This work presents a dynamic model for utility-scale PV systems. The model is based on a centralized converter topology, which uses a voltage-sourced converter (VSC) to facilitate the exchange of energy between PV generators and the utility grid. The related control system regulates active and reactive power injected by the PV system, based on a current control strategy. Moreover, the model includes a Maximum Power Point Tracking (MPPT) scheme, implemented with the incremental conductance method. Dimensioning of the model is presented as well as simulation cases to validate its performance. Subsequently, the model was used to analyze the effect of variations in solar radiation on a test network with high penetration of photovoltaic generation. Results showed that without proper compensation of reactive power, variations in solar radiation can cause voltage fluctuations outside allowable limits. Thus, in order to mitigate these fluctuations, local control strategies were implemented to allow the exchange of reactive power between the solar farm and the utility grid. Simulations showed that the proposed strategies can mitigate voltage fluctuations at the point of common coupling, improving voltage regulation in the network. / Este trabalho apresenta um modelo dinâmico de sistemas fotovoltaicos de grande escala. O modelo é baseado em uma topologia de conversor centralizado, que usa um conversor de fonte de tensão (VSC) para facilitar a troca de energia entre os geradores fotovoltaicos e a rede elétrica. O sistema de controle relacionado regula a energia ativa e reativa injetada pelo sistema fotovoltaico, com base em uma estratégia de controle de corrente. Além disso, o modelo inclui um sistema de rastreamento de ponto de potência máxima (MPPT), implementado com o método da condutância incremental. O dimensionamento do modelo é apresentado, bem como vários casos de simulação para validar o seu desempenho. Posteriormente, o modelo foi utilizado para analisar o efeito das variações na radiação solar sobre uma rede de teste com uma elevada penetração de geração fotovoltaica. Os resultados mostraram que sem uma adequada compensação de energia reativa, as variações na radiação solar podem causar flutuações de tensão fora dos limites permitidos. Assim, a fim de mitigar estas flutuações, estratégias de controle local foram implementadas para permitir a troca de potência reativa entre os sistemas fotovoltaicos e a rede. As simulações mostraram que as estratégias propostas podem mitigar as flutuações de tensão no ponto de acoplamento comum, melhorando a regulação de tensão na rede.

Made available in DSpace on 2016-06-02T20:19:19Z (GMT). No. of bitstreams: 1 DissACBS.pdf: 10545595 bytes, checksum: 079933a164ff065ae11e54e43ae5200a (MD5) Previous issue date: 2004-12-20 / The purpose of this study was to analyze the 660 nm GaAlAs laser effect with 10 mW and 40 mW, during 10 seconds, on angiogenesis process and repair quality after partial lesion of Achilles tendon in rats. It was used 104 male rats, that 96 rats had been submitted to lesion by a falling of 186 g from a height of 20 cm, above the right tendon. These rats had been randomly divided in 3 groups, treated in 3 (n = 32), 5 (n = 32) and 7 (n = 32) days, respectively. Each of these groups was divided again into 4 subgroups, which were submitted to laser with mean output of 10 mW (n = 8) and 40 mW (n = 8), a sham treatment (n = 8), and a group with no treatment (n = 8). The analyzes were made by vessels count that have been previous prepared with nanquim ink and by a semiqualitative analyze of polynuclear cells presence, mononuclear cells presence, collagen organization and neovascularization. A fourth group with 8 animals was established as control, without lesion and used as reference for qualitative analyze. The comparison of the groups made evident that the animals submitted to laser showed more vessels number than the control groups (p<0,05) and the 40 mW subgroup showed better vascularization than the others after 3 days of irradiation. (p<0,01). The semiqualitative analyze showed statistical difference (p<0,05) when considering collagen organization and neovascularization in the comparison between the 10 mW, 40 mW and control. Qualitatively, the groups treated with laser showed better repair aspect. The results permit us to conclude that Low Level Laser Therapy with 660 nm promoted an increase of the blood vessels number and better repair quality and the mean output of 40 mW had begun the neovascularization precocious, showing significant difference after 3 days of application. / A proposta desse estudo foi analisar os efeitos do laser AsGaAl, de 660 nm, com 10 mW e 40 mW de potência de saída, aplicado durante 10 segundos, no processo de angiogênese e qualidade de reparo após lesão parcial do tendão calcâneo de ratos. Foram utilizados 104 ratos machos, sendo que 96 foram submetidos à lesão com a queda de um peso de 186 gramas na altura de 20 cm sobre o tendão direito. Estes foram divididos aleatoriamente em 3 grupos, tratados em 3 (n = 32), 5 (n = 32) e 7 (n = 32) dias, respectivamente. Cada um desses grupos foi ainda dividido em 4 subgrupos, submetidos ao laser com potência de saída de 10 mW (n = 8) e 40 mW (n = 8), grupo placebo (n = 8) e grupo sem tratamento (n = 8). As análises foram feitas através da contagem dos vasos que foram previamente corados com tinta nanquim e por meio de uma análise semiqualitativa da presença de células polimorfonucleares, mononucleares, organização de colágeno e neovascularização. Um quarto grupo com 8 animais foi estabelecido como controle padrão, sem lesão que foi utilizado como referência para a análise qualitativa. A comparação dos grupos evidenciou que os animais irradiados mostraram maior número de vasos do que os grupos controle (p<0,05) e o subgrupo de 40 mW apresentou melhor vascularização que os demais após 3 dias de irradiação (p<0,01). A análise semiqualitativa evidenciou diferença estatística (p<0,05) quando foi considerada a organização de colágeno e a neovascularização na comparação entre os grupos 10 mW e 40 mW com os controle. Qualitativamente os grupos tratados com laser apresentaram melhor aspecto do reparo. Os resultados nos permitem concluir que a terapia laser de baixa intensidade, com comprimento de onda de 660 nm promoveu aumento na neovascularização e melhora na qualidade de reparo e a potência de saída de 40 mW iniciou a neovascularização precocemente, mostrando diferença significativa após 3 dias de aplicação.

L’intégration des énergies intermittentes sur le réseau électrique existant soulèvedes problèmes de stabilité de la balance consommation/production. Afin de limiter les risques,la loi autorise un taux de pénétration maximum de ces énergies de 30% de la puissanceinstallée. Afin de pallier cette limitation, deux pistes sont envisagées, le stockage d’énergie etla prévision de production. Les travaux menés dans cette thèse s’inscrivent dans la secondecatégorie et se concentrent sur la prévision du rayonnement global au sol, ressource principaledes systèmes de production d’énergie photovoltaïque. Dans l’objectif d’une prévision à trèscourt terme (infra-horaire), la problématique développée concerne la fusion d’informationsprovenant d’une part d’observations satellitaires et de l’autre d’observations in-situ telles quedes images hémisphériques. L’approche suivie se veut progressive et s’articule autour de 4grand axes. Le premier chapitre énonce les définitions et les enjeux principaux liés à l’étudedu GHI en décrivant les différents facteurs physiques ayant des interactions sur sa mesure. Lesecond chapitre permet d’évaluer le potentiel des images hémisphériques pour l’estimation durayonnement global. On y développe une méthode d’estimation du GHI basée sur l’utilisationd’un réseau de neurones artificiels permettant d’effectuer une régression non linéaire entre descaractéristiques choisie de l’image et le rayonnement mesuré sur site par un pyranomètre. Letroisième chapitre concerne l’utilisation des images satellitaires pour la prévision à très courtterme du rayonnement global. L’originalité des méthodes proposées provient de l’utilisationen entrées de cartes de rayonnement dérivées des images satellitaires via une méthode externe.L’utilisation de ces cartes de rayonnement permet la construction de modèles linéairessimples (modèles auto-régressifs) grâce à l’homogénéité des données utilisées. Cependant,leur pertinence pour le calcul de champ de vecteurs a également été prouvé et validé dans unsecond modèle. La comparaison des deux modèles ainsi créés à partir d’imagerie satellitairea permis de caractériser les forces et faiblesses de ces modèles. L’intérêt de l’observationsatellitaire réside dans l’anticipation du déplacement des masses nuageuse. Cependant, unbiais non systématique persiste dans la conversion des valeurs des pixels en rayonnement.Ce biais est inhérent à la résolution spatio-temporelle de ces observations. Étant donné cesconsidérations, le chapitre 4 présente alors une méthode d’intégration des données acquisespar l’imagerie hémisphérique, disposant une meilleure résolution spatio-temporelle, dans lesrésultats de prévision satellitaires précédemment évoqués. On joint alors les caractéristiquesretenues au chapitre 2 dans un réseau de neurone avec la prévision pour produire uneprévision dont le biais est largement réduit. L’utilisation de caractéristiques dérivées del’imagerie hémisphérique à la place de simple mesures du pyranomètre est justifiée par l’effetde persistance non souhaité apportées par ces dernières. Ainsi, après avoir étudié chaquesource d’information séparément, on a pu développer un modèle leur permettant de secompléter. / To handle the integration of intermittent energies to the existing grid,managers require more and more acurate tools to forecast the primary resources. This thesisfocuses on the very short term forecast of the global horizontal irradiance (GHI), maininput for most photovoltaic power plant. We chose to use both ground based images fromhemispherical cameras and satellite images to provide a forecating tool. In the first handwe present a novel appraoch to estimate the GHI using ground based images. On secondhand, we propose several satellite based methods to forecast the GHI up to one hour. Finally,we developp a new method allowing us to merge both data in order to benefit from theirrespective advantages. All the methods were tested against real data acquired on the SIRTAsite, Polytechnique campus.

