Orientador: Kamal Abdel Radi Ismail / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-11T03:46:08Z (GMT). No. of bitstreams: 1 Moraes_RaykleisonIgordosReis_M.pdf: 1558122 bytes, checksum: e287784c470caf116d151f9f9cc61f17 (MD5) Previous issue date: 2008 / Resumo: O presente trabalho procurou obter de uma forma detalhada o processo de formação de gelo no interior de cápsulas esféricas e geometrias alternativas recicláveis para o armazenamento de energia térmica, utilizando água e água-polietilenoglicol como PCM. Foi montada uma bancada de teste composta de um tanque de resfriamento e controlada com precisão de. As cápsulas utilizadas nos testes foram incrementadas com termopares tipo T, calibrados e localizados no centro da cápsula para investigar o efeito da solidificação do material. A faixa de variação de temperatura para os ensaios foram de - 25 à 5 ºC. Em seguida é apresentado um modelo matemático transiente em coordenadas esféricas e simulado usando a aproximação por diferenças finitas com o esquema da grade móvel. Os resultados experimentais são discutidos e as variáveis pesquisadas incluíram alguns parâmetros tais como: tempo de solidificação, temperatura do fluido de trabalho, concentração de polietilenoglicol, material da cápsula, velocidade, posição da frente de solidificação e o tamanho da cápsula no processo térmico de solidificação. O modelamento, junto com os resulta- dos experimentais forneceram parâmetros para construção de um armazenador modular para fins residenciais / Abstract: The present work looked for to get of a detailed form the similar process of icing in the interior of spherical capsules and geometrias for the storage of thermal energy being used water and water-polietilenoglicol as PCM. A composed group of benches of test of a controlled tank of cooling and with precision was mounted of ±1 ºC. Capsules used in the tests had been developed with thermocouples type T, calibrated and located in the center of the capsule to investigate the effect of the solidification of the material. The band of variation of temperature for the assays had been of 25 a 5 ºC. After that a transient in spherical coordinates is presented and simulated mathematic model using the approach for finite differences with the project of the movel scheme. The experimental results had been presented and argued some parameters such as: time for solidification, working fluid, concentration, capsule material , velocity and position of the solidification front and the size of the capsule in the thermal process of solidification. However, the together modeling with the experimental results had supplied parameters storing construction of a modular one for residential ends / Mestrado / Termica e Fluidos / Mestre em Engenharia Mecânica

Les procédés de stockage de chaleur haute température par voie thermochimique solide/gaz présentent un grand intérêt pour des applications à des centrales solaires thermodynamiques. Le couple réactif CaO/Ca(OH)2 est adapté à cette application pour des déstockages entre 350 et 550°C sous des pressions de vapeur entre 0,2 et 2bar. Les paramètres de transferts de chaleur et de masse de lits de Ca(OH)2+GNE ont été évalués au travers de corrélations et d'expérimentations. Des expérimentations ont permis d'atteindre des puissances en réaction de déstockage supérieures à 200kW.m-3 pour des durées compatibles avec les centrales solaires (1 à 15h). Un modèle 2D a été développé, validé et exploité afin d'étudier les influences couplées des différents paramètres sur les performances du TCS. Enfin, l'intérêt de différentes configurations d'intégration du TCS dans la centrale solaire ont été mis en évidence en termes de performances et de puissances thermiques échangées avec les sources et puits. / High-temperature heat storage processes using thermochemical solid/gas reaction exhibit great interest for applications in solar thermodynamic power plants. The reactive pair CaO/Ca(OH)2 is suitable for this recovery step application ranging from 350 to 550°C within steam pressures from 0.2 to 2 bar. Heat and mass transfer Ca(OH)2+GNE beds parameters were evaluated through correlations and experimentations. Experiments achieved recovery reaction powers above 200kW.m-3 for compatible durations with solar power plants (1 to 15 hours). A 2D model was developed, validated and exploited to study the coupled influences of different parameters on the performance of TCS. Finally, the benefit of different configurations of TCS integration within the solar power plant have been highlighted in terms of thermal performances and sources and sinks power exchanges.

