Το μεγαλύτερο μέρος της απορροφούμενης ηλιακής ακτινοβολίας από τα φωτοβολταϊκά (φβ) κύτταρα δεν μετατρέπεται σε ηλεκτρισμό αλλά σε θερμότητα, η οποία συντελεί στην αύξηση της θερμοκρασίας τους με συνέπεια την μείωση της ηλεκτρικής τους απόδοσης. Η απαγωγή της θερμότητας από τα φβ πλαίσια βοηθά όχι μόνο στη μείωση της θερμοκρασίας λειτουργίας τους αλλά μπορεί και να αξιοποιηθεί αυξάνοντας τη συνολική ενεργειακή τους απόδοση. Τα ηλιακά συστήματα που έχουν τη δυνατότητα να παρέχουν τόσο ηλεκτρική όσο και θερμική ενέργεια είναι τα υβριδικά φωτοβολταϊκά / θερμικά (φβ/θ ή PV/T) συστήματα, τα οποία αναπτύσσονται τελευταία και έχουν αρχίσει να χρησιμοποιούνται σε επιδεικτικές εφαρμογές.Στην εργασία αυτή παρουσιάζονται πειραματικά αποτελέσματα από μία σχεδίαση ηλιακού υβριδικού φωτοβολταϊκού/θερμικού (φβ/θ ή PV/T) συστήματος, το οποίο αποτελείται από διάταξη απαγωγής της θερμότητας, με κυκλοφορία νερού. / Photovoltaic thermal hybrid solar collectors, sometimes known as hybrid PV/T systems or PVT, are systems that convert solar radiation into thermal and electrical energy. These systems combine a photovoltaic cell, which converts electromagnetic radiation (photons) into electricity, with a solar thermal collector, which captures the remaining energy and removes waste heat from the PV module. The capture of both electricity and heat allow these devices to be more overall energy efficient than solar photovoltaic (PV) or solar thermal alone. In this work the PV/T system was studied with working fluid the water.

Submitted by LEANDRO MENDES PINTO null (leandromendesp@yahoo.com.br) on 2016-02-02T17:51:50Z No. of bitstreams: 1 Dissertação R2.pdf: 3124900 bytes, checksum: 4b8f01450ff24987ee9a730975769c25 (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-02-02T18:43:14Z (GMT) No. of bitstreams: 1 pinto_lm_me_guara.pdf: 3124900 bytes, checksum: 4b8f01450ff24987ee9a730975769c25 (MD5) / Made available in DSpace on 2016-02-02T18:43:14Z (GMT). No. of bitstreams: 1 pinto_lm_me_guara.pdf: 3124900 bytes, checksum: 4b8f01450ff24987ee9a730975769c25 (MD5) Previous issue date: 2016-01-07 / Na atualidade a eficiência energética é um dos assuntos mais citados nas indústrias, pois as empresas que investem em projetos de eficiência energética conseguem economizar recursos, ganhar competitividade e ajudar a amenizar a pressão sobre o aumento da oferta de energia. Postergar parte do investimento no aumento da oferta de energia permite ao governo e ao empresário liberarem recursos para outras prioridades, sem perda de qualidade, segurança no abastecimento e com ganhos sociais e ambientais. Este estudo apresenta critérios de aplicação da metodologia da eficiência energética em uma indústria siderúrgica onde são avaliadas três áreas dentro desta usina, tais como sistemas motrizes, sistemas térmicos e sistemas de iluminação, onde pode-se obter ganhos significativos implementando a metodologia da eficiência energética. / At present energy efficiency is one of the issues most frequently cited in industries, as companies that invest in energy efficiency projects can save resources, improve competitiveness and helps ease the pressure on increasing the supply of energy. Postpone part of the investment in increasing energy supply allows the government and the business owner to release resources for other priorities, without loss of quality, security of supply and social and environmental gains. This study presents application criteria of energy efficiency methodology in a steel industry which are evaluated in three areas of a steel mill, such as drive systems, thermal systems and lighting systems, where can be made significant gains by implementing the methodology of energy efficiency.

