umu.sePublications
Change search
Refine search result
1234567 151 - 200 of 363
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 151.
    Kuba, Matthias
    et al.
    Technische Universität Wien, Institute of Chemical Engineering.
    He, Hanbing
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Kirnbauer, Friedrich
    Technische Universität Wien, Institute of Chemical Engineering.
    Skoglund, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Hofbauer, Hermann
    Technische Universität Wien, Institute of Chemical Engineering.
    Mechanism of Layer Formation on Olivine Bed Particles in Industrial-Scale Dual Fluid Bed Gasification of Wood2016In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, no 9, p. 7410-7418Article in journal (Refereed)
    Abstract [en]

    Utilization of biomass as feedstock in dual fluidized bed steam gasification is a promising technology for the substitution of fossil energy carriers. Experience from industrial-scale power plants showed an alteration of the olivine bed material due to interaction with biomass ash components. This change results mainly in the formation of Ca-rich layers on the bed particles. In this paper, a mechanism for layer formation is proposed and compared to the better understood mechanism for layer formation on quartz bed particles. Olivine bed material was sampled at an industrial-scale power plant before the start of operation and at predefined times after the operation had commenced. Therefore, time-dependent layer formation under industrial-scale conditions could be investigated. The proposed mechanism suggests that the interaction between wood biomass ash and olivine bed particles is based on a solid–solid substitution reaction, where Ca2+ is incorporated into the crystal structure. As a consequence, Fe2+/3+ and Mg2+ ions are expelled as oxides. This substitution results in the formation of cracks in the particle layer due to a volume expansion in the crystal structure once Ca2+ is incorporated. The results of this work are compared to relevant published results, including those related to quartz bed particles.

  • 152.
    Kuba, Matthias
    et al.
    Technische Universität Wien, Institute of Chemical Engineering.
    He, Hanbing
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Kirnbauer, Friedrich
    Technische Universität Wien, Institute of Chemical Engineering.
    Skoglund, Nils
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Hofbauer, Hermann
    Technische Universität Wien, Institute of Chemical Engineering.
    Thermal stability of bed particle layers on naturally occurring minerals from dual fluid bed gasification of woody biomass2016In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, no 10, p. 8277-8285Article in journal (Refereed)
    Abstract [en]

    The use of biomass as feedstock for gasification is a promising way of producing not only electricity and heat but also fuels for transportation and synthetic chemicals. Dual fluid bed steam gasification has proven to be suitable for this purpose. Olivine is currently the most commonly used bed material in this process due to its good agglomeration performance and its catalytic effectiveness in the reduction of biomass tars. However, as olivine contains heavy metals such as nickel and chromium, no further usage of the nutrient-rich ash is possible, and additional operational costs arise due to necessary disposal of the ash fractions. This paper investigates possible alternative bed materials and their suitability for dual fluid bed gasification systems focusing on the behavior of the naturally occurring minerals olivine, quartz, and K-feldspar in terms of agglomeration and fracturing at typical temperatures. To this end, samples of bed materials with layer formation on their particles were collected at the industrial biomass combined heat and power (CHP) plant in Senden, Germany, which uses olivine as the bed material and woody biomass as feedstock. The low cost logging residue feedstock contains mineral impurities such as quartz and K-feldspar, which become mixed into the fluidized bed during operation. Using experimental and thermochemical analysis, it was found that the layers on olivine and K-feldspar showed a significantly lower agglomeration tendency than quartz. Significant fracturing of particles or their layers could be detected for olivine and quartz, whereas K-feldspar layers were characterized by a higher stability. High catalytic activity is predicted for all three minerals once Ca-rich particle layers are fully developed. However, quartz may be less active during the buildup of the layers due to lower amounts of Ca in the initial layer formation.

  • 153.
    Kühn, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Energy efficiency and harmonics in electric power systems2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 154.
    Larsdotter, Linn
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Hur påverkar en ökad andel solceller Umeå Energis elnät?: – En utredning med fokus på spänningsvariationer och osymmetri inom landsbygds- och tätortsnät vid en- och trefasanslutning av solcellsanläggningar2014Independent thesis Advanced level (professional degree), 300 HE creditsStudent thesis
    Abstract [en]

    A good power quality can be an important prerequisite to achieve a sustainable society. Scandinavia's electrical system is in many respects superior, and Sweden has a fossil free electricity generation at 97 % and a reliability of electricity distribution at 99.98 %. Meanwhile, the EU has an ambition to expand the electricity market in order to achieve a joint trading business across Europe. This cross-border market will result in a large proportion of fossil energy sources integrated into our electrical system, which also leads to an increased need for renewable electricity production in Sweden. One part of this development is to increase the share of renewable micro generation that is locally or regionally connected to the power grid. Distributed generation can have advantages as reduced network losses, an increased energy supply and a reduction of the fossil energy use in Europe. But it has also been shown that it gets harder for the electric companies to provide their customers with electricity of good quality when the number of installations increases. An improved power quality implicates reducing events and phenomena in the power grid that affect machinery and electrical appliances negatively. This study focuses mainly on the voltage variations and unbalances that can arise when the proportion of PV-systems increases. One of the main reasons for voltage variations is the reversed power flow that migrates "upwards" in the grid when the PV-systems produce and sell their excess to the grid. The reason for unbalance in the low voltage network is mainly loads or production with uneven distribution between the three phases. An acceptable voltage variation should not exceed ± 10 % of the reference voltage and a balanced state is crossed at 2 %. This study has carried out simulations on three of Umeå Energi´s low voltage networks with different customer configurations and network structure. The grids were assigned virtual PV-systems for 25, 50, 75 or 100 % of the customers, and the phase voltages, unbalances and overloaded lines affected by the output of 1-5 kW from the connected facilities were studied. The differences in voltage at single and three phase connection and differences between customers located near and far from the substation have been investigated. Measurements have also been made on an existing PV-installation. The simulations show that the customers who are placed far out in the network are affected most strongly by the changes, while customers close to the transformer are nearly unaffected by the changes, even with a one phase output (via L1) from all customers at 5 kW. In the simulated scenarios two networks has unbalance as a limiting factor, whereas the third network suffer unacceptable voltage rise and unbalance at nearly the same time. In the extreme scenario with an output power of 5 kW through L1 from 100 % of the costumers in the same network the lines and cables are still not overloaded, which proves that overloaded cables is a secondary problems compared to voltage variations and unbalances. The conclusion is that we do not see any serious threats to the quality of electricity at a larger share of PV-systems, as long as the installations are done in networks with a reliable dimensioning and a great awareness of the importance of three phase connections. However, the simulations have shown that there is an impact when many customers have a large production with an uneven output on the grid at the same time. One should therefore avoid scenarios where all costumers in the same network area has a PV-system with a power output in one single phase, while the loads are very low.

  • 155.
    Larsson, Albin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    NOx-reducerande åtgärder vid låg last av en fastbränslepanna med ureabaserat SNCR-system: Inverkan av körsätt och praktiska åtgärder2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    SCA Obbola AB is a kraft pulp mill that produces and sells packaging paper. The steam demand is covered by a recovery boiler and a solid fuel boiler (consists of two parallel solid fuel furnaces and a boiler). Adjustments in steam production are foremost made by the solid fuel boiler. Previously made energy-reducing measures at the mill has lowered the steam demand which forces the solid fuel boiler to low steam production. The solid fuel boiler produces over 25 GWH/year and is therefor bound by the Swedish nitrous oxide charge, but is also restricted to a monthly mean value of 70 mg/MJ. This mean value was exceeded in July 2016, which is thought to be a result of forced limitation in steam production. NOx emissions are reduced secondarily by an urea-based SNCR-system where its efficiency depends on several parameters, foremost sufficiently high flue gas temperatures.

    This work has identified parameters that effects foremost hydrogen-based combustion emission from the solid fuel boiler. This was achieved by evaluating historical data and by conducting tests during operation of the solid fuel boiler, which was planned and evaluated using a software called MODDE. Emission reducing measures and recommended ways to operate the boiler was then presented from the collected data.

    Practical measures including down-winding supply machinery of secondary air and replacement of urea injection showed no tendencies in reducing NOx emissions. However, complete shut down of one the furnaces produced at least 100 °C higher flue gas temperatures produced from the active furnace. Low NOx emissions was noted when secondary air was supplied from machinery with original speed. therefor, during stretched periods with low steam production, it's recommended that: Only one furnace should be active as steam producer, urea should be injected at its original placement in the flue gas chamber close the furnace and that secondary air should be supplied by machinery with original speed. Comparison test made in this work showed that this way of operating the solid fuel boiler could reduce NOx emissions with 45 % compared to mean NOx emissions at low steam production in July 2016.

