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  • 1.
    Achour, Nemer
    Sveriges lantbruksuniversitet.
    Evaluating energy efficiency and emissions of charred biomass used as a fuel for household cooking in rural Kenya2015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In sub-Saharan Africa a large share of the energy use utilize biomass as a fuel. In some

    countries more than 90 percent of the energy use is biomass. This energy is primarily used for

    cooking, heating and drying. Cooking food on an open fire or using a traditional stove will

    combust the firewood inefficiently and leads to pollution in the form of particulate matter,

    carbon monoxide and other hazardous pollutants. Indoor pollution has serious health effects

    and especially women and children are affected by this since they spend more time in the

    kitchens compared to men.

    More efficient combustion would lead to less harmful pollution to women and children in

    these rural areas. There are different kinds of stoves on the market and one of them is the

    gasifier stove which allows the biomass to go through pyrolysis in a separate step before

    complete combustion. If the charred biomass is harvested before complete combustion it can

    be saved for later use. This stove will result in cleaner and more energy efficient combustion

    compared to the traditional 3-stone-fire.

    The aim of this study has been to evaluate the charred biomass harvested from this gasifier

    stove in terms of energy use efficiency, emissions and cooking time. The charred biomass was

    compared to conventional charcoal bought at the local market. The charred biomass

    investigated is charred Grevillea prunings from the

    Grevillea Robusta tree, charred coconut

    husks (

    Cocos nucifera) and charred maize cobs (Zea mays). They were tested by cooking a

    meal consisting of two dishes at five different households for different kinds of charred

    biomass and conventional charcoal as a reference.

    Using charred Grevillea prunings gives an energy saving up to 31 percent while charred

    coconut husks gives up to 11 percent energy saved compared to the 3-stone-fire. Charred

    maize cobs was only up to 2 percent more energy efficient than conventional charcoal due to

    its low energy density and fast burning rate. In most cases there was no significant difference

    between the emissions of the different charred fuel types. Only charred maize cobs resulted in

    significantly higher emissions than the other fuels. Household B deviated from the others

    households and had higher emissions. In conclusion the different types of charred biomass are

    good fuels for cooking. Charred maize cobs are less valuable since they require a higher rate

    of refilling of fuel during cooking and do not result in better energy use efficiency compared

    to conventional charcoal.

    There were no significant differences between the different types of charred biomass and

    conventional charcoal in emissions except for a few cases where charred maize cobs had a

    slightly higher level of emission compared to the others. CO

    2- levels were so low that there

    was no risk of harmful concentrations in any way. PM

    2.5-emissions levels were safe, but the

    CO-emissions levels for charred maize cobs were close to levels were symptoms might show.

  • 2.
    Adolfsson, Ida
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Scenarioanalys över Sveriges elproduktion år 2050: Kan Sverige försörja sig med 100 % förnybar2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    The aim of this report was to investigate if Sweden can have 100 % renewable electricity production in the year 2050. The conclusion is that it is possible but under certain conditions. For instance wave power must be in commercial use. When wind power and solar power represent a large percentage of the electric production there will be a lack of electric power during the winter but during the summer there will be a surplus of electric power. Both the surplus and the lack of electric power need to be taken into account. Two possible ways to handle this are by demand side management and to have good transmissions capacity to other countries. Both ways have their benefits and disadvantages and more studies need to investigate if those ways can manage the surplus and the lack of electric power.

  • 3.
    Adolfsson, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Characterization of combinatorial Cu2ZnSnS4 thin films2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The kesterite Cu2ZnSnS4 (CZTS) is considered as a possible absorber layer in future photovoltaic (PV) applications. The abundance of its constituent elements along with the material being non-toxic and having a direct band gap of around 1.5 eV make it an attractive material for solar cell applications. So far, cells with an efficiency of 12.6 % have been achieved. The limiting factor is the finished cells' open circuit voltage (VOC) deficit which has been attributed to structural defects in the material. Problems with sustaining a sulfur-enriched atmosphere during the annealing step of material production have been observed, and are thought to be partially responsible for the high density of structural defects. Elemental sulfur is commonly used for inducing a sulfur-enriched atmosphere in the anneal. In this study, four combinatorial and polycrystalline CZTS thin films were prepared and annealed in different conditions with regards to time, sulfur source and amount. The samples were characterized using energy dispersive-, Raman- and photoluminescence spectroscopy. The effect of the anneal on the different composition regions were analyzed and secondary phases were identified. Introducing CuS as the sulfur source during the anneal reduced the decomposition of the CZTS phase, and lowered the density of the defect complex [ZnCu + CuZn], while enlarging the single phase region. Strictly and highly Sn-rich compositions of CZTS was observed to yield both high cation order and photoluminescence intensity, and a link between the two parameters was observed.

  • 4.
    Ahlström, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Åsktransienter och överspänningar: En spänningsfylld simulering av elkraftsystemet vid Forsmark 32014Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A power system will inevitably be subjected to transient overvoltages, most often produced by switching operations and lightning strikes. These transient overvoltages may harm sensitive equipment without sufficient protection, but it is not an easy task to predict what transients may occur or how they affect the system. A fault occurred in a low voltage system at Forsmark 2012 and overvoltages from lightning were concluded as the probable cause. The three aims with this thesis are to develop and test a model of the power system at Forsmark 3, analyse the transient behaviour of the system when subjected to lightning surges and identify critical parameters, and lastly to provide a tool for investigating the protection of the system. The modelling and simulations were performed in the freely available simulation program LT Spice. Challenges and difficulties have been to obtain parameter values for components that are relevant for the high frequencies produced by the short rise time in lightning surges. The main conclusions are: the maximum current in the lightning discharge has the largest impact on the system voltages and surges in the external grid can produce standing waves in the system, causing significant overvoltages even in low voltage systems. The simulations produced larger overvoltages than would occur in a real system, which also would dampen the high frequency signals to a larger extent. Further work to obtain models better suited for high frequency simulation is suggested.

  • 5. Albért, AnnaMaria
    Energieffektiviseringar i byggnader med bevarandevärde: Regelverk, praktisk tillämpning och konsekvenser2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The housing and services sector in Sweden consumes 40 % of thetotal energy use. To reach sustainable development goals existingbuildings must be energy efficient. The potential for energyefficiency is in conflict with cultural goals. Uppsalahem is areal-estate company affected by this conflict. Parts of theproperty portfolio are affected by the cultural heritageobjectives, where energy efficiency improvements are desirable.The consequences of this has been investigated.To investigate if and how energy efficiency measures are inconflict with the cultural environment, the regulations werereviewed through the writing of National Board of Housing,Building and Planning, texts of laws and old court orders. Twobuilding permit administrators in Uppsala municipality wereinterviewed and the program VIP-Energy was used to investigate theenergy effect.Heritage Conservation Act, Environmental Code, Planning andBuilding Act are laws that deals with cultural environments. Thefocus of this report was the Planning and Building Act. Dependingon which skills are available in the municipality differentdecision regarding building permits can be made. Also dependingwho is performing the evaluation of the building, different valuescan be determined. The simulations in VIP-Energy showed how muchenergy can be saved through different energy efficiency measures.The most effective measure could provide for 77 newly buildapartments with the energy saved each year after implementing themeasure. The report discusses consequences for the environment,real estate companies, residents and energy producers, suppliersand distributors.

