Dissertations / Theses on the topic 'Electric water heater'

Today's utilities face new challenges due to the continually increasing penetration of residential solar and other distributed, stochastic generation sources. In order to maintain balance and stability in the grid without building costly, large-scale generation plants, utilities are turning to distributed energy resources for use in demand response programs. Demand response is a cost-efficient way to balance grid load/generation without the need for increased capital investment in traditional generation resources. Demand response programs are excellent exploiters of end-user devices that otherwise further accentuate the daily load curve and thus, add to the difficulties created by daily load peaks. Electric water heaters are excellent candidates for use in demand response programs for a variety of reason. One, electric water heaters represent a large portion of daily household loads due to their high nominal power ratings (1.5 kW - 5.5kW), and frequent use estimated to account for approximately one third of all daily residential power demand. Two, they are composed of strictly resistive elements, which greatly simplifies modeling, aggregation and control. And third, they can be used for load "shedding" during periods of high electrical demand as well as load "absorbing" during periods of excess generation due to their thermal storage capabilities. With improved access and control, electric water heaters could become a major distributed energy resource for utilities. In order to properly control and use a distributed energy resource, it is important to know how these resources operate and their patterns of behavior in different environments. This thesis presents a single-element, single mass electric water heater model for analyzing the effectiveness of using electric water heaters as distributed energy resources and for participation in demand response programs. The CTA-2045 communication protocol was used for testing demand response signals. The electric water heater is modeled in Python and the communication pathway was built in C++ and Python.

In this research, the impact of solar thermal water heaters on the electric water heating load curve in a residential distribution circuit is analyzed with realistic hot water draw profiles. For this purpose, the electric and solar thermal water heater models are developed in MATLAB and validated with results from GridLAB-D and TRNSYS respectively. The solar thermal water heater model is developed for two types of collectors namely the flat plate and evacuated glass tube collector. Simulations are performed with the climate data from two cities - Madison, WI and Tampa, FL - which belong to two very different climate zones in the United States. Minute-by-minute electric energy consumptions in all three configurations of water heaters are modeled for a single water heater as well as a residential distribution circuit with 100 water heaters for daily as well as monthly time frames.<p> The research findings include:<ol><li> The electric energy saving potential of a solar thermal water heater powered by auxiliary electric element is in the range of 40-80% as compared to an all-electric water heater depending on the site conditions such as ambient temperature, sunshine and wind speed. The simulation results indicate that the energy saving potential of a solar thermal water heater is in the range of 40-70% during winter and 60-80% during summer. </li><li>Solar thermal water heaters aid in reducing the peak demand for electric water heating in a distribution feeder during sunshine hours when ambient temperatures are higher. The simulation results indicate that the peak reduction potential of solar thermal water heaters in a residential distribution feeder is in the range of 25-40% during winter and 40-60% during summer. </li><li>The evacuated glass tube collectors save an additional 7-10% electric energy compared to the flat plate collectors with one glass pane during winter and around 10-15% during summer. The additional savings result from the capability of glass tube collectors to absorb ground reflected radiation and diffuse as well as direct beam radiation for a wider range of incidence angles. Also, the evacuated glass tube structure helps in reducing wind convective losses. </li><li>From the simulations performed for Madison, WI and Tampa, FL, it is observed that Tampa, FL experiences more energy savings in winter than Madison, WI, while the energy savings are almost the same in summer. This is due to the fact that Tampa, FL has warmer winters with higher ambient temperatures and longer sunshine hours during the day compared to Madison, WI while the summer temperatures and sunshine hours are almost the same for the two cities. </li><li>As expected, the simulation results prove the fact that lowering the hot water temperature set point will result in the reduction of electricity consumption. For a temperature reduction from 120 deg. F to 110 deg. F, electric water heaters save about 25-35% electric energy whereas solar thermal water heaters save about 30-40% auxiliary electric energy for the same temperature reduction. </li><li>For the flat plate collectors, glass panes play an important role in auxiliary electric energy consumption. Flat plate collectors with two glass panes save about 10-15% auxiliary electric energy compared to those with no glass panes and about 3-5% energy saving compared to collectors with one glass pane. This is because there are reduced wind convective losses with glass panes. However, there are also transmittance losses from glass panes and there are upper limits on how many glass panes can be used.</li></ol> Results and findings from this research provide valuable insight into the benefits of solar thermal water heaters in a residential distribution feeder, which include the energy savings and peak demand reduction.<br>Master of Science

Este trabalho propõe um método com objetivo de avaliar a eficiência energética de aquecedores de água residenciais de acumulação elétricos. Os aquecedores foram submetidos a um ciclo de operação simulando uma condição de uso para o cálculo da eficiência. Este ciclo de duração de um dia é composto pelas fases: produção de água quente, reaquecimento e manutenção da temperatura interna. O método foi aplicado no programa experimental e permitiu a identificação de diversos parâmetros referentes ao funcionamento dos aquecedores, tais como: perda passiva por 24 horas, produção de água quente, tempo de reaquecimento, variação da temperatura interna da água e a sua eficiência energética.<br>This work proposes a method with objective of evaluating the energy efficiency of electrical residential storage water heaters. The heaters were submitted to an operation cycle simulating a use condition for the calculation of the efficiency. This cycle with duration of one day is composed by the phases: hot water withdrawal, temperature recovery and standby thermal loss. The method was applied in the experimental program and it allowed the identification of several parameters regarding the operation of such heaters as: standby thermal loss per 24 hours, hot water rate output, reheating time, cyclic variation of the temperature and its energy efficiency.

Alors que le secteur du bâtiment se montre de plus en plus économe en énergie, les besoins en eau chaude sanitaire (ECS) augmentent, en particulier dans les logements récents. De ce fait, il apparait nécessaire d'améliorer l'efficacité des solutions mises en œuvre pour la production d'ECS, de mieux comprendre les besoins en ECS et d'impliquer l'usager dans la prise de décision. Le projet traite du développement d'algorithmes pour le contrôle/commande « intelligent » d'installations associant chauffe-eau électrique et panneaux solaires photovoltaïques en autoconsommation. Sera mise en œuvre une stratégie fondée sur la théorie de la commande prédictive, mettant à profit les outils de l'apprentissage automatique. Cette stratégie sera généralisée aux systèmes « multi-chauffe-eau », mutualisant une production solaire photovoltaïque, parle développement d'une commande distribuée et hiérarchisée. Une expérimentation permettra d'évaluer les conditions d'acceptabilité de la solution développée et l'impact de l'information sur la prise de décision<br>While the building sector is increasingly energy efficient, the needs in domestic hot water (DHW) is increasing, especially in newer homes. Therefore, improvement of efficiency in the production of DHW, a better understanding of the needs in DHW, and user involvement in the decision-making process are necessary. The project deals with the development of algorithms for the smart control of combined electric water heaters and self-consumption photovoltaic solar panels. A model-based predictive control strategy will be developed and implemented, leveraging machine learning tools. The strategy will be generalized to multi-water heater systems, sharing photovoltaic solar production, through the development of a distributed and hierarchical control approach. An experiment will make it possible to assess the conditions of acceptability of the developed solution and the impact of information on decision-making

