Tesi sul tema "Soilihi"

Depuis la proclamation de l'indépendance unilatérale des Comores le 6 juillet 1975, par Ahmed Abdallah, l'État comorien n'a cessé de traverser de multiples crises politiques et institutionnelles qui conduisent spécialistes et non-spécialistes à revenir sur ce moment fondateur. Dans l'historiographie comme dans les mémoires collectives, deux figures ont particulièrement incarné deux voies opposées. Celle d'Ahmed Abdallah (1919-1989), « le père de l'indépendance » (mbaba wahindépendasi) apparaît comme le garant de valeurs conservatrices. A l'inverse, Ali Soilihi (1937-1978), issu d'une autre génération, incarne un modèle de changement radical associé aux idéaux révolutionnaires et anti-impérialistes des années 1960 et 1970. Au-delà de cette opposition classique entre conceptions politiques et rapports au monde peu conciliables, la thèse entend revenir de manière inédite sur les conditions d'arrivée au pouvoir Ali Soilihi et d'autres représentants d'une génération marquée par le contexte global de la décolonisation et de la circulation de modèles politiques socialistes venus du Bloc de l'Est comme d'Afrique. A partir de sources nouvelles ou peu connues, elle vise à retracer avec précision l'histoire politique et sociale du régime instauré par Ali Soilihi à la suite d'un coup d'État. Elle montre que la révolution comorienne a d'abord suscité l'enthousiasme parmi les plus jeunes notamment. Néanmoins, les dérives autoritaires du régime et ses difficultés profondes à affronter de multiples défis ont fragilisé ses assises et alimenté une opposition de plus en plus massive
Ever since Ahmed Abdallah made the unilateral declaration of independence of on 6 July 1975, the state of Comoros has experienced multiple political and institutional crises which have led specialists and non-specialists to revisit this foundational moment. In historiography as well as in popular memory, two figures in particular have come to represent two opposed trajectories. On the one hand, the figure of Ahmed Abdallah (1919-1989), the 'father of independence' (mbaba wahindépendasi), serves as the guarantor of conservative values. On the other hand, Ali Soilihi (1937-1978), a man from a different generation, represents a radical model of change associated with the revolutionary and anti-imperialist ideology of the 1960s and 1970s. Moving beyond this classic opposition between irreconcilable political ideas and external relationships, this thesis takes a fresh approach to the circumstances which brought to power Ali Soilihi and other members of a generation who were influenced by both the global context of decolonisation and the circulation of socialist ideas from the Eastern Bloc as well as Africa. Using new or little known sources, it seeks to retrace carefully the political and social history of the regime introduced by Ali Soilihi following a coup d'état. It shows that the Comorian revolution initially aroused enthusiasm, especially among the youth. However, the authoritarian drift of the regime and its profound inability to confront multiple challenges weakened its foundations and fuelled an increasingly strong opposition

This thesis considers the sources of airborne particulate matter and dark smoke in the UK and its implication in the soiling of materials. The role of particulate elemental carbon receives special consideration. Results of emission inventories reveal that diesel emissions are responsible for 60% of dark smoke in urban areas and 25% on a national level. Particulate emissions have been identified as being largely responsible for the soiling of building fabric in urban areas. It is now being increasingly accepted that vehicle exhaust emissions make major contributions to this fabric soiling as well as to the deterioration of atmospheric quality within the urban environment. Field work has been carried out at nine locations within metropolitan London, where a variety of materials was displayed. The materials' reflectance was measured at regular intervals together with pollution and meteorological conditions for alperiod of eighteen months. Soiling rates in the range of -0.02-4.5 yr were recorded. Particulate samples were collected by a variety of methods and soiling rates were measured in a traffic tunnel to assess the rate of sliling in the absence of rainfall. Soiling rates of -0.5-0.8 yr were recorded. Daily soiling rates for sheltered and exposed materials were measured in a third field study. A cost-benefit analysis of the building soiling problem was also undertaken. The costings were achieved by a survey of UK stone cleaning companies to identify their turnover, market characteristics, mode and cleaning frequencies. The benefits were obtained by interviewing typical clients of the stone cleaning companies to ascertain the amount they spent per annum on stone cleaning and the benefits accrued as a result of cleaning

Soiling, the process of particle deposition onto surfaces, has been studied since the 40’s. Initially, it was studied as a physical process, including types of adhesion forces, and later its effect on performance of solar energy conversion technologies was analyzed, such as in photovoltaics and concentrated solar power. This thesis approaches the problem from a cause-effect point of view and how it can be mitigated. Soiling is characterized, mineral and chemically, using a Scanning Electron Microscope. Polycristalline photovoltaic modules deposition rates are retrieved and related to environmental parameters, as well as, to long-range Saharan desert dust transport, a non-local phenomenon. Attention is also given to Spring, where atmospheric pollen concentration enhances soiling. The effect of soiling on the photovoltaic optimum tilt angle, for fixed and multiple angles, is studied along with a simple economic analysis. Cleaning schedules, for a desired system efficiency, are calculated based on annual soiling. Mirror soiling, related to concentrated solar power technologies, is also analyzed. Soiling rates are calculated and interlinked with environmental parameters such as air temperature, relative humidity, particulate mater concentration and vertical wind speed. From a collaboration with the Institut de Recherche en Energie Solaire et Energies Nouvelles, Morocco, an insightful study is made comparing soiling effect between Portugal and Morocco. A passive cleaning method, impregnated anti-soiling coating, is tested. Comparison between coated and uncoated mirrors is done to evaluate its performance and conclude if it stands as a possible tool to reduce water consumption in cleaning solar harvesting technologies; Resumo: Sujidade em Tecnologias de Conversão de Energia Solar: Avaliação e Mitigação A sujidade, o processo de deposição de partículas em superfícies, tem sido estudada desde os anos 40. Inicialmente, começou a ser estudada como um processo fisico, incluindo tipos de forças de adesão, e mais tarde o seu efeito no desempenho de tecnologias de conversão de energia solar, como na tecnologia fotovoltaica e e de concentração. Esta tese aborda este problema de um ponto de vista causa-efeito e como pode ser mitigado. A sujidade é caracterizada, mineral e químicamente, usando um Microscópio Eletrónico de Varrimento. As taxas de deposição em módulos fotovoltaicos policristalinos são calculadas e relacionadas com parametros ambientais, tal como com o transporte de longo alcance de areia do deserto do Sahara, um fenómeno não local. Também é dada atenção à Primavera, onde a concentração de pólen na atmosfera aumenta a sujidade. O efeito da sujidade no ângulo de inclinação fotovoltaico óptimo, para ângulos fixos e múltiplos, é estudado juntamente com analises económicas. Calendários de limpeza, para uma eficiência de sistema desejada, são calculados com base em dados anuais de deposição de particulas. A sujidade em espelhos, relacionada com as tecnologias de energia solar concentrada, é também analisada. As taxas de deposição são calculadas e relacionadas com parâmetros ambientais, tais como temperatura do ar, humidade relativa, concentração de particulas e velocidade vertical do vento. A partir de uma colaboração com o Institut de Recherche en Energie Solaire et Energies Nouvelles, Marrocos, fez-se um estudo esclarecedor, comparando o efeito da sujidade entre Portugal e Marrocos. Um método passivo de limpeza, revestimentos impregnados anti-sujidade, é testado. A comparação entre espelhos revestidos e não revestidos é realizada para avaliar o seu desempenho e concluir se é um método importante para alcançar uma redução no consumo de água na limpeza de tecnologias de energia solar.

Les comores ont herite de la colonisation francaise des desequilibres economiques financiers, commerciaux, alimentaires, sociaux, agro-ecologiques et demographiques. Ali soilih, agronome de formation, et fort d'une experience politico-professionnelle a tente de mettre fin a ces desequilibres. Il s'etait fixe comme objectifs : l'auto-suffisance alimentaire, le plein emploi et le niveau des recettes d'exportation. Il avait engage des reformes institutionnelles, sociales culturelles, politiques et economiques. La persistance des desequilibres, l'absence de ressources humaines et financieres suffisantes, l'exiguite des iles, la brutalite des methodes et la crise internationale ont compromis cette experience de developpement auto-centre. Mais ses enseignements sont tels que de nombreux comoriens souhaitent refaire l'experience avec les lecons du passe.