Sverige har klimatmålet att nå negativa utsläpp av växthusgaser efter 2045 och det har en stor betydelse för att kunna uppnå Parisavtalet. Året 2021 stod bostäder och service för 43 % av den totala slutliga energianvändningen i Sverige och en minskning av den här användningen genom energieffektivisering är ett steg åt rätt riktning. Villa Ehrling byggdes 1982 i Falun och var tidigt ute med unika lösningar. I arbetet kartläggs de olika energieffektiviserande åtgärderna som förekommer i energivillan och energiberäkningar har genomförts över husets energiprestanda och klimatskal. Resultatet jämförs med dagens krav och andra lågenergihus för att avgöra om idéerna i villan kan implementeras än idag på nybyggnationer. Det primära syftet med villan är att utnyttja aktiv och passiv solenergi med vatten-och luftsolfångare samt lagra solenergi i villans stomme. Genom en unik utformning av fasaden med en 70 graders takvinkel, samt en orientering av byggnaden med stora glasspartier åt sydväst, kan värme tillföras från solinstrålningen under stora delar av året men också avskärmas under sommaren då solen står högre på himlen och värmebehovet är lägre. Utöver det har fasaden designats för att minska energiförluster från kall vind från norr med en låg takvinkel på 26 grader och begränsat antal fönsterytor. Villans ventilationssystem förvärmer tilluften genom lagrad värme i marken och återvinner värmen i frånluften. Överskottsvärmen kan lagras i ett stenmagasin under huset bestående av kullersten och tas ut när behovet finns. Ytterligare energieffektiviserande lösningar som förekommer i villan är återanvändandet av spillvärmen i avloppet med en avloppsvärmeväxlare. Resultatet av studien visar att villa Ehrling har en energiprestanda som varierar beroende på beteendet hos boende från omkring 35 % till 75 % lägre än de krav som ställs på nybyggnationer enligt Boverkets byggregler. Det här innebär att villan uppnår en hög energiklassificeringen med betygen A eller B än idag och hamnar i samma klassificering som andra lågenergihus. Byggnaden har en genomsnittlig värmegenomgångskoefficient på 0,314 W/(m2 K) vilket nästan uppfyller det högsta tillåtna värdet på denna koefficient idag. Jämfört med moderna lågenergihus fann den här studien att klimatskalet på villa Ehrling var mycket sämre. Slutsatsen från detta arbete är att trots villa Ehrling byggdes omkring 40 år sedan är det en villa som är mycket relevant än idag, både prestandamässigt och att mycket av husets energieffektiviserande lösningar är vanligt förekommande i nybyggnationer och andra lågenergihus idag. / Sweden has the goal of reaching negative emissions in the year 2045 to be able to reach the Paris agreement. In the year 2021, 43 % of the total energy consumption in Sweden came from housing and service and more efficient buildings is a step in the right direction. Villa Ehrling was built in 1982 in Falun, Sweden, with some interesting concepts. This report will present the concepts of the building and calculations that cover the performance of the house and its envelope. The results are compared with the requirement of how well insulated a house should be when built today. The performance and concepts of Villa Ehrling is also compared with other low-energy buildings to determine if some of Ehrlings concepts are of any use to implement in other buildings. The primary purpose of villa Ehrling is to utilize solar energy actively with air and water solar collectors, and passively by storing heat in building parts. A unique design of the façade, with and an orientation towards southwest with large areas of glass and a roof with an angle of 70 degrees, enables the ability to absorb solar heat during larger parts of the year and block the sun rays during summer when the heat demand is low. The façade contains small areas of glass towards northeast and a low roof angle of 26 degrees to reduce energy losses causes by cold winds.The ventilation system utilizes stored heat in the ground to preheat incoming air. The heat in the outflowing air is also utilized to preheat incoming air. Villa Ehrling has a heat storage made of cobblestone where energy is provided by heated air, and the energy can be extracted when the need occurs. Heat from showers and hot tap water usage is used in a heat exchanger and preheats tap water.The result of the study shows that villa Ehrling has an energy performance that varies depending on the behaviour of residents from about 35 % to 75 % lower than the requirements for new constructions according to the Swedish National Board of Housing, Building and Planning's building regulations. This means that the villa achieves a high energy classification with the grade A or B even today and ends up in the same classification as other low-energy houses. The building has an average heat transfer coefficient of 0.314 W/(m2 K), which almost meets the maximum permissible value of this coefficient today. Compared to modern low-energy houses, this study found that the envelope of villa Ehrling was much worse.The conclusion from this work is that despite villa Ehrling being built about 40 years ago, it is a villa that is very relevant even today, both in terms of the energy performance and that much of the house's energy efficient solutions are common in new buildings and other low-energy houses today.