The main aim of my project is to develop a hardware implementation of the electronic waterheater by choosing different components and minimize the errors in the same. I have consideredseveral options depending on the availability of components, cost, reliability, implementation,financial budget, specification and thinking about the professional technical skills required. Inthis project I designed and implemented, an AVR micro controller based water temperaturemeasurement system using Atmega328p microcontroller.The idea of the project came from a company called Relek production AB, Sweden and theydevelop and supply electrical equipment for heating: such as electric boilers, under floor heatingboilers, IR heaters, emergency power plants, power monitors, etc. Now they want to develop anew version of electronic water heater and according to their specification.The microcontroller (Atmega328p) based temperature control system is used in this project forproviding better functioning of the system and will also serve the following purposes.1) As there will be less usage of energy as it is more energy efficient.2) The microcontroller along with temperature sensor decides when the heater shouldturn on/off.With this project I have designed the schematic diagram by using Eagle Autodesk PCB CADprogram. The seven-segment display is used in this project to show the current temperature. Atemperature sensor (LM35) is used in this project to sense the temperature and give thesemeasured values to the microcontroller. The temperature measurement and heater control areprocessed using C++ program.I have connected the circuit as per the schematic diagram and programed the microcontroller,interfacing all the major components like 7 segment display, temperature sensor, 2 pushbuttons(for manually incrementing and decrementing the set point in the program), and optoisolator (tosense the output from microcontroller and control the heater through thyristor).

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.

Distributed energy resources like residential electric water heaters and residential battery inverter systems offer a small amount of change to the grid individually. When aggregated however, these assets can cause major effects to the electric grid. Aggregating these resources allows them to take on generator-like functions with the ability to increment power and decrement power. The Western Energy Imbalance Market is an energy market offering 15 minute and 5 minute markets for energy transactions between balancing areas. Generation assets make increment and decrement bids. Traditionally the only entrants to this market have been large scale generators and large scale assets legally designated as generators. Aggregated distributed resources could offer the same increments and decrements from managing residential assets like electric water heaters and batteries. DERAS, a Distributed Energy Resource Aggregation System developed by the Portland State Power Lab group, is an aggregator of residential resources that could offer increment and decrement bids to an energy market, like an Energy Imbalance Market. This research models and simulates aggregations of distributed energy resources. This work analyzes the effects of 10,000 electric water heaters and 10,000 battery inverter systems. A simulation program was built to simulate regular use of these assets, and then add the additional effects of a decrement bid into the Western Energy Imbalance Market. The effects of the bids on energy levels inside the water heaters and batteries are examined. The power imported from the grid is also analyzed as an effect of the aggregator attempting to cover a generation decrement bid.

The Water To Air heater (WTA) is a component that heats the interior and the engine of the truck by heating coolant through a combustion of diesel fuel. It is vital that the Water To Air heater is primed with fuel prior to using it in order for it to start when desired. Priming of the heater is done in production, which is where the trucks are built. This is done to ensure that there is fuel available to heat the coolant. However, the current priming process has too many weaknesses, it is sensitive to component changes and there are a number of uncertainties present. The goal of this thesis is to investigate the priming process and try to improve the process so that it becomes more robust. The aim is to present an alternate method that could be used to minimize the number of uncertainties and the impact of these. Several methods of how to regulate the fuel supply were studied and evaluated according to a few criteria and limitations. The first method that was tested was to try and detect fuel through a simple type of Electrical Capacitance Tomography. However, initial measurements proved that it would not be possible to use this method in order to achieve the desired result. Instead, fuel was detected by creating a prototype consisting of a photoresistor and a laser pointer. Once it had been established that fuel could be detected through this prototype, a microcontroller was programmed to automatically be able to make measurements and handle the output from the photoresistor. The developed concept is a concept that, if implemented in production, would solve many of the problems that are present with the current priming process. Many of the uncertainties would either be eliminated completely, or decreased massively. However, there is some work that remains. In order to use the proposed solution as a stand-alone system that regulates the fuel supply, it is necessary that a stop signal is implemented. Additional tests need to be performed in order to decide how the final implementation is going to work. Finally, the prototype needs some improvements.<br>Extravärmaren (WTA) är en komponent som värmer både lastbilens hytt och motor genom förbränning av diesel. För att extravärmaren ska starta enligt önskemål så är det viktigt att bränsleslangarna fylls med diesel. Detta är gjort i produktion, vilket är där lastbilarna byggs, för att försäkra sig om att extravärmaren fungerar som den ska. Processen där bränsleslangarna fylls har dock allt för många svagheter, den är känslig mot ändringar av komponenter och det finns även ett antal osäkerheter närvarande. Syftet med detta examensarbete är att undersöka denna process och försöka förbättra processen så att den blir stabilare. Målet är att presentera en mer robust metod, som minimerar mängden och signifikansen av osäkerheter, för att fylla bränsleslangarna. Flera metoder för att kontrollera bränsletillförseln studerades och utvärderades utifrån ett antal kriterier och begränsningar. Den första metoden som testades var att försöka upptäcka bränsle genom att använda en enkel variant av elektrisk kapacitanstomografi. Initiala mätningar visade dock att det inte var möjligt att använda denna metod för att uppnå det önskade resultatet. Istället användes en prototyp bestående av en fotoresistor och en laserpekare för att upptäcka bränslet. När det hade fastställts att bränsle kunde upptäckas på detta sätt så programmerades en mikrokontroller för att automatiskt kunna läsa av och hantera resultatet från fotoresistorn. Det utvecklade konceptet skulle, om det implementeras i produktion, lösa många av de problem som är närvarande under den nuvarande processen. Många av osäkerheterna skulle antingen elimineras helt, eller reduceras tydligt. För att konceptet ska kunna implementeras i produktion krävs det dock framtida arbete. För att kunna använda den föreslagna lösningen som ett fristående system så krävs det att en stopsignal implementeras. Fler tester behöver utföras för att kunna avgöra hur den slutgiltiga lösningen skall fungera. Till sist så behöver prototypen vidareutvecklas.

Includes bibliographical references.<br>In our quest to use more renewable energy to reduce our dependence on non-renewable fuels man has been harnessing wind, solar and hydro energy for many years. While hydo and solar energy are well established, it is only during the last decade that serious progress in wind energy has been made. Solar energy is widely used for water or space heating while wind is used for pumping water for remote areas. This project looks into the design and development of a 6kW wind powered water heating unit.

