Orientador: Vicente Luiz Scalon / Banca: Carlos Teófilo Salinas Sedano / Banca: Santiago Del Rio Oliveira / Resumo: As discussões recentes sobre sustentabilidade tem destacado os sistemas de aquecimento solar como alternativa adequada para aquecimento de água. Estes sistemas tem ganho notoriedade tanto para uso doméstico como no aquecimento de piscinas. Um dos aspectos que é frequentemente destacado como principal dificuldade para a sua popularização, entretanto é o custo de sua implantação. Uma das formas de reduzir este custo é minimizando o número de componentes e simplificando o sistema. Nesta linha de desenvolvimento muito tem se discutido sobre o uso de sistemas integrados coletor-armazenador (ICS). Baseando-se nestas avaliações, este trabalho pretende estudar diferentes configurações geométricas de coletores solares com armazenador integrado do tipo cubóide e verificar a influência sobre o aproveitamento de energia térmica quando se utiliza diferentes dispositivos para direcionar o fluxo de água quente. A partir de simulações numérico-computacionais é possível identificar as geometrias que apresentam melhor estratificação térmica no armazenador. A estratificação da temperatura em um armazenador é um fator extremamente importante no estudo de coletores solares, pois determina a porção de temperatura mais elevada. O modelo base, validado experimentalmente na literatura, foi utilizado com condições de fluxos de calor incidente e de perda por resfriamento constantes com boa concordância de resultados. Modificações geométricas foram implementadas e avaliadas para otimizar os parâmetros de projeto deste tipo de coletores solares integrados. Outras análises alterando o volume do sistema coletor-armazenador foram realizadas: um com 200 litros de capacidade e outro com 300 litros, de maneira a estabelecer um tamanho ótimo do sistema. Para visualizar a estratificação do armazenador... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Recent discussions highlighted the sustainability of solar heating systems as an apropriate alternative for heating water. These systems has gained prominence for both household and swimming pool heating. One aspect that is often highighted as the main obstacle to its popularity is the cost of its implementation. One way to reduce this cost is to minimize the number of components and simplifying the system. In this field of development has long been discussed about the use of integrated collector-storage (ICS). Based on these evaluations, this work analyzes different geometrical configurations of integrated solar collector-storage with storage type cuboid and the influence on the use of thermal energy when you use different devices to direct the flow of hot water. From numerical-computational simulations, the geometry with better thermal stratification in the storage can be identified. the stratification of temperature in a storage is an extremely important factor in the study of solar collectors, because it determines the portion of higher temperature. The base model, experimentally validated in the literature, was used with constant conditions of incident head flux and loss for cooling. Geometric changes were implemented and evaluated to optimize the design parameters of this type of integrated solar collectors. Further analysis by changing the volume of the collector-storage system were carried out: a 200 liter capacity and another with 300 liters, in order to establish and optimum size of the system. To view the stratification of the storage, images with the temperature profile are shown at the end of the heating and cooling periods and the following graphics show the stratification coefficient. The CFD method allowed to obtain results with good agreement with those used as the basis from the literature. Results... (Complete abstract click electronic access below) / Mestre

The increased penetration of renewable energy sources poses new challenges for grid stability. The stochastic and uncontrollable generation of solar and wind power cannot be adjusted to match the load profile, and the transition away from traditional synchronous generators is reducing the grid capacity to arrest and recover from frequency disturbances. Additionally, the distributed nature of many renewable energy sources makes centralized control of generation more complicated. The traditional power system paradigm balances the supply and demand of electricity on the grid by regulating generation. As this becomes more difficult, one alternative is to adjust the load instead. This is not entirely novel, and utilities have incentivized large industrial customers to reduce consumption during peak hours for years. However, the residential sector, which constitutes 37% of electricity consumption in the U.S., currently has very little capacity for load control. Smart electric water heaters provide utilities with an appliance that can be remotely controlled and serves as a form of energy storage. They have very fast response times and make up a large amount of residential energy consumption, making them useful for load peak shifting as well as other ancillary grid services. As smart appliances become increasingly widespread, more and more devices can be brought into the utility's control network and aggregated into a flexible resource on a megawatt scale. This work demonstrates the usefulness of aggregated electric water heaters for peak shifting and frequency response. Because a large number of assets are required, emulators are developed based on observations of real devices. Emulated water heaters are then connected to an energy resource aggregator using an internet-of-things network. The aggregator successfully uses these assets to shift consumption away from peak hours. An algorithm was developed for detecting upward frequency disturbances in real-time. The aggregator uses this algorithm to show that an aggregation of water heaters is well-suited to respond to these frequency disturbances by quickly adding a large amount of load to the grid.