The significant increase in energy requirements across the world, provides several opportunities for innovative methods to be developed to facilitate the storage and utilization of energy. The major energy demand is in the form of electrical energy for domestic as well as industrial sectors, a large part of which are the heating and cooling requirements. Appropriate utilization of thermal energy storage can effectively aid in reducing the electrical demand by storage and release of this thermal energy during peak hours. Thermal Energy Storage using Phase Change Materials (PCMs) is an attractive method of energy storage, with a wide variety of potential applications. Several configurations have been tested by researchers to develop energy storage devices with PCMs. The cycling of melting and solidification of PCMs results in storage and release of heat at a relatively small temperature difference. Design and deployment of these storage systems have certain challenges and considerations associated to them for instance, when used in buildings, PCMs should be non-toxic, non-corrosive, and others. In this thesis, we aim to provide models for designing Latent Thermal Energy Storage (LTES) devices with PCMs, based on their operating conditions, thermophysical properties of materials, and geometric parameters. The models are developed considering fluid dynamics and heat transfer involved in melting and solidification of PCMs. Parameters like inlet temperature and velocity, and volume of storage container are varied to determine the time taken for melting or solidification. For sizing and predicting performance of the storage devices we aim at presenting an analytical correlation, with time taken for melting as the variable defining the ‘charging/discharging time’ of storage device. Along with this, a transient model is developed to predict amount of PCM melted/solidified, along with rate of latent energy storage in defined time period intervals.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The increased necessity to obtain power from other sources than conventional fossil fuels has led to the growing interest in solar power. The problem with the proposed technology is that it can only provide power during the day and therefore requires some sort of storage system, if power is to be supplied throughout the day and night. A number of storage systems exist, but the one of particular interest for this research, is packed rock beds. Rock beds have the advantage that if designed right, they have the potential to be one of the most cost effective means of storing thermal energy for solar power plants. Discrete Element Models (DEM) of rock beds were therefore developed through both experimental and numerical procedures, by conducting a series of sensitivity, calibration and verification studies. The developed models were then used to study various aspects associated with rock beds, which were either too impractical, impossible or too expensive to conduct through actual experimental work. This research focused specifically on the potential of constructing self-supporting tunnels within the rock beds in order to improve the air flow uniformity through the bed, while minimizing the pressure drop. It was observed that if the appropriate steps were followed, stable self-supporting tunnels could be formed. Valuable information such as the rock orientations resulting from different packing directions could also be derived from the models and finally, a method to convert the DEM models into the appropriate format such that it could be imported into a CFD preprocessor for future CFD studies, was developed. / AFRIKAANSE OPSOMMING: Die verhoogde noodsaaklikheid om energie te verkry uit ander bronne as konvensionele fossielbrandstowwe, het gelei tot die groeiende belangstelling in sonkrag energie. Die probleem met die voorgestelde tegnologie is dat dit net energie gedurende die dag kan voorsien en dus word daar ’n stoorstelsel benodig indien energie deur beide die dag en nag voorsien moet word. Tans bestaan daar wel ’n aantal van hierdie stoorstelsels, maar die een wat van besondere belang is in hierdie navorsing, is verpakte klip beddens. Klip beddens het die voordeel dat, indien dit reg ontwerp