  • 6. Aldenlid, Jennie
    Power Quality Analysis at Falu Hospital2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This is a master thesis performed on behalf of ABB Power Quality Center, aiming to investigate the power quality at Falu hospital. Hospitals can suffer from bad power quality both in the aspect of malfunctioning equipment, and as they can provide disturbances to the power grid. In hospitals it is essential that everything works properly, or the consequences can be fatal. The daily operations at a hospital contains a number of different electrical equipment, from ordinary computers to advanced machines for x-rays or chromatography. This type of equipment can cause disturbances in the power system and other equipment can be affected by this. Therefore, it is very important for hospitals to have good power quality. In order to investigate the power quality, a measurement study was performed at the hospital in Falun. The parameters considered in this study were supply voltage variations, voltage dips, voltage swells, rapid voltage changes, voltage unbalance, voltage harmonics and consumption of active and reactive power. To determine the quality of the power the Swedish statute EIFS 2013:1 was used as a reference for the voltage variations and the grid operator's guidelines for the power parameters. The data from the measurements were analyzed with PQSecure and Matlab. The reults showed that the hospital had no problems regarding the studied parameters of the power quality. They were approved in every case investigated in this study however there could still be improvements regarding the power factor.

  • 7.
    Alfheim, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Definition and evaluation of a dynamic source term module for use within RASTEP: A feasibility study2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    RASTEP (RApid Source TErm Prediction) is a computerized tool for use in the fast diagnosis of accidents in nuclear power plants and analysis of the subsequent radiological source term. The tool is based on a Bayesian Belief Network that is used to determine the most likely plant state which in turn is associated with a pre-calculated source term from level 2 PSA. In its current design the source term predicting abilities of RASTEP are not flexible enough. Therefore, the purpose of this thesis is to identify and evaluate different approaches of enhancing the source term module of RASTEP and provide the foundation for future implementations. Literature studies along with interviews and analysis have been carried out in order to identify possible methods and also to rank them according to feasibility. 4 main methods have been identified of which 2 are considered the most feasible in the short term. The other 2 might prove useful when their maturity level is strengthened. It is concluded from the study that the identified methods can be used in order to enhance RASTEP.

  • 8.
    Alm, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Energieffektivisering av Saltsjöbaden Grand Hotell2017Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In a hotel building there are many processes which consume energy, such as lightning and drive fan motor in the ventilation system. These processes needs supplied with electricity. The building is a big consumer of heat. The heating system is supplied with heat pumps and oil. The consumption of electricity is about 1700 MWh and 350 MWh of oil. This thesis affects an energy saving investigation for a hotel and the purpose is to find measures to reduce the energy consumption for this building. The method for the investigation consisted of three steps. First step was to establish how much energy the building consumes today. Second step was to find measures which could be implemented and the third was to calculate the energy saving potential for each measure. If all investigated measures will be implemented the Hotel could save up to 40 % energy. If only the economical and easy measures would be implemented the hotel could save 30 % energy. The easiest measure was to change some parameters in the control system so the oil burners did not go at all times. With that change and a change in the control system for ventilation to reduce the hours the ventilation are on gave reduced energy consumption with 20 %. The economical investments were converting one of the oil burners to an extra heat pump and to change all old lighting to a new LED-Lighting.

  • 9.
    Alsterlund, Hanna
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Industrial Engineering & Management.
    Effektiva återkopplingsverktyg för elanvändning: En studie som syftar till att identifiera utvecklingsmöjligheter för att uppnå ett mer hållbart energisystem år 20302015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Feedback tools support electricity users within the Swedish residential sector to increase their knowledge of electricity and the electricity market as well as to become more aware of their electricity consumption, which in turn encourages a reduction and an increased flexibility of electricity use. The primary aim of this study is to identify and analyse how existing feedback tools can be improved, to ensure that they contribute efficiently to the achievement of the EU objectives congruent with a more sustainable energy system in 2030, emphasizing: greenhouse gas reduction, increased energy efficiency and an increased share of renewable energy. In order to reach the primary aim of this study, existing feedback tools have been identified and mapped and interviews with feedback tools providers have been conducted. The study is limited to three research areas: the practical functions of feedback tools, available technology and the use of feedback tools.

    The use of more efficient feedback tools will provide an increased success rate for energy management, which includes both behavioural changes and energy efficiency. According to the results from the interviews conducted for this study, an increased use and user frequency is important to utilise the energy management potential. Efficient feedback tools can be achieved by developing existing tool functions. The desired development aims to reduce the effort required of the user, promote immediate and continuous feedback and to increase usability. However, the study shows that in order to achieve maximum effect, adaptions to specific needs of the users have to be made. An increased efficiency may also be achieved with additional features to allow more flexible consumption and encourage further energy efficiency measures.

    The technical aspect is important in order to implement more efficient feedback tools. Existing techniques for data collection should be developed in order to reduce the effort required of the user, enhance the quality and resolution of the data and finally prevent technology limitations, hence enabling feedback tools to be used by all users.

  • 10.
    Alverbäck, Adam
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control.
    LQG-control of a Vertical Axis Wind Turbine with Focus on Torsional Vibrations2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this thesis it has been investigated if LQG control could be used to mitigate torsional oscillations in a variable speed, fixed pitch wind turbine. The wind turbine is a vertical axis wind turbine with a 40 m tall axis that is connected to a generator. The power extracted by the turbine is delivered to the grid via a passive rectifier and an inverter. By controlling the grid side inverter the current is controlled and hence the rotational speed can be controlled. A state space model was developed for the LQG controller. The model includes both the dynamics of the electrical system as swell as the two mass system, consisting of the turbine and the generator connected with a flexible shaft. The controller was designed to minimize a quadratic criterion that punishes both torsional oscillations, command following and input signal magnitude. Integral action was added to the controller to handle the nonlinear aerodynamic torque.

    The controller was compared to the existing control system that uses a PI controller to control the speed, and tested usingMATLAB Simulink. Simulations show that the LQG controller is just as good as the PI controller in controlling the speed of the turbine, and has the advantage that it can be tuned such that the occurrence of torsional oscillations is mitigated. The study also concluded that some external method of dampening torsional oscillations should be implemented to mitigate torsional oscillations in case of a grid fault or loss of PWM signal.

