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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Análise do potencial solar térmico em um segmento do setor de alimentos e bebidas na Paraíba

Melquíades, Thiago Freire 29 April 2016 (has links)
Submitted by Viviane Lima da Cunha (viviane@biblioteca.ufpb.br) on 2016-08-02T14:37:49Z No. of bitstreams: 1 arquivototal.pdf: 2360147 bytes, checksum: e0a8bf7d97aa5aeb96223261bcdb9c0a (MD5) / Made available in DSpace on 2016-08-02T14:37:49Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2360147 bytes, checksum: e0a8bf7d97aa5aeb96223261bcdb9c0a (MD5) Previous issue date: 2016-04-29 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Solar energy is the most abundant energy source in the Earth, however, still little explored by modern society, compared to another sources. This dissertation analyzed the potential use of solar thermal collectors in the food and beverage’ industry segment in Paraíba. And specifically analyzed through regional indicators, the relevance of potential segments of food and beverages from Paraiba for the use of Solar Heating Systems (SAS). It was also analyzed the technical and economic feasibility of using solar thermal collectors in a in a manufacturing company of ice cream and other ices, located in João Pessoa. It was found through the environmental impacts Life Cycle Assessment associated with the pasteurization process in an ice cream manufacturing company and other ices in Joao Pessoa, comparing the replacement of atmospheric burner LPG (Liquefied Petroleum Gas) to Solar Heating System. It was analyzed the Global Solar Radiation Series, from July 2007 to December 2013 in the city of Joao Pessoa Paraiba, using the ARIMA family models and testing the models estimated in 2014 forecast. The methodologies used were: regional analysis, through location and regional measures, life cycle assessment using the IPCC 2013 GWP 100a method, the Box and Jenkins method of time series analysis; and technical and economic analysis through NBR 15569 and financial indicators. The main results were: the sub-sectors of the food industry are distributed similarly between mesoregions. The SAS provided smaller environmental impact as compared to atmospheric burner. The SARIMA model (2,1,0) (2,1,3) 12 was the one that provided the best fit global solar radiation for 2014. It was concluded that the use of solar thermal collectors in the segment of the food and beverage industry in Paraíba is feasible according points of view technical, economic and environmental. / A energia solar é a fonte energética mais abundante do nosso planeta, porém, ainda pouco explorada pela sociedade moderna se comparada com outras fontes. Essa dissertação analisou as potencialidades do uso de coletores solares térmicos em um segmento da indústria de alimentos e bebidas na Paraíba. E, de forma específica, primeiramente analisou por meio de indicadores regionais, a relevância dos segmentos potenciais de alimentos e bebidas paraibanos para o uso de Sistemas de Aquecimento Solar (SAS). Segundamente, analisou a viabilidade técnica e econômica do uso de coletores solares térmicos em uma em uma empresa de fabricação de sorvetes e outros gelados comestíveis, localizada em João Pessoa. Terceiramente, verificou por meio da Avaliação de Ciclo de Vida os impactos ambientais associados ao processo de pasteurização em uma empresa de fabricação de sorvetes e outros gelados comestíveis em João Pessoa, comparando a substituição do queimador atmosférico de GLP (Gás Liquefeito de Petróleo) por um Sistema de Aquecimento Solar. Por fim, analisou a Série de Radiação Solar Global, no período de julho de 2007 a dezembro de 2013 do município de João Pessoa na Paraíba, por meio dos modelos da família ARIMA e testando os modelos estimados na previsão de 2014. As metodologias utilizadas foram: análise regional; por meio das medidas de localização e regionais, análise de ciclo de vida pelo método IPCC 2013 GWP 100a, o método Box-Jenkins de análise de séries temporais; e análise técnica e econômica pela NBR 15569 e indicadores financeiros. Os principais resultados foram: os subsetores do setor alimentício são distribuídos de forma semelhante entre as mesorregiões. O SAS proporcionou menores impactos ambientais, quando comparado ao queimador atmosférico. O modelo SARIMA (2,1,0) (2,1,3)12 foi o que forneceu melhor ajuste da radiação solar global para 2014. Concluiu-se que o uso de coletores solares térmicos no segmento da indústria de alimentos e bebidas na Paraíba é viável dos pontos de vista técnico, econômico e ambiental.
2

