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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, 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.

    The full text will be freely available from 2019-06-30 23:59
  • 3.
    Ahlberg, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Georges, Elza
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Norlén, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    The potential of hemp buildings in different climates: A comparison between a common passive house and the hempcrete building system2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The aim of this bachelor thesis was to study the potential of hemp buildings in different climates. The report examines and models two different energy efficient building concepts – the more common passive house and the environmental friendly hempcrete building system. These two buildings thermal performances were then simulated and compared in different climates followed by a brief discussion about their economic and environmental impact.

    The simulation was performed with the energy calculating program VIP-energy v 2.1.1 with the two models located in Kiruna, Sundsvall, Malmo, Berlin and Rome to represent the different climates. Simulations for different wall sizes and a sensitivity analysis of some significant parameters were also made.

    The hempcrete building system showed to have a thermal performance similar to that of passive houses in more southern climates. In the north of Sweden however the hempcrete building required up to 20 % more energy than the passive house to maintain comfortable indoor temperatures. This deficit could be compensated for with hemp fibre insulation to augment the building envelope and U-value. Furthermore the hygrothermal material properties that were not included in the simulation can be expected to have a significant positive impact on hemp buildings relative thermal performance.

    With a passive house thermal performance, a healthy indoor environment and an economically viable and environmental friendly production process hemp building demonstrated great potential in all the fields studied.

  • 4.
    Ahlvin, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Arrigata, Yasmine
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Bauman, Elise
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Berglund, Hanna
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Magnusson, Clara
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Wiklund, Sofia
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Energiomställning Gotland: Alternativ för att nå ett förnybart energisystem2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Sammanfattning

    Syftet med denna studie är att i åtta scenarier konkretisera hur Gotland skulle kunna ställa om till en förnybar energiförsörjning. Detta ska visa vägen för hela Sveriges omställning till förnybar energi 2040. Studien ska tjäna som en första orientering av vad fortsatt forskning kan inriktas på. Metoden var främst litteraturstudie samt modellering och beräkningar utifrån representativa exempel. Bedöm- ning av alternativ gjordes utifrån de övergripande kriterierna hållbarhet, resurseffektivitet och realis- tisk potential. Som begränsning utgick studien från åtta scenarion med olika förutsättningar och olika fokus. Tidsramen var fram till 2030.

    Scenario 1 - Transport: I scenario 1 var fokus att göra transportsektorn förnybar. Biogas och el från vind- kraft ansågs vara de energikällor som bäst ersätter de fossila bränslena. Import av biodiesel bedömdes även nödvändig, framför allt till tung transport. Utmaningen ligger främst i den omfattande omställ- ningen som krävs av fordonsflottan.

    Scenario 2 - Industri: I scenario 2 fokuserades endast på industrins omställning till förnybar energi. Framför allt cementproducenten Cementa använder en stor andel av Gotlands energi. Alternativet med störst potential, och som bör prioriteras för fortsatta studier, ansågs vara att att elektrifiera Ce- menta.

    Scenario 3 - Bioenergi: I scenario 3 skulle bioenergi användas för att ersätta fossila bränslen, samtidigt som Gotland var självförsörjande på livsmedel. Industrin bortsågs ifrån. De två intressena visade sig vara förenliga.

    Scenario 4, 5 och 6 - Reglering: Scenario 4, 5 och 6 fokuserar alla på olika typer av energilagring och reglering. Detta är nödvändigt i ett energisystem som till stor del bygger på vindkraft och solenergi. Batteriparker, tryckluft, pumpkraft och vätgas studerades som möjliga lagringsmetoder. Främst bat- terier i kombination med vätgas ansågs ha potential på Gotland. Fortsatt breda studier krävs dock.

    Scenario 7 - Ingen kabel: Idag finns en kabel mellan Gotland och fastlandet för import och export av elektricitet. I scenario 7 kan den kabeln inte användas. Stor utbyggnad av vindkraften krävs då, spe- ciellt havsbaserad. För att lättare reglera energin föreslogs att Gotland delas in i mindre system.

    Scenario 8 - Energiplan 2020: Region Gotland har satt upp mål för energisystemet år 2020 i Energiplan 2020. I scenario 8 studerades hur energisystemet skulle kunna se ut om målen uppfylldes. Stora för- ändringar från dagens energisystem skulle krävas.

    Slutsatsen av studien var att fortsatta studier främst ska riktas mot möjliga lagringstekniker, indu- strins energiförsörjning samt samhällets inställning till en energiomställning. Lagringstekniker är en förutsättning för den storskaliga utbyggnad av vindkraft som är nödvändig och som finns potential för. Grundläggande för att nå ett förnybart energisystem är hela samhällets delaktighet. Att kartlägga allmänhetens drivkrafter och motsättningar är därför viktigt.

  • 5.
    Aldahan, Filip
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Svensson Grape, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Beräkning av kostnader för lågaktiv kärnavfallshantering2016Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The surtax in Sweden, which exclusively applies for nuclear power plants, in conjunction with low electricity prices, has forced Swedish nuclear power plants to minimize their expenses.

    At Oskarshamn power plant, estimation of cost, associated with low-level nuclear waste management has been conducted several years ago, but with lacking knowledge about how the calculations were performed. Therefore, the purpose of this project was to establish an independent cost estimation for compactible and non-compactible, low level and medium level nuclear waste. Cost estimates for free released low-level nuclear waste was also performed.

    By analyzing average economic figures from year 2014-2015 and visits on-site, an excel-based calculation template was accomplished. During the on-site studies, several visits to the low-level nuclear waste management facilities at Oskarshamn power plant were made, in order to get an overview of how the handling process works.

    By following the staff around, it was possible to estimate some of the time durations for the different parts in the handling process for compactible lowlevel nuclear waste, that were used in the calculations.

    The price for compactible low-level nuclear waste was calculated to 6,72 - 6,97 kr/kg, depending on the activity level. The non-compactible low-level nuclear waste price was found to vary between 4 – 48 kr/kg.

    The large fluctuations are due to different activity levels and associated additional costs in handling, measuring, final deposition etc.

    For both compactible and non-compactible nuclear waste, the storage cost is a factor that dominates the total cost and that could be minimized. Based on the analysis presented in this work, the cost can be decreased by reducing the storage time and/or store the nuclear waste in a more space efficient way.

    The cost estimate for free released material is low (5,94 – 8,74 kr/kg), which concludes that Oskarshamn power plant may profit from free releasing as much material as possible, due to the fact that it is highly profitable to recycle metals.

  • 6.
    Alenius, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Analys och vidareutveckling av marknadsstyrd effekttariff inom eldistribution: En fallstudie av Sandviken Energi Elnät AB:s effekttariff2017Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master thesis evaluates the incentives of a newly implemented market controlled network tariff by analyzing consumption data and constructing a time-differentiated debiting model. The tariff was implemented by Sandviken Energi Elnät AB and the thesis evaluates its customers consumption data compared to data provided by Sundsvall Elnät AB. The differences in data is evaluated by statistical tests of Students t-test, Bayesian t-test and χ2-test with the result that no statistically significant change in user pattern can be found and thus an elucidation of the incentives must be made in the form of a hourly time-differentiated debating model. The thesis also evaluates the cost incentives of the model compared to spot prices where it is shown that the tariff model can benefit much from the spot prices hourly incentives in its hourly time-differentiated model. Five time-differentiated models were constructed and presented where three uses a color coding scheme. The conclusion is that a color coded time-differentiated tariff should give the costumers clear and cost-effective incentives.