Made available in DSpace on 2014-12-17T14:56:13Z (GMT). No. of bitstreams: 1 MiltonMS_DISSERT.pdf: 1198203 bytes, checksum: 5aa3cbd3210f2bffb7997d8334cf6590 (MD5) Previous issue date: 2013-08-06 / This study aims at the design, development and performance evaluation of a flat platform to capture incident solar radiation. The design and implementation of a fuzzy system for the efficient control of the solar tracking movement of the platform are also presented / Este trabalho objetiva o projeto, o desenvolvimento e a avalia??o de desempenho de uma plataforma plana com dois graus de liberdade para capta??o da radia??o solar. S?o apresentados o projeto e a implementa??o de um sistema fuzzy para o controle eficiente do movimento de rastreamento solar da plataforma

L'intégration de la production des énergies renouvelables intermittentes dans le mix énergétique est aujourd'hui limitée à un seuil de 30 % de la puissance totale produite. Cette mesure vise à assurer la sécurité de l'alimentation électrique des réseaux insulaires en France. La levée de ce verrou technique ne pourra se faire qu'en apportant des solutions au caractère intermittent des sources d'énergies éolienne et photovoltaïque. Les difficultés énergétiques auxquelles sont confrontés aujourd'hui les milieux insulaires préfigurent celles que rencontreront la planète à plus ou moins long terme. Ces territoires sont des laboratoires uniques pour éprouver les nouvelles technologies de stockage, de gestion et de prévision de l'énergie. La contribution de ce travail de thèse se focalise sur la prévision du rayonnement solaire global à différents horizons de temps car la puissance photovoltaïque produite découle directement de l'intensité du rayonnement solaire global. Dans un premier temps, l'étude bibliographique a permis de classer les modèles de prévision numériques et les modèles de prévision statistiques en fonction de la résolution spatiale et temporelle. Par ailleurs, elle montre que les meilleurs performances sont obtenues avec les modèles hybrides. Dans un deuxième temps, un modèle de prévisions à court terme (J+1) est proposé avec le modèle Weather Research and Forecasting (WRF) et un réseau de neurone bayésien. L'hybridation de ces deux méthodes améliore les performances de prévisions à J+1. Dans un troisième temps, un modèle de prévision à très court terme (t+h) est proposé avec le modèle hybride de Kalman. Cette méthode produit d'une part une prévision énergétique et d'autre part une prévision multi-horizon. La comparaison de la performance de ces modèles avec la méthode de référence dite de persistance montre une amélioration de la qualité de la prévision. Enfin, la combinaison du filtre de Kalman avec le modèle numérique WRF permet une mise en œuvre opérationnelle de la prévision. / The integration of intermittent renewable energy in the energy mix is currently limited to a threshold of 30% of the total power being produced. This restriction aims at ensuring the safety of the power input. The elimination of this technical obstacle will be possible with solutions to energy intermittence of wind and solar energy. The energy issues which islands are facing today prefigure global problems in a more or less long term. These territories constitute unique laboratories for testing new technologies of storage, management and forecasting of energy. The contribution of this thesis focuses on the forecasting of global horizontal irradiance at different time horizons. Indeed, the generated PV power stems directly from the intensity of the global horizontal irradiance. First, the review of solar irradiance forecasting methods allows to classify numerical weather models and statistical forecasting methods depending on spatial and temporal resolution. Moreover, it shows that best performance is obtained with hybrid models. Second, a short-term forecast model (day ahead forecast) is developed with the Weather Research and Forecasting model (WRF) and a Bayesian neural network. The hybridization of these methods improves the day ahead forecast performance. Third, a model for forecasting the very short term is developped with the Kalman hybrid model. This method offers on the one hand an energy forecasting and on the other hand a multi-horizon forecast. Comparing the performance of the aforesaid with the reference method, namely the persistence method, shows an improvement of the quality of the forecasts. Combining the Kalman filter with the WRF numerical model allows an operational implementation of the forecast.