Dissertations / Theses on the topic 'Solar hydrogen'
To see the other types of publications on this topic, follow the link: Solar hydrogen.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Solar hydrogen.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Mahoney, Luther. "Solar hydrogen and solar electricity using mesoporous materials." Thesis, University of South Dakota, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3723927.
Full textAbstract:
The development of cost-effective materials for effective utilization of solar energy is a major challenge for solving the energy problems that face the world. This thesis work relates to the development of mesoporous materials for solar energy applications in the areas of photocatalytic water splitting and the generation of electricity. Mesoporous materials were employed throughout the studies because of their favorable physico-chemical properties such as high surface areas and large porosities. The first project was related to the use of a cubic periodic mesoporous material, MCM-48. The studies showed that chromium loading directly affected the phase of mesoporous silica formed. Furthermore, within the cubic MCM-48 structure, the loading of polychromate species determined the concentration of solar hydrogen produced. In an effort to determine the potential of mesoporous materials, titanium dioxide was prepared using the Evaporation-Induced Self-Assembly (EISA) synthetic method. The aging period directly determined the amount of various phases of titanium dioxide. This method was extended for the preparation of cobalt doped titanium dioxide for solar simulated hydrogen evolution. In another study, metal doped systems were synthesized using the EISA procedure and rhodamine B (RhB) dye sensitized and metal doped titania mesoporous materials were evaluated for visible light hydrogen evolution. The final study employed various mesoporous titanium dioxide materials for N719 dye sensitized solar cell (DSSC) materials for photovoltaic applications. The materials were extensively characterized using powder X-ray diffraction (XRD), nitrogen physisorption, diffuse reflectance spectroscopy (DRS), UV-Vis spectroscopy, Fourier-Transform-Infrared Spectroscopy (FT-IR), Raman spectroscopy, chemisorption, photoluminescence (PL), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). In addition, photoelectrochemical measurements were completed using current-voltage (I-V) curves, external quantum efficiency (EQE) curves, electrochemical impedance spectroscopy (EIS), and transient spectroscopy. The thesis work presented provides a better understanding of the role of mesoporous materials for solar hydrogen and solar electricity production.
2
Uyar, Basar. "Hydrogen Production By Microorganisms In Solar Bioreactor." Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/2/12609252/index.pdf.
Full textAbstract:
The main objective of this study is exploring the parameters affecting photobiological hydrogen production and developing anaerobic photobioreactor for efficient photofermentative hydrogen production from organic acids in outdoor conditions. Rhodobacter capsulatus and Rhodobacter sphaeroides strains were used as microorganisms.
EU project &ldquoHyvolution&rdquo
targets to combine thermophilic fermentation with photofermentation for the conversion of biomass to hydrogen. In this study, the effluent obtained by dark fermentation of Miscanthus hydrolysate by T. neapolitana was fed to photobioreactor for photofermentation by R. capsulatus. Hydrogen yield was 1.4 L/Lculture showing that the integration of dark and photofermentation is possible. Innovative elements were introduced to the photobioreactor design such as removal of argon flushing. An online gas monitoring system was developed which became a commercial product. It was found that the light intensity should be at least 270 W/m2 on the bioreactor surface for the highest hydrogen productivity and the hydrogen production decreased by 43 % if infrared light was not provided to the bioreactor. Scale-up of photofermentation process to 25L was achieved yielding 27L hydrogen in 11 days by R. capsulatus on acetate/lactate/glutamate (40/7.5/2 mM) medium. The outdoor application of the system was made. Shading and water spraying were adapted as cooling methods for controlling the temperature of the outdoor bioreactor. It was found that uptake hydrogenase deleted mutant of R. capsulatus show better hydrogen productivity (0.52 mg/L.h) compared to the wild type parent (0.27 mg/L.h) in outdoor conditions. It was also shown that the hydrogen production depended on the sunlight intensity received.
3
Bourgeteau, Tiphaine. "Development of hybrid photocathodes for solar hydrogen production." Palaiseau, Ecole polytechnique, 2015. https://tel.archives-ouvertes.fr/tel-01215429v1/document.
Full textAbstract:
L’utilisation des énergies renouvelables, qui sont intermittentes, à l’égal des énergies fossiles (échelle du TW) doit passer par leur conversion et stockage en un vecteur transportable. L’hydrogène semble le vecteur énergétique idéal qui peut être produit à partir de l’eau et de l’énergie solaire. Ce carburant peut ainsi être stocké, transporté puis utilisé à la demande en le combinant avec l’oxygène dans une pile à combustible. Les cellules photo-électrochimiques (PEC) utilisées pour la conversion ne sont actuellement pas rentables car les matériaux majoritairement utilisés pour leur fabrication, tels que le platine et les semiconducteurs cristallins, sont rares ou chers. Le point clé est de trouver des matériaux qui soient disponibles en grande quantité et facilement mis en forme. Ce travail de thèse concerne le développement d’une photocathode sans matériau rare pour la photoproduction de H2 via la réduction des protons à partir de l’énergie solaire et de l’eau. Pour cela, une cellule solaire à hétérojonction polymère-fullerène (P3HT:PCBM) a été couplée directement à un catalyseur sans métal précieux, MoS3. La cellule solaire absorbe les photons, et les électrons photogénérés sont ensuite acheminés jusqu’au catalyseur qui les utilise pour produire l’hydrogène. Après avoir étudié chacun des matériaux (cellule solaire et catalyseur) séparément et vérifié le bon alignement des niveaux énergétiques, les premiers assemblages ont été faits par des procédés en solution. Les méthodes de dépôt ont dû être adaptées en fonction de la nature des matériaux. Ainsi, le spin-coating et le spray ont été utilisés respectivement pour déposer la partie photovoltaïque et le catalyseur. Les caractérisations photo-électrochimiques mises en place ont permis de mettre en évidence la présence d’un photo-courant (100 µA cm–2) correspondant à la production d’hydrogène, qui a été analysé par chromatographie en phase gazeuse. Ces résultats ont permis de montrer la viabilité des photocathodes hybrides sans matériau noble. Afin d’augmenter les performances des photocathodes, de nouvelles configurations ont été conçues. Dans un premier temps des matériaux d’interface entre la couche mince photovoltaïque et le catalyseur ont été étudié (couche extractrice d’électrons, CEE) pour améliorer la collection des électrons photogénérés par le catalyseur. Parmi les métaux étudiés, l’aluminium protégé par le titane a permis d’atteindre des photocourants de 10 mA cm–2. Cependant la présence de l’aluminium induisait une instabilité en milieu aqueux, aussi des oxydes (TiOx) et des matériaux organiques (fullerène C60 et graphène) ont été envisagés. Le TiOx n’a permis qu’une légère amélioration par rapport aux photocathodes sans CEE, tandis que le C60 a permis d’atteindre 5 mA cm–2 mais avec une stabilité moindre par rapport aux CEE métalliques. L’origine de l’amélioration des performances a été attribuée à l’isolement de la jonction photovoltaïque par rapport à l’électrolyte. Dans une deuxième approche, la couche extractrice de trous (CET) située entre l’électrode transparente et le P3HT:PCBM a été remplacée par des oxydes amorphes (oxyde de graphène (GO), MoOx, NiOx). Ce changement a permis la réalisation de photocathodes performantes et stables pendant plusieurs heures, avec des températures de dépôt ne dépassant pas 150 °C dans le cas du MoOx et du GO. L’augmentation des performances semblant aller de pair avec l’augmentation du travail de sortie de la CET, il a été suggéré que la différence des niveaux de Fermi de la CET et de l’électrolyte avait un impact sur la capacité de la photocathode à séparer les charges et les utiliser pour la photocatalyse. Les photocathodes avec MoOx (matériau testé avec le plus grand travail de sortie) ont les meilleurs rendements (plusieurs mA cm–2 et un photovoltage de 0. 6 V), et présentent une plus grande stabilité par rapport aux photocathodes ayant une CTE métalliqueOne of the challenges of the 21st century is to produce clean and inexpensive energy at the TW scale to face the increasing energy demand and the global climate change. Because renewable energies are intermittent, they must be converted and stored in order to use them at the same scale of fossil energies. Hydrogen appears to be an ideal energy carrier when it is produced from water and sunlight. This fuel can be stored, transported and use on-demand by its combination with oxygen, for example in a fuel cell. Photo-electrochemical (PEC) cells able to carry out the photo-electrolysis of water are not yet cost-effective, because most of the materials used for their fabrication are rare or expensive (platinum, crystalline semiconductors). Producing hydrogen in a PEC cell at industrial scale depends on the finding of readily-available and easily-processed materials. In this thesis, the development of a noble-metal free hydrogen-evolving photocathode was undertaken, to reduce protons from light and acidic water. The photo-converting unit was based organic semiconductors organized in a polymer-fullerene bulk-heterojunction layer (P3HT:PCBM) coupled to amorphous molybdenum sulfide (MoS3) as a catalyst. In the device, the P3HT:PCBM layer absorbs the photons and the photogenerated electrons are then transported to the interface with the catalyst, which uses the electrons to produce hydrogen. After studying each material (catalyst and solar cell) separately and checking the alignment of their energy levels, the first assemblies were made by solution processes. The deposition methods were adapted depending on the nature of the materials. Spin-coating and spray were used for the deposition of the light-harvesting unit and the catalyst, respectively. With the photo-electrochemical characterization setup, a photocurrent of up to 100 µA cm–2 was obtained, corresponding to production of hydrogen, as analyzed by gas chromatography. These first results proved the viability of the concept of this hybrid noble-metal free photocathode. In order to improve the photocathode performance, new configurations were designed. Firstly, interfacial materials placed between P3HT:PCBM and MoS3 (electron-extracting layer, EEL) were studied to improve charge collection by the catalyst. Among studied materials, photocathodes with titanium-protected aluminum reached up to 10 mA cm–2 of photocurrent. The presence of aluminum induced instability in aqueous media, so that oxides (TiOx) and organic materials (C60 fullerene and graphene) were considered. TiOx brought only a slight improvement compared to photocathodes without EELs, while C60 allowed to reach 5 mA cm–2 but with a lower stability compared to metallic EELs. The origin of the increased performances with EELs was attributed to the burying of the photovoltaic junction, removing the influence of the electrolyte. Secondly, the material between the transparent electrode and the photovoltaic part, i. E. The hole-extracting layer (HEL), was replaced by amorphous oxides (graphene oxide (GO), MoOx, NiOx). It led to the fabrication of performant photocathodes, stables for several hours, by process temperatures below 150 °C in the case of MoOx and GO. The increase of the performance seemed to be related to the increase of the HEL work function, leading to the suggestion that the Fermi level difference between the HEL and the electrolyte has an impact on the capacity of the photocathode to separate the charges and use them for photocatalysis. The most performant photocathodes (several mA cm–2 and 0. 6 V of photovoltage) were the one with MoOx, i. E. The material with the largest work function, and had a much better stability than the photocathodes with metallic EELs
4
Benton, Jonathan. "Novel III-nitride semiconductors for solar hydrogen production." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/7644/.