La salissure des modules photovoltaïques (PV) dégrade grandement leurs performances dans les environnements désertiques. Les études précédentes en extérieur ont tendance à trouver de faibles corrélations entre les taux de salissure et les paramètres météorologiques. On pensait que l'une des raisons était le long intervalle de mesure - jours ou semaines - des techniques traditionnelles de mesure des salissures sur le terrain. Dans la présente étude, un «microscope de souillure extérieur» (OSM) a été développé pour mesurer le dépôt et le détachement de particules de poussière individuelles, toutes les 10 minutes, dans des conditions extérieures, de jour comme de nuit. En utilisant une paire d'OSM graissés et non graissés, il était en outre possible de séparer les salissures en trois vitesses de flux de poussière de composants - dépôt, rebondissement immédiat et remise en suspension retardée. Les OSM ont été utilisés pour mesurer les taux de flux dans des expériences sur le terrain à Doha, au Qatar. La nouvelle méthode a révélé des effets explicatifs de paramètres environnementaux qui avaient auparavant été obscurcis par de longs intervalles de mesure des salissures et des taux de flux de poussière confondus. L'OSM pouvait également mesurer l'apparition et la croissance de gouttelettes de condensation microscopiques dans des conditions de terrain et de laboratoire. De telles expériences, ainsi que des mesures isothermes et des analyses de composition, ont démontré que la condensation sur les surfaces sales au terrain d’études était fortement influencée par la présence de matière hygroscopique dans la poussière autre que NaCl. En raison de cette matière, la condensation microscopique peut persister à la surface même si elle est bien supérieure à la température du point de rosée. Les résultats de l'étude suggèrent que la souillure des modules photovoltaïques pourrait être atténuée en tirant parti des variations naturelles des conditions météorologiques au cours de la journée
Soiling of photovoltaic (PV) modules greatly degrades their performance in desert environments. Previous field studies have tended to find weak correlations between the soiling rate and weather parameters. It was thought that one reason was the long measurement interval — days or weeks — of conventional field soiling measurement techniques. In the present study, an “outdoor soiling microscope” (OSM) was developed able to measure deposition and detachment of individual dust particles, every 10 minutes, in outdoor conditions, day and night. By using a greased and ungreased pair of OSMs, it was further possible to separate soiling into three component dust flux rates — deposition, immediate rebound, and delayed resuspension. OSMs were used to measure flux rates in field experiments in Doha, Qatar. The novel method revealed explanatory effects of environmental parameters that had previously been obscured by limits of conventional long soiling measurement intervals and confounded dust flux rates. The OSM could also measure the onset and growth of microscopic condensation droplets in field and laboratory settings. Such experiments, along with isotherm measurements and composition analysis, demonstrated that condensation on soiled surfaces at the test site was strongly influenced by the presence of hygroscopic matter in the dust other than NaCl. Because of such matter, microscopic condensation could persist on both hydrophilic and hydrophobic surfaces well above the dew-point temperature. Results of the study suggest that soiling of PV modules might be mitigated by taking advantage of natural time-of-day variations in weather conditions

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A possibilidade de redução na oferta de combustíveis convencionais aliada ao crescimento da demanda por energia e a crescente preocupação com o meio ambiente impulsionam a pesquisa e desenvolvimento de fontes alternativas de energia menos poluentes, renováveis e que produzam menor impacto ambiental. Dentre estas alternativas, destaca-se a energia solar, fonte disponível e passível de ser explorada a partir de todas as suas potencialidades. Atualmente, uma das vias tecnológicas de aproveitamento da fonte solar para geração de energia é a heliotermia, também conhecida como energia solar concentrada ou Concentrated Solar Power (CSP), baseada na utilização de superfícies espelhadas que refletem e concentram a radiação solar direta com o objetivo de convertê-la em energia térmica, a partir da qual se gera vapor d’água que irá acionar um ciclo termodinâmico reversível que converte calor em trabalho, conhecido como Rankine. O soiling consiste no depósito de diferentes tipos de sujeiras em uma superfície exposta em um dado ambiente. No caso de usinas CSP de torre central, o acúmulo gradativo de poeira, sujeira ou até mesmo de excremento de pássaros nas superfícies refletoras dos heliostatos causa uma redução significativa na quantidade de radiação solar que atinge o receptor posicionado no alto da torre e diminuição da eficiência de todo o sistema. Assim, faz-se necessário manter um alto fator de refletividade nas superfícies espelhadas dos heliostatos por meio de uma limpeza regular. Este trabalho apresenta a proposta de um mecanismo automatizado para efetuar a limpeza de superfícies refletoras de heliostatos. O desenvolvimento deste dispositivo, desde sua concepção, passando pelas fases de construção, instalação e funcionamento, respeita padrões de eficiência da limpeza, visa o baixo custo de produção, facilidade de instalação e minimização dos impactos ambientais pertinentes, como, por exemplo, baixo consumo de água na operação. Por meio de experimentos realizados em situações reais de aplicação, utilizando para tal um heliostato de 8 m2 localizado no Departamento de Engenharia Rural da Faculdade de Ciências Agronômicas da UNESP, campus de Botucatu, constatou-se que o dispositivo proposto é uma opção operacionalmente e economicamente viável de solução ao soiling quando aplicado na região de Botucatu, principalmente se comparado a outras propostas de métodos de limpeza de heliostatos apresentadas nos cenários internacional e nacional. Além disso, por meio de estudos sobre os impactos ambientais de usinas heliotérmicas, foi possível sugerir melhorias no processo de licenciamento ambiental de usinas CSP no Brasil.
The possibility of reduction in the supply of conventional fuels, the continuous growing demand for energy and the current concern with the environmental scenario influence the development of researches regarding alternative, renewable and less polluting energy sources, which produces less environmental impact. Among these alternatives, it is worth mentioning the solar energy, available source and that can be explored from all its potentialities. Nowadays, one of many the technological process that uses solar energy for electricity generation is the solar thermal one, also known as Concentrated Solar Power (CSP), based on the use of mirrored surfaces that reflect and concentrate the direct sunlight in order to convert it into thermal energy, from which it generates water vapor that will initiate a reversible thermodynamic cycle which converts heat into energy (Rankine cicle). The phenomenon known as soiling consists in the depositing of different types of dirt on a surface exposed in a given environment. In the case of power tower CSP plants, the gradual accumulation of dust, dirt or even bird's excrements on the reflective surfaces of heliostats causes a significant reduction in the amount of solar radiation that reaches the receiver located at the top of the tower and decreases the efficiency of the entire system. Thus, it is necessary to maintain a high reflectivity factor in the mirrored surfaces of the heliostats through a regular cleaning. This work presents a proposal of an automated mechanism to clean up the reflective surfaces of heliostats. The development of this device, from its conception, through the stages of construction, installation and operation, regarding the cleaning efficiency standards, aimed at low production cost, ease of installation and minimizing the relevant environmental impacts, such as, low consumption of water during its operation. Through experiments in real situations, using a 8 m2 heliostat located in the Department of Rural Engineering of UNESP's Faculty of Agronomic Sciences, Botucatu campus, it was verified that the proposed device is an operationally and economically option for the solution to soiling when applied at Botucatu's region, especially if compared to other proposed methods of heliostats cleaning presented in the international and national scenarios. In addition, through studies on the environmental impacts of heliothermic plants, it was possible to suggest improvements in the environmental licensing process of CSP plants in Brazil.

Highly repellent surfaces are constantly being sought in a number of industrial sectors, where accumulation of unwanted material (ice, debris, insects etc…) can cause seriously detrimental effects on these function. The chemistry and physics of such surfaces is relatively well-understood, yet their industrial adoption is still very limited, due to their poor durability. Emerging technologies for nanostructured coatings have significant potential for the development of advanced surfaces, where high repellency can be combined with mechanical robustness. However, lack of understanding of the wear mechanism in such coatings and lack of recognised test methodologies to enable comparison of various approaches hinders effective progress in advanced surfaces development. Furthermore, there is no comprehensive classification system that allows categorization of highly repellent surfaces. New multi-variable analysis methodology for the evaluation of durability in highly repellent coatings was developed in this study. Key coating parameters were identified, including initial wettability, abrasive wear, adhesive wear and ability to retain repellency. Coating characteristics were examined with FTIR, SEM, AFM, DSA, Taber Abrader, roughness profilometer and goniometer. Furthermore, these characteristics were presented in a form of spider diagrams and performance indices and are used to generate plot of performance indices. In this study, six types of TWI coating anti-soiling materials (based on patented TWI’s Vitolane® technology, containing silsesqioxanes and functionalized silica nanoparticles) and two commercial easy clean products were prepared and subjected to new assessment methodology. It has been found that this novel methodology for evaluation of highly repellent surfaces allows comparison and categorizing different families of coatings. The data obtained from plot of performance indices supports the statement that there is an inverse relation between repellency and durability of hydrophobic surfaces. It has been found that coatings with low Ra value (no more than 10nm) and symmetric distribution of peaks and valleys are the most durable, yet their WCA value doesn’t exceed more than 105°. It has been also found that some nanostructured coatings behave beyond this inverse relationship. Addition of novel inorganic building blocks with controlled size (Ra in a range of 200nm and symmetric distribution in roughness profile) and functionalities (3-(trimethoxysilyl)propyl methacrylate and 1H 1H 2H 2H-perfluorooctyltriethoxysilane) improves overall coating performance by linking mechanical robustness with desired wetting characteristics (WCA reaches 112°C). The progress in testing and classification criteria of repellent coatings enables further development of next generation of materials. This novel knowledge-based approach for highly repellent coatings validation has the potential to accelerate uptake. The findings open a promising new direction in materials development, where advanced coatings and surface treatments can be developed by design, reducing the number of development iterations, ultimately leading to reduced cost and development time.