Submitted by ADRIANA LOPEZ VARGAS (adrialovargas@gmail.com) on 2016-04-14T14:20:54Z No. of bitstreams: 1 Analise de oportunidades de poligeração para edificações e cidades - Adriana Lopez Vargas.pdf: 3896010 bytes, checksum: 3c34d108a2a908648717c9ac5860cd3d (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-04-18T16:55:10Z (GMT) No. of bitstreams: 1 vargas_al_me_guara.pdf: 3896010 bytes, checksum: 3c34d108a2a908648717c9ac5860cd3d (MD5) / Made available in DSpace on 2016-04-18T16:55:10Z (GMT). No. of bitstreams: 1 vargas_al_me_guara.pdf: 3896010 bytes, checksum: 3c34d108a2a908648717c9ac5860cd3d (MD5) Previous issue date: 2016-02-24 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / A geração de energia distribuída em edificações e cidades tem sido proposta como uma importante alternativa para que os países ampliem a base tecnológica de suas matrizes energéticas. No caso do Brasil, a possibilidade da incorporação da geração distribuída em edificações apresenta amparo legal por meio de recentes regulamentações do setor elétrico e das normas de melhoria da eficiência energética de edificações. Por estas razões, novos empreendimentos imobiliários com visão de sustentabilidade ambiental, estão avaliando o uso da geração distribuída na etapa de planejamento. Nesta dissertação, foi analisada uma proposta para atender as necessidades energéticas de um hospital (vapor, água quente, resfriamento e eletricidade) considerando as informações de demanda, classificadas em oito dias típicos do ano, dois por cada estação do ano (outono, inverno, primavera e verão) sendo um dia de trabalho normal e outro de final de semana. A proposta consiste na otimização de uma superestrutura composta de diferentes tecnologias de geração e cogeração incluindo equipamentos solares, para assim obter a melhor configuração em termos econômicos. A superestrutura é flexível, ou seja, permite a venda ou compra de eletricidade e analisa três casos, verificando-se a viabilidade de gerar mais eletricidade. Finalmente são apresentados os resultados da configuração final obtida pela otimização. / Distributed generation in buildings and cities has been proposed as an important option for countries in order to include more technologies in their energy mixes. In Brazil, the possibility of including distributed generation in buildings has recent advances in energy policy and building energy efficiency standards. For these reasons, new construction projects of sustainable buildings include the assessment of distributed generation in the initial stages. In this work, we present an approach for attending energy needs (steam, hot water, cooling and electricity) of a hospital. The information about demand is classified in eight typical days, two for each season of the year (autumn, winter, spring and summer); a workday and a weekend day. The approach consists in the optimization of a superstructure containing different energy generation and cogeneration technologies like solar panels, for obtaining the best configuration in economic terms. The superstructure is flexible, this is, it allows buying or selling electricity. It also analyzes three cases, verifying the feasibility for generating more electricity. Finally, the results present the final configuration obtained from the optimization process.

This master thesis deals with the basic problems of solar thermal systems, which are using heat transfer medium. At the beginning this thesis describes basic components of the solar system, especially their meaning and attributes. Further in the thesis are mentioned heat transfer liquids for commercial usage which are used in those systems, their basic properties and dependence on temperature. There is described the physical nature of liquid viscosity and also ways how to measure them. The same is for measurement of liquid density and thermal conductivity. At the end was made measurement of dynamic viscosity of heat transfer liquids for commercial usage at different temperatures. In practical part of the thesis were mixed samples of alternative heat transfer mediums. It was measured their thermal and physical attributes, like for example density, dynamic viscosity and coefficient of volumetric expansion. Each measurement was compared and evaluated.

In this study, linear and non-linear models were trained on real data to mimic the relationship between household electricity consumption and indoor temperature, in the rooms of an apartment in downtown Stockholm. The aim was to better understand this relationship and to distinguish any divergence between the different rooms. With data from two weeks of measurements, the models proved to perform well when tested on validation data for almost all rooms, only showing performance dips for the middle room. A noticeable correlation between the electricity consumption and the indoor temperature was observed for all rooms except the bedroom. However, the benefits of using this information to predict the indoor temperature are limited and differ between the rooms. The household electricity consumption primarily brought beneficial information to the kitchen models, where most of the heat generating appliances were located. It was found that linear models were sufficient to represent the thermal systems of the rooms, performing equally well and often better than non-linear models.