Desenvolvimento de heliostato para geração heliotermica em torres solares

Silvestre, Alysson Domingos 22 April 2016 (has links)
Submitted by Márcio Maia (marciokjmaia@gmail.com) on 2016-08-08T12:09:17Z No. of bitstreams: 1 arquivototal.pdf: 3228826 bytes, checksum: ddfaa133f9f8a9a5a4d1f5233fb205a5 (MD5) / Made available in DSpace on 2016-08-08T12:09:17Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 3228826 bytes, checksum: ddfaa133f9f8a9a5a4d1f5233fb205a5 (MD5) Previous issue date: 2016-04-22 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / With the increase of global perspectives regarding renewable energy and the use of concentrated solar thermal energy, with the goal of increasing the flow of solar radiation incident on the thermal has been shown to be a viable solution for electric power generation. The heliostats devices have the ability to track the Sun and reflect the radiation in a pre-set fixed point, usually known as solar tracking Tower in the middle of the field of heliostats devices. The solar towers have been aim of studies because they have a great potential for electric generation. The higher the desired concentration values of the system, the higher the accuracy requirements tracking and reflection of the heliostats, and the quality of reflective surfaces will be. This study aims to design and construction of the heliostat of two degrees of freedom for power generation in solar Tower systems using control methods for tracing and reflection on LabView platform. Applying tracking algorithms based on the solar behavior equations and mechanical design, allowing a two degrees’ freedom dynamic, it was gain results with 0.201 degrees in precision in the tracking of radiation reflection. / Com o aumento das perspectivas mundiais a respeito das energias renováveis e a utilização da energia solar térmica concentrada, com o objetivo de aumentar o fluxo de radiação solar incidente em sistemas térmicos tem se mostrado uma solução viável para geração de energia elétrica. Os dispositivos heliostatos tem a capacidade de rastrear o sol e refletir a radiação em um ponto fixo pré – estabelecido, normalmente conhecido como torre solar localizando se ao meio de um campo de dispositivos heliostatos. As torres solares tem sido alvo de estudos por possuir um grande potencial para geração de energia elétrica. Quanto maior os valores de concentração pretendido do sistema, maiores serão os requisitos de precisão de rastreamento e reflexão do heliostato e da qualidade das superfícies refletoras. Este trabalho tem como objetivo de projeto e construção de um heliostato de dois graus de liberdade para geração de energia em sistemas de torres solares utilizando métodos de controle para rastreamento e reflexão ótima em plataforma LabView. Aplicando algoritmos de rastreamento baseado nas equações de comportamento solar e projeto mecânico permitindo uma dinâmica de dois graus de liberdade foi obtido resultados de 0,201 graus de precisão no rastreamento de reflexão da radiação.
3

Optimisation d'échangeurs à films ruisselants / Optimization of falling film exchangers