This master thesis presents a new technological combination of two environmentally friendly sources of energy in order to provide DHW, and space heating. Solar energy is used for space heating, and DHW production using PV modules which supply direct current directly to electrical heating elements inside a water storage tank. On the other hand a GSHP system as another source of renewable energy provides heat in the water storage tank of the system in order to provide DHW and space heating. These two sources of renewable energy have been combined in this case-study in order to obtain a more efficient system, which will reduce the amount of electricity consumed by the GSHP system.The key aim of this study is to make simulations, and calculations of the amount ofelectrical energy that can be expected to be produced by a certain amount of PV modules that are already assembled on a house in Vantaa, southern Finland. This energy is then intended to be used as a complement to produce hot water in the heating system of the house beside the original GSHP system. Thus the amount of electrical energy purchased from the grid should be reduced and the compressor in the GSHP would need fewer starts which would reduce the heating cost of the GSHP system for space heating and providing hot water.The produced energy by the PV arrays in three different circuits will be charged directly to three electrical heating elements in the water storage tank of the existing system to satisfy the demand of the heating elements. The excess energy can be used to heat the water in the water storage tank to some extent which leads to a reduction of electricity consumption by the different components of the GSHP system.To increase the efficiency of the existing hybrid system, optimization of different PV configurations have been accomplished, and the results are compared. Optimization of the arrays in southern and western walls shows a DC power increase of 298 kWh/year compared with the existing PV configurations. Comparing the results from the optimization of the arrays on the western roof if the intention is to feed AC power to the components of the GSHP system shows a yearly AC power production of 1,646 kWh.This is with the consideration of no overproduction by the PV modules during the summer months. This means the optimized PV systems will be able to cover a larger part of summer demand compared with the existing system.

The purpose of the work described here has been to seek methods of narrowing the present gap between currently realised heat pump performance and the theoretical limit. The single most important pre-requisite to this objective is the identification and quantitative assessment of the various non-idealities and degradative phenomena responsible for the present shortfall. The use of availability analysis has been introduced as a diagnostic tool, and applied to a few very simple, highly idealised Rankine cycle optimisation problems. From this work, it has been demonstrated that the scope for improvement through optimisation is small in comparison with the extensive potential for improvement by reducing the compressor's losses. A fully instrumented heat pump was assembled and extensively tested. This furnished performance data, and led to an improved understanding of the systems behaviour. From a very simple analysis of the resulting compressor performance data, confirmation of the compressor's low efficiency was obtained. In addition, in order to obtain experimental data concerning specific details of the heat pump's operation, several novel experiments were performed. The experimental work was concluded with a set of tests which attempted to obtain definitive performance data for a small set of discrete operating conditions. These tests included an investigation of the effect of two compressor modifications. The resulting performance data was analysed by a sophisticated calculation which used that measurements to quantify each dagradative phenomenon occurring in that compressor, and so indicate where the greatest potential for improvement lies. Finally, in the light of everything that was learnt, specific technical suggestions have been made, to reduce the losses associated with both the refrigerant circuit and the compressor.

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&LT;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&deg;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.

The majority of electrical energy in the United States is produced by fossil fuels, which release harmful greenhouse gas emissions and are non-renewable resources. The U.S. Department of Energy has established goals for a smart electric power grid, which facilitates the incorporation of clean, renewable generation sources, such as wind. A major challenge in incorporating renewable energy sources onto the power grid is balancing their intermittent and often unpredictable nature. In addition, wind generation is typically higher at night, when consumer demand is low. Residential electric water heaters (EWHs), which currently account for 20% of the U.S. residential daily energy demand, are the largest contributors to the morning and evening peaks in residential power demand. The simulations in this thesis tested the hypothesis that controlling the thermostat setpoints of EWHs can shift EWH electrical energy demand from hours of higher demand to hours of lower demand, provide a large percentage of the balancing reserves necessary to integrate wind energy generation onto the electric power grid, and economically benefit the customer, while maintaining safe water temperatures and without significantly increasing average daily power demand or maximum power demand of the EWHs. In the experimental simulation, during on-peak hours for demand, when electricity prices are high, the thermostat setpoints of EWHs were set to the minimum, in order to consume minimal energy. The result was that the vast majority of EWH demand occurred during off-peak hours, a significant improvement over the base case (normal operation in which no setpoint control was implemented). During off-peak hours, the thermostat setpoints of EWHs were controlled by the utility in order to provide balancing reserves necessary to maintain power system stability when wind generation is included in the system. The EWHs were able to provide the balancing reserves desired by the utility a majority of the time. In this combined control method, the customer benefitted financially by saving in electrical energy costs when compared to the base case, the EWH water temperatures always remained within safe limits. There was only a small increase in the total energy consumption, but the peak power demand did not change.

The thesis has been conducted at Hetvägg AB and the aim is to develop a combined PID and Model Predictive Controller (MPC) controller for an air to water heat pump system that supplies domestic hot water (DHW) to the users. The current control system is PLC based but because of its big size and expensive maintenance it must be replaced with a robust controller for the heat pump. The main goal of this project has been to find a suitable improvement strategy. By constructing a model of the system, the control system has been evaluated. First a model of the system is derived using system identification techniques in Matlab-Simulink; since the system is nonlinear and dynamic a model of the system is needed before the controller is implemented. The data has been estimated and validated for the final selection of the model in system identification toolbox and then the controller is designed for the selected model. The combined PID and MPC controller utilizes the obtained model to predict the future behavior of the system and by changing the constraints an optimal control of the system is achieved. In this thesis work, first the PID and MPC controller are evaluated and their results are compared using transient and frequency response plots. It is seen that the MPC obtained better control action than the PID controller, after some tuning the MPC controller is capable of maintaining the outlet water temperature to the reference or set point value. Both the controllers are combined to remove the minor instabilities from the system and also to obtain a better output. From the transient response behavior it is seen that the combined MPC and PID controller delivered good output response with minimal overshoot, rise time and settling time.

This PhD involved computational fluid dynamic simulations of finned generators cooling under forced convection in an oscillating water column environment. Various design changes to the upstream Wells turbine and its effect on the consequent cooling of the generator were investigated. Simulations were run in steady-state to obtain an initial condition, thereafter, unsteady simulations revealed a steadying of heat transfer over the course of multiple blade rotation cycles. This justified the use of steady-state for the remaining simulations over a range of flow coefficients. The results revealed that the heat transfer from the generator increased for tighter blade tip clearances, thicker blade profiles and greater turbine solidity. The heat transfer was found to increase with rising flow rate coefficient, which was adjusted by increasing the inlet velocity whilst maintaining the angular velocity of the turbine at a constant 2000 RPM. Additionally, the variation of turbine angular velocity at a fixed flow rate coefficient was investigated, the heat transfer was also found to increase with angular velocity, albeit by a far lesser extent. The inclusion of the Wells turbine upstream of the generator was investigated initially and was found to increase heat transfer due to the resulting impingement of airflow across the generator. In all design scenarios in which the heat transfer increases, there is also an observed increase in the mass flow rate of air, radially, towards the generator.