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / No cultivo de plantas medicinais as condiÃÃes de salinidade e de luz podem exercer influÃncia no rendimento e qualidade final da produÃÃo de fitomassa. Este trabalho foi desenvolvido no NÃcleo de Ensino e Pesquisa em Agricultura Urbana (NEPAU) da Universidade Federal do Cearà â UFC, em Fortaleza â CE, com o objetivo de avaliar o efeito de diferentes nÃveis luminosidades e de salinidade na Ãgua de irrigaÃÃo no crescimento e respostas fisiolÃgicas de trÃs espÃcies medicinais do gÃnero Plectranthus. Utilizou-se o delineamento experimental em parcelas subsubdivididas, com cinco repetiÃÃes, sendo as parcelas referentes ao fator ambiente (pleno sol e telado), as subparcelas referentes aos nÃveis de salinidade na Ãgua de irrigaÃÃo - CEa (0,7; 1,9; 3,1; 4,3 e 5,5 dS m-1), e as subsubparcelas Ãs trÃs espÃcies do gÃnero Plectranthus (P. amboinicus, P. barbatus e P. grandis). O experimento teve a duraÃÃo de 60 dias, apÃs o transplantio, sendo realizadas as seguintes avaliaÃÃes: Ãrea foliar, produÃÃo massa seca da parte aÃrea, massa seca das raÃzes, trocas gasosas, teores de clorofila e acÃmulo de solutos orgÃnicos e inorgÃnicos. O estresse salino induziu reduÃÃes significativas no crescimento e nas trocas gasosas das trÃs espÃcies avaliadas, com as maiores reduÃÃes sendo verificadas nas plantas expostas a pleno sol. A resposta à salinidade da espÃcie P. grandis foi menos influenciada pelo ambiente de cultivo do que nas duas outras espÃcies estudadas. A salinidade afetou a partiÃÃo de matÃria seca, sendo as raÃzes mais afetadas do que a parte aÃrea. Em relaÃÃo a produÃÃo de matÃria seca total, verifica-se que as trÃs espÃcies estudadas se mostraram tolerantes ou moderadamente tolerantes à salinidade de atà 3,1 dS m-1, porÃm na salinidade de 5,5 dS m-1 todas se mostraram sensÃveis ao excesso de sais na Ãgua de irrigaÃÃo. Considerando-se o grau de reduÃÃo na produÃÃo de massa seca da parte aÃrea (parte de interesse comercial), poderia-se recomendar o cultivo da espÃcie P. grandis quando se dispÃe de Ãgua de irrigaÃÃo com CEa de atà 3,1 dS m-1. Verificou-se aumento expressivo na acumulaÃÃo de Na+ e Cl-, e reduÃÃes no teor de potÃssio, tanto nas hastes quanto nas folhas. Em decorrÃncia do maior acÃmulo de sÃdio nas hastes, a relaÃÃo dos Ãons Na+/K+ nesta parte da planta atingiu valor de 1,6 na CEa de 5,5 dS m-1, indicando um possÃvel desequilÃbrio nutricional e toxicidade de Ãons. Para os solutos orgÃnicos, o teor de carboidratos nÃo foi alterado com o aumento da CEa, porÃm os teores de prolina e N-aminossolÃveis aumentaram em resposta ao estresse, sendo que no caso da prolina os aumentos foram maiores na espÃcie P. grandis cultivada em pleno sol. / Growing medicinal plants in the conditions of salinity and light can exert influence on yield and final quality of the biomass production. This work was developed at the Center for Teaching and Research in Urban Agriculture (NEPAU), Federal University of Cearà - UFC, Fortaleza - CE, with the objective of evaluating the effect of different luminosities and salinity levels in irrigation water on growth and physiological responses of three medicinal species of the genus Plectranthus. It was used the completely randomized split plots with five repetitions, the plots had corresponded to the environmental factor (mesh with 50% luminosity and full sunlight) and the split plots for five levels of salt stress in irrigation water â CEw (0.7, 1.9, 3.1, 4.3 and 5.5 dS m-1 ) and the