  • 11.
    Ammon, Anton
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Comparing the benefits of energy saving measures with seasonal solar thermal heat storage2014Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis compares the effects of energy saving measures with Active Solar Energy

    Storage (ASES) on a property owned by Stena Fastigheter. The building is located in

    Lövgärdet in Gothenburg and was a part of the Million Homes Program. It was built in 1967, has 9 floors, a heated basement and is heated by district heating. The thermal envelope of the building consists of the walls, doors, windows, roof/attic and the basement.

     

    ASES is a system consisting of solar panels on the roof of a building connected to the heating system. The solar energy that cannot be used immediately is stored in a ground storage unit for when it is needed. ASES can also be supplemented by geothermal heating by drilling boreholes into the ground and, via a Ground Source Heat Pump (GSHP), using the heat in the underlying rock.

     

    The ASES and GSHP system combined were compared to energy saving measure on the thermal envelope in terms of reducing the need for purchased energy and increasing profitability. The energy saving measures were: changing the 2-pane windows to 3-pane windows (either by adding a window pane or changing to a 3-pane window), insulating the façade, insulating the attic, insulating and draining the basement, changing doors, replacing the heat exchanger with a more efficient one, and improving ventilation system. The new system, called FTX, reuses the heat from the exhaust air to save energy.

     

    The results of the thesis show that it is difficult to make energy saving measures profitable. Of the measures evaluated, draining and insulating the basement is extremely cost effective, with a payback time of less than two years. Other profitable measures are insulating the walls (renovation costs of the wall excluded) and insulating the attic, but with a much longer payback time. The ASES and GSHP system are profitable and greatly reduced the need for purchased energy, but require a long payback time. The sum of all energy saving measures does not reduce the need for purchased energy as much, or as cheaply, as ASES, which reduced the energy usage by 62 %.

     

    Due to limited solar panel area ASES cannot supply enough heat to cover the heat demand of the studied building. ASES is therefore believed to be better suited for the buildings that surround the evaluated building. The surrounding buildings have fewer storeys, larger roof area where solar panels can be mounted, and open areas better suited for the ground storage. The potential to implement the ASES system for buildings like these from the Million Homes Program should be evaluated further.

  • 12.
    Andersen, Kristin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Lokalisering av vågkraftanläggningar: Metodutveckling med GIS och fallstudie Bohuskusten2006Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this thesis work a Geographical Information System (GIS) based methodology to identify locations suitable for the installation of wave energy converters has been developed. Parameters of importance have been identified and a GIS-database has been set up, containing data about the marine environment. In a case study of the Swedish west coast the methodology has been applied, resulting in a number of maps showing possible areas. The results show that large areas are suitable for installation of wave energy converters, from a technical and economical point of view. When consideration is taken to other interests in the area, such as navigation, fishing and environmental protection, the size of the suitable area diminishes considerably. However, the results should be interpreted with caution. Thorough investigations of the environmental impact of wave energy converters or detailed calculations of the costs and revenues have not yet been undertaken, because wave energy conversion is a quite new energy technology. The results of the study are therefore mainly based on assumptions. Before the results can be used as a support for decision-making, the methodology, the GIS-data and the knowledge about wave energy need further improvement. 

  • 13. Andersson, Agnes
    Battery energy storage systems in Sweden: A national market analysis and a case study of Behrn sport arena2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The renewable energy sources increase the volatility on theelectricity market. To manage the quick variations battery energystorage systems (BESS), together with other storing solutions, willbe required in the future. Depending on which level in the grid thebattery is placed, it can serve different purposes. In this report amarket analysis is conducted, which examine the performance ofbattery storages installed in Sweden. Further on, a simulation, withPV-panels and a battery, was performed at Behrn Arena in Örebro.

    From the market analysis it was shown that the majority of therespondents had used, or will use, their battery for peak shaving.This function is particularly meaningful for customers with a powertariff, which is the case for Behrn Arena. The simulated systemdecreased their yearly cost due to the power tariff with 70 000 SEKand the total electricity bill decreased with 155 000 SEK.

    For the batteries to be more profitable in the future, the batteryprice needs to decrease or the number of revenue streams need toincrease. One revenue with great potential is frequency regulation,which has proven its efficiency in other countries.

  • 14. Andersson, Elinda
    Vidareutveckling av metod för bedömning av miljöpåverkan i samhällsekonomiska analyser vid investeringar i det svenska elstamnätet2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Svenska kraftnät, which is the authority responsible for the Swedish national grid, performs cost-benefit analysis (CBA) to assess which of different investment projects that are of greatest benefit to society. The environmental impacts are also estimated during this analysis. In this paper, a tool for estimating the environmental impacts during the lifetime of a grid component has been developed with the purpose of enabling a more complete environmental evaluation. A life cycle assessment was performed to develop the tool. The impact categories that have been studied are climate change (kg CO2-eq), freshwater eutrophication (kg P-eq), particulate matter formation (kg PM10-eq) and terrestrial acidification (kg SO2-eq). To be able to compare the environmental effects with other costs and benefits in the CBA a monetary valuation of the impact categories has been established. The result of this paper indicates that the AC-overhead line is the technology that contributes with the lowest environmental impact during the life cycle. This result, however, is obtained when analyzing different technical alternatives with the same preconditions, which rarely is the case in real projects. The result can therefore differ between different investment projects. The tool enables an assessment of the environmental impacts of different investment projects in the Swedish national grid, and is therefore an important part of the cost-benefit analysis to determine which alternative is best suited. 

  • 15.
    Andersson, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Wengberg, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Utvärdering av konsekvenserna för nätanslutning av vindkraftparker i Sverige vid införandet av nätkoden Requirements for Generators2015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Grid codes are becoming more demanding on power generating units due to the factthat the complexity of the power grid is increasing. The penetration of wind powerhas grown over the last years and it is clear that wind farms need to be addressedwith the same type of grid codes as conventional generation units. There is howeveran undeniable difference between the technology in conventional synchronousgeneration units, and the asynchronous generation units in wind farms.

    This thesis has reviewed the current grid code in Sweden and compared it to the newcode proposed by ENTSO-E, “the Requirements for Generators”, in the aspect ofwind farms with an installed power of 30 MW or more. The comparison has beencomplemented by an analysis of how wind farms of two different technologies(Doubly fed induction generators and full power converters) can meet therequirements and technical proposals have been given on how to be able to meetcompliance with the new grid codes.

    The Requirements for Generators contains many non-exhaustive and optionalrequirements, because of this it has been difficult to, at this stage, exactly point outthe technical impact on the grid connection of future wind farms in Sweden. For manyof the requirements in the Requirements for Generators there is no equivalent in theSwedish Grid Code (SvK FS2005:2) but counterparts can thus be found in existingpractices and therefor does not imply any major differences for the industry.