Cellier, Nicolas 12 April 2018 (has links)
On considère le transfert de chaleur au travers d'un film liquide de faible épaisseur s'écoulant par gravité le long d'un plan incliné, l'objectif étant de comprendre les mécanismes d'intensification des transferts par l'hydrodynamique du film et d'optimiser la géométrie d'un échangeur.Un modèle simplifié fondé sur une méthode intégrale aux résidus pondérés appliquée aux équations de Navier-Stokes et de Fourier a été développé. Un outil de résolution de système d'équations aux dérivées partielles utilisant la méthode des lignes a été écrit. Celui-ci utilise les différences finies pour discrétiser les dérivées spatiales et un schéma Runge Kutta implicite d'ordre élevé couplé à un contrôleur de pas de temps afin de garantir une résolution stable et performante des modèles.Ce modèle simplifié nous a permis de mettre en avant les liens entre l'hydrodynamique (et en particulier la recirculation ayant lieu au sein de la crête des ondes propagatives) et l'intensification des phénomènes de transferts, lien confirmé par résolution des équations primitives du problème.En effet, une étude paramétrique de l'intensification des transferts sur un élément représentatif d'une plaque d'échangeur par une excitation monochromatique en entrée d'écoulement a été menée. Elle montre le lien entre la présence de recirculation au sein des ondes propagatives et accroissement des transferts.Le modèle a été étendu afin de prendre en compte un fond à géométrie variable. Des travaux préliminaires sur l'effet d'un fond ondulé sur les transferts indiquent qu'une faible inclinaison soit nécessaire pour qu'un effet notable soit observé / We consider the heat transfer across a thin liquid film flowing by gravity along an tilted plane. This work aims at the identification of the mechanisms of heat transfer intensification and the optimization of the geometry of a plate exchanger.A simplified model based on weighted residual integral method applied to Navier Stokes and Fourier equations has been developed. A tool for solving system of partial derivative equations using the method of line has also been written. Spatial discretization is dealt with finite differences. A high order implicit Runge Kutta scheme with an adaptative time stepping, allows a stable and efficient resolution.This simplified model allowed us to link the fluid's dynamics (and especially the presence of recirculations under traveling wave crests, alos called roll waves) with transfer intensification. This link has been confirmed solving the primitive equations . Indeed, a parametric study of the transfer intensification on a signature/representative element of an exchanger plate by a monochromatic frequency has been conducted showing that transfer intensification is related to the onset of roll waves.The effect of a variable wall goemetry has been included to the model. Preliminary work points out the need for a low inclination to yield a significant effect on transfer intensification
4

Performance Calculations and Optimization of a Fresnel Direct Steam Generation CSP Plant with Heat Storage

Schlaifer, Perrine January 2013 (has links)
This master thesis deals with the performance calculations of a 9MW linear Fresnel CSP plant withdirect steam generation built by the Solar Division of the CNIM Company. The aim was to calculate theannual electricity production taking into account the weather conditions as well as some steam storage.At first, a steam accumulator model was developed with Excel, in order to estimate the pressureevolution in the tanks during the charging, storage and discharging processes. The data obtained withthis model was then integrated to the thermodynamic cycle model, programmed with Excel, whichcalculated the electrical power production knowing the thermal power available in the solar field. Theelectricity production calculations were made every 600 seconds during one year.To improve the results accuracy, the influence of the plant location slope was estimated, calculating theequivalent azimuth and elevation angles in a new spherical coordinates system. For an average slope of4.21° at the plant location, the annual thermal energy gain is 14.4% (with a gain up to 60% duringwinter days) and the annual electricity production is increased by 12.59%. The influence of frost on themirrors during cold and humid nights was also estimated with a simple model of the energy needed toheat up a constant layer of ice. Depending on the assumptions, the electricity production losses werebetween 1.27 and 2.84% of annual electricity production. The losses due to plant shutdowns set by theelectrical network manager RTE during the snowmelt months were also estimated. The annualelectricity production could decrease by 8.02 to 11.57 % because of the load management, dependingon the days during which the plant is shutdown.Finally, an economic optimisation was led with prices estimated by CNIM, which gave an optimal solarfield design with 31 lines and 5 steam accumulators. The payback time would then be 9.887 years.
5

Identification de caractéristiques réduites pour l'évaluation des performances des systèmes solaires combinés / Identification of restricted characteristics for the evaluation of solar combisystems performance