subsubplots the medicinal species (P. amboinicus, P. barbatus and P. grandis). The experiment lasted for 60 days after transplanting, being determined by the following: leaf area, dry mass production of shoot, root dry mass, gas exchange, chlorophyll content and accumulation of organic and inorganic solutes. Salt stress induced significant reductions in the growth and gas exchange of the three species evaluated, with the largest reductions being observed in plants exposed to full sunlight. The response to the salinity of the species P. grandis was less influenced by growth environment than in the other two species. Salinity affected the dry matter partitioning, the roots being more affected than the shoot. Considering the total dry matter production, it is found that all three species studied were moderately tolerant or salinity tolerance of up to 3.1 dS m-1 but on the salinity of 5.5 dS m-1 all were sensitive to excess salts in the irrigation water. Considering the degree of reduction in the production of raw party area (part of commercial interest), one could recommend the cultivation of the species P. grandis when it has irrigation water with ECw up to 3.1 dS m-1 . There was significant increase in the accumulation of Na+ and Cl- , and reductions in potassium content, both on the stems as the leaves. Due to the higher accumulation of sodium in the stems, the ratio of Na+ /K+ in this part of the plant reached a value of 1.5 in CEa of 5.5 dS m-1 , indicating a possible nutritional imbalance and ion toxicity. For the organic solutes, the carbohydrate content was not changed with increasing salinity but the concentrations of proline and N-aminosoluble increased in response to stress and in the case of proline elevations were higher in the species P. grandis grown in full sunlight.

Nous proposons une méthode pour placer automatiquement des sondes dans une scène par minimisation d’une fonction d’erreur. Nous guidons les sondes vers les sites d’échantillonnage optimaux en appliquant la descente de gradient à une fonction d’erreur qui représente la similarité entre la structure en construction et un ensemble de référence. En utilisant la pondération inverse à la distance comme fonction interpolante, nous avons construit avec fiabilité des ensembles de sondes dans trois scènes. En comparant nos résultats avec ceux produits par un ensemble de sondes de référence placées sur une grille régulière, nous atteignons théoriquement notre objectif dans une des trois scènes, où nous obtenons des valeurs d’erreur inférieures à la référence avec beaucoup moins de sondes. Nous avons eu des succès partiels dans les autres scènes, selon le nombre d’échantillons utilisés. / Diffuse global illumination within a 3D scene can be approximated in real time using irradiance probes. Probe placement typically relies on significant human input, and final quality of the approximation is often left to the subjectivity of a lighting artist. As demand for realism in rendering increases, the need to enhance the quality of such approximations is greater. We propose a method to automatically place probes in a scene by minimizing an error function. We guide probes to optimal sampling locations by applying gradient descent to an error function that represents similarity between our interpolated results and reference irradiance values. Using weighted nearest neighbour interpolation, we were able to reliably construct probe sets with minimal input in three scenes. Comparing our results to those produced by a set of probes placed on a 3D grid, we were theoretically successful in one scene, in which we could obtain lower error values with fewer probes. We obtained partial success in the other scenes, depending on the number of samples used.

This master´s thesis is about searching for a connection between solar illumination and solar irradiance. The task is attempt to find out if it is possible to use one factor in order to determine the other one. Part of this thesis deals with cooling of virtual building.

