Phase change phenomena of a fluid flowing in a micro channel may be exploited to make the heat exchangers more compact and energy efficient. Compact heat exchangers offer several advantages such as light weight, low cost, energy efficiency, capability of removing high heat fluxes and charge reduction are a few to mention. Phase change phenomena in macro or conventional channels have been investigated since long but in case of micro channels, fewer studies of phase change have been conducted and underlying phenomena during two-phase flow in micro channels are not yet fully understood. It is clear from the literature that the two-phase flow models developed for conventional channels do not perform well when extrapolated to micro scale. In the current thesis, the experimental flow boiling results for micro channels are reported. Experiments were conducted in circular, stainless steel and quartz tubes in both horizontal and vertical orientations. The internal diameters of steel tubes tested were 1.70 mm, 1.224 mm and the diameter of quartz tube tested was 0.781 mm. The quartz tube was coated with a thin, electrically conductive, transparent layer of Indium-Tin-Oxide (ITO) making simultaneous heating and visualization possible. Test tubes were heated electrically using DC power supply. Two refrigerants R134a and R245fa were used as working fluids during the tests. Experiments were conducted at a wide variety of operating conditions. Flow visualization results obtained with quartz tube clearly showed the presence of confinement effects and consequently an early transition to annular flow for micro channels. Several flow pattern images were captured during flow boiling of R134a in quartz tube. Flow patterns recorded during the experiments were presented in the form of Reynolds number versus vapour quality and superficial liquid velocity versus superficial gas velocity plots. Experimental flow pattern maps so obtained were also compared with the other flow pattern maps available in the literature showing a poor agreement. Flow boiling heat transfer results for quartz and steel tubes indicate that the heat transfer coefficient increases with heat flux and system pressure but is independent on mass flux and vapour quality. Experimental flow boiling heat transfer coefficient results were compared with those obtained using different correlations from the literature. Heat transfer experiments with steel tubes were continued up to dryout condition and it was observed that dryout conditions always started close to the exit of the tube. The dryout heat flux increased with mass flux and decreased with exit vapour quality. The dryout data were compared with some well known CHF correlations available in the literature. Two-phase frictional pressure drop for the quartz tube was also obtained under different operating conditions. As expected, two-phase frictional pressure drop increased with mass flux and exit vapour quality. / QC 20101206

<p>Biogas is increasingly used for fuel in for example vehicles and it´s produced in a biogas processconsisting of the steps of pretreatment, digestion and gas cleaning. The pretreatment is a method usedto increase the gas production and / or destroy pathogens. The digestion is the stage when anaerobicmicroorganisms convert bio-mass of a substrate to a raw gas containing about 65% of methane. Thegas cleaning is used to increase the methane content to about 97% so the gas can be used for motors invehicles. The biogas part of the Ekeby sewage plant in Eskilstuna is using multiple substrates. Sewagesludge is mostly used but also other substrates, like food waste. The time for processing is in average25 days before the content is taken out for drying and finally for use as cover material. The producedgas will be cleaned in a water scrubber before pressurization and after that used as fuel for vehicles.The usage of support energy in the biogas process is essentially district heating, electricity and oil. Theoverall efficiency term is the energy produced in the gas minus the supporting energy divided with theenergy from possible biogas production of the substrates. For calculation of a continuous process thefact that there is always a part of the substrates which not will be digested has to be considered.Another thing to think about is that the inserted energy as material will not be converted to gasimmediately, several days is needed. In 2009 the overall efficiency in Ekeby biogas plant was inaverage 70.5%, and the value was higher during the summer than the winter. Calculation of overallefficiency of a biogas plant will always involve some uncertainties because differences of thecomposition of the substrates, the condition of the micro-organisms, digestion of many substrates atthe same time etc.</p>

