Enormous quantities of heat are available in air, soil, water, exhaust air from buildings, and in waste water of any kind. However these heat sources are use-less for heating purposes since their temperatures are lower than the tempera-ture required for heating. Heat pumps can be used to extract heat from these sources with a small expenditure of additional energy and up-grade and deliver the energy as useful heat for room heating. The heat pump cycle employs the well-known vapour compression cycle. The amount of heat delivered by a heat pump is equal to the amount of energy extracted from the heat source plus the heat equivalent to the compression work of the heat pump. Heat pumps, of course, are being generally accepted as outstanding energy saving units due their coefficient of performance (COP). Heat pumps for house heating have been used extensively in many countries and are especially common in Sweden. The annual growth rate of heat pump usage in Sweden is the same as in rest of Europe. According to the Swedish heat pump association, between 1986 to August 2003, the number of installed heat pump units in Sweden was 332,309. The demand for heat pumps started to increase from the year 1995 and in the year 2002, approximately 40,000 heat pump units were installed. Among the many types available, single-family heat pumps providing heating capacity of about 5 kW are widely popular. The main drawbacks of heat pumps are the complexity of the systems, high cost, need of technical knowledge, safety hazards and environmental effects of certain refrigerants, etc. An efficient heat pump with small refrigerant charge would have less of some of these drawbacks and could be a competitive alterna-tive to other heating processes. In this study, methods of refrigerant charge minimisation without reducing the performance of a small capacity (5 kW) heat pump have been investigated. Work has been focused on finding refrigerant charge distribution in different components of the heat pump, on finding out the solubility of refrigerant (pro-pane) with different compressor lubrications oils, on testing different types of compact heat exchangers, on constructing new minichannel heat exchangers and on finding correlations for calculating the heat transfer of minichannel heat exchangers. The results included in this thesis have been presented in four con-ference papers and five journal papers of which two were published and three were submitted for publication. / QC 20100707

The tendency to use renewable energy resources has grown continuouslyover the past few decades, be it due to fear over warnings of globalwarming or because of the depletion and short life of fossil fuels or evenas a result of the interest which has developed among researchers doingscientific research into it. This work can be considered as joining any ofthese groups with an objective of giving electric light to the poorpopulation living in one of the poorest nations in the world.The aim of the work is to investigate supplying electric energy fromsolar-wind hybrid resources to remotely located communities detachedfrom the main grid line in Ethiopia. The communities in mind are one oftwo types; the first is the majority of the poor population residing in thecountryside; and the other is people relocated by the Government fromthe over used and dry regions to relatively productive and fertile ones inline with the long-term poverty reduction plan.The work was begun by investigating wind energy and solar energypotentials at four geographically different locations in Ethiopia bycompiling data from different sources and analyzing it using a softwaretool. The locations are Addis Ababa (09:02N, 038:42E), Mekele (13:33N,39:30E), Nazret (08:32N, 039:22E), and Debrezeit (8:44N, 39:02E).The results related to wind energy potential are given in terms of themonthly Average wind speed, the wind speed probability densityfunction (PDF), the wind speed cumulative density function (CDF), thewind speed duration curve (DC), and power density plots for all fourselected sites. According to the results obtained through the analysis, thewind energy potential, even if it is not exceptional, is irrefutably highenough to be exploited for generating electric energy.The solar energy potential, based on sunshine duration data collectedover a period of 7 - 11 years and radiation data obtained from differentsources, has been calculated using regression coefficients specific to thesites in question. Based on the sunshine duration data, the monthlyaverage daily sunshine amount for each of the places has also beencomputed and given in a form of plot. Through additional work on theresults of the calculations, the solar energy potential has been given inthe form of solar radiation plots for each of the selected sites. Asexpected, the results indicated an abundance of solar energy potential.It is based on the promising findings of these two energy resourcepotentials, wind and solar, that the feasibility study for a standalonesolar-wind hybrid energy supply system has proceeded, targeting thecommunity mentioned earlier. The hybrid system consisted of Windturbine, Photovoltaic panel, diesel generator and a bank of batteries, witha power conditioning converter included in the system.The hybrid standalone supply system is intended to provide electricity toa model community of 200 families with five to six family members ineach. The community is equipped with a primary load, a deferrable load,a community school and a health post. An electric load which includeslighting, water pumping, a radio receiver, and some clinical equipmenthas been suggested. Hybrid Optimization Model for ElectricRenewables, HOMER, software has been used for the analysis. Theaverage wind speed and average solar radiation calculated from the datafor all of the selected sites has been used to input into the software.The hybrid system design is approached in three different ways. The firstapproach is to include within the hybrid system those components whichare locally available, without giving special attention to their efficienciesand proceed with the design work. The second approach is tothoroughly search the market for the best and most efficienttechnological products and to select the best components for theanalysis. A third approach considered in an attempt of cost minimizationis to see if a self-contained type of design can be a better solution. Whatthis means is every household will have its own supply system that mayconsist of any combination of PV and wind turbine including converter,battery and charge controller.After running the simulations, lists of power supply systems have beengenerated, sorted according to their net present cost. Sensitivity variables,such as range of wind speeds, range of radiation levels and diesel pricehave been defined as inputs into the software and the optimizationprocess has been carried out repeatedly for the sensitivity variables andthe results have been refined accordingly. / QC 20100623

