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  • 301. Trubetskaya, Anna
    et al.
    Jensen, Peter Arendt
    Glarborg, Peter
    Garcia Llamas, Angel David
    Umeki, Kentaro
    Kling, Jens
    Gardini, Diego
    Bates, Richard B.
    Jensen, Anker Degn
    Effects of Biomass Feedstock on the Yield and Reactivity of Soot from Fast Pyrolysis at High Temperatures2016Other (Other academic)
  • 302.
    Trubetskaya, Anna
    et al.
    Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltoft Plads, Building 229, Kgs. Lyngby 2800, Denmark.
    Jensen, Peter Arendt
    Jensen, Anker Degn
    Llamas, Angel David Garcia
    Umeki, Kentaro
    Gardini, Diego
    Kling, Jens
    Bates, Richard B.
    Glarborg, Peter
    Effects of several types of biomass fuels on the yield, nanostructure and reactivity of soot from fast pyrolysis at high temperatures2016In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 171, p. 468-482Article in journal (Refereed)
    Abstract [en]

    This study presents the effect of biomass origin on the yield, nanostructure and reactivity of soot. Soot was produced from wood and herbaceous biomass pyrolysis at high heating rates and at temperatures of 1250 and 1400 °C in a drop tube furnace. The structure of solid residues was characterized by electron microscopy techniques, X-ray diffraction and N2 adsorption. The reactivity of soot was investigated by thermogravimetric analysis. Results showed that soot generated at 1400 °C was more reactive than soot generated at 1250 °C for all biomass types. Pinewood, beechwood and wheat straw soot demonstrated differences in alkali content, particle size and nanostructure. Potassium was incorporated in the soot matrix and significantly influenced soot reactivity. Pinewood soot particles produced at 1250 °C had a broader particle size range (27.2–263 nm) compared to beechwood soot (33.2–102 nm) and wheat straw soot (11.5–165.3 nm), and contained mainly multi-core structures.

  • 303.
    Trubetskaya, Anna
    et al.
    Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts Plads Bygning 229, Kgs. Lyngby 2800, Denmark.
    Jensen, Peter Arendt
    Jensen, Anker Degn
    Llamas, Angel David Garcia
    Umeki, Kentaro
    Glarborg, Peter
    Effect of fast pyrolysis conditions on biomass solid residues at high temperatures2016In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 143, p. 118-129Article in journal (Refereed)
    Abstract [en]

    Fast pyrolysis of wood and straw was conducted in a drop tube furnace (DTF) and compared with corresponding data from a wire mesh reactor (WMR) to study the influence of temperature (1000-1400)°C, biomass origin (pinewood, beechwood, wheat straw, alfalfa straw), and heating rate (103 °C/s, 104 °C/s) on the char yield and morphology. Scanning electron microscopy (SEM), elemental analysis, and ash compositional analysis were applied to characterize the effect of operational conditions on the solid residues (char, soot) and gaseous products. The char yield from fast pyrolysis in the DTF setup was 3 to 7% (daf) points lower than in the WMR. During fast pyrolysis pinewood underwent drastic morphological transformations, whereas beechwood and straw samples retained the original porous structure of the parental fuel with slight melting on the surface. The particle size of Danish wheat straw char decreased in its half-width with respect to the parental fuel, whereas the alfalfa straw char particle size remained unaltered at higher temperatures. Soot particles in a range from 60 to 300 nm were obtained during fast pyrolysis. The soot yield from herbaceous fuels was lower than from wood samples, possibly due to differences in the content of lignin and resin acids.

  • 304. Trubetskaya, Anna
    et al.
    Jensen, Peter Arendt
    Jensen, Anker Degn
    Steibel, Markus
    Spliethoff, Hartmut
    Glarborg, Peter
    Influence of fast pyrolysis conditions on yield and structural transformation of biomass chars2015In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 140, p. 205-214Article in journal (Refereed)
    Abstract [en]

    Fast pyrolysis of biomass (wood, straw, rice husk) and its major components (cellulose, hemicellulose, lignin) was conducted in a wire mesh reactor. The aim of this study was to understand the influence of temperature (350-1400 ∗ C), heating rate (10-3000 ∗ C/s), particle size (0.05-2 mm) and holding time (1-4 s) on the char morphology and char yield. Scanning electron microscopy (SEM) and elemental analysis were conducted to determine the effect of operating conditions on char softening and melting during pyrolysis. The char yield decreased with heating rate for rates ≤ 600 ∗ C/s; above this value a similar biomass char yield was obtained. The potassium content affected the char yield stronger than other minerals, while the distribution of the three major biomass constituents (cellulose, hemicellulose, lignin) affected the char yield only to a minor degree. Moreover, it was found that the heat treatment temperature had a larger influence on the char yield than the heating rate. Scanning electron microscopy indicated different types of biomass char plasticization influenced by the applied temperatures, heating rates, particle sizes and holding times, except for the rice husk char that formed chars with a structure similar to the parental fuel at all conditions. The less severe morphological changes of rice husk char were attributed to a high silica content.

  • 305. Trubetskaya, Anna
    et al.
    Jensen, Peter Arendt
    Jensen, Anker Degn
    Stiebel, Markus
    Spliethoff, Hartmuth
    Glarborg, Peter
    Larsen, Flemming Hoffmann
    Comparison of high temperature chars of wheat straw and rice husk with respect to chemistry, morphology and reactivity2016In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 86, p. 76-87Article in journal (Refereed)
    Abstract [en]

    Fast pyrolysis of wheat straw and rice husk was carried out in an entrained flow reactor at high-temperatures (1000–1500) °C. The collected char was analyzed using X-ray diffractometry, N2-adsorption, scanning electron microscopy, particle size analysis with CAMSIZER XT, 29Si and 13C solid-state nuclear magnetic resonance spectroscopy and thermogravimetric analysis to investigate the effect of inorganic matter on the char morphology and oxygen reactivity. The silicon compounds were dispersed throughout the turbostratic structure of rice husk char in an amorphous phase with a low melting temperature (≈730 °C), which led to the formation of a glassy char shell, resulting in a preserved particle size and shape of chars. The high alkali content in the wheat straw resulted in higher char reactivity, whereas the lower silicon content caused variations in the char shape from cylindrical to near-spherical char particles. The reactivities of pinewood and rice husk chars were similar with respect to oxidation, indicating less influence of silicon oxides on the char reactivity.

  • 306.
    Trubetskaya, Anna
    et al.
    Department of Energy Engineering, Luleå University of Technology, Luleå 97187, Sweden.
    Poyraz, Yunus
    Weber, Roman
    Wadembäck, Johan
    Secondary comminution of wood pellets in power plant and laboratory-scale mills2017In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 160, p. 216-227Article in journal (Refereed)
    Abstract [en]

    This study aims to determine the influence of mill type and pellet wood composition on particle size and shape of milled wood. The size and shape characteristics of pellets comminuted using power plant roller mills were compared with those obtained by using laboratory-scale roller- and hammer mills. A 2D dynamic imaging device was used for particle characterization. It was shown that mill type has a significant impact on particle size but an almost negligible effect on the shape of milled wood. Comminution in the pilot plant using a Loesche roller mill requires less energy than using a hammer mill, but generates a larger fraction of coarse particles. The laboratory-scale roller mill provides comparable results with the power plant roller mill with respect to particle size and shape.

  • 307. Trubetskaya, Anna
    et al.
    Stiebel, Markus
    Spliethoff, Hartmuth
    Jensen, Anker Degn
    Glarborg, Peter
    Effect of pyrolysis conditions and composition on the char structure and char yield of biomass chars2014Other (Other academic)
  • 308. Trubetskaya, Anna
    et al.
    Stiebel, Markus
    Spliethoff, Hartmuth
    Talbro Barsberg, Søren
    Andersen, Mogens Larsen
    Jensen, Peter Arendt
    Jensen, Anker Degn
    Glarborg, Peter
    Structural and Compositional Transformations of Biomass Chars during Fast Pyrolysis2014Other (Other academic)
  • 309.
    Trubetskaya, Anna
    et al.
    Energy Engineering Department, Luleå University of Technology, 97187 Luleå, Sweden.
    Surup, Gerrit
    Shapiro, Alexander
    Bates, Richard B.
    Modeling the influence of potassium content and heating rate on biomass pyrolysis2017In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 194, p. 199-211Article in journal (Refereed)
    Abstract [en]

    This study presents a combined kinetic and particle model that describes the effect of potassium and heating rate during the fast pyrolysis of woody and herbaceous biomass. The model calculates the mass loss rate, over a wide range of operating conditions relevant to suspension firing. The shrinking particle model considers internal and external heat transfer limitations and incorporates catalytic effects of potassium on the product yields. Modeling parameters were tuned with experimentally determined char yields at high heating rates (>200 K s−1) using a wire mesh reactor, a single particle burner, and a drop tube reactor. The experimental data demonstrated that heating rate and potassium content have significant effects on the char yield. The importance of shrinkage on the devolatilization time becomes greater with increasing particle size, but showed little influence on the char yields.