<p>Huvudsyftet med arbetet har varit att undersöka potentialen för värmedriven kylproduktion, dvs. absorptionskyla, i Linköpings energisystem. Bakgrunden är att många energibolag söker efter nya avsättningsområden för fjärrvärme pga. det överskott på värme som finns sommartid i energisystem med kraftvärme. Dessutom förväntas elpriserna fortsätta stiga då Sverige med stor sannolikhet kommer att följa resten av Europa och gå från ett energidimensionerat system till ett effektdimensionerat system. Till följd av detta blir energieffektiviserande åtgärder allt viktigare och absorptionskyla innebär att mer el kan produceras i ett system med kraftvärme, istället för att konsumeras.</p><p>Det finns två typer av absorptionskylmaskiner (ABS) tillgängliga på marknaden, antingen har de fjärrvärme eller ånga som drivmedel. Den typ av ABS som drivs av fjärrvärme lämpar sig för produktion av komfortkyla, dvs. kyla som inte behöver komma ned till så låga temperaturer. Ångdriven ABS kan däremot komma ned till lägre temperaturer, något som kan passa vid processkyla. En förutsättning för absorptionskyla är tillgång till billig värme/ånga. Tekniska Verken har tack vare avfallsförbränning tillgång till billig värme. Ångan i systemet produceras däremot idag med olja och el, något som gör det dyrare att generera absorptionskyla med hjälp av ånga.</p><p>En fallstudie utfördes på de två industrierna Linköpingsmejeriet och Swedish Meats där anslutningsmöjligheterna för absorptionskyla undersöktes. Främst behovet av processkyla har undersökts då det var betydligt större än behovet av komfortkyla. Ett antal fall med olika förutsättningar för att tillgodose dessa kylbehov till de båda industrierna har simulerats i MODEST. Utifrån de resultat som erhållits har följande slutsatser dragits.</p><p>• I dagsläget finns inte tillräckligt med ångproduktion i systemet för att tillgodose både det befintliga ångbehovet samt den mängd ånga som behövs för att framställa kylan.</p><p>• En investering i nya biopannor till ett kraftvärmeverk kan ge tillräcklig mängd billig ånga och värme för att ge lönsamhet i värmedriven kylproduktion.</p><p>• Koldioxidutsläppen, lokala såväl som globala, minskar som en följd av övergång från el-kompressorer till absorptionskylmaskiner. En investering i nya biopannor skulle minska utsläppen ytterligare, då fossilt bränsle ersätts.</p><p>• En investering i en litiumbromid absorptionskylmaskin är inte lönsam vid en så pass liten efterfråga som har varit aktuellt i de undersökta fallen.</p> / <p>The main purpose of this thesis has been to look in to the potential of a production of district cooling using heat as the source of power, i.e. absorptions cooling, in the energy system of Linköping. In the light of the fact that many energy companies are looking for new markets for district heating due to the surplus of heat in the summertime in an energy system with CHP (Combined Heat and Power). Furthermore, the price on electricity is expected to continue to rise since Sweden is most likely to follow Europe’s lead and embrace a power dimensioned energy system. As a result of that transition, energy efficient measures will be more important and absorption cooling implies that more electricity can be produced, instead of consumed, in a CHP system.</p><p>There are two different types of absorption cooling machines available in the market, with either district heating or steam as the source of power. A machine using district heating as the source of power is most suitable to produce comfort cooling i.e. the cold does not need to attain such low temperatures. A steam driven absorption cooling machine is able to attain the very low temperatures needed for cooling used in the processing industry. A condition for absorption cooling is the access to low-cost heat/steam. Tekniska Verken (an energy company) has due to waste incineration access to low-cost heat. The steam in the energy system is produced with oil and electricity, which makes it more expensive to generate absorption cooling with steam as the power source.</p><p>A casestudy was preformed at two industries in Linköping, Linköpingsmejeriet and Swedish Meats, where the possibility for connection of district cooling was examined. Mainly the cooling needed in the processing industry has been examined as this is need is considerably larger than the need for comfort cooling. A number of cases with different conditions for producing district cooling have been simulated in MODEST. The following conclusions have been drawn based on the results of the simulations.</p><p>• In the energy system of today there is not enough steam production to fulfil both the current need for steam and the amount of steam needed for cooling production.</p><p>• An investment in new CHP-plants using biomass fuels will generate enough heat and steam to be profitable for cooling production using heat as a source of power.</p><p>• The emission of carbon dioxide will decrease as a result of the transmission from compression cooling to absorption cooling. The emission will decrease further if an investment in new CHP plants with biomass fuels is carried out. This will then replace the use of fossil fuels.</p><p>• An investment in lithium bromide absorptions cooler will not be profitable with such a small demand as the one in question.</p>

