electrolysis of water to produce H2 with a sustainable energy source such as solar. Sustainable H2 generation would potentially be a prelude to the adoption of a hydrogen economy, allowing the phasing out of fossil fuels as a primary fuel source. Toward this end, there is a global research effort to develop electrocatalysts that would facilitate the kinetics of the two half-reactions that make up the water-splitting process: the anodic oxygen evolution reaction (OER) and the cathodic hydrogen evolution reaction (HER). A challenge is to develop active electrocatalysts that are largely composed of earth-abundant elements and show catalytic stability during water splitting at low pH, where the scientific community feels that commercial electrolysis will operate most efficiently. Currently, iridium oxide (IrO2) is being looked at for low pH water splitting because of its stability at low pH, but its relative scarcity (e.g., it is a precious metal) may well make it an unacceptable choice in the long run.In this dissertation, we focus on understanding the scientific issues that will allow the development of earth-abundant catalysts that contain a loading of Ir that is low as possible, while maintaining suitable activity and stability. We began by synthesizing a series of Ir-based OER electrocatalysts by incorporating varying amounts of Ir into 2D layered MnO2 (birnessite, nominally δ-MnO2) and 3D MnO2 (pyrolusite, β-MnO2) phases. The Ir-incorporated δ-MnO2 (Ir/δ-MnO2) electrocatalysts with 16-22 wt% Ir were synthesized by a wet chemical method using a ligating agent, such that Ir was present on the surface and partially intercalated into the interlayer of δ-MnO2. Ir-incorporated β-MnO2 (Ir/β-MnO2) was prepared for the first time via a thermally induced phase transition of Ir/δ-MnO2. This phase transition of δ-MnO2 to β-MnO2 was facilitated by the presence of Ir in the structure, as both Ir in IrO2 and Mn in β-MnO2 could adopt the more thermodynamically stable rutile structure. Extended X-ray absorption fine structure (EXAFS) of Ir/β-MnO2 showed that the catalyst consisted of Ir substituted into the crystalline β-MnO2 lattice, additionally, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and scanning electron microscopy (SEM) imaging revealed micron-sized particles with non-uniform distribution of Ir in the MnO2. In 0.5 M H2SO4 electrolyte, 22 wt% Ir/β-MnO2 (60 〖μg〗_Ir cm_geo^(-2)) resulted in the most active catalyst with an η@10 (overpotential at 10 mA cm_geo^(-2)) of 337 mV and stability of 6 h. This electrocatalyst outperformed a commercial IrO2 on a per Ir mass basis. EXAFS, HAADF-STEM and X-ray absorption near edge structure (XANES) showed that 22 wt% Ir/β-MnO2 had a strained structure containing ~41% Mn3+, an OER active species, along with a modified Ir bonding due to the presence of Ir-O-Ir and Ir-O-Mn. Density functional theory (DFT) computation has demonstrated that this modified bonding environment in Ir/β-MnO2 has contributed to enhancing the thermodynamic stability of the structure. Furthermore, the literature suggests that the presence of Ir-O-Mn bond can favorably tune the d-orbital energy of Ir, enabling superior performance in the Ir/β-MnO2 compared to IrO2. The thesis research also included the investigation of the activity and stability of Ir/β-MnO2 that was synthesized via a novel strategy. The resulting material maintained a homogeneous distribution of Ir in the MnO2 lattice and exhibited excellent OER activity and stability. A surfactant-assisted (SA) synthesis method was carried out to achieve uniform doping of 22-28 wt.% Ir in 3D MnO2 (ramsdellite, R-MnO2). Upon annealing, Ir/R-MnO2 transformed to Ir/β-MnO2 (SA), composed of nano-sized particles. Electrochemical studies in 0.5 M H2SO4 showed that, Ir/β-MnO2 (SA) with 75.6 〖µg〗_Ir cm_geo^(-2) exhibited an η of 327 mV and exceptional stability (up to 50 h). At similar Ir mass loadings, the Ir/β-MnO2 (SA) outperformed Ir/R-MnO2 (SA) and commercial IrO2. This enhanced activity and stability was attributed to a thermodynamically stable structure composed of uniform distribution of Ir (Ir-O-Mn) in the MnO2 lattice. Overall, the research results presented in this dissertation contributed towards designing a novel class of Ir-MnO2 catalysts, which potentially will point the scientific community in the right direction for designing future noble metal-incorporated earth-abundant metal oxides for electrocatalytic energy conversion reactions. / Chemistry