A modeling demonstration of the moderation of 14.1 MeV primary neutrons in beryllium emitted from a D-T fusion nuclear reaction. The energy deposited from neutron-beryllium interactions which produces heat in the blanket of a fusion tokamak. A review of literature and data available for neutron-beryllium interactions is provided to support the MC software of a simplified model of the ITER first wall and blanket. Energy deposited in regions of the model using FLUKA are used to calculate a polynomial heat flux profile through the model. One dimensional conductive heat transfer through the model is performed and the cooling capacity of the coolant channels via convective heat transfer is explored.

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.

Orientador: Marina Sangoi de Oliveira Ilha<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo<br>Made available in DSpace on 2018-08-16T20:54:27Z (GMT). No. of bitstreams: 1 Ribeiro_MariliaFerraz_M.pdf: 7377703 bytes, checksum: 1e30ea2940df727adbb976b5bcd9ca4e (MD5) Previous issue date: 2010<br>Resumo: O emprego de medidas visando a conservação de água e energia elétrica vem sendo cada vez mais incentivado, dentro do conceito de sustentabilidade das edificações. O chuveiro, equipamento mais empregado para o aquecimento de água para o banho em habitações de interesse social, representa cerca de 24% do consumo de energia elétrica do setor residencial, além de ser utilizado no horário de pico do sistema elétrico, o que aumenta sobremaneira a demanda desse insumo. Alguns estudos avaliaram o impacto do emprego de sistemas de aquecimento solar em conjunto com chuveiros de potência regulável em edificações de interesse social, evidenciando a redução de consumo de energia elétrica. Há necessidade de se verificar, contudo, o impacto no consumo da água vinculado ao uso desses sistemas, pois muitas vezes o pensamento relacionado ao "aquecimento gratuito" pode conduzir a um aumento do consumo de água. A conscientização das pessoas é condição imprescindível para a sua participação ativa e mudança de hábitos de consumo, em conjunto com o emprego de tecnologias economizadoras. Este trabalho apresenta um estudo desenvolvido junto a 16 habitações de interesse social localizadas em um bairro da cidade de Campinas, São Paulo. Trata-se de um estudo de caso no qual a montagem e instalação dos aquecedores solares de baixo custo (ASBC) foram efetuadas pela própria comunidade envolvida, que participou também de oficinas de sensibilização para o uso racional de água e de energia elétrica. Foram avaliados o impacto após a instalação do ASBC, a apropriação da tecnologia por seus usuários e as mudanças ocorridas nos hábitos de consumo após a participação das oficinas de sensibilização. A partir dessas análises foram propostas diretrizes e recomendações para implantação de tecnologias sociais em comunidades com as mesmas características<br>Abstract: The use of measures aiming to conserve water and energy has been increasingly encouraged, within the concept of sustainability of buildings. Shower, the equipment most used to heat water for bathing in low-income houses, represents approximately 24% of electricity consumption in the residential sector, besides being used on peak periods of the electrical system, which greatly increases demand of this input. Some studies have assessed the impact of the use of solar heating systems in conjunction with adjustable power showers in low-income houses, highlighting the reduction in power consumption. It is necessary to verify, though, the impact on water consumption linked to the use of such systems because often the thought related to the "free heating" can lead to an increase in water consumption. The awareness of people is prerequisite for their active participation and change in consumption habits, along with the use of saving technologies. This work presents a study conducted with 16 low-income houses located in a neighborhood in the city of Campinas, São Paulo. This is a case study in which the assembly and installation of low cost solar heating systems (ASBC) were carried out by the community involved, which also participated in workshops to raise awareness of the rational use of water and energy. The impact after installation of the ASBC, the appropriation of technology by its users and the changes in consumption habits after participating in the workshops to raise awareness were evaluated. From these analyses, guidelines and recommendations were established for deployment of technologies in communities with the same characteristics<br>Mestrado<br>Arquitetura e Construção<br>Mestre em Engenharia Civil

Orientador: Luiz Carlos Pereira da Silva<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação<br>Made available in DSpace on 2018-08-25T04:17:06Z (GMT). No. of bitstreams: 1 Tome_MauriciodeCastro_M.pdf: 1294997 bytes, checksum: 7f957ff745612ef36a77596912782f07 (MD5) Previous issue date: 2014<br>Resumo: O presente trabalho procura analisar o aquecimento elétrico de água no setor residencial e seu impacto no perfil de tensão, perdas e energia total acumulada. Por meio de simulações computacionais com uma rede de teste, juntamente com dados de uso dos eletrodomésticos mais comuns no ambiente residencial (separados por região, devido às diferentes condições e padrões de consumo das mesmas), foi possível estimar a quantidade de energia utilizada referente ao chuveiro elétrico, bem como o impacto no perfil de tensão e as perdas na distribuição decorrentes do uso do mesmo. Além disso, também foram analisadas as propostas de tarifação branca da ANEEL e as propostas homologadas pelas concessionárias, e seu impacto na conta de luz do consumidor residencial, para três padrões de consumo: consumo total não modificado, consumo do chuveiro deslocado e consumo do chuveiro eliminado. Na parte de impactos na rede de distribuição, confirmou-se que a utilização do chuveiro elétrico, que é praticamente uma exclusividade brasileira, representa uma parcela significativa do consumo total de uma residência, além de ser um dos maiores responsáveis pelo pico de consumo no setor residencial, o que causa um afundamento no perfil de tensão e aumento nas perdas na distribuição, características indesejadas na operação do sistema elétrico. Já na parte do consumo residencial, foi visto que os postos tarifários homologados pelas concessionárias reduzem em muito os ganhos possíveis com o deslocamento do horário de carga do chuveiro, de forma que a chance de uma adoção significativa da tarifa branca pelos consumidores é baixa. Por outro lado, uma adesão maciça dos consumidores poderia fazer com que o consumo do chuveiro fosse deslocado do horário de ponta e se concentrasse no horário imediatamente posterior, o que pode agravar a situação atual em termos de pico de consumo<br>Abstract: This thesis presents an analysis of the electricity based water heating in the Brazilian residential sector and its impacts on the electric grid voltage profile, losses and total energy consumption. Using computer simulation through a test network, and considering the most common household appliances' usage data, it was possible to estimate the total energy used by the electric shower, as well as its impact on voltage profile and distribution losses. Moreover, it is also analysed the time of use (TOU) tariff proposed by ANEEL and the consolidated tariffs proposed by the Brazilian utilities, and its impacts in the customers' energy bill, for three load patterns: unmodified, electric shower demand moved off-peak, and without electric shower. Results about the impact on distribution networks confirmed that the electric shower usage (which is almost exclusive to Brazil) represents a large amount of the electric energy used by the residential customers, and, in addition, it is a major contributor to the peak loading of the residential sector, causing voltage drop and increased distribution losses, which are undesired in electric distribution systems. In terms of household consumption, it was possible to conclude that the utilities' approved time-of-use tariffs give little margin for possible savings in the electricity bill in comparison with ANEEL's initial tariff proposal, so that TOU adoption will probably be very low. On the other hand, a massive adoption of the off-peak shower usage by the customers could cause a concentration in its usage in a later time, which would eventually worsen the actual peak hour scenario<br>Mestrado<br>Energia Eletrica<br>Mestre em Engenharia Elétrica