<p>The aim of this project is to make an energy flow survey of Ljusdal’s municipality. The reason for the energy flow survey is to discover possibilities to utilize and refine the energy resources locally, and use the information from this survey as a base for further discussions about the energy situation in Ljusdal’s municipality. As it is today the raw material is transported to other municipalities for processing and then bought back, e.g. biomass is transported to other municipalities where they make pellets which are sold back to consumers in Ljusdal’s municipality. A local upgrading of the raw material will probably create more job opportunities in the municipality and it will probably also lead to a higher profit than just selling the raw material. The target groups for this study are the local (and regional) politicians and entrepreneurs, primarily in Ljusdal but also in other similar municipalities. Mainly bioenergy is handled in this thesis. Other energy sources e.g. hydroelectricity is handled just briefly, flows and use of electricity are described briefly for different parts of the municipality and types of consumers. To perform the energy flow survey, information about now used, and possible future, energy resources was collected in order to find out the energy quantities used per year, for different users, and the energy flows. Unexploited energy sources, and energy sources that have the potential to be increased, like forest and arable land was also included. Investigations about the wind potential are also carried out. The energy use of the consumers, divided into energy carriers, is mapped. Larger companies and institutions, particularly those with energy related business are asked about their future plans. Energy suppliers are also asked where they buy and sell energy in order to make an energy flow survey. The energy needs for different types of buildings were also considered in this energy flow survey. In order to do that, information about the numbers of buildings in the municipality and also the average energy usage, for different types of buildings e.g. apartments and single family houses, are collected from different sources. The flows of bioenergy across the municipality border are also investigated in order to be able to see where it comes from and where it goes. Nearby municipalities, projects nearby Ljusdal’s municipality, that may have an impact in the field of energy in Ljusdal’s municipality are also briefly handled. The energy flows, in and out of the municipality, were put into maps from the municipality’s Geographic Information System (GIS) in order to get a good overview of the energy flow, supply and use. Based on the gathered information, project ideas are suggested, and calculations are done to determine if biogas production, from household waste and sludge, could be a better option than today’s waste management where the waste is being transported to a nearby municipality for incineration, a service that Ljusdal’s municipality also have to pay for. The results from the calculations show that the total amount of energy that could be extracted from the annual produced biogas would reach about 1.9 GWh. The biogas could e.g.be used as a fuel in the district heating plants in the municipality. By using locally produced products a decreased import of energy carriers, e.g. light fuel oil, would be expected.</p><p>The conclusions that could be drawn from this study are that a lot of biomass is produced in Ljusdal’s municipality, which is mainly exported in the form as raw material. Large amounts of hydroelectricity is produced in Ljusdal’s municipality, about 60% of the electricity is being exported. Wind mappings show that there are some areas of national interest for electricity production through wind power in the municipality. A deregulated European electricity market will probably lead to an increased electricity price, this in combination with the green certificate would lead to a more profitable electricity</p><p>production through wind power and areas that are not of national interest at present could probably be of national interest in the future. There are also a large potential to increase the amount of biomass from the forestry remainings. Another potential energy source is the arable land where it probably would be possible to grow e.g. hemp for an energy conversion purpose. In Ljusdal’s municipality, there are possibilities in the field of energy which no one takes advantage of at present.