Sensible energy storage for solar domestic hot water (SDHW) systems is space consuming and heavy. Latent heat energy storage systems (LHESSs) offer a solution to this problem. However, the functionality of a LHESS during simultaneous charging/discharging, an operating mode encountered when used with a SDHW, had not been studied experimentally. A small scale vertical cylindrical LHESS, with dodecanoic acid as the phase change material (PCM), was studied during separate and simultaneous charging/discharging. Natural convection was found to have a strong influence during melting, but not during solidification. During simultaneous operation heat transfer was limited by the high thermal resistance of the solid PCM. However, when the PCM was melted, direct heat transfer occurred between the hot and cold heat transfer fluids, indicating the significance of the PCM phase on heat transfer in the system. The results of this research will lead to more optimally designed LHESS for use with SDHW. ?

Solar domestic hot water (SDHW) systems collect energy with a solar collector, transfer the energy to the water through a heat exchanger, and store it in a storage tank. The water in the tank should be thermally stratified to the highest possible degree to maximize system efficiency because a stratified tank has higher availability than a mixed tank temperature. The objective of this research is to develop a manifold that will enhance thermal stratification in the SDHW tank. In this work a new immersion shell-and-coil heat exchanger with a perforated manifold that extends from the heat exchanger to the top of the tank was used to enhance the thermal stratification. The purpose of the perforated manifold is to deliver the water heated by the heat exchanger to the tank at the level where the temperature of the water in the tank matches the temperature of the heated water, thereby enhancing stratification. The effectiveness of the perforated manifold was determined experimentally. An experimental set-up was designed and constructed. The experimental results were analyzed for each manifold design then compared to determine the most effective manifold. The experimental work included testing and comparing different manifold designs. To simulate an actual system, experiments were conducted on three initial tank conditions, namely cold, hot, and mixed tank conditions. The thermal performance of the system in terms of tank availability and entropy, maximum tank temperature, and thermal stratification were studied. A method to determine and design a perforated manifold that works with the standard Canadian SDHW system was established and evaluated experimentally. An availability analysis approach was developed to evaluate the thermal performance of manifolds, which have been operated at different times of the year. Theoretically, gradually increasing the diameter of the holes in the manifold from the bottom into the top should reduce the unwanted flow of cold water from the bottom of the tank to the manifold and enhance the thermal performance of the manifold. However, the experimental did not confirm this.

No description available.

Renewable energy has become the world's fastest growing energy source as a direct result of increasing concerns about the environmental damage that is being caused by fossil fuel and nuclear energy use. With the exception of large-scale hydro, however, very little of Australia's electricity is supplied from renewable energy. Due to our lack of experience with the use of most renewable energy technologies and the associated lack of knowledge regarding their true potential, doubts remain as to how much electricity could be generated or displaced by renewable energy. Although renewable energy industries in Australia have recently begun to experience strong growth, this growth could be curtailed if there is a lack of faith in the potential for renewable energy. The aim of this study is to further our understanding of the potential for renewable energy to contribute to electricity supply in Australia. This aim is achieved through the development and demonstration of methodologies for estimating potential electricity production from key renewable energy resources. The study demonstrates how methodologies for assessing the potential contribution of key renewable energy resources to electricity supply in Australia can be developed utilising a spatial assessment of important resource variables within the context of plausible utilisation of renewable energy resources. A literature review provides the basis for an assessment of the current state of knowledge regarding the use of renewable energy for electricity supply in Australia. The range of different renewable energy technologies is canvassed, brief descriptions of the technologies are presented and an appraisal is made of their commercial development status. The extent to which different renewable energy technologies have been utilised for electricity supply in Australia and prospects for near-future developments are described. Scenario analysis is used to provide insights into future development paths for renewable energy. This assists in the identification of key renewable energy technologies that will be examined in more detail and it helps in the setting of parameters for assessments of these technologies. Three scenarios are presented and these provide a framework for an analysis of possible contributions by renewable energy to electricity supply in Australia. Of those technologies that could potentially make significant contributions to electricity supply in the near term, utility scale wind energy, domestic rooftop photovoltaics (rooftop BIPV) and domestic solar hot water (SHW) stand out as being key technologies where further research in relation to resource assessment would be beneficial. The dispersed nature of the resource bases utilised by these technologies has made it difficult to assess how much electricity they could generate or displace. Conventional methods of assessing electricity generation or displacement, based upon project or site-specific analyses, have not proven amenable to analyses of the total amount of electricity that could be generated or displaced by these technologies throughout Australia. Therefore, alternative methods for assessing the potential of these technologies are needed. New models for analysing wind, BIPV and SHW performance are developed in this study. These models demonstrate the application of Geographical Information Systems (GIS) for wind, BIPV and SHW resource mapping. Wind energy maps for Australia are created showing actual wind speeds suitable for use at elevations appropriate for wind turbines. These maps represent significant advances over traditional wind atlases used in other nations due to their presentation of estimated actual wind speeds, rather than isovent lines for idealised wind speed gradients. The use of GIS for analysing BIPV and SHW resources also represents a significant departure from traditional modelling processes and demonstrates a means of overcoming important limitations of existing BIPV and SHW evaluation tools. The wind, BIPV and SHW resource mapping processes that have been developed and applied in this study show how broad-area assessments of electricity supply or displacement can be produced for technologies where spatial variations in key performance attributes constrain the use of traditional modelling processes.