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-03-14T21:37:10Z No. of bitstreams: 1 NATÁLIA DE OLIVEIRA SANTIAGO - DISSERTAÇÃO PPGEQ 2015..pdf: 2885726 bytes, checksum: 42752aa08c69c959e3a3f1367b0e8e7a (MD5) / Made available in DSpace on 2018-03-14T21:37:10Z (GMT). No. of bitstreams: 1 NATÁLIA DE OLIVEIRA SANTIAGO - DISSERTAÇÃO PPGEQ 2015..pdf: 2885726 bytes, checksum: 42752aa08c69c959e3a3f1367b0e8e7a (MD5) Previous issue date: 2015 / Capes / O uso desenfreado de combustíveis fósseis tem causado problemas climáticos graves em todo o planeta, tais como o aquecimento global e a poluição do ar. Além de seus efeitos negativos perante a natureza, estes acarretam custos cada vez maiores de energia, devido à disponibilidade cada vez menor de reservas de petróleo, de produção e de fornecimento. Nesse contexto o hidrogênio vem a ser um vetor energético, devido a principalmente à sua alta eficiência de conversão, reciclagem e natureza não-poluente. É um combustível que não se encontra na natureza, mas ele pode ser facilmente produzido. Este trabalho apresenta a produção do hidrogênio através da eletrólise da água em meio alcalino (hidróxido de potássio, KOH) num reator de tipo bipolar usando eletrodos de espuma de níquel. A avaliação do reator eletrolítico, constituído de uma célula unitária, foi realizada pelo método estatístico de superfície de resposta visando a otimização dos experimentos através de dois planejamentos com duas variáveis dependentes: a tensão aplicada e a concentração em porcentagem de massa do KOH. A resposta é dada na forma de fluxo de hidrogênio (L/h) com o intuito de analisar o comportamento do reator em diferentes situações. A partir dos parâmetros analisados, foi encontrado o ponto ótimo de funcionamento do reator, obtido com uma concentração de 16,6% em massa de KOH e uma tensão aplicada de 2,6 V, produzindo 0,841 L/h de H2, valor máximo obtido para ambos planejamentos. / The society development is associated to the increasing use of fossil fuels, creating serious climatic problems such as global warning and air pollution. The ecological disasters, like floods and droughts, are a consequence of the increasing release of CO2 and other greenhouse gases. Besides these environmental problems, the costs relied to the extraction, production and supply of oil, are increasing due to its availability. Changes are necessary to control this situation and a way out is the use of another fuel in order to guarantee sustainability. This fuel of the future can be hydrogen, mainly due to its high conversion efficiency, recycling and non-polluting nature. It is particularly attractive as a promising substitute of the fossil fuels. This work presents the production of hydrogen by alkaline water electrolysis (potassium hydroxide, KOH) using nickel foam based electrodes. The evaluation of the electrolytic reactor, consisting of a unit cell, was performed by the statistical method of response surface experiments through two plans with two dependent variables: applied tension and KOH concentration. The response is the hydrogen flow (L/h) in order to analyze the reactor behavior in different situations. The optimum point of the reactor operation for both schedules was obtained with a concentration of 16,6% KOH and an applied voltage of 2.6 V, producing 0,841 L/h of H2.

Purpose of this thesis is wisdom accumulation from current area of energetic use of hydrogen and future systems. In overview is presented possible processes where dominate steam methane reforming. In main part of thesis, steam methane reforming will be analyzed and electrolysis also. Actual results will be discussed. Next part is about energetic use of hydrogen based on thermochemical properties and safety. Used of hydrogen will be divided to areas thermal generation as burner‘s section, electric generation as fuel cell‘s section, mechanical energy as combustion engine’s section and finally chemical transportation of energy. At the end will be made a promising energy systems using hydrogen as fuel which can be applied in a large scale.