Full textAbstract:
III-nitride materials are crucially becoming the most important and promising class of semiconductors for future optoelectronic devices including solid state lighting and solar energy applications. Presently, there are still many challenges in regards to the wide scale uptake of these devices, including low efficiencies and short lifetimes. Despite the ideal properties of InGaN for water splitting, there are still very few reports utilising these semiconductors. This thesis investigates GaN and InGaN based structures for water splitting. Initially focussing on the fabrication of nanorods via the use of a self-organised nickel mask, where diameter and height of the structures have been optimised. As a result, the surface area of the device increases dramatically leading to an enhancement in photocurrent compared to as-grown planar devices. Alongside this, the fabricated nanostructures allow for an enhancement in electron-hole separation and an increase in the hydrogen generation rate. The lifetime of the fabricated devices is also discussed. Prolonged exposure of the nanostructured devices results in the degradation and etching of the InGaN material. The addition of a secondary semiconductor material, NiO, acts as a reaction site for photogenerated holes preventing the oxidation and dissolution of InGaN devices in the experimental electrolytes, increasing the device lifetime. Furthermore, a photoelectrochemical etch technique is implemented to create a porous device structure. The nanoporous network in the structure shortens the required diffusion length of the photogenerated carriers to values close to that of InGaN. An enhancement in photocurrent and hydrogen production has been observed due to the nanoporous structure.
5
Morton, Craig D. "Development of novel photocatalysts for solar hydrogen production." Thesis, University of Greenwich, 2012. http://gala.gre.ac.uk/3630/.
Full textAbstract:
Photocatalysts, typically nanoparticulate semiconductors, can be used to split water into hydrogen and oxygen. If solar light is used for this, it opens the possibility of a renewable source of hydrogen. However, extension of photocatalytic response into the visible region of the solar spectrum is required. A new visible light activated photocatalyst is reported herein. Iron vanadate, FeVO4, was first synthesised using a low-temperature, aqueous precipitation reaction. The material prepared was found to be predominantly amorphous and required thermal treatment. The resultant material was characterised using XRD, SEM, IR spectroscopy, Raman spectroscopy and magnetic susceptibility measurements. Materials annealed above 600 °C were found to consist mainly of FeVO4, although traces of hematite were found. Diffuse-reflectance UV spectroscopy and subsequent Tauc plots revealed a band gap of ca. 2.00 eV corresponding to an indirect transition. Photocurrent-voltage characteristics recorded under simulated solar illumination indicate that photocurrents are sensitive to annealing temperature and the thickness of the deposit. However, although photocurrent-voltage plots show that electrodes prepared from a suspension of nanoparticulate FeVO4 powders were photo-responsive, these electrodes were found to be mechanically unstable. Films were prepared directly onto the electrode by using a sol-gel approach. Raman spectroscopy, XRD and diffuse-reflectance UV-visible spectroscopy has revealed the electrode films to be crystalline in nature, significantly more stable, with an indirect band gap in the visible region of 2.00 eV. Higher photocurrent densities were observed for the sol-gel prepared electrodes compared to those deposited from aqueous suspensions of pre-formed powders. It was determined that these photocurrents were dependant on film thickness, annealing time and temperature, and sol pH.
6
Uluoglu, Arman. "Solar-hydrogen Stand-alone Power System Design And Simulations." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12611884/index.pdf.
Full textAbstract:
In this thesis, solar-hydrogen Stand-Alone Power System (SAPS) which is planned to be built for the emergency room of a hospital is designed. The system provides continuous, off-grid electricity during the whole period of a year without any external electrical power supply. The system consists of Photovoltaic (PV) panels, Proton Exchange Membrane (PEM) based electrolyzers, PEM based fuel cells, hydrogen tanks, batteries, a control mechanism and auxiliary equipments such as DC/AC converters, water pump, pipes and hydrogen dryers. The aim of this work is to investigate the optimal system configuration and component sizing which yield to high performance and low cost for different user needs and control strategies. TRNSYS commercial software is used for the overall system design and simulations.
Numerical models of the PV panels, the control mechanism and the PEM electrolyzers are developed by using theoretical and experimental data and the models are integrated into TRNSYS. Overall system models include user-defined components as well as the default software components. The electricity need of the emergency room without any shortage is supplied directly from the PV panels or by the help of the batteries and the fuel cells when the solar energy is not enough. The pressure level in the hydrogen tanks and the overall system efficiency are selected as the key design parameters. The major component parameters and various control strategies affecting the hydrogen tank pressure and the system efficiency are analyzed and the results are presented.
7
Liu, Simin. "Photocatalytic hydrogen production with iron oxide under solar irradiation." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/43666/1/Simin_Liu_Thesis.pdf.
Full textAbstract:
As solar hydrogen is a sustainable and environmental friendly energy carrier, it is considered to take the place of fossil fuels in the near future. Solar hydrogen can be generated by splitting of water under solar light illumination. In this study, the use of nanostructured hematite thin-film electrodes in photocatalytic water splitting was investigated. Hematite (á-Fe2O3) has a narrow band-gap of 2.2 eV, which is able to utilise approximately 40% of solar radiation. However, poor photoelectrochemical performance is observed for hematite due to low electrical conductivity and a high rate of electron-hole recombination. An extensive review of useful measures taken to overcoming the disadvantages of hematite so as to enhance its performance was presented including thin-film structure, nanostructuring, doping, etc. Since semiconductoring materials which exhibit an inverse opal structure are expected to have a high surface-volume ratio, unique optical characteristics and a shorter distance for photogenerated holes to travel to the electrode/electrolyte interface, inverse opals of hematite thin films deposited on FTO glass substrate were successfully prepared by doctor blading using PMMA as a template. However, due to the poor adhesion of the films, an acidic medium (i.e., 2 M HCl) was employed to significantly enhance the adhesion of the films, which completely destroyed the inverse opal structure. Therefore, undoped, Ti and Zn-doped hematite thin films deposied on FTO glass substrate without an inverse opal structure were prepared by doctor blading and spray pyrolysis and characterised using SEM, EDX, XRD, TGA, UV-Vis spectroscopy and photoelectrochemical measurements. Regarding the doped hematite thin films prepared by doctor blading, the photoelectrochemical activity of the hematite photoelectrodes was improved by incorporation of Ti, most likely owing to the increased electrical conductivity of the films, the stabilisation of oxygen vacancies by Ti4+ ions and the increased electric field of the space charge layer. A highest photoresponse was recorded in case of 2.5 at.% Ti which seemed to be an optimal concentration. The effect of doping content, thickness, and calcination temperature on the performance of the Ti-doped photoelectrodes was investigated. Also, the photoactivity of the 2.5 at.% Ti-doped samples was examined in two different types of electrochemical cells. Zn doping did not enhance the photoactivity of the hematite thin films though Zn seemed to enhance the hole transport due to the slow hole mobility of hematite which could not be overcome by the enhancement. The poor performance was also obtained for the Ti-doped samples prepared by spray pyrolysis, which appeared to be a result of introduction of impurities from the metallic parts of the spray gun in an acidic medium. Further characterisation of the thin-film electrodes is required to explain the mechanism by which enhanced performance was obtained for Ti-doped electrodes (doctor blading) and poor photoactivity for Zn and Ti-doped samples which were synthesised by doctor blading and spray pyrolysis, respectively. Ti-doped hematite thin films will be synthesised in another way, such as dip coating so as to maintain an inverse opal structure as well as well adhesion. Also, a comparative study of the films will be carried out.
8
Udiaver, Rahul Gaurang. "Thermo-economic study and optimization of solar hydrogen generation plants." Thesis, KTH, Kraft- och värmeteknologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-149942.
Full textAbstract:
The main goal of this project is to calculate the maximum theoretical efficiencies of a solar hydrogen generation plant and also to carry out economic analysis of the solar and chemical plants. The final combined results would comprise the optimized values of the annual hydrogen production with respect to the overall costs. Another area of investigation is the effect of temperature and partial pressure of oxygen in the reduction of the chemical reactor. This will lead to the optimal values of temperature and oxygen partial pressure, hence determining maximal hydrogen production. The redox pairs under study are Cerium IV oxide CeO2, Zinc in the form ZnO/Zn , Ferrites as Fe3O4/FeO and Tungsten as WO3/W.
9
Onigbajumo, Adetunji. "Integration of concentrated solar thermal energy for industrial hydrogen production." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/235889/1/Adetunji%2BOnigbajumo_Thesis%281%29.pdf.
Full textAbstract:
The research demonstrated a balanced process, energy, and techno-economic argument for the utilisation of concentrated solar thermal energy, essentially, for hydrogen production and other industrial process systems. The representative case studies undertaken in the research addressed process and solar thermal energy modelling, energy integration, process optimisation, exergy assessment, and techno-economic evaluation as it relates to renewable hydrogen and hydrogen-based fuel production. The research established that economic assessment studies, process-energy configuration, choice of renewable energy, and mixed energy options are key to the shift from fossil fuel to green energy and industrial production to significantly reduce the impact of climate change.
10
Clarke, Daniel. "Stand-alone solar-pv hydrogen energy systems incorporating reverse osmosis." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2015. https://ro.ecu.edu.au/theses/1750.
Full textAbstract:
The world’s increasing energy demand means the rate at which fossil fuels are consumed has increased resulting in greater carbon dioxide emissions. For many small (marginalised) or coastal communities, access to potable water is limited alongside good availability of renewable energy sources (solar or wind). One solution is to utilise small-scale renewably powered stand-alone energy systems to help supply power for everyday utilities and to operate desalination systems serving potable water (drinking) needs reducing diesel generator dependence. In such systems, on-site water production is essential so as to service electrolysis for hydrogen generation for Proton Exchange Membrane (PEM) fuel cells. Whilst small Reverse Osmosis (RO) units may function as a (useful) dump load, it also directly impacts the power management of stand-alone energy systems and affects operational characteristics. However, renewable energy sources are intermittent in nature, thus power generation from renewables may not be adequate to satisfy load demands. Therefore, energy storage and an effective Power Management Strategy (PMS) are vital to ensure system reliability.
