Solar Domestic Hot Water systems and air-source heat pumps offer the potential for energy savings in residential hot water production, however their performance is limited in cold climates, where the low ambient temperature reduces the collector efficiency or the heat pump coefficient of performance. Combining these systems into a Solar-Assisted Heat Pump can alleviate these limitations by reducing the required collector temperature and by providing an increased heat pump evaporator temperature. This study is a continuation of the development of an Indirect Solar-Assisted Heat Pump undertaken at the Queen’s University Solar Calorimetry Laboratory. Previously, a numerical study compared its performance to existing technology, and based upon this feasibility analysis, a prototype was constructed for controlled laboratory tests using simulated solar input. In the current study, the prototype was modified to include a novel hybrid collector such that its performance under actual weather conditions throughout the year could be assessed. On sunny days, the system experienced daily averaged collector efficiencies between 0.47 and 0.88, depending on the flow rate and season. Averaged heat pump coefficients of performance of 2.54 to 3.13 were observed. Overcast days experienced reduced coefficients of performance, between 2.24 and 2.44. However, on overcast days, upwards of 76% of the collected energy gain was from convection with the surroundings. Based upon these experimental results, a model for the hybrid collector was developed. Annual simulations of the system were conducted to compare the performance of the solar heat pump system when fitted with the hybrid collector relative to cases with more conventional glazed and unglazed collectors commonly used in solar thermal systems. Results were produced for three Canadian cities: Toronto, Vancouver and Winnipeg. The heat pump with the hybrid collector outperformed the other collectors in the Toronto climate, with a free energy ratio of 0.548. Adding a thermally controlled valve to the hybrid collector was proposed to further increase the annual free energy ratio, and was shown to perform best in all three cities, with free energy ratios of 0.558, 0.576 and 0.559 for Toronto, Vancouver and Winnipeg, respectively. It is proposed that additional improvements could be achieved by allowing the collectors to deliver heat directly to the storage tank, by circumventing the heat pump if the conditions were favorable. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2012-01-06 13:44:41.77

There is widespread acceptance of the need to reduce energy consumption within the built environment. Despite this, there are often large discrepancies between the energy performance aspiration and operational reality of modern buildings. The application of existing mitigation measures appears to be piecemeal and lacks a whole-system approach to the problem. This Engineering Doctorate aims to identify common reasons for performance discrepancies and develop a methodology for risk mitigation. Existing literature was reviewed in detail to identify individual factors contributing to the risk of a building failing to meet performance aspirations. Risk factors thus identified were assembled into a taxonomy that forms the basis of a methodology for identifying and evaluating performance risk. A detailed case study was used to investigate performance at whole-building and sub-system levels. A probabilistic approach to estimating system energy consumption was also developed to provide a simple and workable improvement to industry best practice. Analysis of monitoring data revealed that, even after accounting for the absence of unregulated loads in the design estimates, annual operational energy consumption was over twice the design figure. A significant part of this discrepancy was due to the space heating sub-system, which used more than four times its estimated energy consumption, and the domestic hot water sub-system, which used more than twice. These discrepancies were the result of whole-system lifecycle risk factors ranging from design decisions and construction project management to occupant behaviour and staff training. Application of the probabilistic technique to the estimate of domestic hot water consumption revealed that the discrepancies observed could be predicted given the uncertainties in the design assumptions. The risk taxonomy was used to identify factors present in the results of the qualitative case study evaluation. This work has built on practical building evaluation techniques to develop a new way of evaluating both the uncertainty in energy performance estimates and the presence of lifecycle performance risks. These techniques form a risk management methodology that can be applied usefully throughout the project lifecycle.