is, dit oor die potensiaal beskik om een van die mees koste-doeltreffende middels te wees vir die stoor van termiese energie vir sonkragstasies. Diskreet Element Modelle (DEM) van die klip beddens is ontwikkel deur gebruik te maak van beide experimentele en numeriese metodes waartydens ’n reeks sensitiwiteits-, kalibrasie- en verifiëring studies uitgevoer is. Die ontwikkelde modelle is gebruik om verskeie aspekte van klip beddens te ondersoek, wat of te onprakties, onmoontlik of te duur is vanuit ’n eksperimentele oogpunt. Hierdie navorsing het spesifiek gefokus op die potensiaal om self-ondersteunende tonnels binne in die klip beddens te vorm, ten einde die egaligheid van die lugvloei deur die bed te verbeter, terwyl die drukval geminimeer word. Daar is waargeneem dat stabiele self-ondersteunende tonnels wel gevorm kon word indien die toepaslike stappe gevolg is. Waardevolle inligting soos die klip oriëntasies wat as gevolg van die verskillende verpakkings rigtings onstaan kon ook vanuit die model verkry word. Ten slotte is ’n metode ontwikkel om die DEM modelle na die toepaslike formaat te omskep sodat dit ten einde gebruik kan word in numeriese vloeidinamika studies.

Disertacijoje nagrinėjami būdingi šilumos akumuliacinės talpos veikimo režimai, susiformuojantys nedidelės galios kogeneracinėje jėgainėje, tiriamas šiluminės stratifikacijos susidarymas tokioje talpoje ir atliekamas jos modeliavimas. Pagrindinis disertacijos tikslas – ištirti nedidelės galios kogeneracinės jėgainės šilumos akumuliacinės talpos veikimo režimų ypatumus, sudaryti algoritmą, padedantį parinkti tokios talpos tūrį ir pateikti modelį, leidžiantį nustatyti šiluminę stratifikaciją akumuliacinėje talpoje bet kuriuo jos veikimo metu. / The dissertation investigates typical operation modes of the heat storage tank in the small-scale cogeneration (CHP) plant, analyses formation of thermal stratifi-cation in such storage tank and presents the simulation of the stratification. The main aim of the dissertation is to investigate peculiarities of operation modes of heat storage tank in small-scale CHP plant, develop an algorithm allowing to choose the storage tank volume and present a model allowing determination of thermal stratification in the storage tank at any time of its operation.

This study describes a simulation-based approach for informing the incorporation of Phase Change Materials (PCMs) in buildings designed to the "Passive House" standard. PCMs provide a minimally invasive method of adding thermal mass to a building, thus mitigating overheating events. Phase change transition temperature, quantity, and location of PCM were all considered while incrementally adding PCM to Passive House simulation models in multiple climate zones across the United States. Whole building energy simulations were performed using EnergyPlus from the US Department of Energy. A prototypical Passive House with a 1500 Watt electric heater and no mechanical cooling was modeled. The effectiveness of the PCM was determined by comparing the zone-hours and zone-degree-hours outside the ASHRAE defined comfort zone for all PCM cases against a control simulation without PCM. Results show that adding PCM to Passive Houses can significantly increase thermal comfort so long as the house is in a dry or marine climate. The addition of PCM in moist climates will not significantly increase occupant comfort because the majority of discomfort in these climates arises due to latent load. For dry or marine climates, PCM has the most significant impact in climates with lower cooling degree-days, reducing by 93% the number of zone-hours outside of thermal comfort and by 98% the number of zone-degree-hours uncomfortable in Portland, Oregon. However, the application of PCM is not as well suited for very hot climates because the PCM becomes overcharged. Only single digit reductions in discomfort were realized when modeling PCM in a Passive House in Phoenix, Arizona. It was found that regardless of the climate PCM should be placed in the top floor, focusing on zones with large southern glazing areas. Also, selecting PCM with a melt temperature of 25°C resulted in the most significant increases in thermal comfort for the majority of climates studied.

