The building sector accounted for around a fourth of the total energy usage in Sweden in year 2010 (Energimyndigheten, 2012). Therefore it has become very interesting to achieve a lower energy usage in residential buildings. One way to achieve that is to build so called passive houses. By being very well insulated and have low leakage through the walls, they can reduce the energy usage for heating with a substantial amount. The first passive house was built during the 90’s in Germany; and in Sweden the first passive house was built in Gothenburg 2001. Both Sweden and EU have goals to reduce the overall energy usage and greenhouse emission by 2020 and 2050. The concept of the passive house is one way to achieve the goals. In short, the concept of the passive house in Sweden is: The air tightness for the walls should be tighter than 0,3 l/m2,s at 50 Pa overpressure The heat loss factor must not exceed 15 W/m2 Atemp for climate zone III The delivered energy must not exceed 50 kWh/m2 Atemp,year for purely non electrically heated systems in climate zone III The average u-value for windows should be as highest 0,8 W/m2,K. The term primary energy is a term that is frequently used in the EU when talking about energy usage. Apart from the above mentioned criteria, passive houses in Germany must also use less than 120 kWh/m2Atemp,year in primary energy. Primary energy usage for the passive houses is calculated by multiplying the energy usage with the respective primary energy factor. The primary energy factors were set to be the following: Electricity mix – 2,7 District heating mix – 0,79 District heating from waste – 0,04 Electricity from wind power – 0,05 The results show that the passive houses in Trettondagen and Oxtorget were the only ones that passed the German limit of 120 kWh/m2Atemp,year. The low energy usage in Trettondagen could be explained by the fact that the input values for calculating primary energy usage were simulated and not measured. Moreover, the passive house in Trettondagen was connected to the district heating from waste, which has a very low primary energy factor. The passive houses in Oxtorget were not connected to district heating and relied only on solar panels and heat recovery in the ventilation unit. An electric heater was installed in both the ventilation unit and the storage tank to provide extra heating. What set the passive house in Oxtorget apart from the others was that the electricity used in the houses only came from wind power. The low primary energy factor for wind power contributed to the extremely low primary energy of Oxtorget. The domestic electricity was relatively high in most of the passive houses, a reason to why they had problem with passing the German limit. One house had low enough domestic electricity usage to possibly pass the limit if the source of energy for heating was changed. It was the passive house in Falkenberg which was connected to district heating from biofuels (1,035). By switching to district heating from waste instead, the passive house in Falkenberg will then pass the limit. Primary energy usage for the passive houses in Oxtorget was also calculated with one half from electricity mix and the other half from electricity from wind power. Despite a large increase in primary energy, the passive houses still passed the limit. The passive house in Trettondagen was also calculated with switching district heating from waste to district heating mix. The primary energy increased a little bit but remained under the limit. The conclusion form this thesis showed that certain passive houses in Sweden were able to fall beneath the German limit for primary energy. One obstacle could be the high domestic electricity that has to decrease, perhaps by informing and involving the residents. Another problem is the absence of proper framework for calculating primary energy. There are some calculations mentioned in FEBY that resembles calculations for primary energy. The definitions though are too unclear and thus difficult to compare with the German standard.

Global concerns of climate change, increased greenhouse gas emissions and security of energy supply have accelerated the search for alternative energy sources both indeveloped and developing countries. Developing countries are now embracingutilization of biogas as a renewable energy option to meet some of their cooking andlighting needs. In Uganda, despite the introduction of biogas in the 1950’s, thetechnology has not received considerable acceptance and as a result its penetrationhas remained relatively low.  Several installed biogas plants have failed and those working are not working to theexpectation of the technicians and their owners. This research presents results of thestudy carried out to establish the performance of farm based biogas systems so as toassess the challenges faced by the users and to identify the possible causes of failurefor the non-operational systems.  A survey of 144 biogas plants was carried out after which performance monitoring ofselected digesters in the districts of Luwero, Kampala, Wakiso, Mbale, Jinja andMukono. It was found that 55% of the surveyed  biogas  plants  were  not  operational and  others  not  performing  to  the  users expectations. Most of the plants monitoredwere operating in the temperature range of 18°C-25°C with the gas quality rangingbetween 50-60% methane. Most digesters showed evidence of high organic loadingrates indicated by traces of biogas at the expansion chamber. The identified  causes of  failure  were  poor  system  maintenance, poor workmanship during constructionworks, poor  operation  practices, availability of other cheap fuel alternatives, lazinessand lack of interest amongst  the users, lack of alternative sources of feedstock andsystem blockages. Furthermore, there is need to sensitize people on the need for using alternativesources of energy such as biogas and improved cooking stoves for fuel saving as mostof them use wood and charcoal as supplementary fuels. This would reduce globalwarming through reduced deforestation and bring about environmental sustainabilityas a whole.