The Achilles heel of the heat pump technology has for long been the low efficiency occurring during domestic hot water production. The problem is the high condensation pressure needed to reach high temperatures. To produce domestic hot water, the system need to deliver a supply temperature of about 60 °C, to be compared with a supply temperature of around 30-50 °C when heat is delivered to a radiator circuit. This drawback has for long held the heat pump technology back and instead gave room for alternative technologies on the market, like district heating.The Energy Machine is a heat pump system developed to bypass the poor efficiency during domestic hot water heating. The technology is based on the use of two heat pumps working together. The main heat pump delivers heat to the heating system, as usual, whilst the second smaller heat pump heats the domestic hot water. As the second heat pump is fed with reject heat from a subcooler in the main heat pump, it can operate at high efficiency, even when producing domestic hot water.The aim of this master thesis has been to investigate how the performance of the Energy Machine differs from that of a conventional heat pump system. In order to do so, models describing the two systems have been designed using MATLAB, Simulink. Simulations have then been performed to investigate how the two systems perform on an annual basis.The results of the simulations show that the Energy Machine performs much better than the conventional systems at most operating conditions, especially during domestic hot water heating. The annual COP- factor of the Energy Machine has proven to be 33,5 % higher than that of a conventional heat pump system. / Värmepumpsteknikens akilleshäl har sedan lång tid tillbaka varit den låga verkningsgraden som uppstår vid tappvarmvattenproduktion. Problemet är att det krävs mycket högt kondenseringstryck för att uppnå den höga framledningstemperatur som efterfrågas vid tappvarmvattenproduktion. Normalt krävs en temperatur omkring 60 °C vid tappvarmvattenproduktion, att jämföras med 30-50 °C då värme levereras ut på en radiatorkrets. Detta problem har länge hållt värmepumpstekninken tillbaka och istället givit utrymme för alternativ teknik på marknaden, såsom fjärrvärme.Energimaskinen, eller Energy Machine, är ett värmepumpssystem utvecklat för att kringgå problemet med den låga verkningsgraden vid tappvarmvattenproduktion. Tekniken bygger på två värmepumpar som arbetar tillsammans. En basmaskin används för att leverera värme ut på värmesystemet, medan en mindre värmepump används för att producera tappvarmvatten. Den mindre värmepumpen matas med värme från en underkylare i basmaskinen, vilket ger hög förångningstemperatur och därmed hög COP faktor, även vid tappvarmvattenproduktion.Målet med projektet har varit att jämföra prestandan hos en Energy Machine med ett konventionellt värmepumpssystem. För att kunna göra dettta har två modeller designats, en modell som beskriver en Energy Machine och en modell som beskriver ett konventionellt värmepumpssystem. Modellerna gjordes i MATLAB, Simulink, och simuleringar utfördes varpå resultaten tolkades och jämfördes.Resultaten från simuleringarna visar att en Energy Machine presterar mycket bättre än ett konventionellt värmepumpssystem i de allra flesta driftfallen , men särskilt vid tappvarmvattenproduktion. Simuleringarna visar att COP- faktorn på årsbasis för en Energy Machine är 33,5 % högre än den för ett konventionellt värmepumpssystem.

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.

Solar Domestic Hot Water (SDHW) systems collect energy from the sun to heat the household water. In the context of a system energy balance, numerical simulations were conducted using the commercial software “TRNSYS-17” to study the SDHW system performance (solar fraction) influenced by the critical parameters in various sizes of the thermal storage tank (TES) tank. The key parameters were the magnitude of the collector mass flow rate, degree of thermal stratification within the TES tank, and the duration of the mass flows through the collector. An empirical correlation was obtained to determine the operating collector mass flow rate and TES volume to deliver the peak system performance. The correlation was preliminarily verified with different weather data. The studies showed that the optimal collector mass flow rate occurred when the same amount of total daily household demand passed through the collector. Furthermore, when the twofold amount of the household demand passed through the collector, the optimal dimensionless tank volume became insensitive to the change of collector flow rate and remained constant at 0.84. Researchers discovered that promoting thermal stratification within the TES tank would enhance system performance. Thermal stratification within a TES improves the system performance by sending colder water to the solar collector and hotter water to the household. This research challenges the research community’s focus on thermal stratification by showing that solar fraction is directly related to the solar collector heat losses. As such, the role of the TES tank is to supply cold fluid to the collector to minimize collector losses. Thermal stratification in the top portion of the tank is thus unimportant in influencing solar fraction. In this research, the pump is turned on/off by monitoring the temperature difference between the collector inlet and outlet. Different pump control strategies at different collector mass flow rates were implemented to adjust the pump-on time. The studies showed the system performance was negligibly affected (~0.5%) by employing different pump control strategies while the collector mass flow rate was held constant. / Thesis / Master of Applied Science (MASc)