Thesis (M.S.M.E)--Baylor University, 2009. / Includes bibliographical references (p. 133-134).

Electric hot water tanks play a pivotal role as demand response assets within the UK's energy system by storing heat when energy is inexpensive and delivering domestic hot water when it is required. This role will become increasingly important if non-dispatchable renewable energy sources are to play a bigger part in the energy mix. Historically, the design standards relating to hot water tanks have focused primarily on minimising heat losses. However, in addition to preserving energy, a hot water tank should preserve the availability of heat above a useful temperature for as long as possible to avoid energy usage during peak times when it is costly or carbon intensive. To do this, thermal stratification within hot water tanks must be promoted. Unfortunately, thermal stratification leads to conditions that are conducive to bacterial growth due to the hospitable temperatures that arise during operation. For this reason, question marks have arisen over the extent to which more flexible control strategies, designed to allow for increasing penetrations of intermittent renewable energy sources, might lead to the growth of pathogenic bacteria within hot water tanks. The objective of the work discussed in this thesis was to understand the extent to which there is a conflict between thermal stratification and bacterial growth in practice, whether this conflict can be resolved and the potential implications for electric hot water tanks operating on a time of use tariff. A small field study demonstrated that there is prolific bacterial growth within conventional electric cylinders and that this can be attributed to thermal stratification with a confidence of (P<0.01). Fitting a de-stratification pump, to enhance sanitary performance, resulted in a 19% decrease in the recovery of useable hot water above 43°C. Given that the tanks tested during the field study were made of copper, the consequences of alternative material choices on thermal performance were explored. It was found that the rate of useable hot water loss, due to de-stratification associated with thermal diffusion across the thermocline, could be reduced by a factor of 2.7 by making the tank liner wall from stainless steel instead of copper. Further numerical work indicated that this improvement in stratifying performance was most significant for small tanks with high aspect ratios. In addition to de-stratification that arises due to vertical conduction, de-stratification due to inlet mixing was reduced by up to 30% by installing a spiral diffuser into the base of a test cylinder. In addition, by lowering the immersion heating element to ensure there is sufficient heat transfer to the base of the cylinder, sterilising temperatures could be attained throughout the stored volume of water in the tank during heating. This showed that the conflict between thermal and sanitary performance within electric tanks could potentially be resolved. A bespoke tank, made from stainless steel and fitted with a diffuser, was built and subjected to typical draw cycles that reflect real world operation. These tests showed that more useable hot water could be delivered in comparison to a commercial off the shelf copper tank and consequently the utilisation of the Economy 7 time of use tariff would be enhanced.