  • 7. Alev, Ullar
    et al.
    Eskola, Lari
    Arumägi, Endrik
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Department of Art History.
    Jokisalo, Juha
    Donarelli, Anna
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Department of Art History.
    Siren, Kai
    Broström, Tor
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Department of Art History.
    Kalamees, Tango
    Renovation alternatives to improve energy performance of historic rural houses in the Baltic Sea region2014In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 77, p. 58-66Article in journal (Refereed)
    Abstract [en]

    This paper analyses renovation alternatives to improve energy performance of historic rural houses in three countries (Estonia, Finland, Sweden) in the Baltic Sea region (cold climate). The study was conducted by a combination of field measurements and simulations. Indoor climate, typical houses and structures as well as the current condition and need for renovation were determined by field measurements. Based on field measurements, indoor climate and energy simulation models were validated and used to calculate energy use for different renovation measures. Energy renovation packages were calculated for different scenarios (minimal influence on the appearance of the house, improvement of thermal comfort, improvement of building service systems) for different energy saving levels. The analysis showed that the improvement of building service systems and the energy source holds the largest energy saving potential. The building envelope of old rural houses needs improvement also due to high thermal transmittance and air leakage. The insulation of the external wall has the largest single energy saving potential of the building's envelope. The results show how energy savings depend on energy saving targets, typology of the building, thermal transmittance of original structures, and building service systems. (C) 2014 Elsevier B.V. All rights reserved.

  • 8.
    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.

  • 9.
    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.

  • 10. 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.

  • 11. 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. 

  • 12.
    Andersson, Emil
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Mathematics.
    Småskalig elproduktion i urban miljö: Fallstudie av elproducerande system på ett handelscentrum2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis investigates if a system for small scale electricity production located in anurban environment can be profitable. The work has been divided up into two parts,one extensive literature study and one case study. The purpose of the literature studywas to investigate the area, resulting in a choice of which technology to be studied indepth in a case study.In the case study a system containing small scale wind turbines and photovoltaicsmounted on Gränby Centrums roof was examined. From data containing wind power,wind direction and total irradiation, possible production from a system weresimulated. Three products of each technology were examined in the simulations.From the simulated production an economic analysis was carried out, this toinvestigate if a system is profitable. The two alternatives that showed the besteconomic result formed the optimal system.The economic analysis showed that none of the investigated alternatives whereprofitable, this because the capital costs exceeded the revenues. The revenues fromthe wind turbines were low because of the poor wind conditions in an urbanenvironment and the revenues from the photovolatics were low because of the lowelectricity price.

  • 13.
    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.

  • 14.
    Andersson, Jonas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Bernström, Vendela
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Törnqvist, Joacim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Hosting Capacity of a Low-Voltage Grid: Development of a Simplified Model to be used in future Solar Roadmaps2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of this bachelor thesis is to assess whether it is possible to create a simplified model that estimates the hosting capacity of a low-voltage grid. The Simplified model is compared with a more elaborate model created by the Built Environment Energy Systems Group (BEESG) at Uppsala University. The Simplified model takes three easily obtainable variables into account. The model created by BEESG allows us to observe both the amount of photovoltaic (PV) power that is installed as well as the voltages in each bus in a grid. The hosting capacity is found by gradually increasing the amount of PV power installed in a low-voltage grid until overvoltage is reached. Simulations with BEESG’s model are done for a week in July when the PV generation has its peak and the load is generally low. The Simplified model is created using linear regression with the calculated values from the BEESG’s model as a reference. The report shows that the Simplified model will give an estimation of the low-voltage grid’s hosting capacity that is comparable to the value calculated with BEESG’s model. The results show that it is rarely the low-voltage grid that restricts the installation of PV facilities and that a high self-consumption is advantageous regarding to the grids hosting capacity.

  • 15.
    Apelfröjd, Senad
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Bülow, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Kjellin, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Eriksson, Sandra
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Laboratory verification of system for grid connection of a 12 kW variable speed wind turbine with a permanent magnet synchronous generator2012In: EWEA 2012 Annual Event, Copenhagen, Denmark, 2012, 2012Conference paper (Refereed)
    Abstract [en]

    In this paper the first laboratory tests of the gridconnection system, connected to a resistiveload, for a vertical axis wind turbine (VAWT)with a permanent magnet generator arepresented. The system is based on a taptransformertopology with a voltage sourceinverter and an LCL-filter. The use of a taptransformer topology eliminates the need for aDC-DC converter to handle the variations inDC voltage. The harmonic content of thecurrents from experiments and simulationsperformed in Simulink using different taps onthe transformer are presented. The simulatedcurrents, fed to the resistive load, have a totalharmonic distortion (THD) of 0.5% to 0.9% forthe different taps. The experimental systemhas a current THD ranging from 1.8% to 2.8%.The difference is expected to be due tounbalances, delays and dead times in theexperimental set-up as the major THDcontribution is from harmonic orders below 11.The results show that an LCL filter can bedesigned to meet the demands on powerquality for grid connection of the system withall the taps of the tap transformer inaccordance with IEEE 519-1992.

  • 16.
    Arumägi, Endrik
    et al.
    Chair of Building Physics and Architecture, Tallinn University of Technology, Estonia.
    Kalamees, Targo
    Chair of Building Physics and Architecture, Tallinn University of Technology, Estonia.
    Broström, Tor
    Gotland University, School of Culture, Energy and Environment.
    Indoor climate in a naturally ventilated unheated medieval church in Harju-Risti, Estonia2010In: 10th REHVA World congress Clima 2010: Sustainable Energy Use in Buildings, 2010Conference paper (Refereed)
    Abstract [en]

    Indoor climate in a naturally ventilated unheated medieval church was analysed to determine if the conditions existing suit for three medieval wooden sculptures forming the Calvary group that were decorated the church until 1958. The values of temperature and RH were measured with data loggers at 1-h intervals inside and outside the church. Ventilation measurements were performed using a passive tracer gas technique. The current study shows that there is a considerable risk in bringing back the medieval sculptures forming the Calvary group to the Harju-Risti Church without creating conditions for indoor temperature and humidity regulation. To start risk assessment it is required to maintain a RH level that prevents the risk of mould growth, reduce fluctuations of air RH annually and in the short term period, avoid of too high and too low humidity levels in church that could cause flaking, peeling and cracking of wooden sculptures.

  • 17.
    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.

  • 18.
    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.