  • 310. Trubetskaya, Anna
    et al.
    Umeki, Kentaro
    Garcia Llamas, Angel David
    jensen, Anker Degn
    Jensen, Peter Arendt
    Glarborg, Peter
    Effect of Fast Pyrolysis Conditions on Structural Transformation and Reactivity of Herbaceous Biomasses at High Temperatures2015Other (Other academic)
  • 311. Trubetskaya, Anna
    et al.
    Umeki, Kentaro
    Garcia Llamas, Angel David
    Jensen, Anker Degn
    Jensen, Peter Arendt
    Glarborg, Peter
    Effect of Fast Pyrolysis Conditions on the Biomass Solid Residues at High Temperatures (1000-1400°C)2015Other (Other academic)
  • 312.
    Ulander, Stefan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Planeringsverktyg för energiproduktionen på SCA Ortvikens pappersbruk2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Ortvikens pappersbruk i Sundsvall har i dagsläget bristande möjlighet till framförhållning av kommande ångbehov. Det medför att man ofta har fel antal ångpannor i drift, endera för få pannor, dock oftast för många för att säkerställa tillräcklig leverans av ånga till fabriken. Detta leder till dålig reglermån på pannorna samt att man ofta inte kör pannorna under optimala driftsförhållanden, vilket leder till onödigt stora utsläpp av främst NOX och viss onödig oljeförbrukning. Syftet med detta arbete är att ta fram ett planeringsverktyg för energiproduktionen (EPP-verktyget) gällande den förväntade ångproduktionen från Ångcentralen ett dygn framöver, som ett underlag för att optimera ångproduktionen på bruket.

    På Ortviken kommer ungefär hälften av den totalt producerade ångan som en biprodukt från massaproduktionen, andra hälften produceras i Ångcentralen, som utgör den reglerande ångleverantören med dess totalt sex ångpannor.

    Historiska medelvärden från loggade data för ångbehov och ångproduktion från olika driftsförhållanden har varit grunden för beräkningarna som verktyget byggts upp med i Excel. Genom att bl.a. koppla den förväntade elkonsumtionen på bruket, utomhustemperaturen och körscheman på pappersmaskinerna för nästkommande dygn till den förväntade konsumtionen av ånga på Ortviken och produktion av ånga från Massafabriken (TMP), har den förväntade produktionen av ånga från Ångcentralen kunnat beräknas fram med EPP-verktyget.

    Resultatet från simuleringar av EPP-verktyget med aktuella driftsdata på Ortviken visar en förväntad ångproduktion från Ångcentralen som avviker som mest med +- 5 ton/h (ca 5 %) mot det verkliga utfallet, och får ses som en rimlig felmarginal. Den förväntade ångproduktionen från beräkningar i EPP- verktyget tillsammans med trendkurvor över de ångförbrukare som varierar mest och är svårast att förutsäga, gör EPP-verktygets användargränssnitt till ett bra underlag för att ha rätt antal pannor i drift, samt uppmärksamma fel som påverkar ångproduktionen negativt.

  • 313. van Noord, Michiel
    et al.
    Berglund, Torsten
    Murphy, Mark
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Snöpåverkan på solelproduktion: om snöförluster på takanläggningar i Norra Sverige2017Report (Other academic)
  • 314. van Noord, Michiel
    et al.
    Murphy, Mark
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Berglund, Torsten
    Investigating a potential linear model for prediction of monthly snow-induced production losses for rooftop PV2017In: 33rd European Photovoltaic Solar Energy Conference and Exhibition: Proceedings of the International Conference held in Amsterdam, The Netherlands, 25 September – 29 September 2017, 2017, p. 2316-2319Conference paper (Refereed)
    Abstract [en]

    This study investigates the potential of an easy applicable linear model of typical yield losses from PV rooftop systems due to snow coverage, by relating these losses to air temperature. The basis for this study is measurements conducted during two winter seasons, on three locations and a total of six PV systems. A yield prediction model based on “snow free” Performance Ratio is used to calculate daily and monthly snow losses. Correlation of monthly snow loss factors (% of expected yield) with average monthly air temperature is visually analyzed. Three temperature correlation zones are identified: A zone with practically no snow losses, a transition zone and a zone with almost full snow losses. A linear regression is used to model snow loss factors for the transition temperature zone. Comparison with historical data indicates that an improvement of the transition zone model is desirable. Addition of snowfall amounts and/or global irradiation into the model are proposed for future development. 

  • 315.
    Velaga, Sitaram P.
    et al.
    Department of Health Sciences, Luleå University of Technology, Luleå S-971 87, Sweden.
    Vangala, Venu R.
    Department of Health Sciences, Luleå University of Technology, Luleå S-971 87, Sweden.
    Basavoju, Srinivas
    Department of Health Sciences, Luleå University of Technology, Luleå S-971 87, Sweden.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Polymorphism in acesulfame sweetener: structure-property and stability relationships of bending and brittle crystals2010In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 46, no 20, p. 3562-3564Article in journal (Refereed)
    Abstract [en]

    Acesulfame is found to exist in two crystalline forms of which Form I (needles) shows bending upon mechanical stress. Crystal structures explain their mechanical response. This is the first case of aliphatic organic compounds featuring a bending phenomenon. Form I is physically more stable than Form II in ambient conditions.

  • 316.
    Vennström, Per
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Modellering och optimering av Lycksele kraftvärmeverk2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Rising prices for biofuel and a more competitive energy market makes the use of optimization of heat and electricity production in a cogeneration plants necessary. In this report a mixed integer linear programming model of Skogsbacka cogeneration plant, heat storage tank, heat water boiler and Lycksele district heating network is proposed. The model takes into account the forward and return temperature of the water in the district heating network and how it affects the operation of the cogeneration plant and the heat storage tank. A simple model describing the heat demand in the district heating network is also proposed. The model was made in Matlab using Optimization toolbox.The resulting model successfully optimized the energy production of Skogsbacka cogeneration plant with different operation modes such as direct condensing, backpressure operation, auxiliary cooling and flue gas condensation. The model showed that the operation cost for the system could be reduced by 800 000 kr for year 2012, 600 000 kr for year 2013 and 200 000 for the first four months of 2014. The use of flue gas condensing was shown to reduce the operation cost for year 2012 by 1.5 million kr by reducing the amount of fuel used. The use of unique restrictions for Skogsbacka cogeneration plant such as a maximum change in power for the boiler and turbine was required to achieve optimization that were not only possible in theory but also in practice. The model of the heat demand in the district heating network proved to predict the load for longer periods of time but for shorter periods the total heat predicted was not good enough. The model should be improved to take weather conditions such as wind and sun into account.

  • 317.
    Vernersson, Maria
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Solceller för lantbruksbyggnader: Projektering och kartläggning i nätområdet för PiteEnergi2017Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis in energy engineering, on behalf of the energy company PiteEnergi, aim to investigate the potential of solar cell plants for agricultural buildings. Projection of solar cell plants for nine farms have been executed in Piteå municipality, all of which are customers of PiteEnergi. Visits to all nine farms, have been carried out to plan for solar plants where measurements have been made of roof surfaces and buildings. Through measurement data, the system has been reviewed by a design program called” The material calculator”, belonging to the Company Kraftpojkarna, a supplier to PiteEnergi. Furthermore, simulations have been carried out with the simulation program, SolarEdge, to find out the amount of electricity that the plants are expected to produce annually. Based on the design and material needed for installation, investment calculations have been made to calculate which investments and repayment times each individual prospectus has. The results obtained are to be presented, together with this paper, to the farmers who have participated in this thesis, when the project is finished. The main results indicate that it’s more profitable to invest in a larger solar cell plant, as these provide a slightly lower repayment time, even though the initial investment is larger and increases linearly with the installed effect. Most projected solar cell plants in this thesis, have a repayment period of around 14 years without investment support and approximately 10 years including investment support. This with the electricity prices and prices for electricity certificates assumed for the calculations. The expected energy from the solar cells can satisfy several agricultural annual uses of energy. The expected effect of the solar cell system never reaches installed effect in the simulations, and is due to among things like the weather, slope and solar insolation. Conclusions to be made from this work is that solar cell plants are a good investment in Piteå municipality. It’s not only environmentally friendly, but, due to its long-life expectancy, it’s also considered to be a good investment since the repayment period is 30–50 % of its longevity and system prices are continuing to drop. It’s difficult to draw general conclusions between the different prospects when they differ widely in both slope, azimuth, and installed effect. Proposals for further work are to evaluate the network area of PiteEnergi to find out how much power the power grid can handle and how, in the future, it needs to be developed and possibly expanded to meet the demand for photovoltaic cells and solar cell plants.

  • 318.
    Vesterberg, Jimmy
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Improved building energy simulations and verifications by regression2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    It is common with significant differences between calculated and actual energy use in the building sector. These calculations are often performed with whole building energy simulation (BES) programs. In this process the analyst must make several assumptions about the studied building and its users. These calculations are often verified with measured data through the EUI benchmark indicator which is calculated by normalizing the annual energy use (from the grid) with the floor area. Due to the highly aggregated nature of the EUI indicator it is problematic to use this indicator to deduce erroneous assumptions in the calculations. Consequently, the learning process is often troublesome.