In this report we discuss the use of k-ε RANS (Reynolds-averaged Navier-Stokes equations) turbulence model for wind turbine applications. This model has been implemented in the new wind turbine wake CFD code that is being developed at ECN. Simulations of the wind turbine test site EWTW are compared with measurements conducted between 2005 and 2009 and with FarmFlow, ECN's current wind turbine wake code. Based on the results the uncertainties in the current approach are highlighted and areas for possible improvement are discussed.

The current energy scenario in the developing nations with abundant sun resource (e.g. southern Mediterranean countries of Europe, Middle-East & North Africa) relies mainly on fossil fuels to supply the increasing energy demand. Although this long adopted pattern ensures electricity availability on demand at all times through the least cost proven technology, it is highly unsustainable due to its drastic impacts on depletion of resources, environmental emissions and electricity prices. Solar thermal Hybrid power plants among all other renewable energy technologies have the potential of replacing the central utility model of conventional power plants, the understood integration of solar thermal technologies into existing conventional power plants shows the opportunity of combining low cost reliable power and Carbon emission reduction. A literature review on the current concentrating solar power (CSP) technologies and their suitability for integration into conventional power cycles was concluded, the best option was found be in the so called Integrated solar combined cycle systems (ISCCS); the plant is built and operated like a normal combined cycle, with a solar circuit consisting of central tower receiver and heliostat field adding heat to the bottoming Rankine cycle. A complete model of the cycle was developed in TRNSYS simulation software and Matlab environment, yearly satellite solar insolation data was used to study the effect of integrating solar power to the cycle throw-out the year. A multi objective thermo economic optimization analysis was conducted in order to identify a set of optimum design options. The optimization has shown that the efficiency of the combined cycle can be increased resulting in a Levelized electricity cost in the range of 10 -14 USDcts /Kwhe. The limit of annual solar share realized was found to be around 7 % The results of the study indicate that ISCCS offers advantages of higher efficiency, low cost reliable power and on the same time sends a green message by reducing the environmental impacts in our existing power plant systems.

This thesis is a collaboration between Siemens Industrial Turbomachinery(SIT) and Royal Institute of Technology(KTH). It is aimed to study and compare the outputs of two different computational approaches in axial gas turbine design procedure with the data obtained from experimental work on a test turbine. The main focus during this research is to extend the available test databank and to further understand and investigate the turbine stage efficiency, mass flow parameters and reaction degree under different working conditions. Meanwhile the concept and effect of different loss mechanisms and models will be briefly studied.  The experimental part was performed at Heat and Power  Technology department on a single stage test turbine in its full admission mode. Three different pressure ratios were tested. For the medium pressure ratio a constant temperature anemometry (CTA) method was deployed in two cases, with and without turbulence grid, to determine the effect of free-stream turbulence intensity on the investigated parameters. During the test campaign the raw gathered data was processed with online tools and also they served as boundary condition for the computational codes later.  The computational scope includes a one-dimensional design approach known as mean-line calculation and also a two-dimensional method known as throughflow calculation. An in-house SIT software, CATO, generated the stage geometry (vane, blade and the channel) and then two other internal computational codes, MAC1 and BETA2, were employed for the one-dimensional and two-dimensional computations respectively. It was observed that to obtain more accurate mass flow predictions a certain level of channel blockage should be implemented to represent the boundary layer development and secondary flow which is typically around 2%. The codes are also equipped with two options to predict the friction loss: One is a more empirical correlation named as the Old approach in SIT manuals and the other works based on allocation of boundary layer transition point, named as BL in the present thesis. Simulations were done by use of both approaches and it turned out that the latter works more accurately if it is provided with appropriate transition point and blockage estimation.  The measured data also suggests the idea that the transition point of the vane and blade is not affected by a change in turbulence intensity at least up to 6% in the tested Reynolds numbers, . Amongst different solutions the one which used BL approach and constant transition point (while the turbulence intensity changed) managed to predict this behavior. Also it was investigated and revealed that the codes inherently predict poor results in off-design loadings which is mainly due to positive incidence angle in addition to high spanwise gradient of the flow parameters.