This thesis utilises a combination of experiments and modelling to analyse the performance of renewably powered stand-alone energy systems consisting of photovoltaic panels, PEM electrolysers, PEM fuel cells, batteries, metal hydrides and Reverse Osmosis (RO) under various scenarios. Laboratory experiments have been done to resolve time-resolved characteristics for these system components and ascertain their impact on system performance. However, the main objective of the study is to ascertain the differences between applying (simplistic) predictive/optimisation techniques compared to intelligent tools in renewable energy systems. This is achieved through applying intelligent tools such as Neural Networks and Particle Swarm Optimisation for different aspects that govern system design and operation as well as solar irradiance prediction.
Results indicate the importance of device level transients, temporal resolution of available solar irradiance and type of external load profile (static or time-varying) as system performance is affected differently. In this regard, minute resolved simulations are utilised to account for all component transients including predicting the key input to the system, namely available solar resource which can be affected by various climatic conditions such as rainfall. System behaviour is (generally) more accurately predicted utilising Neural Network solar irradiance prediction compared to the ASHRAE clear sky model when benchmarked against measured irradiance data. Allowing Particle Swarm Optimisation (PSO) to further adjust specific control set-points within the systems PMS results in improvements in system operational characteristics compared to using simplistic rule-based design methods. In such systems, increasing energy storage capacities generally allow for more renewable energy penetration yet only affect the operational characteristics up to a threshold capacity. Additionally, simultaneously optimising system size and PMS to satisfy a multi-objective function, consisting of total Net Present Cost and CO2 emissions, yielded lower costs and carbon emissions compared to HOMER, a widely adopted sizing software tool. Further development of this thesis will allow further improvements in the development of renewably powered energy systems providing clean, reliable, cost-effective energy. All simulations are performed on a desktop PC having an Intel i3 processor using either MATLAB/Simulink or HOMER.
11
Knob, Daniel. "Geração de hidrogênio por eletrólise da água utilizando energia solar fotovoltaica." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-11062014-143621/.
Full textAbstract:
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.
12
Ho, Po Yu. "New molecular materials for organic and dye-sensitized solar cells and photocatalytic hydrogen generation." HKBU Institutional Repository, 2016. https://repository.hkbu.edu.hk/etd_oa/280.
Full textAbstract:
Emerging solar energy technology, including photovoltaics, solar fuels generation and solar thermal systems, is considered as one of the most potential renewable energy resources because of the tremendous and free radiant energy supply by our sun. Unlike burning of fossil fuels, carbon dioxide emission-free energy conversion process is definitely another key feature and attracting scientists to explore these research areas. Besides, this implies a giant business market to compete with traditional fossil fuel companies. Nevertheless, it is too early to realize commercial application since the technologies are in the early development stage and there is still much room to explore and improve. Simply speaking, energy conversion efficiency, robustness, environmental impacts and cost are the major factors the community should deeply concentrate on at this moment. This provides many research opportunities on the creation of novel molecular functional materials and investigates the relationship between the molecular design and functional properties, and they obviously take up significant roles in the technology evolution. The basic concepts and conspectuses regarding organic photovoltaics and light-driven hydrogen generation are collected in Chapter 1. In Chapter 2, a series of new thiophene-based small molecules is presented and the discussion is focused on its application in the bulk-heterojunction organic solar cells. Importantly, the structure-property relationship is elucidated by varying the terminal electron withdrawing group and elongating the central electron donating unit. The highest power conversion efficiency (η) of 2.6% is attained by the device with compound M3 as the active material with traditional device configuration (without any annealing process and additives addition) under AM 1.5G irradiation. In Chapter 3, a series of DπA organic dyes is introduced and the discussion concentrates on its application in the dye-sensitized solar cells. Briefly, a case study on alkyl chain effects is investigated while a new starburst triarylamine donor and uncommon selenophene-containing π-linker are studied separately. The highest power conversion efficiency (η) of 6.7% is achieved by D11 under AM 1.5G irradiation with a high open-circuit voltage of 0.825 V. In Chapter 4, three new platinum(II) diimine complexes are synthesized and they are utilized as photosensitizers with platinized titanium dioxide as catalyst site in the context of light-driven hydrogen generation. Comparison between platinum(II) diimine dithiolate complex and platinum(II) diimine bis(acetylide) complex is accomplished, and the importance of photosensitization using an organic chromophore with a desirable energy transfer consideration is accounted. Finally, Chapter 5 puts forward the concluding remarks and possible future works while Chapter 6 includes all the experimental details of the studied compounds presented in Chapter 24.
13
Weaver, Eric P. "Low voltage electrochemical hydrogen production." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001849.
Full text
14
Rodriguez, Ramon, and Pamplona David Sanchéz. "DYNAMIC MODELING OF HYBRID PV/THERMAL SOLAR SYSTEM FOR HYDROGEN PRODUCTION." Thesis, University of Gävle, University of Gävle, Department of Technology and Built Environment, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-3580.
Full text
15
Brown, Stephen Alistair. "Observations and modelling of the hydrogen Lyman lines in solar flares." Thesis, University of Glasgow, 2019. http://theses.gla.ac.uk/40974/.
Full textAbstract:
The extent of dynamical processes in the lower atmosphere of the Sun during solar flares is not fully understood. While it is widely accepted that the majority of the associated flare energy is deposited in the Sun's chromosphere, it is less clear how this energy is transported and how it influences the configuration of material flows. Current models of chromospheric evaporation and condensation assume an upwards expulsion of high-temperature plasma, with an accompanying downwards flow at cooler temperatures. In this thesis, the validity of these assumptions are tested using a combination of observations and modelling, with particular focus given to the Lyman lines of hydrogen.
16
Rey, de Castro Ana. "New ways to take advantage from solar energy and produce hydrogen." Revista de Química, 2013. http://repositorio.pucp.edu.pe/index/handle/123456789/99122.
Full textAbstract:
Un grupo de investigadores del Instituto Tecnológico de Israel ha observado que el uso de foto ánodos de Fe2O3 produce una mejora importante en el rendimiento de las celdas fotoelectroquímicas. Las mejoras están basadas en el uso de láminas muy delgadas de Fe2O3 que mejoran la eficiencia en el transporte de carga. La elección de Fe2O3 está basada en su estabilidad en agua, su alta eficiencia de absorción de luz, su no toxicidad y su bajo coste. Las celdas fotoelectroquímicas son importantes para la electrólisis del agua y la producción de hidrógeno.A research group at the Israel Institute of Technology has outlined the use of Fe2O3 photoanodes to enhance the efficiency of photoelectrochemical cells. The improvement is based on the design of extremely thinsheets of Fe2O3, which allow for a more efficient transport of charge carriers, reducing the amount of them that are lost due to recombination. Fe2O3 was chosen as a photoanode material due to its high stability in water, its high light absorption efficiency, the fact that it is non toxic and its low cost. Photoelectrochemical cells are extremely important in order to electrolyse water, hence producing hydrogen,a green fuel.
17
Katyukha, Igor. "World permanent oil crises: pathways for change to solar-hydrogen economy." Thesis, Видавництво СумДУ, 2007. http://essuir.sumdu.edu.ua/handle/123456789/12828.
Full text
18
Aksakal, Ziya Can Şeker Erol. "Hydrogen production from water using solar cells powerd nafion membrane electrolyzers/." [s.l.]: [s.n.], 2007. http://library.iyte.edu.tr/tezlerengelli/master/enerjimuh/T000633.pdf.
Full text
19
Wimmer-Schweingruber, Robert F. "Oxygen, helium, and hydrogen in the solar wind : SWICS/ULYSSES results /." [S.l.] : [s.n.], 1994. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
Full text
20
Hassan, Ibrahim. "Solar energy conversion by photoelectrochemical processes." Thesis, University of Bath, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.542078.
Full text
21
Jeong, Ji-Weon. "Hydrogen passivation of defects and rapid thermal processing for high-efficiency silicon ribbon solar cells." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/15615.
Full text
22
Meyer, Ryan Thomas. "Integrating Architecture and Infrastructure: The Design of a Solar-Powered Hydrogen Refueling Station." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1242416199.
Full text
23
Brown, Jared R. "Analytical Methods Development for High-Throughput Photochemisty With Led Arrays." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/32709.
Full textAbstract:
This thesis describes the design, construction, and evaluation of a series of LED array photolysis systems for high throughput photochemistry. Three generations of array systems of increasing sophistication are evaluated using calorimetric measurements and potassium tris(oxalato)ferrate(III) chemical actinometry. The results are analyzed using descriptive statistics and analysis of variance (ANOVA). The LEDs in the third generation array were shown to be statistically equivalent, with respect to light output, according to physical and chemical actinometry experiments. The third generation LED array was compared with a traditional 1000 W Xe arc lamp source in terms of cost, light intensity, and light stability. Two constant current drivers were evaluated with respect to LED array performance. The optimized third generation LED array was evaluated as the photolysis source for photochemical hydrogen production experiments using the supramolecular catalyst [{(bpy)2Ru(dpp)}2RhCl2](PF6)5.Master of Science
24
Bruce, David R. "Photocathodic composite conductive polymer-titania films for use in solar hydrogen generation." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/43459.
Full textAbstract:
Green hydrogen generation can serve as a solution to energy storage needs of the 21st century if coupled with a renewable energy source such as solar power. There is an advantage to performing in-situ hydrogen generation at a photocatalytic surface in order to reduce system efficiency losses. Investigation into the limitations and benefits of coupled electrolytic and solar process are investigated in this dissertation.
Of chief examination were polybithiophene-titania composite films used as a photocathode in a Nafion 117 membrane based H₂SO₄ electrolytic system. Titania content inclusion up to 0.35 mg/cm² with a range of film thicknesses between 1-20 μm, were investigated in several architectural configurations. The placement of the composite films was directed either towards or away from the proton conducing membrane in a 2-D or 3-D configuration.