Two-phase spray cooling has been an emerging thermal management technique offering high heat transfer coefficients and critical heat flux levels, near-uniform surface temperatures, and efficient coolant usage that enables to design of compact and lightweight systems. Due to these capabilities, spray cooling is a promising approach for high heat flux applications in computing, power electronics, and optics. Two-phase spray cooling inherently depends on saturation temperature-pressure relationships of the working fluid to take advantage of high heat transfer rates associated with liquid-vapor phase change. When a certain application requires strict temperature and/or pressure conditions, thermo-physical properties of the working fluid play a critical role in attaining proper efficiency, reliability, or packaging structure. However, some of the commonly used single-component working fluids have relatively poor properties and heat transfer performance. For example, water is the best coolant in terms of properties, yet in certain applications where the system operates at low temperature ambient, it cannot be implemented due to freezing risk. The common solution for this problem is to use the antifreeze mixtures (binary mixtures of water and alcohol) to reduce the freezing point. In such cases, utilizing binary mixtures to tune working fluid properties becomes an alternative approach. This study has two main objectives; (1) to experimentally investigate the two-phase spray cooling performance of water/2-propanol binary mixture, and (2) to numerically investigate the performance of an advanced heat spreader featuring high and directional thermal conductivity materials for high heat flux focal sources. The first part of the study involves experimental characterization of heat transfer performance. Tests are conducted on a small-scale, closed loop spray cooling system featuring a pressure atomized spray nozzle. The test section, made of copper, measures 10 mm x 10 mm x 2 mm with a plain, smooth surface. A cylindrical copper block, with a matching size square protrusion attached onto the back side of the test section, generates heat using cartridge heaters and simulates high heat flux source. Embedded thermocouples are used to determine the spray surface temperature. The working fluid, water/alcohol mixture, has various concentration levels of 2-propanol by mass fraction 0.0 (pure water), 0.25, 0.50, 0.879 (azeotrope) and 1.0 (pure alcohol)), representing both non-azeotropic and azeotropic cases. Spray cooling tests are performed with a constant flow rate of 5.6 ml/cm².s at subcooled temperatures (~20oC) and atmospheric pressure. Experimental procedure involves controlling the heat flux in increasing steps, and recording the corresponding steady-state temperatures to obtain cooling curves in the form of surface superheat vs. heat flux. The second part of the study investigates an advanced heat spreader design for thermal management of a high heat flux focal source. The heat spreader comprises of three layers: a copper layer that interfaces with the heat source, a high and directional thermal conductivity material (such as CVD diamond and Pyrolytic graphite) layer, and another copper layer that is exposed to two-phase spray cooling. The analysis applies various heat fluxes on the heat source side and the experimentally obtained heat transfer coefficients on the spray side of the spreader design to determine the temperature and heat flux distributions, and examine the potential capabilities of this configuration.

This diploma thesis focuses on the design of heating and hot water reservoir in an apartment complex. For three variants of heat sources (gas condensing boiler, heat pump and electric boiler) is evaluated their economic profitability for heating and hot water heating. For the best selected heat sources is drawn up the technical solution of heating in the apartment complex.

The aim of this diploma thesis is to find a solution of heating system, a hot water preparation and a subsequent design of the heat source for the apartment building. The project consists of a calculation of heat losses, a design of radiators, a dimensioning of pipes and a design of two options of the heat source for heating and hot water preparation. The first option of the heat source I chose a pellet boiler and the second option is an electric boiler with solar collectors for the preparation of hot water. The introductory part deals with analysis of this object and emission limits of heat source using different fuels.

This thesis deal with design and implementation of innovative cooling method, intended primarily for medium-power synchronous generators. The main objective of this proposal is to remove the large heat exchanger connected to generator. This heat exchanger unduly increases the space requirements for the machine location. The proposed solution is to use a direct water-cooled stator. It is assumed that the rotor winding will be still cooled by air. Unlike current cooling system, the hot air from the rotor can be cooled in smaller cooler inside the generator. In this work are described methods which can be used for design of water cooling basic parameters, taking required temperatures into account. A small induction motor was selected for practical verification of the proposed cooling concept. This motor was modified into two variants - related to the old cooling of synchronous generators and related to the proposed solution. Both of these variants were measured and compared with each other. Subsequently, CFD models of these two variants were set up. Measured temperatures were used for debugging of models and identification of material properties of components of these machines. The final model of water-cooled variant also makes it possible to simulate the work of motor for higher performance and to determine the overload compared with the old cooling variant. Some knowledge and experience obtained from the small water-cooled induction machine were used in the design of water-cooling for large synchronous generator. In a similar way, CFD models of the old variant of cooling and proposed variant of water- cooling were created. Although these models were not verified by actual measurements on the generators, the results indicated that the application of water-cooling in this type of machine is appropriate and provides many benefits.

The goal of this project is to test the possibility to connect the Cogenerational generation of power 138 MW (still in the development stage) to the control room 110 kV in Prostejov production. This merge would product the electrical energy as well as the heat energy for all local area. In this dissertation we will be considering the solution of the steady state (stationary state) of system with the voltage level of 110kV, as well as the influence of the generation of power on this system, there by the suggesting a connection. The Congenerational production indicates higher effectiveness in the transformation of energy during primary production process due to the production of heat energy as well as the electrical energy from the primary power sources. In our country, as well as around the world, commonly used fuels are fossil fuels- coal, crude oil, and gas. As the demand for energy grows, those supplies are slowly running out. Not to mention that those fuels have a negative environmental impact. They are a source of carbon, which causes damage to the atmosphere and leads to global warming. Power plants which do not produce carbon are much safer for the environment, and much more productive. However, the residue of this energy is challenging to dispose of. Nuclear energy has common attributes with renewing the sources of energies that are extremely friendly to our environment. Nuclear power plants also produce enough energy and with the usage of Fourth generation reactors, they will be able to recycle the nuclear fuels. Today, more importance is put on renewing sources which are more gentle for the environment. In the near future, CEZ Company, the largest producer of electric energy is planning to use water energy. Water energy comes from water plants or dams. Other ecological forms of energy include geothermal and solar energies. These two types of energy are not as applicable for our geographical position. Geothermal energy is commonly used on islands where there is an abundance of natural hot springs. The most discussed source of energy is bioenergy. It uses natural wood sources, recycled wood products, and applies bioenergy as a main source for thermal power plants.

