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Coming dissertations at TekNat

  • Modeling and Forecasting of Electric Vehicle Charging, Solar Power Production, and Residential Load : Perspectives into the Future Urban and Rural Energy Systems

    Author: Mahmoud Shepero
    Publication date: 2020-08-27 14:13

    The urban and rural energy systems are undergoing modernization. This modernization is motivated by the need to increase sustainability in both systems. Some characteristics of this modernization include electrification of industries, transports, and heating and cooling loads. Additionally, there has been an increase in building-applied photovoltaic (PV) systems, and in the flexibility of customer loads. This thesis aims to progress the knowledge regarding the electric power production and consumption in the future urban and rural energy systems. In total, three models were developed and applied to case studies: a spatial electric vehicle (EV) charging model, a residential load forecasting model, and a clear-sky index (CSI) generative model. The results of the EV spatial model showed that there is an aggregation effect for the charging of the EVs. If all EVs charge opportunistically upon arrival using 3.7 kW, at most 19% of the EVs in a large area will charge simultaneously. Delaying the charging to after 22:00 will result in a significant increase in the simultaneity factor — to 59%. Two forecasting models were compared for the residential load. Both models achieved a root...

  • Window Layer Structures for Chalcopyrite Thin-Film Solar Cells

    Author: Fredrik Larsson
    Publication date: 2020-08-27 08:04

    This thesis aims to contribute to the development of improved window layer structures for chalcopyrite thin-film solar cells, with an emphasis on the buffer layer, to assist future reductions of the levelized cost of energy. This is realized by exploring the potential of existing materials and deposition processes, as well as developing new buffer layer processes based on atomic layer deposition (ALD).

    Ternary compound ALD processes are more complicated to control than when depositing binary compounds and the composition can be significantly different at the absorber interface as compared to the bulk. A method based on in-situ quartz crystal microbalance that can measure these compositional variations is demonstrated in the thesis. Furthermore, the addition of alkali-metal fluoride post-deposition treatments (PDTs) can further complicate ALD of buffer layers, due to residual salts that are formed on the absorber surface during a PDT process. When applying ALD ZnO1-xSx to KF-treated CIGS absorbers, competitive solar cell efficiencies could only be obtained after performing additional wet-chemical treatments prior to ALD processing.

    It is shown that the performance of...

  • New horizons in string theory : bubble babble in search of darkness

    Author: Suvendu Giri
    Publication date: 2020-08-26 10:50

    It was discovered nearly two decades ago that we live in an accelerating universe that is dominated by dark energy. Understanding the origin of such an energy has turned out to be a very difficult open question in physics, and calls on the need for a fundamental theory like string theory. However, despite decades-long effort, string theory has proven incredibly resilient to a satisfactory construction of dark energy within its framework.

    In the first part of this thesis and the included papers, we examine this problem and propose two possible solutions. The first is a construction within the framework of M-theory, the eleven dimensional cousin of string theory. Using only well-understood geometric ingredients and higher-derivative corrections to eleven dimensional supergravity, we present a new class of four dimensional vacua that contain dark energy. In the process, we also construct a new class of non-supersymmetric Minkowski vacua that were previously not known. Our second idea is a novel proposal that our universe could be embedded on the surface of an enormous spherical bubble that is expanding in a five dimensional anti de Sitter spacetime. The bubble is made of...

  • Study of Student Electricity Use in Uppsala

    Author: Max Torbjörner Anthony Gundstedt Philip Shaposhnikov
    Publication date: 2020-07-02 08:51

    This report covers a project that set out to create our own and implement another existing measurement system that measures the power consumption in different student residences with higher resolution then what is currently offered by Vattenfall. This is important since there is a problem in Uppsala with a lack of power from the electrical grid which limits Uppsalas ability to grow as a city. Different dorm rooms in the housing area Gamla Studenstaden were then measured and data with the resolution of 1 minute was then analysed. This data was then used in order to answer which type of accommodation is most efficient with its power usage in relation to the amount of rooms. This report also wanted to answer how different types of accommodations cause spikes in their power usage which are only possible to spot with the higher resolution. The resulting data show that one-room apartments has relatively low power consumption over the day but contribute to so called power spikes which cause large load on the power grid. The dorm rooms did however seem to have a more distributed power consumption over the day.

  • Characterisation of natural dissolved organic matter with liquid chromatography and high resolution mass spectrometry

    Author: Claudia Patriarca
    Publication date: 2020-06-11 10:32

    Dissolved organic matter (DOM) is one of the most heterogeneous and complex mixture on Earth. DOM plays a crucial role in biogeochemical processes on the global scale and it is essential to sustain and regulate the biological processes in aquatic ecosystems. DOM originates from a multitude of biological, physical and chemical transformations, leading to its phenomenal chemical diversity. In order to understand and predict its effect on the global carbon cycle, an intimate characterization at molecular level is necessary. The investigation of the extraordinary complexity of the DOM mixture represents a compelling challenge for analytical chemistry. The focus of this thesis was the development of methods for the characterization of DOM in natural waters. High resolution mass spectrometry (HRMS), was combined with high pressure liquid chromatography (HPLC) and electrospray ionization (ESI), to investigate the chemical diversity of DOM. The first study demonstrated that cutting-edge techniques (such as the Fourier-transform ion cyclotron resonance mass spectrometer - FTICR-MS), are not indispensable to disclose essential information on the DOM molecular composition, in fact the...

  • Inertial motion capture for ambulatory analysis of human movement and balance

    Author: Fredrik Olsson
    Publication date: 2020-06-04 10:58

    Inertial sensors (accelerometers and gyroscopes) are ubiquitous in today’s society, where they can be found in many of our everyday mobile devices. These sensors are capable of recording the movement of the device, and by extension, the movement of humans carrying or interacting with the device. Human motion capture is frequently used for medical purposes to assess individual balance performance and movement disorders. Accurate and objective assessment is important in the design of individualized interventions and rehabilitation strategies.

    The increasing availability of inertial sensors, combined with their mobility and low cost, has made inertial motion capture highly relevant as a more accessible alternative to the laboratory based gold standard. However, mobile solutions need to be adopted for plug-and-play use with the end user in mind. Methods that automatically calibrate the sensors, and methods that detect and record relevant motions are required.

    This thesis contributes to the development of human inertial motion capture as a plug-and-play technology. A method for accelerometer calibration, which allows for compensation of systematic sensor errors, is...

  • Bacterial DNA repair and molecular search

    Author: Arvid H. Gynnå
    Publication date: 2020-06-04 08:45

    Surveillance and repair of DNA damage is necessary in all kinds of life. Different types of DNA damage require different repair mechanisms, but these mechanisms are often similar in all domains of life. The most serious type of damage, double stranded DNA breaks, are for example repaired in conceptually similar ways in both bacteria and eukaryotes. When this kind of breaks are repaired by homologous recombination, a homology to the site of the break must be found. Sometimes, this homology can be located far away from the break necessitating a search. Considering the large amount of heterologous DNA present, the complexity of this search is enormous. If and how this search can proceed has been unclear even in simple and well characterized organisms as E. coli.

    In this thesis, microscopy together with microfluidics are used to show that DNA repair by homologous recombination occurs even between homologies separated by several micrometers. We also see that it finishes well within the time of a cell generation, with the enigmatic search phase being as quick as eight or possibly even three minutes. Since this time is much faster than expected, we present a physical...