Les défis environnementaux et l'augmentation de la population viennent en preuve de l'importance de réfléchir à d'autres moyens de production tout en maintenant la sécurité et la fiabilité du système électrique. La sûreté du système électrique exige à tout moment que la production soit égale à la demande des consommateurs, pour ça, différentes solutions sont déjà mises en place, ces solutions consistent à mettre en marche des moyens de pointes couteux et polluants pendant les périodes de pointes, mais comme les moyens de production son insuffisants et vue la difficulté d'exploitation de nouveaux moyens de production, une nouvelle réflexion sur la gestion de la demande est apparue; celle-ci se base sur la possibilité à gérer la demande du consommateur final au lieu de la satisfaire.L'objectif de la thèse est d'étudier la possibilité à rendre des services au système électrique en appliquant des actions de contrôle dites de DR (Demand Response), sur différents types de charges électriques. Ces actions de DR représentent des interruptions partielles appliquées sur les charges électriques de type thermique. Notre choix s'est basé sur ces types de charges parce que celles-ci emmagasinent de la chaleur respectivement dans l'air et dans l'eau; qui peut être restituée pendant la période de contrôle ou d'interruption. Néanmoins, il existe un effet négatif qui suit le contrôle de ces charges car l'énergie effacée de ces charges est reportée à l'instant de reconnexion de celles-ci; ce report prend la forme d'un pic de consommation nommé CLPU (Cold Load Pick-Up) et qui apparait au moment de la reconnexion. Le CLPU représente un problème qui doit être géré, et sa magnitude dépend des types d'actions de contrôle qu'on veut implanter et aussi des conditions du système électrique (contingence, défaillance d'une unité de production ou besoin de réserve de puissance). Pendant la thèse, le CLPU est contrôlé et optimisé ainsi que la puissance effacée. Un cas d'étude est présenté sur la contribution des actions de gestion de la demande à l'ajustement entre la demande et la production et l'effet généré sur le réglage secondaire de fréquence.

Made available in DSpace on 2014-06-11T19:25:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-07-13Bitstream added on 2014-06-13T20:33:04Z : No. of bitstreams: 1 sales_fb_me_bauru.pdf: 1185139 bytes, checksum: ba8e8304a72e250dcb73d00e64d9a913 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / As discussões recentes sobre sustentabilidade tem destacado os sistemas de aquecimento solar como alternativa adequada para aquecimento de água. Estes sistemas tem ganho notoriedade tanto para uso doméstico como no aquecimento de piscinas. Um dos aspectos que é frequentemente destacado como principal dificuldade para a sua popularização, entretanto é o custo de sua implantação. Uma das formas de reduzir este custo é minimizando o número de componentes e simplificando o sistema. Nesta linha de desenvolvimento muito tem se discutido sobre o uso de sistemas integrados coletor-armazenador (ICS). Baseando-se nestas avaliações, este trabalho pretende estudar diferentes configurações geométricas de coletores solares com armazenador integrado do tipo cubóide e verificar a influência sobre o aproveitamento de energia térmica quando se utiliza diferentes dispositivos para direcionar o fluxo de água quente. A partir de simulações numérico-computacionais é possível identificar as geometrias que apresentam melhor estratificação térmica no armazenador. A estratificação da temperatura em um armazenador é um fator extremamente importante no estudo de coletores solares, pois determina a porção de temperatura mais elevada. O modelo base, validado experimentalmente na literatura, foi utilizado com condições de fluxos de calor incidente e de perda por resfriamento constantes com boa concordância de resultados. Modificações geométricas foram implementadas e avaliadas para otimizar os parâmetros de projeto deste tipo de coletores solares integrados. Outras análises alterando o volume do sistema coletor-armazenador foram realizadas: um com 200 litros de capacidade e outro com 300 litros, de maneira a estabelecer um tamanho ótimo do sistema. Para visualizar a estratificação do armazenador... / Recent discussions highlighted the sustainability of solar heating systems as an apropriate alternative for heating water. These systems has gained prominence for both household and swimming pool heating. One aspect that is often highighted as the main obstacle to its popularity is the cost of its implementation. One way to reduce this cost is to minimize the number of components and simplifying the system. In this field of development has long been discussed about the use of integrated collector-storage (ICS). Based on these evaluations, this work analyzes different geometrical configurations of integrated solar collector-storage with storage type cuboid and the influence on the use of thermal energy when you use different devices to direct the flow of hot water. From numerical-computational simulations, the geometry with better thermal stratification in the storage can be identified. the stratification of temperature in a storage is an extremely important factor in the study of solar collectors, because it determines the portion of higher temperature. The base model, experimentally validated in the literature, was used with constant conditions of incident head flux and loss for cooling. Geometric changes were implemented and evaluated to optimize the design parameters of this type of integrated solar collectors. Further analysis by changing the volume of the collector-storage system were carried out: a 200 liter capacity and another with 300 liters, in order to establish and optimum size of the system. To view the stratification of the storage, images with the temperature profile are shown at the end of the heating and cooling periods and the following graphics show the stratification coefficient. The CFD method allowed to obtain results with good agreement with those used as the basis from the literature. Results... (Complete abstract click electronic access below)