A decomposition methodology based on the concept of "thermoeconomic isolation" applied to the synthesis/design and operational optimization of an advanced tactical fighter aircraft is the focus of this research. Conceptual, time, and physical decomposition were used to solve the system-level as well as unit-level optimization problems. The total system was decomposed into five sub-systems as follows: propulsion sub-system (PS), environmental control sub-system (ECS), fuel loop sub-system (FLS), vapor compressor and PAO loops sub-system (VC/PAOS), and airframe sub-system (AFS) of which the AFS is a non-energy based sub-system. Configurational optimization was applied. Thus, a number of different configurations for each sub-system were considered. The most promising set of candidate configurations, based on both an energy integration analysis and aerodynamic performance, were developed and detailed thermodynamic, geometric, physical, and aerodynamic models at both design and off-design were formulated and implemented. A decomposition strategy called Iterative Local-Global Optimization (ILGO) developed by Muñoz and von Spakovsky was then applied to the synthesis/design and operational optimization of the advanced tactical fighter aircraft. This decomposition strategy is the first to successfully closely approach the theoretical condition of "thermoeconomic isolation" when applied to highly complex, highly dynamic non-linear systems. This contrasts with past attempts to approach this condition, all of which were applied to very simple systems under very special and restricted conditions such as those requiring linearity in the models and strictly local decision variables. This is a major advance in decomposition and has now been successfully applied to a number of highly complex and dynamic transportation and stationary systems. This thesis work presents the detailed results from one such application, which additionally considers a non-energy based sub-system (AFS). / Master of Science

The successful delivery of low-carbon housing (both new and retrofitted) is a key aspect of the UK s commitment to an 80% reduction in carbon emissions by 2050. In this context, the inclusion of small-scale building-integrated renewable energy technologies is an important component of low carbon design strategies, and is subject to numerous regulation and incentive schemes (including the Renewable Heat Incentive (RHI)) set up by government to encourage uptake and set minimum performance benchmarks. Unfortunately there are numerous examples of in-use energy and carbon performance shortfalls for new and retrofitted buildings this is termed the performance gap . Technical and human factors associated with building subsystem performance, which are often not considered in design tools used to predict performance, are the root cause of performance uncertainty. The research presented in this doctoral thesis aims to develop and apply a novel probabilistic method of evaluating the performance uncertainty of solar thermal systems installed in the UK. Analysis of measured data from a group of low carbon retrofitted dwellings revealed that the majority of buildings failed to meet the designed-for carbon emissions target with an average percentage difference of 60%. An in-depth case study technical evaluation of one of these dwellings showed significant dysfunction associated with the combined ASHP/solar thermal heating system, resulting in a performance gap of 94%, illustrating that the performance gap can be regarded as a whole-system problem, comprising a number of subsystem causal factors. Using a detailed dataset obtained from the UK s largest field trial of domestic solar thermal systems, a cross-cutting evaluation of predicted vs. measured performance similarly revealed a discrepancy with a mean percentage difference in predicted and measured annual yield of -24%. Having defined the nature and extent of underperformance for solar thermal technology in the UK, causal factors influencing performance were mapped and the associated uncertainty quantified using a novel knowledge-based Bayesian network (BN). In addition, the BN approach along with Monte Carlo sampling was applied to the well-established BREDEM model in order to quantify performance uncertainty of solar thermal systems by producing distributions of annual yield. As such, the modified BN-based BREDEM model represents a significant improvement in the prediction of performance of small-scale renewable energy technologies. Finally, financial analysis applied to the probabilistic predictions of annual yield revealed that the current UK RHI scheme is unlikely to result in positive returns on investment for solar thermal systems unless the duration of the payments is extended or electricity is the primary source of heating.