    The requirements of frequency regulation, synthetic inertia and reactive powercapability are the main components of the RfG which will require additional softwareand hardware installations for future wind farms in Sweden.

  • 16.
    Andersson, Johan
    Institutionen för energi och teknik, SLU.
    Uppgradering av biogas med aska från trädbränslen2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Swedish production of biogas was 1,5 TWh 2011. About half of the production was used as vehicle fuels. The cost for upgrading biogas depends on the size of the biogas plant and its gas production. If the gas flow is low the cost will be high. However, further development of existing upgrading technologies or development of new ones, have good potential to decrease the upgrading cost for small scale biogas plants. The aim of this master thesis is to investigate a new technology for upgrading biogas to vehicle fuel standards.

    The investigated technology is based on the carbonation principle, which means that carbon dioxide is fixed by calcium oxide under the formation of calcite. Wood ash, which is rich of calcium oxide, has been used for capturing carbon dioxide in biogas during the lab-scale tests. During the tests the composition of the ingoing biogas was 35 % carbon dioxide and 65 % methane. When the gas passes through the ash bed the carbon dioxide was fixed by the ash and that is the reason why the methane yields is about 95-100 % in the outgoing gas.

    Three different types of wood ashes have been investigated. They originate from combustion of wood pellets respectively different assortment of wood chips. Ash from combustion of wood pellets shows the best ability to capture carbon dioxide, 0,24 g CO

    2/g dry ash.

    A Proposal on a system design has been developed based on the results from the lab-scale tests. Simplified calculations showed that the upgrading cost for the proposed system was 0,24 kr/kWh. That is about half of the cost compared to the available small-scale upgrading technologies on the market. The calculations were based on a biogas plant with the annual gas production of 1 GWh, which is a typical size for a Swedish farm-scale biogas plant

  • 17.
    Andersson, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Wave Power Base Load Properties: A study on wave power base load properties and wind and wave power co-production2008Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The increased introduction of renewable energy puts pressure on power producers to level peak loads, since the electrical generation from renewable sources more often than not is of intermittent nature. Good base load properties i.e. smooth and even power production over time is one of the most important characteristic a renewable source can show since that implies that less regulating power is required.

    This project examines the base load properties of wave power and compares them to the base load properties of wind power. This is done based on wave data from Islandsberg on the Swedish west coast and on wind and wave data recorded at Horns rev, a large wind power farm of the west coast of Jutland, Denmark. The wave energy converter (WEC) investigated is a point absorber type WEC, similar to the device developed at Uppsala University / Seabased AB.

    The results indicate that electrical generation from waves is less fluctuating than generation from winds. Further, wind and wave power co-production would benefit from the time delay in electric wave generation due to that the wind-generated waves continue, after the wind velocities slow down and the wind power output decreases. However, the results also show that Horns rev (and Islandsberg) have rather moderate wave climates and wind-wave co-production would be better balanced inmore energetic wave climates (deeper and/or more exposed waters).

  • 18.
    Andersson, Malin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Energy storage solutions for electric bus fast charging stations: Cost optimization of grid connection and grid reinforcements2017Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This study investigates the economic benefits of installing a lithium-ion battery storage (lithium iron phosphate, LFP and lithium titanate, LTO) at an electric bus fast charging station.  It is conducted on a potential electric bus system in the Swedish city Västerås, and based on the existing bus schedules and routes as well as the local distribution system. The size of the energy storage as well as the maximum power outtake from the grid is optimized in order to minimize the total annual cost of the connection. The assessment of the distribution system shows that implementing an electric bus system based on opportunity charging in Västerås does not cause over-capacity in the 10 kV grid during normal feeding mode. However, grid reinforcements might become necessary to guarantee potential backup feeding modes. Batteries are not a cost effective option to decrease grid owner investments in new transformers. However, battery energy storage have the possibility to decrease the annual cost of connecting a fast charging station to the low-voltage grid. The main advantage of the storage system is to decrease the fees to the grid owner. Of the studied batteries, LTO is the most cost effective solution because of its larger possible depth-of-discharge for a given cycle life. The most important characteristics, that determine if a fast charging station could benefit economically from an energy storage, is the bus frequency. The longer the time in between buses and the higher the power demand, the more advantageous is the energy storage.

  • 19.
    Andersson, Mats
    SLU, Institutionen för energi och teknik.
    Energikartläggning av biogasanläggningen, Kungsängens gård2011Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this thesis was to make an energy survey and quantify energy flows of individual unit operations associated with the biogas production in Uppsala Vatten och Avfall AB:s biogas plant, located at Kungsängens gård. Moreover, large consumers of energy would be identified and analyzed. The objective of this energy survey was to obtain a detailed understanding of the energy use in the biogas production.

    The energy survey was divided into two parts: electricity and heat. Each part was treated separately and with somewhat different approach. To estimate the electricity usage during the projcet the rated power of each selected unit operation was noted and multplied with thenmeasured time of usage. By doing that the total amount of energy consumed is obtained.

    During the project a total amount of 152 kWh/ton electricity was used. The 12 largest electricity consumers had a combined usage of 106 kWh/ton, corrresponding to 70 % .

    The heat survey was subdivided into hot water and steam. Hot water is used to keep the biogas digesters and facilities warm. Steam is exclusively used in the heat pretreatment.

    Thermal energy consumption was as following:

    • Keeping the biogas digester warm consumed close to 20 % of the total heating demand, corresponding to 40,8 kWh/ton.
    • Heat pretreatment accounted for 62 % of the total heating demand, corresponding to 129 kWh/ton.
    • Heating demand for other staff facilities accounted for 18 % of the total heating demand, corresponding to 37,7 kWh/ton.
  • 20.
    Andersson, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Förutsättningar att utforma stationsbatterier i vattenkraftverk med Li-jonteknik2015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In hydropower plants it is necessary to always have local power supply. Therefore, the plants are equipped with batteries as stationary back up power. Vattenfall Vattenkraft is using lead acid batteries but has been investigating alternatives to replace them. The aim of this study is to investigate the potential of using Li-ion technology as back up power.

    The study showed that Li-ion batteries have many qualities. The Li-ion technology will decrease the space and maintenance demand. The technology also eliminates many of the personal safety risks that lead acid batteries may cause. Unfortunately overcharging or overheating the Li-ion battery may result in fire or explosion. Those risks are reduced by an electronic battery management system and mechanical protection.

    The result from the cost comparison between the two battery technologies showed that the maintenance costs decreases with 70 % when using Li-ion battery. The purchase cost of Li-ion batteries is almost three times higher compared to lead acid batteries. But prices will probably drop drastically in the coming years.