</p> / <p>Syftet med detta projektarbete är att kartlägga energiflödet inom-, samt till och från Ljusdals kommun, i första hand bioenergi men även andra energiformer som t.ex. elektricitet behandlas översiktligt. Anledningen till denna energiflödesanalys är att upptäcka möjligheter att bearbeta och förädla biomassan lokalt. I dagens läge lämnar stora mängder av råmaterial kommunen för förädling utanför kommunens gränser, detta leder till förlorade arbetstillfällen i kommunen. Ett exempel på detta är att råmaterial i form av sågspån transporteras från Ljusdals kommun till en annan kommun där sågspånen förädlas till pellets som i sin tur säljs tillbaka till konsumenter i Ljusdals kommun. En lokal förädling av biomassan skulle förmodligen kunna leda till nya arbetstillfällen inom kommunens gränser samt en högre avkastning än att bara sälja råmaterialet obearbetat. Målgruppen för denna studie är lokala och regionala politiker och entreprenörer, i första hand i Ljusdals kommun, men också i liknande glesbygdskommuner med stora arealer skog och andra former av biobränslen. För att genomföra denna energiflödesanalys samlades information, angående i nuläget använda samt framtida energikällor, in med avsikt att uppskatta de kvantiteter, och olika typer av energi som omvandlas och används årligen av olika typer av konsumenter. Denna information tillhandahölls av bl.a. statistiska central byrån – SCB, kommunens energirådgivare, energibolag, större energikrävande företag samt bostads företag. Antalet enfamiljshus och flerfamiljs hus i kommunen samt antalet boende i kommunen kartlades för att kunna beräkna, enligt schabloner, de energimängder som förbrukades årligen i bostadssektorn. Även transport- och industrisektorn undersöktes med avseende på dess energianvändning.</p><p>Flödet av biomassa i kommunen samt över dess gränser analyserades med avsikt på att klargöra vilka mängder som lämnar, respektive stannar kvar inom kommunen. Även projekt i närliggande kommuner analyserades översiktligt för att se om de hade någon nämnbar inverkan på Ljusdals kommuns energiproduktion1 och energianvändning. Slutsatserna som kan dras från denna analys är i korthet att stora mängder av biomassa produceras inom Ljusdals kommuns gränser och transporteras bort i form av råmaterial, som förädlas utanför kommunens gränser. Ett sätt att eventuellt skapa fler jobbtillfällen samt se till att en större del av vinsten från biomassan stannar kvar inom kommunens gränser är att lokalt bearbeta biomassan. Inom kommunen produceras också en stor del vattenkraft där ungefär 60 % exporteras och resterande används inom kommunen, möjlighet till utökad elproduktion bör vara möjlig genom byggnation av vindkraftsparker eftersom det finns områden som är av nationellt intresse för vindkraftsproduktion. Något mer som talar för en ökad lönsamhet inom elproduktion via vindkraft är den avreglerade Europeiska elmarknaden som förmodligen kommer att leda till ökade elpriser, en annan faktor är elcertifikaten, som erhålls för varje MWh producerad med förnyelsebara källor t.ex. vindkraft eller biomassa eldat kraftvärmeverk. Biogas motsvarande ungefär 2 GWh årligen bör också kunna utvinnas ur sopor, gödsel från bondgårdar och energigrödor. Detta kräver dock investeringar i rötningsanläggningar och ytterligare utredningar angående detta föreslås göras. En markant ökad produktion av biobränsle från skogsbruket bör också vara möjlig.</p><p>Den globala ökningen av invånare i kombination med en strävan efter minskad produktion av fossila bränslen resulterar i en ökad efterfrågan av förnyelsebara bränslen, denna ökade efterfrågan leder i sin tur till ett ökat pris för dessa bränslen. Dessutom har ett antal länder skrivit på Kyoto avtalet, vilket innebär i korthet att dessa länder måste minska sina koldioxidutsläpp. Dessa faktorer kan tolkas som indikationer på att det kommer att bli en ökad användning av biobränslen. Problemet med detta scenario är att, aven i ett nationellt perspektiv, mängden av tillgänglig biomassa är begränsad om den skulle utgöra baslasten för energiproduktionen. Detta faktum öppnar nya möjligheter för kommuner med en låg befolkningstäthet i kombination med stora skogsarealer. Ljusdals kommun är en glest befolkad kommun med ungefärligen 19 400 invånare, det finns 10 100 bostäder i kommunen varav 3 700 är lägenheter och resterande är enfamiljshus. Den totala arealen av kommunen uppgår till 5 640 km2, befolkningstätheten uppgår till fyra invånare per kvadrat kilometer. Arealen per capita i kommunen är väldigt hög, vilket innebär att det finns stora mängder biomassa tillgänglig då stordelen av kommunen består av skog. Syftet med denna analys är att få en bättre översikt över dagens situation inom detta område. En bättre översikt skulle kunna hjälpa politiker och entreprenörer att se nya möjligheter inom detta område, vilket skulle kunna innebära fler arbetstillfällen inom kommunen.</p>