M. Tech. (Department of Electronic Engineering, Faculty of Engineering and Technology) --Vaal University of Technology| / Global warming is of increasing concern due to several greenhouse gases. The combustion of fossil fuels is the major contributor to the greenhouse effect. To minimalise this effect, alternative energy sources have to be considered. Alternative energy sources should not only be environmentally friendly, but also renewable and/or sustainable. Two such alternative energy sources are hydrogen and solar energy. The regenerative fuel cell, commonly known as a hydrogen generator, is used to produce hydrogen. The current solar/hydrogen system at the Vaal University of Technology’s Telkom Centre of Excellence makes use of PV array to supply power to an inverter and the inverter is connected to the hydrogen generator. The inverter provides the hydrogen generator with 220VAC. The hydrogen generator has its own power supply unit to convert the AC power back to DC power. This reduces the efficiency of the system because there will be power loss when converting DC power to AC power and back to DC power. The hydrogen generator, however, could be powered directly from a PV array. However, the hydrogen generator needs specific input parameters in order to operate. Three different input voltages with their own current rating are required by the hydrogen generator to operate properly. Thus, a DC-DC power supply unit needs to be designed to be able to output these parameters to the hydrogen generator. It is also important to note that current PV panel efficiency is very low; therefore, the DC-DC power supply unit also needs to extract the maximum available power from the PV array. In order for the DC-DC power supply unit to be able to extract this maximum power, a maximum power point tracking algorithm needs to be implemented into the design. The DC-DC power supply is designed as a switch mode power supply unit. The reason for this is that the efficiency of a switch mode power supply is higher than that of a linear power supply. To reach the objective the following methodology was followed. The first part of the research provided an introduction to PV energy, charge controllers and hydrogen generators. The problem statement is included as well as the purpose of this research and how this research was to be carried out. The second part is the literature review. This includes the background study of algorithms implemented in MPPT’s; it also explains in detail how to design the MPPT DC-DC SMPS. The third part was divided into two sections. The first section is the design, programming and manufacturing of the MPPT DC-DC SMPS. The second section is the simulation of the system as a whole which is the simulation of the PV array connected to the MPPT DC-DC SMPS and the hydrogen generator. The fourth part in the research compared the results obtained in the simulation and practical setup. The last part of the research provided a conclusion along with recommendation made for further research. The simulation results showed that the system works with an efficiency of 40,84%. This is lower than expected but the design can be optimised to increase efficiency. The practical results showed the efficiency to be 38%. The reason for the lower efficiency is the simulation used ideal components and parameters, whereas the practical design has power losses due to the components not being ideal. The design of the DC-DC switch mode power supply, however, indicated that the hydrogen generator could be powered from a PV array without using an inverter, with great success.

Thesis. (M. Tech. (Dept. Electronic Engineering, Faculty of Engineering and Technology))--Vaal University of Technology, 2011. / There are a number of ways to produce hydrogen using solar energy as the primary source. Water electrolysis, which uses solar electrical energy, is the rapidly available process. Hydrogen can be produced by using solar electric energy from photovoltaic (PV) modules for the electrolysis of water without emitting carbon dioxide or requiring fossil fuels. Solar hydrogen energy systems are considered one of the cleanest hydrogen production technologies, where the hydrogen is obtained from sunlight by directly connecting the photovoltaic modules to the hydrogen generator. This dissertation presents a designed solar photovoltaic electrolyser hydrogen production and storage system for various applications such as in the power generation and telecommunications industries. Various experiments were performed on the designed system to ensure its reliability and conformity with theoretical findings. The purity of the generated hydrogen was determined. The relationship between the amount of solar irradiance reaching the surface of the PV panel, the PV panel surface temperature, the PV panel tilt angle and the maximum power point voltage and current of the PV panel array were also considered. The effect of dust on the panel voltage and current outputs was also determined. Finally, the factors to consider when designing a solar photovoltaic electrolyser hydrogen system (based on this study) were enumerated.

Hydrogen and oxygen or air polymer electrolyte membrane fuel cell is one of the most promising electrical energy conversion devices for a sustainable future due to its high efficiency and zero emission. Membrane electrode assembly (MEA), in which electrochemical reactions occur, is stated to be the heart of the fuel cell. The aim of this study was to develop methods for preparation of MEA with alternative polymer electrolyte membranes and compare their performances with the conventional Nafion&reg / membrane. The alternative membranes were sulphonated polyether-etherketone (SPEEK), composite, blend with sulphonated polyethersulphone (SPES), and polybenzimidazole (PBI). Several powder type MEA preparation techniques were employed by using Nafion&reg / membrane. These were GDL Spraying, Membrane Spraying, and Decal methods. GDL Spraying and Decal were determined as the most efficient and proper MEA preparation methods. These methods were tried to improve further by changing catalyst loading, introducing pore forming agents, and treating membrane and GDL. The highest performance, which was 0.53 W/cm2, for Nafion&reg / membrane was obtained at 70 0C cell temperature. In comparison, it was about 0.68 W/cm2 for a commercial MEA at the same temperature. MEA prepared with SPEEK membrane resulted in lower performance. Moreover, it was found that SPEEK membrane was not suitable for high temperature operation. It was stable up to 80 0C under the cell operating conditions. However, with the blend of 10 wt% SPES to SPEEK, the operating temperature was raised up to 90 0C without any membrane deformation. The highest power outputs were 0.29 W/cm2 (at 70 0C) and 0.27 W/cm2 (at 80 0C) for SPEEK and SPEEK-PES blend membrane based MEAs. The highest temperature, which was 150 0C, was attained with PBI based MEA during fuel cell tests.