    According to this study Li-ion has great potential to replace the lead acid battery.  Vattenfall Vattenkraft should wait until the technology develops further and prices decrease before any larger installations are made. But small installations should be considered in order to get more experience of the technology.

     

  • 21.
    Andersson, Sofia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Energikartläggning av ett stort företag: Rutin för insamling av energidata, energianalys och åtgärdsförslag2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The EU directives of energy efficiency and transparency of sustainablework have recently been implemented in Swedish law. This requires largecompanies to report audits of their energy use and how they work withsustainability. Due to the recent requirements, many companies do not havea systematic method to collect and report the data needed. In this projectsuch a company in construction and residential development - VeidekkeSverige - has been examined and evaluated. The aim of the project has beento systemize the collection and compilation of data from the energy use ofVeidekke Sverige and perform an energy audit and report their greenhousegas emissions. The energy audit involves systematically mapping energyusage and making proposals for cost-effective measures to decrease energyuse. This has been made at a general level for the whole company andstudied in detail at one of the affiliated companies - Veidekke Prefab.The routine for the collection of energy data developed in this projectwas made with standardized surveys, adapted to the type of data requestedin any special case, from a variety of internal units at the company andexternal suppliers. The compilation of the surveys has been programmed inExcel. Although the routine for the collection and compilation of energydata has been standardized from previous implementations, unique manualchanges to the compilation file is still required for an upcoming year. Arecommendation is therefore to implement the developed routine at adigital platform, where surveys can be filled in online and then managedand compiled automatically at the platform. The energy survey of VeidekkeSweden shows that energy consumption in 2017 was about 50 GWh, of whichfuel accounts for 37%, electricity for 33% and gasoline for 25%. Thus,measures of energy efficiency should be done in the use of these threesources. The detailed energy audit of Veidekke Prefab shows that thecompany has a high power consumption of which half derives from theproduction, although, focus of the energy audit has been on ventilationand heating. The plant has two buildings for drying that are heated withdirectacting electric boilers which are recommended to be replaced by airheat pumps. In addition, the ventilation unit for the large buildingshould be replaced by a more modern unit with rotary heat recovery toreduce demand of district heating with about 20 %. Another feasiblemeasure is to replace the lighting to LED units, which would reduce energyconsumption by 6 %.

  • 22.
    Andersson, Therese
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    The potential of utilizing geographic information systems for the district heating networks within Fortum Heat2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This study is a thesis work at Uppsala University initiated by the Cross Country Team for Operate Networks at Fortum Heat. The team requested an analysis of the current situation of the functions, processes and systems regarding geographic information systems, GIS, for the district heating networks within Fortum Heat. GIS software is used to store, analyse and visualize information in digital maps. This study aims to investigate in which processes the use of GIS can contribute to facilitate and make operations more effective. The potential of utilizing GIS for the district heating networks was found to be: geographic and technical documentation, visualization, maintenance management, locate potential customers, sales, customer communication, risk analysis and other types of analysis.

     

    The situation regarding documentation, maintenance management and customer management differs a lot between the district heating networks within Fortum Heat. The general conclusions and recommendations for improvement are to implement GIS for those networks that do not utilize GIS for documentation today. These networks are situated in Plock, Czestochowa and Jelgava. A further recommendation is that there should be one target system for GIS within Fortum Heat. The advantages of using the same system in the whole heat division are that there would be more users with knowledge about the systems, which could benefit from collaboration with each other. The maintenance management system for a district heating network should include an asset register where the network is well defined and where all parts of the network are represented as individuals. Since a district heating network in opposite to a heat plant is spread over a large geographical area is a map of the district heating network necessary for planning and execution of work. To meet these requirements either a module for maintenance planning in a GIS or integration between the current GIS system of a district heating network and the maintenance management system Maximo could be used. A large potential of utilizing GIS is to locate potential new customers, sales and customer communication. More active use of GIS in when locating new potential customers and analysis of where non-connected buildings near existing district heating networks are situated would result in more targeted marketing. 

  • 23.
    Andersson, Viktoria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Elbilar på Lidingö: Påverkan på det regionala elnätet2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis aims towards increasing the understanding of how the growing number of electric cars is going to affect the regional power grid of Stockholm. The results are meant to aid in long term planning of maintenance and development of the regional power grid. Three possible scenarios are presented for the development of electric cars on Lidingo until the year 2040. The number of electric cars, maximum load and load profiles are calculated and analyzed for each scenario. Possible measures of value for the DSO Ellevio are then presented.

    By the year 2040 it is likely that at least one fourth of cars are electric. The maximum power loads from the charging of electric cars will coincide with already existing power peaks during early evening. Loads from charging of electric car will cause a significant contribution to the loads of the regional power grid. If international, national and local climate goals are to be fulfilled the loads would be even larger, though that scenario is deemed unlikely. It is concluded that extensive measures in the regional power grid of Lidingo are needed in order to handle the new maximum loads. It is suggested that Ellevio should start planning for upgrading components, install energy storages and work for load shifting in order to handle the higher loads.

  • 24.
    Appelstål, Sophia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Teknisk utvärdering av befintliga och potentiella teknologier för automatisk frekvensreglering i det svenska elnätet2019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The increasing amount of renewable energy in the power system have led to new challenges to balance supply and demand in the electric grid. To maintain the balance in the power system the system operator can activate power reserves to restore the balance at a frequency deviation. Today these reserves consist exclusively of hydropower in Sweden. With more volatile power generation new types of technologies to provide these reserves are desirable.

    The aim of this master thesis is to investigate the technical potential for using wind power, demand response and energy storage for automatic frequency control in the Swedish power system. The thesis examines the performance of the different technologies to see if they meet the technical requirements for delivering reserves set by the TSO. Moreover, the available capacity from the technologies throughout the year are estimated.

    The results show that all three technologies potentially could be used for frequency control. However, the technical requirements are not always fulfilled. In order to enable new technologies to provide power reserves some of the requirements needs to be modernized. Generally, demand response proved to have the largest available capacity for frequency control today. The study shows that demand response from industries and electric heated households could potentially provide all automatic frequency control. Modern wind turbines can be used for frequency control and for down regulation of the frequency the potential is considerable. Energy storages are not yet widely used in Sweden but with reduced costs they can play an important role in regulating the frequency in the future.  

  • 25.
    Arlemark, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    CFD model of fluid flow in reactor: A simulation of velocity and heat distribution in a channel2006Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The basic problem of operating a boiling water nuclear reactor (BWR) is that of maximizing the power output while avoiding fuel rod over-heating (dry-out). For the safe operation of BWRs this entails a detailed understanding of the flow of water and steam through the reactor core. In a BWR the water functions not only as a coolant, but also as a moderator for the neutrons emitted in the fission process. To describe the thermohydraulic properties of the reactor a number of parameters are of common interest. Examples of such parameters are void, pressure, temperature, water and steam velocities, pressure, sheer forces and turbulent kinetic energy. There are a few ways of revealing these values such as experiments built up to behave like a reactors and computer simulations using models based on the laws of fluid dynamics and thermodynamics.

