Uppsala Kommun is developing a new city district called Sydöstra staden (SÖS) as an innovative and transformative city district. A technical supply system that aligns with the district’s goals is pyrolysis. Pyrolysis is a process where biomass is heated without the supply of oxygen. This leads to carbonization where the energy is converted to biochar and heated gas that can be used for district heating. The biochar, which is considered as a carbon sink, could be the path for the municipality to achieve their climate goals for 2050. The aim of this project is to investigate the viability of providing district heating to SÖS through pyrolysis. Three scenarios based on biomass assets of garden waste, manure, and wooden chips will be evaluated from four perspectives: climate impact, economic feasibility, district heating coverage, and placement considerations. The method is a model constructed in python that simulates how much heat and biochar that can be produced including an income statement and how the price of biochar relates to the return of investment. The biochar price and biomass flow are two parameters that are examined in the sensitivity analysis. The model enables comparisons between the outcomes of the pyrolysis process and the heat energy demands in SÖS, the biochar usage in Uppsala and the municipality’s CO2 emissions. The results show profitable reactor alternatives in all three scenarios even without selling CORCs. However, the profitability is heavily reliant on maximizing the utilization of burned biomass. Furthermore, the first two scenarios had a negligible climate impact while the most profitable reactor in scenario 3 had a large impact on the municipality’s climate goals. Also, the coverage of district heating has been evaluated due to the asset of biomass as well as placement requirements have been stated.

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Wireless sensor networks (WSNs) have been a topic of research for decades. Researchers have been exploring different uses for UAVs with their growing popularity. In this thesis I develop a wireless sensor network (WSN) and introduce the theoretical effects of an unmanned aerial vehicle (UAV) for wireless recharging of individual nodes in the WSN. My research focuses on understanding how to use wireless recharging technology to maximize the lifetime of a WSN by simulating recharging on the physical nodes. Using a three by three grid of nine sensor nodes, I proved that recharging the lowest powered node in the network at each sink iteration increased the lifetime of the WSN by 538% when compared to no recharging. I also further investigate the potential uses of a WSN and UAV for detecting and deterring animals. Using wireless sensor nodes to initially detect movement, and the UAV to find the object proved to be a viable solution for offloading the more power intensive tasks from the WSN to the UAV.

Monitoring the structural health of civil infrastructures with wireless sensor networks aids in detecting failures early, but faces power challenges in ensuring reasonable network lifetimes. Recharging select nodes with Unmanned Aerial Vehicles (UAVs) provides a solution that currently can recharge a single node; however, questions arise on the effectiveness of a limited recharging system, the appropriate node to recharge, and the best sink selection algorithm for improving network lifetime given a limited recharging system. This paper simulates such a network in order to answer those questions. This thesis first determines whether or not recharging with a UAV is an effective method of delivering limited power to the network. It then determines the best way to deliver that power. Finally, this thesis explores five different sink positioning algorithms to find which optimize the network lifetime by load-balancing the energy in the network, all in combination with the added capability of a UAV.

Analytical, closed-form solutions governing thermoelectric behavior are derived. An analytical model utilizing a thermal circuit is presented involving heat transfer into, through, out of, and around a thermoelectric device. A nondimensionalization of the model is presented. Linear heat transfer theory is applied to the model to obtain a series of closed form equations predicting net power output for the thermoelectric device. Fluid streams flowing through shrouded heat sinks with square pin fins are considered for the thermal pathways to and from the device. Heat transfer and pressure drop are characterized in a manner conducive to an analytical model using previously published experimental results. Experimental data is presented which validates and demonstrates the usefulness of the model in predicting power output for commercially available thermoelectric generators. A specific design for a thermoelectric power harvester is suggested consisting of a pattern of thermoelectric generators. An economic model for calculating payback time is developed. An optimization process is demonstrated that allows for the payback time of such a system to be minimized through optimization of the physical design of the system. It is shown that optimization of the thermal pathways dramatically reduces payback time. Optimized design of a system is discussed in light of theoretical cases with feasible payback times.