Mémoire (M.Sc.A)--Université du Québec à Chicoutimi, 1989. / Document électronique également accessible en format PDF. CaQCU

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-03-15T16:40:52Z No. of bitstreams: 1 ALDREANY PEREIRA DO NASCIMENTO - DISSERTAÇÃO PPGEQ 2016..pdf: 4384493 bytes, checksum: 8cf20c9f79749f12b562389c82ec5d3f (MD5) / Made available in DSpace on 2018-03-15T16:40:52Z (GMT). No. of bitstreams: 1 ALDREANY PEREIRA DO NASCIMENTO - DISSERTAÇÃO PPGEQ 2016..pdf: 4384493 bytes, checksum: 8cf20c9f79749f12b562389c82ec5d3f (MD5) Previous issue date: 2016-10-30 / Capes / A crise do petróleo juntamente com a grande necessidade de novas fontes de energias sustentáveis leva ao desenvolvimento de tecnologias mais limpas e eficientes. Neste contexto, as células a combustível aparecem como uma das soluções promissoras para a geração de energia elétrica, tendo como produto da reação, basicamente água e calor. Este trabalho de dissertação consiste na caracterização de uma célula a combustível PEM (Polymer Electrolyte Membrane) alimentada com hidrogênio e ar para a conversão de energia elétrica da energia química contida no gás hidrogênio. A célula a combustível utilizada é de potência nominal de 1 kW, constituída por 72 células ligadas em série com um sistema de controle próprio. A caracterização é feita através da utilização de uma carga resistiva configurável com base num microcontrolador. A partir dos parâmetros registrados (corrente e tensão), a curva de polarização, a densidade de corrente e a eficiência foram calculadas com base nos sistemas de curto circuito ligado e desligado (SCU: ON e SCU: OFF, respectivamente). Os resultados mostram uma potência máxima de saída de aproximadamente 623 W (37,09 V, 16,78 A), e uma densidade de corrente de 209,75 mA/cm2, com uma eficiência operacional em torno de 42 %, com o sistema de SCU: OFF. Para o sistema SCU: ON a potência máxima de saída é em torno de 664 W (39,10 V, 17,81 A) com densidade de corrente de 222,62 mA/cm2 e uma eficiência operacional de 44 %. O sistema de carga variável mostrou-se satisfatório para testar a célula, com um desvio entre a potência nominal e a real inferior a 20 %. Os relativamente baixos valores de eficiência do sistema (<20 %) são explicados pelo tempo de vida da célula. / The use of new sustainable energy sources is dependent on the development of clearer and more efficient technologies. Therefore, the fuel cells appear like a promising solution for the electrical energy generation, since that the reaction products are water and heat. This work plans to characterize a polymer electrolyte membrane fuel cell, feeding with hydrogen and air. The tested 1 kW nominal power fuel cell is constituted by 72 cells connected in serial. The characterization is made using a variable resistive charge system. It comprises 64 resistors (20 W) together with blowers for cooling. From the electrical parameters (voltage and current), the polarization curve, the current density and the efficiency of the fuel cell were calculated, with the short-circuit system on and off (SCU: ON and SCU: OFF). A maximum output power of 623 W (37.09 V and 16.78 A), with a current density of approx. 209.75 mA/cm2 and an efficiency around 42 % are obtained when the SCU is OFF. With the SCU: ON, the values are 664 W (39.10 V and 17.81 A), 222.62 mA/cm2 and 44 %, respectively. The results show that the resistive charge system is appropriate to test this kind of fuel cell. The low global efficiency values (< 20 %) can be explained by the fuel cell age.