Thesis (MTech(Electrical Engineering)) -- Cape Peninsula University of Technology, 2014 / Today the building energy modeling industry is facing a number of challenges, the advanced programs or methods developed for building energy modeling, are very technical and complex to be used, especially for earlier designs, and the easy programs or methods are not accurate. Moreover, more than a hundred programs developed for energy modeling, have been used in the same building, but most of the time the results differed by about 30%. That is why this thesis has developed a new building energy model in System Modeling Language (SysML), in order to meet, at the same time, the accuracy and the simplicity to be used for future and existing buildings. In this thesis, SysML has been used to develop an energy model and to set up an automation system to the existing building. SysML can do more than simulations, but this thesis is limited to only the simulations steps by using easy applications of SysML and fewer diagrams which could develop in a complete building energy model. SysML is the extension of Unified modeling Language (UML), which uses fewer diagrams than UML. SysML is simple, open and more flexible to be used in any Engineering System. The previous chapter describes SysML and gives the overview and the platform of SysML. The simulations of SysML in this project have been developed through Enterprise Architect and Mat lab software. The inputs used to simulate the program are the parameters of the existing building chosen for modeling that is a student residential building complex located in Stellenbosch, Western Cape in South Africa. Automation system program used in this thesis was based on the norms and building standards of South Africa, renewable energy and the requirements of the buildings’ occupants, in order to meet energy efficiency and safety of the occupants.

Orientador: José Antonio Siqueira Dias / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-16T16:32:34Z (GMT). No. of bitstreams: 1 Florio_JoaoLuiz_M.pdf: 3876077 bytes, checksum: 656fc1412001c5a7dcda51118870e94a (MD5) Previous issue date: 2010 / Resumo: Mais de 90% dos sistemas de aquecimento de água por energia solar instalados no Brasil (número superior a 700.00 instalações) são do tipo convencional por circulação passiva. Esse tipo de instalação apresenta boa performance, aliada à simplicidade de funcionamento. Considerando-se que aproximadamente 8% da energia consumida em nosso país é para o aquecimento de água residencial, trata-se de uma excelente alternativa ecológica de economia de energia. Em períodos de baixa insolação, o usuário pode contar com um aquecimento auxiliar através de um resistor instalado no interior do reservatório (boiler).Nesta situação a temperatura da água até atingir o valor de desligamento do termostato de segurança do sistema.Não havendo o acompanhamento da temperatura, o sistema entra num regime de funcionamento de sucessivos períodos e aquecimento e resfriamento (por perdas de calor), até que o usuário lembre-se de desligar o disjuntor. Este trabalho apresenta uma solução economicamente viável de se melhorar essa situação, fazendo-se uso da eletrônica microcontrolada. Assim, pode-se monitorar o aquecimento da água pelo resistor auxiliar através de sensores do tipo NTC, propiciando uma economia de até 25% na conta mensal, além de outras comodidades. Possuindo três modos de operação : temporizado (atua como timer), termostato (termostato ajustável pelo painel) e programado (o usuário determina o momento de uso e a temperatura desejada da água) , o sistema é constituído por console de controle e unidade de potência. O sistema é de fácil instalação, constituindo uma alternativa viável para se melhorar significativamente a performance dos sistemas atuais / Abstract: Over 90% of heating water by solar energy installed in Brazil today (more than 700,000 facilities ) are of the conventional type passive thermosyphon. This type of installation has good performance and the simplicity of operation. Considering that approximately 8% of energy consumed in our country is for heating domestic water, this is an excellent alternative of ecological energy saving. In periods of low insolation, the user can rely on an auxiliary heating through a resistor installed inside the tank (boiler), powered through a circuit breaker. In this situation, with no one monitoring , the water temperature rises until it reaches the value of shutting down the thermostat's security system, which in most cases is set at 55 ° C. Without the monitoring of temperature, the system enters a regime of operation of successive periods of heating and cooling (for heat loss), until the user remember to turn off the breaker. This paper presents an economically viable solution to improve that, by making use of electronics microcontroller. Thus, one can monitor the water heating aid through the resistor sensor NTC, providing savings of up to 25% on the monthly bill, and other amenities. With three modes of operation: timer (operates as a timer), thermostat (panel adjustable thermostat ) and programmed (the user determines the time of use and temperature of the water), the system consists of the control console and power unit. The system is easy to install, providing a viable alternative to significantly improve the performance of current systems / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica

O presente estudo teve por objetivo avaliar a qualidade de painéis de partículas de média densidade (MDP), manufaturados a partir de bagaço de cana-de-açúcar e bambu (Dendrocalamus asper). A massa específica nominal foi 0,65 g.cm-3 e utilizou-se adesivo à base de uréia-formaldeído. O delineamento consistiu em 16 tratamentos, divididos em quatro Experimentos. Foram avaliadas as propriedades físicas (Massa Específica Aparente - MEA, Absorção de Água - AA, Inchamento em Espessura - IE e Taxa de Não-Retorno em Espessura - TNRE), mecânicas (Flexão Estática - MoR e MoE, Arrancamento de Parafuso de Superficie e Topo - APS e APT e Ligação Interna - LI, além do Perfil de Densidade, Molhabilidade e Resistência Natural. Os objetivos foram: I - Avaliar painéis de partículas de bagaço de cana com duas granulometrias (0,50 mm e 0,85 mm), tratadas e não tratadas em água quente; II - Avaliar os painéis adotando as mesmas variáveis do experimento anterior, porém, empregando partículas de bambu; III - Avaliar os painéis gerados a partir da mistura de ambos materiais nas proporções de 100%, 75%, 50%, 25% e 0%; IV - Avaliar os painéis constituídos com partículas termorretificadas de bagaço e bambu encoladas com três teores de adesivo (10, 12 e 14%). Os resultados do Experimento I mostraram que propriedades físicas (IE2h, IE24h, AA24h e TNRE), mecânicas (MoR, MoE, APS, APT e LI) e molhabilidade não foram influenciadas pelos fatores (granulometria e condição de partículas). Os fatores influenciaram de forma interativa o perfil de densidade de massa específica aparente da camada externa. A resistência natural foi influenciada pelos fatores e os painéis foram inclusos na categoria \"resistência moderada\". Os resultados do Experimento II mostraram que as partículas tratadas em água quente resultaram em aumento significativo dos valores de IE2h, IE24h e TNRE. O APS, APT e LI apresentaram melhorias significativas para os painéis manufaturados com partículas tratadas em água quente. Os fatores avaliados influenciaram a massa específica aparente da camada externa dos painéis. Houve interação significativa entre os fatores para o ângulo inicial obtido com água. O fungo G. trabeum causou maiores perdas de massa nos painéis constituídos com partículas tratadas em água quente e o T. versicolor evidenciou maior índice de ataque em chapas confeccionadas com partículas controle. No Experimento III o aumento da razão de compactação apresentou tendência significativa de aumento de valores da AA24h, IE2h, IE24h e TNRE, além do MoR. Tal variável reduziu a AA2h, APT e LI, proporcionou picos mais acentuados de massa específica nas faces dos painéis, reduziu significativamente a molhabilidade e aumentou a perda de massa dos painéis submetidos aos fungos P. placenta e G. trabeum. No Experimento IV o tratamento térmico promoveu melhorias significativas para AA2h, AA24h, IE2h e IE24h, porém reduziu o MoR, MoE, APS, APT e LI, que foram melhoradas com o aumento no teor de adesivo, além do perfil de densidade. Não houve influência significativa na molhabilidade, comparando os painéis com mesmo teor de adesivo e nem considerando diferentes teores de adesivo. De forma geral, os painéis apresentaram melhorias significativas na resistência biológica com a termorretificação e aumento no teor de adesivo. Bagaço de cana-de-açúcar e bambu representam boas alternativas de matérias-primas para confecção de chapas aglomeradas. Os painéis podem ser utilizados para forros, isolamento térmico e acústico, revestimentos, painéis decorativos, componentes para construção civil, substrato para piso, embalagens, pequenos objetos entre outras aplicações. / The aiming of this study was to evaluate the quality of medium density particleboard (MDP) manufactured with particles of sugarcane bagasse and bamboo with nominal density of 0.65 g.cm-3 and urea-formaldehyde adhesive. The experimental design was composed of 16 treatments divided in four experiments. The physical properties (apparent density, water absorption, thickness swelling and the nonrecoverable tax, mechanical (static bending - modulus of elasticity and modulus of rupture, screw withdrawal strength and internal bonding) were evaluated, as well as the density profile, wettability and natural resistance. The objectives were: I - To evaluate panels of sugarcane bagasse particles with two granulometries (0.50 mm and 0.85 mm) treated and not treated in hot water; II - To evaluate the panels using the same variables of the previous experiment, however using bamboo particles; III - Evaluate the panels origin from the mixture of both materials in proportions of 100%, 75%, 50%, 25% and 0%; IV - Evaluate the panels constituted with heat treatment particles of bamboo and bagasse and glued with three adhesive contents (10, 12 and 14%). The results of the Experiment I showed that physical (IE2h, IE24h, AA24h and TNRE) and mechanical properties (MoR, MoE, APS, APT and LI) and wettability were not influenced by the factors (grain size and particle condition). The factors influenced the apparent specific bulk density profile of the outer layer. Natural resistance was influenced by the factors and the panels were included in the \"moderate resistance\" category. The results of Experiment II showed that the particles treated in hot water resulted in a significant increase in the values of IE2h, IE24h and TNRE. APS, APT and LI showed significant improvements for panels manufactured with hot water treated particles. The evaluated factors influenced the apparent specific mass of the outer layer of the panels. There was a significant interaction between the factors for the initial angle obtained with water. The G. trabeum fungus caused greater mass losses in the panels constituted with particles treated in hot water and T. versicolor evidenced a higher attack rate in plates made with control particles. In Experiment III the increase in compaction ratio showed a significant tendency to increase values of AA24h, IE2h, IE24h and TNRE, in addition to MoR. This variable reduced AA2h, APT and LI, provided more pronounced peaks of specific mass in the faces of the panels, significantly reduced wettability and increased the mass loss of the panels submitted to P. placenta and G. trabeum fungi. In Experiment IV the heat treatment promoted significant improvements for AA2h, AA24h, IE2h and IE24h, but reduced MoR, MoE, APS, APT and LI, which were improved with the increase of the adhesive content, as well as the density profile. There was no significant influence on wettability, comparing the panels with the same adhesive content and different adhesive contents. In general, the panels showed significant improvements in the biological resistance with thermortification and increase in the adhesive content. Sugarcane bagasse and bamboo represent good alternatives of raw materials for confection of agglomerated sheets. The panels can be used for linings, thermal and acoustic insulation, coatings, decorative panels, components for civil construction, substrate for flooring, packaging small objects among other applications.