<p>Arvika Fjärrvärme AB, a district heating company from Arvika, today cover 74 % of their total energy production with biofuel wich runs a 16 MW bioler giving process water at saturated liquid state.</p><p>In recent years Vaporel AB has introduced a new tecnique that gives an external generation of steam after boilers. The concept is built on an adiabatic pressure drop of the saturated liquid in a so called Flashbox which makes a small part of the liquid to evaporate. The generated steam is lead into a turbine where electricity is in a conventional manner.</p><p>The purpose with this rapport was to do a basic study for the specific system at Arvika where it’s possible to see the potential production of electricity that follows an installation of a flasbox.</p><p>The final goal was to introduce an economic analysis of a flashox installation at given conditions.</p><p>To reach our goals we have created a model in Excel where we used the given conditions at Arvika Fjärrvärme to do our calculations. The model has been tested at three different states, of process water returning to potboiler, to be able to decide the optimal operation for the system at present.</p><p>The studies have resulted in a pressure of the processwater at 14,5 bar (at) and a pressuredrop to 9,5 bar (at) in the flashbox. The condenser pressure is set to 0,5 bar (at) what is equal to 81 ˚C. Energy to the district heating net is produced in the condenser and heat exchanger.</p><p>The result of our calculations clearly shows that to reach the highest turbine-efficiency as possible and gain the largest profit the highest process-waterflow possible should be used.</p><p>That means 70 kg/s after present conditions.</p><p>At the highest boiler efficiency the turbine will produce 694 kW. At this state the water that returns to the boiler will be at temperature 148 ˚C (14, 5 bar).</p><p>Totally during a year the production of electric energy could reach 2, 47 GWh/year. The energy used by the pumps will increase with 0,21 GWh over the year at that state.</p><p>Included all economic factors this will generate a profit of 0, 97 million (SEK)/year.</p><p>To make an installation of a flashbox system more profitable an increased generation of electricity have to be made. This could be done by an installation of new pumps to be able to run the process-water at a larger flow to increase the amount of steam made in the flashbox.</p> / <p>Arvika fjärrvärme producerar idag 74% av sitt värmeunderlag via en hetvattenpanna som drivs med biobränsle och har en maxeffekt på 16 MW.</p><p>På senare år har företaget Vaporel AB introducerat en ny teknik på marknaden som ger en extern ångproduktion efter hetvattenpannor.</p><p>Konceptet är byggt på en trycksänkning som medför att delar av det mättade vattnet förångas efter att ha letts in i en så kallad flashbox. Efter flashboxen äntrar ångan en turbin där el produceras på konventionellt vis.</p><p>Syftet med denna rapport har varit att ta fram en grundläggande studie för Arvikas specifika system där det är möjligt att se den potentiella elproduktionen vid en flashboxinstallation.</p><p>Det slutgiltiga målet med rapporten har varit att kunna presentera en lönsamhetsbedömning för en flashboxinstallation vid givna driftfall.</p><p>För att kunna uppfylla uppsatta mål har en Excelmodell konstruerats där beräkningar utförts efter givna förutsättningar, detta utefter tre olika driftfall för att kunna fastställa den mest optimala driften för systemet i dagsläget.</p><p>Studierna har lett fram till att vi har kunnat fastställa ett maximalt tryck efter pannan på 14,5 bar (at) samt en trycksänkning över flashboxen till 9,5 bar. Kondensortryck efter turbinen har satts till 0,5 bar(a) vilket ger en kondensations temperatur motsvarande 81 ˚C. Energi till att värma fjärrvärmevattnet tas via kondensorn samt en värmeväxlare.</p><p>Resultatet av våra beräkningar visar tydligt att vi för att nå en så hög turbineffekt som möjligt och därmed en större lönsamhet skall ha ett så högt processvattenflöde som tillåts, enligt dagens förutsättningar 70 l/s.</p><p>Vid högsta panneffekten kommer turbinen att ge 694 kW, enligt Excelmodellen, vid en returtemperatur till pannan satt till 148 ˚C.</p><p>Sammanlagt under året, med Arvikas varaktighetsdiagram som grund, kommer vi att kunna producera 2,47 GWh el/år varav pumparna kommer att kräva 0,21 GWh el extra per år.</p><p>Med alla ekonomiska faktorer inräknade så kommer detta att ge en vinstkalkyl på 0,97 miljoner /år.</p><p>För att kunna göra dessa installationer lönsamma krävs att vi ökar elproduktionen och därmed den årliga vinsten, detta skulle kunna göras i och med installation av nya pumpar för att uppnå ett större flöde i pannkretsen.</p><p>Vidare bör en studie göras för att bedöma lönsamheten gällande en ombyggnad av rökgaskondenseringen för att kunna klara en större effekt och därmed kunna använda högre returtemperaturer till biopannan. Detta skulle generera ett högre genomsnittligt flöde över året.</p>