Biochar can reduce the amount of CO2 in the atmosphere and is acknowledged as one feasible technology for negative carbon emissions. The stability of carbon in biochar is of major importance for the carbon sequestration value. A method for confident estimation of the stability is needed to make efficient priorities for the climate. The aim of this study is to identify the best available method that can be used to indicate the stability and quantify the carbon sequestration potential of biochar. The result builds on a literature review of the current state of scientific knowledge and the proposed method is tested with data from previous studies and then applied to the case of Stockholm Exergi. Biochar has a stable carbon structure, always more recalcitrant than the biomass that it derives from. However, estimations of how stable the carbon are varying a lot in the literature. Biochar is not unambiguously defined, there is rather a range of materials with different stability and the degradationis context dependent. Further discrepancy in the estimated stability derives from different experimental design and approaches to modeling the data. There is a challenge to do a proper estimation of the actual degradation, due to the long time perspective and the complexity of observation of behavior in a naturalsystem. A functional method to indicate the stability of carbon in biochar is needed because a biochar producer cannot conduct a long term trial to prove the carbon sequestration potential. Several methods have in theory the ability to indicate stability. However, the H/Corg model with the expression BC+100 emerging to be the best suited method due to its connection to measured degradation, accessibility and acceptance. The H/Corg model could be further improved by calibration and validation by collecting existing data from previous assessments. Communication of the carbon sequestration after hundred years compared to other carbon sinks should be improved to better reflect the long term carbon sequestration value of biochar. Stockholm Exergi is planning for a biochar production of 5 000 ton/year. The H/Corg method estimate that this corresponds to 9 000 – 11 500 ton CO2 per year, stable for at least hundred years. The widerange in the result derives from the different interpretations on the H/Corg method, where the different interpretations derive from the variation that previous research result shows. This is an incentive to support further development of the method. The sequestered carbon in biochar must be protected in its application to ensure the carbon sink in a trade system. Biochar in soil, green areas and concrete face the risk of being dis/re-located. However, that is not a threat to the carbon sequestration value. Biochar and biochar in a soil product sold in bags cannot account for the biochar sequestration value detached from the product, because of the risk of incineration. The future development of biochar stability assessment should in a short term assemble the existing knowledge of conducted trials and use that with knowledge of what approaches that best corresponds to the real stability of biochar. This could decrease the observed variations in the stability assessments and be used to calibrate and validate methods that could indicate stability. In the long perspective field trials and incubation trials should be done in a standardized way to assess the degradation, designed according to best practice with long trial times and consciously extrapolated data. / Biokol kan minska halten av CO2 i atmosfären och är identifierad som en möjlig teknologi för negativa CO2 utsläpp. Biokolets stabilitet har stor betydelse för dess potential. Målet med denna studie är att identifiera den bästa tillgängliga metoden för att indikera kolets stabilitet. Resultatet bygger på en litteraturgenomgång av befintligt kunskapsläge. Den föreslagna metoden testas med biokolsdata ifrån tidigare gjorda mätningar. Kolinbindningspotentialen i Stockholm Exergi’s biokolsprojekt beräknas genom att applicera metoden på förväntad biokolsproduktion. Biokol har en stabil kolstruktur, alltid mer stabil än den biomassa den härstammar ifrån. Uppskattningar av hur stabilt biokol är varierar mycket i litteraturen. Biokol är inte entydigt definierat utan är ett spann av olika material och dessutom är stabiliteten kontext beroende. Ytterligare variationer härstammar ifrån varierande experimentdesign och olika metoder som används för extrapolation av mätdata. För att beräkna kolinbindning i biokol som produceras behövs en metod som kan visa hur stabilt kolet är.Mätmetoden är resurskrävande och därför behövs istället ett samband mellan kolets innehåll/struktur och uppvisad stabilitet som kan användas i kombination med en enklare analys av det producerade biokolet för att indikera stabilitet. I teorin finns det många metoder som kan vara funktionella men enligt denna studie är H/Corg metoden i kombination med BC+100 index mest lämpligt att använda pågrund av metodens uppvisade koppling till uppmätt stabilitet, tillgänglighet och acceptans. Stockholm Exergi planerar för en biokolsproduktion på 5000 ton/år och H/Corg metoden uppskattar att detta årligen motsvarar 9 000 – 11 500 ton CO2 stabilt i minst 100 år. Spannet som resultatet uppvisar beror av den variation av uppskattad stabilitet i litteraturen och är ett incitament för att stödja en vidareutveckling av metoden. I applikationen av biokol måste kolsänkan skyddas för att kunna ingå i ett handelssystem. För biokol till jordförbättring, grönområden i staden samt biokol i betong föreligger en möjlighet att biokolet blir omflyttat eller förloras ifrån den ursprungliga applikationen, detta medför dock inte att kolsänkan går förlorad och är därför inte ett problem för värdet av kolsänkan. Däremot bör värdet av kolsänkan av biokol som säljs i konsumentförpackningar inte frikopplas ifrån biokolsprodukten eftersom det då saknas kontroll över att kolet inte bränns. Vidare studier av stabilitet av biokol bör på kort sikt innefatta insamling av befintlig data ifrån genomförda försök. Genom kunskap om hur olika faktorer inverkar på verklig och uppskattad stabilitet kan spannet av variation bättre accepteras och minska. Vidare kan insamlad data användas för att kalibrera och validera indikationsmetoder. Kommunikationen av kolsänkan av biokol och det långsiktiga värde som skiljer biokol ifrån andra mer kortsiktiga kolsänkor bör förbättras. Långsiktiga fält och inkubationsförsök bör etableras enligt kunskap om experimentell design och hantering av data för att på ett så korrekt sätt som möjligt spegla verklig stabilitet och kolsänka.