The results indicated that the electrochemical benefits to titania inclusion and film thickness increase were counter to photonic energy collection. With an increase in titania there was an increase in electrochemical performance, but it led to worse photonic efficiency as suspected due to an increase in recombination from defect trap states. With an increase in film thickness there was an increase in photonic efficiency with increased photon absorption, but this was accompanied by an increase in cell resistance leading to worse electrochemical performance. Electrochemical performance was also enhanced by placing the catalytic film directly against the membrane, although photonic stimulation in this configuration was impossible in our current cell configuration. Photonic stimulation was enhanced by the deposition of the composite films onto a distributed 3-D carbon fibre substrate. Doping of the 3-D composite films loaded on carbon fibre substrates with a Nafion ionomer interconnect was tested in an effort to enhance the triple phase connectivity of the cell. It was found that the doping resulted in a deactivation of the substrate (both electrochemical and photonic) due to the deposition method used, but increases in photonic performance at higher current densities showed that with less catalyst encapsulation this strategy may be a viable method to enhance PEM based photoelectrochemical cells.
25
Lakadamyalı, Fezile. "Solar light driven hydrogen evolution with cobaloximes modified on dye-sensitised TiO₂." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708088.
Full text
26
Kalapala, Sreevani. "Removal of Hydrogen Sulfide from Landfill Gas Using a Solar Regenerable Adsorbent." Youngstown State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1403006045.
Full text
27
Schulz, Meghan E. "Nitrogen- and carbon-doped titanium dioxide thin films for solar hydrogen generation." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 95 p, 2009. http://proquest.umi.com/pqdweb?did=1896914051&sid=4&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Full text
28
Ghamgosar, Pedram. "Advanced Metal Oxide Semiconductors for Solar Energy Harvesting and Solar Fuel Production." Licentiate thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-64922.
Full textAbstract:
Increasing energy consumption and its environmental impacts make it necessary to look for alternative energy sources. Solar energy as huge energy source which is able to cover the terms sustainability is considered as a favorable alternative. Solar cells and solar fuels are two kinds of technologies, which make us able to harness solar energy and convert it to electricity and/or store it chemically. Metal oxide semiconductors (MOSs) have a major role in these devices and optimization of their properties (composition, morphology, dimensions, crystal structure) makes it possible to increase the performance of the devices. The light absorption, charge carriers mobility, the time scale between charge injection, regeneration and recombination processes are some of the properties critical to exploitation of MOSs in solar cells and solar fuel technology. In this thesis, we explore two different systems. The first one is a NiO mesoporous semiconductor photocathode sensitized with a biomimetic Fe-Fe catalyst and a coumarin C343 dye, which was tested in a solar fuel device to produce hydrogen. This system is the first solar fuel device based on a biomimetic Fe-Fe catalyst and it shows a Faradic efficiency of 50% in hydrogen production. Cobalt catalysts have higher Faradic efficiency but their performance due to hydrolysis in low pH condition is limited. The second one is a photoanode based on the nanostructured hematite/magnetite film, which was tested in a photoelectrochemical cell. This hybrid electrode improved the photoactivity of the photoelectrochemical cell for water splitting. The main mechanism for the improvement of the functional properties relies with the role of the magnetite phase, which improves the charge carrier mobility of the composite system, compared to pure hematite, which acts as good light absorber semiconductor. By optimizing the charge separation and mobility of charge carriers of MOSs, they can be a promising active material in solar cells and solar fuel devices due to their abundance, stability, non-toxicity, and low-cost. The future work will be focused on the use of nanostructured MOSs in all-oxide solar cell devices. We have already obtained some preliminary results on 1-dimensional heterojunctions, which we report in Chapter 3.3. While they are not conclusive, they give an idea about the future direction of the present research.
29
Basu, Alex. "Relation between hydrogen production and photosynthesis in the green algae Chlamydomonas reinhardtii." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-242624.
Full textAbstract:
The modernized world is over-consuming low-cost energy sources that strongly contributes to pollution and environmental stress. As a consequence, the interest for environmentally friendly alternatives has increased immensely. One such alternative is the use of solar energy and water as a raw material to produce biohydrogen through the process of photosynthetic water splitting. In this work, the relation between H2-production and photosynthesis in the green algae Chlamydomonas reinhardtii was studied with respect to three main aspects: the establishment of prolonged H2-production, the involvement of PSII in H2-production and the electron pathways associated with PSII during H2-production. For the first time, this work reveals that PSII plays a crucial role throughout the H2-producing phase in sulfur deprived C. reinhardtii. It further reveals that a wave-like fluorescence decay kinetic, before only seen in cyanobacteria, is observable during the H2-producing phase in sulfur deprived C. reinhardtii, reflecting the presence of cyclic electron flows also in green algae.
30
KNOB, DANIEL. "Geração de hidrogênio por eletrólise da água utilizando energia solar fotovoltaica." reponame:Repositório Institucional do IPEN, 2014. http://repositorio.ipen.br:8080/xmlui/handle/123456789/23300.
Full textAbstract:
Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-01-21T10:10:35Z
No. of bitstreams: 0Made available in DSpace on 2015-01-21T10:10:35Z (GMT). No. of bitstreams: 0
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
31
Doddathimmaiah, Arun Kumar, and arun doddathimmaiah@rmit edu au. "Unitised Regenerative Fuel Cells in Solar - Hydrogen Systems for Remote Area Power Supply." RMIT University. Aerospace, Mechanical and Manufacturing Engineering, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20081128.140252.
Full textAbstract:
Remote area power supply (RAPS) is a potential early market for renewable energy - hydrogen systems because of the relatively high costs of conventional energy sources in remote regions. Solar-hydrogen RAPS systems commonly employ photovoltaic panels, a Proton Exchange Membrane (PEM) electrolyser, a storage for hydrogen gas, and a PEM fuel cell. Unitised Regenerative Fuel Cells (URFCs) use the same hardware for both electrolyser and fuel cell functions. Since both of these functions are not required simultaneously in a solar hydrogen RAPS system, URFCs based on PEM technology provide a promising opportunity for reducing the cost of the hydrogen subsystem used in renewable-energy hydrogen systems for RAPS. URFCs also have potential applications in the areas of aerospace, submarines, energy storage for central grids, and hydrogen cars. In this thesis, a general theoretical relationship between cell potential and current density of a single-cell PEM URFC operating in both fuel-cell (FC) and electrolyser (E) modes is developed using modified Butler-Volmer equations for both oxygen- and hydrogen-electrodes, and accounting for mass transport losses and saturation behaviour in both modes, membrane resistance to proton current, and membrane and electrode resistances to electron current. This theoretical relationship is used to construct a computer model based on Excel and Visual Basic to generate voltage-current (V-I) polarisation curves in both E and FC modes for URFCs with a range of membrane electrode assembly characteristics. The model is used to investigate the influence on polarisation curves of varying key parameters such charge transfer coefficients, exchange current densities, saturation currents, and membrane conductivity. A method for using the model to obtain best-fit values for electrode characteristics corresponding to an experime ntally-measured polarisation curve of a URFC is presented. The experimental component of the thesis has involved the design and construction of single PEM URFCs with an active area of 5 cm2 with a number of different catalyst types and loadings. V-I curves for all these cells have been measured and the performance of the cells compared. The computer model has then been used to obtain best-fit values for the electrode characteristics for the URFCs with single catalyst materials active in each mode on each electrode for the corresponding experimentally-measured V-I curves. Generally values have been found for exchange current densities, charge transfer coefficients, and saturation current densities that give a close fit between the empirical and theoretically-generated curves. The values found conform well to expectations based on the catalyst loadings, in partial confirmation of the validity of the modelling approach. The model thus promises to be a useful tool in identifying electrodes with materials and structures, together with optimal catalyst types and loadings that will improve URFC performance. Finally the role URFCs can play in developing cost-competitive solar- hydrogen RAPS systems is discussed, and some future directions for future URFC research and development are identified.
32
Perkins, Christopher Michael. "Solar thermal decomposition of zinc oxide in aerosol flow for renewable hydrogen production." Diss., Connect to online resource, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3239400.
Full text
33
Yarahmadi, Sina. "Preparation and performance of nanostructured iron oxide thin films for solar hydrogen generation." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/8131.
Full textAbstract:
Nowadays, energy and its resources are of prime importance at the global level. During the last few decades there have been several driving forces for the investigation of new sources of energy. Hydrogen has long been identified as one of the most promising carriers of energy. Photoelectrochemical (PEC) water splitting is one of the most promising means of producing hydrogen through a renewable source. Hematite (α-Fe2O3) is a strong candidate material as photoelectrode for PEC water splitting as it fulfils most of the selection criteria of a suitable photocatalyst material for hydrogen generation such as bandgap, chemical and photelectrochemical stability, and importantly ease of fabrication. This work has explored different preparation techniques for undoped and Si-doped iron oxide thin films using microwave-assisted and conventional preparation methods. Two distinct strategies towards improving PEC performance of hematite photoelectrodes were examined: retaining a finer nanostructure and enhancing the photocatalytic behaviour through doping. By depositing thin films using atmospheric pressure chemical vapour deposition (APCVD) and aerosol-assisted CVD (AACVD) at high temperature, it was shown that a combination of different factors (such as silicon incorporation into the hematite structure and formation of lattice defects, along with a nanostructure of small agglomerate/cluster enhancing hole transportation to the surface) were the contributing factors in improving the PEC performance in hematite films. The role of the Si-containing precursors and their consecutive effect on nanostructure of the hematite films were investigated. Further work is needed to study the decomposition pattern of precursors and consequent effects of Si additives as well as co-dopants on fundamental physical and electrical properties of hematite electrodes. In addition, the feasibility of using microwave annealing for the fabrication of iron oxide thin films prepared by electrodeposition at low temperature was also investigated. Hematite films showed improved PEC performance when microwave assisted annealing was used. Microwave heating decreased the annealing temperature by ~40% while the PEC performance was increased by two-fold. The improved performance is attributed to the lower processing temperatures and rapidity of the microwave method that help to retain the nanostructure of the thin films whilst restricting the grain coalescence to a minimum. Around 60% of the energy can be saved using this low carbon foot-print approach compared to conventional annealing procedures for the lab-scale preparation of hematite films – a trait that will have significant implications for scale-up production. The lower processing temperature requirements of the microwave process can also open up the possibility of fabricating hematite thin films on conducting, flexible, plastic electronic substrates.
34
Styrov, V. V., S. V. Simchenko, and V. N. Golotyuk. "Chemo-emf in the silicon solar cell exposed to low-energy hydrogen atoms." Thesis, Sumy State University, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20602.