För ett genomsnittligt småhus i Sverige idag går ca 5000 kWh till hushållsel. Av dessa 5000 kWh går 7% till att driva diskmaskiner. Effektiviseringen av diskmaskiner har framförallt strävat efter en låg vatten- och energianvändning, en kort processtid samt en effektiv rening av disken. Det finns dock gränser för hur effektiva diskmaskinerna kan göras med traditionell teknik. Därför har producenter under de senaste åren börjat se sig om efter mindre traditionella metoder som till exempel bruket av en värmepump för att få ned energiförbrukningen. Syftet med det här examensarbetet har varit att ta fram systemlösningar för värmepump i diskmaskin samt att utvärdera energibesparingspotentialen i denna tillämpning. Målet har varit att ta fram och beskriva de möjliga systemlösningar som uppstår vid en idégenerering. Att välja ut två lösningar för närmare undersökning, att bestämma en lämplig kompressoreffekt samt att beräkna energibesparingen dessa lösningar ger. En litteraturstudie har gjorts av teknik och tillämpningar inom området, som till exempel värmeväxlaranvändning i diskmaskiner samt användandet av värmepumpar i andra vitvaror. Denna litteraturstudie följdes upp av en idégenerering, som tar hänsyn till möjliga värmekällor och –sänkor. Idégenereringen gav upphov till två systemlösningar som modellerades i MATLABs Simulink för att en lämplig kompressoreffekt och storleken på energibesparingen skulle bestämmas. De två utvalda lösningarna ifrån idégenereringen var utomhusluftlösningen, där värme hämtas från uteluften och energilagerlösningen, där värme hämtas ur ett energilager. I båda lösningarna överförs värmen till det kalla ingående vattnet. Energiåtgången för utomhusluftlösningen var beroende av köldmediets förångningstemperatur och modellering av lösningen visade att energiåtgången var 0,25 kWh vid en förångningstemperatur på -10°C, och 0,18 kWh vid 5°C. Vid modellering av energilagerlösningen påvisades en energiåtgång på 0,23 kWh. Slutsatsen som drogs var att kompressorn vid energilagerlösningen skall leverera en effekt på 240 W till köldmediet. / For an average detached house in Sweden today about 5000 kWh are used for household electricity. Of these 5000 kWh 7% are used to run dishwashers. The streamlining of dishwashers has above all strived for a lower water and energy use, a short process time along with a more efficient cleaning of the dishes. There are however limits for how efficient the dishwashers can be made with traditional technology and acceptable costs. Therefore producers have, during recent years, started looking for less traditional methods, for example the use of a heat pump to reduce the energy use. The purpose of this examination work has been to find system solutions for an application of a heat pump in a dishwasher and to evaluate the possible energy saving for each solution. The goal has been to find and describe possible system solutions, which came up during the idea generation. To choose some of these for a closer investigation, to decide a fitting mechanical power for the compressor and to calculate the energy saving these solutions give rise to. The method has consisted of a literature study, an idea generation, which takes the heat sources and sinks in consideration and a modelling in MATLAB’s Simulink of the selected solutions from the idea generation, which has been used to fit a mechanical power for the compressor. The result of the idea generation was two solutions, an outdoor air solution, which collects heat from the outdoor air and gives it to the cold water which enters the machine and a energy storage solution, which collect heat from a heat stock to give to the cold entering water. A modelling of these show an energy usage of 0,24 respectively 0,17 kWh for the outdoor air solution, with a heat source temperature at 10 °C respectively 5°C and a energy usage of 0,22 kWh for the energy storage solution for one round. The conclusion that was drawn was that the compressor of the energy storage solution should deliver a mechanical power of 240 W to the refrigerant.