Ett allt vanligare sätt att ta hand om det avfall som produceras i samhället är att förbränna det för att producera el och fjärrvärme. Detta gör Bodens Energi AB vid deras värmeverk som har flera avfallseldade pannor. Detta arbete fokuserar på deras största avfallseldade ångpanna där det uppstår problem till följd av askhanteringen. Den heta askan som kommer från pannan kyls ned i en asktransportör som är vattenfylld. Detta gör att vattnet blir varmt och samtidigt bildas det ånga som sedan bidrar till dålig arbetsmiljö då underhåll ska utföras på asktransportören. Den dåliga arbetsmiljön uppstår till följd av de skadliga ämnen som finns i vattnet, och därmed ångan, till följd av avfallet. Speciellt är det höga halter av klorid och sulfat men även andra skadliga ämnen. Den värme som finns tillgänglig i asktransportören utnyttjas inte idag och förslaget från företaget är att använda det till markvärme som kan smälta snö och is i en tipphall. I tipphallen är det idag problem för lastbilar att lasta av avfallet till följd av isbildning som uppstår i samband med ett sluttande plan. I det här arbetet har två lösningar undersökts med målet att sänka temperaturen på vattnet i asktransportören, baserat på företagets önskemål, och därmed minska ångbildningen. Lösningarna ska klara av den aggressiva miljö som förekommer i vattnet och ska vara kompatibla med markvärme som installeras i en tipphall. Utöver en beskrivning av lösningarna har även en analys av mass- och energiflöden gjorts för vattnet i asktransportören som underlag till beräkningarna. Den ena lösningen använder sig av plaströr som är formade som U och som sänks ned i vattnet i transportören. För den lösning visade resultatet att värmeöverföringen var för låg. För den andra lösningen, då den heta ytan på utsidan av transportören kyls med vatten, visar resultatet på att det är ett fungerade koncept. Lösningen innebär att kanaler skapas där vatten får passera den heta ytan flera gånger. Med denna lösning uppnås den sökta utloppstemperaturen på 45 °C och effekten på 250 kW för markvärmen. Samtidigt visar den framtagna energibalansen att värmflödet från transportörens väggar till vattnet i kanalerna är för liten. Den största energin finns i ångan som befinner sig i en annan del av transportören. Till följd av osäkerheter i energibalansen i form av massflöden och temperaturer är det inte möjligt att beräkna temperatursänkningen för vattnet. Men även om temperaturen på vattnet i transportören kan sänkas kommer ångbildningen inte att minska. Därför är rekommendationen att inte använda sig av lösningen med kanalerna. Framtida arbeten bör istället fokusera på att kondensera ångan genom att skapa kalla ytor på insidan av transportören.

Genom att kartlägga smältugnarna och dess kylvattensystem inom Åkers Sweden AB har en studie genomförts för att analysera vilken potential det finns till att ytterligare återvinna överskottsenergi. Detta har genomförts för att uppfylla de av Sverige ställda miljö- och energi-mål till år 2030 som dels handlar om att vi behöver energieffektivisera våra processer och tillföra mindre energi för att uppnå samma resultat som tidigare. Uppdraget är genomfört på uppdrag av Åkers Ledningsgrupp som önskar förstå om det finns tekniska och ekonomiska förutsättningar att starta upp ett projekt för att investera i ett energilager. Överskottsenergi som idag inte kan tillvaratas kyls bort med sjövatten vilket kan betraktas som ett rent energislöseri. Resultatet påvisar att det finns en potential till att återvinna ytterligare 2 GWh överskottsenergi vilka är möjliga att lagra i ett energilager till en investeringskostnad på 21 MSEK.