  • 156.
    Larsson, Gustav
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Värmeleverans från pappers- och massabruk till sågverk2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Stenvalls Trä äger ett sågverk på Lövholmen i centrala Piteå. De har ett effektbehov på ca 10 MW värme för att torka virke i virkestorkar. Smurfit Kappa Kraftliner är ett integrerat pappers- och massabruk och även Piteås största producent av fjärrvärme. Fjärrvärme produceras främst med sekundärvärme, som är betraktat som spillvärme. Om fjärrvärmebehovet är stort används även primärvärme i form av ånga. Under vissa delar av året när fjärrvärmebehovet är lågt finns ett överskott av sekundärvärme. Stenvalls Trä är en tänkbar köpare av värme, men för att möjliggöra värmeleverans måste investeringar göras i form av en 3 km fjärrvärmekulvert, pump och värmeväxlare. För att undersöka konsekvenserna av en sammankoppling har en modell skapats i Excel som kan beräkna behovet av primärvärme för att ge rätt effekt och temperatur till Stenvalls Trä. Eftersom sågverket kräver hög temperatur måste en delmängd av flödet vara primärvärme. En undersökning har även utförts på sågverket för att fastställa effektbehovet till 10 MW och temperaturbehovet till 95°C. Värmen som levereras från Smurfit Kappa är 96°C och returen 80°C. Vid leverans vintertid när utetemperaturen är kallare än -10°C kommer all leverans ske med primärvärme. Turbinen som genererar el med ånga från biopannan är fullastad vintertid. Det innebär att primärvärme som används för leverans vid utetemperatur kallare än 0°C inte kommer ge ökad elproduktion. Vid högre utomhustemperaturer blir behovet av primärvärme lägre med bättre marginaler som följd, tack vare elproduktion och leverans av sekundärvärme. När det är olönsamt att leverera värme kan Stenvalls Trä använda sin egen biopanna. Möjligheterna för att det ska vara lönsamt att leverera värme vissa delar av året från Smurfit Kappa till Stenvalls Trä bedöms vara mycket goda.

  • 157.
    Larsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Analys av fördelningssystem för bostadshus2012Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of this project is to analyze earthing systems for houses. By practical measurements and theoretical analyzes consequences of possible faults, that can occur within the facility and in the low-voltage distribution network, is illustrated.  

    The reason for this project is that nowadays one has to arrange with a main equipotential bonding system for buildings. Apart from that, if necessary, bathrooms must be provided with a supplementary equipotential bonding system.

    The practical measurements verify that potential differences in facilities may be due to voltage drops in the PEN conductor between the origin of the electrical installation and the power transformer.

    Based on the theoretical analyzes of possible faults, it is considered that the requirement for  supplementary equipotential bonding systems for bathrooms in most cases can be questioned, when basic insulation, fault protection, residual current devise and main equipotential bonding system already provides an adequate level of protection.

    A PEN conductor loss may result in a situation where metallic parts attached to the equipotential bonding system starts working as earth electrodes. Equipotential bonding system may also increase the incidence of stray currents. If TN-C-S systems is provided with a local connection to earth a redundant system against PEN conductor loss is obtained. That is not the case for neutral conductor loss in TN-S systems with a local connection to earth. If district heating pipes is supplied with insulated flanges it prevents stray currents and foreign potential to be spread in the district heating network.

  • 158.
    Larsson, Sylvia H.
    et al.
    Swedish University of Agricultural Sciences, Unit of Biomass Technology and Chemistry.
    Rudolfsson, Magnus
    Swedish University of Agricultural Sciences, Unit of Biomass Technology and Chemistry.
    Nordwaeger, Martin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Olofsson, Ingemar
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Samuelsson, Robert
    Swedish University of Agricultural Sciences, Unit of Biomass Technology and Chemistry.
    Effects of moisture content, torrefaction temperature, and die temperature in pilot scale pelletizing of torrefied Norway spruce2013In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 102, p. 827-832Article in journal (Refereed)
    Abstract [en]

    Pilot scale pelletizing of torrefied Norway spruce was performed in a factorial design with controlled factors at two levels: material moisture content (11% and 15%) and torrefaction temperature (270 and 300 °C), and die temperature as an uncontrolled factor (60–105 °C). Compared to commercial wood pellets, produced pellets had comparable bulk densities (630–710 kg/m3) but lower pellet durability (80–90%). Energy consumption for pelletizing of torrefied materials was approximately 100% higher than for softwood pelletizing, despite using a much shorter die channel length (35 vs. 55 mm:s), and the amounts of fines were high (10–30%). Die temperature showed a strong positive correlation with pellet production rate. Material moisture content had little influence on pellet quality and production rate, but addition of water created handling problems due to bad flow behavior.

  • 159.
    Larsson, Tommy
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Determining the viscous splash losses in the housing of a hydraulic motor through CFD-simulations: A master thesis in collaboration with Bosch-Rexroth in Mellansel AB2017Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    One possible way of solving future energy shortages is by the optimization of our current energy consumption. These optimizations must span all possible fields of consumption. In the mechanical field radial piston hydraulic motors may show some margin of improvement. The radial piston hydraulic motor is driven by a pressure difference in hydraulic oil. These motors are commonly found in heavy industrial equipments such as drills and conveyor belts. The advantage with these motors in comparison with electric motors is the high torque and ability to absorb shock loads that may cause damage to electrical motors.

    The effectiveness of these motors are determined both by the motor and by the drive system as a whole consisting of hydraulic pump driven by a electric motor, hydraulic hoses, motor and possible external coolers. If the effectiveness of the motor is low the whole drive system will be affected thus amplifying the total losses. The losses in the motor can be both mechanical and derived to the viscosity of the oil. One region in the motor where there are viscous losses are in the housing. The housing is filled with oil, that both aids in the cooling and acts as a lubricant for the motor. Pistons and rollers are some of the components found in the housing. These components rotates around the centre line axis while having a pulsating radial motion following a cam ring. This rotating and pulsating motion will push oil in and out of a volume between two consecutive pistons and rollers. This will create viscous losses and regions with a enhanced risk of cavitation.

    This study investigates if the flow of oil in the housing can be simulated accurately. The study also examine what are the main problems regarding the flow of oil in the housing and the factors affecting the size of the viscous losses. The study also examines the correlation between viscosity and viscous losses. Finally two different optimizations with the intention of decreasing the viscous losses are compared.

    The study found that the majority of the viscous losses in the housing can be derived to the flow of hydraulic oil in and out of the volume between two consecutive pistons and rollers. The oil will pass a sharp edge around the cylinder block and a narrow passage under the spacing between the cylinder rows in a two cam ring configured motor. This will create regions with a enhanced velocity and risk of cavitation. The stroke of the motor will greatly affect the effectiveness of the motor especially at a high rotational speed. The viscous losses will be transformed into internal energy, heat, thus increasing the temperature of the oil. A increased temperature will decrease the viscosity and the viscous losses. The viscous losses will vary with 17 % if the viscosity is varied between 20 and 100 cSt. The developed model is not sufficient to determine the viscous losses accurately since the geometry had to be considerably simplified, but can act as a way of comparing different optimizations of the motor. The viscous losses can be decreased with 25 % in the CCe motor at 150 rpm by milling material of the cylinder block between the piston holes. This is an expensive optimization and needs to be justified from a cost-benefit perspective.

    The full text will be freely available from 2022-06-01 17:51
  • 160.
    Ledin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    The effects of processing conditions on crystallization of rr-P3HT for use in organic electronic devices.2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 161.
    Lee, Nicky
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Spränggenerator för rengöring av överhettare i avfallspanna: Utredning av drifterfarenheter och ekonomi i Umeå Energis kraftvärmeanläggning Dåva 12019Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The aim of this report was to evaluate a shock pulse generator installed at Dåva 1, the waste-fired combined heat and power (CHP) plant at Umeå Energi AB, located about 9 km northeast of Umeå. The study deals with the subject based on both technical aspects, in terms of operating experience and performance. Financial aspects, regarding repayment time and operating costs. With these results, an investment for a shock pulse generator has been discussed. Furthermore, proposals for improvements or combinations with ammonium sulphate should be discussed in order to prevent corrosion, in particular chlorine-induced corrosion.

    With the data logging program (ABB 800xa Smart Client), it was possible to study temperature trends and profiles at the superheaters. With these data, calculations have been performed to obtain a heat transfer coefficient (UA-value). The UA-value describes how the heat transfer changes over time and is therefore a measure of the degree of coating formation, and how the shock pulse generator influences this. Comparisons have been made for periods before and after the installation of the shock pulse generator. The study has included several interviews with the operation and maintenance staff concerning costs and experiences, to perform an economic calculation.

     

    The results show that the shock pulse generator have had a positive effect with an increase in the UA mean value by 7%. With reduced growth of deposits with the shock pulse generator, there are possibilities to reduce operating and maintenance costs. An improvement in the efficiency of the shock pulse generator could also have been achieved by increasing the frequency of explosion during periods where coating formation occurs. A future method could be to combine the UA-value with the shock pulse generator to create an intelligent soot-blowing system.

     

    The payback period for the installed shock pulse generator is estimated to be 5.7 years with a saving of SEK 385,000/year. For the assessment of an extra shock pulse generator, the evaluation indicate that it would probably not be as profitable as the present shock pulse generator.

    A minor literature study was also performed concerning deposit formation on superheater tubes and the effects of addition of ammonium sulphate. According to previous studies, deposits with a higher content of sulfur than chlorine are formed when using such additive, which causes deposits to become less corrosive and more porous, which makes them easier to be removed. This can be interesting for Dåva 1 and can be a suggestion for further investigation.

  • 162.
    Leonarde, Alexander
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Generationsskifte av vindkraftverk2011Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 163.
    Lindberg, Robin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Utveckling av rökgaskondenseringsmodell för kraftvärmeverk2014Independent thesis Advanced level (professional degree), 300 HE creditsStudent thesis
  • 164.
    Linder, Kristofer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Värmeåtervinning av gruvventilationsluft - LKAB i Kiruna2011Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In order to make underground mining production, large amounts of outdoor air

    must be pushed down to the mining level. At the LKAB facility in Kiruna this is

    done by a number of mining ventilations stations. The air has to be heated before

    it is transported down to the mining levels. This is done in order to prevent icing in

    the shaft. Today, the heating of the air is done by using waste heat from the pellet

    mills and if extra heating is needed, due to lower outdoor air temperatures, oil is

    used.