As buildings age biological and non biological soiling accumulates on their facades. Soiling changes the visual appearance of buildings. This thesis investigates the aesthetic and perceptual changes which take place as a result of the accumulation of soiling. A series of experiments and surveys were conducted to investigate the effects soiling had on aesthetic and perceptual judgements of buildings. A multiple sorting procedure using photographs of buildings, revealed that both an aesthetic evaluation and soiling levels were important ways in which the buildings were conceptualised. A second study comparing photographs of architecturally similar buildings before and after stonecleaning had taken place, revealed large shifts in the evaluation of buildings following cleaning as measured by semantic differentials. Changes in evaluation were found to be dependent on the nature and outcome of the cleaning process. Buildings were also consistently perceived to be younger following cleaning. Surveys amongst residents of cities which had undergone major stonecleaning programmes revealed an awareness of this activity in line with theories of urban perception. Attitudes towards stonecleaning programmes was found to be generally favourable. A survey conducted amongst architects showed the complex range of aesthetic and perceptual effects which soiling and cleaning has on buildings. The surveys conducted amongst both the general public and architects revealed that while cleaned buildings were generally seen to be aesthetically more pleasing than heavily soiled ones, there were some situations where soiling could enhance the aesthetic appearance of buildings. A further study involving ratings of buildings which varied in terms of soiling was therefore conducted which further clarified the role of soiling in aesthetic judgements. Drawing on research in experimental and environmental aesthetics, as well as data from the reported experiments and surveys a model is proposed which relates soiling level to facade complexity and aesthetic evaluation.

The fact that most of the large scale solar PV plants are built in arid and semi-arid areas where land availability and solar radiation is high, it is expected the performance of the PV plants in such locations will be affected significantly due to high cell temperature as well as due to soiling. Therefore, it is essential to study how the different PV module technologies will perform in such geographical locations to ensure a consistent and reliable power delivery over the lifetime of the PV power plants. As soiling is strongly dependent on the climatic conditions of a particular location a test station, consisted of about 24 PV modules and a well-equipped weather station, was built within the fences of Scatec’s 75 MW Kalkbult solar PV plant in South Africa. This study was performed to a better understand the effect of soiling by comparing the relative power generation by the cleaned modules to the un-cleaned modules. Such knowledge can enable more quantitative evaluations of the cleaning strategies that are going to be implemented in bigger solar PV power plants. The data collected and recorded from the test station has been analyzed at IFE, Norway using a MatLab script written for this thesis project. This thesis work has been done at IFE, Norway in collaboration with Stellenbosch University in South Africa and Scatec Solar a Norwegian independent power producer company. Generally for the polycrystalline modules it is found that the average temperature corrected efficiency during the period of the experiment has been 15.00±0.08 % and for the thin film-CdTe with ARC is 11.52% and for the thin film without ARC is about 11.13% with standard uncertainty of ±0.01 %. Besides, by comparing the initial relative average efficiency of the polycrystalline-Si modules when all the modules have been cleaned for the first time and the final relative efficiency; after the last cleaning schedule which is when all the reference modules E, F, G, and H have been cleaned for the last time it is found that poly3 performs 2 % and 3 % better than poly1 and poly16 respectively, poly13 performs 1 % better than poly15 as well as poly5 and poly12 performs 1 % and 2 % better than poly10 respectively. Besides, poly5 and poly12 performs a 9 % and 11 % better than poly7. Furthermore, there is no change in performance between poly6 and poly9 as well as poly4 and poly15. However, the increase in performance of poly3 to poly1, poly13 to poly15 as well as poly5 and poly12 to poly10 is insignificant. In addition, it is found that TF22 perform 7% better than the reference un-cleaned module TF24 and similarly; TF21 performs 7% higher than TF23. Furthermore, modules with ARC glass (TF17, TF18, TF19, and TF20) shows that cleaning the modules with only distilled water (TF19) or dry-cleaned after cleaned with distilled water(TF20) decreases the performance of the modules by 5 % and 4 % comparing to its respective reference uncleanedmodules TF17 and TF18 respectively.

The solar PV modules are influenced by a variety of loss mechanisms by which the energy yield is affected. A PV system is the sum of individual PV modules which should ideally operate similarly, however, inhomogeneous soiling, mismatching, and degradation, which are the main focus in this study, lead to dissimilarities in PV modules operating behavior and thus, lead to losses which will be assessed intensively in terms of energy yield. The dissimilarities in PV modules are referred to the ambient conditions or the PV modules characteristics which result in different modules’ maximum power point (MPP) and thus, different currents generated by each PV modules which cause the mismatching. However, the weakest PV module current governs the string current, and the weakest string voltage governs the voltage. Power optimizers are electronic devices connected to the PV modules which adjust the voltages of the PV modules in order to obtain the same current as the weakest module and thus, extract the modules’ MPP. Hence, the overall performance of the PV plant is enhanced. On the other hand, the power optimizers add additional cost to the plant’s investment cost and thus, the extra energy yield achieved by utilizing the power optimizers must be sufficient to compensate the additional cost of the power optimizers. This is assessed by designing three systems, a reference system with SMA inverters, a system utilizes Tigo power optimizers and SMA inverters, and a system utilizes SolarEdge power optimizers and inverters. The study considers four different locations which are Borlänge, Madrid, Abu Dhabi, and New Delhi. An Excel model is created and validated to emulate the inhomogeneous soiling and to evaluate the economic feasibility of the power optimiz ers. The model’s inputs are obtained from PVsyst and the precipitation data is obtained from Meteoblue and SMHI database. The economic model is based on the relation between Levelized Cost of Electricity (LCOE) which will be used to derive the discount rate. Graphs representing the discounted payback period as a function of the feed-in tariff for different discount rates is created in order to obtain the discounted payback period. The amount of extra energy yielded by the Tigo and the SolarEdge systems is dependent on the soiling accumulated on the PV modules. Relative to the reference system, 6.5 % annual energy gain by the systems utilizing the power optimizers in soiling conditions, up to 2.1 % in the degradation conditions, and up to 9.7 % annual energy gain at 10 % mismatching rate. The extra energy yield is dependent on the location, however, the Tigo and the SolarEdge systems have yielded more energy than the reference system in all cases except one case when the mismatch losses is set to zero. The precipitation pattern is very influential, and a scare precipitation leads to a reduction in the energy yield, in this case, the Tigo and the SolarEdge systems overall performance is enhanced and the extra energy gain becomes greater. The Tigo system yield slightly more energy than the SolarEdge system in most cases, however, during the plant’s lifetime, the SolarEdge system could become more efficient than the Tigo system which is referred to the system’s sizing ratio. The degradation of the system or the soiling accumulation decreases the irradiation and thus, a slightly oversized PV array become suitable and deliver an optimal power to the inverters. The SolarEdge system is feasible in all scenarios in terms of LCOE and discounted payback period, although its slightly lower performance relative to the Tigo system, this is referred to its low initial cost in comparison to the other systems. The Tigo system is mostly infeasible although it yields more energy than the reference and the SolarEdge systems, this is referred iii to its relatively high initial cost. However, feed- in tariffs higher than 20 € cent / kWh make all systems payback within less than 10 years. The results have overall uncertainty within ± 6.5 % including PVsyst, Excel model, and the precipitation uncertainties. The uncertainty in the degradation and the mismatching calculations is limited to PVsyst uncertainty which is ± 5 %. The uncertainties in LCOE in the location of New Delhi, since it is the worst-case scenario, are 5.1 % and 4 % for the reference and the systems utilizing power optimizers, respectively. Consequently, accommodating the uncertainties to the benefits gained by utilizing power optimizers indicates that the energy gain would oscillate in the range of 6 % - 6.9 % for the soiling calculations, 2 % - 2.2 % for the degradation simulations, and 9.2 % - 10.2 % for the mismatching simulations at 10 % mismatchrate.

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The dependence on nonrenewable sources and concern about high levels of pollutant emissions encourage the use of systems that are derived from renewable resources. In this way, photovoltaic systems are seen as promising because they depend on a clean and abundant source, especially in areas of tropical climate, the solar radiation. However, the accumulation of soiling on the surfaces of photovoltaic modules is one of the main environmental factors that cause of the loss of efficiency of these systems, together with irradiance, temperature and shading. In this sense, the present work seeks to verify the soiling effects on the efficiency of photovoltaic modules, through data collection, measurement of specific parameters, statistical analysis and comparisons of scenarios of dirty and clean modules. For the verification and quantification of soiling interference in the efficiency of photovoltaic modules, the electrical and environmental parameters capable of characterizing them are obtained: Isc - Short circuit current (A); Voc - Open circuit voltage (V); G - Solar irradiance (W/m²); T - Module temperature (°C). From the results it can be observed that the intensity of the solar radiation has greater influence on the current of the module, while the temperature directly affects the voltage. This work showed that, in the universe studied, soiling has reduced the power generation efficiency of modules by 3,2% for accumulated soiling in periods of 45 days, and by 18% for accumulated soiling in a longer period of 3,5 years. The characterization of the soiling showed that in addition to mineral particles, there is also organic matter derived from biofilms, which makes it difficult to clean the modules by natural methods (rains and winds). Based on the bibliography and the tests realized, it is estimated that the periodicity of the hygiene should not exceed 60 days, with that, the effects of the soiling are reduced significantly.
A dependência por fontes não renováveis e a preocupação com os elevados níveis de emissões de poluentes estimulam o uso de sistemas que são provenientes de recursos renováveis. Com isso, são vistos como promissores os sistemas fotovoltaicos, por dependerem de uma fonte limpa e abundante, em especial em áreas de clima tropical, a radiação solar. Porém, o acúmulo de sujeira nas superfícies de módulos fotovoltaicos é um dos principais fatores ambientais que causam perda de eficiência desses sistemas, juntamente com irradiância, temperatura e sombreamento. Neste sentido, o presente trabalho busca verificar os efeitos da sujidade na eficiência dos módulos fotovoltaicos, por meio de coletas de dados, medições de parâmetros específicos, análise estatística e comparações de cenários de módulos sujos e limpos. Para a comprovação e quantificação da interferência da sujidade na eficiência de módulos fotovoltaicos são obtidos os parâmetros elétricos e ambientais capazes de caracterizá-los, são eles: Isc - Corrente de curto-circuito (A); Voc - Tensão de circuito aberto (V); G - Irradiância solar (W/m²); T - Temperatura do módulo (°C). A partir dos resultados pode-se observar que a intensidade da radiação solar tem maior influência sobre a corrente do módulo, enquanto que a temperatura afeta diretamente a tensão. Este trabalho comprovou que, no universo estudado, a sujidade diminuiu a eficiência dos módulos em até 3,2% para sujeira acumulada em períodos de 45 dias, e em até 18% para sujidades acumuladas por um período mais longo, de 3,5 anos. A caracterização da sujidade demonstrou que além de partículas minerais, há também matéria orgânica derivada de biofilmes, que dificulta a limpeza dos módulos pelos métodos naturais (chuvas e ventos). Com base na bibliografia e nos ensaios realizados, estima-se que a periodicidade de higienização não deva exceder 60 dias, assim os efeitos da sujidade são reduzidos significativamente.