Este trabalho trata de um estudo experimental da transferência de calor e de massa de um condensador evaporativo, bem como, da relação existente entre as grandezas envolvidas durante a sua operação. Para o desenvolvimento da pesquisa foi construído um condensador evaporativo de pequeno porte com dimensões proporcionais a condensadores comercialmente fabricados no Brasil para operar com R-22 como fluido refrigerante. Este condensador tem 35 colunas e 12 fileiras de tubos de cobre de 6,35 mm de externo e opera junto a uma instalação que proporciona o escoamento de R-22 por termossifao. O distribuidor de água também foi construído em cobre e o eliminador de gotas em alumínio, assim como a estrutura do condensador. As laterais e a bandeja de recolhimento de água foram construídas em vidro para permitir a visualização do escoamento da água que e aspergida sobre os tubos. A fim de variar as condições operacionais, este condensador foi acoplado a um ventilador centrifugo acionado por um conversor de freqüência e a um circuito que permitiu a variação da vazão de água aspergida sobre os tubos. Dos ensaios resultaram 79 amostras de medição, que serviram para verificar a relação existente entre grandezas, bem como avaliar os coeficientes de transferência de calor e massa. Foram determinados os coeficientes de transferência de calor médio e local para o R-22. Alem disso, foram verificadas as regiões onde ocorrem o dessuperaquecimento, a mudança de fase e o subresfriamento do fluido refrigerante, e foram confrontados os coeficientes globais de transferência de calor obtidos a partir dos dados experimentais com aqueles obtidos por correlações para as regiões de condensação e subresfriamento. Destas investigações, resultou uma correlação para o coeficiente global de transferência de calor que visa determinar esta grandeza através das condições operacionais e das características geométricas do condensador. O Maximo desvio encontrado entre os valores provenientes dos dados experimentais e aqueles calculados pela correlação foi inferior a 10%. / This work presents an experimental heat and mass transfer study of an evaporative condenser, as well as, the relationship between measured quantities obtained during its operation. A small scale evaporative condenser was built in agreement to the real size equipment geometric similarity. The small scale condenser has a bundle of 210 copper tubes, with the outer diameter equal to ¼ inch, which were arranged in 35 columns and 6 rows and operating connected to the thermosifon facility that promote R-22 flow. The spray water distributor is also built on copper and the drift eliminator on aluminum, as well as the evaporative condenser structure. This condenser bounds were constructed as a glass enclosure to allow for the spray water flow visualization. To evaluate the operational conditions, the equipment was attached to a centrifugal fan controlled by a frequency inverter and a spray water circuit which allows for water quantity changing. From the carried out tests, 79 measuring samples were obtained and used to verify the quantities relationship, as well as, to evaluate the heat and mass transfer coefficients For the R-22 were determined the local and average heat transfer coefficients. Furthermore, the dessuperheating, condensation and subcooling regions were verified and compared both, the experimental overall heat transfer coefficient and those calculated by correlations at condensation and subcooling zones. From these investigations a correlation for the overall heat transfer coefficient is proposed. Its application allows determining the coefficient using the operational conditions and the geometric condenser features. The higher deviation found between the experimental data and the presented correlation is lower to 10%.

Este trabalho trata de um estudo experimental da transferência de calor e de massa de um condensador evaporativo, bem como, da relação existente entre as grandezas envolvidas durante a sua operação. Para o desenvolvimento da pesquisa foi construído um condensador evaporativo de pequeno porte com dimensões proporcionais a condensadores comercialmente fabricados no Brasil para operar com R-22 como fluido refrigerante. Este condensador tem 35 colunas e 12 fileiras de tubos de cobre de 6,35 mm de externo e opera junto a uma instalação que proporciona o escoamento de R-22 por termossifao. O distribuidor de água também foi construído em cobre e o eliminador de gotas em alumínio, assim como a estrutura do condensador. As laterais e a bandeja de recolhimento de água foram construídas em vidro para permitir a visualização do escoamento da água que e aspergida sobre os tubos. A fim de variar as condições operacionais, este condensador foi acoplado a um ventilador centrifugo acionado por um conversor de freqüência e a um circuito que permitiu a variação da vazão de água aspergida sobre os tubos. Dos ensaios resultaram 79 amostras de medição, que serviram para verificar a relação existente entre grandezas, bem como avaliar os coeficientes de transferência de calor e massa. Foram determinados os coeficientes de transferência de calor médio e local para o R-22. Alem disso, foram verificadas as regiões onde ocorrem o dessuperaquecimento, a mudança de fase e o subresfriamento do fluido refrigerante, e foram confrontados os coeficientes globais de transferência de calor obtidos a partir dos dados experimentais com aqueles obtidos por correlações para as regiões de condensação e subresfriamento. Destas investigações, resultou uma correlação para o coeficiente global de transferência de calor que visa determinar esta grandeza através das condições operacionais e das características geométricas do condensador. O Maximo desvio encontrado entre os valores provenientes dos dados experimentais e aqueles calculados pela correlação foi inferior a 10%. / This work presents an experimental heat and mass transfer study of an evaporative condenser, as well as, the relationship between measured quantities obtained during its operation. A small scale evaporative condenser was built in agreement to the real size equipment geometric similarity. The small scale condenser has a bundle of 210 copper tubes, with the outer diameter equal to ¼ inch, which were arranged in 35 columns and 6 rows and operating connected to the thermosifon facility that promote R-22 flow. The spray water distributor is also built on copper and the drift eliminator on aluminum, as well as the evaporative condenser structure. This condenser bounds were constructed as a glass enclosure to allow for the spray water flow visualization. To evaluate the operational conditions, the equipment was attached to a centrifugal fan controlled by a frequency inverter and a spray water circuit which allows for water quantity changing. From the carried out tests, 79 measuring samples were obtained and used to verify the quantities relationship, as well as, to evaluate the heat and mass transfer coefficients For the R-22 were determined the local and average heat transfer coefficients. Furthermore, the dessuperheating, condensation and subcooling regions were verified and compared both, the experimental overall heat transfer coefficient and those calculated by correlations at condensation and subcooling zones. From these investigations a correlation for the overall heat transfer coefficient is proposed. Its application allows determining the coefficient using the operational conditions and the geometric condenser features. The higher deviation found between the experimental data and the presented correlation is lower to 10%.