    The exhaust air from the underground is moist and warm. It is therefore interesting

    to investigate if it is possible to install a heat exchanger in the mine ventilation

    stations and use the heat in the exhaust air to heat the supply air. The heat recovery

    system which has been investigated in this study is a type of coil heat exchanger.

    Heat exchanger manufacturer has submitted a proposal on the type of coil

    heat exchanger that could withstand the specic demands and oer a price for the

    system. The chosen heat recovery system has four supply exchangers with the size

    4500x2000 mm and 3 exhaust exchangers with size 8000x2200 mm. Each Supply

    air coil had a power of 661 kW and each exhaust exchanger was sized at 882 kW.

    Analyses were made to estimate reductions in the use of oil by implementing

    the heat recovery system. In addition, also the amount of waste heat energy that

    could be saved by installing the heat exchangers was calculated. The calculations

    were carried out on a total of 9 mining ventilation stations.

    The energy that the rst installed station could save in form of oil during a

    year has been estimated to 4,7 GWh. If heat exchangers were installed in all the 9

    stations the energy reduction would be approximately 29 GWh per year.

    The energy that could be saved at station 1 in the form of waste heat was 0.6

    GWh per year. If heat exchangers were installed at all the 9 stations, the recoverable

    waste heat was calculated to be approximately 18 GWh per year.

    The nancial analyses were made for two cases. One that was based only on

    prots from the saved oil and, the other also by selling of the saved waste heat to

    TVAB.

    The total installation cost per station was estimated at to around 4.3 million

    skr. Considering the saved amount of oil the payback time for a single station was

    found to be approximately 1.4 years. For all the 9 stations the payback time was

    estimated to be 3.6 years.

    If sale of waste heat is included and added to the analysis, the payback time

    for a single ventilation station is 1,4 years and for an installation in all the stations

    the payback time is 2,4 years.

    The problems that could arise are due to contamination, which could be prevented

    by greater spacing of the battery heat exchangers and protective coating

    with Heresite. Expansion of the exhaust duct must also be made when the exhaust

    air coils are too big to t in the available channel .

    The calculations are based on the assumptions that the temperature of the

    exhaust air is 8

    . and the relative humidity is 100 % in all stations. The same

    kind of coil heat exchanger has therefore been used in the calculation of the dierent

    stations. In the next design step it is proposed that more accurate values for

    each station are provided to the heat exchanger manufacturer to improve design

    performance of the recovery system.

    A futher recommendation is that the rst installation of the heat exchange

    system should be implemented in ventilation station KV10 where there is plenty of

    space available for a heat exchanger system, and KV10 also has the second highest

    exhaust air temperature.

  • 165.
    Lindgren, Rickard
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Energikartläggning av en äldre fastighet: En kartläggning kring energiförbrukningen och kostnadsbesparande lösningar för en äldre fastighet2016Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    On the behalf of Norrporten in Umeå have an energy audit been made on an older part of a building. The goal has been to calculate the distribution of energy carriers in the property and to find out what the operating cost for the building is. With that in mind so have different methods to reduce energy and operating costs been examined and its effect on energy consumption. This survey analyzes ventilation, heating, water heating and climate shell of the property. Measures to reduce energy consumption due to operations in the building have not been examined.

    The simulation program IDA ICE was used for energy calculations. The results show that the property currently use about 150 MWh/year of heat and about 104 MWh/year of electricity. This means an annual operating cost of about 200 600 SEK.

    Among the largest energy consuming parts are:

    • Heating of the facility
    • Heating of domestic hot water
    • Ventilating el for fan operation

    The total savings opportunity is apparent to about 14,600 kWh/year of electricity and about 39,600 kWh/year of district heating.

  • 166.
    Lindholm, Kasper
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Analys av renoveringsåtgärder på ett flerbostadshus i samarbete med AB Bostaden2017Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this project the result of a refurbishment of a multi-family residential was analyzed from an energy perspective.

    The purpose of this project was to show how the different improvement measures that were performed in conjunction with the refurbishment impacted the district heating demand of the building.

    To analyze the building and the improvement measures the simulation program IDA Indoor Climate and Energy was used. In the program the buildings district heating demand before the refurbishment, after the refurbishment and in the seven cases listed below was simulated:

    • If the windows had not been exchanged from double pane to three pane.
    • If the building’s exterior walls had been additionally insulated inwards.
    • In the scenario of where the insulation in the attic had not been exchanged.
    • If neither of the exterior walls had been additionally insulated nor had the insulation in the attic been exchanged.
    • If the buildings airtightness had remained unchanged after refurbishment.
    • If the ventilation system in the building had not been switched to a FTX-system.
    • If the buildings airtightness had remained unchanged and if the ventilation had not been switched to a FTX-system.

    The results of the simulation before the refurbishment, showed that the buildings district heating demand was 160 kWh/m2. The simulation of the building after it was refurbished resulted in the district heating demand being lowered to 71 kWh/m2.

    When simulating the cases listed above, it was determined that the measure that gave the most significant decrease in district heating usage was the installation of the FTX ventilation system. If the building had been renovated without installing the FTX the district heating demand would have risen with 65 kWh/m2.

    The measure that had the second largest impact on the buildings district heating usage was the improvement of the buildings airtightness. The simulation for the case in which in the buildings airtightness remained unchanged resulted in that the district heating usage was increased by 28 kWh/m2.

    The result of the simulation where the windows were not exchanged showed an increase in district heating usage by 24 kWh/m2. The district heating demand increased by 4 kWh/m2 in the simulation where the building’s exterior walls had not been additionally insulated. The results for the case when the insulation in the attic was not exchanged showed an in increase in district heating usage by 3 kWh/m2.

    The conclusion that could be drawn as a result of the simulation results was that the different renovation measures should be prioritized as following, for buildings with similar preconditions:

    1. Install FTX ventilation system
    2. Increase the building's airtightness
    3. Exchange windows
    4. Additionally insulate external walls
    5. Additionally insulate / exchange insulation in the attic.
  • 167.
    Lindmark, Jonas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Energikartläggning och energieffektivisering av Trinnliden 7:5: Simulering av energibesparande åtgärder i "IDA Indoor Climate and Energy"2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    On behalf of GATE Intelligent Support AB an energy audit has been conducted in the spring of 2015. The project was to develop an energy audit at an industrial premise in Vännäs municipality. Vännäs Fastigheter AB is the owner of this venue and has recently received complaints from tenants about an cold indoor climate in the property. Furthermore, it emerged that the property's future energy supply of heating is uncertain. Therefore a separate project to find an alternative heating sources solution has been initialized. This report will place great emphasis on changes, which lead to an improved indoor climate as to energy savings. To achieve this plan and to make it more understandable the simulation program IDA ICE has been used throughout the whole paper. Additionally, economic calculations for an LCC-analysis including repayment time has been done to compare the measures easier. Results from this project have demonstrated that this industrial premise can when all energy saving measures are carried out, reduce their energy consumption from 299 MWh per year to 129 MWh per year. This means a total decrease of 56.9%. The inspection of the property reveals shortcomings in the existing heating system. The current radiator system was configured wrong which resulted in a significant reduction of the heat outcome. This was not just done by changing settings of the radiator system but as well by adjusting the ventilationsystem to the business conditions of the property. 

  • 168.
    Lindström, Erica
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Larsson, Sylvia H
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Öhman, Marcus
    Slagging tendencies during combustion of woody biomass pellets made from  a range of different forestry assortments2010In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 24, no 6, p. 3456-3461Article in journal (Refereed)
    Abstract [en]

    In this study, multivariate methods were used to select representative raw materials of the pellet assortments prior to combustion. The fuels were selected to form a range of expected slagging tendencies. During combustion, temperatures and O2, CO, NO, and SO2 were measured continuously. The deposits (i.e., slag and bottom ash) were quantified after every experiment and collected for analysis to identify the crystalline phases and to study the morphology and elemental composition respectively. As expected, the slagging was most severe for the whole-tree assortments because of their content of branches, foliage, and twigs. In the most severe case over three-quarters of the total amount of ash melted to form slag. This study indicates that certain concentrations of silicon, inherent in the fuel but also as silicates from contamination, together with alkali metals, mainly potassium, are prerequisites for the initiation of and progress of slag formation. Generally the concentrations of silicon and potassium are low in stemwood but higher in bark, foliage, and living tissues of the tree. Also, the contamination from sand and/or soil is present in the bark and foliage.