Master’s thesis on Energy performance of domestic hot water preparation is concerned with calculating and comparing the energy performance of domestic hot water preparation in two-generation family house with an administrative part. Energy performance of domestic hot water preparation is calculated by two calculation methods and by experimental measurements, which are compared at the end of the thesis. The calculation is performed according to standard ČSN 06 0320 and set of standards ČSN EN 15316-3. Thesis is processed in accordance with valid legislative regulations.

Det pågår idag arbete på många håll för att göra våra bostäder mer energieffektiva, ofta genom tekniska förbättringar av till exempel klimatskärm och värmesystem. En post i energianvändningen som inte alltid får lika mycket fokus är varmvattenanvändningen. Varmvattenanvändningen mäts sällan i flerbostadshus, vilket gör att kunskapen kring den är relativt låg. På senare år har dock allt fler bostadsbolag börjat arbeta för att minska vattenanvändningen och en metod som har blivit allt vanligare är individuell mätning och debitering. I denna rapport redovisas ett examensarbete kring olika aspekter på vattenanvändning i flerbostadshus. Vattenanvändningen i ett bostadsbolag som överväger att införa individuell mätning och debitering undersöktes och jämfördes med statistik från ca 2000 lägenheter i två bostadsbolag som redan infört individuell mätning. Resultaten visar att användningen i allmänhet är lägre i fastigheter med individuell mätning, men också att användningen varierar stort, framförallt mellan olika lägenheter. Det finns också stor variation i hur stor andel av den totala användningen som är varmvatten, men resultaten tyder på att 40% är ett bättre antagande än de 30% som ofta används som schablonvärde. För att ge en bild över vattenanvändningen i svenska flerbostadshus och hur den utvecklats genom åren sammanställdes också statistik från vattenmätningar i olika undersökningar från de senaste 60 åren. Resultatet visar att variationen är stor, men att användningen per person varken är högre eller lägre nu än på 1950-talet. En möjlig utveckling är att användningen tidigare stigit, men sedan vänt nedåt igen. Per lägenhet och per kvadratmeter finns det dock en tydligare minskning, sannolikt på grund av minskande boendetäthet. Detta illustrerar en problematik i analyser av vattenanvändning: nyckeltalet måste väljas med omsorg. Sammanställningen visade också att intresset för att följa upp vattenanvändningen verkar ha varierat och att mätningar gjorts främst under tre perioder. I studien sammanställdes även vilken effekt införande av individuell mätning och debitering haft i olika undersökningar. Tydligt är att effekten varierar beroende på förutsättningarna i olika fastigheter, men en minskning av varmvattenanvändningen med 15-40% bör kunna förväntas. Med hjälp av boendestatistik undersöktes också olika variablers inverkan på vattenanvändningen. Endast en mindre del av variationen i vattenanvändning mellan olika fastigheter kunde förklaras med variabler som ålder och inkomstnivå. Viss ökad användning för åldersgrupperna 16-19 och 45-54 år kunde ses. Andra resultat var att vattenanvändningen minskar något med ökad andel lokalyta, medan fastigheternas byggår inte påverkar användningen. Individuella variationer och skillnader i beteende och vanor hos de boende är dock sannolikt de viktigaste förklaringarna till variation i vattenanvändning. En huvudslutsats i studien är att vattenanvändningen varierar stort mellan olika användare, och det kan vara svårt att förklara varför användningen är högre i vissa fastigheter och lägre i andra. Inte bara den totala vattenanvändningen utan också andelen som blir varmvatten varierar, vilket gör att det finns ett behov av att mäta även varmvattenanvändningen i de fall detta inte görs. Kollektiv varmvattenmätning skulle också ge bättre underlag för beslut om att införa individuell mätning och debitering – och för uppföljning av resultatet. / As multi-family houses get more energy efficient thanks to technical improvements of for example the building envelope and heating system, domestic hot water becomes an increasingly important part of the overall energy performance. Despite this fact, water use does not always get much attention, and in Sweden it is not common practice to measure the amount of hot water used in multi-family houses. In