    This research concerns a computer based model which uses a continuous fluid dynamic, (CFD), calculation program called OpenFOAM (Open Field Operation and Manipulation). OpenFOAM uses Navier Stokes equations for continuity, momentum- and energy conservation to simulate flows. The method used in this research has been to first build a model which describes the adiabatic flow correctly by using an already existing solver which uses the continuity and momentum conservation laws. In order to achieve a model that can solve temperature distributions in the flow the energy equation is added to the program coding in OpenFOAM.

    There are totally 12 turbulence models. Some of the models have not produced results on account of that they either diverged or needed input that was not attainable. The models which were tested and used were four k -ε models, one RSTM model and two low-Re models. A question that is addressed in this report is which of the many turbulence models that describes the experimental flow most correctly. The low-Re model LienLeschzinerLowRe produces the results with best congruence to the experimental data. The k -ε models model RNGkEpsilon and the RSTM model LRR were also fairly close.

    It is found that there are a few turbulence models that describe the experimental flows sufficiently well. LaunderSharmaKe was the turbulence model which simulated the temperature distribution best and was almost within the error bar limit of 5 K in all of the plots.

    It is interesting that the two low-Re models show the best results if only one characteristic at the time is studied. One of the turbulence models describes only the velocity profile well and the other one oppositely describes the temperature distribution the best. It can thereby be stated that if the user wants a turbulence model that describes both velocity profiles and temperature distribution the RSTM model LRR is the best one. If on the other hand computer capacity is a limiting factor it might be profitable to use the simpler k -ε model RNGkEpsilon.

    An other conclusions of this thesis is that the LRR and RNGkepsilon models are suited for the simulations of the geometries described in this work provided that the channel is wide enough for the model to simulate a correct temperature profile. With the use of gmsh a case geometry with wider channel area could easily be created. It would of course be necessary to use experimental data to validate the assumption that more realistic results can be obtained on wider channels.

  • 26.
    Arvidsson, Mari
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Analys av mellanspänningsnätet i centrala delar av Västerås stad2015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The dependency of continuous electricity supply is high in the Swedish society today, at the same time no one is willing to pay for a too costly or over dimensioned power distribution system. The owners of the distribution systems are the ones responsible for this balance act of maintaining a high quality of electricity delivery to customers at a reasonable cost.

    In this master thesis a limited part of the primary distribution system (10 kV), owned by Mälarenergi Elnät AB and located in the city centre of Västerås, was chosen for a deeper analysis of its reliability. Its ability to handle outages of system components (N-1 and N-2 contingency analysis) was investigated to find out potential weak spots and parts of the grid that showed signs of being overdimensioned.

    The results of the performed simulations showed that in 74 % of the studied N-1 contingencies cases, consisting of outages of a bus bar in a distribution substation, the system could handle this without causing outages in other parts of the grid. For the N-2 contingencies 61 % passed the test. It was also found that one of the two included high voltage substations could alone supply the investigated part of the grid. Some cables and transformers were found to be more or less unnecessary, whereas other components proved to be overloaded in several situations.

  • 27.
    Ayotte, John
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control.
    Dynamic positioning of a semi-submersible, multi-turbine wind power platform2015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As a growing market for offshore wind power has created a niche for deep-water installations, offshore floating wind solutions have become more and more viable as a renewable energy source. This technology is currently in development and as with many new technologies, many traditional design methods are found lacking. In the multi-turbine platform design investigated, turbine units are placed closely together to conserve material use and reduce cost, however with such tightly spaced turbines; wake interaction poses a threat to the productivity and the lifespan of the installation. In order to fully capitalize on the substantial increase in available wind energy far at sea, it is important that these floating parks operate in an optimal way. The platform investigated in this report sports 3, 6MW turbines which must be positioned such that wake interference is minimized; the platform must always bear a windward heading. 

    Maneuvering ocean going vessels has been practiced using automated dynamic positioning systems in the gas and oil industry for over 50 years, often employing submerged thrusters as a source of propulsion. These systems are mostly diesel powered and require extra operational maintenance, which would otherwise increase the cost and complexity of a floating wind farm. In this paper, it is suggested that the wind turbines themselves may be used to provide the thrust needed to correct the platform heading, thus eliminating the practical need for submerged thrusters. By controlling the blade pitch of the wind turbines, a turning moment (torque) can be exerted on the platform to correct heading (yaw) relative wind direction. Using the Hexicon H3-18MW platform as a starting point; hydrodynamic, aerodynamic and electromechanical properties of the system are explored, modeled and attempts at model predictive control are made. Preliminary results show that it is possible to control the H3’s position (in yaw) relative the wind using this novel method.

  • 28.
    Backström, Kristoffer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Statistisk analys av partiella urladdningar2010Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis concerns partial discharges in stator windings and the possibility of analyzing data using statistical methods. Partial discharges, or PD, are a physical phenomenon in which discharges occur locally due to large electric fields. PD can occur in or adjacent to the insulation of stator windings and causes breakdown of the insulating materials. PD measurement can provide an idea of how widespread the PD activity is. A technique to measure and analyze PD that has become very popular over the last few decades is phase resolved PD patterns. These patterns supplies a "fingerprint" of the PD activity and by visually interpreting this patterns one can, in addition to read the intensity of the PD, also get a picture of what type of PD that is active. The problem with phase resolved PD patterns is that they are very complex and difficult to interpret. By applying statistical methods to PD patterns it has been investigated in this thesis whether the interpretation of the PD patterns can be simplified. The results show that the proposed methods have some advantages as they can quantify trends in the patterns. The methods have also shown to have severe limitations due to the fundamental properties of the PD patterns.

  • 29.
    Barr, Johanna
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Integration of Distributed Generation in the Volt/VAR Management System for Active Distribution Networks2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis is set within the research scope of an active distribution grid. Control of the DG output to ensure voltage stability and reactive power support is investigated. The solution presented in this thesis proposes integration of DG management systems into decentralized parts of the Volt/VAR management system. The solution is designed to address issues connected to increased DG penetration, while at the same time avoiding the technical challenges related to state-of-the-art model-based Volt/VAR management.

    The solution proposes coordinated control of DGs with conventional voltage regulation equipment, based on pre-defined hierarchies. However, to reduce requirements for control and communication technology, the distribution grid is divided into zones. Each zone has its individual Volt/VAR control scheme, where the pre-defined rules depend on the available voltage regulation devices. To add yet another level of flexibility, these zones can be combined into larger zones with a common voltage regulation scheme. This is referred to as "adaptive zoning".