Orientador: Jose Antonio Siqueira Dias / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-14T11:25:46Z (GMT). No. of bitstreams: 1 Ormenese_Marcela.pdf: 17981897 bytes, checksum: c7b7714358950bc575686565e846f762 (MD5) Previous issue date: 2009 / Resumo: Os sistemas de aquecimento solar disponíveis comercialmente, embora proporcionem boa economia de energia elétrica, não apresentam bom desempenho em dias com baixa radiação, pois o boiler é automaticamente preenchido com água fria toda vez que ocorre consumo de água quente. Neste trabalho é proposto e estudado um sistema de aquecimento solar que é otimizado para proporcionar uma mínima utilização da energia elétrica no auxílio ao aquecimento de água. Um controlador fuzzy analisa a intensidade da radiação solar, a temperatura da água dentro do boiler, a quantidade de água dentro do boiler e controla a entrada de água fria no boiler, otimizando o sistema. Foram modelados dois sistemas de aquecimento: um convencional e este sistema com o controlador fuzzy; e, através de simulações, suas eficiências foram comparadas. Os resultados obtidos em simulação mostram que o sistema proposto com controlador fuzzy apresenta eficiência superior aos sistemas convencionais. Para um período de três dias de inverno, com baixa radiação solar, o sistema convencional consumiu uma energia elétrica de 10,08 kWh enquanto que o sistema proposto consumiu apenas 1,86 kWh. / Abstract: Although significant savings in electrical energy are achieved with commercially available solar water heaters, they do not present a good performance in days that the radiation is not good, because the boiler is filled with cold water whenever the hot water is used. In this work, a new solar heating system, which minimizes the use of electrical energy, is proposed. The proposed system uses a fuzzy controller that analyzes the intensity of solar radiation, the temperature of the water inside the boiler and the volume of water inside the boiler, to actuate on a On/Off valve which controls the boiler's input of cold water. Two solar heating systems were modeled: a conventional system and the new proposed system with the fuzzy controller; and their efficiencies were compared using computer simulations. The obtained results show that the proposed system with the fuzzy controller presents a much higher performance when compared to the traditional system. Simulation results indicate that for a three winter days period, with low intensity solar radiation, the conventional system consumed 10.08 kwh of electrical energy while the proposed system needed only 1.86 kwh to achieve the same performance. / Universidade Estadual de Campi / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica

Thesis (MDF)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Deforestation, increasing pollution levels, diminishing non-renewable energy reserves, the resulting global warming, and climate change are areas of concern to environmentalists and the whole global village. It appears that the solution lies in the exploitation of renewable, clean and sustainable energy resources. Solar energy is one of the renewable, clean and environmentally friendly energy resources readily available in most tropical countries of the world, including Namibia. The research was conducted in the Rocky Crest suburb of Windhoek, Namibia. The research focused on the exploration barriers in the diffusion of solar water heaters (SWHs) for generating hot water for Rocky Crest residents. The investigation involved data collection from the stakeholders, including the residents of Rocky Crest suburb, SWH suppliers, financial institutions, non-governmental organisations (NGOs) and the Ministry of Mines and Energy (MME) in Namibia. The results of this study introduce information that can largely benefit the Rocky Crest residents, MME, NGOs, financial institutions and relevant stakeholders. It can also act as a departure point for further studies on the subject of renewable energy sources, their exploitation and the impact thereof. Furthermore, solutions to the current problems of diminishing non-renewable energy reserves and the impact of pollutant energy sources can be identified and implemented.

Thesis (MBA)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: South Africa is experiencing an energy shortage and volatile supply of electricity. This situation is placing pressure on businesses and citizens and is opening avenues into the renewable sector. This study investigates servicisation as a potential means to assist in the alleviation of energy consumption on the national power grid, and answers whether servicisation in the solar water heating sector could pose as a viable business venture. The main research goal was to investigate whether servicisation within a housing estate could be favourably received. The majority of residents in this high-income bracket were more willing to invest their own capital in renewables rather than being provided with a solar water heater through servicisation. Knowledge of solar water heating is extremely poor amongst consumers, and this contributes to the lack of penetration of solar water heaters in the industry to date. To further exacerbate the situation, installations are often poorly executed, leading to negative experiences by consumers. Initially it was assumed that post 2012, all homes built would be installed with solar geysers or heat pumps, due to legislation. However, surprisingly this was not the case, as a large portion of homes built between 2012 & 2013 have not complied with this legislation.