<p>The energy use in a workshop company has been examined in this work in order to find areas for energy efficiency improvement. The combined oil and electricity heating in the company were compared with other alternative heating systems including cooling of the premises in following combinations:</p><ol><li>Ground source heat pump for heating and cooling</li><li>District heating and absorption cooling</li><li>District heating and low temperate surface water cooling</li></ol><p>Energy use, operation costs and carbon dioxide emissions were calculated for the current heating systems and the three alternatives including cooling. The ground source heat pump for heating and cooling decreases bought energy with 34 MWh annually compared to current heating only. The district heating and low temperate surface water cooling has the largest reduction of operation cost and carbon dioxide. The operation cost decreases with 42 kSEK and the carbon dioxide with 43 metric ton CO₂ annually. The differences between the alternatives were smaller concerning the operation costs. The ground source heat pump alternative had smaller reductions of carbon dioxide than the other two alternatives with district heating.</p><p>An alternative heating and cooling system can also lead to alternative energy use. The choice is between electrical or heat energy. A weighting can be done to evaluate the energy use for heating on basis of how much energy is needed in order to generate the energy the end user buys. A 2.5 factor for electrical energy entails the alternative with district heating and low temperate surface water cooling gets the lowest heating and cooling energy in comparison.</p><p>An inventory of the lighting was also done. The company has already an energy effective lighting but yet another saving of 2 MWh can be done annually without replacement of armatures.</p><p>Finally, the operation time of the compressor was calculated with a mean value of 11 hours per day. The compressor delivers pressure air to machines and tools. There can be a great demand for pressure air in the workshop but the operation time can also be an indication of leakage in the air net.</p>

The energy use in a workshop company has been examined in this work in order to find areas for energy efficiency improvement. The combined oil and electricity heating in the company were compared with other alternative heating systems including cooling of the premises in following combinations: Ground source heat pump for heating and cooling District heating and absorption cooling District heating and low temperate surface water cooling Energy use, operation costs and carbon dioxide emissions were calculated for the current heating systems and the three alternatives including cooling. The ground source heat pump for heating and cooling decreases bought energy with 34 MWh annually compared to current heating only. The district heating and low temperate surface water cooling has the largest reduction of operation cost and carbon dioxide. The operation cost decreases with 42 kSEK and the carbon dioxide with 43 metric ton CO2 annually. The differences between the alternatives were smaller concerning the operation costs. The ground source heat pump alternative had smaller reductions of carbon dioxide than the other two alternatives with district heating. An alternative heating and cooling system can also lead to alternative energy use. The choice is between electrical or heat energy. A weighting can be done to evaluate the energy use for heating on basis of how much energy is needed in order to generate the energy the end user buys. A 2.5 factor for electrical energy entails the alternative with district heating and low temperate surface water cooling gets the lowest heating and cooling energy in comparison. An inventory of the lighting was also done. The company has already an energy effective lighting but yet another saving of 2 MWh can be done annually without replacement of armatures. Finally, the operation time of the compressor was calculated with a mean value of 11 hours per day. The compressor delivers pressure air to machines and tools. There can be a great demand for pressure air in the workshop but the operation time can also be an indication of leakage in the air net.