    Extensive time domain simulations are carried out to verify the control efficacy of the proposed method. The simulated cases show that control schemes successfully maintain voltage within limits at disturbed grid conditions. It is seen that coordination of DGs with voltage regulation equipment is an efficient strategy to mitigate the negative impacts of increased DG penetration. Adaptive zoning effectively reduces the requirements for control and communication equipment, while still ensuring a grid-wide solution.

  • 30.
    Bengtsson, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Modelling of a Power System in a Combined Cycle Power Plant2011Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Simulators for power plants can be used for many different purposes, like training for operators or for adjusting control systems, where the main objective is to perform a realistic behaviour for different operating conditions of the power plant. Due to an increased amount of variable energy sources in the power system, the role of the operators has become more important. It can therefore be very valuable for the operators to try different operating conditions like island operation.

    The aim of this thesis is to model the power system of a general combined-cycle power plant simulator. The model should contain certain components and have a realistic behaviour but on the same time be simple enough to perform simulations in real time. The main requirements are to simulate cold start, normal operation, trip of generator, a controlled change-over to island operation and then resynchronisation.

    The modelling and simulations are executed in the modelling software Dymola, version 6.1. The interface for the simulator is built in the program LabView, but that is beyond the scope of this thesis.

    The results show a reasonable performance of the power system with most of the objectives fulfilled. The simulator is able to perform a start-up, normal load changes, trip of a generator, change-over to island operation as well as resynchronisation of the power plant to the external power grid. However, the results from the changing-over to island operation, as well as large load losses during island operation, show an unreasonable behaviour of the system regarding the voltage magnitude at that point. This is probably due to limitations in calculation capacity of Dymola, and the problem has been left to further improvements due to lack of time.

    There has also been a problem during the development of a variable speed regulated induction motor and it has not been possible to make it work due to lack of enough knowledge about how Dymola is performing the calculations. Also this problem has been left to further improvements due to lack of time.

  • 31.
    Berggren, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Study of auxiliary power systemsfor offshore wind turbines: an extended analysis of a diesel gen-setsolution2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Until today the offshore wind power has grown in a steady pace and many new wind farms are being constructed around the globe. An important factor that is investigated today in the industry are the security of power supply to the equipment needed for controlling the offshore system during emergency situations. When a offshore wind farm is disconnected from the external grid and an emergency case occur the wind turbine generators lose their ability to transfer power and they are forced to be taken out of operation. As there are a number of loads in the wind turbines (navigation lights, sensor- and communication-apparatus, ventilation- and heating equipment etc.) they have a load demand which must be supplied in emergency mode. The German Transmission System operator (TSO) TenneT GmbH has set a requirement that the wind turbines is to be supplied by an auxiliary power supply (APS) in 12 hours and therefore there is need for a long-term auxiliary power supply system. This master thesis was assigned to investigate the most feasible APS-system. From the study of a number of different APS's one concept was chosen. This was the diesel gen-set solution placed on an offshore substation at sea. The system was modeled in the software DIgSILENT PowerFactory where a load flow analysis validated the calculated data and a study of the impact of  transients in the system was performed.

  • 32.
    Berglund, Arne
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Control System for Reactive Power of an Offshore Wind Farm2010Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Until just a few years ago wind farms where excluded from many of the requirementsthat can be found in grid codes. But as the numbers of wind farms have grown as wellas the sizes of them, the requirements to connect them to the grid have becomemore stringent. In this thesis it has been investigated if it’s possible to design a controlsystem that controls the reactive power from an offshore wind farm, so that the gridcode requirements regarding reactive power are fulfilled. By controlling the reactivepower the dynamic variations in the voltage are decreased. The regulator should alsobe able to help the wind farm to handle the fault conditions that are described in thegrid code.An offshore wind farm outside the coast of Western Europe is now being planned.Data from this wind farm has been used in this thesis. The wind farm has a total of 54wind turbines with more than 300 MW all together. The reactive power is controlledvia the generators and also by disconnecting and connecting four shunt reactors.A model of the wind farm has been built in Simpow, as well as design of the regulator.Simpow is a simulation program developed by ABB that enables simulations of powersystems. Different scenarios have been simulated to see if it is possible to control thewind farm in the desired way. The results show that the wind farm manages to handlefault conditions as described in the grid, and it is also possible to control the reactivepower in a desirable way.

  • 33.
    Bergman, Adam
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Utvärdering av Blitzortung blixtlokaliseringssystem: En jämförande studie med SMHI som referenssystem2017Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Blitzortung is a non-commercial lightning detection system intended for recreational use only. In this thesis the performance of the Blitzortung system is evaluated in order to see to which extent it can be compared to a high performance commercial lightning detection system for use in Sweden. Also a graphical tool for visualising lightning strikes detected by Blitzortung on maps containing an electric grid with the related infrastructure is proposed.

    The evaluation is accomplished by comparing lightning data registered by Blitzortung with lightning data from the national lightning locating system provided by the Swedish meteorological institute. By analysing lightning data from the lightning high-season in Sweden between the year 2012-2016, and by conducting a more in depth evaluation of the system based on data from 2016, the Blitzortung system performance is evaluated.

    Results for calculated flash density and flash rate density suggests that the Blitzortung system is improving over the study time, which is probably due to the fact that the number of sensors in Sweden has increased from a single station in 2012 to 30 stations in 2016. The performance evaluation show a relative detection efficiency of 34 % for strokes correlated between the systems in relation to the total strokes detected by SMHI. For strokes detected south of latitude 61 in Sweden the relative DE (detection efficiency) is 44.7 %, and for CG(cloud-toground) strokes it is 43.0 %. If only CG-strokes south of latitude 61 is considered the corresponding value is 55.1 %. The performance of the Blitzortung-system seems to be depending on the number of sensors in the region of interest. The relative positional error between the networks south of latitude 61 was shown to have a smaller median error of 1750 m and an upper quartile on 3350 m, compared to north of latitude 61 where the median error was 2780 m and the upper quartile 5900 m.

    The results indicates a systematic directional error for correlated strokes between the systems. It is also shown that the included parameters for Blitzortung strokes could not be used in any meaningful way for predicting positional errors between the networks.

  • 34.
    Bergquist, Hampus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    A self restoring system on low voltage level2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Fortums electric grid in Norra Djurgårdsstaden is a test grid for smart equipment and they are investigating new techniques and ways to improve the quality of the grid. With the quality improvements that are researched, a "self-restoring system" is a part of the research with the intention to lower the amount of outages and shorten the time it takes to restore faults. This thesis can be seen as a part of the optimization process of the grid in Norra Djurgårdsstaden where the benefits with a basic self-restoring system have been investigated on low voltage level.