recent years, more and more housing companies have realized that there is a potential for improving the energy performance further by reducing the use of hot water. One increasingly popular method for this is individual metering – which is common in other countries but not the established practice in Sweden. This thesis deals with various aspects of water use in multi-family houses. Water use in a housing company considering to introduce individual metering was analyzed and compared with data from approximately 2000 flats in two other housing companies, which had already introduced individual metering. The results show that water use is generally lower in houses with individual metering, but that there is a considerable variation, particularly when studying water use in individual flats. There is also a large variation in the proportions between hot and cold water, but 40% hot water seems to be a better estimate than 30%, which is a commonly used value. Data on water use from other studies, covering the last sixty years, was also collected, in order to give an overview of water use in Swedish multi-family houses. The data shows great variation, and neither a significant increase nor decrease in water use per capita can be seen. One possible scenario is that water use per capita has previously increased, but then turned to a decrease. When measured as water use per square meter of living area or per flat there has been a significant reduction, mainly due to a gradually decreasing housing density. This illustrates a problem when analyzing water use: care must be taken when choosing which unit to use when comparing different data. Another result is that studies of water use in Swedish multi-family houses mainly appear in three periods, showing that there has been a varying interest in water use and its impact on energy performance. Data from other studies of individual metering was also collected, showing that the effect varies between different projects and houses, but that an expected result might be a reduction of hot water use by 15-40%. The thesis also includes an analysis of to what degree variation in water use can be explained by factors such as age and income levels. The variables available in the data could only explain part of the variation in water use, but some impact could be seen, e.g. that people in the ages of 16-19 and 45-54 years seem to use more water than others. However, most of the variation in water use is probably caused by different users’ individual behaviour and habits. One important conclusion is that there is a large variation in water use, and that it is difficult to explain why water use is high in some houses and low in some. Not only does the total water use vary, but also the proportions between hot and cold water. With this in mind, installing hot water meters would be beneficial for many housing companies, not only giving better data on energy performance but also as a first step before introducing individual metering.

This master’s degree project concerns the combination of a multi dwelling passive house with solar energy for the generation of electricity and domestic hot water (DHW). Different alternatives with either solar thermal systems or photovoltaic (PV) systems are compared with two reference alternatives producing DHW from electricity or district heating. The economical comparison uses a life cycle cost (LCC) perspective based on the present value of expenditures for investment, energy and annual operating and maintenance. The energy yields from the solar energy systems were calculated by hand and with simulation software. Calculation and dimensioning of PV systems were carried out with a software called PVSYST. Solar thermal systems were calculated by hand and with the software Winsun Villa Education. Both softwares use hourly weather data for the calculations. The LCCs are lower for the two reference alternatives than for the solar energy alternatives. The reference alternative with district heating generates the lowest LCC. The alternatives with solar thermal energy replace more energy and have significantly lower LCCs than the PV alternatives. The study also shows the importance of using cheap and environmentally friendly backup energy for producing DHW. When aiming for a quantitative energy use target, the DHW-circulation losses ought to be taken into account as these can be extensive.