Leconte, Antoine 14 October 2011 (has links)
Les Systèmes Solaires Combinés (SSC), qui répondent aux besoins d'Eau Chaude Sanitaire (ECS) et de chauffage d'un bâtiment, peuvent réaliser des économies d'énergie conséquentes. Cependant, leurs performances dépendent énormément de leur conception, de leur installation et surtout de l'environnement énergétique auquel ils sont confrontés (c'est-à-dire les besoins thermiques du bâtiment et les ressources solaire). A ce jour, il est impossible de prédire l'économie d'énergie qu'un SSC permettrait de réaliser. Il n'existe aucun test normatif permettant la caractérisation des performances des SSC, ce qui pénalise le développement de son marché. La méthode SCSPT (Short Cycle System Performance Test) a pour objectif d'évaluer les performances annuelles des SSC à partir d'un test de 12 jours sur banc d'essai thermique semi-virtuel. Sa particularité est de considérer chaque système comme un unique ensemble ce qui permet, contrairement aux méthodes de type « composant », de prendre en compte les vraies interactions entre les éléments des SSC lors de leur test. Elle montre de très bons résultats mais ceux-ci sont limités à la prédiction des performances du système pour le seul environnement énergétique adopté lors du test. Ces travaux de recherche proposent une amélioration de la procédure SCSPT en lui ajoutant une étape d'identification d'un modèle générique de SSC à partir de données expérimentales. De cette manière, le modèle identifié pourrait simuler le comportement du SSC testé sur différentes séquences annuelles pour n'importe quel environnement énergétique et ainsi caractériser ses performances (à l'aide de la méthode FSC par exemple). L'architecture proposée pour ce modèle est du type « Boite Grise ». Elle mêle une partie « Boite Blanche » composée d'équations physiques caractéristiques de certains éléments du SSC et une partie « Boite Noire » constituée principalement d'un réseau de neurones artificiels. Une procédure complète est conçue pour entrainer et sélectionner un modèle correspondant aux SSC à partir des données de leur test sur banc d'essai semi-virtuel. Cette approche a été validée numériquement grâce à des simulations de trois modèles détaillés de SSC sous TRNSYS. En comparant leurs résultats annuels avec ceux des modèles « Boites Grises » entrainés à partir d'une séquence 12 jours, ces derniers sont capables de prédire la consommation en énergie d'appoint de manière très précise pour 27 environnements énergétiques différents. L'application concrète de cette nouvelle procédure a été réalisée expérimentalement sur deux SSC réels. Elle a confirmé que l'approche était pertinente et cohérente. Elle a également permis d'identifier quelques améliorations pour que la méthode soit totalement opérationnelle. Ce travaux offrent une base pour avancer dans l'élaboration d'une méthode complète et fiable de caractérisation des SSC qui pourraient conduire à une nouvelle procédure de normalisation (et d'envisager un étiquetage énergétique des SSC. / Solar Combi Systems (SCS) can be very efficient at reducing heat energy bill of a house but their performances depend on the environment they are working in (type of climate and thermal quality of the building). Currently it is impossible to predict how much energy a SCS would save before its installation. There is no standard test to characterize SCS performances and this curbs its market development. The Short Cycle System Performance Test (SCSPT), that is being developed at the French National Institute of Solar Energy (INES, Chambery, France), aims to evaluate SCS annual performance from a test on a semi-virtual test bench. Its special feature is to test the whole system as only one part, unlike “component testing” which can't consider real interaction between combisystems components. The SCSPT method shows good results but performance prediction is limited to only one environment (i.e. one set of system sizing, type of climate and building thermal quality, corresponding with the test). This work proposes an improvement of the SCSPT procedure by identifying a global SCS model from the test data. In this way, the identified model would be able to simulate the tested SCS behaviour in any environment and thus to characterize its performances. The proposed model to identify is a “grey box” model, mixing a “white box” model composed of known physical equations and a “black box” model, which is an Artificial Neural Network (ANN). A complete process is developed to train and select a relevant global SCS model from such a test on semi-virtual test bench. This approach has been validated through numerical simulations of three detailed SCS models. Compared to their annual results, “grey box” SCS models trained from a twelve days sequence are able to predict energy consumption with a good precision for 27 different environments. Concrete experimentations of this procedure have been applied to two real systems. They have confirmed that the approach is pertinent and revealed some points to improve in order to get it totally operational. This work offers major basis to get ahead with a complete method to characterize SCS that could lead to develop a standardization method from performance evaluation (and eventually complete the European norm EN 15316 for instance) and to plan a combisystems performance labelling.
6

Optimisation, design, development, and trial of a low-cost solar oven with novel concentrator geometry