A conceptual end use model for residential water demand and return flow is presented in this thesis. The model requires a unique description of a single residential stand in terms of all its end-uses. The end-uses include toilet flushing, bathing and showering, garden watering, leaks, et cetera. Various parameters describe each of the end-uses. The model predicts five components relating to water demand and wastewater flow at a residence: indoor water demand, outdoor water demand, hot water demand, wastewater flow volume and concentration of solutes in the wastewater. Twelve monthly results are calculated, for each of the five components, to provide a typical seasonal pattern as well as an annual value. The large number of input parameters in an end-use model allows for powerful and detailed analysis. The parameters required to populate the model are discussed and guideline values are presented. The end-use model is used to conduct a sensitivity analysis of each independent parameter for each of the five individual model components. The elasticity and sensitivity is determined at a base point with respect to each parameter for all five results. A research significance index is also devised to integrate the elasticity and availability of data for each parameter. The result is a prioritised list of the most critical parameters for each of the five components, which are the ones that should receive the focus for future study and data recording. The parameters are combined to obtain a list of the overall most important parameters in the model for all components combined, and based on a combination of the elasticity-based rank and the sensitivity based rank. The five most important parameters are the household size, toilet flush frequency, toilet flush volume, the washing machine event frequency and the volume of leaks on a stand. The practical application of the model is illustrated. The researchers first apply the model to mimic a few commonly accepted characteristics of water demand. The effectiveness of some specific water demand management measures are evaluated by adjusting selected model parameters. The measures include xeriscaping, the installation of dual-flush toilets, low-flow showerheads, pool ownership and pool cover use. The model also enables practitioners to obtain an insight into the water use habits of homeowners. The model forms the basis for further research work in the field. Its relatively simple structure and realistic data requirement encourages its integration into existing commercially available software suites for water and sewer system analysis and -management in the civil engineering industry in South Africa, as well as abroad. / Prof. J. Haarhoff