Les défis environnementaux et l’augmentation de la population viennent en preuve de l’importance de réfléchir à d’autres moyens de production tout en maintenant la sécurité et la fiabilité du système électrique. La sûreté du système électrique exige à tout moment que la production soit égale à la demande des consommateurs, pour ça, différentes solutions sont déjà mises en place, ces solutions consistent à mettre en marche des moyens de pointes couteux et polluants pendant les périodes de pointes, mais comme les moyens de production son insuffisants et vue la difficulté d’exploitation de nouveaux moyens de production, une nouvelle réflexion sur la gestion de la demande est apparue; celle-ci se base sur la possibilité à gérer la demande du consommateur final au lieu de la satisfaire.L’objectif de la thèse est d’étudier la possibilité à rendre des services au système électrique en appliquant des actions de contrôle dites de DR (Demand Response), sur différents types de charges électriques. Ces actions de DR représentent des interruptions partielles appliquées sur les charges électriques de type thermique. Notre choix s’est basé sur ces types de charges parce que celles-ci emmagasinent de la chaleur respectivement dans l’air et dans l’eau; qui peut être restituée pendant la période de contrôle ou d’interruption. Néanmoins, il existe un effet négatif qui suit le contrôle de ces charges car l’énergie effacée de ces charges est reportée à l’instant de reconnexion de celles-ci; ce report prend la forme d’un pic de consommation nommé CLPU (Cold Load Pick-Up) et qui apparait au moment de la reconnexion. Le CLPU représente un problème qui doit être géré, et sa magnitude dépend des types d’actions de contrôle qu’on veut implanter et aussi des conditions du système électrique (contingence, défaillance d’une unité de production ou besoin de réserve de puissance). Pendant la thèse, le CLPU est contrôlé et optimisé ainsi que la puissance effacée. Un cas d’étude est présenté sur la contribution des actions de gestion de la demande à l‘ajustement entre la demande et la production et l’effet généré sur le réglage secondaire de fréquence. / Environmental challenges and the increasing in electric demand show the importance of considering other form of production while maintaining the safety and reliability of the electrical system. The electrical power systems stability lays on a fundamental constraint: supply and demand must be equal at each instant, so, different solutions are already in place, these solutions include controlling generators’ production during peak periods. But, power units (mainly nuclear, thermal, hydro) capacities are not always sufficient and flexible to follow the demand variations during these periods; an alternative solution to this insufficiency is to make the demand following the electrical power generation by providing bulks of electrical power to the power system by curtailing consumer’s electric load consumption. Such a solution that represents a new organization in the power system industry can be done by Demand Side Management (DSM) actions. The aim of the thesis is to study the possibility to offer services to the electrical system by applying control actions called DR (Demand Response) on different types of electric loads. These DR actions represent partial interruptions of electrical loads’ consumption and especially thermal loads’ consumption.Our choice was based on the thermal electric loads because they store heat respectively in air and water, which can be restored during the control period or interruption. However, there is a negative effect that follows the control of these type of loads because the reduced energy during curtailment period is deferred at the time of reconnection, this deferred power takes the form of a power peak named CLPU (Cold Load Pick-Up), which appears at the time of reconnection. The CLPU is a problem that must be managed, and its magnitude depends on the type of control actions and on the electric system conditions (ie: contingency or failure of a generating unit). In the thesis, the CLPU is controlled and optimized as well as the load reduction during curtailment period. The contribution of control actions in balancing mechanisms and the effect produced on the secondary control of frequency are analyzed.

Graduation date: 2003 / Best scan available on figures. Original figures are dark.

Concern with global climate change has led to the interest in the use of natural refrigerants, such as carbon dioxide, as replacements in heat pump systems. When operating in a transcritical cycle, carbon dioxide heat pumps are well suited for use in high temperature water heating heat pumps. In this work, four systems are analyzed: with and without the use of a suction line heat exchanger, and two water heating schemes. These two schemes involve the heating of water to its desired temperature at a low water flow rate in a single pass through the heat pump, and the heating of water at a high water flow rate, but requiring multiple passes. The performance and resulting heat exchanger size of these four systems is analyzed through the development of an overall system model. This system model uses component-level models that were developed based upon heat exchanger geometry and subsequently validated through experimental testing on a test facility developed for this purpose.