In developing countries about 40 % of the food-waste is due to post-harvest losses, such as improper storage. The Zeer-pot is an evaporative cooler, which cools the inside by convective heat transfer, and can be used to keep fruits and vegetables fresh longer. This is typically convenient in hot rural areas without access to electricity and is more efficient in non-humid areas. This study will investigate if there is a correlation between the temperature decrease inside the pot and the wind velocity, how the efficiency of the Zeer-pot is affected by hanging it in the air to additionally expose the underside to the airflow and also how the efficiency is affected from glazing of the inner pot, to prevent the food from getting damaged from high humidity. It will also consider the feasibility of combining the Zeer-pot with a solar dryer, also to improve its efficiency. The evaporation is increased by higher wind velocity due to forced convection. A solar dryer can create an airflow when the heated air rises along the surface of the solar collector and creates a temperature difference between the upper and the lower part. A design for a solar dryer that could be appropriately integrated with a Zeer-pot to achieve a greater airflow around it is modelled in CAD and presented. The tests on the pots took place in a climate chamber where the ambient temperature was controllable. In the climate chamber a fan and a dehumidifier was installed in order to create wanted conditions. One pot was tested only for wind velocities and the other only for the cases of the pot hanging in the air and being glazed on the inside. A reference case was designed and tested for the second pot in order to compare the glazed and hanging pot in the same conditions. The relative humidity was not controllable in this setup, and thereof a way to compare these results was to calculate the final temperature the pot achieved relative to the lowest possible theoretical temperature, the wet bulb temperature. For the first pot an almost linear correlation between the time it took to reach the final temperature depending on the wind velocities could be observed, apart from two values. A rather nice coherent curve, also apart from two values, was found for how close to the wet bulb temperature the final temperature was depending on the wind velocity. For the second pot the cooling capacity was enhanced for both the hanging construction and the glazed pot. For the hanging pot this was expected, but for the glazed one it was not. If a solar dryer is combined with the Zeer-pot, a wind velocity around 3-3.5 m/s is guaranteed to improve the Zeer-pots cooling capacity. A lower wind velocity could probably make a large difference too, but the experiments in this study is insufficient to make any conclusions. / I utvecklingsländer beror cirka 40 % av matavfallet på förluster efter skörd, till exempel felaktig förvaring. En Zeer-pot är en evaporativ kylare som kyls med hjälp av konvektion och kan användas för att öka livslängden på frukter och grönsaker. Den är användbar i områden utan tillgång till elektricitet där klimatet är varmt och behovet för kylning är stort. Kyleffekten förbättras i ett klimat med låg luftfuktighet. Denna studie kommer att undersöka om det finns ett samband, mellan temperatursänkningen och vindhastigheten. Ett sätt att förbättra kyleffekten skulle kunna vara att konstruera någon form av stöd för att göra det möjligt för krukan att hänga i luften, detta för att även undersidan ska utsättas för luftflödet. För att inte låta fukten som skapas vid evaporationen komma in i innerkrukan där maten förvaras kan innersidan glaseras. Hur mycket dessa justeringar kommer att påverka kylkapaciteten undersöks också i denna studie. Krukan kyls med hjälp av evaporation av vatten och denna ökar vid en högre vindhastighet på grund av påtvingad konvektion. Ett sätt att skapa ett större luftflöde runt krukan är att integrera en soltork med den så kallade Zeer-poten. Soltorken skapar ett luftflöde då en temperaturskillnad mellan den övre och den undre delen får värmen att stiga upp från ytan av solfångaren. En hypotetisk modell av en lämplig soltork modelleras i CAD och presenteras. För att se en korrelation för hur ökade vindhastigheter påverkar temperatursänkningen i grader och hur fort sluttemperaturen uppnås gjordes tester på samma kruka i så i övrigt konstanta förhållanden som praktiskt var möjligt. Testen för de olika krukorna ägde rum i en klimatkammare där luftens temperatur gick att kontrollera. En fläkt och en avfuktare var installerade. Den ena krukan testades för fallet med olika vindhastigheter och den andra för den upphängda krukan och för glaseringen på insidan. Ett referensfall gjordes även för att jämföra den andra krukans två fall separat. Den relativa fuktigheten gick inte att kontrollera i klimat-kammaren och därav fick resultaten jämföras genom en framräknad procentsats. Procentsatsen visade hur långt testets sluttemperatur hade sjunkit i förhållande till den våta temperaturen. En nästan linjär korrelation, med undantag för två värden, mellan tiden det tog att nå sluttemperaturen i förhållande till vindhastigheten kunde observeras. Ett tydligt samband, också undantaget från två värden, kunde observeras mellan den våta temperaturen och den uppnådda temperaturen för olika hastigheter. För den andra krukan ökade kylkapaciteten för både den hängande konstruktionen samt den glaserade krukan. Det var väntat för den hängande konstruktionen, men inte för den glaserade. Om en soltork kombineras med Zeer-poten i syfte att märkbart förbättra dess kylkapacitet, skulle ett luftflöde med en vindhastighet kring 3-3,5 m/s garanterat fungera. Lägre vindhastigheter lär även de kunna påverka krukan nästan lika mycket, men tyvärr är resultaten från experimenten inte tillräckliga för att dra några slutsatser om detta.