    Against this background, the main aim of this thesis has been to develop methods that can provide feedback (key building performance parameters) from measured data which can be used to increase simulation accuracy and verify building performance. For the latter, regression models have been widely used in the past for verifying energy use. This thesis has the focus on the use of regression analysis for accurate parameter identification to be used to increase the agreement between BES predictions and actual outcome. For this, a BES calibration method based on input from regressed parameters has been developed which has shown promising features in terms of accurate predictions and user friendliness. The calibration method is based on input from regressed estimations of air-to-air-transmission losses, including air leakage (heat loss factor) and ground heat loss. Since it is known that bias models still can give accurate predictions, these parameters have been evaluated in terms of robustness and agreement with independent calculations. In addition, a method has been developed to suppress the bias introduced in the regression due to solar gain. Finally, the importance of calibrated simulations was investigated.

    The regressed parameters were found to be robust with yearly variations in the heat loss factor of less than 2%. The regressed estimates of ground heat loss were also in good agreement with independent calculations. The robustness of the heat loss factor based on data from periods of substantial solar gain was also found to be high, with an average absolute deviation of 4.0%. The benefit with calibrated models was mainly found to be increased accuracy in predictions and parameters in absolute terms. With increased access to measured data and the promising results in this thesis it is believed that the presented regression models will have their place in future energy quantification methods for accessing energy performance of buildings. 

  • 319.
    Vesterberg, Jimmy
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Andersson, Staffan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Robustness of a regression approach, aimed for calibration of whole building energy simulation tools2014In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 81, p. 430-434Article in journal (Refereed)
    Abstract [en]

    An approach, able to easily and effectively integrate field measured data in whole Building Energy Simulation (BES) models is crucial to increase simulation accuracy for existing buildings. In this paper the robustness of a linear regression method for extracting transmission losses above ground (including air leakage) and ground heat loss parameters are analyzed. The regression method is evaluated on two documented and monitored multifamily buildings with mechanical supply and exhaust ventilation systems, with and without heat recovery.   

    The obtained results are found to be robust, with variations less than 2% in the extracted estimates of transmission losses above ground (including air leakage) and with a high goodness of fit (R2>0.96) against measured data from two years. In addition, the estimations of the buildings ground heat loss were in good agreement with calculations in accordance with EN ISO 13370:2007. The high quality output from the used regression method serves as good prerequisites for the method to be used in conjunction with BES models to aid the analyst in a BES calibration process

  • 320.
    Vestner, Robin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Optisk mätning av koncentrerade paraboliska solfångare: Kvalitetssäkring av den geometriska formen på tråget2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Absolicon Solar Collector AB has started to investigate the possibility to implement a quickquality insurance for concentrating parabolic solar collectors to their new power train. This will be done by calculating the geometrical shape on the trough by letting cameras move over the through and detect the edges on the reflected receiver pipe. Measure data will be sent to a central computer through Message Queuing Telemetry Transport(MQTT) that handles the calculation of the troughs geometrical shape. The project has been named ARGQOS and is an acronym for Absolicon Robotized GeometricalQuantification Ocular System. In the project eight identical camera houses should be designed, constructed and tested where the camera and the computer would be mounted. LED-lights should also be located on top of the camera house to communicate the operational status of the unit to the operator. The software also had to be developed for edge recognition algorithms, communication to the system central computer over MQTT, where measure data and other important information will be send. Tests has been made to determine the function of the camera house where the first test consisted of the evaluation of the hardware of the camera house for industrial usage. The second test that was made was the evaluation of the software and a test scheme was established to mimic a real measurement on a concentrated parabolic solar collector. Even the communication with the central computer trough MQTT was tested. In the third test a measurement was done to a real concentrating parabolic solar collector to see how well the reflected edges could be detected. Also the status of the solar collector by calculating if the detected points hit the receiver pipe or not. The fourth and final test that was made was to validate the method by first measure a defect parabolic solar collector with a laser to where the laser hit and missed the receiver pipe and then measure the same solar collector with the system ARGQOS and compare the results. The tests show that the camera houses have the intended function for industrial usage and that the program is working well and is stable with only a few minor bugs. Measurements on parabolic solar collectors can be done repeatedly without any problems. The cameras could detect the reflected edges on almost the whole trough with only a few problem areas. It also displayed that the measurement was sensitive to outer disturbances that was reflected in the trough and the system was sensitive to the ambient light. In the validation test the comparison between the measurement between the system and the laser displayed the same result. More tests need to be performed to be sure that the validation holds.

  • 321.
    Vidar, Caroline
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Värmeåtervinning på förskolan Rymdattacken 1: En jämförelse av värmeväxlare2014Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In the spring of 2014 Sweco Systems AB were commissioned to design a ventilation system for a newly built preschool in Linköping. Terms from the client was that it cost efficiency would cope with the energy demands that are placed on the building. The unit chosen was a cross-flow heat exchanger, and this work is to compare it with two other heat exchangers to see if a more energy and cost efficient could have been chosen. The heat exchangers that was chosen for the comparison was a rotating- and a counterflow heat exchanger. Simulations have been made to the different heat exchangers by the manufacturers. The values from the simulations are then used to make calculations of the heat exchangers use of energy in Joulin. Even a comparison of temperature efficiencies have been made to see how well the heat recycler is working.

    To get an economic aspect, the calculation of LCC have been made.

    This work was in addition to the comparison even to find out about the values that came from the simulations to the original unit consists. It turned out that the temperature efficiency shown in these simulations was calculated at a different temperature than the other heat exchangers so it showed a higher percentage than if it had been shown for the same temperature as the other units showed in their simulation. Thus, a calculation of the temperature efficiency for the same temperature in order to make a fair comparison.

    After studying the different values it was concluded that a rotating heat exchanger should have been chosen instead of the original cross-flow heat exchanger.

  • 322.
    Viil, Stig
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Utvärdering av energiprestanda: Granskning av verkligt utförande i byggnad 14D Hjältarnas hus2019Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    På uppdrag av Region Västerbotten har författaren analyserat och utvärderat energiprestandan i Hjältarnas Hus, byggnad 14D i Umeå. Byggnaden är ett anhörighus på den västra sidan av sjukhusområdet som består av 4 våningsplan med 1658 m2, varav 390 m2 består av en ombyggnad av en portvaktarbostad och 1268 m2 av en tillbyggnad med en förbindelse som kallas för ”länken”. Utvärderingen baseras på mätningar under år 2018 som erhölls från webbplattformen DeDU och som sedan jämförs med byggnadens beräknade energianvändning från WSP.

     

    Byggnadens beräknade energiprestanda från WSP uppgick till 47 kWh/m2, värmeanvändningen för ombyggnaden 75 kWh/m2 och tillbyggnaden 42 kWh/m2. Den verkliga energiprestandan som utföraren beräknade fram uppgick för byggnaden till 60 kWh/m2, där ombyggnadens värmeanvändning blev 113 kWh/m2 och tillbyggnaden 57 kWh/m2.

     

    Den verkliga energiprestandan överstiger den projekterade med 28 %. Avvikelserna orsakas av flera faktorer. Dels att systemet opererar ihop på ett annat sätt än vad som var projekterat och att indata för energibalansberäkningen i relationshandlingen skiljer sig från det verkliga indata som författaren har beräknat. Utöver det är en potentiell orsak till avvikelserna deviationer från fackmannamässigt utförda installationer.

  • 323.
    Viil, Stig
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Utvärdering av energiprestanda: Granskning av verkligt utförande i byggnad 14D Hjältarnas hus2019Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    På uppdrag av Region Västerbotten har författaren analyserat och utvärderat energiprestandan i Hjältarnas Hus, byggnad 14D i Umeå. Byggnaden är ett anhörighus på den västra sidan av sjukhusområdet som består av 4 våningsplan med 1658 m2, varav 390 m2 består av en ombyggnad av en portvaktarbostad och 1268 m2 av en tillbyggnad med en förbindelse som kallas för ”länken”. Utvärderingen baseras på mätningar under år 2018 som erhölls från webbplattformen DeDU och som sedan jämförs med byggnadens beräknade energianvändning från WSP.

     

    Byggnadens beräknade energiprestanda från WSP uppgick till 47 kWh/m2, värmeanvändningen för ombyggnaden 75 kWh/m2 och tillbyggnaden 42 kWh/m2. Den verkliga energiprestandan som utföraren beräknade fram uppgick för byggnaden till 60 kWh/m2, där ombyggnadens värmeanvändning blev 113 kWh/m2 och tillbyggnaden 57 kWh/m2.

     

    Den verkliga energiprestandan överstiger den projekterade med 28 %. Avvikelserna orsakas av flera faktorer. Dels att systemet opererar ihop på ett annat sätt än vad som var projekterat och att indata för energibalansberäkningen i relationshandlingen skiljer sig från det verkliga indata som författaren har beräknat. Utöver det är en potentiell orsak till avvikelserna deviationer från fackmannamässigt utförda installationer.