Dissertação de Mestrado Integrado em Medicina Veterinária
Embora seja um dos mais pequenos e recentes grupos de especialidade, o comportamento animal constitui uma área de extrema importância na medicina veterinária, permitindo identificar e afastar problemas médicos subjacentes a um quadro de alterações comportamentais, assim como divulgar conselhos baseados na ciência e na investigação, auxiliando os proprietários a compreender e a modificar os problemas comportamentais observados nos seus animais de companhia. De acordo com a bibliografia consultada, os sinais mais frequentemente observados pelos proprietários são a eliminação inapropriada, a agressividade, a ansiedade e os problemas dermatológicos, estando disponível uma grande variedade de possibilidades de tratamento, nomeadamente no que diz respeito à modificação comportamental e ao maneio ambiental. O presente estudo teve como objectivo compreender quais as alterações comportamentais mais frequentemente identificadas pelos proprietários em Portugal, e a sua relação com as características dos animais, dos proprietários e do ambiente em que se inserem. Tentou-se ainda conhecer a forma como se recorre aos diferentes meios de tratamento possíveis, e as condições em que se opta pela eutanásia num caso de agressividade. Para tal foi distribuído um questionário, tendo sido recebidas respostas relativas a 197 animais, 120 cães e 77 gatos, oriundos, essencialmente, da região da grande Lisboa. Os medos, particularmente nos gatos, constituem o problema comportamental que mais se destaca, seguido da agressividade para com animais desconhecidos, situação que se revelou mais comum em cães. A ansiedade e a agitação constituem a terceira alteração comportamental mais referida pelos proprietários, sendo caracterizada por originar a exibição de outros comportamentos indesejados, como o comportamento destrutivo, a auto-mutilação, a vocalização excessiva e a eliminação inapropriada, observando-se ainda, especialmente nos gatos, o picacismo. Apenas um pequeno número dos animais que revelaram algum problema comportamental recebeu tratamento. Nos cães, o procedimento mais utilizado é a modificação comportamental, essencialmente através de aulas de obediência e treino, embora também se recorra ao tratamento farmacológico quase com a mesma frequência. Nos gatos, após o recurso aos fármacos, o maneio ambiental surge como o procedimento mais utilizado e associado a outras formas de tratamento, apesar de se verificar que as técnicas descritas pelos proprietários são muito limitadas quando comparadas com a diversidade de possibilidades existentes. Os proprietários da maioria dos animais incluídos neste estudo, afirma que não recorreria à eutanásia em nenhum caso de agressividade ou que, pelo menos, tentaria alguma forma de tratamento.
ABSTRACT - BEHAVIOUR PROBLEMS IN SMALL ANIMALS - Although being one of the smallest and most recently formed fields of speciality, animal behaviour is an extremely important area in veterinary medicine. It not only allows the identification and treatment of underlying medical problems but it also provides advice and science based information to the owners in order to help them understand and manage their pets behaviour problems. According to the researched bibliography, the most common signs of behaviour problems are house-soiling, aggression, anxiety and dermatologic disorders, and there is a wide range of treatments available, especially regarding behaviour modification and environmental enrichment. The purpose of this study is to acknowledge which are the most common behaviour problems indentified by animal owners in Portugal, and understand their connection with the animal’s features, as well as with its owner’s and the surrounding environment’s characteristics. This investigation is also focused on learning how the owners resort to the available treatment possibilities and in which conditions they would choose euthanasia in an aggression case. In order to achieve that purpose, a questionnaire was distributed, having been received 197 replies, 120 concerning dogs and 77 concerning cats, the majority being from the Lisbon area. Fears, especially in cats, are the most frequently observed signs of behaviour problems, followed by aggression towards unfamiliar animals, which is mainly observed in dogs. Anxiety was the third most reported sign, being known to cause other behaviour problems such as destructive behaviour, self-directed behaviour, excessive vocalization, house-soiling, and also pica, especially in cats. Only a small number of the animals that showed some kind of behaviour problems actually received treatment. Within the group of dogs, behaviour modification was the most common form of therapy, usually applied through obedience classes, followed closely by pharmacological therapy. In cats, after drug therapy, the environmental enrichment is the form of treatment that is most commonly used and combined with other therapies, although it became clear that the options used by the owners in this study were very limited comparatively to the wide range of techniques available. It was also possible to conclude that the owners of the majority of the animals in this study would not opt for euthanasia to solve cases of aggression but would seek some form of treatment instead.

Il presente lavoro di tesi è volto allo studio dei prodotti di degrado che si sviluppano su materiali lapidei di natura carbonatica a causa di diversi fattori ambientali. Il lavoro è stato sviluppato su due distinti filoni di ricerca: a) un primo filone incentrato sulla caratterizzazione mineralogico-petrografica e geochimica di croste nere prelevate dalle superfici di monumenti; b) un secondo filone riguardante, invece, lo studio sperimentale di alcuni provini di marmo e calcareniti esposti in ambiente outdoor. La prima linea di ricerca ha riguardato la caratterizzazione di 23 campioni di crosta nera prelevati da 8 rilevanti monumenti Europei, mediante l utilizzo di un approccio multianalitico utile a valutare l interazione tra il substrato e l ambiente. Tale approccio ha riguardato lo studio dei caratteri composizionali e microtessiturali delle croste e lo stato di conservazione dei substrati lapidei, nonché l interazione di questi ultimi con le soprastanti croste. In generale, i risultati acquisiti da questo primo filone di ricerca hanno dimostrato come la variabilità osservata dai dati ottenuti su ciascun campione di crosta possa essere giustificata dal processo stesso che porta alla formazione delle croste nere, un fenomeno complesso e dinamico che è certamente influenzato nel tempo dalle diverse fonti d inquinamento (fisse o mobili) oltre che da numerosi fattori quali: altezza di campionamento, tipologia di substrato, morfologia delle superfici di deposito del particolato, esposizione agli agenti atmosferici, alle fonti di inquinamento, al wash-out e alla deposizione di aerosol atmosferico. Inoltre, la possibilità di poter analizzare la composizione geochimica, in termini di elementi in tracce, delle croste nere e dei substrati alterati, può fornire risposte utili per comprendere l influenza degli inquinanti nella genesi di queste forme di degrado. La seconda linea di ricerca ha riguardato uno studio sperimentale finalizzato al monitoraggio del processo di degrado cui sono sottoposti nel tempo i materiali lapidei di natura carbonatica posti in opera. La sperimentazione condotta ha previsto l esposizione di provini di marmo di Carrara, pietra di Noto e pietra di Comiso (sia tal quali che trattati con un materiale nano-strutturato) in due diversi ambienti outdoor, ubicati in due importanti città siciliane, Catania e Palermo. Il tempo di permanenza dei provini in ambiente outdoor e di relativo monitoraggio è stato di due anni. Sia nella fase pre-espositiva che in quella post-espositiva, la caratterizzazione è avvenuta mediante l utilizzo di diverse metodologie analitiche, al fine di ottenere informazioni circa le eventuali modificazioni fisiche, chimiche e mineralogiche subite dai provini dopo esposizione prolungata. I dati ottenuti hanno permesso di identificare le principali cause di annerimento e soiling di materiali a composizione carbonatica nei due centri di Catania e Palermo. Inoltre, le prove condotte sui provini trattati con biossido di titanio hanno evidenziato che l applicazione dei formulati deve essere testata prima del suo utilizzo sulle superfici dei monumenti d interesse storico-artistico, allo scopo di evitare interventi di restauro errati e/o privi di efficacia. Il lavoro sviluppato in questi due anni di monitoraggio contribuisce indubbiamente alla messa a punto di una metodologia finalizzata alla valutazione della durabilità di diversi litotipi nei confronti dell inquinamento (sorgenti di combustione mobili e fisse) e dell efficacia del prodotto autopulente preso in considerazione.

This thesis is focusing on general issues of floor concrete slabs, technology, implementation, subsoil models, calculation of internal forces and design approaches. Based on these data the thesis monitors the behaviour of floor slabs according to the various parameters. It also includes three versions of design of the real floor slab, made of steel fibre reinforced concrete, reinforced concrete and prestressed concrete. Economic comparison is also included. In addition it developes a design of the chalice base and reinforced concrete column of the supporting hall system, instead of the original usual base with steel column.