Biogas is increasingly used for fuel in for example vehicles and it´s produced in a biogas processconsisting of the steps of pretreatment, digestion and gas cleaning. The pretreatment is a method usedto increase the gas production and / or destroy pathogens. The digestion is the stage when anaerobicmicroorganisms convert bio-mass of a substrate to a raw gas containing about 65% of methane. Thegas cleaning is used to increase the methane content to about 97% so the gas can be used for motors invehicles. The biogas part of the Ekeby sewage plant in Eskilstuna is using multiple substrates. Sewagesludge is mostly used but also other substrates, like food waste. The time for processing is in average25 days before the content is taken out for drying and finally for use as cover material. The producedgas will be cleaned in a water scrubber before pressurization and after that used as fuel for vehicles.The usage of support energy in the biogas process is essentially district heating, electricity and oil. Theoverall efficiency term is the energy produced in the gas minus the supporting energy divided with theenergy from possible biogas production of the substrates. For calculation of a continuous process thefact that there is always a part of the substrates which not will be digested has to be considered.Another thing to think about is that the inserted energy as material will not be converted to gasimmediately, several days is needed. In 2009 the overall efficiency in Ekeby biogas plant was inaverage 70.5%, and the value was higher during the summer than the winter. Calculation of overallefficiency of a biogas plant will always involve some uncertainties because differences of thecomposition of the substrates, the condition of the micro-organisms, digestion of many substrates atthe same time etc.

Conducting polymers (CP) have received great attention in both academic and industrial areas in recent years. They exhibit unique characteristics (electrical conductivity, solution processability, light weight and flexibility) which make them promising candidates for being used in many electronic applications. Recently, there is a renewed interest to consider those materials for thermoelectric generators that is for energy harvesting purposes. Therefore, it is of great importance to have in depth understanding of their thermal and electrical characteristics. In this diploma work, the thermal conductivity of PEDOT:PSS is investigated by applying 3-omega technique which is accounted for a transient method of measuring thermal conductivity and specific heat. To validate the measurement setup, two benchmark substrates with known properties are explored and the results for thermal conductivity are nicely in agreement with their actual values with a reasonable error percentage. All measurements are carried out inside a Cryogenic probe station with vacuum condition. Then a bulk scale of PEDOT:PSS with sufficient thickness is made and investigated. Although, it is a great challenge to make a thick layer of this polymer since it needs to be both solid state and has as smooth surface as possible for further gold deposition. The results display a thermal conductivity range between 0.20 and 0.25 (W.m-1.K-1) at room temperature which is a nice approximation of what has been reported so far. The discrepancy is mainly due to some uncertainty about the exact value of temperature coefficient of resistance (TCR) of the heater and also heat losses especially in case of heaters with larger surface area. Moreover, thermal conductivity of PEDOT:PSS is studied over a wide temperature band ranging from 223 - 373 K.