  • 324.
    Vikström, Jimmy
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Teknisk och ekonomisk optimering av ett sekundärt kylsystem: KB01-Systemet, akademiska sjukhuset i Uppsala2018Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The University hospital in Uppsala is in an expanding phase with renovation of existing buildings, new building projects and a more sophisticated healthcare. Therefor the cooling demand is rising as the hospital is expanding. In 2011 Region Uppsala started a collaboration with Sweco to see how the rising cooling demand could be guaranteed in an efficient way, with a time perspective to 2060. The collaboration resulted in a proposal of a big secondary cooling system, with only one connection point to the district cooling. Buildings in the hospital area will connect to the system, this is instead of a traditional system where every building is directly connected to the district cooling. The benefits with a system like this is that low quality energy can be transported between buildings in an easy way. With this system, the regional council can lower their demand of purchased energy, and instead use their internal energy better.

    Today the system is operational with two subsystems connected to it. Although one of the subsystems is not fully operational because of ongoing constructions of the building. The purpose with this master thesis was to analyze three different substations that are a part of the cooling system, the analyze should result in ways to improve the temperature in the return pipe, and the use of internal energy. To control if a big secondary system could be profitable investment vise, if a cost for reserved effect is to be implemented by the district cooling supplier, the investment comparison is with an traditional system and an economical calculation has been performed to control this.

    The result from the economical calculation showed a lower yearly cost of 160 kkr for the big secondary system in comparison with a traditional system, but a higher net present value of 3,6 Mkr.

    Evaluation of the operating data from the substations resulted in five different suggestions to improve the return temperature and use of internal energy. These suggestions are as following,

    • To improve the use of available energy on the primary side, it’s suggested to install two parallel control valves on the primary side, in accordance to Svensk Fjärrvärme recommendation about control valves in systems with an installed effect over 300 kW [1]. In connection with installing parallel control valves, the regulation of the heat exchanger should be altered so they work together, instead of independently as it is today. 
    • The regulation of the circulations pumps in R4 should be changed, from constant pressure regulation to proportional pressure regulation. This measure will have no effect on the return temperature, this is only an energy saving measurement.
    • Change the type of regulation to type-2 regulation in the subsystem for house R4. What this means is that if the temperature in the supply pipe is stable, and the temperature in the return pipe start to descend, the subsystem will go over to regulate on the return temperature instead of the supply temperature.
    • Deactivate the function for a bypass valve in R4, if the function is deactivated the return temperature could rise one degree Celsius, under the circumstances that the volume flow in the system is as it has been up to now.

    When the flow is negative on the secondary side, the regulation valve on the primary side should close, and then open again when the flow is positive. 

  • 325.
    von Essen, Oskar
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Elbesparingar för eldrifter massalinje 3: Ett examensarbete på Iggesund Bruk2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Efter lagen om energikartläggning kom i juni 2014 har det ställt högre krav på företag att ha koll på sin energikonsumtion och produktion. Därifrån utformades detta examensarbete som till en början gick ut på att identifiera och sammanställa alla drifter för massalinje 3 på Iggesunds bruk. Efter sammanställningen gjordes grova beräkningar med hjälp av uppskattad besparingspotential baserat på ventillägen hos strypreglerade drifter. De grova beräkningarna visade att frekvensdrift inte var ett alternativ som effektiviseringsåtgärd idag på de drifterna, då man ville ha en återbetalningstid på max 3 år. Därför gjordes den noggranna beräkningen med avseende av andra effektiviseringsåtgärder. Just i detta fall då omsvarvning av pumphjul för att hamna rätt på pumpkurvan. Resultatet visade att en omsvarvning av pumphjul var en åtgärd som skulle återbetala sig väldigt fort och kan vara relevant för flera av drifterna i massalinjen. Resultatet visade också att man har överdimensionerade pumpar för arbetet de utför, och således tvingas strypa bort motsvarande 80 tkr per år för endast en drift. Då många liknande drifter finns i processavsnittet. Rekommenderade jag att man skall börja med att uppdatera, de sedan tidigare gjorda förstudier för blekeriet, för att se om en ombyggnad kan vara aktuell. Då blekeriet är 47 år gammalt och en del andra åtgärder, som inte har med energi påvisades som anledning till detta. Andra energieffektiviseringsåtgärder upptäcktes också, till exempel att man hade något höga börvärden för två tryckreglerade pumpar vilket också är något som återbetalar sig väldigt fort.

  • 326.
    von Sydow, Tyra
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Rådvilla - A comparative study on energy saving measures for Swedish houses from the fourties, fifties and sixties2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The awareness of the climate change and the need to reduce our energy usage is increasing worldwide. In Sweden, as in most other countries, buildings are responsible for 40% of the total energy usage. Reducing the energy usage in this sector has therefore a great potential for saving energy.

    The aim of this bachelor thesis has been to investigate and compare several energy efficiency measures on houses from the fourties, fifties and sixties. The measures have been compared from an economic, environmental and energy saving point of view with the help of simulations using the softwave IDA ICE. The energy saving measures have been put together into three energy saving packages, each with an increasing difficulty and corresponding potential for saving energy.

    A model of each house has been built up in IDA ICE, based on original drawings. The input parameters needed which could not be taken from the drawings or building construc- tion descriptions have mostly been taken from Svebys brukarindata för energiberäkningar and Energimyndighetens energistatistik för småhus 2010.

    A simple economic calculation has also been done for every energy saving package on each of the three houses. The results from the simulations clearly shows that a great amount of energy can be saved without neither a large investment cost nor a great effort. The smallest package of the project has a cost of around 15 000 SEK and saves approxi- mately 5 000 kWh every year. The medium package has a total investment cost of 100 000 SEK and an annual saving of around 8 000 kWh. Finally the largest package of the project will cost about 300 000 SEK and annualy save from 12 500 kWh to 15 500 kWh additionally.

  • 327.
    Väppling, André
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Energieffektivisering av Ringen 14: Ekonomiskt hållbara och energibesparande åtgärder för kontorslokal2013Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Denna rapport avser ett projekt som utfördes för Energitjänst i Norr AB och deras fastighet Ringen 14 på Ersboda i Umeå. Syftet var att hitta eventuella energibesparande åtgärder för fastigheten. Detta med betoning på sådana åtgärder som kunde tänkas vara ekonomiskt lönsamma, helst även på kort sikt. Ett antal scenarier undersöktes och dess energi- och ekonomibesparingar kartlagdes. Dessa gällde att optimera ventilationsflödet för fastigheten, att tidsstyra det så att ventilationen var avstängd nattetid, sänka inomhustemperaturen samt installera s.k. markförvärmning av uteluften. Sedan undersöktes även ett antal scenarier där kombinationer av dessa åtgärder applicerades. Innan slutsatser kunde dras om eventuell omfattning på dessa åtgärder så undersöktes fastigheten närmare genom mätningar av diverse storheter. Detta gällde dels mått och dimensioner på byggnaden, men även fysiska storheter som temperaturer och ventilationsflöden. Begreppet markförvärmning undersöktes även närmare. Markförvärmning är ett system där uteluften leds genom en kanal nedgrävd under mark innan den når byggnadens luftbehandlingsaggregat. Genom denna kanal kan luften förvärmas eller förkylas beroende på årstid och behov, och således gör marken en del av jobbet som annars kanske skulle krävas av värme- eller kylbatterier i ventilationssystemet. Platsspecifika förutsättningar för en sådan lösning undersöktes, och det bedömdes att en sådan lösning var möjlig för den aktuella platsen. En 3D-modell av byggnaden skapades i programvara Revit Architecture. De olika lösningarna simulerades i programvaror Revit MEP och Ida Ice 4.5.1. Beräkningarna gällande markförvärmning och dess fördelar räknades även manuellt. Resultatet efter mätningar och beräkningar visade på att ventilationen som den ser ut idag är väl fungerande och tillräcklig, men att det fanns utrymme för en minskning av volymsflödet på 25 %, vilket skulle ge en ekonomisk besparing på ca 4700 SEK/år. Den relativt höga inomhustemperaturen på 22 °C skulle vid sänkning till 20 °C ge en årlig besparing på 6800 SEK. Vid tidsstyrning av ventilationen så att den är avstängd halva dygnet gav besparingen 8800 SEK/år. Markförvärmning gav en icke försumbar sänkning av uppvärmningsbehovet, men visade sig ha en återbetalningstid på strax över 10 år. I slutändan framstod markförvärmning som ett allt för dyrt alternativ, vilket innebar att denna lösning inte rekommenderades. Däremot ansågs sänkning och avstängning nattetid av ventilationsflödet som goda lösningar. Lägre inomhustemperatur rekommenderades även, utifall att dagens klimat upplevs som övertempererat.

  • 328.
    W Flodén, Emma
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Värmeåtervinning: Energieffektivisering av varmhållningssystem för flygplan.2018Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Parked airplanes are kept warm with preheated air distributed to the plane through PCA-units (Preconditioned Air). As this air is vented directly to the outside after passing through the plane it brings approximately 70% of the input power with it. With the purpose to further improve the energy efficiency of the system Smart Climate Scandinavian AB has developed, this project examines the possibilities to recycle part of this power by returning air to the PCA-unit.

     

    The duct leading the recycled air back to the PCA should have an insolation with a thickness of at least 14mm to prevent energy loss. Calculations show that it is possible to reduce the power requirement in the PCA´s heater with 20 or 40% when 1/3 resp. 2/3 of the total airflow is recycled. The possible amount of return air is determined by the outside temperature and the fact that part of the air in most cases must pass through other vents that are not connected to recycling.