  • 169.
    Lodin, Tobias
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Modellering och analys av ventilation i stängda motorutrymmen2016Independent thesis Advanced level (professional degree), 300 HE creditsStudent thesis
    Abstract [en]

    This thesis work, which totally include 30hp, was performed in cooperation with BAE Systems Hägglunds in Örnsköldsvik. They are trying to reduce the cost for their new vehicles, Beowulf, which is constructed for professional civil customers. The engine bay ventilation today utilizing a high rpm military axial fan. The cost for the fan is high because the requirements from the military are high, specially the EMC requirement. Since Beowulf is for civil customers there are no need for those military requirements, therefore is this thesis works focused on are any cheaper solutions for the engine room ventilation.In this work, the heat generation in engine bay and the required air ventilation have been determined through theoretical calculation in Excel. A model has been created, in FloEFD 13, for simulation of the pressure drop in the ventilation system in the engine bay. Another simulation model was created to simulate a solution where the engine bay was ventilated through the cooler fan. A concept generation were also done to find advantages and disadvantage with different ventilation solutions. Finally measurements were made to see how the temperature in the engine bay reacts when the fan is shut off, during amphibian driving and also how the engine after heat affects the temperature.From the results of the simulations and real tests it was shown that the ventilation through the cooler fan would work. In the concept generation it was shown that there are cheap solutions that would reach the requirement ventilation flow if the fan is changed to an electric or hydraulic radial fan.From this reports the conclusion is that there are suitable fan solutions that are a lot cheaper than the fan that is used today. The best solution is reached by using the original cooler fan instead of a separate engine bay fan. This solution would reduce the cost for engine bay ventilation with more than 90 %.

  • 170. Lou, Benyong
    et al.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Velaga, Sitaram P.
    Polymorph control of felodipine form II in an attempted cocrystallization2009In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 9, no 3, p. 1254-1257Article in journal (Refereed)
    Abstract [en]

    The metastable form II of racentic felodipine was obtained in an attempted cocrystallization with isonicotinamide. Its low temperature crystal structure was characterized by a ID hydrogen-bonded chain consisting of four independent felodipine molecules.

  • 171.
    Lund, David
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Rundstyrning i lokalnät: En förstudie i tekniska och ekonomiska konsekvenser för Värnamo Elnät AB2012Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Värnamo Elnät owns and operates a ripple control system which is used to control loadsespecially when the grid is heavily loaded and for control of street lighting. This report aims atclarifying technical and economic aspects of the ripple control system’s future. The system wasinstalled from 1975 and onwards and its use was greater in those days when the controllableloads where greater then today, the current controllable load level is about 3 MW. The reporthighlights three different aspects of the ripple control system’s future – retain the currentsystem, reinvest in a newer system or discontinue the system.In the report the author also discusses relevant connections to Smart Grids and future meteringsystems and tariffs. The author senses a will from the company to discontinue the system on along term, but also a will to be able to control loads on the grid. Therefore the author suggeststhat the system should remain in operation for another 5 to 10 years, under the condition ofanother investigation of the remaining customer base.

  • 172.
    Lundberg, Daniel
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Bergvärme och solenergi i flerbostadshus: En förstudie över Kv. Uppfarten2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
  • 173.
    Lundberg, Mattias
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Språkförskolan: En jämförelse mellan CAV- och VAV-system2019Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report examines the profitability and energy-saving potential of replacing the existing CAV system with a VAV system in Språkförskolan, which is located in Umeå in the Marielund/Olofsdal area. The project is carried out in collaboration with Tyréns in Umeå, which is a consulting company and one of the leading companies in urban management in Sweden.

     

    With the help of IDA ICE, which is an energy calculation program, a model of the preschool could be built in 3D based on floor plan drawings and settings such as the number of people, lighting, ventilation systems and air flows, indoor temperature and so on adjusted so as to be as similar to the actual building as possible. When all values ​​were set, an energy simulation was made in the program, which gave a lot of values ​​such as annual energy consumption for different systems in the building and heat losses through the building envelope. The file was duplicated, and the CAV system was replaced by a VAV system and another simulation was started. Based on the simulation results, energy consumption for the heating system and the fans was compared in both cases.

     

    In AutoCAD, a ventilation solution was designed with the VAV system in one department of the preschool, with associated VAV dampers that automatically adjust the airflow according to the measured load in the room. The CAV system does not adjust the airflow but goes to the maximum dimensioned flow all the time which is not energy efficient in rooms with varying loads (people).

     

    The results from the simulations showed that with variable ventilation, the total annual energy consumption decreased by 20 953 kWh, which is a reduction of 26%. Of this energy saving, the heating system accounted for 67% and the fans for 33%. The investment cost for installing VAV dampers in the building is SEK 192,000, and based on the annual savings the payback time was calculated to 19,7 years. With a lifetime of 25-30 years, an investment of the VAV system is considered to be profitable.

  • 174.
    Lundberg, Petter
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Investigation of the transient nature of rolling resistance on an operating Heavy Duty Vehicle2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    An operating vehicle requires energy to oppose the subjected driving resistances. This energy is supplied via the fuel combustion in the engine. Decreasing the opposing driving resistances for an operating vehicle increases its fuel efficiency: an effect which is highly valued in today’s industry, both from an environmental and economical point of view. Therefore a lot of progress has been made during recent years in the area of fuel efficient vehicles, even though some driving resistances still rises perplexity. These resistances are the air drag Fd generated by the viscous air opposing the vehicles propulsion and the rolling resistance Frr generated mainly by the hysteresis caused by the deformation cycle of the viscoelastic pneumatic tires.

    The energy losses associated with the air drag and rolling resistance account for the majority of the driving resistances facing an operating vehicle, and depends on numerous stochastic and ambient parameters, some of which are highly correlated both within and between the two resistances. To increase the understanding of the driving mechanics behind the energy losses associated with the complexity that is rolling resistance, a set of complete vehicle tests has been carried out. These tests were carried out on the test track Malmby Fairground, using a Scania CV AB developed R440 truck equipped with various sensors connected in one measurement system. Under certain conditions, these parameters can allow for an investigation of the rolling resistance, and a separation of the rolling resistance and air drag via explicit subtraction of the air drag from the measured traction force. This method is possible since the aerodynamic property AHDVCd(β) to some extent can be generated from wind tunnel tests and CFD simulations.

    Two measurement series that enable the above formulated method of separation were designed and carried out, using two separate measurement methods. One which enables the investigation of the transient nature of rolling resistance as it strives for stationarity, where the vehicle is operated under constant velocities i.e. no acceleration, and one using the well established method of coastdown, where no driving torque is applied.

    The drive cycles spanned a range of velocities, which allowed for dynamic and stationary analyses of both the tire temperature- and the velocity dependence of rolling resistance. When analysing the results of the transient analysis, a strong dependence upon tire temperature for given constant low velocity i.e. v ≤ 60 kmh−1 was clearly visible. The indicated dependency showed that the rolling resistance decreased as the tire temperature increased over time at a given velocity, and vice versa, towards a stationary temperature and thereby rolling resistance. The tire temperature evolution from one constant velocity to another, took place well within 50 min to a somewhat stationary value. However, even though the tire temperature had reached stationarity, rolling resistance did not; there seemed to be a delay between stationary tire temperature, and rolling resistance. The results did not indicate any clear trends for v ≥ 60 kmh−1, where the results at v = 80 kmh−1 were chaotic. This suggests that some additional forces were uncompensated for, or that the compensation for air drag was somehow wrongly treated at higher velocities.

    Several factors ruled out any attempts at proposing a new rolling resistance model. These included: the chaotic results for v = 80 kmh−1, the delayed rolling resistance response upon tire temperature stabilization, and the lack of literature support for the observed tendency. The results from the coastdown series on the other hand, showed good agreement with a dynamical model suggested in literature. The stationary temperature behaviour for the considered velocity range at assumed constant condition is also supported in literature.

    Finally, an investigation of the aerodynamic property AHDVCd inspired by ongoing work in ACEA (European Automobile Manufacturers’ Association), was carried out assuming both zero and non-zero air drag at low velocities. The results indicated surprisingly good agreement with wind tunnel measurements, especially when neglecting air drag at low velocities: as suggested by ACEA. 

  • 175.
    Lundegård, Erik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Energy recovery – Gasification, combustion or plasma?: Competitor or complement?2018Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Abstract

    Energy recovery – Gasification, combustion or plasma?

    -          Competitor or complement?

    The Swedish waste-to-energy system has been developed during many years, and the facilities are well established within the waste management system. Even though the waste volume is significantly reduced by 70 – 80 %, the residues are quite challenging to manage due to high content of pollutants. The air emissions are quite low today, but since waste contains various kinds of contaminants, there is a high need for extensive flue gas cleaning, adding to the residue that must be handled. Today, the main part of residues from flue gas cleaning and fly ash from Swedish waste-to-energy facilities are transported to Langöya, Norway to be used for remedial purposes of an old limestone quarry. However, this option will probably be phased out sometime after the year 2023 – 2025 and other solutions must be considered such as e.g. gasification.

     

    The Plagazi Company has a patented process, including gasification and subsequent production of hydrogen gas, that may be used as a vehicle fuel. Although gasification is a well-known technique, there is still a great distrust in using the method for waste treatment purposes. There is a conception that gasification facilities are high energy consumers, with low operational performance and high investment costs. The present thesis is part of the B.Sc. Programme in Energy Engineering at the University of Umeå. The main thesis objectives are:

     

    • Study and explain significant differences and similarities between waste incineration and gasification;
    • Describe pros-and-cons regarding various methods to produce hydrogen gas;
    • Describe different gasification techniques.

    In addition, the Plagazi-process is described; local plasma gasification with low environmental impact and a second step including production of hydrogen gas. The present study is based on a literature review and interviews with experts in the field. The report excludes biogas production in anaerobic digestion plants.

     

    The present report has proven that there are significant differences between various gasification devices. When making investment decisions regarding gasification as a waste treatment option; fuel quality and utilization of the syngas must be considered.