As wind power expands rapidly worldwide, it is becoming more common to build wind farms in alpine locations where the wind resources often are good and conflicting interests are few. This is evident in Sweden where a substantial portion of the large wind parks planned are to be built in cold climate locations. The fact that icing of turbine blades and sensors can severely impact the production raises the question how large the losses are. In this thesis 10 wind parks comprising 45 turbines, well dispersed throughout Sweden are investigated. Daily production figures are compared to wind data from the MERRA reanalysis data-set in order to see if it is possible to determine the level of losses during the winter period caused by cold climate. A method is suggested where a relationship between daily production and daily average wind speed is established using representative summer days. This relationship is then used to calculate an expected production for the winter period. Losses are concluded as the difference between expected and actual production. The method did not produce a consistent and reliable result for the sites investigated. However, the method captures the overall trend with higher losses in the north of Sweden compared to the sites in the south where little or no icing is likely. At the sites where icing is expected, losses in the range of 10 to 20% of the annual production were calculated.

<p><!-- --></p><p>In the wake of the economic growth of the Chinese market the past couple of decades, the energy consumption has surged. One of the biggest consequences of the increased energy consumption is a massive increase in CO₂ emission. In fact, China has overtaken the U.S. as the biggest emitter of CO₂. In light of this energy-saving technology gets more important to implement. District heating is one of the solutions used with success in parts of China where heating is required. In this paper, an energy recovery technology has been examined for two climate zones in China namely a mechanical ventilation system using a flat-plate counter-flow heat exchanger. Beijing is located in a cold zone while Hong Kong is located in a zone with hot summers and mild winters. Cooling load calculations were conducted manually using the RTS - method developed by ASHRAE and heating load calculations were conducted for Beijing using Swedish guidelines stated in BBR. Further, the energy recovery unit (VM1) that was provided by Systemair AB was tested using a rig where different outdoor conditions were simulated. This data was then used to evaluate the potential for energy recovery in a model apartment located in the two zones. As expected, significant differences were obtained when comparing the performance for the two locations.</p><p> </p> / Redan avklarad

<p>This project deals with the potential of membrane stratified solar ponds which consist of two water layers, where one is a salt solution here, and a separating translucent membrane. An experimental pond was set up to study the thermal behaviour of such collector systems. The input is mainly solar radiation, sometimes when the ambient temperatures are higher than the pond temperatures also heat from the environment is transferred into the pond.</p><p>The measured temperatures of the pond, the ambient temperature, the global radiation and wind speed were the basis data for thermal calculations which showed that the pond was working well as a solar collector and thermal storage system all in one. Heat was not extracted from the pond however, only the losses to the environment were studied.</p><p>It was found out that the pond temperatures were higher than the ambient temperature over the whole measurement period of 12 days, and insulation and pollution problems as well as future prospects and suggestions for further studies are discussed at the end of this paper.</p>

<p>This thesis investigates the possibility of using an unglazed flat-plate solar collector as a cooling radiator. The solar collector will be connected to the condenser of a heat pump and used as cooler during nighttime. Daytime the solar collector will be connected to the evaporator of the heat pump and used as heat source. The two widely differing fields of application make special demands on the solar collector. The task is given by the heat pump manufacturer Thermia and the main objective is to find out whether a solar collector should be used as a cooler or not. The performance of the solar collector under varying environmental conditions is investigated using COMSOL Multiphysics 3.3. Only the cooling properties are investigated here. The performance of the solar collector as a heat exchanger is estimated using the effectiveness-NTU method, and the solar collector is found to be a good heat exchanger at low wind speeds. The heat transfer coefficients of the convection and radiation are determined for varying temperature and wind speeds. The convective heat transfer coefficient is lowered by tubes above the absorber plate and for a high convective heat transfer rate the solar collector surface should be smooth. For a high radiative heat transfer rate the surface needs to have a high emissivity. The cooling rate is higher from a warm surface than from a cold and since no temperature change of the heat carrier is necessary the solar collector should be kept at a high temperature. To increase the cooling rate alterations need to be made to the solar collector that makes its heating performance deteriorate. A solar collector that can be used for cooling is not an efficient solar collector.</p>