The Master’s thesis is focused on the analysis and design of selected members of load-bearing structure of an administration building according to the ultimate limit states (ULS) and seviceability limit states (SLS). The calculation and the analysis was supported by design software SCIA ENGINEER 2012. Structural analysis deals with the design of the reinforced concrete (RC) flat slab above the 4rd strorey which is particularly supported by RC columns and particularly lies on RC walls. Furthermore, the Master’s thesis contains analysis of some selected columns of last three storeys, column of lowest storey, construction of stairway between 4rd and 5th storeys. The work beside this deals with the calculation and design of foundation of the object. The rest parts of the load-bearing structure are not solved in the Master’s thesis.

Mestrado de dupla diplomação com a UTFPR - Universidade Tecnológica Federal do Paraná
This work has as general objective the creation of a soiling index modeling for photovoltaic systems. The specific objectives are: To characterize the functioning of photovoltaic cells, to simulate the photovoltaic system utilizing the PVSyst software to analyze the production capacity of the system, to identify how these variables affect the production of solar energy and to characterize the conditions of energy production based on simulations. To accomplish these objectives, it is necessary to perform a systematic literature review aiming at the soiling impact and the tilted angle in photovoltaic systems. To perform the modeling, a mathematical formula was adapted to calculate the output current of photovoltaic systems. The differences of this approach regarding the other on the extant literature are the facilities to implement this technology using a reduced number of sensors and demanding less processing power. To validate the proposed soiling index model and achieve the objectives, it was performed a simulation of the photovoltaic system, where the theoretical production values of the photovoltaic system were acquired which were used as a database to analyze the results obtained by modeling the soiling index. From these steps, it was possible to realize the relative error for the modeling varies from 0.33% to 2.48%, with a consistent behavior for most of the scenarios. It is possible to conclude that the behavior presented by the modeling is similar to the simulated. The modeling can contribute to photovoltaic systems as a tool to create better and cleaning schedules.
Este trabalho tem como objetivo geral a criação de uma modelagem de índice de sujidade para sistemas fotovoltaicos. Os objetivos específicos são: Caracterizar o funcionamento das células fotovoltaicas, simular o sistema fotovoltaico utilizando o software PVSyst para analisar sua capacidade de produção, identificar como essas variáveis afetam a produção de energia solar e caracterizar as condições de produção de energia com base em simulações. Para atingir esses objetivos, é necessário realizar uma revisão sistemática da literatura, visando estimar o impacto da sujidade e o ângulo de inclinação nos sistemas fotovoltaicos. Para realizar a modelagem, uma fórmula matemática foi adaptada para estimar a corrente de saída dos sistemas fotovoltaicos. A diferença desta abordagem em relação a outras na atual literatura, caracteriza-se pela redução do número de sensores ao se implementar essa tecnologia, o que exige menor poder de processamento. Para validar o modelo de índice de sujidade proposto, foi realizada uma simulação do sistema fotovoltaico. Para isto, foram adquiridos os valores teóricos de produção fotovoltaica, a fim realizar uma análise comparativa aos resultados obtidos através da modelagem do índice de sujidade. A partir disto, foi possível perceber que o erro relativo para a modelagem varia de 0,33% a 2,48%, com um comportamento consistente na maioria dos cenários. É possível concluir que o comportamento apresentado pela modelagem é semelhante ao simulado. Podendo contribuir para os sistemas fotovoltaicos como uma ferramenta, auxiliando na otimização das escalas de limpeza.

abstract: Photovoltaic (PV) systems are one of the next generation's renewable energy sources for our world energy demand. PV modules are highly reliable. However, in polluted environments, over time, they will collect grime and dust. There are also limited field data studies about soiling losses on PV modules. The study showed how important it is to investigate the effect of tilt angle on soiling. The study includes two sets of mini-modules. Each set has 9 PV modules tilted at 0, 5, 10, 15, 20, 23, 30, 33 and 40°. The first set called "Cleaned" was cleaned every other day. The second set called "Soiled" was never cleaned after the first day. The short circuit current, a measure of irradiance, and module temperature was monitored and recorded every two minutes over three months (January-March 2011). The data were analyzed to investigate the effect of tilt angle on daily and monthly soiling, and hence transmitted solar insolation and energy production by PV modules. The study shows that during the period of January through March 2011 there was an average loss due to soiling of approximately 2.02% for 0° tilt angle. Modules at tilt anlges 23° and 33° also have some insolation losses but do not come close to the module at 0° tilt angle. Tilt anlge 23° has approximately 1.05% monthly insolation loss, and 33° tilt angle has an insolation loss of approximately 0.96%. The soiling effect is present at any tilt angle, but the magnitude is evident: the flatter the solar module is placed the more energy it will lose.
Dissertation/Thesis
M.S.Tech Engineering 2011

abstract: This is a two-part thesis. Part 1 presents the seasonal and tilt angle dependence of soiling loss factor of photovoltaic (PV) modules over two years for Mesa, Arizona (a desert climatic condition). Part 2 presents the development of an indoor artificial soil deposition chamber replicating natural dew cycle. Several environmental factors affect the performance of PV systems including soiling. Soiling on PV modules results in a decrease of sunlight reaching the solar cell, thereby reducing the current and power output. Dust particles, air pollution particles, pollen, bird droppings and other industrial airborne particles are some natural sources that cause soiling. The dust particles vary from one location to the other in terms of particle size, color, and chemical composition. The thickness and properties of the soil layer determine the optical path of light through the soil/glass interface. Soil accumulation on the glass surface is also influenced by environmental factors such as dew, wind speeds and rainfall. Studies have shown that soil deposition is closely related to tilt angle and exposure period before a rain event. The first part of this thesis analyzes the reduction in irradiance transmitted to a solar cell through the air/soil/glass in comparison to a clean cell (air/glass interface). A time series representation is used to compare seasonal soiling loss factors for two consecutive years (2014-2016). The effect of tilt angle and rain events on these losses are extensively analyzed. Since soiling is a significant field issue, there is a growing need to address the problem, and several companies have come up with solutions such as anti-soiling coatings, automated cleaning systems etc. To test and validate the effectiveness of these anti-soiling coating technologies, various research institutes around the world are working on the design and development of artificial indoor soiling chambers to replicate the natural process in the field. The second part of this thesis work deals with the design and development of an indoor artificial soiling chamber that replicates natural soil deposition process in the field.
Dissertation/Thesis
Masters Thesis Engineering 2017

碩士
國立中興大學
化學工程學系所
102
In recent years, the photovoltaic conferences pay attention to two topics. First, they are developed for the high efficiency solar cells. Second, the performance and reliability of photovoltaic module are in the outdoor operation. The high efficiency photovoltaic module could be got more energy for the investors at the same area. The excellent performance of photovoltaic module could not affect the energy by the environment in outdoor operation. The area of the back-contact photovoltaic module is 1559mm length × 1046mm width, and the output power is 320W. The temperature coefficient of the back-contact PV module is 0.35W/℃ lower than P-mono and P-multi crystalline photovoltaic module. The back-contact photovoltaic module could be got more energy for the investors in the high temperature environment. The real outdoor performance of the photovoltaic systems is significantly affected by the accumulation of soiling on the surface of photovoltaic modules. The surface of photovoltaic modules is cleaned periodically with water in enormous photovoltaic plants. It is an important topic “How to define the cleaning cycles?” The dust detection system has been developed to monitor real time daily soiling impact on photovoltaic module performance in the field. In this study, we evaluate the cleaning cycles from the dust detection system, and install the system in Jordan, in Taichung, in Thailand respectively. In the dry season, the energy loss of photovoltaic module is 28% during four months in Jordan. It rains frequently in Taichung, and the photovoltaic system was installed in the rooftop. The energy loss of photovoltaic module is only 4%. The climates in Thailand are the same as in Taichung, but the energy loss of photovoltaic module is 15% due to the location of the installation is near the underway infrastructure construction.

碩士
國立成功大學
航空太空工程學系
106
The energy output delivered by photovoltaic module or solar thermal collector is highly dependent on how much the irradiance can reach the panel. The efficiency of the system relies on its design. However, most studies have calculated power output based on the ideal situation, that is, clean surface of the panel. One critical factor is that the output of solar system will decline as suspended dust is deposited on the cover of the solar panel. In order to investigate the effects of dust soiling, a set of glass samples was placed at the Gurien campus of National Cheng Kung University. Three factors were considered: surface modification, size, and tilt angle. Knowing how these factors influence dust deposition helps determine a better design for a specific location. It was found that the average transmittance reduction for the tilted glass samples is 3.38% and is 7.29% in the dry season (October to April) and in rainy season (May to September), respectively. Among the four coatings under consideration, the anti-reflection coating performed the best due to having the highest initial transmittance while the TiO2 coating performed the worst. Tilt angle was found to have a significant influence on dust soiling, where a larger tilt angle resulted in less dust being deposited. As for the sample size, size and dust deposition have an obvious positive relation, where in this study, the side length of the square glass ranged between 50 mm to 300 mm. Based on the observations of precipitation and dust deposition, if there is no rain for a whole month, it is recommended that the surface of the solar panel be cleaned to recover the transmittance to high value.