    The method developed by Plagazi may be suitable in the Swedish waste management system to treat household waste and/or flue gas residues from the combustion plants, for production of hydrogen gas as a vehicle fuel. A full-scale facility in operation is needed to evaluate the Plagazi process with respect to cost efficiency and performance. The Plagazi concept should not be viewed as a competitor to the profitable waste incineration plants, more preferably as a complement. 

  • 176.
    Lundholm, Karin
    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.
    Backman, Rainer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Trace element speciation in combustion processes: review and compilatons of thermodynamic data2007In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 88, no 11-12, p. 1061-1070Article in journal (Refereed)
    Abstract [en]

    Chemical equilibrium calculations are often used to determine the fate of trace metals in combustion processes and to study the effects of different process variables and varying fuel compositions. In the present report, thermodynamic data on compounds containing the trace elements As, Cd, Cr, Cu and Pb from different database sources are compared. The results showed significant differences between existing databases in both number of compounds included in the databases and thermodynamic data. The differences also significantly affected the outcome of the equilibrium calculations.

  • 177.
    Lundholm Ljungkvist, Hampus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordstjärnan som nära-nollenergibyggnad2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Examensarbetets syfte var att utvärdera hur Umeå kommuns egna energikrav står sig mot det kommande kravet på nära-nollenergibyggnader, NNE-byggnader. Som underlag för utvärderingen på Umeå kommuns kombinerade förskola/äldreboende Nordstjärnan gjordes en energibalansberäkning i simuleringsverktyget IDA ICE. Genom att bestämma byggnadens energiprestanda enligt NNE-kravets författning Boverkets Byggregler, BBR, 26 och enligt tidigare författningar, BBR 24 och 25, kunde utvärdering ske. Byggnadens energiprestanda jämfördes med Umeå kommuns och BBR 24, 25 och 26 krav. Resultatet av utvärderingen visade att Nordstjärnan klarade kraven med kombinerad fjärr- och bergvärme som uppvärmning. Marginalen till BBR 26 krav och Umeå kommuns krav blev 4 % respektive 3 %. Utvärderingen visade också att byggnaden inte hade klarat något av de två kraven om uppvärmningen endast utgjorts av fjärrvärme. Slutsatsen är att Umeå kommuns energikrav är hårdare än BBR 26 krav för byggnader liknande Nordstjärnan. Någon generell slutsats om Umeå kommuns krav mot BBR 26 krav kunde inte dras. Detta på grund av att kraven bygger på olika författningar med olika metoder för bestämning av byggnadens energiprestanda.

    Vidare undersöktes en egen energiproduktions påverkan på Nordstjärnans energiprestanda. En solcellsanläggning simulerades i programmet PV*SOL. Den mängd solel som momentant kunde nyttjas till byggnadens energianvändning och byggnadens nya energiprestanda beräknades. Resultatet visade att den simulerade solcellsanläggningen förbättrade Nordstjärnans energiprestanda enligt BBR 26. Förbättringen blev 12 % vid fjärrvärme och 14 % vid kombinerad fjärr- och bergvärme som uppvärmning. Byggnaden klarade då NNE-kravet vid både fjärrvärme och kombinerad fjärr- och bergvärme med 4 % respektive 16 % marginal.

    Det noterades att byggnadens utformning var bristfällig, sett ur ett energiperspektiv. En enklare undersökning av hur en förbättring av formfaktorn påverkar byggnadens uppvärmningsbehov gjordes. Byggnadens specifika uppvärmningsbehov förbättrades med 5 % samtidigt som byggnadens genomsnittliga värmegenomgångskoefficient, Umedel , försämrades. Slutsatsen av detta blev att energiteknisk kompetens bör kopplas in i ett tidigt skede för att i samråd med arkitekten kunna göra förändringar av byggnadsutformningen. Den visade också på att en byggnads Umedel inte räcker för att bedöma en byggnads konstruktion ur energisynpunkt. Även formfaktorn bör beaktas. 

  • 178.
    Lundin, Mattias
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Voutilainen, Karl-Oskar
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Vinddataanalys för vindkraft Storfall: behandling och analys av mätdata från sodarmätning samt produktionsberäkning2012Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In recent years the interest in wind power has increased in Västerbotten. The wind resources are generally good while it is sparsely populated. Apoidea is on behalf of the Baltic Group investigating the possibility of establishing a wind farm with about 20 wind turbines northwest of Nordmaling. Wind measurements have been taken for a little more than a year to confirm the wind conditions at the site. The measurements were made with sodar, a kind of remote sensing equipment. The Sodar is an acoustic device which sends out sound signals and then records the rebounding echo to measure wind direction and speed. The technique is based on the Doppler Effect. The signals sent out reflects on temperature stratifications in the air and changes frequency which the sodar registers. Two sodars with support system have been used and they have been placed in different locations around the project area. One sodar has been kept at a location named 006 throughout the entire measure period. While the other sodar during the same period has been moved around to three different locations, each named 071, 072 and 073. The aim of the project was to analyze sodar data to quality check the measurements and calculate the potential energy production. To make this possible the correlation between fixed and mobile sodar was analyzed. This is to receive proof of how well the two measurements align during the period. A long-time correction of 006 has been made and analyzed. As a long-time reference NCEP/NCAR reanalysis data has been used. The areas that were selected to be analyzed includes availability, wind speed, quality and energy production. Most analyses were made in WindPRO or Microsoft Access. The analysis resulted in an estimated availability at between 53 and 86 %. The quality at 120 m is between 90 and 95 % for all measurements. The correlation between sodar 006 and 071 was estimated to 0.90 sector wise weighted average, for sodar 006 and 072, 0.85 and for 006 and 073, 0.86. The correlation between fixed sodar and long-term reference for the time period 2010-06-01 to 2011-10-01 was calculated to 0.64. The statistically corrected average wind velocities were all lower than the 006 measurement and are in the range between 6.54 to 6.67 m/s compared to 6.77 m/s for 006. The method we chose, which included an examination at several measurements in the same area during the same period and the use of the analysis and planning tool WindPRO to analyze these values, is what we understand a common approach. The results of the correlation between measurement sites are high in all locations, which gve a more reliable result, even if two different methods would have been preferred for the validation of the measurement. But this was not possible since there was no mast available in the area. The terrain in the area can be described as complex. Therefore caution was used when the results of the measurements were interpreted. The low availability depended largely on problems with the support system such as the generator. The correlations between the two different sodars are high throughout the entire period and together with the quality results they are validating the measurement. In future projects it would be recommended to include a mast measurement to correlate against. Further comparisons of long-term data would be needed to make reliable production estimates.

  • 179.
    Lundin, Mikael
    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.
    Östin, Ronny
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Development and validation of a method aimed at estimating building performance parameters2004In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 36, no 9, p. 905-914Article in journal (Refereed)
    Abstract [en]

    This paper presents a method for estimating the total heat loss coefficient, the total heat capacity and the gain factor based on measured data for the internal-external temperature difference, the domestic load and the supplied heat. Knowledge of these performance parameters is essential for a reliable energy demand forecast, close guidance and the accurate analysis of efficiency actions in buildings. The method was validated on measurements from a test cell. The values obtained for the performance parameters were in good agreement with a lumped capacitance analysis of the heating and cooling of the test cell. The deviation in the total heat loss coefficient, expressed in terms of the root mean square error, was between 2.5 and 9.4%. The values obtained for the total heat capacity were on average 9.8% higher than the reference value and for the gain factor the average deviation was 12.5%. The method shows promising signs of becoming a robust and accurate tool for extracting both the magnitude and the variation of the performance parameters, based on easily accessible data.

  • 180.
    Lundin, Mikael
    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.
    Östin, Ronny
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Further validation of a method aimed to estimate building performance parameters2005In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 37, no 8, p. 867-871Article in journal (Refereed)
    Abstract [en]

    A further validation of an earlier developed neural network method for estimating the total heat loss coefficient (K-tot), the total heat capacity (C-tot) and the gain factor (alpha) based on measured diumal data of internal-external temperature difference, supplied heat for heating and "free heat" is presented. The validation was performed in laboratory scale, using a test cell, for three different cases of ventilation, without (constant)-, natural-, and forced ventilation. Earlier measurements from a building was also used in order to simulate a realistic energy use pattern and a rather stochastic behavior of alpha, which also was transformed to represent existing and future buildings in terms of the composition of their energy use. For all three types of ventilation and different types of buildings, the method was capable of estimating the three different performance parameters and their different dependencies. For K-tot, the RMSE was between 3 and 20% and for alpha, the deviation was between 9 and 19%.

  • 181.
    Lundmark, Martin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Evaluating a high rise building for passive house classifications: Simulating and improving the Slovenian Eco Silver House in European climates using PHPP2015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As part of the EU project Energy Efficient Demo Multiresidential highrise Building (EE-highrise), this thesis work evaluates and changes the Slovenian Eco Silver House (ESH) high rise building model in order to see if it can be classifiable as a passive house in different European regions.

    The purpose of this thesis work was to evaluate if the ESH could meet the European and Swedish passive house classification in Sibernik, Ljubljana, Lund, Östersund, Sundsvall and Kiruna. The purpose was also to make a sensitivity analysis of different energy efficiency measures in the energy performance of the building. This analysis was conducted to understand which of the selected energy efficiency measures made the most significant improvements in the results. The measures included in the sensitivity analysis were the building envelopes wall insulation thickness, changing the window frames, altering the ventilation air duct length and width as well as increasing the air duct insulation thickness. Finally, simulations with solar panels on the roof of the ESH were carried out.