Energy systems with a high portion of renewable energy from wind and solar power can suffer from fluctuations in production due to weak winds or cloudy weather, which may affect the electricity price. When producing heat and power in a combined heat and power plant, an additional heat storage tank can be used to store the heat surplus which is obtained when the power production is high, and the heat demand is low. To optimize heat and power production economically, short-term planning can be applied. Short-term planning covers the production in the near future of 1-3 days. The optimization in this degree project is based on the district heating production, which means that the heating demand always needs to be fulfilled. The district heating production is based on the weather. Therefore a suitable period for simulation is three days due to the accuracy of the weather forecasts are reasonable. The optimization is performed on the district heat system in Gävle, Sweden. The system comprises several different production units, such as combined heat and power plants, backup plants, and industrial waste heat recovery. Two different models are made, one using linear programming and one using mixed integer non-linear programming. The model stated as a linear programming problem is not as accurate as of the one stated as a mixed integer non-linear programming problem which uses binary variables. Historical input data from Bomhus Energi AB, a company owned together by the local heat and power supplier Gävle Energi AB and the pulp and paper manufacturer BillerudKorsnäs AB, was given to simulate different scenarios. The different scenarios have various average temperatures and in some scenarios are there some issues with the pulp and paper industry affecting the waste heat recovery. In all scenarios is the heat storage tank charged when the demand is low and then discharged when the demand increases to avoid starting some of the more expensive backup plants if possible. The simulation time varies a lot between the two approaches, from a couple of seconds to several hours. Particularly when observing scenarios with a rather high demand since the backup generators use binary variables which take a lot of time to solve.

Research in solar heating has traditionally focused solely on increasing the system efficiency by improving the technical components. In this thesis the technical methodology and system boundaries are widened to connect the technical aspects with market actors that are highly influential on the implementation of solar technology. The research was focused on how social aspects can be brought into technical studies to improve the understanding of solar heating, and how solar thermal technology can be optimized in a larger energy system. Both heat storage and different system solutions have been investigated. The thesis is built on a number of sub-projects exploring different aspects of solar heating. Improved components and system configurations may result in higher fractional energy savings and thereby make solar energy go from a marginal contribution to be the main energy supplier. Both components and systems are considered in this thesis. The solar heating technology has been shown to work well, also in unique system solutions. Technical possibilities with medium-sized stores for single-family houses and seasonal stores for residential areas are presented. Methods to bring studies of technology and actor studies together are also proposed; domestic hot water use has been modelled based on time-use data, while a multifaceted market situation, in which new system solutions must find their way, has been described by the solar and pellet industries. The complexity of assessing installation and use of a particular heating system in relation to the overall energy system is also discussed. Overall, this thesis shows that successful use of solar heating does not only come down to proper technical solutions, but also depends on the interaction between technology and market actors. A widened perspective, including the social context in which the heating system appears, is then essential. This thesis constitutes a step in that direction.

In this thesis, the possible usage of phase change materials in military shelters with the aim of decreasing the heating effect of the solar radiation is presented. In order to meet the rapidly growing demand for energy in military applications, a passive cooling technique, specifically, storing thermal energy with phase change materials is analyzed by using experimental approach. Not only different types of phase change materials but also different amounts of them are examined during the solar loading experiments. In order to simulate solar heat loading on prototype military shelters, solar radiation test or in other words sunshine test that is stated in military standard MIL