碩士
國立中央大學
資訊工程學系碩士在職專班
100
Information is useless if it is not trimmed, sorted, or organized in nowadays the network era. Converting tacit information with potential value to explicit knowledge is not only a process of data management, but also the spirits of data mining technologies. Owing to requiring direct normal irradiance (DNI), the concentration photovoltaic (CPV) system comprises hundreds of solar trackers to carry modules to trace the sun. General speaking, possible reasons for the output power of the CPV system going down are deteriorating or failed components, adjustment problems, or under influences of environmental factors, such as: dirt, pollen, or soiling. However, maintenance methods and strategies are varied among those reasons, i.e., system will be recovered by repairing the deteriorated, failed, or making an adjustment, but to resume the output power from soiling depends on the sites, seasons, and rains. In this study, via regression technology, authors exploited the influences on CPV system by soiling or dirt; also, through R-square, to understand the trend after raining or module cleaning. In the meantime, comprehending influences on modules are varied in terms of environmental factors on different locations. In the end, a cleaning decision making strategy is promoted to save manpower, deduct resource waste, achieve cost reduction purpose, enhance system availability, and secure the best overall benefits of CPV systems.

Solar energy installations located in dry, arid regions chosen for their availability of sunlight often face the problem of dust accumulation, or "soiling", on their solar collector surfaces, requiring this dust to be cleaned regularly in order to maintain optimal power production. The electrodynamic screen (EDS) is a technology that can clean this dust off the surfaces of photovoltaic panels and concentrating solar power mirrors using no water and a minimum of power. The EDS is a series of conductive electrodes embedded between two thin dielectric layers, where voltages applied across the electrodes create a patterned electric field which directs the motion of charged dust particles off the EDS surface. As the dust in different desert regions across the world have different physical characteristics, a different set of design parameters is required for the optimal EDS for each region. This optimization work could be easily conducted using a computer model of the physics of an EDS and the dust it clears off its surface. In this thesis, a computer model of the EDS system is created using COMSOL Multiphysics. This model simulates the voltages applied across the electrodes and the resulting electric fields, and then use these to simulate the trajectories of the charged dust particles as they move across the EDS surface. This particle tracing work is validated using experimental data from high-speed camera trials and performance data for different EDS designs. This validation work shows both agreements and disagreements between the predicted and observed dust particle motion, and the beginnings of the investigation into this difference is presented. Finally, the ability to further develop this model for EDS design optimization is discussed.

abstract: This is a two-part thesis: Part 1 characterizes soiling losses using various techniques to understand the effect of soiling on photovoltaic modules. The higher the angle of incidence (AOI), the lower will be the photovoltaic (PV) module performance. Our research group has already reported the AOI investigation for cleaned modules of five different technologies with air/glass interface. However, the modules that are installed in the field would invariably develop a soil layer with varying thickness depending on the site condition, rainfall and tilt angle. The soiled module will have the air/soil/glass interface rather than air/glass interface. This study investigates the AOI variations on soiled modules of five different PV technologies. It is demonstrated that AOI effect is inversely proportional to the soil density. In other words, the power or current loss between clean and soiled modules would be much higher at a higher AOI than at a lower AOI leading to excessive energy production loss of soiled modules on cloudy days, early morning hours and late afternoon hours. Similarly, the spectral influence of soil on the performance of the module was investigated through reflectance and transmittance measurements. It was observed that the reflectance and transmittances losses vary linearly with soil density variation and the 600-700 nm band was identified as an ideal band for soil density measurements. Part 2 of this thesis performs statistical risk analysis for a power plant through FMECA (Failure Mode, Effect, and Criticality Analysis) based on non-destructive field techniques and count data of the failure modes. Risk Priority Number is used for the grading guideline for criticality analysis. The analysis was done on a 19-year-old power plant in cold-dry climate to identify the most dominant failure and degradation modes. In addition, a comparison study was done on the current power plant (framed) along with another 18-year-old (frameless) from the same climate zone to understand the failure modes for cold-dry climatic condition.
Dissertation/Thesis
Masters Thesis Engineering 2015

abstract: This is a two-part thesis. Part 1 presents an approach for working towards the development of a standardized artificial soiling method for laminated photovoltaic (PV) cells or mini-modules. Construction of an artificial chamber to maintain controlled environmental conditions and components/chemicals used in artificial soil formulation is briefly explained. Both poly-Si mini-modules and a single cell mono-Si coupons were soiled and characterization tests such as I-V, reflectance and quantum efficiency (QE) were carried out on both soiled, and cleaned coupons. From the results obtained, poly-Si mini-modules proved to be a good measure of soil uniformity, as any non-uniformity present would not result in a smooth curve during I-V measurements. The challenges faced while executing reflectance and QE characterization tests on poly-Si due to smaller size cells was eliminated on the mono-Si coupons with large cells to obtain highly repeatable measurements. This study indicates that the reflectance measurements between 600-700 nm wavelengths can be used as a direct measure of soil density on the modules. Part 2 determines the most dominant failure modes of field aged PV modules using experimental data obtained in the field and statistical analysis, FMECA (Failure Mode, Effect, and Criticality Analysis). The failure and degradation modes of about 744 poly-Si glass/polymer frameless modules fielded for 18 years under the cold-dry climate of New York was evaluated. Defect chart, degradation rates (both string and module levels) and safety map were generated using the field measured data. A statistical reliability tool, FMECA that uses Risk Priority Number (RPN) is used to determine the dominant failure or degradation modes in the strings and modules by means of ranking and prioritizing the modes. This study on PV power plants considers all the failure and degradation modes from both safety and performance perspectives. The indoor and outdoor soiling studies were jointly performed by two Masters Students, Sravanthi Boppana and Vidyashree Rajasekar. This thesis presents the indoor soiling study, whereas the other thesis presents the outdoor soiling study. Similarly, the statistical risk analyses of two power plants (model J and model JVA) were jointly performed by these two Masters students. Both power plants are located at the same cold-dry climate, but one power plant carries framed modules and the other carries frameless modules. This thesis presents the results obtained on the frameless modules.
Dissertation/Thesis
Masters Thesis Engineering 2015

abstract: The deposition of airborne dust, especially in desert conditions, is very problematic as it leads to significant loss of power of photovoltaic (PV) modules on a daily basis during the dry period. As such, PV testing laboratories around the world have been trying to set up soil deposition stations to artificially deposit soil layers and to simulate outdoor soiling conditions in an accelerated manner. This thesis is a part of a twin thesis. The first thesis, authored by Shanmukha Mantha, is associated with the designing of an artificial soiling station. The second thesis (this thesis), authored by Darshan Choudhary, is associated with the characterization of the deposited soil layers. The soil layers deposited on glass coupons and one-cell laminates are characterized and presented in this thesis. This thesis focuses on the characterizations of the soil layers obtained in several soiling cycles using various techniques including current-voltage (I-V), quantum efficiency (QE), compositional analysis and optical profilometry. The I-V characterization was carried out to determine the impact of soil layer on current and other performance parameters of PV devices. The QE characterization was carried out to determine the impact of wavelength dependent influence of soil type and thickness on the QE curves. The soil type was determined using the compositional analysis. The compositional data of the soil is critical to determine the adhesion properties of the soil layers on the surface of PV modules. The optical profilometry was obtained to determine the particle size and distribution. The soil layers deposited using two different deposition techniques were characterized. The two deposition techniques are designated as “dew” technique and “humidity” technique. For the same deposition time, the humidity method was determined to deposit the soil layer at lower rates as compared to the dew method. Two types of deposited soil layers were characterized. The first type layer was deposited using a reference soil called Arizona (AZ) dust. The second type layer was deposited using the soil which was collected from the surface of the modules installed outdoor in Arizona. The density of the layers deposited using the surface collected soil was determined to be lower than AZ dust based layers for the same number of deposition cycles.
Dissertation/Thesis
Masters Thesis Engineering 2016

abstract: To increase the deployment of photovoltaic (PV) systems, a higher level of performance for PV modules should be sought. Soiling, or dust accumulation on the PV modules, is one of the conditions that negatively affect the performance of the PV modules by reducing the light incident onto the surface of the PV module. This thesis presents two studies that focus on investigating the soiling effect on the performance of the PV modules installed in Metro Phoenix area. The first study was conducted to investigate the optimum cleaning frequency for cleaning PV modules installed in Mesa, AZ. By monitoring the soiling loss of PV modules mounted on a mock rooftop at ASU-PRL, a detailed soiling modeling was obtained. Same setup was also used for other soiling-related investigations like studying the effect of soiling density on angle of incidence (AOI) dependence, the climatological relevance (CR) to soiling, and spatial variation of the soiling loss. During the first dry season (May to June), the daily soiling rate was found as -0.061% for 20o tilted modules. Based on the obtained soiling rate, cleaning PV modules, when the soiling is just due to dust on 20o tilted residential arrays, was found economically not justifiable. The second study focuses on evaluating the soiling loss in different locations of Metro Phoenix area of Arizona. The main goal behind the second study was to validate the daily soiling rate obtained from the mock rooftop setup in the first part of this thesis. By collaborating with local solar panel cleaning companies, soiling data for six residential systems in 5 different cities in and around Phoenix was collected, processed, and analyzed. The range of daily soiling rate in the Phoenix area was found as -0.057% to -0.085% for 13-28o tilted arrays. The soiling rate found in the first part of the thesis (-0.061%) for 20o tilted array, was validated since it falls within the range obtained from the second part of the thesis.
Dissertation/Thesis
Masters Thesis Engineering 2014

碩士
國立臺灣大學
森林學研究所
92
This study applied on the hydraulic conductivity of the unsaturated forest soil in the Lien-Hwa-Chi area, and compared the deviation in hydraulic conductivity among different locations and depths. It’s helpful to understand the effective of water contain, soil pores, rough pores and roots of plants. The study area was located on the eastern slope in Lienhwachi watershed No.5. Measure the forest soil saturated hydraulic conductivity in different gradient, and choose 4 points, 3 depths on ridge, hillslope and valley. The study used the Tension Infiltrometer to measure the hydraulic conductivity and excavated undisturbed soil for physical test. It could tell the effectives of hydraulic conductivity by compared both of the results. These results show that there was no deviation in hydraulic conductivity among different locations but depths. The surface soil is loose and the pores are less in deeper soil, so the hydraulic conductivity becomes smaller within the increasing of depth. The hydraulic conductivity decrease if part of soil pores filled with air, and the gradient become smaller. This situation usually happened in the surface soil. There was no significant difference in deeper soil because the water movement here depended on micro pores.