This thesis work researched the temperature effects the insert tool life. This was examined through physical laboratory testing with designed milling tools and temperature simulations in ANSYS. The designed milling tools altered the temperature in the insert through external parameters like design and material. Three milling tools were used in total: A milling tool created in an copper alloy that cools the inserts, a milling tool created in the material idun that increases the temperature in the inserts, and the milling tool Coro Mill 245 that was used as a reference. These tools were tested with two inserts, insert 1130 with a coating of PVD, and insert 4330 which has a coating of CVD.  The idun milling tool and the reference milling tool was already designed, but the copper milling tool was designed during the thesis work. The designed copper milling tool implemented a heat sink to cool the milling tool with convection and was manufactured in a copper alloy with high strength. The copper milling tool was 20 $\%$ colder than the reference milling tool when comparing the maximum temperature of the insert. Through testing in dry milling of the three milling tools with different inserts and a simulation in ANSYS of the temperature development, the conclusion was that insert 4330 had crater wear which increased with increased temperature. This crater wear can be the main factor in the insert tool life.

This thesis presents a simulation study on the thermal performance of the fuel systemin a fighter aircraft. The main objective is to investigate the potential utilization of thefuel system as a heat sink and explore various operational aspects that can enhance itsperformance. To achieve this, the study focuses on analyzing the impact of tank emptyingsequences, fuel types, and the implementation of bypass recirculation under low thrustconditions.The fuel system is modeled using the Modelica language-based tool, Modelon Impact,which enables a thorough and detailed examination of its thermal behavior. A functionalmodel of the fuel system has been successfully built in this modeling tool. The investiga-tion of the three operational aspects has been divided into two heat sink studies. Heat sinkstudy 1 examines the tank emptying sequences, with three different sequences being inves-tigated. The simulation results did not demonstrate any clear and significant benefits fromusing different emptying sequences. However, emptying the fuselage tank first showedslightly better behavior compared to the sequence that involved emptying the wing tanksfirst. Heat sink study 2 focuses on the implementation of bypass recirculation of the fuelback to the tanks. The primary objective of heat sink study 2 is to maintain the feed linetemperature close to the threshold determined by the fuel type in order to . The simulationresults revealed significant improvements in the heat sink capacity of the system, reachingup to 168%.

京都大学 / 新制・課程博士 / 博士(農学) / 甲第24238号 / 農博第2517号 / 新制||農||1094(附属図書館) / 学位論文||R4||N5409(農学部図書室) / 京都大学大学院農学研究科農学専攻 / (主査)教授 土井 元章, 教授 田尾 龍太郎, 准教授 中野 龍平 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

Bromus tectorum, an invasive winter annual, has displaced native vegetation throughout the western United States. Bromus tectorum litter influences nutrient cycling near the soil surface as well as plant establishment. Failed seed production of B. tectorum occasionally occurs in the field, with plants exhibiting weak flowering culms that turn straw-colored in spring when normal plants are green or purple in color. Because annual grasses transport most soluble carbon (C) and nitrogen (N) to reproductive organs, seed production failure results in significantly different fates for these nutrients compared with normal plants. As part of larger efforts to understand events leading to large-scale seedling emergence failure (termed die-offs), occasionally observed in near mono-cultures of B. tectorum, we here test the hypothesis that prematurely senesced litter associated with seed production failure has higher soluble C and N than normal litter. C and N concentrations of aboveground biomass were compared for normal and prematurely senesced B. tectorum plants. Two methods were used to cause premature senescence: fungal pathogen infection with Clarireedia capillus-albis and glyphosate herbicide application. In a related experiment, field sampling of normal and prematurely senesced plants under natural conditions was conducted to compare C and N levels in-situ. Herbicide-induced senescence resulted in 1.5 to 2 times greater soluble C concentrations, but fungal infection had no effect on soluble C under experiment conditions. Prematurely senesced litter had increased total N concentrations, resulting in lower C:N ratios. The C:N ratio for prematurely senesced plants (averaged across all studies) was 68:1, whereas mature normal plants averaged 243:1. These findings illustrate failed seed production associated with premature senescence results in B. tectorum litter with significantly higher N concentrations and can result in increased soluble C concentrations. Altered nutrient status may contribute to changes in soil microbial activity, including activity of soilborne pathogens found in die-offs.