Full textAbstract:
A new reactive gas-semiconductor system is experimentally found and examined
for the electron-hole pairs (e-h pairs) generation in the semiconductor due to exoergicty
of a surface chemical reaction. This system is “atomic hydrogen-crystalline silicon”. The
p-n silicon homojunction was used to produce chemo-emf and chemicurrent in the semi-
conductor system due to e-h pairs creation. The ideal geometry of the semiconductor
system would require the top semiconductor layer be of a nanosized thickness since only
the upper layer of the semiconductor is involved in chemical excitation. To make the
beginning of a research we howere harnessed the commercial silicon solar cell fabricat-
ed with the certain technological changes to have a bare semiconductor surface. A spe-
cial procedure was worked out to prepare the silicon surface free of the blocking layer of
silicon oxide.
The chemo-emf in the open circuit up to a few mV and the short circuit chemicur-
rent up to the record 700 nA were achieved that are the promising magnitudes to pave a
way for direct chemical energy to electrical energy conversion by semiconductor sys-
tems.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/20602
35
Meyer, Ryan. "Integrating architecture and infrastructure the design of a solar-powered hydrogen refueling station /." Cincinnati, Ohio : University of Cincinnati, 2009. http://rave.ohiolink.edu/etdc/view.cgi?acc_num=ucin1242416199.
Full textAbstract:
Thesis (Master of Architecture)--University of Cincinnati, 2009.Advisor: Jerry Larson. Title from electronic thesis title page (viewed July 27, 2009). Includes abstract. Keywords: architecture; infrastructure; solar energy; concentrating solar power; hydrogen economy. Includes bibliographical references.
36
Rossi, Gianmarco. "modeling of proton exchange membrane water electrolyzer for green hydrogen production from solar energy." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Find full textAbstract:
Hydrogen is considered one of the means by which to store energy coming from renewable and intermittent power sources. With the growing capacity of renewable energy sources, a storage system is required to not waste energy. PEM electrolysis provides a sustainable solution for the production of hydrogen and is well suited to couple with energy sources such as solar and wind.
This work reports the development of simulation software to estimate the performance of a proton exchange membrane electrolyzer working at atmospheric or low pressure conditions connected to a solar energy source. The electrolyzer is defined from a validated reference semi-empirical model, which allows for simulating the electrochemical, thermal and H2 output flow behaviours with enough precision for engineering applications. An algorithm for a fitting procedure to characterize commercial products, and functions for power modulation have been implemented. A series of simulations have been carried on, starting from real photovoltaic data of input power, and the output values have been discussed, with particular attention to output flow rate, thermal behaviour and the cooling demand in order to preserve the operation of the electrolyzer.
37
Zhang, Jinqiang. "Development of nanostructured photocatalysts for solar fuels production." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2021. https://ro.ecu.edu.au/theses/2403.
Full textAbstract:
Hydrogen energy is an ideal energy resource owing to its clean and efficient utilization. As an energy carrier without natural abundance, the limited reserve makes the high consumption a big challenge. In the meantime, fossil fuels, e.g., coal, oil and gas, have been important carbon carriers in the long-term carbon cycle, but their upgrading is restricted to conventional thermocatalysis. Solar energy with the advantages of large abundance, widespread distribution, and high flux appeals extensive attention, but unfortunately is underutilized at the moment. Photocatalysis initiated with semiconductors is a promising pathway towards the conversion and storage of solar energy into chemical stocks, and has been studied for several decades. However, due to the low photoresponse capacity and solar energy conversion efficiency of the existing photocatalysts, the prospect of their industrialization is still unclear. Photothermal catalysis integrating photocatalysis and thermocatalysis into one unit has been proposed in the past several years. Although its quantum efficiency and reaction turnover frequency were significantly improved, the reaction mechanisms have not yet been well illustrated. This PhD study is to develop photo assisted catalysis to obtain high performances for energy preparation and fossil fuels upgrading, and to have a deep insight into their reaction mechanisms. First, in-plane heterostructured graphene/carbon nitride photocatalyst was prepared via a hydrogeninitiated chemical epitaxial growth strategy. With the insert of nano-graphene into the porous carbon nitride, the quantum efficiency of the water splitting reaction for hydrogen generation was significantly enhanced (Chapter 3). Considering the unsatisfied incident light to electron efficiency, the study unveiled the potential difference as the internal electrical field affecting the separation, transfer and output of photoinduced charge carriers. Meanwhile, the quantum efficiency and utilization of solar light were both improved via the optimization of potential differences in photocatalytic systems (Chapter 4). In addition, the active sites (Chapter 5) and relationships between photocatalysis and thermocatalysis (Chapter 6) in photothermal catalytic systems were both in-depth studied. With the available reaction mechanism and optimization of reaction conditions, the photothermal catalytic performances in the upgrading of fossil fuels are increased to a industrialization level. This PhD project contributes to the improvements of quantum efficiency via catalyst modification, reaction optimization and mechanism investigation and then expects to provide both technological and scientific knowledge for the full storage and conversion of solar energy into fuels.
38
Eskandari, Azin. "A preliminary theoretical and experimental study of a photo-electrochemical cell for solar hydrogen production." Thesis, Université Clermont Auvergne (2017-2020), 2019. http://www.theses.fr/2019CLFAC104.
Full textAbstract:
Afin de relever le défi énergétique et climatique du 21ième siècle qui s’annonce, une solution consiste, pour valoriser la ressource solaire, à mettre au point des procédés de production de vecteurs énergétiques stockables par photosynthèse artificielle permettant la synthèse de carburants solaires, en particulier l’hydrogène. La compréhension de ses procédés et l’obtention de performances cinétiques et énergétiques élevées nécessitent le développement de modèles de connaissance génériques, robustes et prédictifs considérant le transfert de rayonnement comme processus physique contrôlant le procédé à plusieurs échelles mais aussi les différents autres phénomènes intervenant dans la structure ou la réification du modèle.Dans le cadre de ce travail de doctorat, le procédé photo-réactif au cœur de l’étude était la cellule photo-électrochimique. D’un fonctionnement plus complexe que le simple photoréacteur, avec une photo-anode et une (photo)cathode, la cellule photo-électrochimique dissocie spatialement les étapes d’oxydation et de réduction. En se basant à la fois sur la littérature existante (essentiellement dans le domaine de l’électrochimie) et en déployant les outils développés par l’équipe de recherche sur le transfert de rayonnement et la formulation du couplage thermocinétique, il a été possible d’établir des indicateurs de performance des cellules photo-électrochimiques.En parallèle de l’établissement de ce modèle, une démarche expérimentale a été entreprise en se basant tout d’abord sur une cellule commerciale de type Grätzel (DS-PEC) indiquant les tendances générales de tels convertisseurs de l’énergie des photons avec en particulier une chute de l’efficacité énergétique en fonction de la densité incidente de flux de photons. Un dispositif expérimental modulable (Minucell) a aussi été développé et validé afin de caractériser des photo-anodes de différentes compositions comme des électrodes de TiO2 imprégnées de chromophore pour un fonctionnement en cellule de Grätzel ou bien des électrodes d’hématite Fe2O3 (SC-PEC) où le semiconducteur joue à la fois les fonctions d’absorption des photons et de conduction des porteurs de charges. Surtout, le dispositif Minucell a permis de tester, caractériser et modéliser le comportement d’une cellule photo-électrochimique de type bio-inspiré pour la production d’H2 utilisant à la photo-anode un catalyseur moléculaire Ru-RuCat (développé par ICMMO Orsay/CEA Saclay) et à la cathode un catalyseur CoTAA (développé par LCEMCA Brest). Minucell a été utilisé pour caractériser chaque élément constitutif d’une cellule photo-électrochimique puis la cellule dans son ensemble, confirmant les tendances et observations obtenues sur les efficacités énergétiques.Ce travail préliminaire ouvre de très nombreuses perspectives de recherche, il pose des bases communes entre électrochimie et génie des systèmes photo-réactifs et donne des pistes quant à la conception et l’optimisation cinétique et énergétique des cellules photo-électrochimiques pour la production d’hydrogène et de carburants solairesIn order to meet the energy and climate challenge of the coming 21st century, one solution consists of developing processes for producing storable energy carriers by artificial photosynthesis to synthesize solar fuels, in particular hydrogen, in order to valorize the solar resource. The understanding of these processes and the achievement of high kinetic and energetic performances require the development of generic, robust and predictive knowledge models considering radiative transfer as a physical process controlling the process at several scales but also including the various other phenomena involved in the structure or reification of the model.In this PhD work, the photo-reactive process at the heart of the study was the photo-electrochemical cell. More complex than the simple photoreactor, with a photo-anode and a (photo)cathode, the photo-electrochemical cell spatially dissociates the oxidation and reduction steps. Based both on the existing literature (mainly in the field of electrochemistry) and by deploying the tools developed by the research team on radiative transfer and thermokinetic coupling formulation, it was possible to establish performance indicators of photo-electrochemical cells.In parallel to the establishment of this model, an experimental approach was undertaken based first on a commercial Grätzel-type cell (DS-PEC) indicating the general trends of such photon energy converters with in particular a drop in energy efficiency as a function of the incident photon flux density. A modular experimental device (Minucell) has also been developed and validated in order to characterize photo-anodes of different compositions such as chromophore impregnated TiO2 electrodes for operation in Grätzel cells or Fe2O3 hematite electrodes (SC-PEC) where the semiconductor plays both the functions of photon absorption and charge carrier conduction. Above all, the Minucell device allowed to test, characterize and model the behavior of a bio-inspired photo-electrochemical cell for H2 production using at the photo-anode a Ru-RuCat molecular catalyst (developed by ICMMO Orsay/CEA Saclay) and at the cathode a CoTAA catalyst (developed by LCEMCA Brest). Minucell was used to characterize each constituent element of a photo-electrochemical cell and then the cell as a whole confirming the trends and observations obtained on energy efficiencies.This preliminary work opens up a wide range of research prospects, lays common ground between electrochemistry and photo-reactive systems engineering, and provides insights into the design and kinetic and energy optimization of photo-electrochemical cells for the production of hydrogen and solar fuels
39
Nilsson, Mattias. "Solar-driven Hydrogen Production by the use of MIEC Membranes : A Techno-Economic Assessment." Thesis, KTH, Energiteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-104735.