     

    During flight moisture from the passengers accumulates in the plane. It is not known in what form or where this moisture is and therefore also not in which pace it evaporates to the air. It is however desired that the moisture is dried from the plane. With the airflow the PCA can provide the relative humidity of the cabin air can be lowered from 60% to 40% in 45 minutes. This also applies if 1/3, 2/3 of the total airflow is recycled or even with a moisture addition of 1g/s. The moisture is not considered a limitation since no demands on drying are made. With a hygrometer placed in the cabin there is a possibility of 100% recycling when the desired relative humidity of the air is met and there is no risk of freezing.

    The full text will be freely available from 2023-06-20 13:58
  • 329. Wagner, Katharina
    et al.
    Häggström, Gustav
    Skoglund, Nils
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Bioenergy 2020+ GmbH, Vienna, Austria; Institute of Chemical, Environmental & Bioscience Engineering, Technische Universität Wien, Vienna, Austria.
    Priscak, Juraj
    Kuba, Matthias
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Bioenergy 2020+ GmbH, Vienna, Austria; Institute of Chemical, Environmental & Bioscience Engineering, Technische Universität Wien, Vienna, Austria; Energy Engineering, Division of Energy Science, Luleå University of Technology, Luleå, Sweden.
    Öhman, Marcus
    Hofbauer, Hermann
    Layer formation mechanism of K-feldspar in bubbling fluidized bed combustion of phosphorus-lean and phosphorus-rich residual biomass2019In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 248, p. 545-554Article in journal (Refereed)
    Abstract [en]

    The use of phosphorus-rich fuels in fluidized bed combustion is one probable way to support both heat and power production and phosphorus recovery. Ash is accumulated in the bed during combustion and interacts with the bed material to form layers and/or agglomerates, possibly removing phosphorus from the bed ash fraction. To further deepen the knowledge about the difference in the mechanisms behind the ash chemistry of phosphorus -lean and phosphorus-rich fuels, experiments in a 5 kW bench-scale-fluidized bed test-rig with K-feldspar as the bed material were conducted with bark, wheat straw, chicken manure, and chicken manure admixtures to bark and straw. Bed material samples were collected and studied for layer formation and agglomeration phenomena by scanning electron microscopy combined with energy dispersive X-ray spectrometry. The admixture of phosphorus-rich chicken manure to bark changed the layer formation mechanism, shifting the chemistry to the formation of phosphates rather than silicates. The admixture of chicken manure to straw reduced the ash melting and agglomeration risk, making it possible to increase the time until defluidization of the fluidized bed occurred. The results also highlight that an increased ash content does not necessarily lead to more ash melting related problems if the ash melting temperature is high enough.

  • 330.
    Wagner, Katharina
    et al.
    Bioenergy 2020+ GmbH, Austria.
    Kuba, Matthias
    Bioenergy 2020+ GmbH, Austria.
    Häggström, Gustav
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Skoglund, Nils
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Hofbauer, Hermann
    Technische Universität Wien, Institute of Chemical Engineering.
    Influence of Phosphorus on the Layer Formation on K-feldspar during Fluidized Bed Combustion and Gasification2018In: European Biomass Conference and Exhibition Proceedings, ETA-Florence Renewable Energies , 2018, p. 486-492Conference paper (Refereed)
    Abstract [en]

    Today, mainly wood-based feedstocks are used in thermo-chemical biomass conversion since they have a comparably high heating value and contain a small amount of ash. Fluidized beds allow a greater variety of fuels to be used, since they are rather flexible regarding their fuel input. The use of biogenic waste streams (chicken manure, horse manure, etc.) and sewage sludge would not only increase the fuel diversity in fluidized beds but might also enhance the usability of side products. The contained essential nutrients like phosphorus, potassium, calcium, etc. in these fuels are enriched in the ash after thermochemical conversion. Thus, in the near future it may be possible to apply this ash as secondary resource for fertilizer. Especially the recovery of phosphorus is of importance due to the imminent phosphorus scarcity. Due to its tendency to react with ash forming elements in fuels, phosphorus influences the ash chemistry severely. Especially the agglomeration and layer formation on bed materials during biomass combustion and gasification is highly dependent on the predominant ash forming elements. Phosphorus therefore has a significant impact on those mechanisms. Until now, the behavior of phosphorus-rich fuels in fluidized beds has not been studied in much detail. To develop a basic understanding of the behavior, phosphorus-rich feedstock was combusted in a bench-scale fluidized bed reactor. Ash layers on bed particles, which were formed during these experiments, were studied and compared to results with phosphorus-lean fuels. Furthermore, layer formation of phosphorus-rich and phosphorus-lean fuels from dual fluid bed gasification were compared to those from fluidized bed combustion. The studied layers on bed materials showed significant amounts of phosphorus. The data also indicates a change in layer formation as soon as phosphorus is present. An increased catalytic activity due ash-layer formation was observed for both phosphorus-rich and phosphorus-lean feedstock, independent from the presence of phosphorus in the ash layer.

  • 331.
    Wahlén, Sofia
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Bergkyla och bergvärmeutredning för industrilokalen Rödbergsmyran 5 i Umeå, Västerbotten.2014Independent thesis Basic level (university diploma), 180 HE creditsStudent thesis
    Abstract [en]

    Grubbe Ventilation AB is a sheet metal and ventilation company who provides design, installation, service, and repair of ventilation. The company is expanding their business by building a new facility in Umeå, Västerbotten. The property is designed to be used for both office and industrial work.

    Grubbe Ventelation AB has not yet decided upon wish system which is to be established to provide the building with heating and cooling. The consulting firm Umeå Projekt Team has therefore been asked to investigate the possibilities to invest in geothermal- heating and cooling.

    If the investigation of a geothermal heating- and cooling system would provide favorable results it would be a very appropriate alternative that provides energy at low costs and are an environmentally friendly option as the energy comes from stored solar energy in the ground is provided by stored solar energy in the ground.

    The facility ´s heating and cooling consumptions are calculated in the program BV2 and the result indicate a heating demand of 185 000 kWh per year due to thermal transmittance, transmission losses, heating of warm water and a cooling requirement of 5500 kWh.

    Three different systems of geothermal heating and cooling were tested in the computer program Energy Earth Design. The results show no difference in the dimensioning of the drill hole if merely heating were to be used or both heating and cooling were to be established. The only alteration in the investment is therefore the additional cost of the cooling machine.

    The geothermal heat pump is designed to cover 60-70 percent of the maximum heat demand of the facility. The additional 30-40 percent will be covered by additional heating. A geothermal heat pump of 40 kW who require a 30 kW electrical heater to cover additional heating would be appropriate for this project.

    An investment of geothermal heating and cooling would require five bore holes of 210 meters wish provide an investment cost of 307 050 sek for the boreholes and an total investment of 446050 sek with a pay-off time of 5,6 years without cooling and 471050 sek with cooling wish give a pay-off time of 5,9 years.

    If a special double U-piping were to be used only four boreholes would be required of 250 meters. That would give a total investment cost of 459240 sek and a pay-off time of 5,8 years.

  • 332.
    Wallin, Erik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Utvärdering av laststyrning av fjärrvärme hos Umeå Energi AB2011Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    During spring of 2011 Umeå Energi AB (UEAB) took the initiative to test and implement load control of district heating to see the effects it has on their system. The system has been tested on Bostaden Umeå AB’s (BUAB) apartment complex on Liljansberget in Umeå. The area includes 709 apartments of various sizes and construction started in 2005 and was completed in 2008. The system periodically reduces the input power to obtain a reduction in supplied energy through the district heating central. Since UEAB in winter depend on peak load in the form of oil and electric boilers this thesis has also evaluated the possibility to gain a reduction in peak power.

    Noda Intelligent Systems (Noda IS) has developed the system for load management and has promised a minimum performance which the system has to deliver. A reduction in energy of 5 %, which is in interest of BUAB since they want to reduce their energy consumption. Also a peak power reduction of 10 % which UEAB wants to evaluate in order to reduce its dependence on fossil fuels. A reduction of peak power offers the possibility for a more balanced production and a better use of the system’s major production facilities.

    During the project, various control schemes was developed and tested to see how the system would reacts to load management. During the period from January to mid-March the system had problems when losing contact with the internet and the system was unable to establish contact. On one occasion, the implemented safety devices from Noda IS failed to start. Which meant that the system stoped supplying heat to the buildings. Because of this the indoor temperature droped below the recommended level of 180C.

    The expected energy savings for the area with normal-correction is 2,9%. No energy-saving effect can be seen in the largest of the three district centers in the area. The reason for this is believed to be due to the small amount of reading available for the used method. The system shows promising results in power reduction, where two times a day, except at +100C it obtains a mean power reduction of 10% over four hours. Power reduction is derived theoretically without inclusion of the recession in energy. Which has been noted after the system has managed a reduction in supplied power.

    The system that has been installed on Liljansberget receive a payback of 1,8 years. This is possible due to a decreased use of fossil fuels. Peak load and the duration is taken from UEAB under 2010. The assumption that a power reduction from the area directly lead to a reduction in peak load during the hours they are active is made.