Berryman, Ian January 2016 (has links)
A promising and novel solar concentrator design has been thoroughly investigated and optimised. A prototype concentrator based on this novel geometry was validated using ray tracing techniques. This ray tracing demonstrated the comparative performance of this novel concentrator in regards to equivalent parabolic dishes. The effect of mirror surface normal errors on performance was established using Monte-Carlo based ray tracing code, which agreed well with the optical performance of this prototype which was determined experimentally. A need for low-cost solar cookers to replace bio-mass worldwide was identified, and the concentrator design was then developed as a low-cost solar oven. Despite existing in some number, no current design is able to achieve high performance at low-cost. An industrial partner, Dytecna, was initially involved in the process of this development of the system as a solar cooker. In support of a field trial for the solar cooker developed with Dytecna, a detailed thermal model of the oven was developed. A low-cost lightmeter was constructed and calibrated in order to measure the direct normal irradiance during the field trial in Italy. Laboratory work provided baseline results for the heating of various thermal masses in the oven. The Italian field trials provided a wealth of feedback into the design of the system and many valuable results. The solar cooker was able to bring 0.75L of water to the boil in 33 minutes with an average heat throughput of 203W. Important benchmark results and practical experience of several competing receiver materials was obtained; further lab testing provided more accurate measurements of the receivers' performances. The experiences of the Italian field trial were fed back into the design of a subsequent prototype, intended for a much larger field trial in Tanzania. Improvements in the hotplate, receiver material, and the oven were all incorporated into the design. Additionally, the structure of the solar cooker was redesigned to incorporate a low-cost wooden construction. Supporting work was conducted for the month long trial in which 8 solar cookers would be distributed to families in Tanzania. The field trial in Tanzania provided a wealth of user feedback into the design. At the same time the new solar cooker exceeded previously established performances in Italy. The new design was able to provide an average of 246W of heat to 1kg of water, which was brought to boiling point in 25 minutes. This represents a heating efficiency of 66% compared to the incident solar flux on the hotplate. In response to findings during the Tanzanian trials, further laboratory work was conducted into establishing the reflectivities of low-cost candidate mirror materials. Throughout all phases of the project the design of the solar cooker was refined and improved with the goal of a solar cooker design that could reach price-point, performance, and usability standards which would ensure market success.
7

Films d’oxydes de vanadium thermochromes dopés aluminium obtenus après un recuit d’oxydation-cristallisation pour applications dans le solaire thermique / Thermochromic Al-doped vanadium dioxide thin films obtained after an oxidation crystallization annealing for solar thermal applications

Didelot, Aurélien 15 December 2017 (has links)
Ces travaux sont issus d’une thèse CIFRE et de la collaboration entre la société Viessmann Faulquemont et le laboratoire de recherche l’Institut Jean Lamour. Ayant pour objectif de fortement réduire les problèmes liés aux hautes températures de stagnation dans les panneaux solaires thermiques, nous présentons une nouvelle génération d’absorbeur solaire intelligent à base de dioxyde de vanadium. Le dioxyde de vanadium, noté VO2, est un matériau présentant une transition métal-isolant (MIT) à une température critique (Tc) de 68°C. Cette transition s’accompagne d’une modification de la structure cristallographique. Le VO2 se trouve sous une forme monoclinique VO2(M) à basse température, et sous une forme rutile VO2(R) à haute température. Ce changement de structure s’accompagne d’une forte modification des propriétés optiques. La synthèse de ces films est réalisée à partir d’une couche de vanadium métallique déposée par pulvérisation. Un recuit d’oxydation-cristallisation est ensuite effectué pour obtenir une couche d’environ 400 nm de dioxyde de vanadium. Afin d’optimiser et d’augmenter la variation d’émissivité (Δε), la température et la durée du recuit sont étudiées. Dans un second temps, un dopage aluminium est réalisé afin d’augmenter l’effet de la transition thermochrome. Après optimisation, le passage au niveau industriel est un succès et des prototypes de taille 1 sont réalisés à partir de la couche thermochrome et de la couche standard afin d’être comparés dans des conditions normales d’utilisation / This work is a CIFRE thesis between VIESSMANN Faulquemont SAS society and the laboratory Institut Jean Lamour. In order to strongly reduce the problems associated with high stagnation temperature, we present a new generation of solar absorbent layers based on a smart thermochromic vanadium dioxide thin film. Vanadium dioxide (VO2) is a material which exhibit a metal insulator transition (MIT) at a critical temperature of 68°C (Tc). The transition is accompanied by a change in crystallographic structure VO2(M), while a rutile-like structure VO2(R) is obtained at high temperature. This structural change induces a drastic modification of the optical properties. The synthesis of vanadium-based films is performed using magnetron sputtering. We proceed to a subsequent annealing in air to form crystalline films of about 400 nm thickness. In order to increase the thermochromic effect of our thin film (Δε) we study the temperature and duration of the annealing. In a second time we try to increase the emissivity switch between the low and high temperature phase by adding an aluminum doping. After optimization, scale up have been successfully done and the optimized parameters have been used to build a prototype of thermochromic selective layer that has been compared to the standard industrial solar absorber
8