A computer simulation was done in COMSOL Mulitphysics 5.1, on heat transfer in rods filled with phase change material (PCM). The main objective was to compare the rods rate of heat transfer at two different orientations, horizontal and vertical. Information about the viscosity gradient, velocity magnitude and temperature gradient were used to analyze the result. The vertical orientation showed a faster rate of heat transfer with a large initial difference. The horizontal placement shows tendencies to provide a more even rate of heat transfer. To analyze the simulation a literature study was conducted on the theory behind modeling phase change heat transfer coupled with fluid flow. The societal implications of better PCM technology were also discussed. / Denna rapport tittar på värmeöverföringen i en cylinder fylld med phase change material (PCM) och hur denna påverkas vid olika placeringar. De placeringar som simuleras är vertikal och horisontell. Båda placeringarna modelleras som 3D- modeller. Det förväntas bli en skillnad i värmeöverföring på grund av ett internt flöde i cylindern som skapas av förändringen i densitet och hur denna påverkas av gravitationen. Studien visar att den vertikala modellen påvisar något högre hastighet i värmeöverföring än den vertikala. Simuleringarna utfördes med mjukvaran COMSOL multiphysics 5.1. För att vidare förstå och tolka datan utförs en litteraturstudie på den bakomliggande teorin till värmeöverföring med fasförändring och denna redogör för de ekvationer som används av COMSOL för att beräkna modellerna. Vidare kopplas även PCM teknik till sociala aspekter i en redogörelse för hur denna typ av värme- lagrings teknik kan påverka samhället

High cycle fatigue failure of turbine and compressor blades due to resonance in the operating frequency range is one of the main problems in the design of gas turbine engines. To suppress excessive vibrations in the blades and prevent high cycle fatigue, dry friction dampers are used by the engine manufacturers. However, due to the nonlinear nature of friction contact, analysis of such systems becomes complicated. This work focuses on the numerical modelling of friction contact and a 3D friction contact model is developed. To reduce the computation time in the Newton-iteration steps, a method to compute the Jacobian matrix in parallel to the contact forces is proposed. The developed numerical scheme is successfully applied on turbine blades with shroud contact having an arbitrary 3D relative displacement. The equations of motion are formulated in the frequency domain using the multiharmonic balance method to accurately capture the nonlinear contact forces and displacements. Moreover, the equations of motion of the full turbine blade model are reduced to a single sector model by exploiting the concept of the cyclic symmetry boundary condition for a periodic structure. The developed 3D coupled numerical contact model is compared with a 3D contact model having uncoupled tangential motion and drawback of the uncoupled contact model is discussed. Furthermore, presence of higher harmonics in the nonlinear contact forces is analyzed and their effect on the excitation of the different harmonic indices (nodal diameters) of the bladed disk are systematically presented. Moreover, due to the quasi-analytical computation of the Jacobian matrix, the developed scheme is proved to be effective in solving the equations of motion and significant reduction in time is achieved without loss of accuracy. / <p>QC 20151130</p>