The present Master thesis focuses on evalution of CO2 concentration and irradiance on selected leaf anatomical parameters of European Beech (Common Beech) Fagus sylvatica L.. The process of photosynthesis is remarkably determined by numerous extrenal factors, among them by atmoshperic CO2 concentration and irradiance and is closely correlated with leaf anatomical parameters. One of these most important anatomical parameters affecting the net assimilation rate is an internal leaf surface, which corresponds to mesophyll area avialable for gas exhcange. Experimental material of the study was sampled from the leaves of juvenile trees of F. sylvatica planted in 2005 and growing under ambient (390 ppm, AC) and elevated (700 ppm, EC) CO2 concentrations on the experimental site of the Global Change Research Center AS CR at Bílý Kříž in the Beskydy Mountains. Sun and shade leaves were sampled from trees of both CO2 treatments in two seasons 3 years apart (2009 and 2012). To determine leaf anatomical parameters, the stereological methods were applied, which yield unbiased estimation of measured parameters, particularly the Fakir method for internal leaf surface determination. The EC effect was observed on the leaves sampled in 2009 only in the decrease of proportion of intercellular spaces in mesophyll. In...

Examensarbetet som presenteras i denna rapport är ett delprojekt utfört i samarbete med Glava Energy Center och redovisar framtagningen av ett PV-system för den eldrivna båten Bowter. I rapporten utfördes en energianalys där solinstrålning i olika plan studerades och analyserades. Möjligheter att utöka antalet solceller baserat på båtens design undersöktes, där båtens horisontella badbrygga samt vertikala långsidor bedömdes vara de ytor som var lämpliga för placering. Förslag på konfigurationer av PV-systemet dimensionerades och den förväntade mängden genererad energi och laddning beräknades. Systemet som togs fram skulle enligt beräkningar i genomsnitt generera mellan 1,06–2,22kWh energi per dag och kosta omkring tio tusen kronor. Energianalysen visade att solceller placerade i 30–40° lutning i genomsnitt skulle kunna generera mellan 20–43 procent mer energi och laddning än den valda vertikala placeringen. Med båtens nuvarande design utan några möjligheter för placering av solceller i lutande plan går därmed denna potentiella mängd energi förlorad. Praktiska mätningar av energi via reflektioner från vattenytan visar heller inga övertygande tecken på att rädda upp för denna mängd förlorad energi. Simuleringar av det framtagna systemet genomfördes och jämfördes med det beräknade genomsnittet, vilket visade att man skulle kunna förvänta sig cirka 25 procent mer energi under klara förhållanden och 76 procent mindre energi under svåra väderförhållanden med långvariga och heltäckande moln. Av resultaten drogs slutsatsen att det mest praktiska alternativet för maximal systemeffekt är att möjliggöra placering av fler solceller i horisontellt plan via t.ex. en takdel och på den vägen erhålla ett mer pålitligt och förutsägbart resultat som både skulle vara mer effektivt samt ekonomiskt fördelaktigt i jämförelse med det framtagna systemet. / The thesis work presented in this report is a sub-project carried out in collaboration with Glava Energy Center and reports on the development of a PV system for the electric boat Bowter. In the report, an energy analysis was performed where solar irradiance in different planes was studied and analyzed. Opportunities to increase the number of solar cells based on the boat's design were investigated, where the boat's horizontal swim platform and vertical sides were determined to be the areas that were suitable for placement. Proposals for configurations of the PV system were sized and the expected amount of generated energy and charge capacity were calculated. According to calculations the proposed system would on average generate between 1.06–2.22kWh of energy per day and cost around SEK 10,000. The energy analysis showed that solar cells placed at an angle of 30–40° could on average generate between 20–43 percent more energy and charge than the chosen vertical placement. With the boat's current design without any possibilities for placing solar cells in an inclined plane, this potential amount of energy is lost. Practical measurements of energy via reflections from the water surface show no convincing signs of compensating for this amount of lost energy. Simulations of the proposed system were carried out and compared with the calculated average, which showed that one could count on about 25 percent more energy in clear conditions and 76 percent less energy in harsh weather conditions with long-lasting and overcast clouds. From the results, it was concluded that the most practical alternative for maximum system power is to enable the placement of additional solar cells in a horizontal plane via e.g. a roof section and in that way obtain a more reliable and predictable result that would be both more efficient and economically advantageous in comparison with the proposed system.