Full textAbstract:
This thesis comprises an assessment of a novel concept to produce high purity hydrogen using mixed oxide ion/electronic conductor (MIEC) membranes and energy provided by solar concentrators (i.e. parabolic troughs or parabolic dishes). The vision of this concept is that it will be used to produce tons of high purity hydrogen for fuel cells, which is a scarce commodity with an increasing demand from residential and transportation power generation applications. The MIEC membrane activates a steam reforming reaction between water and methane to produce hydrogen of high purity on the water side and syngas on the fuel side. Expectations are that this concept has cost advantages over other thermo-chemical water-dissociation methods, using a lower temperature and no electricity for the reaction process. The thesis’ focus is on techno-economic aspects of the concept, as part of an application process for project financing by the European Commission of Research and Innovation. The assessment in the thesis shows that the overall efficiency of the concept is expected to be very low. It also identifies the difficulties of providing stable working conditions for the concept. Suggestions to improve the concept are proposed to address the most urgent problems of the concept. These suggestions illuminate the opportunities that actually do exist to combine MIEC membranes, solar energy and thermo-chemical water splitting into a working concept. These improvements include using parabolic dishes instead of parabolic troughs, using furnaces with control systems and using a viable flow rate. The production capacity of high purity hydrogen is expected to be approximately 89 mg per minute in a membrane bundle (i.e. 150 thin membrane fibers with an oxygen permeation flux of 1 ml cm-2 min-1) if these improvements were implemented. This would imply that the studied concept needs further development to produce high purity hydrogen in quantities that could meet the shortage on the commercial fuel cell markets.
40
Marques, Alessandra Abe Pacini Schmidt. "The role of hydrogen and beryllium isotopes as tracers of solar and climate variability." Instituto Nacional de Pesquisas Espaciais, 2010. http://urlib.net/sid.inpe.br/mtc-m19/2010/09.10.18.49.
Full textAbstract:
A história do clima terrestre e sua relação com a atividade solar podem ser reconstruídas a partir de informações encontradas em registros naturais. Dentre esses registros, os isótopos estáveis do hidrogênio e os radioisótopos cosmogênicos do berílio são usualmente analisados, retirados de diferentes matrizes naturais, especialmente de testemunhos de gelo e amostras de ar. Nesta tese, a razão deutério/hidrogênio, extraída de testemunhos de gelo, e a atividade do $^7$Be, medida em amostras de ar, foram utilizadas para o estudo do papel de diferentes fenômenos climáticos e solares em suas variações. Os dados de deutério foram obtidos a partir de testemunhos de gelos das regiões polares (Groenlândia e Antártica) e equatoriais (Andes) para as últimas quatro décadas (1951 1994). Foi encontrada uma periodicidade decadal nessas séries isotópicas, que parece ser o resultado de uma influência direta da modulação da irradiância solar no ciclo hidrológico global. Além disso, os resultados encontrados enfatizaram a importância dos regimes climáticos locais na variabilidade do deutério medido. Os dados de berílio-7 foram extraídos de amostras de ar coletadas próximas ao solo desde 1987 (com resolução temporal trimestral) nas cercanias da Usina Nuclear de Angra, no Rio de Janeiro, Brasil, e também de amostras de ar coletadas e medidas (semanalmente) pela nossa própria instrumentação instalada desde o final de 2008 no campus da Universidade Estadual do Rio de Janeiro. Dados e modelos numéricos da Universidade de Oulu, Finlândia, foram também utilizados na análise das origens da variabilidade do $^7$Be. Os resultados indicam que o forçante dominante da modulação dos dados de 7Be do Rio de Janeiro é o padrão regional de chuvas, tornando as variações locais da produção cosmogênica (causada por raios-cósmicos) não evidentes nos dados. Além disso, nossos resultados indicaram que eventos anômalos da dinâmica troposférica podem imprimir nos dados de $^7$Be as informações dos movimentos 3-D das massas de ar. Assim, essa tese explora as informações contidas nas séries temporais dos isótopos estudados, mostrando os potenciais usos científicos de cada um deles e destacando a necessidade de interpretações mais cuidadosas das modulações isotópicas utilizadas como traçadores de variações climáticas e solares.The history of Earth's climate and the role of solar activity as a driver of the observed changes can be recovered through the study of natural records. Among them, stable isotopes of hydrogen and cosmogenic radioisotopes of beryllium are usually analyzed, especially from ice cores and air samples. In this thesis, deuterium/hydrogen ratio from ice cores and $^7$Be activity from air samples are analyzed to study the role of different climatic and solar phenomena in their variation. Deuterium isotope data were obtained from polar (Greenland, Antarctic) and equatorial (Andes) regions for the last four decades (1951-1994). It has been found that deuterium series present a decadal cycle, which might be a direct influence of solar irradiance modulation on the hydrological cycle. Furthermore, the results emphasize the importance of the local climatic system on the deuterium isotopic temporal variability. Berylium-7 data were obtained from near-ground air samples measured since 1987 around the Angras Nuclear Power Station (with 3-month time resolution) , in Rio de Janeiro, Brazil, and also from air-samples acquired by our own instrumentation installed in the campus of University of Rio de Janeiro State since late 2008 (with weekly time resolution). Data and model results from Oulu University, Finland, were also used in the $^7$Be variability study. For the Brazilian isotopic data, the dominant driver of its modulation was found to be the regional precipitation pattern, with the local production by cosmic-rays having a minor effect on its variability. Moreover, our results indicate that anomalous events of tropospheric dynamics may also imprint information about air masses 3-D movement in the near-ground air $^7$Be data. Thus, this thesis explores the information contained in the studied isotopic time series, showing the potential scientific uses of them and highlighting the necessity of more careful interpretations of the isotopic modulation as proxies of climatic and solar variations.
41
Stone, Howard Brian James. "Thermochemical hydrogen production from the sulphur-iodine cycle powered by solar or nuclear sources." Thesis, University of Southampton, 2007. https://eprints.soton.ac.uk/65716/.
Full textAbstract:
Since mankind's adoption of fossil fuels as its primary energy carrier for heating, elec- tricity and transportation, the release of greenhouse gases into the atmosphere has increased constantly . A potential replacement energy carrier is hydrogen. Current industrial techniques for dissociating hydrogen from its common substances are con- ventionally reliant on fossil fuels and thus greenhouse gases are still released. As a mechanism to develop a hydrogen economy current industrial techniques will suffice; however, a long-term sustainable solution to hydrogen mass production that does not release greenhouses gases is desired. The United States of America Government be- lieves that the Sulphur-Iodine thermochemical hydrogen production cycle, thermally powered by a nuclear source, is the most likely long-term solution. A critical part of the Sulphur-Iodine cycle is the point of interaction between the thermal source and sulphuric acid used within the cycle. A novel bayonet heat exchanger made from silicon carbide is theoretically applied to the point of interaction. Through a combination of experiments and theoretical modelling, the bayonet heat exchanger is characterised. The bayonet model is then modified to simulate the intended nuclear reactor favoured by the United States Department of Energy. In addition, the bayo- net heat exchanger is analysed for a solar thermal application. An advanced design of the bayonet is also presented and theoretically analysed for its increased thermal efficiency.
42
Friman, Max. "Techno-economic analysis of solar powered hydrogen production in vicinity of Swedish steel industries." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-281961.
Full textAbstract:
The world’s steel industries account for 7% of the global CO2 emissions and the demand for steel is estimated to increase in the near future. Swedish steel manufactures are investigating processes to produce steel in an environmental friendly way. One attractive option is to include hydrogen gas as much as possible in the processes. This thesis investigates hydrogen production from solar power in vicinity of 7 different steel producing facilities in Sweden. The objective is to construct systems with electrolyzers, PV and storage to possibly lower the cost of operation as well as lowering the CO2 emissions. The types of industries investigated are divided into two groups. The first group consists of industries with no current hydrogen demand. These industries are evaluated with a system which produces hydrogen from PV during the summer and storing it until winter when electricity prices increase. Then the hydrogen is converted back to electricity with a fuel cell. The second group consists of industries with a existing demand of hydrogen. These industries are evaluated with a system similar to the first, but the hydrogen is used in gasous form in melt-shops and furnaces, not as a source for electricity. The systems are evaluated on two parameters; the change in CO2 emissions and NPV. The system for group one showed a negative NPV for all industries, as well as an increase of CO2 emissions. The system for group two showed both positive NPV and a decrease in CO2 emissions compared to operations as it is done today. As a conclusion of this thesis, industries would benefit from producing their own hydrogen gas at the facilities if they use it as a raw product. If it shall be used as storage for electricity usage, the storage cost today are too high.Världens stålindustrier bidrar till 7% av de totala CO2 utsläppen, och efterfrågan av stål i världen antas öka. I Sverige undersöker ståltillverkare nya mer miljövänliga alternativ för att producera stål. Ett av dessa alternativ är att i större utsträckning använda använda vätgas i stålproduktione. Syftet för denna uppsats var att undersöka hur vätgasproduktion från solkraft i närhet av 7 svenska stålindustrier påverkar CO2 utsläpp samt driftkostnader. Detta gjordes genom att bygga system bestående av elektrolysörer, PV samt förvaring. Det 7 industrierna blev uppdelade i två grupper. Den första gruppen består av industrier som inte använder sig utav vätgas idag. Dessa industrier undersöktes med ett system där vätgas produceras från solkraft under sommarhalvåret för att lagras till vintern, då priset på elektricitet ökar. Vätgasen blir då omväxlad till elektricitet via en bränslecell. Den andra gruppen består av industrier som redan använder sig utav vätgas. Dessa industrier undersöktes med ett system som liknar det första, men här används vätgasen som råprodukt i ugnar, och omvandlas därav inte till elektricitet. Båda systemen mättes på två parametrar, skillnad i CO2 utsläpp och NPV. Alla industrier som utvärderades med första systemet visade en ökning i CO2 utsläpp och negativa NPV. Industrierna i grupp två som utvärderades med det andra systemet visade båden en förminskning i CO2 utsläpp samt possitiva NPV. Slutsatsen av denna uppsats är att industrier som använder sig utav vätgas som råvara skulle gynnas av att producera vätgasen själva. Om vätgasen ska användas till elektricitet vid ett senare tillfälle är kostnaden för förvaring idag alldeles för hög.
43
Abdin, Zainul. "Components models for solar hydrogen hybrid energy systems based on metal hydride energy storage." Thesis, Griffith University, 2017. http://hdl.handle.net/10072/370890.
Full textAbstract:
Modelling and simulation are essential tools for concept evaluation and for predicting
the performance of a hybrid energy system, since prototyping and testing each candidate
design for such a complex system would almost always be prohibitively cumbersome,
expensive and time consuming. To meet the modelling and simulation objectives, the various
components of the system (sources, storage, loads, and converters) need to be characterised
and modelled in a tractable way. The tuning of the models to reflect the actual system
components is a key milestone in this process and requires reliable and comprehensive
experimental data. Furthermore, environmental conditions such as ambient temperature may
have a significant impact on the performance, which has to be taken into account.