  • 333.
    Wallin, Michaela
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Utredning kring verkningsgrad och driftparametrar hos en biobränsleeldad rosterpanna: Panna 6 Ålidhems värmeverk2017Independent thesis Advanced level (professional degree), 300 HE creditsStudent thesis
    Abstract [en]

    Boiler 6 is one of Umeå Energy's heating boilers that are placed at Ålidhem's heat plant and it is used for top heat production during the winter season. It is a grate fired biomass boiler with an installed effect of 32 MW and it is fed with fine wood chips. During the past few years, the boiler have had problems with some of the parameters that does not work the way they should. For example, the content of carbon monoxide (CO) in the flue gases are extreamly high at sometimes and it is a high amount of unburnt organic material in the the ash. Since the boiler is not continuously in use, it is difficult to identify the reason to this unwanted conditions. The efficiency of the boiler is calculated with the input-output method every month, but a more thorough determination is demanded from Umeå Energy. Therefore, the efficiency has been calculated with the heat loss method in this work together with an investigation of the non-optimal parameters.

    Samples from three different times when the conditions of the boiler was different was taken and sent of for analysis. Samples from the fuel and the ashes were taken and the surface temperature and wind flow close to the boiler was determined. After the sampling and calculation was done, the investigation of the parameters started and some help could be taken from the efficiency determination.

    The result showed that the efficiency is high, between 92-93 % depending on the conditions. The investigation showed that it is possible to save up to 55 000 SEK per year by reduce the amount of unburnt material in the ash with 85 %. It also showed a relation between the high amount of CO in the flus gases and the heat output of the boiler. When the boiler is on maximal operation, the fuel is most likely not fully combusted. That is therefore the reason for the high amount of CO when the boiler is at its maximal operation. The result also showed that the secondary air supply does not have any relation to the CO amount, which it was assumed to have in the first place.

    The conclusion of the work is that the boiler works well overall, but there are some improvments of the parameters that could be done and further investigated. It is recommended to further look at the relation between the CO and heat output to determine its occurrence and aslso determine the new maximum heat output for the boiler to work in a more stable and environmental way.

  • 334.
    Wannemo, John
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Zero CO2 factory: Energikartläggning av industrier och ett exempel på hur noll utsläpp nås2019Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The industry sector accounts for 32% of the global energy usage where the majority of the energy is being used as heat. Most of the heat is generated by burning fossil fuels which leads to heat use being the largest source of emissions in the sector. About half of energy used as in the industries are in temperatures up to 400 °C which is suitable for heat provided by solar collectors.The apparel industry accounts for 10% of the global carbon emissions and multiple of the industry processes used in textile production are in temperature ranges reachable with solar collectors such as Absolicons T160.Energy data was collected from textile factories and calculations of energy usage and emissions was made. The calculations for solar collectors was made with Absolicons web application Field Simulator. A 3-step plan was created to demonstrate how two textile factories in India could reach zero CO2 emissions.The analysis shows that the textile industry’s majority of energy is being used from fossil fuels to generate heat where the 5 largest factories in this report average energy is 85% as heat and 15% as electricity. The emissions per produced mass of goods in kg is an average of 6,1 kgCO2e at these 5 factories which is comparable to burning 2,1 kg of black coal.The two large textile factories combined emissions from energy usage is reported to be 686 ktCO2e. In the 3-step plan the heat usage is reduced by 17% and heat from fossil fuels are replaced by heat from solar collectors and biomass. To cover 68% of the new energy demand it would require solar fields with a total thermal capacity of about 400 MW and an area of 1,3 km2. The remaining 32% of heat demand would be covered by burning 100 000 tonne of biomass per year.The conclusion is that he industry sector has a huge potential of reducing their emissions by replacing fossil fuels for generating thermal energy by thermal energy from e.g. solar collectors or biomass. It will require available spaces close to or on top of the factories to be able cover large portions of the heat demand with solar collectors. The current prices of energy from fossil fuels is low compared to their emissions and a global carbon market or taxes should be applied to accelerate the change to clean energy and lower emissions.

  • 335.
    Wansulin, Linnéa
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Vindkraftens utvecklingsmöjligheter: En studie om samverkan och tekniksprång2018Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The aim with this study has been to achieve an enhanced cooperation within the wind power corporate and to examine the situation for leapfrogging innovations. The existing cooperation between different areas of expertise has been analysed to be able to identify flaws and make an improvement. An investigation has been conducted to examine the possibility of an improved cooperation by making it more comprehensive. To achieve a greater interaction has a suggested joint program been developed. This study also contains an evaluation about new innovations. The focus is on how to proceed in new technological leaps and how the industry should work to promote wind power growth. A flow chart has been developed making it easier to weed out substandard technologies and take advantage of the hidden gems. These two areas have a mutual red thread which is how it’s supposed to assimilate in future research. The project charts and analyses the following areas:

    ➢ Development requirements within existing cooperation.

    ➢ Possible new and innovative concepts, with focus on leapfrogging.

    The report mainly consists of an empirical study in which interviews were made with relevant and knowledgeable people within the business. Interviews have been compiled and formed the basis of the project results. The study shows that today's cooperation between different wind research areas is faulty. As a result, the wind turbine's optimal potential is not achieved. The problem origins in politics and how Sweden initially choose to invest in wind energy. Since then, more problems have occurred such as lack of communication and financial difficulties.

  • 336.
    Wells, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Determining the voltage range of a carbon-based supercapacitor2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The focus of this thesis has been to determine the usable voltage range of carbon-based supercapacitors (SC). Supercapacitors are a relatively new type of capacitors with a vast increase in capacitance compared to capacitors which utilize a dielectric as charge separator. A SC consists of two electrodes and an electrolyte separating the electrodes. The charges are stored by electrostatic forces in the interface between the electrode and the electrolyte, forming the so called electrochemical double-layer (EDL). With porous electrodes the effective surface area of the interfacial zone can be made very large, giving SCs a large storage capacity. The limiting factors of a SC is the decomposition potential of the electrolyte and the decomposition of the electrodes. For commercially manufactured SCs the electrolyte is usually an organic solvent, which has a decomposition potential of up to 2.7-2.8 V. Compared to aqueous electrolytes with a thermodynamic limit of 1.23 V. The drawback of using non-aqueous electrolytes is that they are not environmentally friendly, and they increase the production cost. It is claimed that the voltage range can be up to 1.9 V using aqueous electrolytes. Some researchers have focused on aqueous electrolytes for these reasons. In this thesis two different electrolytes were tested to determine if the voltage range could be extended. The experiments were conducted using a three electrode cell and performing cyclic voltammogram measurements (CV). The carbon electrodes were made of  two different sources of grahite, battery graphite or exfoliated graphite, and nano fibrilated cellulose was added to increase the mechanical stability. The results show that the oxidation potential of the carbon electrode was the positive limit. A usable potential of about 1 V was shown. However, when cycling the electrodes to potentials below the decomposition limit, for hydrogen evolution, interesting effects were seen. A decrease in reaction kinetics, indicating a type of conditioning of the electrode was observed. An increase in charge storage capacitance was also observed when comparing the initial measurements with the final, probably corresponding to an increase in porosity.

  • 337.
    Wennebro, Jonas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Produktion av Pyrolysolja från kvistrejekt2012Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Fast pyrolysis is a method for converting biomass into three energy rich products: char, gas and bio-oil, where the latter is most interesting.  Pyrolysis is an endothermic process where biomass is heated in an anaerobic environment and, with the right operating conditions, up to 80 %wt bio-oil can be extracted. Key parameters for fast pyrolysis are: stable reactor temperature (~500°C), short residue time for gas in the reactor (<2 s) and a very high heating rate for the biomass. Today there are several different process solutions for fast pyrolysis, where fluidized beds and rotating cones are most developed. Bio-oil has compared to fossil oil: lower heating value, low pH and also polymerizes with time. Because of this upgrading is desirable for increasing competitiveness. Several large projects for producing of bio-oil are at the moment developed around the world. Though often is subsidy money involved in these projects. 

    Domsjö Fabriker AB in Örnsköldsvik, who is converting softwood into special cellulose, bio-ethanol and lignin, are interested in pyrolysis technology. They are using the unique sulphide process; and during the pulping of the biomass a residue in form of knots are extracted from the process. This waste product is of little value and the company is interested in investigating the possibility to produces bio-oil from these knots. The knots have several characteristics that differ from normal biomass, such as high amount of ash and extractives. High ash content leads to secondary reactions in the reactor, which leads to lower yields of bio-oil. Because of this the knots are not an optimum raw material for fast pyrolysis. At the same time high amount of extractives in the biomass might result in a to two phase liquid product. To ensure how well the knots will behave during pyrolysis testing is needed. The relatively low reject flow (18 tons/day) will, in relative terms, lead to high investment costs and a larger facility (120+ tons/day) is preferred in order to keep production costs low. Considering this, plus an uncertainty regarding the knots as a raw material for pyrolysis, bio-oil as a fuel and fast pyrolysis competitiveness, a recommendation for investing in a pyrolysis plant at Domsjö will not be recommended without first experimentally examining this untested biomass in combination with fast pyrolysis technology. 