Tese de mestrado integrado, Engenharia da Energia e do Ambiente, Universidade de Lisboa, Faculdade de Ciências, 2019
A acumulação de partículas na superfície de painéis solares é um fenómeno transversal a todas as tecnologias fotovoltaicas. Este fenómeno é designado por Soiling, e têm como principal consequência a redução da eficiência fotovoltaica dos painéis. Esta tese tem como por objetivo a caracterização e quantificação das perdas causadas pelo efeito do soiling em painéis solares. Para tal, serão estudados cinco módulos instalados nos arredores de Paris com o intuito de obter uma taxa de degradação da potência para cada painel. O impacto do Soiling será estudado através da análise da eficiência dos painéis durante períodos secos, com um foco especial no maior período seco de que existem registos, durante o qual todos os módulos sofreram um decréscimo de eficiência para um intervalo de confiança superior a noventa por cento. Os painéis encontram-se no Observatório SIRTA [1], orientados a Sul a uma inclinação fixa de vinte e sete graus. Situados em terreno aberto, a cerca de vinte centímetros do solo, os painéis estão inseridos numa área rodeada por extensos relvados, caracterizada por uma fraca intensidade rodoviária. Para a realização deste estudo, foi disponibilizada uma ampla gama de dados amostrados em intervalos de dez minutos, permitindo uma precisa análise intra-diária da eficiência fotovoltaica. Dados como a temperatura, potência, corrente e tensão dos painéis, irradiância, temperatura ambiente, pluviosidade, velocidade do vento, humidade relativa, entre muitos outros, possibilitaram não só o estudo do impacto do soiling na performance dos painéis, como também várias outras análises acessórias relevantes. A tese inicia-se por uma abordagem aos principais fatores que afectam a taxa de deposição de partículas nos módulos, assim como os seus variados impactos na eficiência dos painéis. Esta secção visa introduzir o leitor aos conceitos básicos indispensáveis à compreensão da tese, e igualmente fornecer uma contextualização alargada de modo a facilitar a interpretação dos resultados apresentados. Seguem-se depois os métodos e objetivos, o capítulo central desta tese, o qual explica em detalhe todo o processo que culminou na quantificação do impacto do soiling na performance dos painéis estudados. Este capítulo encontra-se dividido em aproximadamente três partes. A primeira, relativa ao processamento inicial dos dados, envolve o cálculo da temperatura dos módulos, a sua eficiência de conversão e subsequente correção térmica. Grande parte desta seção é dedicada estimação das temperaturas dos módulos, as quais serão necessárias para preencher eventuais lacunas devido a falhas dos sensores térmicos. Estas temperaturas serão obtidas através da implementação de dois modelos térmicos capazes de simular a temperatura dos módulos. O primeiro, já existente na literatura, requer apenas a introdução da temperatura ambiente, irradiância, e a temperatura nominal de operação das células solares. Embora este valor seja geralmente fornecido pelo fabricante, este último foi calculado experimentalmente, assegurando que o modelo fosse fornecido com temperaturas nominais de operação de células reais, medidas nas suas verdadeiras condições de operação. O segundo modelo, baseado na modelação /dos fluxos de calor entre o painel e o ambiente, foi criado de raiz com o intuito de aumentar a precisão das estimativas. A estabilidade e desempenho destes modelos será avaliada, comparando a sua precisão e fiabilidade sob diferentes condições. De seguida, a eficiência dos painéis será calculada e corrigida para uma temperatura base de vinte e cinco graus Celcius. Esta correção é indispensável à análise da degradação do desempenho dos painéis, uma vez que remove o efeito da temperatura na eficiência, permitindo o cálculo das taxas de degradação de potência normalizadas. A qualidade desta correção será também estudada de modo a garantir a validade dos resultados. O segundo passo centra-se no reprocessamento dos valores de eficiência por forma a facilitar a deteção de eventuais perdas, permitindo obter uma taxa de degradação da potência fiável. Para tal, a eficiência diária acumulada dos painéis será calculada, com o objetivo de simplificar a análise através da redução das variações intra-diárias, obtendo uma série mais representativa das variações de eficiência. Nesta fase serão também filtrados valores anormais de eficiência, resultantes de erros de medição ou condições de fraca iluminação, detrimentais ao estudo em curso. Será ainda feita uma análise da relação entre a dispersão dos valores diários de eficiência e as condições climatéricas, uma vez que estas podem dificultar a análise dos impactos do soiling, afetando a extração e significância estatística das taxas de degradação de eficiência. O terceiro e último passo consiste na identificação dos períodos secos, ou intervalos durante os quais a chuva não foi suficientemente forte por forma a interferir com a acumulação de partículas nos painéis, e portanto ideais para o cálculo das taxas de degradação da eficiência. Estas serão baseadas no declive da recta resultante de uma regressão linear das eficiências durante estes períodos. O uso de uma regressão linear na previsão de perdas pelo efeito do soiling é baseado em estudos de natureza semelhante, os quais concluíram que o declínio do desempenho fotovoltaico observado durante períodos secos é aproximadamente linear, decrescendo continuamento durante períodos sem chuva e regressando a níveis normais após um episódio de precipitação [2]. Estes factos sugerem que os efeitos do soiling no desempenho de um Sistema PV podem ser estimados adotando um modelo linear de perdas de eficiência entre eventos significativos de precipitação. A quantificação destas perdas foi feita para dois tipos de períodos. Inicialmente, apenas períodos durante os quais a precipitação diária não excedeu os cinco milímetros foram estudados. Isto consistiu no cálculo das taxas de degradação da eficiência para estes intervalos. De seguida, este limiar foi fixado num valor mais conservador, assegurando que nenhum processo de limpeza possa ter acontecido, e as taxas de degradação recalculadas. Uma ênfase especial foi dada ao mais longo período seco de que existem registos, durante o qual todos os painéis registaram uma diminuição inequívoca de eficiência. A taxa de degradação média de potência durante este intervalo foi de -0.042 %/Dia, um valor que se encontra de acordo com vários outros estudos semelhantes [2,3]. Devido à sua incomparável duração, estendendo-se por trinta e sete dias, uma especial atenção foi dada a este intervalo, uma vez que este foi o mais longo período de acumulação ininterrupta de partículas. Por fim, foi feita uma breve análise estatística das regressões lineares, visando validar os resultados. As regressões lineares foram testadas unidireccionalmente, de modo a determinar a probabilidade de um painel registar um decréscimo de eficiência durante este período. Para tal, foram calculados os intervalos de confiança de cada regressão baseados na distribuição t de student, focando-se exclusivamente no intervalo superior, revelando o revelando o nível de confiança com o qual se pode afirmar que perdas devidas ao efeito do soiling estão presentes em cada painel. Os resultados indicaram que todos os painéis sofreram uma queda de eficiência para um intervalo de confiança superior a noventa porcento durante este período mais longo, e de noventa e cinco por cento para quatro dos painéis.
Soiling can be one of the major causes of power loss on photovoltaic systems. Despite this, these remain largely ignored. This study analyzed the soiling-induced efficiency degradation of five different solar modules, aiming to characterize and quantify the impact of soiling on the performance of these systems. This was accomplished through the analysis of the module efficiencies over dry periods, during which rain was insufficient to effectively clean the panels. Results showed that all panels registered an efficiency decrease within a ninety percent confidence interval during the longest dry period, with an average power degradation rate of -0.042 %/Day, suggesting a stable trend of soiling induced efficiency degradation. All other periods exhibited non-significant trends, likely due to the high day-to-day efficiency fluctuations which persisted despite the thermal correction of the efficiency values. The accuracy of two thermal models was tested, aiming to obtain the most reliable module temperature records to be employed in the thermal correction procedure. The first, already existent in the literature and based on the panels’ NOCT yielded the best results, with an average error of 3.55 ºC. The second, based on the precise modelling of the panels’ heat fluxes, proved less practical and reliable, yielding a slightly average error in the order of 3.9 ºC. Finally, the impact of the diffuse radiation on the dispersion of the daily efficiency values was studied, revealing that the latter is proportional to the diffuse ratio. This was achieved through the analysis of the monthly standard deviation for different day types, so as to bypass the effect of seasonal variations. Results suggest that solar panel cleaning can be neglected in the region of Palaiseau, as soiling losses are rendered insignificant due to the combination of moderate panel inclinations and the natural cleaning provided by the high frequency of rainfall events.