The complexity of hybrid energy systems and their dependence on embedded control
software increases the difficulty in predicting interactions among the various components and
subsystems. A modelling environment that can model not only the components but also
control algorithms (such as Matlab/Simulink, Homer etc.) is therefore advantageous.
Effective diagnosis of faults in an installed system also presents a challenge, because of the
interactions between the components and the control system. Modelling may play an
important role in diagnosis of the operating components. For example, running an electrolyser
model and comparing actual electrolyser operating variables with those obtained from the
model may help to diagnose a fault in the real electrolyser.
This thesis focuses on modelling the principal components of hybrid solar energy
systems that include energy storage in the form of hydrogen: a large photovoltaic array
subject to manufacturer’s variability and temperature inhomogeneity; two types of
electrolyser as commonly found in hydrogen energy systems; a metal-hydride hydrogen
storage tank; a fuel cell. Attention is given here to building physics-based component models with minimum empiricism and to critically analysing the state of the art in modelling such
components. The models have been realised in Simulink, so that they are mutually compatible
and can be linked into a whole of system model. All the models were validated against
experimental data and performed at least as well as models found in the literature. The thesis
is based on six papers, four already published and two submitted.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Natural Sciences
Science, Environment, Engineering and Technology
Full Text
44
Nigro, Luciano Giannecchini. "Concepção de um receptor de cavidade para concentração de energia solar para aplicação em reatores químicos." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/3/3150/tde-14072016-104455/.
Full textAbstract:
Este trabalho dimensionou um receptor de cavidade para uso como reator químico de um ciclo de conversão de energia solar para energia química. O vetor energético proposto é o hidrogênio. Isso implica que a energia solar é concentrada em um dispositivo que absorve a radiação térmica e a transforma em energia térmica para ativar uma reação química endotérmica. Essa reação transforma o calor útil em gás hidrogênio, que por sua vez pode ser utilizado posteriormente para geração de outras formas de energia. O primeiro passo foi levantar os pares metal/óxido estudados na literatura, cuja finalidade é ativar um ciclo termoquímico que possibilite produção de hidrogênio. Esses pares foram comparados com base em quatro parâmetros, cuja importância determina o dimensionamento de um receptor de cavidade. São eles: temperatura da reação; estado físico de reagentes e produtos; desgaste do material em ciclos; taxa de reação de hidrólise e outros aspectos. O par escolhido com a melhor avaliação no conjunto dos parâmetros foi o tungstênio e o trióxido de tungstênio (W/WO3). Com base na literatura, foi determinado um reator padrão, cujas características foram analisadas e suas consequências no funcionamento do receptor de cavidade. Com essa análise, determinaram-se os principais parâmetros de projeto, ou seja, a abertura da cavidade, a transmissividade da janela, e as dimensões da cavidade. Com base nos resultados anteriores, estabeleceu-se um modelo de dimensionamento do sistema de conversão de energia solar em energia útil para um processo químico. Ao se analisar um perfil de concentração de energia solar, calculou-se as eficiências de absorção e de perdas do receptor, em função da área de abertura de um campo de coleta de energia solar e da radiação solar disponível. Esse método pode ser empregado em conjunto com metodologias consagradas e dados de previsão de disponibilidade solar para estudos de concentradores de sistemas de produção de hidrogênio a partir de ciclos termoquímicos.This work aimed to design a cavity receptor for purpose of chemical reactor for cycles of energy conversion of solar energy to chemical energy. The proposed chemical agent is hydrogen gas. Solar energy is concentrated in a device that absorbs thermal radiation, transforming it in thermal energy, used to activate chemical reactions. This reaction transforms the heat in hydrogen gas and the last, in its turn, can be used to generate other forms of energy. The first step oh this work was an assessment of metal/oxides pairs studied in literature, which can be used to activate thermochemical cycles for hydrogen production. These pairs were compared based in four parameters, important to cavity receptor design: reaction temperature, physical state of the reactants and products, material resistance to several cycles; hydrolysis reaction rate and other aspects. The chosen pair, rated as the higher average in all parameters, was the pair tungsten and tungsten trioxide. (W/WO3). Based in the literature, it was determined a standard reactor, which was studied regarding cavity reactor performance. By such analysis, it was possible to determine the main design parameters, therefore, cavity aperture, window transmissivity, and the cavity geometric dimensions. The results allowed to establish a mathematical model in which solar energy can be converted in useful energy for chemical processes, inside a cavity receptor. Given a profile of solar energy concentration, it was calculated absorption and energy lost efficiencies, related to a solar concentration field and radiation available. This method can be used in tandem with available methodologies and data of solar predictions for hydrogen production by concentration systems via thermochemical cycles.
45
Pinto, Carolina Ferreira. "Estudo sobre o uso de células a combustível movida a hidrogênio solar em residências." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/102/102131/tde-18122014-161350/.
Full textAbstract:
Devido a crescente demanda de energia elétrica este trabalho tem como objetivo a elaboração de um projeto bioclimático de uma edificação para o estudo sobre o uso de célula a combustível movida a hidrogênio solar, como forma de energia alternativa. O fornecimento de energia elétrica é feito apor meio de um sistema proveniente de painéis fotovoltaicos fornecendo energia para a produção de hidrogênio através da eletrólise da água para gerar energia elétrica com uma célula a combustível. A metodologia utilizada foi projetar uma casa típica da região do interior de São Paulo, para posteriormente dimensionar um sistema hidrogênio solar adequado para essa casa modelo. Foi feita a análise do clima local para posteriormente aplicar estratégias da arquitetura bioclimática. Os dados sobre o dimensionamento do sistema tais quais, número de painéis solares, número e volume dos tanques de hidrogênio necessários, potência e tamanho físico da célula a combustível foram fornecidos pela empresa UNITECH de fabricação de célula a combustível. Um modelo foi simulado utilizando uma planilha eletrônica; nele foram introduzidas as principais características e eficiências dos equipamentos que compõem o sistema, bem como o perfil de carga elétrica característico do local e seus custos. Como resultado foram analisadas as formas de dimensionar o sistema hidrogênio solar para uma residência típica, onde foi constatado que há duas formas de dimensionamento: uma através da demanda energética da casa (kWh) e outra através da potência requerida pelos equipamentos da casa (Watts). O modelo escolhido a ser estudado e representado com o projeto arquitetônico foi pela curva da demanda energética diária resultando em 450 kWh/mês, havendo assim a diminuição da área de painéis solares e viabilizando a introdução da nova tecnologia. Outro cenário foi analisado pelo cálculo da potência, resultando em um total de 5 kW e obtendo uma extensa área de painéis solares, no entanto essa energia que sobra poderia ser fornecida para as concessionárias auxiliando nos horários de pico a energia consumida, ou ainda formando uma mini usina para comunidades isoladas. No projeto arquitetônico da edificação foram analisadas as mudanças e dificuldades quanto ao design, local e instalação dos componentes para implantação do sistema. Os dados de energia gerada e consumida são analisados servindo também como base para diversas pesquisas. Conclui-se que o sistema ainda não consegue ser competitivo economicamente com o sistema tradicional de energia elétrica, se não levado em conta aspectos ambientais, e sem o apoio de uma forte política governamental; porém aspectos do processo projetual arquitetônico se mantêm praticamente os mesmos. E ainda destaca-se a mudança de paradigma da energia elétrica, pois o consumidor passa a ser produtor.Due to increasing demand for electricity this paper aims to draw up a bioclimatic design a building for studies on the use of fuel cells powered solar hydrogen as an alternative energy. The electricity supply is done through a system from photovoltaic panels supplying power to produce hydrogen through electrolysis of water to generate electricity with a fuel cell. The methodology used was to design a typical home of the São Paulo region, using data from IBGE and SINFHA for later sizing a solar hydrogen system to the house style. Analysis of the local climate was taken by INMET, CPTEC and CIIAGRO. Subsequently the bioclimatic chart (NBR 15220) and the solar chart for use of bioclimatic architecture strategies are applied. The data on the system design as such, the number of solar panels, number and volume of hydrogen required, power and physical size of the fuel cell tanks were provided by the company UNITECH manufacturing fuel cell. A model was simulated using a spreadsheet; it was introduced the main characteristics and efficiencies of equipment that make up the system, as well as the listing of the characteristic electrical charge of the place and its costs. As a result ways to scale the solar hydrogen system for a typical residence, where it was found that there are two ways of scaling were analyzed: one through the house energy demand (kWh) and the other through the power required by the equipment of the house (Watts) . The model chosen to be studied and represented with the architectural design was by the curve of daily energy demand resulting in 450 kWh / month, so there is a decrease in the area of solar panels and enabling the introduction of new technology. Another scenario was analyzed by calculating the power, resulting in a total of 5 kW and getting a large area of solar panels, however this left over energy could be provided for utilities assisting at peak energy consumed, or forming a mini plant for isolated communities. In the architectural design of the building, we analyzed the changes and difficulties regarding the design, location and installation of components for deployment. The data generated and consumed energy are analyzed also serving as base for numerous research. We conclude that the system still can not be economically competitive with traditional power system, if not taken into account environmental aspects, and without the support of a strong government policy; But aspects of the architectural design process remain largely the same.
46
Bell, Stuart James. "The effect of light intensity and temperature on photocatalytic water splitting." Thesis, Queensland University of Technology, 2011. https://eprints.qut.edu.au/50960/1/Stuart_Bell_Thesis.pdf.
Full textAbstract:
Photocatalytic water splitting is a process which could potentially lead to commercially viable solar hydrogen production. This thesis uses an engineering perspective to investigate the technology. The effect of light intensity and temperature on photocatalytic water splitting was examined to evaluate the prospect of using solar concentration to increase the feasibility of the process.
P25 TiO2 films deposited on conducting glass were used as photocatalyst electrodes and coupled with platinum electrodes which were also deposited on conducting glass. These films were used to form a photocatalysis cell and illuminated with a Xenon arc lamp to simulate solar light at intensities up to 50 suns. They were also tested at temperatures between 20°C and 100°C.
The reaction demonstrated a sub-linear relationship with intensity. Photocurrent was proportional to intensity with an exponential value of 0.627. Increasing temperature resulted in an exponential relationship. This proved to follow an Arrhenius relationship with an activation energy of 10.3 kJ mol-1 and a pre-exponential factor of approximately 8.7×103.