  • 338.
    Wennerström, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Energieffektivisering av Fröklängen 12011Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 339.
    Westergren, Erik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Heat Flux Measurement using Infrared Thermography: The development and validation of a novel measurement method2017Independent thesis Advanced level (degree of Master (Two Years)), 300 HE creditsStudent thesis
  • 340.
    Wiglöv, Elin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Energioptimering med laststyrning av fjärrvärme på Sandåkern2012Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    District heating is an efficient way to supply buildings and larger housing areas with heat and due to new technologies further optimizations can be done in the heating distribution and use between different building and housing areas. This is called Load Control.

    At times of high loads of energy use, there is a possibility to displace a part of that load to later point in time and in such a way eliminate load peaks. This way peak load production can be restricted to lower levels or, preferably, avoided completely.

    The aim of this study was to investigate what possible effects Load Control of district heating could have on a new housing district currently under construction called Sandåkern in Umeå. The study focused on the effects of Load control in terms of energy usage, environmental impact and also how the use of heating oil in the production of the district heat might be influenced.

    A reference project, that has used Load Control of district heating since the beginning of 2011, is used for estimating possible effects of Load Control at Sandåkern. All statistics, like energy usage and temperatures, comes from the reference project. Excel and the built in support for Visual Basic has been used for all calculations.

    The results show that, for the model house Sandåkern Hus 2, an estimated saving in energy usage of 7,7 MWh could be achieved during a common year. Scaled to be equivalent to a number of normal sized districts the savings range from 152 MWh to 610 MWh depending on the assumed sizes.

    The use of heating oil could be diminished with 2,6 MWh for the single model house during one common year and this value varies in the range of 51 MWh to 206 MWh for the different sizes of made up districts.

    The real effects of Load Control of district heating for Sandåkern will be available when construction work has been completed and statistics measured for the whole housing area can be analyzed.

  • 341.
    Wänglund, Josefin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Undersökning av SNCR som rökgasreningsmetod för att reducera utsläpp av NOx: En utredning gjord på SCA Östrands massafabrik2017Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    På SCA Östrands massafabrik i Timrå produceras två olika typer av pappersmassa,blekt sulfatmassa och kemitermomekanisk massa (CTMP). Idag produceras ungefär 430 000 ton blekt sulfatmassa och 95 000 ton CTMP per år. Just nu pågåren om- och nybyggnation av sulfatmassalinjen inom projektet Helios. Målet med projektet är att under 2018 ta i drift en fabrik med en kapacitet att producera 900 000 ton blekt sulfatmassa per år. I och med utbyggnaden har fabriken fått en ny miljödom (som ett resultat av verksamhetstillståndsansökan) med villkor attförhålla sig till. I miljödomen presenteras ett antal olika villkor; utredningsvillkor, utsläppsvillkor och riktvärden. Ett av villkoren är ett utredningsvillkor som gäller utredning av rökgasreningstekniken SNCR (selektiv icke-katalytisk reduktion) för att rena rökgaserna från fabrikens ångproducerande enheter, barkpannan (ÅP1)och sodapannan (SP6), från NOx. Syftet med examensarbetet var att i ett första steg i utredningen av utredningsvillkoret undersöka möjligheterna till att använda SNCR som rökgasrening på ÅP1 för att rena rökgaserna från NOx.

    För att utreda möjligheterna att använda SNCR på ÅP1 gjordes temperaturmätningar av rökgaserna i pannans övre del och en temperaturprofil över pannan bestämdes. Vidare undersöktes olika metoder av SNCR och andra sekundära rökgasreningsmetoder i en litteraturstudie och i en undersökning av marknaden som bland annat innehöll referensbesök på anläggningar med olika SNCR-system.En grov kostnadsmässig analys genomfördes också genom att beräkna teoretiskautsläppsmängder för de nya förutsättningarna efter Helios, NOx-avgiften och kemikalieförbrukningen i ett hypotetiskt fall där SNCR installeras.

    Under de förutsättningar som temperaturmätningarna gjordes framkom det att det inte är möjligt att använda sig av SNCR för att reducera NOx-utsläppen från ÅP1. Mätningarna visade dock att det är möjligt att använda SNCR som reningsmetod vid laster högre än 72 ton ånga/h om det finns ett linjärt samband mellan last(ton ånga/h) och rökgastemperaturen.

  • 342. Zhu, Youjian
    et al.
    van Eyk, Philip J.
    Boman, Christoffer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Kirtania, Kawnish
    Piotrowska, Patrycja
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    de Nys, Rocky
    Bhattacharya, Sankar
    Gentili, Francesco G.
    Ashman, Peter J.
    Preliminary understanding on the ash behavior of algae during co-gasification in an entrained flow reactor2018In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 175, p. 26-34Article in journal (Refereed)
    Abstract [en]

    Algae are considered as a promising alternative fuel to produce energy due to its advantages such as high production yield, short growth cycle and flexible growing environment. Unfortunately, ash-related issues restrict its thermochemical utilization due to the high ash content and especially the high alkali metal concentration. In this paper, the gasification performance and ash behavior were experimentally analysed for three macro- and micro-algal species. Clear differences in the proximate and ultimate compositions were found between the cultivated algae used in this study and macroalgae (seaweed) harvested from the marine environments. Algal biomass generally contained higher Na and P contents than lignocellulosic biomass. Microalgae also had a relatively high mineral content due to the impurities in the harvesting process which included centrifugal pumping followed by sedimentation. Co-gasification of 20 wt% algae with softwood was investigated using an entrained flow reactor. The addition of both macroalgal species Derbersia tenuissima and Oedogonium to softwood had a limited influence on the gas yields and carbon conversion. On the other hand, the addition of the microalgal species Scenedesmus significantly decreased the main gas yields and carbon conversion. Moreover, the addition of algae clearly changed the residual ash composition of the base fuel. Finally, a preliminary understanding of the ash behavior of the tested algae blends was obtained through the analysis of the fuel ashes and the collected residual ashes. Fouling and corrosion were presumably occurred during the co-gasification of wood/macroalgae blends in view of the high alkali metal content. Microalga Scenedesmus had a high mineral content which could potentially capture the alkali metal in the ash and mitigate fouling when gasified with softwood. The growing environment and harvesting method were found to be significantly affecting the ash behavior implying the need for careful consideration regarding co-gasification process.

  • 343.
    Zäll, Christian
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Uppvärmning av fastigheter utanför fjärrvärmenätet: En jämförande studie av olika alternativ till el och olja2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Uppsalahem AB has set up a goal to phase out all heating that is done by electric or oil-fueled boilers. In this work it has been investigated how Uppsalahem could expect their operating costs and environmental impact to change if these boilers are converted to other alternatives that is available on the market today. The alternatives that have been evaluated are pellet boilers and heat pumps and these two alternatives in combination with solar heating. So called “Färdig värme” (translates to “Ready heating”), a sort of small scale pellet based district heating, has also been evaluated.

    In this work numbers are presented for environmental impact expected for the different alternatives. The results indicate that it would be possible to cut the emission of green-house gases to a tenth of their current level by converting to a pellet based heating or to a third by converting to a heat pump. The operating cost and the potential for investment, based on the life cycle cost, are also presented. For the potential for investment, a sensitivity analysis has been made to investigate how it depends on future changes in the energy prices. The evaluation also gives some technical merits and demerits for the different techniques.

    The conclusion that can be drawn from the results is that it is probably a good affair, both economically and environmentally, to convert the oil and electrically heated units that still exist in the housing stock. Due to the difficulty to foretell the future energy prices there is still a large uncertainty in judging what alternative is the most profitable one. New heating techniques can therefore be selected based on what suits the organization best, or to achieve the greatest possible environmental benefit.

  • 344.
    Åberg, Robin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Energikartläggning och utredning av klimatpåverkande kylanläggning: Ett examensarbete för ökad energieffektivitet och reducerad klimatpåverkan på en glassgrossist2017Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The report presents the results of the energy mapping and the investigation of the cooling system performed at the ice cream wholesaler GB Glass in Umeå. An overall study of the entire operation with all technical systems has been performed. GB glass aims to reduce its climate impact caused by energy consumption in the property as well as leakage of refrigerant from the cooling system and vehicle refrigeration equipment. Except fuel for trucks the wholesaler only consumes electricity. The following energy aspects have been identified as significant for the business:

     

    Total energy use                                       394 MWh

    Cooling system plant                                258 MWh      (65% of total total energy use)

    Refrigeration trucks                                 75   MWh      (19% of total total energy use)

    The cooling system plant constitutes a major part of the wholesaler's total energy use and must be rectified due to a decision by the EU's F-Gas Regulation by 2020 when a service and maintenance prohibition carries out for the existing refrigerant.

    The investigation concerns how to best accommodate this prohibition, convert and replace the refrigerant for continued operation of the existing plant or invest in a new climate-neutral type. After inspection of the cooling system and completed study of cooling systems and refrigerants, it is recommended to invest in a new climate-neutral transcritical carbon dioxide plant. A price estimate has been made and has been estimated to cost between 1.3 - 1.5 million.