Conception et optimisation d'un capteur solaire thermique innovant adapté à la rénovation énergétique grâce à l'intégration du stockage / Design and optimization of an inovating thermal solar collector adapted to the energy restoration thanks to the storage integration

Vidigal Duarte Souza, Jeronimo 05 March 2012 (has links)
La part de consommation d'énergie primaire d'eau chaude sanitaire (ECS) dans des bâtiments à basse consommation (BBC) devient proportionnellement importante quand comparée aux autres postes. Actuellement, l'intégration des systèmes dans les nouveaux bâtiments ne présente pas de difficulté. En revanche, le marché de la rénovation est mal exploité, et une des contraintes importante est le placement du ballon de stockage. Dans le cas où le ballon doit être placé en dehors du bâtiment, les solutions existantes ne sont pas satisfaisantes, ni d'un point de vue thermique (fortes pertes), ni d'un point de vue esthétique (réservoir visible à l'extérieur). Dans le cadre de cette thèse, nous avons étudié une solution innovante visant à intégrer le stockage au capteur, afin de permettre une intégration complète du système au niveau de la toiture. Le critère énergétique nous a conduit à proposer un volume de stockage totalement isolé où l'apport de chaleur se produit en partie basse. Nous réalisons dans le cadre de la thèse une étude expérimentale d'une cavité à haut rapport de forme, qui nécessite la réalisation d'un système de stratification. Ce système, une plaque, a été étudié numériquement pour optimiser le placement du fluide en partie haute. Enfin un modèle global a été conçu pour les simulations de performance annuelle. Ce modèle se montre satisfaisant, et montre que la performance du système est légèrement inférieure aux systèmes classiques (thermosiphon). Les pertes thermiques ont été le facteur le plus pénalisant. Le dimensionnement d'un prototype a été réalisé, et ce dernier sera testé au cours de l'année 2012. / The primary energy consumption of domestic hot water (DHW) in low energy house becomes proportionately large when compared to other energy consumptions. In new buildings, the integration of DHW systems do not present any difficulty. However, the thermal renovation market is poorly operated, with the storage's placement as the main constraint. When the storage must be placed outside the building, nowadays the solutions are not satisfactory, or by a thermal point of view (high losses), or an aesthetic point of view (tank visible from outside). In this thesis we studied an innovative solution of an integrated storage collector, allowing full integration at the roof and completly insulated. The storage is heated at the bottom. A cavity with high aspect ratio has been studied experimentaly and the cavity requires a stratification system. This system, a plate, was numerically studied to optimize the placement of the fluid at the top. Finally a global model was developed for annual performance simulations. This model proves satisfactory and shows that system performance is slightly lower than conventional systems (thermo- siphon). Heat loss was most detrimental factor. The design of a prototype was produced, and it will be tested during the year 2012.
9

Réalisation d'un absorbeur solaire sélectif pour centrale CSP associant dépôt en couches minces et texturation de surface / Development of CSP selective solar absorber combining thin layers coating and textured surface

Bichotte, Maxime 20 June 2017 (has links)
Le contexte du réchauffement climatique entraîne un développement des technologies CSP (Concentrated Solar Power). La réduction des coûts de production de ces technologies passe par une amélioration de la durabilité et de l'efficacité des composants des centrales solaires. Les températures de fonctionnement élevées du CSP (250-600°C) nécessitent d'employer des absorbeurs spectralement sélectifs afin de limiter les pertes par radiation. Cette thèse propose une architecture originale d'absorbeurs sélectifs stables à haute température sous air en combinant un dépôt de TiAlN en couches minces avec un réseau de diffraction. L'ajout d'une texturation de surface augmente l'absorption solaire du dépôt par un effet d'absorption et de gradient des indices optiques effectifs conduisant à une augmentation du rendement photothermique de l'absorbeur. Dans ce mémoire, la modélisation du comportement optique des absorbeurs texturés, les méthodes de fabrication du réseau de diffraction ainsi que le dépôt des couches minces par PVD et PECVD seront abordés et les mesures expérimentales seront comparées aux modélisations. L'analyse des absorbeurs texturés fabriqués confirme un gain de rendement photothermique pouvant atteindre +3% ainsi qu'une stabilité thermique remarquable à 500°C sous air jusqu'à 300 h de recuit / The global warming context reinforces the development of CSP technologies. Cost reduction of CSP requires the improvement of component durability and efficiency. The solar absorbers should be spectrally selective since the high working temperatures of CSP plants increase the radiative thermal losses. This thesis proposes an original, spectrally selective absorber structure combining TiAlN based coatings and diffractive gratings. The surface texturing provided by the diffractive gratings improves the solar absorption of the thin coating by an effective optical index gradation effect leading toincreased photothermal efficiency. In this thesis, the modeling of the textured absorber’s optical behavior, fabrication methods of diffractive gratings, as well as layer deposition by PVD/PECVD will be discussed. Experimental measurements will be compared to the theoretical modelling. The experimental analysis of textured absorbers confirms the increase of photothermal efficiency by almost 3%, as well as a good thermal stability at 500°C in air for 300 hours of annealing
10

Stárnutí teplonosných kapalin v termických solárních systémech a propan-1,3-diol jako nová možnost / Degradation of Heat Transfer Fluids in Thermal Solar Systems and Propane-1,3-diol as a New Option

Mikšík, František January 2018 (has links)
Stárnutí teplonosných kapalin na organické bázi je dlouhodobým problémem, který je znám od počátku jejich používání. První část této disertační práce je tak věnována případové studii funkčního experimentálního systému, který byl jako nový naplněn teplonosnou kapalinou na bázi propan-1,2-diol a pozorován po období 7 let. Pro analýzu stárnutí kapaliny v tomto systému byly sledovány základní provozní vlastnosti kapaliny jako jsou hustota, viskozita, teplota tuhnutí, pH a obsah kovů. Skrze tyto vlastnosti tak bylo sledováno stárnutí kapaliny nepřímo. Přímé sledování stárnutí bylo posléze provedeno analýzou degradačních produktů, jako jsou organické kyseliny a změny ve složení směsi pomocí izotachoforézy a hmotnostní spektrometrie. Pro srovnání byly taktéž analyzovány vybrané vzorky z několik dalších systémů plněných identickou kapalinou s prokazatelně pokročilou formou degradace. V druhé části práce jsou představeny základní fyzikálně-chemické vlastnosti směsí propan-1,3-diolu s vodou a jejich analytické hodnocení a matematické modelování pro universální použití jakožto nového základu pro nemrznoucí teplonosné kapaliny. Na základě dostupných informací je pak hodnocena použitelnost této směsi. Výhoda propan-1,3-diolu je spatřována především ve výrobě z obnovitelných zdrojů a v některých fyzikálních a chemických vlastnostech, které dle dosavadních poznatků předčívají doposud používané glykolové směsi.

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