Increasingly intensive efforts are being made to enhance energy systems via augmented introduction of renewable energy along with improved energy efficiency. Resource constraints and sustained high fossil fuel prices have created a new phenomenon in the world market. Enhanced energy security and renewable energy development are currently high on public agenda worldwide for achieving a high standard of welfare for future generations. Biomass and municipal solid waste (MSW) have widely been accepted as important locally-available renewable energy sources offering low carbon dioxide (CO2) emissions. Concerning solid waste management, it has become a critical issue in Southeast Asia since the most popular form for waste disposal still employs open dumping and landfilling. While the need for a complete sustainable energy solution is apparent, solid waste management is also an essential objective, so it makes sense to explore ways in which the two can be joined. Electricity production in combination with energy recovery from flue gases in thermal treatment plants is an integral part of MSW management for many industrialized nations. In Sweden, MSW is considered as an important fuel resource for partially meeting EU environmental targets within cogeneration. However it is normally difficult to justify traditional cogeneration in tropical locations since there is little need for the heat produced. Similarly, MSW-fired cogeneration usually operates with low capacity during non-heating season in Sweden. Therefore, it is very important to find new alternatives for energy applications from waste, such as the implementation of thermally driven cooling processes via absorption cooling in addition to electricity production. The work presented herein concentrates first on an investigation of electricity generation from MSW power plants and various energy applications from waste in tropical urban areas. The potential for various types of absorption chillers driven by MSW power plants for providing both electricity and cooling is of particular interest. Additionally a demonstration and analysis of decentralized thermally driven cooling in district heating network supplied by low temperature heat from a cogeneration of MSW have been conducted. This study aims at developing the best system configuration as well as finding improved system design and control for a combination of district heating and distributed thermally driven cooling. Results show that MSW incineration has the ability to lessen environmental impacts associated with waste disposal, and it can contribute positively towards expanding biomass-based energy production in Southeast Asia. For electricity production, the proposed hybrid dual-fuel (MSW/natural gas) cycles feature attractive electrical efficiency improvements, leading to greenhouse gas emissions reduction. Cogeneration coupled with thermally driven cooling is a solution that holds promise for uniting enhanced sustainability with economic advantages. The system offers great opportunity for primary energy saving, increasing electrical yield and can significantly reduce CO2 emissions per unit of cooling as compared to compression chiller. The demonstration and simulation have also revealed that there is a potential with some modifications and improvements to employ decentralized thermally driven cooling in district heating networks even in temperate regions like Sweden. Thus, expanding cogeneration towards trigeneration can augment the energy supply for summer months in Europe and for year-round cooling in tropical locations. / QC 20110408

Secondary working fluids (secondary refrigerants, heat transfer fluids, antifreezes, brines) have long been used in various indirect re-frigeration and heat pump systems. Aqueous solutions (water solu-tions) have long been used as single phase (liquid only) secondary working fluids for cooling in supermarkets, ice rinks, heat recovery systems, heat pumps and other applications. However, aqueous solutions are increasingly used also for freezers in supermarkets and other applications in low temperature refrigeration. Of importance when comparing different secondary working fluids for indirect systems are the following basic thermophysical properties: freezing point, density, viscosity, specific heat, and thermal conductivity. Reliable data of these properties are needed to choose suitable fluid and to make technical calculations of an indirect refrigeration or heat pump system. The main intention of this work has been to select thermophysical property data with good or acceptable technical accuracy of a number of aqueous solutions that can be used by the refrigeration and heat pump industry, rather than focusing on a limited number of property values or scientifically very accurate measuring techniques. A thorough literature search was in view of this made to find the most reliable property values of aqueous solutions. Detailed literature references are given for thermo-physical properties of the following aqueous solutions, without other additives: Ethylene and propylene glycol, ethyl and methyl alcohol, glycerol, ammonia, potassium carbonate, calcium, lithium, magnesium and sodium chlorides as well as potassium acetate and potassium formate. Some laboratory measurements were made of most of the fluid types when literature values were incomplete or deemed unreliable. Methods used are briefly described and results are given. Much of the work was reported on in the Engineering Licentiate Thesis: Thermophysical properties of liquid secondary refrigerants, A Critical Review on Literature References and Laboratory Measure-ments (Melinder 1998a). That material forms the basis for the charts and tables used in the IIR-publication Thermophysical properties of liquid secondary refrigerants (Melinder, 1997). The present thesis reports on an update made since 1998, including re-view work done on two additional fluids not covered in Melinder (1998a). The thesis describes how the selection of property values results in tables and charts intended for the industry. Coefficients for poly-nomial equations are generated from these property values using a Matlab program and this material is intended as a useful tool for computer treatment. Aqueous solution of ethyl alcohol is used as example to see how this process is made. This choice of fluid can also be seen as a test of this method, as the basic thermophysical properties of aqueous solutions of ethyl alcohol present more chal-lenges than the other fluids examined. A comparison is made of a few types of aqueous solutions used as secondary working fluids for two types of applications. The first example is bedrock heat pumps and the second is cooling cabinets in a supermarket. An effort is made to see how the additive con-centration affects the thermal performance. Most aqueous solutions used as single-phase secondary fluids can also be used as ice slurry, a fluid consisting of liquid and ice where small ice crystals are produced, usually with some type of ice generator. The ice crystals are then transported to the cooling object from which heat is removed when ice crystals melt. This results in less temperature change in the cooling object and makes it also possible to reduce the volume flow rate and to use smaller pipe dimensions in the system. In order to choose a secondary fluid for ice slurry use and to make correct technical calculations of the ice slurry system there is a need to examine and evaluate thermo-physical properties and other aspects of ice and of the aqueous solution used. For dimensioning purposes it is of interest to estimate ice mass fraction and enthalpy values and enthalpy-phase diagrams can serve that purpose. This thesis presents enthalpy-phase diagrams made by author that besides isotherms contain lines with ice fraction and lines connecting enthalpies at freezing point and 1, 2, etc. to 10 K below the freezing point curve. / QC 20100609