    For the European passive house classification, the study involved constructing the model in the Passive House Planning Package (PHPP) and simulating each region and energy efficiency measures separately. PHPP is however made specifically for verifying buildings according to the European passive house standard. So the demands for the Swedish passive house classification cannot be calculated in the PHPP simulations. Because of this, the data available through PHPP was used to manually calculate the Swedish passive house requirements.

    The results showed that the original ESH model, was only passive house certifiable according to the European classification in Sibernik. When including the additional energy efficiency measures it was possible for the ESH to become passive house certifiable in Lund, Ljubljana and Sibernik.

    The Swedish passive house classification results suggests that the ESH may be passive house certifiable in Lund. Also, with additional energy efficiency measures the ESH may meet the passive house requirements in Sundsvall and Kiruna. However, all the passive house classification parameters could not be considered in this study. Accordingly, additional analysis are required to draw final conclusions on whether the ESH building could meet the Swedish passive house certification in the different Swedish climate zones.

    The conclusions drawn were that all the energy efficiency measures contribute to reducing the primary energy demand, heating demand and the heating load. However, these same energy efficiency measures would at the same time increase the cooling demand. Because of this, it was discussed that specific regional models should be made. Because some regional models might benefit from not including the energy efficiency measures used in this thesis at all. They might instead benefit from finding and implementing energy efficiency measures that reduce the cooling demand.

  • 182.
    Lundström, Oskar
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Utredning av effektiva elmotorer för fläktdrift2012Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Fläkt Woods is a global manufacturer of fan and air climate systems, they produce the fans and climate systems themselves but they buy the motors from other manufacturers. The objective in this report is to compare the technical differences between the motors and to find where each motor is best used.

    The EC and PMSM-motors are both permanently magnetized and over all they are built very similar. The main difference is shown in the back-EMF, the EC-motor is using a trapezoidal back-EMF while the PMSM-motor uses a sinusoidal back-EMF. The PMSM-motor has a higher degree of efficiency, especially at higher speeds. At lower speeds there are EC-motors showing higher efficiency then the PMSM-motor at around 1300 rpm and below. The second main difference between the motors is the sensors. The EC-motor can use hall-sensors, while the PMSM-motor need more sophisticated sensors because of the sinusoidal current.

    To lower the electric cost of motors a very important part is to dimension it appropriate. If the motor is over dimensioned the efficiency will be lowered because it won’t operate at its optimal speed. Both the EC and PMSM-motor have better efficiency then the older AC-motor, despite this it is still up to the customer to decide what type of product they want to buy. Today the most sold motor for fans is still the AC-motor. This is because of the AC-motors simple construction, the customers high knowledge about the motor and because it is much easier to find spare parts. 

  • 183.
    Löfgren, Helena
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    NOx-reducering vid avfallsförbränning2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Waste incineration is used to reduce the volume of waste, destruction of hazardous waste and to extract energy in combined heat and power plants (CHP). Umeå Energi’s CHP Dåva 1 incinerates municipal solid waste (MSW) and other hazardous waste. Nitrogen oxides (NOx) are formed in the combustion process. The emission of NOx is regulated in Sweden’s regulation SFS 2013:253 and law 1990:613. Dåva 1 uses selective non-catalytic reduction (SNCR) with ammonia as flue gas treatment, to reduce NOx in the flue gas. Some of the ammonia in the process remains unreacted (ammonia slip) and it probably contributes to corrosion in the colder economizer. Umeå Energi wants to reduce the NOx emissions without increasing the ammonia related corrosion of the economizer. In the present study, the possibility to reduce NOx formation by SNCR optimization was evaluated. Furthermore an investigation on the use of selective catalytic reduction (SCR) in waste incineration plants in Sweden, and whether it is beneficent to install in Dåva 1, was included. The current efficiency of the SNCR system was tested by switching of the ammonia in short periods of time and measuring and logging the flue gas composition. The efficiency (80 %) proved to be very high if operated at the optimal temperature. ButHowever, the test also showed that the temperature limits for the injection levels could be optimized for improved efficiency. Improved efficiency at all temperatures could reduce both NOx emission and ammonia use. The use of SCR in Swedish waste incineration plants was investigated through interviews. It was found that only five plants are equipped with SCR and they were placed in the clean gas position – after electrostatic precipitatorelectric filter and wet scrubber treatment. The contents of the flue gas was examined monitored at three positions at Dåva 1. The content of SO2, HCl and dust were measured, which in combination with ammonia can cause coating with reduces the efficiency of the catalyst. All three positions were located after the textile filters and had low contents of dust. Position A was located between the textile fabric filters and the economizers and was the hottest position with 205℃. Position B was located after the economizers and had the temperature of 145℃. Position C had the cleanest and thereby the safest position for a catalyst, due to its location after all the flue gas treatments, but the temperature was only 65℃ and requires most re-heating of the flue gas. Since the SNCR system proved to have potential to be more efficient, it should be optimized before considering an investment in a SCR system.

  • 184. Ma, Charlie
    et al.
    Backman, Rainer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Ohman, Marcus
    Thermochemical Equilibrium Study of Slag Formation during Pressurized Entrained-Flow Gasification of Woody Biomass2015In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 29, no 7, p. 4399-4406Article in journal (Refereed)
    Abstract [en]

    The potential slag formation behavior during pressurized entrained-flow gasification (PEFG) of woody biomass has been studied from a thermodynamic perspective with respect to compositional, temperature, and pressure variations. An ash transformation scheme was proposed on the basis of the melt formation potential that arises when gaseous K species are present with Si and Ca. Databases and models in FactSage 6.4 were used to carry out thermochemical equilibrium calculations within ChemSheet. It was found that increasing pressure and increasing Si content expanded the range of operating conditions that are conducive of melt formation, while increasing temperature and increasing Ca content diminished the range. The results from the calculations compared qualitatively well to experimental results and provide further information needed in the development of PEFG reactors for woody biomass.

  • 185.
    Mannberg, Andreas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Utredning av värmesystem på ICA Kvantum Umeå2012Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The total energy consumption in Sweden reached 457 TWh in the year of 1970, and today is 600 TWh. It shows how our use has increased recently and that we should do something about it. The whole chain from energy production to energy use needs to be more efficient. A study conducted by ICA Fastighet AB shows an average energy use among grocery stores of 421 kWh/m2 year. ICA Kvantum Kronoparken in Umeå has a specific energy use of 658 kWh/m2 year, it shows that the energy use is high and above the mean average.

    The project aims is to conduct a case study at ICA Kvantum Kronoparken in Umeå by mapping the total energy use by the selected energy use categories in the shop. Furthermore, investigate various alternatives to replace the electric boiler which supplies the building with heat today.

    Today, the property has a total energy use of 2 237 MWh/year in a heated area of 3 400 m2. The analysis was conducted by separating the total energy use in seven main categories. By doing that it is easy to find the categories of high energy efficiency potential. Separation as follow:

    • Lights
    • Ventilation
    • Heating
    • Food cooling
    • Comfort cooling
    • Hot water
    • Operational electricity

    After completing the case study it showed that food cooling is responsible for approximately 42 % of total energy use, and also there you have the highest potential in saving energy and money. Other major users are area operational electricity which accounts for 21 % and includes all other equipment and use in addition to the above categories. The areas where energy efficiency measures were possible are lights, ventilation and cooling food. After these measures a given potential of the total energy use reduction by 20 % from 2 237 MWh/year down to 1 818 MWh/year.

    District heating and geothermal heating are the heat sources which best could replace the existing electric boiler. District heating has a lower investment cost and higher annual cost than geothermal heat, which is the opposite. Both have a payback period of 4-6 years which is considered as viable.

    The project focused on the property heating system, which only represents 7 % of total use. That compares to cooling food which represent 42 %. If the project was focused on food cooling rather than the heating system greater savings may has become possible. A recommendation for the future is to explore the cooling food system more, and also study and explore if free cooling is possible in winter. Today is not used, and it may be one of many factors that make the property’s energy use so high. 

  • 186.
    Mattias, Jonsson
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Planeringsnivåer och Störutrymme: En studie i övertonshalt och kravställning på lågspänningsnätet2018Independent thesis Advanced level (professional degree), 300 HE creditsStudent thesis
    Abstract [sv]

    Elektricitet blir allt vanligare i hemmet och idag är stora delar av samhället beroende av en avbrottsfri elförsörjning. När transistorn gjorde sitt intåg runt 1950-1960-talet skedde en förändring i de elektriska lasterna på nätet; från att vara mestadels linjära resisistiva laster tillkom flera olinjära laster i form av till exempel radio och TV.Med dessa olinjära laster uppstod problem med elkvaliteten som tidigare inte funnits i större utsträckning.

    Umeå kommun har de senaste åren satsat på helelektriska bussar som en del av en lösning på de problem man haft med buller och dålig luftkvalitet i centrala Umeå. För att driva dessa elbussar används snabbladdare, vilket är en kraftigt olinjär last. I en tidigare studie påvisades att under tider när laddning skedde hos dessa snabbladdare kunde det förekomma höga övertonshalter, där elkvalitetsnormen EIFS 2013:1 emellanåt överskreds.

    Syftet med det här arbetet är att utröna vilka krav Umeå Energi bör ställa vid nya bussladdare och vilka krav som borde ställts vid de första bussladdarna, gällande elkvalitetsstörningar. Målet är att föreslå planeringsnivåer som Umeå Energi kan använda för att ställa krav och fördela störutrymme för kunder. Det finns flera olika modeller för att fördela störutrymme där målet är att föreslå en som passar Umeå Energis nät. Endast planeringsnivåer för övertoner föreslås då övertoner visade störst problematik i den tidigare studien.