碩士<br>國立彰化師範大學<br>電機工程學系<br>101<br>With the industry development, the application of water heating is progressed from firewood to natural gas and electricity as heating sources. Because of the feature of fast heating and high efficiency, electronic heater is widely utilized in household to improve the living convenience. However, the temperature of tankless water heater cannot be changed with minor adjustment, which has been compensated by digital thermostat water heater in literature. Also, traditional metal contacting, utilized to control the signal of temperature, might cause electric leakage and rusted metal. Therefore, a sensor control module is proposed in this study to avoid above shortages and reach the purpose of contactless control through ultrared ray sensor. The system of sensor control module for instaneous water heater is to control water temperature without touching the water heater. In the system, a microprocessor control unit is utilized to control the relay and then adjust the heating condition of contactless sensor. The experiment applies reflective sensor of ultrared rays to be the temperature controller with an operating frequency between 2 kHz to 5 kHz. The signal is evaluated as effective while the sensing period is more than 30 ms. The result proves the proposed system achieves the function of contactless temperature control and the advantage of maintenance-free to extend product life.

碩士<br>國立雲林科技大學<br>電機工程系<br>107<br>In recent years, energy policy has always been an important issue for human life. Under the pressure of global greenhouse gas emissions, how to develop high energy efficiency and environmentally friendly is the future trend for theproduction .This study proposes innovative reserve-type electric water heater products, and develops product features, good energy efficiency, high water release rate as the research target; and desigs a set of test chart control system in the laboratory, Using the laboratory simulation economics department of the Commodity Inspection Bureau sets the energy efficiency test standard. Automatically adjust the data through various instruments, set the collected data, and analyze the energy consumption analysis data through the test computer. The energy consumption standard must meet the energy efficiency classification specification of the Energy Bureau and the CNS11010, CNS3765 Commodity Inspection Bureau inspection specification, and optimize the output power optimization reserve. Type electric water heaters develop energy-saving products. In the future, the trend of reserve electric water heaters will match the current demand for hot water showers. The stainless steel liner will have higher pressure resistance and larger water output. The hot water temperature control is an electronic temperature sensor. The reaction is more sensitive and the heating temperature is more precise. More energy-saving, the The product focuses on beautiful appearance, no space, energy saving and low energy consumption, good energy saving, and continuously use is the mainstream innovation in the market. Keywords: Energy policy, electric water heater, energy consumption analysis, energy efficiency grading, temperature sensor, stainless steel.

碩士<br>國立雲林科技大學<br>工業工程與管理系<br>107<br>With the changing global environment and changing people's consumption habits, Taiwan's electric water heater industry is facing more and more diversified competition. No matter how the external environment changes, only by strengthening the competitiveness of enterprises and creating competitive advantages of enterprises, such as the acquisition of product quality image must be formed through continuous improvement and accumulation, and the maintenance of quality must rely on experience accumulation. To achieve quality prevention measures. Therefore, in order to improve the quality of products, we need not only to make the products well, but also to have the thinking of risk management and continuous improvement, efficient management and monitoring feedback mechanism to create the value of the existence of enterprises. This study explores the quality prevention and improvement of electric water heater manufacturing process. In the part of quality prevention, failure mode and effect analysis (FMEA) is used to discuss the possible causes of product failure in the manufacturing process of electric energy water heater. Some improvement measures are put forward to reduce the loss caused by the effect, reduce the risk priority index to an acceptable range, and prevent the causes of failure again. Occurs. In the quality improvement part, QCC and QIT are used to improve the quality. Through this study, we can improve people's ability of quality prevention and logic improvement, as well as their professional knowledge and skills.

碩士<br>樹德科技大學<br>經營管理研究所<br>101<br>Knowing the role of purchase intention is important to marketers as a determinant of success. To ensure success, an understanding of purchase intention is very important. The purpose of the research study is to determine the factors that influence purchase intention from gaining knowledge about consumer buying towards the electric water heater product, investigate the reasons that may influence intention of buying the electric water heater product. There are a lot of competitors in electric water heating market which have advance manufacturing facilities and technologies. To be successful, any electrical water heater companies have to strengthen the performance of their electrical water heater in order to remain competitive edge in the water heating industry. Another possible reason is the introduction of benefit factor as a mediator that is customer satisfaction between product quality, service quality, price fairness and purchase intention (indirect effect) as suggested by past researches which could increase the importance of perceived quality in the study relationships. Electric water heater companies should not emphasize solely on the physical appearance of the Electric water heater but also on the brand image of an electric water heater manufacturer, customer satisfaction, product quality, service quality, and price fairness of the electric water heater.

Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e Tecnologia<br>It is intended, with this dissertation, to explore a solution for an DHW system based on a thermostated bath (DHW-TB). Thus, the goal is the development of a study on an equipment that is based on a thermoaccumulation system but with a similar operation as an electric shower. This system is not implemented in the Portuguese market and, with this study, it is intended to analyse its possible viability either as an independent system or as a support system for some DHW equipment currently in force in the market.Thus, for the development of this system, two phases of operation are assumed:Pre-start phase: phase in which the system is full of water at the supply network supply temperature, there being no water inlet or outlet of the system, and this is undergoing heating through the electric resistance until it reaches a predefined temperature.Usage phase: phase in which there are an inlet and outlet of a water flow, the volume of water entering is at the supply temperature of the supply network, the volume of water leaving the outlet temperature as temperature is considered as the average temperature of the water inside the system, and a power resistance heats the volume of water inside the system.The DHW-TB system is made up of two fundamental elements: the thermostatized water bath that serves as an energy accumulator from an electric resistance and a copper tube arranged in a propeller through which circulates the water to be heated and used.When studying the sensitivity of the system when used to the volume of water of the bath with a pressure of 1 bar, it was concluded that the system is more efficient with the use of volumes of the thermostatized bath of smaller volume.The effect of changing the flow rate or length of the tube in the system is also verified. The flow variation, between a minimum and maximum value previously defined, was explored in the DHW-TB system with a fixed flow. It has been concluded that there is a greater use in fixed flow systems with reduced value.By varying the percentage of occupancy that the diameter of the propeller occupies to the diameter occupied by the volume of water, the maximum length of the tube varies. It has been shown that the variation of the length does not produce changes in the time of use of the system.These results point to the favouring of more compact systems, of smaller volume and smaller tube length, with the use of a smaller flow rate.By evaluating the change in the pressure at which the thermostatized bath water is subjected, and its impact on the time of use of the system, an advantage is identified in the use of pressurised systems. However, the high start-up time of the pressurised systems may make their use unfeasible.After the analysis with a fixed flow, the behaviour of the system was studied using a variable flow.The sensitivity of the system to the variation in the time of use available to the change in bath volume was thus investigated. It has been found that the smaller the pipe length, the more sensitive the system is to a change in the time of use for a larger volume tank.In order to have a good comparison factor of the system, it was considered the Utilization Performance Index, which compares the time of use to the necessary reheating time after use. It has been found that the system is much more efficient with lower thermostatted bath temperatures. However, the lower the temperature of the thermostatted bath, the more sensitive the system is to the variation of the tube length. When comparing the behaviour of the system in the approach of fixed and variable flow, there was a clear advantage for the variable flow approach.In conclusion, it can be stated that such a system will be useful, even if it requires particular parameterisations, such as the preheating temperature, for any short-term use (bathroom sink and / or kitchen). For prolonged use, and as an independent system, this depends on the user’s requirement in terms of flow rate and temperature of use. This type of equipment is indisputably viable as auxiliary equipment. If we refer to a water heater installation, such as those in most Portuguese homes, this system can largely replace the use of gas by electricity, since the water heater can only be used to preheat the water from the network to a slightly higher system inlet temperature; and also with a view to nullifying the waste of cold water characteristic of the start of use of a system provided only with water heater. As support equipment for a heater, it may do so in order to cope with peaks of use. The most interesting solution may, however, be the support for a solar thermal system.<br>Pretende-se, com esta dissertação, explorar uma solução para um sistema AQS com base num banho termostatizado (AQS-BT). Assim, tem-se como objetivo o desenvolvimento de um estudo sobre um equipamento que tenha como base um sistema de termoacumulação mas com um funcionamento similar a um chuveiro elétrico. Este sistema não está implementado no mercado português e, com este estudo, pretende-se analisar a sua possível viabilidade quer enquanto sistema independente, quer enquanto sistema de apoio a algum equipamento AQS atualmente em vigor no mercado.Assumem-se, assim, para o desenvolvimento deste sistema, duas fases de funcionamento:Fase de pré-arranque: fase na qual o sistema está cheio de água à temperatura de abastecimento da rede fornecedora, não havendo qualquer entrada ou saída de água do sistema, e sofrendo esta um aquecimento por via da resistência elétrica até chegar a uma temperatura pré-definida.Fase de utilização: fase na qual há entrada e saída de um caudal de água, sendo que o volume de água que entra está à temperatura de abastecimento da rede fornecedora, o volume de água que sai tem como temperatura a temperatura de saída que é considerada como sendo a temperatura média da água no interior do sistema, e o volume de água no interior do sistema é aquecido por uma resistência de potência.O sistema AQS-BT compõe-se de dois elementos fundamentais: o banho termostatizado de água que serve de acumulador de energia proveniente de uma resistência elétrica e um tubo de cobre disposto em hélice por onde circula a água a aquecer e utilizar.Ao estudar-se a sensibilidade do sistema quando utilizado em relação ao volume de água do banho com a pressão de 1 bar, concluiu-se que o sistema é mais eficaz com a utilização de volumes de banho termostatizado de menor volume.Verifica-se, igualmente, o efeito que a variação do caudal ou do comprimento do tubo teriam no sistema. Explorou-se a variação do caudal, entre um valor mínimo e máximo previamente definidos, no sistema AQS-BT com caudal fixo. Chegou-se à conclusão a existência de um maior aproveitamento em sistemas de caudal fixo com um valor reduzido.Variando a percentagem de ocupação que o diâmetro da hélice ocupa em relação ao diâmetro ocupado pelo volume de água, varia-se o comprimento máximo de tubo. Demonstrou-se que a variação do comprimento não produz alterações no tempo de utilização do sistema.Estes resultados apontam para o favorecimento de sistemas mais compactos, de menor volume e menor comprimento de tubo, com a utilização de um caudal mais reduzido. Avaliando a alteração da pressão a que a água do banho termostatizado está sujeita, e qual o seu impacto no tempo de utilização do sistema, identifica-se uma vantagem na utilização de sistemas pressurizados. No entanto, o elevado tempo de arranque dos sistemas pressurizados pode inviabilizar a sua utilização.Após a análise com caudal fixo, estudou-se o comportamento do sistema usando um caudal variável.Explorou-se, assim, a sensibilidade do sistema à variação do tempo de utilização disponível em relação à variação do volume do banho. Constatou- se que, quanto menor o comprimento de tubo, mais sensível é o sistema a uma variação do tempo de utilização para um tanque de maior volume.Para haver um bom fator de comparação do sistema considerou-se o Índice de Desempenho de Utilização, que compara o tempo de utilização ao tempo necessário de reaquecimento após utilização. Verificou-se que o sistema é muito mais eficiente com temperaturas de banho termostatizado inferiores. No entanto, quanto mais baixa a temperatura do banho ter- mostatizado, mais sensível é o sistema à variação do comprimento do tubo. Ao comparar-se o comportamento do sistema na abordagem de caudal fixo e variável, verificou-se uma clara vantagem para a abordagem de caudal variável.Em conclusão, pode-se afirmar que tal sistema será útil, ainda que requerendo parametrizações particulares, como seja a temperatura de pré-aquecimento, para qualquer uso de curta duração (lavatório de casa de banho e/ou cozinha). Para usos prolongados, e enquanto sistema inde- pendente, tal depende da exigência do utilizador em termos de caudal e temperatura de utilização. Este tipo de equipamento é indiscutivelmente viável enquanto equipamento auxiliar. Se nos referirmos a uma instalação com esquentador, como as presentes na maioria dos lares portugueses, este sistema pode substituir largamente o uso do gás por electricidade, dado que o esquentador pode servir apenas para fazer um pré-aquecimento da água de origem da rede a uma temperatura de entrada do sistema um pouco mais elevada; e também com vista a nulificar o desperdício de água fria característico do início de utilização de um sistema munido apenas de esquentador. Enquanto equipamento de apoio a um termoacumulador, podê-lo-á fazer com vista a fazer face aos picos de utilização. A solução mais interessante poderá passar, no entanto, pelo apoio a um sistema solar térmico.

碩士<br>國立勤益科技大學<br>冷凍空調系<br>97<br>The thermal handing process is an important issue to improve the material and relative electronic physical properties for semiconductor electronic device. In this study, a numerical analysis is applied to investigate the influence of heating powers and heating speed on the surface temperature uniformity of a wafer heater. Due to the increase of the data transmission speed in the network, the data exchange capacity of a electronic communication device also seriously increases. In order to maintain a suitable temperature environment for operating the communication device and reduce the production cost of the device, a novel design for the substrate of the device was carried out, which can quickly remove the heat from the substrate and reduce the average temperature of the substrate.