Oxygen-diluted Combustion (OdC) technology has evolved from the concept of Excess Enthalpy Combustion and is characterized by reactants of low oxygen concentration and high temperature. Recent advances in this technology have demonstrated significant energy savings, high and uniform thermal field, low pollution, and the possibility for downsizing the equipment for a range of furnace applications. Moreover, the technology has shown promise for wider applications in various processes and power industries. The objectives of this thesis are to analyze the thermodynamic aspects of this novel combustion technology and to quantify the enhancement in efficiency and heat transfer inside a furnace in order to explore the potentials for reduced thermodynamic irreversibility of a combustion process and reduced energy consumption in an industrial furnace. Therefore, theoretical and experimental investigations were carried out. The 2nd law of thermodynamics analyses of OdC systems have been carried out for cases in which the oxidizer is either oxygen (Flameless-oxy-fuel) or air (High Temperature Air Combustion, HiTAC). The analyses demonstrate the possibilities of reducing thermodynamic irreversibility of combustion by considering an oxygen-diluted combustion process that utilizes both gas- and/or heat-recirculation. Furthermore, the results showed that an oxygen-diluted combustion system that utilizes oxygen as an oxidizer, in place of air, results in higher 1st and 2nd law efficiencies. Mathematical models for heat regenerators were developed to be designing tools for maximized heat recovery. These models were verified by heat performance experiments carried out on various heat regenerators. Furthermore, experiments were performed in a semi-industrial test furnace. It was equipped with various regenerative burning systems to establish combustion and heat transfer conditions prevailing in an industrial furnace operating based on HiTAC. The tests were carried out at seven firing configurations, two conventional and five HiTAC configurations, for direct and indirect heating systems. Measurements of energy balance were performed on the test furnace at various configurations in order to obtain the 1st law efficiency. Moreover, local measurements of temperature, gas composition, and heat fluxes in the semi-industrial test furnace were performed to find out the main characteristics of HiTAC flame and the effects of these characteristics on the heating potential, i.e., useful heating in the furnace. In the case of HiTAC, these measurements showed uniformities of chemistry, temperature, temperature fluctuation, and heat fluxes profiles. The values of fluctuations in temperature were small. The high speed jets of the fuel and air penetrated deep into the furnace. The fuel gradually disappeared while intermediate species gradually appeared in relatively high concentrations and at broader regions inside the furnace. These findings indicate: a large reaction zone, low specific combustion intensity in the flame, low specific fuel energy release, and high heat release from this large flame. In addition to the thermodynamic limitations to the maximum temperature of the Oxygen-diluted Combustion, the low specific energy release of the fuel and the high heat release from the flame to its surroundings cause this uniform and relatively moderate temperature profile in a HiTAC flame, consequently suppressing thermal-NO formation. Heat flux and energy balance measurements showed that heating potential is significantly increased in the case of HiTAC compared to that in the conventional case, implying much more energy savings than the apparent heat recovery from the heat regenerators, and consequently much less pollutants emissions. Therefore, it is certain that this large HiTAC flame emits more thermal radiation to its surroundings than the conventional flame does, in spite of the moderate-uniform temperature profile of the flame. This intense heat flux was more uniform in all HiTAC configurations, including the indirect heating configuration, than that of the conventional-air combustion configuration. / QC 20101011