  • 19.
    Balksten, Kristin
    et al.
    Gotland University, School of Culture, Energy and Environment.
    Broström, Tor
    Gotland University, School of Culture, Energy and Environment.
    Myrin, Malin
    Tyréns AB.
    Thelin, Carl
    Tyréns AB.
    Kettunen, Rebeca
    Gotland Museum.
    Mebus, Ulrika
    Gotland Museum.
    Increased use of ruins through secured masonry and comfortable climate2010In: Proceedings of the 7th International Conference on Science and Technology in Archaeology and Conservation, Petra, Jordan, 2010Conference paper (Other academic)
    Abstract [en]

    This paper presents a unique scientific research project, funded by the KK-foundation in Sweden together with several companies participating in the project. A primary goal is to find methods to examine and take care of open masonry constructions thereby enabling an increased use of them in a safe and comfortable way without diminishing their cultural values. A second goal is to establish a long-term cooperation/network of researchers, conservators, engineers, antiquarians and craftsmen that can keep and develop the knowledge. The project takes place in year 2010 and 2011. This paper presents a model of cooperation as well as the ongoing experiment and expected results. The project is divided into three major parts:1) Description and assessment of historic masonry as load bearing structures. 2) Assessment of stone and mortar in old masonry and finding the methods to secure and preserve them. 3) The climate in the ruin with respect to comfort and preservation. The goals for the different parts of this research project are to find the best possible solutions of how to: a) Evaluate the construction of complex masonry structures to enable new additions that are appropriate with respect to statics. b) Find efficient methods to evaluate and conserve the status of the materials (stone, mortar) and walls in old masonry to grant safe accessibility. c) Create a comfortable climate in an open masonry structure without closing it. These three research areas all focus on the historic masonry which at the same time forms the climate shell, the bearer of plaster and the historical setting to the activities that are to take place in the ruin.

  • 20.
    Barrios Rivero, Matías
    Karlsruhe Institute of Technology (KIT), Institute of Applied Geosciences (AGW).
    EVALUATION OF AN AQUIFER THERMAL ENERGY STORAGE (ATES) SYSTEM FOR THE CITY HOSPITAL IN KARLSRUHE (GERMANY)2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The objective of the present study is to evaluate the economic, technical and environmental feasibility of an Aquifer Thermal Energy Storage (ATES) system combined with groundwater heat pumps (GWHP) for providing space cooling and heating for the future surgery building at the city hospital in Karlsruhe. The base case system used as reference for comparison is a system similar to the one currently supplying space cooling from a GWHP system and space heating by the local district-heating network. In addition, two alternative systems were included in the analysis, an Absorption Chiller (AbC) and a Desiccative Evaporative Cooling (DEC) system, both fed from the district-heating network. The study shows that the ATES system combined with a GWHP system is the most environmentally and economically attractive system for the planned facility. The results for the AbC system and the DEC systems show a negative net present value, meaning that this alternative is economically unfeasible. Furthermore, the AbC system and the DEC system do not provide any environmental advantage, showing an annual increase in CO2 emissions compared to the base case. A similar system like the one already providing cooling to some of the facilities would have several advantages over these two alternatives. However, it cannot compete with the ATES system together with GWHP, which apart from providing cooling at slightly higher efficiencies than the base case also delivers heating at high efficiencies. Therefore, it offers great potential savings and also provides an annual reduction in green house gas emissions. Concerning the technical feasibility of the four studied systems, no obstacle or significant barrier could be identified yet.

  • 21.
    Bartusch, Cajsa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Industrial Engineering & Management.
    Alvehag, Karin
    KTH Royal Institute of Technology.
    Further exploring the potential of residential demand response programs in electricity distribution2014In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 125, p. 39-59Article in journal (Refereed)
    Abstract [en]

    Smart grids play a key role in realizing climate ambitions. Boosting consumption flexibility is an essential measure in bringing the potential gains of smart grids to fruition. The collective scientific understanding of demand response programs argues that time-of-use tariffs have proven its merits. The findings upon which this conclusion rests are, however, primarily derived from studies covering energy-based time-of-use rates over fairly short periods of time. Hence, this empirical study set out with the intention of estimating the extent of response to a demand-based time-of-use electricity distribution tariff among Swedish single-family homes in the long term. The results show that six years after the implementation households still respond to the price signals of the tariff by cutting demand in peak hours and shifting electricity consumption from peak to off-peak hours. Studies conducted in the Nordic countries commonly include only homeowners and so another aim of the study was to explore the potential of demand response programs among households living in apartment buildings. The demand-based tariff proved to bring about similar, but not as marked, effects in rental apartments, whereas there are virtually no corresponding evidences of demand response in condominium apartments.

  • 22.
    Bartusch, Cajsa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Industrial Engineering & Management.
    Stikvoort, Britt
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Psychology.
    Residential demand response in the long run: Assessing the effects of a time-of-use power tariff 20 years after implementing it2018In: Behave 2018: Book of Abstracts / [ed] Hackenfort, Markus; Carabias-Hütter, Vicente; Hartmann, Cathérine; Janser, Marcel;: Schwarz, Natalie; Stücheli-Herlach, Peter, Zürich, 2018, p. 30-31Conference paper (Refereed)
  • 23.
    Berggren, Björn
    et al.
    Lund University.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Karlsson, Björn
    Mälardalen University.
    Wall, Maria
    Lund University.
    Evaluation and optimization of a Swedish Net ZEB - Using load matching and grid interaction indicators2012In: Proceedings of the First Building Simulation and Optimization Conference, Loughborough, UK, September 10-11, 2012, 2012Conference paper (Refereed)
    Abstract [en]

    Net Zero Energy Buildings, Net ZEBs, is one of many necessary measures for climate change mitigation as they may reduce the energy consumption in the building sector. The Net ZEB interacts with a grid infrastructure. It is therefore important to consider the interaction with the grid in the design phase.

    This paper reports an evaluation of a proposed designof a Net ZEB in the south of Sweden evaluating load matching and grid interaction using simulated datasets with hourly resolution. The aim was to find a design with as high load matching and as low grid interaction as possible.

    The results show difficulties of achieving a high load matching between the building load and on-site generation, due to the Nordic climate and the relatively low loads during daytime, when the availability of solar energy is high. The building is likely to accomplish the goal of a Net ZEB balance. If higher flexibility is sought, a larger energy storage should be considered.

  • 24.
    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.

  • 25.
    Björlin Svozil, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    The Distribution System Operator: A Changing Role2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the introduction of distributed generation and

    information and communication technology the

    distribution system operator need to adapt to the

    changing circumstances of the market place. This has

    put requirements on the distribution system operator

    to transform from a passive management philosophy

    and become pro-active in its management of the

    system.

    The aim of this report is to investigate how the

    changing market place will put new requirements on

    the distribution system operator and how it will

    transform its business model.

    The pro-active distribution system operator will have

    to manage new type of consumers (Prosumer, DGO/

    Aggregator, TSO) with different contracts and new

    consumer relationships. These new consumers will be

    in need of faster (real-time) and more transparent

    information in order to support the system and its

    system services.

    The Distribution system operator will have to

    transform from being passive and become pro-active

    in order to solve the new requirements that it will

    face, in order to produce value for its consumers and

    partners.