Les systèmes solaires thermiques combinés à un système d’appoint tel que une chaudière, une pompe à chaleur ou intégrant une machine à absorption, peuvent jouer un rôle important dans la réduction des consommations des bâtiments pour les besoins de chauffage, de climatisation et de production d’eau chaude sanitaire. Dans ce sens, la caractérisation des performances énergétiques des systèmes thermiques est un enjeu crucial.Les méthodes de caractérisation actuellement disponibles sont soit basées sur plusieurs essais physiques séparés des composants du système à évaluer, chose qui ne prend pas en compte les vraies interactions entre ces derniers, soit sur des modèles physiques qui peuvent être complexes et difficilement identifiables notamment du fait que les systèmes actuels sont compacts et préfabriqués en usine. En l’absence de méthode fiable pour estimer les performances des systèmes solaires thermiques avant leur intégration au bâtiment, le marché de ses derniers subit de fortes contraintes pour son développement.Dans ce contexte il devient indispensable de développer une méthodologie générique qui peut être appliquée à différentes typologies de systèmes et qui pallie les difficultés rencontrées par les méthodes actuelles.L’approche d’évaluation proposée dans ce mémoire est constituée de quatre étapes principales : la détermination d’une séquence de test, l’essai du système dans un banc d’essai semi-virtuel selon la séquence déterminée, l’acquisition des données et l’identification d’un réseau de neurones artificiels (RNA) du système et enfin la simulation du modèle en vue de l’estimation de la consommation du système dans l’environnement désiré. L’avantage d’utiliser un modèle complètement « boîte noire » du système complet à l’aide des RNA la rend totalement « non intrusive ». La connaissance des paramètres internes aux systèmes (rendements, conductivités thermiques, régulation etc.) n’est en conséquence pas nécessaire pour l’application de la méthodologie.La validation de la méthodologie a été réalisée à travers plusieurs expérimentations numériques, pour 7 systèmes issus de 3 typologies différentes, durant lesquelles les estimations des RNA ont été comparées aux calculs des modèles physiques dans plusieurs conditions différentes (qualité du bâtiment, climat et surface du capteur). Une application de l’approche développée dans le cas de 5 systèmes réels a permis la confirmation de la pertinence de la méthodologie. / Solar thermal systems combined with a backup system such as a boiler, a heat pump or incorporating an absorption chiller, can play an important role in reducing buildings energy consumption for heating, cooling and hot water production needs. In this sense, characterizing the energy performance of thermal systems is crucial.Currently available methods of system characterization are either based on several separate physical tests of system components to be evaluated, which do not take into account the real interactions between them, or on physical models that can be complex and difficult to identify especially because systems nowadays are compact and prefabricated in the factory. Due to the lack of a reliable method to estimate the performance of solar thermal systems before their integration into buildings, their market faces a lot of impediment to be developed.In this context, it becomes essential to develop a generic methodology that can be applied to different types of systems which overcomes the difficulties encountered by the current ones.The proposed evaluation approach in this manuscript is composed of four main steps: determining a test sequence, testing the system in a semi-virtual test bench according to predetermined sequence, data acquisition and identifying an artificial neural network (ANN) of the system and finally the model simulation in order to estimate the system consumption in the desired boundary condition. Using a completely "black box" model of the whole system using the ANN makes the methodology totally "non-intrusive". No prior knowledge about the systems internal parameters (yields, thermal conductivities, regulation etc.) is necessary to apply the proposed approach.The methodology validation was performed through several numerical experiments for seven systems coming from three different typologies. During the validation process, ANN estimates were compared with calculations of physical models in several different conditions (quality of building, climate and collector area). The developed approach was applied to five real systems as well. The application results allowed the confirmation of the methodology relevance.