碩士<br>國立彰化師範大學<br>電機工程學系<br>99<br>The need of hot water has become necessity of bath or shower in a human society by looking for comfortable life. So water heater is an important home appliance equipped in every modern family. Various products are available from the market for the need, to categorize the types of energy resource for heating up water, Gas and Electric are the two main kinds; to categorized by the way of heated water be supplied, Instantaneous heated water supply and storage heated water supply are the two main kinds. For reduce carbon exhausting and saving energy resource, it has become more popular in use of Solar Power on water heater in recent decade that energy resource shortage crisis and global warming have been disclosed. No matter what kind of energy in use for heating up water and which way of supply, Instant and sufficient hot water supply with Constant temperature are the main challenge for water heater design. This study is based on the complementary of Wind energy and Solar power as major energy for water heater design, having Wind energy heat up water tank while Solar power is shortage during night time and continuous cloudy randy days. With additional implementation by auxiliary electric heater after water tank for keeping the constant temperature hot water supply to the user. In this way, not only for refrain from the energy waste of non useful heat up the whole water tank which most of Solar water heater with its auxiliary system is design for, but also the goal of minimize the use of electricity can be accomplished.

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering in the School of Electrical and Information Engineering, July 2017<br>This dissertation presents the design and testing of controllers intended to provide au- tonomous demand response, through the use of water heater loads and grid frequency measurements. The controllers use measured frequency as an indication of the strain on a utility grid, which allows demand side management to be isolated from any form of central control. Water heaters can operate as exible loads because their power consump- tion can be dispatched or deferred without directly impacting users. These properties make it possible to control individual water heaters based on the functioning of the grid, rather than end user input. The purpose of this research is to ultimately provide a low- cost alternative to a traditional Smart Grid, that will improve the resilience of a grid without negatively impacting users. The controllers presented here focus on ensuring that users receive hot water, while attempting to reduce any imbalance between power generated and power consumed on the grid. Simulations of these controllers in various situations highlight that while the controllers developed respond suitably to variations in the grid frequency and adequately ensure end users receive hot water, the practical bene t of the controllers depends largely on the intrinsic characteristics of the grid.<br>CK2018

碩士<br>國立中興大學<br>機械工程學系所<br>104<br>The essence of Six Sigma is a statistical quality control methods to improve the quality of the products to reduce the cost of bad waste products. This research attempts to use the six sigma management approach for the improvement of the manufacturing process of stock-type electric water heater of the case company. We tried to the useful tools of quality improvement to discover the problem and point out the weaknesses of the process. The Failure Modes and Effects Analysis (FMEA) was then conducted to identify high priority risk priority number (RPN) steps, followed by proposing feasible methods to prevent the errors from happening and thus enhance the reliability of the product. In order to find the RPN steps, the Taguchi Method was adopted for experimental design and failure analysis. The optimal parameter set was than obtained and further used to enhance the quality of the products and reduce the cost. Hence achieve the ultimate goal of Six Sigma. Through our systematic approach, the consumption coefficient of the stock-type electric water heater products was increased from -0.59 to 3.66 and the allowable average consumption coefficient was reduced from the original 0.9075 kWh to 0.5804 kWh. Each year, a stock electric water heater can save energy about 90 kWh, hence reduce carbon dioxide emission of 57.63 kg. If we consider the overall sales of the reserve-type electric water heaters, it is estimated that about 1,355 million kWh of electricity can be saved and 8,645 103 kg of carbon dioxide emission can be reduced.

ABSTRACT- Electricity is usually supplied by diesel generators in remote communities at high costs. In such a case, renewable energy sources (RESs), such as wind and photovoltaics (PV), can be cost effective to meet part of the energy needs. However, the integration of RESs may lead to large power fluctuations and to the operation of the diesel genset under-loaded. Traditionally, energy storage devices have been used to provide power smoothing and frequency regulations, but this solution is quite costly. In this thesis, electric water heaters (EWH) are used to assist with power balancing and frequency regulation and to prevent the diesel genset from operating under-loaded, in a PV-diesel hybrid mini-grid. The characteristics of the diesel genset, PV, and the EWH are studied. An EWH is modeled using Matlab/SIMULINK. Approximate linear equations are derived and used for estimating the amount of power an EWH can take or drop, by varying the set point temperature Td. A review of methods used to control the EWH are then presented. A basic integrated control of the EWH, which varies the set point temperature (Td), using the system frequency is studied. Issues using this control in a small power system are investigated, and a modified integrated control is proposed to solve them. The effectiveness of basic and modified integrated controls is validated using a hybrid PV-diesel mini-grid benchmark implemented in PSCAD. Moreover, the impact of the PV on fuel consumption, and frequency variations is observed. Simulation results indicate that the modified integrated control is effective for frequency regulations, peak shavings, and for preventing genset operates under loaded.

碩士<br>大葉大學<br>食品工程研究所<br>90<br>In this research, ohmic heating treatment was studied to observe the changes and interactions of electrical conductivity, water activity, and viscosity. Wheat starch, corn starch, potato starch were used as experimental materials. Starch and distilled water were mixed as the ratio 7.97%( w/w ), 6.53%, and 5.55% to form starch suspensions and 0.3%( w/w )NaCl was added as electrolyte. Before the experiments, starch suspensions were boiled to 100℃ to make it fully-gelatinized and cooled to 30℃. The heating range was 30 ~ 80℃. In ohmic heat, samples were heated by using alternating current and the voltage gradient was 4.67 V/cm. The electrical conductivity increased as temperature increased, and in high temperature range the tendency turned nonlinear. The m values of electrical conductivity was similar, and the higher suspension concentrations, the lower in electrical conductivity. For water activity, samples were heated by circulating water bath. Water activity decreased slightly as temperature was between 30 ~70℃,but between 70 ~80℃, the water activity increased because of the raise of free water. Viscosity of samples was determined by Brookfield viscometer and hot plate. High viscosity occurred at high starch concentration, and the higher in temperature, the lower in viscosity. In regression analysis, the relationship among the electrical conductivity, water activity, and viscosity were clear when the starch concentrations were low. For the interrelationship of the three properties, the electrical conductivity and water activity was negative-related because of gelation, whereas the relation between Water activity and viscosity was not clear. The electrical conductivity and viscosity was negative-related because of the increased rate of water flow. In addition, 70℃was a critical point for water activity where showed reverse tendency. The wheat starch was the most suitable material for analyzing the relationship among the electrical conductivity, water activity, and viscosity.