Particulate contamination of the optical surfaces of solar collectors, often called "soiling", can have a significant deteriorating impact on energy yield due to the absorption and scattering of incident light. Soiling has more destructive effect on concentrated solar systems than on flat-plate photovoltaic panels, as the former are incapable of converting scattered sunlight. The first part of this thesis deals with the soiling losses of flat-plate photovoltaic (PV), concentrated solar power (CSP), and concentrated photovoltaic (CPV) systems in operation in several regions of the world. Influential parameters in dust accumulation losses, as well as different cleaning mechanisms in pursuit of restoring the efficiency of soiled systems, have been thoroughly investigated. In lieu of the most commonly-practiced manual cleaning method of using high-pressure water jets, the concept of automatic dust removal using the electrostatic forces of electrodynamic screen (EDS) technology is in a developmental stage and on its way toward commercialization. This thesis provides comprehensive analytical solutions for the electric potential and electric field distribution in EDS devices having different configurations. Numerical simulations developed using finite element analysis (FEA) software have corroborated the analytical solutions which can easily be embedded into software programs for particle trajectory simulations while also providing flexibility and generality in the study on the effect of different parameters of the EDS on the electric field and ensuing dust-removal performance. Evaluation and comparison of different repelling and attracting forces exerted on dust particles is of utmost importance to a detailed analysis of EDS performance in dust removal. Hence, the balance of electrostatic and adhesion forces, including van der Waals and capillary forces, have received significant attention in this dissertation. Furthermore, different numerical analyses have been conducted to investigate the potential causes of observed failures of EDS prototypes that functioned well in a laboratory environment but failed after outdoor exposure. Experimental studies form the last two chapters of this dissertation. Different tests have been conducted on an EDS sample integrated with a PV cell to restore the efficiency of the cell after dust deposition. In order to evaluate the performance of the EDS in dust-particle removal, we have studied the particle size distribution on the EDS surface after each dust deposition and EDS cleaning cycle using a custom-built dust-deposition analyzer. Furthermore, we have pursued several experiments to examine how the geometric and operational EDS parameters affect particle charge via charge-to-mass-ratio measurements.

Dissertação de Mestrado em Reabilitação de Edifícios apresentada à Faculdade de Ciências e Tecnologia
No universo dos edifícios antigos, é cada vez mais importante refletir sobre as patologias a que estão sujeitos e a importância de intervenções concordantes e adequadas de tratamento. No caso do fenómeno do enodoamento, as causas e as formas de manifestação diferem de tal forma que urge um conhecimento profundo e detalhado deste tema antes de tomar uma decisão de intervenção.Uma perspetiva consciente e proativa para a prevenção do enodoamento nos edifícios antigos reconhece que estes sofrem naturalmente um processo de envelhecimento, determinado por fatores inevitáveis como as condições atmosféricas e a poluição urbana, e por fatores controláveis, como a escolha dos materiais e o desenho das fachadas. O enodoamento por depósito de sujidade acompanha este processo de envelhecimento e manifesta-se não só nos edifícios envelhecidos, mas também nas construções mais recentes envolventes, pela proximidade e capacidade de disseminação dos agentes contaminantes.Neste contexto, pretende-se no âmbito desta dissertação clarificar os diferentes tipos de enodoamento passíveis de ser encontrados e proceder a uma caracterização arquitetónica e construtiva da Avenida Sá da Bandeira em Coimbra, no sentido de tornar possível o mapeamento e análise do enodoamento por depósito superficial de sujidade e por colonização biológica num conjunto mais restrito de edifícios. Da observação e análise do enodoamento em algumas fachadas desta avenida, foi possível concluir que o enodoamento por depósito de sujidade afeta maioritariamente edifícios virados a norte e nordeste ao fundo do vale, onde há maior emissão de poluentes e as condições de temperatura e humidade são favoráveis à deposição de sujidade. A colonização biológica é mais incidente nos elementos de relevo, porque são os constituintes da fachada mais expostos às condições de menor exposição solar, menor temperatura, maior humidade e fraca ventilação que a existência de elementos arbóreos proporciona.
In the universe of ancient buildings, it is increasingly important to reflect on the pathologies to which they are subject and the importance of concordant and appropriate treatment interventions. In the case of the phenomenon of soiling, the causes and forms of manifestation differ in such a way as to require a detailed knowledge of this theme before making a decision to intervene.A conscious and proactive perspective for soiling prevention in old buildings recognizes that they naturally undergo an aging process, determined by unavoidable factors such as atmospheric conditions and urban pollution, and by controllable factors such as the choice of materials and the design of facades. Dust and pollutants accompanies this aging process and is manifested not only in the aged buildings, but also in the more recent constructions surrounding it, due to the proximity and the capacity of dissemination of the contaminating agents.In this context, it is intended within the scope of this thesis to clarify the different types of soiling that can be found and to proceed with an architectural and constructive characterization of Avenida Sá da Bandeira in Coimbra, in order to make possible the mapping and analysis of dust and pollutants and biological colonization in a more restricted set of buildings.From the observation and analysis of soiling in some façades of this avenue, it was possible to conclude that dust and pollutants mainly affects buildings facing north and northeast to the bottom of the valley, where there is more emission of pollutants and the conditions of temperature and humidity are favorable to the deposition of dirt. Biological colonization is more incident in embossed elements, because these constituents of the façade are more exposed to conditions such as less sun exposure, lower temperature, higher humidity and poor ventilation that the existence of arboreal elements provides.

abstract: Soiling is one of the major environmental factors causing the negative performance of photovoltaic (PV) modules. Dust particles, air pollution particles, pollen, bird droppings and other industrial airborne particles are some natural sources that cause soiling. The thickness of soiling layer has a direct impact on the performance of PV modules. This phenomenon occurs over a period of time with many unpredictable environmental variables indicated above. This situation makes it difficult to calculate or predict the soiling effect on performance. The dust particles vary from one location to the other in terms of particle size, color and chemical composition. These properties influence the extent of performance (current) loss, spectral loss and adhesion of soil particles on the surface of the PV modules. To address this uncontrolled environmental issues, research institutes around the world have started designing indoor artificial soiling stations to deposit soil layers in various controlled environments using reference soil samples and/or soil samples collected from the surface of PV modules installed in the locations of interest. This thesis is part of a twin thesis. The first thesis (this thesis) authored by Shanmukha Mantha is related to the development of soiling stations and the second thesis authored by Darshan Choudhary is associated with the characterization of the soiled samples (glass coupons, one-cell PV coupons and multi-cell PV coupons). This thesis is associated with the development of three types of indoor artificial soiling deposition techniques replicating the outside environmental conditions to achieve required soil density, uniformity and other required properties. The three types of techniques are: gravity deposition method, dew deposition method, and humid deposition method. All the three techniques were applied on glass coupons, single-cell PV laminates containing monocrystalline silicon cells and multi-cell PV laminates containing polycrystalline silicon cells. The density and uniformity for each technique on all targets are determined. In this investigation, both reference soil sample (Arizona road dust, ISO 12103-1) and the soil samples collected from the surface of installed PV modules were used. All the three techniques are compared with each other to determine the best method for uniform deposition at varying thickness levels. The advantages, limitations and improvements made in each technique are discussed.
Dissertation/Thesis
Masters Thesis Mechanical Engineering 2016

abstract: This study evaluates two photovoltaic (PV) power plants based on electrical performance measurements, diode checks, visual inspections and infrared scanning. The purpose of this study is to measure degradation rates of performance parameters (Pmax, Isc, Voc, Vmax, Imax and FF) and to identify the failure modes in a "hot-dry desert" climatic condition along with quantitative determination of safety failure rates and reliability failure rates. The data obtained from this study can be used by module manufacturers in determining the warranty limits of their modules and also by banks, investors, project developers and users in determining appropriate financing or decommissioning models. In addition, the data obtained in this study will be helpful in selecting appropriate accelerated stress tests which would replicate the field failures for the new modules and would predict the lifetime for new PV modules. The study was conducted at two, single axis tracking monocrystalline silicon (c-Si) power plants, Site 3 and Site 4c of Salt River Project (SRP). The Site 3 power plant is located in Glendale, Arizona and the Site 4c power plant is located in Mesa, Arizona both considered a "hot-dry" field condition. The Site 3 power plant has 2,352 modules (named as Model-G) which was rated at 250 kW DC output. The mean and median degradation of these 12 years old modules are 0.95%/year and 0.96%/year, respectively. The major cause of degradation found in Site 3 is due to high series resistance (potentially due to solder-bond thermo-mechanical fatigue) and the failure mode is ribbon-ribbon solder bond failure/breakage. The Site 4c power plant has 1,280 modules (named as Model-H) which provide 243 kW DC output. The mean and median degradation of these 4 years old modules are 0.96%/year and 1%/year, respectively. At Site 4c, practically, none of the module failures are observed. The average soiling loss is 6.9% in Site 3 and 5.5% in Site 4c. The difference in soiling level is attributed to the rural and urban surroundings of these two power plants.
Dissertation/Thesis
M.S.Tech Engineering 2013