     Transmission (thermal loss through climate scale) and infiltration (involuntary ventilation) accounts for 50% of the total energy delivered. Ceded heat energy by the cooling plants condenser fans on the roof accounts for 18% and the truck's cooling units 19%. Proposals for efficiency enhancements developed after the energy survey are as follows: 

    • Install an air curtain to reduce infiltration flows in the doorway between freezing and storage
    • Install timer-controlled engine heaters on the yard
    • Add a new ventilation unit with rotary heat exchanger
    • Seal around the emergency exit on the freezer

    Performing all efficiency measures is estimated to reduce energy consumption by 42 MWh, which represents 11% of the wholesaler's total energy supply. In connection with the installation of a transcritical carbon dioxide cooling system, there is a great opportunity to install the system so that the high temperature condenser heat can be used for heat recovery. The hot gas heater can preheat the supply air in the ventilation units as well as heating the tap water. This would help to further reduce the overall energy demand.

  • 345.
    Åkerström, Niklas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Ackumulatortank i PiteEnergis fjärrvärmenät2017Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 346.
    Åslund, David
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    PVT-panelernas plats i samhället: En vidareutveckling av Evertechs ETX-paneler2017Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Abstract

    To prevent that the climate influences reaches critical and irreversible levels in the near future, a change in our energy consumption and our energy sources is required. It will be a combination of multiple system solutions and several types of renewable sources, both at a personal and national levels. Every hour, the sun shines at the earth with the same amount that the world's population needs in a year. It is clearly a small part of this that we could use, but it is easy to see the potential.

    Evertech is a company in Umeå, whose strategy is to develop products to extract and recycle heat energy from the solar renewable resource. The company has several products and all are based on a heat exchange panel. Together with the company the possibility of combining a solar module with Evertech's solar panel was tested for a hybrid to get better effect on the solar cell by cooling. Hybrids are also called PVT-modules (photovoltaic thermal).

    A system setup was made with a simple prototype to measure surface temperature and power difference when the solar cell was cooled by the heat exchanger absorber. The measurement study showed an increased effect of 8 % on average and a maximum of 15 %. At the time of maximum, a surface temperature difference between the solar cell and the hybrid was determined to 20°C while the average was at 15°C. A temperature gradient at the cooled module was detected, which inhibited the power increase. This indicates that a future product would have the ability to obtain higher values. 

    By combining the solar hybrid with a geothermal heating system, one could secure both the own heat supply and the electricity supply and at the same time have the possibility of recharge the mountain. This and how the systems can benefit from each other were studied in the simulation program Polysun. The primary goal of using a hybrid system is to create as high efficiency as possible on the solar cells and to improve the SPF value of the heat pump by allowing the heat carrier to circulate through the hybrids. The difference between the SPF-value of a hybrid system in conjunction with a geothermal system was 4.2 against the geothermal system 2.7. To cover up the increased electricity consumption that the circulation meant and the heat losses against a solar collector system did not become a problem.

    The results of the simulations and the economic study show that a PVT-panel built on Evertech's ETX-panel together with geothermal heat has equally good conditions for managing as solar cells or traditional solar collectors. The repayment period for a PVT module was 13,8 years for a 20 % solvency payment. For a solar cell plant of the same size it became 14,5 years. The PVT had the best return on investment of 1,2 % and an annual gain of 2000 Swedish kronor of the compared systems.

  • 347.
    Åström, Amanda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Flerbostadshuset Vasa 2: Simulering i IDA ICE av energibesparande åtgärder2016Independent thesis Basic level (university diploma), 180 HE creditsStudent thesis
  • 348.
    Öberg, Malin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Optimerade material för optiska komponenter i koncentrerande solfångare2015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The energy consumption continues to increase as the use of electronics and energy consuming equipment increases. The use of fossil fuels has to be phased out for this to be sustainable in the long run while the use of renewable energy continues to increase. A renewable energy source is solar energy but the production of heat and electricity are today very expensive compared to other energy sources and an important task for the solar energy market to grow is therefore to minimize the production cost of the solar collectors while increasing its efficiency to produce heat and/or electricity. One way to convert solar energy into heat is by using solar collectors and electricity can be produced by utilizing the produced heat, or by applying solar cells.

    This thesis aims to recommend a reflective material for the next generation solar collectors from Absolicon and to recommend a commercially available coating for the receiver tube of the solar collector. A market study has been carried out to investigate the cost-related aspects along with the optical and durable aspects for the optical material of the solar collector. Experimental evaluations have been performed to ensure that the optical materials meet the requirements that the supplier promises. The optical properties have been evaluated with advanced measuring equipment at the Ångströmlaboratoriet at Uppsala University and with an infrared camera. The measured values from the infrared camera were in turn used to theoretically calculate the thermal losses of the receiver tubes. To investigate the materials durability the materials were subjected to different climates in a climate chamber and all the tests that has been conducted in this thesis have been carried out both before and after the climate chamber simulation to investigate the materials optical and physical durability. An important aspect of the laminated films is that they should have good adhesive properties even when subjected to high temperatures and high humidity and a method to evaluate this has been developed.

    The result of the thesis shows that aluminum reflectors obtain the best optical results for concentrated solar collectors, but since aluminum is not suitable for the Absolicon solar collector TC160 the recommended reflector material is SF2, which showed good optical, adherent and durable properties which is desirable for a good solar collector and a total reflectance of 92.4 % was obtained. The material that is recommended as a receiver tube is R2 with a measured absorptance of 95.9 %, an emissivity of 17.7 % and the thermal energy loss was calculated to 1055 W. R2 is durable in high humidity and temperatures of 85°C for over 300 hours without the optical characteristics deteriorated. Based on the recommended materials, the next generation solar collectors from Absolicon obtained a theoretical calculated optical efficiency of 76 %. 

  • 349. Öhman, M.
    et al.
    Pommer, L.
    Nordin, A.
    Bed agglomeration characteristics and mechanisms during gasification and combustion of biomass fuels2005In: Energy & Fuels, Vol. 19, no 4, p. 1742-1748Article in journal (Refereed)
    Abstract [en]

    Controlled agglomeration tests, using six representative biomass fuels (bark, Lucerne, reed canary grass, bagasse, olive flesh, and cane trash) were performed in a bench-scale fluidized bed (5 kW) during both gasification and combustion conditions. The resulting bed materials were analyzed using scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS), and chemical equilibrium calculations were performed to facilitate the interpretation of the experimental findings. Layers of fuel-ash-derived compounds were built up on the bed particles during processing of all studied fuels. The accumulated material was determined to consist of two layers: (i) an inner thicker and more homogeneous layer that consisted of mainly K-Ca-silicates and (ii) a thinner, particle-rich outer layer. For all fuels except Lucerne, no major differences in bed agglomeration tendencies or bed particle layer characteristics could be detected between gasification and combustion, which suggested no major difference in layer formation processes or bed agglomeration mechanisms between the two different operational modes. Thus, initial silicate layer formation followed by subsequent viscous flow sintering and agglomeration was identified as the bed agglomeration process in all cases except during the combustion of Lucerne. For combustion of the relatively sulfur-rich Lucerne fuel, the agglomeration was induced by a salt melt where the bed material particles were directly glued together by a separate ash-particle-derived melt.

  • 350.
    Öhman, Marcus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Hedman, H
    Jirjis, R
    Reasons for slagging during stemwood pellet combustion and some measures for prevention2004In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 27, no 6, p. 597-605Article in journal (Refereed)
    Abstract [en]

    Ash related problems have more than occasionally been observed in pellet burners during the last years. These problems lead to reduced accessibility of the appliances and also bad publicity for the pellet market. The objectives of the present work were therefore to: (i) determine the critical levels of the problematic ash components in stemwood pellets regarding slagging, (ii) document the variations of these problematic elements in the outgoing pellets from two pellet-mills during one operational season, (iii) determine how frequently these elements exceed the critical levels, (iv) determine how different sub-processes in the pelletising process (especially the dryer) effect the slagging properties of the pellet, and if possible (v) suggest some measures for prevention. A significant number of wood pellets reported to be problematic and problem-free, regarding slagging in ordinary residential pellet burners, were collected from the Swedish market. The ash compositions of these fuels were analysed and the results compiled in a database. Partial Least-Squares Discriminant Analysis (PLS-DA) and F-tests were used to statistically identify both the critical ash components and the critical levels of these components that separated the two reported classes. In addition, chemical equilibrium model calculations were used to interpret the findings. The variations of these elements in the in-going raw material and in the produced pellets were determined during one season in two pellet mills equipped with exhaust gas dryers. The results showed that the problematic wood-pellets had a significantly higher amount of Si, but also Al and Fe, in the fuel ash. The critical level of Si (given as SiO2) was about 20-25 wt% of the fuel ash, i.e. pellets with levels in or over this range resulted in slagging problems in residential burners. This critical Si content was exceeded once and twice for the analysed samples in the two studied pellet mills. In one of the studied mills, this was because of contamination by sand of the raw material during storage and handling, and in the other mill the reason was found to be contamination of the raw material by elutriated particles from the dryer fuel. The major conclusion of the work is that both raw materials and drying fuels/processes should be carefully treated to avoid mineral contamination, and an additional cyclone separator could potentially also be used to improve the pellet quality.

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