  • 26.
    Blomqvist, Emelie
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Termoelektrisk lagring i system med fjärrvärmeproduktion2014Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With increased deployment ofintermittent renewable energy, such aswind and solar power, energy storagebecomes necessary to help reduceproduction peaks. Thermoelectric EnergyStorage is a method still in researchphase, which stores electricity in hotwater at a temperature of 120 ° C. Thisthesis aims to examine whether theThermoelectric Energy Storage would bepossible to integrate into existingpower generation such as a combined heatand power plant, and how the technologypotentially could function in theelectricity market. ThermoelectricEnergy Storage consists of a chargingprocess and a discharging process, bothoperating by the working fluid CO2. Toincrease the efficiency of theThermoelectric Energy Storage, wasteheat from the district heating networkis integrated.

    A model of the Thermoelectric EnergyStorage has been developed and it wascalculated by thermodynamic propertiesof the working fluid, CO2, in thevarious process steps. Results of themodel consist of a coefficient ofperformance (COP) of the chargingprocess and an efficiency of thedischarge process. A total roundtripefficiency of the system was alsocalculated. Two cooling alternativeswere examined in the model, an opencycle and a closed cycle. The resultsshow that the most effective systemoption includes waste heat in both thecharging and discharging process. Onaverage, the mentioned system optionresulted in an overall efficiency ofabout 98 per cent for an open cycle and83 per cent for a closed cycle.

  • 27.
    Bolander, Dan-Axel
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kapacitetsutnyttjande för Power-to-Heat i svenska fjärrvärmesystem: En studie med befintliga anläggningar i framtida energisystem2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The installation of variable renewable energy sources has rapidly increased during the last decade in several countries. It is likely that it will also increase in Sweden. Such a development could lead to periods of very high power production. In order to keep the stability of the electric grid, curtailment is the most common feed-in management method. This study examines how Power-to-Heat can utilize this surplus power in Swedish district heating systems instead of using curtailments and thereby facilitate the development of installed variable renewable energy sources.

    During this study a model was developed in MatLab where the capacity utilization was simulated for Power-to-Heat. The study indicates that the capacity utilization varies from 1,1–4,2 TWh electricity. In this scenario a share of the base load is substituted with new installed wind and solar power; 50 TWh respectively 10 TWh. The parameter that showed greatest sensitivity for the analysis were how the net power profile was simulated.

  • 28.
    Boman, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Fjärrvärmedriven absorptionskyla i Hedemora och Säter2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Hedemora Energi produces and distributes district heating in Hedemora and Säter. It is during the summer in these cities, as in the rest of the country, a low heating demand. By offering its customers district heating driven absorption cooling, this could be a way to satisfy more requests while being able to sell more heat and better use the available capacity. 

    In this thesis the cooling potential in Hedemora and Säter is calculated. Furthermore, the impact of integrated absorption chillers on district heating production, as well as absorption cooling profitability for Hedemora Energi is investigated. Simulations and calculations show that the system need to be adjusted for absorption cooling by increasing the supply temperatures during the hours that they are below the requirements of the absorption chillers. In addition, the adjustments cause raised return temperatures and altered flows in the network. This results in increased fuel costs and heat losses, reduced flow revenues and reduced heat supplies from flue gas condensers. Despite this, the economic results are positive for all cases. For example, over 44 thousand SEK in annual profit after integration of absorption chillers, producing 422 MWh of cooling in Skönvik, Säter.

  • 29.
    Borggren, Lisa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Grill, Rebecca
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Lykken, Susanna
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Nilsson, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Demand based price determination for electricity consumers in private households2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report investigates the effects a demand based tariff would have on private electricity consumers and how it could contribute to a sustainable electrical grid. The fuse tariff that is currently used charges customers for their electricity usage and does not fully reflect the electrical grid load and thereby not the cost for the distribution system operators. A demand based tariff, that charges customers for their power peaks and promotes a change of behaviour better reflects the grid load and could lead to a more even grid distribution and a sustainable development. In light of this issue, two demand based tariffs have been constructed for the energy company Upplands Energi’s private customers’ current electricity consumption. One of the tariffs consists of a higher fixed cost and a lower variable cost and the other consists of a lower fixed cost and a higher variable cost, both leading to the same revenue för Upplands Energi. The two different demand based tariffs have been simulated and analysed, where the one with the lowest fixed cost is recommended since it gives customers higher economic incentives to change their electricity usage behaviour. It is essential that electricity retailers communicate the information of how the demand based tariff works to the customers in order to make them change their electricity behaviour to attain a sustainable grid.

  • 30.
    Borràs Morales, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Park optimization and wake interaction study at Bockstigen offshore wind power plant2014Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Losses for wake effects in offshore wind farms represent about 10% to 20% of the park annual energy production. Several analytical wake models have been developed and implemented to predict the power deficit of a wake-affected wind turbine. Validating and parameterizing the wake models available in the industry is essential to better predict the wake losses and thus maximize the energy yield of future offshore developments.

    In this study, a wake model validation is undertaken for the three models available in the commercial software WindSim. Data from Horns Rev wind farm is used to that purpose. Next, the models that show the best agreement with the observations are parameterized to better describe the power losses of a future offshore wind farm at Bockstigen. To finish with, an optimization sensitivity study is carried out and a final optimal layout is determined according to the seabed depth.

  • 31.
    Boström, Christoffer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Optimization of a Household Battery Storage: The Value of Load Shift2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Sweden’s energy system is facing major changes in the near future in order to reducecarbon emissions and to switch to sustainable energy sources. PV systems havebecome a sensible alternative for homeowners that want to be a part of this changeand at the same time reduce the cost of their electricity bill. To further improve theutilization of their PV system and to handle the intermittent nature of solar power,battery storages have become an interesting system complement. This thesisinvestigates how batteries can provide smart services; load shift and peak price energyutilization to a household. This is done by developing an optimized battery algorithmmodel that can provide these smart services which is compared to a simple batteryalgorithm. The results show that the developed battery optimization model works asintended. It performs both load shift and peak price energy utilization. The economicanalysis shows that the most profitable PV system and battery configuration is a 20kW PV system with a 5 kWh battery. The system has an internal rate of return, IRR,of 2.3% which does not reach Vattenfall’s weighted average cost of capital, WACC, at7%. The results also show that the battery cost is an important factors for a system'sprofitability. A larger battery system is more expensive and the increased yield doesnot cover the increased cost. Further research is needed to implement the optimizedbattery as a functional application since the model has access to a perfect forecast andthus a method for forecasting PV production and load profile of the household arecrucial to get similar results.

  • 32.
    Boström, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Bränslecellsystem för strömförsörjningsbehov i Försvarsmakten2011Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Swedish Defence Materiel Administration (FMV) has since 2003 been running a fuel cell programme with the purpose to increase the Armed Forces knowledge of fuel cell technology and its potential for future applications. This work has been performed as a part of the Armed Forces "Dual-Use"-programme which goal is to identify potential strategic technologies for both civilian and military purposes.

    Specific fuel cell technology advantages relevant to military activities are low acoustic and infra red signature and high fuel density which potentially means lower risk of detection compared to combustion systems and notably longer operating times in comparison to batteries. Furthermore, they can be constructed to be fuel flexible and be designed to handle everything from pure hydrogen to high sulphur diesel fuel.

    The question now is which applications in the Armed Forces that can actually benefit from a power supply system which allows for longer operating times than batteries yet is quieter than a combustion engine.

    The task has been solved partly by studies of the results and conclusions of already conducted reports and partly by interviewing key personnel in relevant positions for each of the proposed power supply systems.

    Two applications has been selected to be studied in more detail; a battery charging system and a power supply system for an Autonomous Underwater Vehicle (AUV).

     The battery charging system is intended to meet the power supply demands of small ranger or reconnaissance units required to operate independently of other forces for up to three weeks.  The maximum power requirement was calculated to be approximately 90 W at the maximum recommended charge current the radio battery being normative. However, if a longer charge time is acceptable this power requirement could be reduced and along with it the system weight and volume.

     

    For the AUV application three cases were formulated; 1) Only battery power 2) Only fuel cell power 3) Fuel cell power handles base load and battery power handles peak load. The results showed calculated operational times of 11, 20 and 24 hours respectively.

    In addition to these results, technical specifications have been produced for each application. These are included as attachments.

  • 33.
    Bras, Patrice
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Midsummer AB, Elektronikhojden 6, SE-17143 Jarfalla, Sweden..
    Mauvy, Leo
    Midsummer AB, Elektronikhojden 6, SE-17143 Jarfalla, Sweden..
    Sterner, Jan
    Midsummer AB, Elektronikhojden 6, SE-17143 Jarfalla, Sweden..
    Platzer-Björkman, Charlotte
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Uniformity assessment of a 6-inch Copper-Zinc-Tin-Sulfide solar cell sputtered from a quaternary compound target2015In: 2015 IEEE 42ND PHOTOVOLTAIC SPECIALIST CONFERENCE (PVSC), 2015Conference paper (Refereed)
    Abstract [en]

    Cu2ZnSnS4 solar cells are fabricated following an all-sputtering in line vacuum approach. 6-inch semi-square stainless steel substrates are used. A compositional and structural study of the absorber layer is conducted before and after annealing to assess the uniformity of both the sputtering and the annealing process. It is found that while the precursors are uniform both in morphology and composition, the annealing process introduces differences in grain size and metal content depending on the area considered on the 6-inch substrate. The corresponding solar cell is further divided into 184 small cells of 1 cm(2) to check the performance distribution across the device. Current-voltage characteristics and solar cell parameters are extracted. Natural convection inside the annealing chamber is suggested to affect significantly the heat distribution and a strong correlation between device performance and local temperature can be identified.

  • 34.
    Brodersson, Anna Lilly
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Mathematics, Applied Mathematics and Statistics.
    Flygbesiktning av Luftledningar: Modellering av samband mellan besiktningsanmärkningar och systemtillförlitlighet2014Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This paper thoroughly investigates needs and requirements for overhead distribution feeder inspection and develops models to investigate possible relations between short term inspections remarks and outages. The study was conducted in collaboration with Fortum Distribution AB that supplied extensive information about their overhead power feeders concerning both inspection and power outages. The investigated models where lognormal linear model, Poisson generalized linear model and negative binomial generalized linear model. All models were implemented utilizing offset terms to compensate for differences in feeder length and amount of overhead versus underground feeders. The Poisson generalized linear model was rejected at an early stage due to overdispersion and neither of the remaining models fit the data perfectly. There for conclusions were primarily concluded from similarities and differences amongst the models. The results either implicate that maintenance is scheduled sufficiently fast, with respect to short term inspection, to ensure a high system reliability or no relationships between short term inspection and feeder outages exist. Therefore the final conclusion was that maintenance and reinvestment decisions should not be based on short cycle inspection data.

  • 35.
    Broström, Tor
    Gotland University, School of Culture, Energy and Environment.
    Handbok i hållbar energianvändning för kyrkan2008Book (Other academic)
    Abstract [sv]

    Kyrkans skapelseansvar går hand i hand med vårt gemensamma ansvar för en hållbar livsstil och jordens överlevnad. Handbok i hållbar energianvändning för kyrkan ger handfasta ekonomiska tips på hur man kan effektivisera energianvändningen i kyrkans byggnader. I boken tar bl.a. upp: Ventilation, fjärr- och närvärme, belysning, energideklarationer, vattenförbrukning, solvärme, klimatskal och isolering, transporter, energispartips och biobränsle. Boken ger också råd om uppvärmning och vad som är viktigt att beakta vid ändrad användning av kyrkobyggnaden. Boken vänder sig i första hand till verksamhets- och driftsansvariga i församlingar, samfälligheter och stift, men också till miljösamordnare och antikvarier.

  • 36.
    Broström, Tor
    Gotland University, School of Culture, Energy and Environment.
    Preventive conservation by climate control in historic buildings2008In: Preservation and conservation in 21st century : knowledge, challenge, attitude :: preprints of the 8th Triennal Meeting for Conservators of the Baltic States, Tallinn, 7-10 May 2008 / [ed] Pia Ehasalu, Kriste Sibul, Talinn: Conservation Centre Kanut , 2008, p. 56-59Chapter in book (Refereed)
    Abstract [en]

    This paper shows how we can work step by step to design appropriate climate control systems. We know enough about climate specifications to reduce risks significantly. The specifications for preservation should be wheighed against other factors in a risk assessment, methods used in museums need to be adapted for this purpose. A climate analysis will give the basic conditions for climate control. A climate control strategy should use a combination of passive control, ventilation, heating and humidity control to achieve the desired indoor climate at low cost and with minimal impact on the building.

  • 37.
    Broström, Tor
    Tekniska högskolan i Stockholm. Institutionen för energiteknik.
    Uppvärmning i kyrkor: fukt- och värmetekniska beräkningar för dimensionering och klimatstyrning1996Doctoral thesis, monograph (Other academic)
  • 38.
    Broström, Tor
    et al.
    Gotland University, School of Culture, Energy and Environment.
    Hagentoft, Carl-Eric
    Chalmers University of Technology.
    Wessberg, Magnus
    Gotland University, School of Culture, Energy and Environment.
    Humidity Control in Historic Buildings through Adaptive Ventilation: a Case Study2011In: NSB 2011: 9th Nordic Symposium on Building Physics, 2011, p. 1-8Conference paper (Refereed)
    Abstract [en]

    Adaptive ventilation, controlled with respect to absolute humidity inside and outside a building, canbe used to reduce RH below risk levels for biodeterioration. In the present case study, adaptiveventilation was used in a historic stone building with severe moisture problems. Measurementscarried out over a year shows that ventilation had a significant drying effect. The mould risk is keptat an acceptable level with exception of two short periods .Short term variations in RH are acceptableaccording to conservation standards. Heating or dehumidification as an auxiliary measure would beneeded only for a short period of time. The performance can be improved by increased fan capacityand improving air tightness of the building.

  • 39.
    Broström, Tor
    et al.
    Gotland University, School of Culture, Energy and Environment.
    Klenz Larsen, Poul
    Gotland University, School of Culture, Energy and Environment.
    Climate control strategies for occasionally used churches: heat, dehumidify, ventilate – or do nothing2012In: Cultural heritage preservation : EWCHP- 2012: proceedings of the 2nd European workshop on cultural heritage preservation / [ed] Elin Dahlin, Kjeller: NILU, Norwegian Institute for Air Research , 2012, p. 124-130Conference paper (Refereed)
  • 40.
    Broström, Tor
    et al.
    Gotland University, School of Culture, Energy and Environment.
    Leijonhufvud, Gustaf
    Gotland University, School of Culture, Energy and Environment.
    Heat pumps for conservation heating2008In: Proceedings of the 8th symposium on building physics in the Nordic countries: Copenhagen, June 16-18, 2008 / [ed] Carsten Rode, Lyngby: Technical university of Denmark , 2008, p. 1143-1150Conference paper (Refereed)
    Abstract [en]

    Conservation heating is used to control relative humidity in order to better preserve historic buildings and their interiors. The heating load for conservation heating when applied in a Nordic climate was characterized in order to investigate if and how air-to-air heat pumps can be used for conservation heating. Heating for conservation results in indoor temperatures that follow the seasonal variation of the outdoor temperature. Depending on the season and moisture load on the building, the indoor temperature will be 0-10 °C higher than the ambient temperature. The heating load is much smaller and more stable over the year as compared to heating for comfort. In the south of Sweden conservation heating is motivated mainly by preservation aspects, whereas in northern Sweden the potential for energy saving is considerable. Heat pumps in general and air-to air heat pumps in particular, have properties that match the requirements of conservation heating and can provide a cost effective solution. Heat pumps specially designed for conservation heating could improve the performance radically in relation to standard heat pumps.

  • 41.
    Broström, Tor
    et al.
    Gotland University, School of Culture, Energy and Environment.
    Leijonhufvud, Gustaf
    Gotland University, School of Culture, Energy and Environment.
    Hållbarhet och byggnadsvård2011In: Energiboken: energieffektivisering för småhusägare / [ed] Eva Löfgren & Paul Hansson, Stockholm: Svenska byggnadsvårdsföreningen , 2011, p. 34-45Chapter in book (Other (popular science, discussion, etc.))
  • 42.
    Broström, Tor
    et al.
    Gotland University, School of Culture, Energy and Environment.
    Leijonhufvud, Gustaf
    Gotland University, School of Culture, Energy and Environment.
    The Indoor Climate in Skokloster Castle2010In: Historical buildings as museums: Systems for climate control and heritage preservation / [ed] Davide Del Curto, Firenze: Nardini Editore , 2010, p. 84-93Conference paper (Refereed)
    Abstract [en]

    Skokloster castle is a heavy stone and brick building without any active climatization. It houses a large collection of artefacts shown in their historic environment without any showcases. The objective of this study is to analyse the indoor climate, make a risk assessment and to propose interventions to improve the indoor climate with respect to the long term preservation of the collection. Relative humidity and temperature have been monitored within the castle for more than one year. Air exchange in selected rooms has been measured quarterly using diffusive sampling. The indoor climate is characterized by extremely low temperatures and high relative humidity in the winter. Even though the building does reduce the effect of outdoor variations, the variations in the indoor climate are larger than one would prefer in a museum. The primary risks associated with the indoor climate are mould growth, mechanical damages and chemical degradation. The variations in RH can be reduced by enhancing the effective hygrothermal inertia of the building through a reduction of the air exchange. In order to substantially reduce the mould risk, conservation heating and/or dehumidification would be needed.

  • 43.
    Broström, Tor
    et al.
    Gotland University, School of Culture, Energy and Environment.
    Linden, Elisabet
    University of Gavle, Department of Built Environment.
    Lindström, Svante
    University of Gavle, Department of Built Environment.
    Mattsson, Magnus
    University of Gavle, Department of Built Environment.
    Sandberg, Mats
    KTH Research School, University of Gavle.
    Convective heating in a medieval church: Effects of air-to-air heat pumps on air movements, particle deposition and temperature distribution2009In: Proceedings of the 11th International Conference on Air Distribution in Rooms (Roomvent) 2009, Busan, Korea, 2009Conference paper (Refereed)
    Abstract [en]

    In Europe many historic buildings use direct electric heating. Air-to-air heat pumps are an interesting alternative, in particular for conservation heating. However, the convective heating may accelerate soiling of walls and artefacts by increasing the velocity and turbulence. The objective of the present paper is to discuss the general problem, the methodology for studying air motions and temperature distribution, and to present the results from a case study where air-to-air heat pumps and bench heaters were used for heating in a medieval church. The temperatures, velocities and humidity in the church have been measured for four different heating modes. The present study does not indicate any major disadvantages of using heat pumps for background heating in stone churches of the studied kind. More detailed long term studies are needed to ascertain the effects over time.

  • 44.
    Broström, Tor
    et al.
    Gotland University, School of Culture, Energy and Environment.
    Nilsen, Lisa
    Energy Efficiency in Historic Buildings: Postprints from the Conference : Visby, February 9–11, 20112012Conference proceedings (editor) (Other academic)
    Abstract [en]

    Energy efficiency is an issue that brings the trade-off between aspects of use and preservation to a head. On the one hand, interventions for energy efficiency facilitate long-term use by reducing operating costs; on the other hand, the interventions may have both a physical and a visual impact on the cultural heritage value and the fabric of the building.

    In order to promote a sustainable use and preservation of historic buildings, The Swedish Energy Agency instituted a National Research Program for Energy Efficiency in HistoricBuildings. The first stage of the program ranfrom 2007 to 2010 with a total budget of around 4 million Euro. Additional funding was provided by the Church of Sweden and the NationalHeritage Board. There were fifteen projects involving some thirty researchers from different Swedish universities and research institutes.

    To mark the end of the first stage of the national research program the international conference Energy Efficiency in Historic Buildings was held in Visby in February 2011. Most of the projects within the program were presented at the conference and international key-note speakers were invited to each session, giving a total of 24 papers. More than one hundred participants, representing ten countries, participated in the conference.

  • 45.
    Broström, Tor
    et al.
    Gotland University, School of Culture, Energy and Environment.
    Nilsson, Håkan
    WSP Environmental, Department of Building Physics.
    Climate Comfort Measurements in Swedish Churches Equipped with New Heating System2008In: Proceedings of the 7th International Thermal Manikin and Modeling Meeting, University of Coimbra , 2008Conference paper (Refereed)
    Abstract [en]

    Many church buildings in Sweden have problems with rising heating costs combined with deterioration of inventories as a consequence of an inappropriate indoor climate. Gotland University has in collaboration with Gotland's churches installed a new radiant heating system for churches. The developed system has floor heating and bench heating pads combined with radiant heaters hanging from above the bench rows. These new installations have now been evaluated with respect to thermal climate comfort. The results show that the clothing of course plays an important role even with help radiant heaters and bench heat pads. Persons on both sides of the instrument as well as the height of the heaters do seem to play a smaller role in this investigation. An important parameter to check is the risk for drought that clearly is dependent on of the construction of the church benches.

  • 46.
    Broström, Tor
    et al.
    Gotland University, School of Culture, Energy and Environment.
    Nordström, Anders
    Historiska Hus, Umeå, Sweden.
    Climate Control in Churches in Northern Sweden2009In: Proceedings Cold Climate HVAC Sisimiut, Greenland, 16-19 March 2009, 2009Conference paper (Refereed)
    Abstract [en]

    In the extreme north of Sweden, the indoor climate and energy performance of 50 churches is being monitored in order to improve energy efficiency and to improve the indoor climate with respect to the preservation. The objective of the present paper is to investigate if and how both indoor climate and energy efficiency can be improved through better climate control. Three cases were chosen to study churches with no heating, permanent heating and intermittent heating. In each case the actual indoor climate was compared to climate criteria for preservation to determine the consequences in terms of climate control. The results show that there is a conflict between the climate criteria for preservation and the present use of the churches that cannot be resolved by technical solutions only. In order to come up with reasonable compromise research is needed on climate criteria and risk management at extremely low ranges of RH.

  • 47.
    Broström, Tor
    et al.
    Gotland University, School of Culture, Energy and Environment.
    Svanström, Karin
    Gotland University, School of Culture, Energy and Environment.
    Solar energy and cultural-heritage values2011In: World Renewable Energy Conference, Linköping, May 2011: Volume 8 (Low-Energy Architecture) / [ed] Moshfegh, Bahram, Linköping: Linköping University Electronic Press, 2011, p. 2034-2040Conference paper (Refereed)
    Abstract [en]

    The use of solar energy in a building of cultural-heritage value is an issue that brings the trade-off between aspects of use and preservation to a head. A sustainable use and preservation of historic buildings requires broad and long term compromises between social, economic and environmental aspects. The objective of the present paper is to present and discuss a decision framework for such compromises regarding the use of solar energy in historic buildings.

  • 48.
    Brunskog, Maria
    Gotland University, School of Culture, Energy and Environment.
    Energieffektivisering i byggnader av kulturhistoriskt intresse med avseende på kyrkor i Luleå stift2011Report (Other academic)
  • 49.
    Bydell, Linn
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Evaluation of the thermal-hydraulic software GOTHIC for nuclear safety analyses2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of this master theses was to evaluate the thermal-hydraulic calculation software GOTHIC for the purpose of nuclear containment safety analyses. The evaluation was performed against some of the Marviken full scale containment experiments and a comparison was also made against the two codes RELAP5 and COPTA. Models with different complexity were developed in GOTHIC and the parameters pressure, temperature and energy in different areas of the enclosure was investigated.

    The GOTHIC simulations in general showed a good agreement with the Marviken experimental results and had an overall better agreement then RELAP5. From the results it was possible to conclude that the developed GOTHIC model provided a good representation of the Marviken facility. 

  • 50.
    Bülow, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    A Generator Perspective on Vertical Axis Wind Turbines2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The wind energy conversion system considered in this thesis is based on a vertical axis wind turbine with a cable wound direct drive PM generator. Diode rectifiers are used to connect several such units to a single DC-bus and a single inverter controls the power flow from the DC-bus to a utility grid. This work considers the described system from a generator perspective i.e. the turbine is primarily seen as a torque and the inverter is seen as a controlled load.

    A 12 kW VAWT prototype with a single turbine has been constructed within the project. The power coefficient of this turbine has been measured when the turbine is operated at various tip speed ratios. This measurement determines both how much energy the turbine can convert in a given wind and at what speed the turbine should be operated in order to maximise the energy capture. The turbine torque variation during the revolution of the turbine has also been studied.

    A PM generator prototype has been constructed in order to study power loss in the stator core at low electrical frequencies. Heat exchange between the stator and the air-gap between the stator and the rotor has been studied. Heat exchange between the stator and the air-gap is increased by turbulence caused by the rotor. The generator was also used in a demonstration of a DC-grid where two diode rectified PM generators supplied power to a single DC load.  An initial study of an inverter suitable for grid connection of the 12 kW PM generator has been performed.

    Several turbine control strategies are evaluated in simulations. The control strategies only require the parameter "turbine speed" to determine the optimal system load.

    List of papers
    1. Offshore underwater substation for wave energy converter arrays
    Open this publication in new window or tab >>Offshore underwater substation for wave energy converter arrays
    Show others...
    2010 (English)In: IET Renewable Power Generation, ISSN 1752-1416, Vol. 4, no 6, p. 602-612Article in journal (Refereed) Published
    Abstract [en]

    In this study, the design, construction, deployment and operation of an offshore underwater substation is discussed. The seabed placed substation interconnects three linear generator wave energy converters (WECs) at the Swedish Lysekil wave energy research site. The power from the WECs fluctuates because of their direct-driven topology. The generator voltage has varying electrical frequency and amplitude. To reduce the fluctuations, the individual voltages of the WECs are rectified and the power is added on a common DC-bus in the substation. The voltage is inverted, transformed and power is transmitted to an on-shore resistive load. The substation was retrieved on two occasions since the deployment in the spring of 2009. The functionality of the substation is validated by comparing voltage and current wave forms from Simulink with measured results from laboratory experiments. In addition, a sample of results from real offshore operation is illustrated and discussed. With a proportional-integral-derivative (PID)-regulator in the inverter control, the small fluctuations in the DC-bus voltage could be minimised. However, this would reduce the energy storage capability of the DC-link smoothing capacitors.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-112954 (URN)10.1049/iet-rpg.2009.0180 (DOI)000284511300013 ()
    Available from: 2010-01-22 Created: 2010-01-22 Last updated: 2018-05-31Bibliographically approved
    2. Power coefficient measurement on a 12 kW straight bladed vertical axis wind turbine
    Open this publication in new window or tab >>Power coefficient measurement on a 12 kW straight bladed vertical axis wind turbine
    Show others...
    2011 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 36, no 11, p. 3050-3053Article in journal (Refereed) Published
    Abstract [en]

    A 12 kW vertical axis H-rotor type wind turbine has been designed and constructed at Uppsala University. A measurement campaign has been performed to collect data to calculate the power coefficient using the method of bins. The measurement was performed at different constant rotational speeds on the turbine during varying wind speeds to observe the power coefficients dependence on tip speed ratio. The power coefficient peaked at 0.29 for a tip speed ratio equal to 3.3.

    Keywords
    VAWT, H-rotor, Experimental, Measured, Cp
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Science of Electricity
    Identifiers
    urn:nbn:se:uu:diva-156579 (URN)10.1016/j.renene.2011.03.031 (DOI)000292441400035 ()
    Available from: 2011-08-07 Created: 2011-08-04 Last updated: 2018-05-30Bibliographically approved
    3. Adapting a VAWT with PM generator to telecom applications
    Open this publication in new window or tab >>Adapting a VAWT with PM generator to telecom applications
    Show others...
    2010 (English)In: European Wind Energy Conference & Exhibition, Warsaw, Poland, 2010Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    Warsaw, Poland: , 2010
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-142522 (URN)
    Conference
    European Wind Energy Conference & Exhibition
    Available from: 2011-01-14 Created: 2011-01-14 Last updated: 2018-05-30Bibliographically approved
    4. No-load core loss prediction of PM generator at low electrical frequency
    Open this publication in new window or tab >>No-load core loss prediction of PM generator at low electrical frequency
    2012 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 43, p. 389-392Article in journal (Refereed) Published
    Abstract [en]

    A method for measurement of frequency dependent electromagnetic core loss of a permanent magnet generator is presented. Core loss of a PM generator is measured at electrical frequencies ranging from 4 to 14 Hz. Core loss in the same interval is simulated using the finite element method and frequency domain loss separation. The specific loss is both extrapolated from specific loss at 50 Hz and measured directly at 4, 8, 12 and 16 Hz. Core loss simulations based on extrapolated specific loss are 38–53% smaller than measured loss. Core loss simulations based on specific loss measured at 4, 8, 12 and 16 Hz are 19–23% smaller than measured loss.

    Keywords
    Core loss Variable speed PM generator Cable wound generator Loss separation
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Science of Electricity
    Identifiers
    urn:nbn:se:uu:diva-190099 (URN)10.1016/j.renene.2011.12.002 (DOI)000301311500042 ()
    Available from: 2013-01-07 Created: 2013-01-07 Last updated: 2017-12-06Bibliographically approved
    5. Robust VAWT control system evaluation by coupled aerodynamic and electrical simulations
    Open this publication in new window or tab >>Robust VAWT control system evaluation by coupled aerodynamic and electrical simulations
    2013 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 59, p. 193-201Article in journal (Refereed) Published
    Abstract [en]

    A control system for a vertical axis wind turbine is presented.The control strategy is to determine the electric load solely from the rotational velocity and the characteristics of the turbine, thus measurement of the incoming wind velocity is not required.The control system is evaluated with an aerodynamic vortex model coupled with an electrical model.Three different sets of control system parameters are tested, due to the trade off between high power absorption and achieving a fast system with high stability.The control systems are tested against a reference strategy where the wind speed is known.The simulations show that the three control systems provide a similar power absorption as the reference case.For dynamic cases, with fast changes in wind speed, the fast control strategies are beneficial.All control strategies are stable throughout the simulations when proper power absorption characteristics of the turbine are used. It is also shown that if peak power absorption is estimated at a too low tip speed ratio, the control strategies may inadvertently stop the turbine.

    Place, publisher, year, edition, pages
    Elsevier, 2013
    Keywords
    Wind power, VAWT, Darrieus Turbine, Control system, Numerical simulation, Vortex method
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Science of Electricity
    Identifiers
    urn:nbn:se:uu:diva-183738 (URN)10.1016/j.renene.2013.03.038 (DOI)000320827300024 ()
    Available from: 2012-11-01 Created: 2012-11-01 Last updated: 2017-12-07Bibliographically approved
    6. Aerodynamic and electrical evaluation of a VAWT farm control system with passive rectifiers and mutual DC-bus
    Open this publication in new window or tab >>Aerodynamic and electrical evaluation of a VAWT farm control system with passive rectifiers and mutual DC-bus
    2013 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 60, p. 284-292Article in journal (Refereed) Published
    Abstract [en]

    A wind farm with a simple electrical topology with passive rectifiers and a single inverter (mutual topology) is compared to a more complex topology where each turbine has a separate inverter (separate topology).In both cases, the turbines are controlled electrically by varying the extracted power with the rotational velocity as control signal.These two electrical topologies are evaluated with respect to absorbed power for a farm of four turbines placed either on a line or in a square formation.The evaluation is done with an aerodynamic vortex model coupled with an electrical system model.Simulations predict that individual control is beneficial for aerodynamically independent turbines if flow velocities differ significantly between turbines. If the differences in flow velocities are caused by one turbine operating in the wake of another, the deviations in power output between the topologies are less prominent.The mutual topology even deliver more power than the separate topology when one turbine is in the wake of another turbine if the wind speed changes rapidly.

    Place, publisher, year, edition, pages
    Elsevier, 2013
    Keywords
    Wind power, Wind farm, VAWT, Vortex model, Control system
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Science of Electricity
    Identifiers
    urn:nbn:se:uu:diva-183739 (URN)10.1016/j.renene.2013.05.028 (DOI)000323628600031 ()
    Available from: 2012-11-01 Created: 2012-11-01 Last updated: 2017-12-07Bibliographically approved
    7. Torque ripple of a straight-bladed Darrieus turbine with PM generator estimated from diode rectifier output current.
    Open this publication in new window or tab >>Torque ripple of a straight-bladed Darrieus turbine with PM generator estimated from diode rectifier output current.
    (English)Manuscript (preprint) (Other academic)
    National Category
    Energy Systems
    Identifiers
    urn:nbn:se:uu:diva-197853 (URN)
    Available from: 2013-04-05 Created: 2013-04-05 Last updated: 2013-08-30
    8. Stator cooling by axial flow through air-gap of high torque PM generator.
    Open this publication in new window or tab >>Stator cooling by axial flow through air-gap of high torque PM generator.
    (English)Manuscript (preprint) (Other academic)
    National Category
    Energy Systems
    Identifiers
    urn:nbn:se:uu:diva-197854 (URN)
    Available from: 2013-04-05 Created: 2013-04-05 Last updated: 2013-08-30
    9. Laboratory verification of system for grid connection of a 12 kW variable speed wind turbine with a permanent magnet synchronous generator
    Open this publication in new window or tab >>Laboratory verification of system for grid connection of a 12 kW variable speed wind turbine with a permanent magnet synchronous generator
    2012 (English)In: EWEA 2012 Annual Event, Copenhagen, Denmark, 2012, 2012Conference paper, Poster (with or without abstract) (Refereed)
    Abstract [en]

    In this paper the first laboratory tests of the gridconnection system, connected to a resistiveload, for a vertical axis wind turbine (VAWT)with a permanent magnet generator arepresented. The system is based on a taptransformertopology with a voltage sourceinverter and an LCL-filter. The use of a taptransformer topology eliminates the need for aDC-DC converter to handle the variations inDC voltage. The harmonic content of thecurrents from experiments and simulationsperformed in Simulink using different taps onthe transformer are presented. The simulatedcurrents, fed to the resistive load, have a totalharmonic distortion (THD) of 0.5% to 0.9% forthe different taps. The experimental systemhas a current THD ranging from 1.8% to 2.8%.The difference is expected to be due tounbalances, delays and dead times in theexperimental set-up as the major THDcontribution is from harmonic orders below 11.The results show that an LCL filter can bedesigned to meet the demands on powerquality for grid connection of the system withall the taps of the tap transformer inaccordance with IEEE 519-1992.

    Keywords
    VAWT, Tap transformer, LCL-filter, voltage source inverter
    National Category
    Energy Systems Other Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Science of Electricity
    Identifiers
    urn:nbn:se:uu:diva-182434 (URN)
    Conference
    EWEA 2012 Annual Event, Copenhagen, Denmark, 2012
    Available from: 2012-10-10 Created: 2012-10-10 Last updated: 2018-05-30
1234567 1 - 50 of 471
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