    För att bestämma planeringsnivåer gjordes trendanalyser på övertonsdata från fyra nätstationer och fem transformatorer under fyra års tid. Trendlinjer plottades upp med minsta kvadratmetoden och planeringsnivåer bestämdes utifrån hur mycket övertonshalten hade ökat relativt elkvalitetsnormen EIFS 2013:1.

    De planeringsnivåer som föreslogs ligger mellan 85 % till 100 % av de krav som EIFS 2013:1 ställer. Metod för fördelning av störutrymme föreslås följa metoden i ”Fördelning av störutrymme” som publicerades i en energiforskrapport. Slutsatser från det här projektet är att det är svårt att bestämma generella planeringsnivåer på lågspänningsnätet och det saknas metoder som beskriver hur det ska göras. Vidare har det visat sig att de flesta övertoner, upp till 25:e övertonen,ökar på Umeå Energis elnät, på de punkter som undersökts. Framförallt uppvisar den 7:e övertonen en större ökning än de andra.

  • 187.
    Medin, Johan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    TRACE-modellering av kondensatsystem vid Ringhals 42016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Nuclear power plants such as Ringhals 4 have undertaken major investments in technical improvements during the last decade to ensure secure operating and to increase efficiency. All activity concerning nuclear processing is performed under heavy regulation and it is therefore desirable to better anticipate how changes in components or new operating guidelines will implicate the overall process.

    The modern nuclear reactor system operates at a level of complexity where simple math and theoretical models are not capable of performing complete process calculations. Complex numerical schemes have therefore been developed to serve as powerful tools in solving the partial differential equations that describe two-phase flow and heat transfer. One of these numerical schemes is the code TRACE (TRAC/RELAP Advanced Computational Engine) that is used in this project. The objective was to compare results from the theoretical model in TRACE for the condenser system at Ringhals 4 with actual data obtained under normal operating conditions.

    The main components of the condenser system is composed of condenser-pumps and drain coolers with low pressure pre-heater. The main task of these pumps is to increase the static pressure in the system while the drain cooler with the preheater’s main objective is to raise the temperature.

    The graphic interface SNAP (Symbolic Nuclear Analysis Package) was used to design the model with constructional drawings and internal documentation as complementary sources. The boundary conditions used are sourced from either local readings, heat- and mass balance or logged values. The analysis was broken down in three different parts with focus initially on the pump system and preheaters. For completeness, the two systems were thereafter assembled to represent the whole condenser system.

    Satisfactory results have been obtained considering the main objective. Also discovered was that the theoretical model has a great sensitivity with new initiating values for temperature, mass flow as well as when using different pressure conditions. The main reason for this sensitivity is believed to be found in the HEATER-component, which is used to model the preheaters shell side. This also poses questions concerning how the code handles the condensation in the HEATER-component, where film condensation and forced convection should exist.

    Further investigation and development are therefore required before the model can be implemented in the context of more complex flow set-ups. Some of the more direct changes that are proposed would be to lowering the valves on the HEATER-component and a complete investigation around the physical conditions for the preheaters is needed to be performed. 

  • 188.
    Melin, Björn
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Utvärdering av urban vindkraft2012Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    NCC has started a project in collaboration with IVL Swedish Environmental Research Institute and Solna City. This is a research project about alternative energy production in the urban environment. A wind turbine with a maximum power of 2.5 kW was installed on the NCC's headquarters in Stockholm in mid-February 2011. IVL's role in the project is to develop a meteorological model where wind speeds, according to nearby obstacles and different heights, are presented. The purpose of this thesis is to conduct a technical evaluation of the wind turbine. Are the promises the supplier gave accurate? Is urban wind power profitable or what conditions are required for it to be? Do you need to measure wind speed on every location or can you use IVLs model or data from nearby monitoring stations? Do NCCs competitors work with similar projects in energy- and environment development? These questions form the base of this report.

    In 2009 a weather station was installed on the roof of NCCs headquarters and those measurements are used in the calculations. Wind speed measurements equal to one third of a year was available and with the assumption that the wind speed is the same over the year, the frequency distribution with the number of hours on the y-axis and wind speed on the x-axis could be made. Integrating the frequency distribution with the power curve for the plant makes it possible to calculate annual production. The turbine has been operational during April and May 2011 and theoretical calculations of the production have also been made for this period. Wind speeds from SMHI’s weather station at Bromma Airport and IVLs model has been compared with the measurements made on the property to investigate its use in future projects. A PEST and SWOT analysis has been made to obtain the preconditions for urban wind power. The competitor analysis shows what other companies are focused on in energy and environment development.

    In 2009, the plant should have delivered 627 kWh with an average annual wind of 3 m / s. The economic calculations in this report show that a production of 12,000 kWh per year is needed for the investment to become profitable during the plant life time. Average annual wind speeds of more than 8 m / s is required for this to be possible. During April and May 2011 the plant theoretically produced 47 kWh. Actual production is unknown at this point. SMHI's data differ too much to serve as a basis for future decisions but IVLs model can be an interesting tool. It is a necessity to continue working with energy and environment issues from a competitive perspective since the three largest competitors all have projects in various fields. Factors such as higher electricity prices, subsidies and better wind conditions could make investments profitable in the future.

  • 189.
    Melin, Tobias
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Energikartläggning av ett 1970-tals lägenhetshus på Skarpövägen i Nacka kommun: Simulering av energibesparande åtgärder i ”IDA Indoor Climate and Energy”2014Independent thesis Basic level (university diploma), 180 HE creditsStudent thesis
    Abstract [en]

    This study has been carried out in the spring of 2014 on behalf of PQR Consult AB in Stockholm. The aim of the study has been to analyse the energy usage of the building Skarpövägen 1 in order to explore the possibilites of saving energy by using appropriate equipment. These possible solutions have been simulated by using the programe IDA Indoor Climate and Energy, combined with a life cycle cost analysis. The laundry building, Skarövägen 23, has also been analysed due to its high amount of energy usage. The result of the energy analysis showed that the energy usage was much higher than the energy declaration. The energy usage of Skarpövägen 1 was 193 kWh/m2, which is 25 % higher than the energy declaration of 155 kWh/m2. Based on the energy saving actions, the most profitable investment would be to install heat recycling that would save 47470 kWh district heating per year with a pay-back time of 14 years. The results for the laundry building showed that there is a possibility to save up to 75% of the electricity usage by replacing certain equipment that is dependent on a high amount of energy. Throughout the whole analysis it has been clear that the energy usage in the buildings are higher than necessary. However, the energy saving actions have shown that there are ways to reduce the usage in the buildings. Some changes are simple to make while others would take longer, with varied pay-back time. In the long run those changes are vital for a sustainable reduction of energy usage.  

  • 190.
    Mengelian, Mahdieh
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nyckeltal för framtida fjärrvärmeutbyggnad: Nyckeltal för framtida bebyggelse som planeringsunderlag för fjärrvärmeutbyggnad samt uppföljning av verkligt utfall vs beräknat för ny bebyggelse.2014Independent thesis Basic level (university diploma), 180 HE creditsStudent thesis
  • 191.
    Mirghaemi Ghahani, Sara
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Energibalans Dåva Kraftvärmeverk2013Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
  • 192.
    Moberg, Désirée
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Transmission alternatives for grid connection of large offshore wind farms at large distance2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the great possibility of offshore wind power that can be installed in the world seas, offshore wind power is starting to get and important source of energy. The growing sizes of wind turbines and a growing distance to land, makes the choice of transmission alternative to a more important factor. The profitability of the transmission solution is affected by many parameters, like investment cost and power losses, but also by parameters like operation & maintenance and lead time of the system.

    The study is based on a planned wind farm with a rated power of 1 200 MW and at a distance of 125 km to the connection point. Four models have been made for the transmission network with the technology of HVAC, HVDC and a hybrid of both. The simulation program used is EeFarm II, which has an interface in Matlab and Simulink. The four solutions have been compared technically, with difficulties and advantages pointed out and also economically, with the help of LCOE, NPV and IRR. Costs, power losses and availability of the wind turbines and intra array network are not included in the study.

    The result of the simulations implies that the HVAC solution is the most profitable with the lowest Levelized Cost of Energy and highest Net Price Value and Internal Rate of Return. The values are 25.11 €/MWh, 387.60 M€ and 15.32 % respectively. A HVDC model with just one offshore converter station, has a LCOE close to the HVAC solution, but with a more noticeable difference in NPV and IRR (25.71 €/MWh, 300.76 M€ and 14.84 % respectively).

    A sensitivity analysis has been done, where seven different parameters have been changed for analysing their impact on the economic result. The largest impact made was by a change in investment cost and lead times. The results imply that with a structure of the transmission network as for the models, and with similar input data, the break point where a HVDC solution is more profitable than a HVAC solution is not yet passed at a distance of 125 km from the connection point. With an evolving technology in the field of HVDC, a shorter lead time and lower investment cost could mean that a HVDC solution would be more profitable at this distance. Difficulties for a HVAC solution with more cable required, like bigger land usage and cable manufacturing as a bottle neck, could make an important factor tough while making a decision.