These results then formed the basis of a mathematical model which extrapolated beyond the range of the experimental tests. This model shows that the loss of efficiency from performing the reaction under high light intensity is offset by the increased reaction rate and efficiency from the associated temperature increase. This is an important finding for photocatalytic water splitting. It will direct future research in system design and materials research and may provide an avenue for the commercialisation of this technology.
47
Gies, Warren. "Conditions for Maximum Operating Efficiency of a Multi-Junction Solar Cell and a Proton Exchange Membrane Electrolyser System for Hydrogen Production." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/40985.
Full textAbstract:
Hydrogen is a valuable and versatile energy currency; it may be produced by harvesting solar energy and later used as a fuel to generate electricity any time of the day. This energy transaction of solar energy to hydrogen is evaluated in this work by employing a one-to-one multi-junction solar cell to proton exchange membrane combined system in a laboratory setting. Both components of the system were commercially available. The energy conversion efficiency of each isolated system was first evaluated to determine the ideal operation conditions of each respective system. For input currents in the range of 60 mA to 440 mA, the proton exchange membrane converted electrical energy to chemical potential energy with an efficiency greater than 90%. The multi-junction solar cell reached efficiencies of up to 33% while under a solar concentration of 30 Suns. The current and voltage characteristics, which resulted in the optimal operation of the isolated systems did not align and therefore, both systems were not operating at
their ideal operation conditions when in the combined system. The overall energy conversion efficiency of the system was measured to be at most 19.1% under 25 Suns, an efficiency higher than systems employing traditional silicon solar cells. It was theorized that if the two system were operating under ideal conditions, the overall energy conversion efficiency would be 30.3% between 10 and 15 Suns. Methods to align the ideal operation conditions of the two systems are presented.
48
Adeli, Koudehi Babak. "Solar hydrogen generation through overall water splitting on gallium-zinc oxynitride visible-light activated photocatalyst." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/60303.
Full textAbstract:
In this study, novel approaches for the development of solar-responsive photocatalysts for water splitting are investigated, with a focus on the gallium-zinc oxynitride solid solution (GaN:ZnO).
A facile synthesis technique was developed for the fabrication of nanoporous GaN:ZnO photocatalyst. The synthesis time was reduced substantially to 12 min (from original 10+ h) as the result of effective solid–solid and gas–solid reactant interactions at the nanoscale. The synthesized photocatalyst samples were characterized for their optical, structural, and photochemical properties. Despite the short synthesis time, the prepared nanoporous GaN:ZnO photocatalyst maintained the overall visible-light water splitting activities at reasonable rates, reaching to the maximum apparent quantum efficiency of 2.71% at 420–440 nm.
Decoration of the photocatalyst surface with the optimal amount of various hydrogen and oxygen evolution co-catalyst materials through photo-deposition and impregnation was investigated. Our experimental and characterization data suggest a mechanism for minimizing the effect of the undesired charge recombination and reverse reaction through the utilization of structural nanopores as the active water splitting regions.
To reduce the recombination of photo-excited charges, the hybridization of GaN:ZnO photocatalyst on highly conductive graphene support was studied. Effective electrochemical interaction between composite components was confirmed through material characterization, photo-induced conversion of graphene oxide to reduced graphene oxide (rGO), and visual observation of co-catalyst nanoparticles on the surface of the conductive nanosheets. The GaN:ZnO-rGO composite photocatalyst exhibited ~70% improvement in photocatalytic hydrogen evolution.
Finally, a number of approaches for the synthesis of one-dimensional (1-D) GaN:ZnO photocatalysts were studied. A novel direct fabrication route for 1-D GaN:ZnO through gold-catalyzed atmospheric pressure chemical vapour deposition was proposed. The material characterization data indicated that the proposed method is capable of preparing 1-D GaN:ZnO nanostructures with a wide range of morphologies, including nanofibers and nanowires, via vapour–liquid–solid epitaxy. In addition, via the proposed method, the dimensions of the obtained nanomaterials can be tailored. The synthesized GaN:ZnO nanowires demonstrated promising sacrificial hydrogen evolution compared to the powder and nanofiber photocatalysts.
The work presented in this research provides an in-depth understanding of the nanoscale fabrication and optimization of GaN:ZnO photocatalysts for visible-light hydrogen generation.Chemical and Biological Engineering, Department of
Graduate
49
El-Sharif, Abdulhamid. "A thermo-economic model and a simulation analysis of a solar hydrogen system using IPSEpro." Thesis, University of Newcastle upon Tyne, 2013. http://hdl.handle.net/10443/3234.
Full textAbstract:
The high growth of world population and modern lifestyle are increasing the world’s energy consumption and fossil fuel depletion, as well as increasing environmental and economic adverse impacts. This concern is encouraging scientists and governments to create more reliable, long-lasting and environmentally benign energy sources. Renewable energy sources, particularly solar energy, are nowadays suggested as being one of the main alternative and future sources of energy to traditional fossil fuel sources. Nevertheless, the main challenge in utilizing solar energy is its high utilization cost and variability, when a storage or backup system is required. To overcome this problem, many researchers have introduced hydrogen because it is the cleanest, most abundant and safest fuel that can be used as an energy carrier or a backup system in place of batteries and fossil fuel generators. Solar hydrogen system (SHS) technologies are still immature and a few experimental projects have been installed around the world, inspiring more studies to improve these technologies towards a hydrogen-economy objective. Very little software is commercially available to use for simulation and optimization of a solar hydrogen system and no effective software has been developed for thermo-economic analysis. However, in this study a thermo-economic model library component for solar hydrogen system units such as photovoltaic (PV), photovoltaic thermal (PV/T), fuel cell and electrolyzer have been developed and validated using the commercially available software package IPSEpro. The developed models, along with the existing IPSEpro model libraries have been used to; design, optimize and simulate the entire system to meet the energy demands of a small community in three different sites. The sites considered were Sabha and Misurata in Libya, a hot region as well as Newcastle in United Kingdom in a cold region, using yearly average and a typical summer and winter actual weather data for each site. A parametric study was carried out to investigate the effects of the environmental, main operation and economic parameters on the performance and outputs of each component and the entire system. A thermo-economic analysis of the SHS showed that the PV unit has the highest factors for; (exergy destruction (exdf), destruction cost (CD), investment and destruction summation (ZTCD), and the lowest exergoeconomic (fk), followed by the fuel cell and the electrolyzer. However, the low (fk) factor of the PV and the fuel cell units indicated that a high level of attention has to be focused on increasing the unit’s exergy efficiency. Moreover, the high (fk) factor of the electrolyzer indicates that the reduction of the unit investment cost (ZT) has the priority for unit performance improvement and production cost reduction. It has also been established that, for a SHS at base condition, A. A. El-sharif iii Newcastle University the system’s exergy efficiency was 5.07% with a daily average output electricity cost of 0.23$/kWh. However, for Sabha and Newcastle, the yearly average electricity cost was 0.40$/kWh and 0.77 $/kWh respectively. This is still uncompetitive compared with (+- 0.15 $/kWh) typical current electricity market prices. In addition, the study clarified that SHS will be economically reasonable if the costs of the CO2 emission and fossil fuels consumed are considered in the analysis, particularly in Sabha and Misurata regions. Nevertheless, in these regions the photovoltaic electricity is competitive to the traditional power plant current prices. The analysis also shows that the variation in the environmental, economic and operation parameters have a significant effect on the system and its units’ performance and output costs. The parametric study mainly considered the variation of; ambient temperature (Ta), solar intensity (Sirr), module surface temperature (PV/Tc), interest rate (ir), capacity factor (CF), capital cost (CFC), lifetime (ny), price of output hot water (cwh), cell voltage (Vc), stoichiometric ratio (StH2), hot water temperature and mass flow rate. The parametric study results revealed that the optimum SHS operation conditions will achieve at the smallest ambient temperature and the highest solar intensity. It is also found that recycling the output streams, particularly the hydrogen and utilizing the output hot water of the unit’s cooling system will significantly enhance its performance and reduce the production costs. The study proves that increasing the output hot water of the PV/T system to utilize it in a low thermal energy system using an electric heater is unfeasible. More investigation is recommended to build an integrated IPSEpro thermo-economic model to utilize the SHS output hot water in a low thermal energy system using a solar collector.
50
SHAKYA, BIKRAM D. "PYROLYSIS OF WASTE PLASTICS TO GENERATE USEFUL FUEL CONTAINING HYDROGEN USING A SOLAR THERMOCHEMICAL PROCESS." University of Sydney, 2007. http://hdl.handle.net/2123/1709.
Full textAbstract:
Master of EngineeringGlobal warming and diminishing energy supplies are two major current concerns. Disposal of plastic wastes is also a major concern. The aim of this research is to address these three concerns by developing a solar powered process, using waste plastics as fuel to generate energy. Research into: i) solar concentrators for high temperature thermochemical processes, and ii) pyrolysis/gasification of waste plastics has been separately reported in the literature. In this study the aim was to bring these fields of research together to design a solar receiver-reactor suitable for the production of a synthesis gas, consisting of hydrogen, from waste plastics. To achieve this aim, studies of plastic decomposition behaviour using the thermal analysis method known as thermogravimetric analysis were conducted. Solar concentrators and their potential to be used for thermochemical processes were also studied. Firstly, the thermal decomposition behaviour of common plastics, namely low density polyethylene (LDPE), high density polyethylene (HDPE), polyethylene terephthalate (PET) and polyvinyl chloride (PET), were studied using thermogravimetry at heating rates of 5, 10, 20, 50 and 100 ºC/min. The kinetic parameters for the decomposition were determined from these experiments. Secondly, a simple solar receiver-reactor in which the plastic decomposition could be achieved was designed. The solar receiver-reactor designed was a quartz tube reactor which can be placed in the focus of a dish type parabolic concentrator capable of generating up to 3 kW in the focus of diameter 50 mm. The thermogravimetric analysis of plastic samples showed that LDPE, HDPE and PET have a single-step decomposition, whereas PVC has a two-step decomposition. The first step was related to the release of hydrogen chloride from the PVC and the second step was related to the release of hydrocarbon from the polymer backbone. If PVC is pretreated to release HCl it can be mixed with other plastics for a single step decomposition. It is likely that a single step plastic decomposition can be achieved in a directly irradiated solar receiver-reactor to generate useful gases consisting of hydrogen.