    In the thesis the self-restoring system has been classified into a "basic" and an "advanced" category. The basic self-restoring system cross-connect several feeding paths by cross-connecting different low voltage grids and use mechanical equipment to change between cables when a fault in a cable occurs. The advanced self-restoring system uses several feeders and smart grid technology with equipment and softwares which communicate and visualize the grid.

    The difference between the systems is that the advanced system can visualize the grid and is able to tell when and where faults have occurred to a more detailed level. The advanced system can also calculate the power available and does not need the same amount of cables for redundancy because it can command users to lower their consumption when an outage has occurred. A decision was made to only investigate the technique on low voltage level because a basic system already exists on medium voltage in Norra Djurgårdsstaden.

    Results show that investing in a basic self-restoring system in Norra Djurgårdsstaden would cost about 2 million SEK and lower the total amount of outages for the customers in the area from 45 minutes per customer and year down to about 41 minutes. The reason why the decrease is only four minutes per year and customer is because faults occurring on higher voltage level cannot be reduced with the system. It is totally about 10 % of the faults that occur on low voltage level.

    One conclusion from the thesis is that the reduction in quality costs which are because to the lowered outages will not be enough to pay back the investment. More outage-time per customer and year need to be prevented with the system or the customers need to value reduced outages significantly more.

  • 35.
    Bergqvist, Sofia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Energy Efficiency Improvements Using DC in Data Centres2011Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The installed power usage in a data centre will often amount to several megawatts (MW). Thetotal power consumption of the data centres in the world is comparable to that of the airtraffic. The high energy costs and carbon dioxide emissions resulting from the operation of adata centre call for alternative, more efficient, solutions for the power supply design. Oneproposed solution to decrease the energy usage is to use a direct current power supply (DCUPS) for all the servers in the data centre and thereby reduce the number of conversionsbetween AC and DC.The aim with this thesis was to determine whether such a DC solution brings reduced powerconsumption compared to a traditional setup and, if this is the case, how big the savings are.Measurements were carried out on different equipment and thereafter the power consumptionwas calculated. The conclusion was that up to 25 % in electricity use can be saved when usinga DC power supply compared to the traditional design.Other benefits that come with the DC technology are simplified design, improved reliabilityand lowered investments costs. Moreover the use of DC in data centres enables a moreefficient integration of renewable energy technologies into the power supply design

  • 36.
    Berning, Katrine
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Design of Stand Alone Renewable Power Supply Systems on Futuna Island, Vanuatu2011Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This Master’s Degree project has been performed on behalf of Vanuatu Renewable Energy and Power Association. The purpose of the project was to suggest the design of stand-alone renewable power supply systems on Futuna Island in the Republic of Vanuatu. Futuna is the easternmost island in Vanuatu with a population of about 400 people. The island covers an area of just 13 km2. The proposed sites for power production were the villages of Mission Bay, Matangi, Herald Bay and Iahsoa. In Mission Bay and Matangi the power should be produced by wind turbines and in Herald Bay and Iahsoa, solar modules are proposed.

    The results of the study showed that some parts of Futuna Island can be suitable for wind power production and wind speeds in the order of 5-7 m/s are suggested. However, wind monitoring on the sites are required to estimate the exact potential. Furthermore, the study showed that there is less uncertainty involved with estimating the power output from the solar modules. In addition, solar power proved to be more reliable and less vulnerable to local variations in weather and topography. Solar modules are therefore considered more appropriate for small scale power production on the island, at least until the wind climate is better known.

    The results of the study also showed that proper sizing of battery banks and cables are essential to increase the efficiency and lifetime of the systems. If there are insufficient financial resources in the project, it is therefore recommended in the report to use all resources available to properly size the systems in 1-2 villages rather than to inadequately size the systems in all the villages.

  • 37.
    Bjelkenstedt, Tom
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Optimization and design of a detection system based on transmission tomography with fast neutrons2014Independent thesis Advanced level (professional degree), 300 HE creditsStudent thesis
    Abstract [en]

    This thesis is part of a project focusedon investigating the possibility ofmeasuring void distributions usingtransmission tomography with fastneutrons. The measurements are plannedto be conducted at thermal hydraulictest loops. The project, called STUNT,is carried out at Uppsala University atthe division for applied nuclearphysics.The purpose of this work was to designand optimize a detection system for thedetection of fast neutrons in the abovementioned environment. For this purpose,detector elements consisting of theplastic scintillator material EJ208 wasmodeled using the particle transportcode MCNPX.Both plate shaped elements and fibers ofdifferent dimensions where tested forperformance.Through a comparison utilizing severalfigures of merit and MATLAB, the plateshape was selected with an element widthof 2.6 mm. During the optimizationprocess a possible detector design with73 detector plates was chosen. At anenergy threshold of 11 MeV the followingdesign parameters were found; adetection efficiency of 3.0 %, a signalto background ratio of 15, a totalmeasurement time of 3600 s and a pixelresolution of 1.4 mm.A point spread function was produced andtwo projection tests where conductedusing a water filled steel cylinder asobject.

  • 38.
    Björk, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Analys av stationsreglering vid Forsmarks kärnkraftverk: koppling mot eldynamiska simuleringsverktyg och modeller2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master thesis is done within the Energy Systems Engineering program at Uppsala University and performed for Forsmarks Kraftgrupp, Vattenfall. The nuclear power plant at Forsmark consists of three BWR units and is an important component in the Swedish power system. The nuclear power units are individually connected to the 400 kV transmission grid to export their production, but also to supply the units with auxiliary power when needed. As a backup the units are also connected to the 70 kV grid and each have several sub grids supported by backup diesel engines and batteries.This is to guarantee that the nuclear power units always have electrical power to support their vital auxiliary systems.

    To evaluate the function of the separate local power grids of Forsmark’s nuclear units and their interaction with the offsite grid, the simulation software Simpow have been used. With Simpow, the function of controllers, pumps and motors, vital for the plants safety, can be analyzed for different operation conditions and plant changes. Today the Electrical Power Analysis and Plant Engineering Group are in the process of changing from Simpow to new simulation software, PowerFactory. During this process the question of how to best implement the plant controller have been raised. The plant controller controls the thermal power, pressure and water level of the reactor, all contributing to the dynamics of the units power supply during operation. An implementation of the plant controller exist in Simpow for the plant’s older units Forsmark 1 and 2, but for the newest unit Forsmark 3 there is only a standard model of a steam turbine with governor implemented.

    In this thesis the effect of the plant controller systems are investigated to serve as a basis for implementation of the plants dynamics in the modelling of Forsmark 3 in PowerFactory.

  • 39.
    Björkelund de Faire, Elias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.