Huvudsyftet med arbetet har varit att undersöka potentialen för värmedriven kylproduktion, dvs. absorptionskyla, i Linköpings energisystem. Bakgrunden är att många energibolag söker efter nya avsättningsområden för fjärrvärme pga. det överskott på värme som finns sommartid i energisystem med kraftvärme. Dessutom förväntas elpriserna fortsätta stiga då Sverige med stor sannolikhet kommer att följa resten av Europa och gå från ett energidimensionerat system till ett effektdimensionerat system. Till följd av detta blir energieffektiviserande åtgärder allt viktigare och absorptionskyla innebär att mer el kan produceras i ett system med kraftvärme, istället för att konsumeras. Det finns två typer av absorptionskylmaskiner (ABS) tillgängliga på marknaden, antingen har de fjärrvärme eller ånga som drivmedel. Den typ av ABS som drivs av fjärrvärme lämpar sig för produktion av komfortkyla, dvs. kyla som inte behöver komma ned till så låga temperaturer. Ångdriven ABS kan däremot komma ned till lägre temperaturer, något som kan passa vid processkyla. En förutsättning för absorptionskyla är tillgång till billig värme/ånga. Tekniska Verken har tack vare avfallsförbränning tillgång till billig värme. Ångan i systemet produceras däremot idag med olja och el, något som gör det dyrare att generera absorptionskyla med hjälp av ånga. En fallstudie utfördes på de två industrierna Linköpingsmejeriet och Swedish Meats där anslutningsmöjligheterna för absorptionskyla undersöktes. Främst behovet av processkyla har undersökts då det var betydligt större än behovet av komfortkyla. Ett antal fall med olika förutsättningar för att tillgodose dessa kylbehov till de båda industrierna har simulerats i MODEST. Utifrån de resultat som erhållits har följande slutsatser dragits. • I dagsläget finns inte tillräckligt med ångproduktion i systemet för att tillgodose både det befintliga ångbehovet samt den mängd ånga som behövs för att framställa kylan. • En investering i nya biopannor till ett kraftvärmeverk kan ge tillräcklig mängd billig ånga och värme för att ge lönsamhet i värmedriven kylproduktion. • Koldioxidutsläppen, lokala såväl som globala, minskar som en följd av övergång från el-kompressorer till absorptionskylmaskiner. En investering i nya biopannor skulle minska utsläppen ytterligare, då fossilt bränsle ersätts. • En investering i en litiumbromid absorptionskylmaskin är inte lönsam vid en så pass liten efterfråga som har varit aktuellt i de undersökta fallen. / The main purpose of this thesis has been to look in to the potential of a production of district cooling using heat as the source of power, i.e. absorptions cooling, in the energy system of Linköping. In the light of the fact that many energy companies are looking for new markets for district heating due to the surplus of heat in the summertime in an energy system with CHP (Combined Heat and Power). Furthermore, the price on electricity is expected to continue to rise since Sweden is most likely to follow Europe’s lead and embrace a power dimensioned energy system. As a result of that transition, energy efficient measures will be more important and absorption cooling implies that more electricity can be produced, instead of consumed, in a CHP system. There are two different types of absorption cooling machines available in the market, with either district heating or steam as the source of power. A machine using district heating as the source of power is most suitable to produce comfort cooling i.e. the cold does not need to attain such low temperatures. A steam driven absorption cooling machine is able to attain the very low temperatures needed for cooling used in the processing industry. A condition for absorption cooling is the access to low-cost heat/steam. Tekniska Verken (an energy company) has due to waste incineration access to low-cost heat. The steam in the energy system is produced with oil and electricity, which makes it more expensive to generate absorption cooling with steam as the power source. A casestudy was preformed at two industries in Linköping, Linköpingsmejeriet and Swedish Meats, where the possibility for connection of district cooling was examined. Mainly the cooling needed in the processing industry has been examined as this is need is considerably larger than the need for comfort cooling. A number of cases with different conditions for producing district cooling have been simulated in MODEST. The following conclusions have been drawn based on the results of the simulations. • In the energy system of today there is not enough steam production to fulfil both the current need for steam and the amount of steam needed for cooling production. • An investment in new CHP-plants using biomass fuels will generate enough heat and steam to be profitable for cooling production using heat as a source of power. • The emission of carbon dioxide will decrease as a result of the transmission from compression cooling to absorption cooling. The emission will decrease further if an investment in new CHP plants with biomass fuels is carried out. This will then replace the use of fossil fuels. • An investment in lithium bromide absorptions cooler will not be profitable with such a small demand as the one in question.