  • 193. Muhammad, Yaseen
    et al.
    Rahman, Ata Ur
    Rashid, Haroon Ur
    Sahibzada, Maria
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Subhan, Sidra
    Tong, Zhangfa
    Hydrodesulfurization of dibenzothiophene using Pd-promoted Co–Mo/Al2O3 and Ni–Mo/Al2O3 catalysts coupled with ionic liquids at ambient operating conditions2019In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 9, no 18, p. 10371-10385Article in journal (Refereed)
    Abstract [en]

    Sulfur compounds in fuel oils are a major source of atmospheric pollution. This study is focused on the hydrodesulfurization (HDS) of dibenzothiophene (DBT) via the coupled application of 0.5 wt% Pd-loaded Co–Mo/Al2O3 and Ni–Mo/Al2O3 catalysts with ionic liquids (ILs) at ambient temperature (120 °C) and pressure (1 MPa H2). The enhanced HDS activity of the solid catalysts coupled with [BMIM]BF4, [(CH3)4N]Cl, [EMIM]AlCl4, and [(n-C8H17)(C4H9)3P]Br was credited to the synergism between hydrogenation by the former and extractive desulfurization and better H2 transport by the latter, which was confirmed by DFT simulation. The Pd-loaded catalysts ranked highest by activity i.e. Pd–Ni–Mo/Al2O3 > Pd–Co–Mo/Al2O3 > Ni–Mo/Al2O3 > Co–Mo/Al2O3. With mild experimental conditions of 1 MPa H2 pressure and 120 °C temperature and an oil : IL ratio of 10 : 3.3, DBT conversion was enhanced from 21% (by blank Ni–Mo/Al2O3) to 70% by Pd–Ni–Mo/Al2O3 coupled with [(n-C8H17)(C4H9)3P]Br. The interaction of polarizable delocalized bonds (in DBT) and van der Waals forces influenced the higher solubility in ILs and hence led to higher DBT conversion. The IL was recycled four times with minimal loss of activity. Fresh and spent catalysts were characterized by FESEM, ICP-MS, EDX, XRD, XPS and BET surface area techniques. GC-MS analysis revealed biphenyl as the major HDS product. This study presents a considerable advance to the classical HDS processes in terms of mild operating conditions, cost-effectiveness, and simplified mechanization, and hence can be envisaged as an alternative approach for fuel oil processing.

  • 194.
    Mwaba, MG
    et al.
    Carleton University, Ottawa, Canada.
    Golriz, Mohammad R
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Gu, J
    Carleton University, Ottawa, Canada.
    A semi-empirical correlation for crystallization fouling on heat exchange surfaces2006In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 26, no 4, p. 440-447Article in journal (Refereed)
    Abstract [en]

    Crystallization fouling experiments are reported in this paper. In general the results show four distinct time regions: a region where the fouling thermal resistance is zero, a region where the fouling thermal resistance is negative, a region where the fouling resistance increases steadily and a region where the fouling thermal resistance remains constant. Each of these regions can be matched with different development phases in the crystallization fouling process: nucleation phase (regions 1 and 2), growth phase and asymptotic phase. Overall the fouling curves exhibit an S-curve, characteristic of the logistic curve. A new correlation based on the solution of the logistic equation is formulated. The correlation parameters are evaluated and related to the crystallization parameters. The results of this work can find application in predicting the evolution of the fouling scale layer in heat exchangers that are in operation. The predictions can assist heat exchanger operators to plan cleaning schedules.

  • 195.
    Mäki, Jonatan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Energieffektivisering av "kontorslimpan": Energianalys med förslag till energieffektiviserande åtgärder2018Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The housing and service sector accounts for close to 40 % of Sweden's total energy use. In this sector, households and premises account for about 90 %. There are great potential for savings in this sector through energy efficiency.The purpose is to develop proposals for measures that reduce the energy use of the building in a cost-effective manner.The energy calculation program BV2 has been used to build a model of the building. The energy use of the simulated model is compared to the buildings measured values of energy use to see how well the model represents the building in terms of energy use.When these are in agreement, different energy efficiency measures are investigated. Simulations are performed for measures such as installation of heat exchanger, additional insulation of the attic and replace of windows etc.Of the measures investigated, installation of rotary heat exchangers has the shortest pay-back time of approximately 3 years, liquid-coupled heat exchangers get higher with a repayment period of 3,5 - 4 years. Additional insulation of wind bellows has a repayment period of around 5,5 to 6,5 years at a thickness of 350 mm. This measure, after installing heat exchanger, is the most profitable and is also relatively easy to perform.Based on these simulated measures, a package of measures has been developed and investigated using Belok's internal rate method. The result for the entire package of measures provides an internal rate of 18,7 % and a pay-backperiod of 5 years. This exceeds the 7 % yield requirement with a significant margin.

  • 196. Nazelius, Ida-Linn
    et al.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Rebbling, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Boman, Christoffer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Öhman, Marcus
    Fuel indices for estimation of slagging of phosphorus-poor biomass in fixed bed combustion2017In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 31, no 1, p. 904-915Article in journal (Refereed)
    Abstract [en]

    The market for solid biofuels will grow rapidly during the coming years, and there will be a great demand for raw materials. This will force the existing fuel base to also cover wooden materials of lower qualities as well as agricultural raw materials and residues, which often show unfavorable ash-melting temperatures. This may lead to combustion-related problems. Thus, for the utilization of lower quality fuels, it is important to be able to predict potential fuel ash-related problems such as slagging. In light of this, the first objective of the present paper was to evaluate the applicability of previously defined indices for slagging of biomass fuels (phosphorus-poor) in fixed bed combustion. The evaluation showed that none of the previously suggested indices in the literature are suitable for qualitative (nor quantitative) prediction of slagging during fixed bed combustion of P-poor biomass fuels. Hence, a second objective was to develop improved novel fuel indices that can be applied to estimate the slagging of phosphorus-poor biomass in fixed bed combustion. The novel fuel indices give a qualitative prediction of the slagging tendency in biomass fixed bed combustion but still needs additional work to further extend the compositional range as well as to fine tune the indices' boundaries.

  • 197.
    Nilsson, Alexander
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    A new energy strategiy for controlling heating system in existing buildings: Investigation in IDA ICE simulation environment2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
  • 198.
    Nilsson, Erik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Förbättrad utomhusbelysning vid Skebos fastigheter: En energieffektivisering av utomhusbelysningen i bostadsområden genom ett byte till LED-armaturer2014Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Throughout the last years, developments of energy efficiency regarding the housing sector have in general kept a steady pace with modern technology. However this could not be said for the field of outdoor lighting, where the possibilities of further energy savings still is evident. One action which intends to decrease the energy use of outdoor lighting systems have been issued by the European Commission. This act of legislation have banned future market introduction of high-pressure mercury vapor lamps (HPM), which represents a relatively large proportion of Swedish outdoor lighting. This, in combination with the pure economical gain of energy efficiency, should be incentive enough to change the wasteful situation that outdoor lighting currently holds. In addition to the choice of the lighting source, other factors like badly designed luminaires and over-dimensioned facilities are other factors that should be taken into consideration while preparing to minimize the waste of electrical energy.

    The outdoor lighting system for the municipally owned company Skelleftebostäder AB is no exception to the general need of efficiency. This project have investigated the consequences of adapting suitable LED-lighting instead of the current HPM-based system. The assignment included the choice of specific fixtures, and to clarify the reasoning behind the choice. To even start this process it was necessary to acquaint oneself with the terminology in the science of light and lighting, as well as studying previous projects with similar objectives. The project as such was initiated by examining 27 housing areas where the number of luminaires, as well as the corresponding power consumption where inventoried. This data where transformed into an equation which shows the relationship between lettable area (which is known for all housing areas) and installed power for each housing area, where the percentage of installed power per type of luminaire was assumed to be constant. Thus the total amount of luminaires for each type could be approximated.

    Based on the knowledge of the studies, together with the outcome of the inventory, four types of luminaire’s where decided to replace the current ones, to different extents. This results in the life cycle cost analysis which compared the value of keeping the existing lighting system to the value of changing it to LED under a 12 year period of time. The result shows that it is roughly 1,2 Mkr more profitable to change the luminaires in the 27 areas that where inventoried, and about 5 Mkr more profitable to make the change in the areas where the use of power where approximated.

  • 199.
    Nilsson, Jenny Elisabet
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Elproduktion ur låggradig värme: Tillämpningsmöjligheter vid Skellefteå Kraft ABs kraftvärmeverk Skogsbacka i Lycksele2013Independent thesis Basic level (university diploma), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    In a bio-fuelled combined heat and power plant, a lot of energy is lost in the outgoing fumes. By condensing the moist in the fumes, a lot of this energy can be recovered. At the plant Skogsbacka in Lycksele, investments in technology to do this is being considered. The purpose of this study is to evaluate the potential for using the recovered energy at Skogsbacka for generation of electricity. Different technologies are available for the generation of electricity from low grade heat. This study looks into "Powerbox" and "FlexiGen", two machines working according to the Organic Rankine Cycle, and C3, a newly developed technology that uses a chemical reaction to split the working media into different components. Ways to integrate the machines with the existing system are discussed, and the resulting electricity produced is calculated, and the influence on the rest of the system is considered. It is concluded that the possible economical winnings are very small.

  • 200.
    Nilsson, Ola
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Driftoptimering av torkmaskin: Driftoptimering av torkmaskin 3 vid Billerudkorsnäs Karlsborg AB2013Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
1234567 151 - 200 of 363
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf