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  • 1.
    Abolghasemi Moghaddam, Saman
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science.
    The effects of low-emissivity window films on thermal comfort and energy performance of a historic stone building in cold climate: computer simulations with "IDA ICE"2019Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Low-emissivity (low-E) window films are designed to improve the energy performance of windows and prevent indoor overheating by solar radiation. These films can be applied to different types of glazing units without the need for changing the whole window. This characteristic offers the possibility to improve the energy performance of the window of old and historic buildings for which preservation regulations say windows should remain more or less unchanged. This research aims to figure out to what extent a low-E window film can improve thermal comfort and energy performance of an old three-storey historic stone building in the cold climate of Mid-Sweden. In this research, first, with help of the simulation software “IDA ICE”, the entire building was modelled without window films in a one-year simulation. Second step was to add the low-E window films (3M Thinsulate Climate Control 75 (CC75)) to all the windows and repeat the simulation. Comparison between the results of the two cases revealed an improvement in energy use reduction as well as the thermal comfort when applying the films. For the application of the window films, a cost analysis using payback method was carried out which showed a long- time payback period. Although an investment with a long-time payback period is considered as a disadvantage, for historic buildings with very strict retrofit regulations specially when it comes to the building’s facades, application of the low-emissivity window films for better energy performance and thermal comfort is among the recommendable measures, but not necessarily the best.

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  • 2.
    Alcoverro Colom, Pau
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    A new energy model for the Lakshadweep islands: Change from a diesel-based model to a hybrid model with renewable energy systems considering the ecological fragility of the islands2019Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
  • 3.
    Aljaberi, Saif
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science.
    Majeed, Aram
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science.
    Energisimulering i modulhus: Fallstudie för uppskattning av energiprestanda och därefter energieffektivisera enligt passivhusstandaren2019Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Abstract

    The Building sector is today an important sector in our society, which means that more people move from the urban area to the big cities, which in turn increases building production. The building and service sector is the largest energy waste in Sweden and internationally, which is about 40% of Sweden's total energy use and 60% of that energy goes to heating. The EU Directive Energy Performance of Buildings Directive (EPBD), implemented the concept of near zero-energy houses, which comes into full force in 2020, which means that all newly-built buildings must be energy-efficient with better energy performance than todays buildings. This is in connection with the need of houses/buildings and rental costs continuing to increase. For this reason, Ljusbo Hyreshus AB has invented a solution that includes both climatesmart rental apartments and cheap rental costs, which has attracted more than 20 communes (kommuner in Sweden) to offer land for these apartments. The purpose of this thesis is to find out the energy performance of one of Ljusbo Hyreshus AB's prototype module houses. Furthermore, improvement proposals would be developed to make the module house more energy efficient. The prototype house consisted of a single-storey modularhouse that stay in Söderhamn, which has been chosen in this thesis for further investigations. The house had a total area of 45 m2 and consisted of 3 rooms and kitchen. In this case study, the energy performance has been developed using analysis methods in the form of hand calculations and the energy signature method. Subsequently, the result of the analysis would be validated and would form the basis for later identification of various energy efficiency measures that contributed to the reduction of energy performance in the house and thereby achieved the passive house standard. The result shows that the modularhouse does not fullfil BBR's requirements at present, because the house misses important components which is important for energy performance. For this reason, improvement proposals, specifically regarding the climate shell, on energy efficiency measures have been developed in this report. With the help of these energy efficiency measures, which mainly consist of additional insulation and energy-efficient windows and with an energy-efficient ventilation system with heat recovery (FTX) and an installed air-water heat pump, the passive house standard has been possible to achieve. Future measures, such as the installation of solar cells, have also been examined in the report. This is due to converting the building from a passive house to a plus energy house.

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    Energisimulering i modulhus
  • 4.
    Al-sabti, Merna
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science.
    Lönsamhet och affärsmodell för en biogasanläggning som drivs av lantbrukare2019Independent thesis Basic level (university diploma), 180 HE creditsStudent thesis
    Abstract [en]

    Biogas production has environmental and social advantages for farmers, the target group of this study, but there are obstacles. Profitability issues can be resolved by, for example, applying business models. The purpose of the study was to investigate which business model can be applied by an agricultural biogas plant and to analyze the profitability of the company through assessment of key figures and DuPont models. An agricultural biogas plant was selected and various studies on the profitability and business models of agricultural biogas plants were used as a basis for comparing the example plant with previous research. Interviews were conducted with a partner in the biogas company. In order to determine the profitability of the company, calculations of key figures and DuPont models were carried out for the years 2017 and 2018. The study identified various success factors for the company, regarding collaboration, entrepreneurial characteristics, long-term perspective and the relationship to the market. The results show that even if the company has lacked a structured business model, their work is following recommendations given by published business models. The analysis shows that the company has good profitability, but profitability is difficult to evaluate on the long term, since data for several years were not available in the yearly report of the company. The conclusions from the present study are that the company is profitable, however, profitability risks are present, which demonstrate that the company cannot lower its prices due to competition, and they require knowledge about costs to maintain or increase profit over time. The present study proposes that the company utilizes a formal business model, which needs to include financial analysis for long-term and maintained profitability. The business model of the company could be used as a source of inspiration to other farmers, as long as it will be expanded to include financial analysis.

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  • 5.
    Ameen, Arman
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Cehlin, Mathias
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Reducing energy usage in multi-family housing2019In: 2019 9th International Conference on Future Environment and Energy 9–11 January 2019, Osaka, Japan, Institute of Physics Publishing (IOPP), 2019, Vol. 257, article id 012030Conference paper (Refereed)
    Abstract [en]

    The energy usage in residential sector have been around 22% of the total energy use in the world and increasing due to the population growth and higher living standards. The energy sources for this are made up primarily of non-renewable energy resources which generates a large amount of global greenhouse gases. A lot of countries have implemented various regulations and rules to reduce the energy usage in buildings and promoting the use of renewable energy technologies. This paper presents a parametric study of a typical multi-family building in its pre-design stage. The climate location used is Sweden (Gothenburg) and Japan (Osaka). The aim of the study is to compare various configurations and to examine how they affect the energy use. The most interesting configurations are the use of heat pump and solar cells. Other configurations that are examined are infiltration levels, pressure coefficients, wind impact, ventilation with heat recovery, ventilation scheduling, building orientation and finally changing U-values in the building material. Results of this study show that the energy saving, by utilizing a heat pump and solar panels, can reduce the total energy use by 34.9% for Gothenburg and 32% for Osaka. The results also show that the difference in total energy use between the two cities reduce substantially (3% difference) when utilizing a heat pump in combination with solar panels.

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  • 6.
    Ameen, Arman
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Cehlin, Mathias
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Larsson, Ulf
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Karimipanah, Taghi
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Experimental Investigation of Ventilation Performance of Different Air Distribution Systems in an Office Environment: Heating Mode2019In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, no 10, article id 1835Article in journal (Refereed)
    Abstract [en]

    A vital requirement for all-air ventilation systems are their functionality to operate both in cooling and heating mode. This article experimentally investigates two newly designed air distribution systems, corner impinging jet (CIJV) and hybrid displacement ventilation (HDV) in comparison against a mixing type air distribution system. These three different systems are examined and compared to one another to evaluate their performance based on local thermal comfort and ventilation effectiveness when operating in heating mode. The evaluated test room is an office environment with two workstations. One of the office walls, which has three windows, faces a cold climate chamber. The results show that CIJV and HDV perform similar to a mixing ventilation in terms of ventilation effectiveness close to the workstations. As for local thermal comfort evaluation, the results show a small advantage for CIJV in the occupied zone. Comparing C2-CIJV to C2-CMV the average draught rate (DR) in the occupied zone is 0.3% for C2-CIJV and 5.3% for C2-CMV with the highest difference reaching as high as 10% at the height of 1.7 m. The results indicate that these systems can perform as well as mixing ventilation when used in offices that require moderate heating. The results also show that downdraught from the windows greatly impacts on the overall airflow and temperature pattern in the room.

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  • 7.
    Ameen, Arman
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Cehlin, Mathias
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Larsson, Ulf
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Karimipanah, Taghi
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Experimental investigation of ventilation performance of different air distribution systems in an office environment – cooling mode2019In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, no 7, article id 1354Article in journal (Refereed)
    Abstract [en]

    The performance of a newly designed corner impinging jet air distribution method with an equilateral triangle cross section was evaluated experimentally and compared to that of two more traditional methods (mixing and displacement ventilation). At nine evenly chosen positions with four standard vertical points, air velocity, turbulence intensity, temperature, and tracer gas decay measurements were conducted for all systems. The results show that the new method behaves as a displacement ventilation system, with high air change effectiveness and stratified flow pattern and temperature field. Both local air change effectiveness and air exchange effectiveness of the corner impinging jet showed high quality and promising results, which is a good indicator of ventilation effectiveness. The results also indicate that there is a possibility to slightly lower the airflow rates for the new air distribution system, while still meeting the requirements for thermal comfort and indoor air quality, thereby reducing fan energy usage. The draught rate was also lower for corner impinging jet compared to the other tested air distribution methods. The findings of this research show that the corner impinging jet method can be used for office ventilation.

  • 8.
    Ameen, Arman
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Choonya, Gasper
    Cehlin, Mathias
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Experimental Evaluation of the Ventilation Effectiveness of Corner Stratum Ventilation in an Office Environment2019In: Buildings, ISSN 2075-5309, E-ISSN 2075-5309, Vol. 9, no 7, article id 169Article in journal (Refereed)
    Abstract [en]

    An experimental study was conducted in a room resembling an office in a laboratory environment. The study involved investigating the ability of corner-placed stratum ventilation in order to evaluate the ventilation’s effectiveness and local thermal comfort. At fixed positions, the air temperature, air velocity, turbulence intensity, and tracer gas decay measurements were carried out. The results show that corner-placed stratum ventilation behaves very similar to a mixing ventilation system when considering air change effectiveness. The performance of the system was better at lower supply air flow rates for heat removal effectiveness. For the heating cases, the draught rates were all very low, with the maximum measured value of 12%. However, for the cooling cases, the maximum draught rate was 20% and occurred at ankle level in the middle of the room.

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  • 9.
    Andersson, Emelie
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Aziz, Shniar
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    En jämförelse mellan gröna-, metall- och gråa tak för ett oisolerat parkeringshus utifrån dess olika temperaturer och dagvattenhantering2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Since climate change increases and changes constantly, it contributes to higher average temperatures, ice melting and has a great impact on our ecosystem. This will then lead to a warmer climate, which means increased precipitation and milder winters. One of the reasons to climate change is urbanization, meaning people moving to the cities. To succeed in changing the climate, international cooperation and common goals are required. At the northern part of Brynäs, in the municipality of Gävle, work is currently in progress around the area where the factory of Läkerol was once standing. The area continues to be rebuilt and the outcome will eventually be called Godisfabriken. There, amongst other, a car park will be built for the newly built homes. The aim of this study is to compare metal roofs, grey concrete roofs and green roofs within the two aspects of stormwater management and temperature. Then analyse which alternative of these three roofs would be most advantageous for the car park of Godisfabriken.

     

    The focused roofs are green, metal and concrete. A green roof is when it's completely or partly covered by a layer of vegetation and metal roofs are different sheet roofs with steel and aluminium-zinc. Grey roofs are made of concrete which works as both floor and ceiling. A building's roof affects which air temperature the surroundings has with its slope, vegetation and surrounding buildings. Another problem with urbanization and a warmer climate is stormwater management, which means rain and melted snow from roofs, parking areas and other hard surfaces.

     

    The method includes a literature study and calculations. The literature study gave research on temperature for all roofs as well as stormwater management for green roofs. Calculations were made for stormwater management and temperature with its flow, absorption, reflectance and heat transfer.

     

    The literature study and the calculations showed that green roofs have a high SRI value of 80 while the remaining roof is at around 40. The higher SRI, the lower surface temperatures on the material. This is proven in both methods when green roofs according to the literature study received a maximum surface temperature of 38 °C and 48 °C. According to the literature study green roofs can preserve more than 50 % of the rainwater. They also had a water flow rate of 1.97 l/s, which is less than half of what the metal roof got in the calculations. Since green roofs had both low air and surface temperatures, as well as longer drainage times and most absorbed water, green roofs are a more suitable choice than metal and grey concrete.

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  • 10.
    Andersson, Harald
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Numerical and experimental study of confluent jets supply device with variable airflow2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In recent years, application of confluent jets for design of ventilation supply devices has been studied. Similarly, numerus studies have been made on the potential and application of variable air volume (VAV) in order to reduce the energy demand of ventilation systems. This study investigates the combination of supply devices based on confluent jets and VAV, both in terms of the nearfield flow behavior of the device and the impact on thermal comfort, indoor air quality and energy efficiency on a classroom-level space when the airflow rate is varied.

    The method used in this study is an experimental field study where the confluent jets-based supply devices were compared to the previously installed displacement ventilation. The field study evaluated the energy efficiency, thermal comfort and indoor air quality of the two systems. In the case of the confluent jets supply devices, airflow rate was varied in order to see what impact the variation had on the performance of the system for each airflow rate. Furthermore, the confluent jets supply devices were investigated both experimentally and numerically in a well insulated test room to get high resolution data on the particular flow characteristics for this type of supply device when the airflow rate is varied. The results from the field study show nearly uniform distribution of the local mean age of air in the occupied zone, even in the cases of relatively low airflow rates. The airflow rates have no significant effect on the degree of mixing. The thermal comfort in the classroom was increased when the airflow rate was adapted to the heat load compared to the displacement system. The results lead to the conclusion that the combination of supply devices based on confluent jets can reduce energy usage in the school while maintaining indoor air quality and increasing the thermal comfort in the occupied zone.

    The results from the experimental and numerical study show that the flow pattern and velocity in each nozzle is directly dependent on the total airflow rate. However, the flow pattern does not vary between the three different airflow rates. The numerical investigation shows that velocity profiles for each nozzle have the same pattern regardless of the airflow rate, but the magnitude of the velocity profile increases as the airflow increases. Thus, a supply device of this kind could be used for variable air volume and produce confluent jets for different airflow rates.

    The results from both studies show that the airflow rate does not affect the distribution of the airflow on both near-field and room level. The distribution of air is nearly uniform in the case of the near-field results and the room-level measurement shows a completely uniform degree of mixing and air quality in the occupied zone for each airflow rate. This means that there is potential for combining these two schemes for designing air distribution systems with high energy efficiency and high thermal comfort and indoor air quality.

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  • 11.
    Andersson, Martin
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Jonsson, Andreas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Nyström, Niklas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Insvällning av olimmade och limmade trädymlingar2019Independent thesis Basic level (degree of Bachelor), 180 HE creditsStudent thesis
    Abstract [en]

    Wood is a renewable material, unlike many other building materials. The amount of wood used in the construction industry can be increased by using wooden dowels as a substitute for screws and nails. Screws and nails are made of metals, which are non-renewable materials. The manufacturing process of metal-based materials is more energy consuming than it is for wooden materials and therefore it has a greater impact on our global environment.The purpose of this study was to investigate the adhesion capacity of wooden dowel-joints, non-glued and glued made out of beech and pine. The attachment of the non-glued wooden dowels was achieved by swelling of the wood. Swelling was achieved by first drying the wooden dowels in an oven and then letting them acclimatize with the surrounding materials and the relative air humidity. The adhesion capacity of the wooden dowels should be able to compete with the withdrawal strength of nails to be practically useful.Tensile strength tests have been carried out in the laboratory in house 45 at the University of Gavle to determine the adhesion capacity of wooden dowel-joints. The tensile strength tests were performed with a Shimadzu AG-X machine. The results of the tests have been compared with the theoretical withdrawal strength for nails. Characteristic strength values have also been calculated from the tensile strength test results for the wooden dowels.The results of the study shows that only the glued wooden dowels can compete with the withdrawal strength of nails. Glued wooden dowels can therefore be a substitute for screws and nails. The calculated characteristic values for glued beech-dowels and glued pine-dowels are 5,2 kN respectively 4,3 kN.

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    Insvällning av olimmade och limmade trädymlinga r
  • 12.
    Archakis, Viktor
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    The Design of a Passive House2018Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    About 25 % of the total buildings in the European Union have been categorized as ”old buildings”. Followed the recent strickt rules for carbon emissions reduction, each house has to approximetely cut 20 % of CO2 by 2020. Countries like England, have taken the issue very seriously and planning to reduce the carbon emissions by 30 % until the end of 2020 and by an extra 80 % by 2050 (Francis Moran, 2014). The aim of the report is to present how a traditional house can be retroffited into a passive house and also to identify the key points that every passive house should have. For the purpose of the project an avtual house, based in Gävle, was provided and all the simulations are based on actual data. The initial design of the house which was used for the simulation and the 3D design, was provided by the house owner. The building was built in 1953, information regarding the current insulation of the house was provided by the owner as well. For the simulations and the 3D design a software know as IDA ICE was used, license and access to the software were given by the University of Gävle. The report simulates the current house and compares the results with two possible scenarios that are reducing the energy demand of the house. Furthermore, the possible ways and tools that could be used to reduce the energy demand of the house and cost estimation for the retrofitting is available in the paper.The first simulations were occured on the actual house, the first retrofitting package introduces new simulations based on new insulation materials, like wood and cement, that are placed mainly on the roof and on the outer walls. Also, the thickness have changed, thus the new insulations are thicker.Moreover, the second and final retrofitting package, introduces an HVAC system, which is a standard system. The aim is to achieve further energy demand reductions and prove that simple and basic changes can improve the quality of living and reduce CO2 emissions.After the completition of the first analysis, a reduction equal to 60 % and after the addition of the HVAC a further 20 % reduction achieved.

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  • 13.
    Arfan, Muhammad
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science. 202100-2890.
    Biogas Value Chain in Gävleborg: Feedstock, Production and Use2019Report (Other academic)
    Abstract [en]

    This report aims to identify the current status and future opportunities for biogas as an alternative fuel for road transport in the Gävleborg region. The regional actors along the value chain are mapped by their role in feedstock supply, production and use of the biogas. Mapping and analysis of biogas development generally in Sweden and particularly in the Gävleborg region has been conducted primarily through literature, national and regional statistics and through interviews with the regional actors. About 15 companies were reached through emails and phone calls during the interview process.

    In 2017, about 3.5-4.0 million Nm3 of raw biogas (50-65% CH4) was produced in the region of which 3.6 GWh was upgraded. The region has two plants with upgrading facilities, one in Forsbacka, which produces gas mainly from food waste and Duvbacken, the wastewater treatment plant in Gävle. The gas produced at these two big facilities is upgraded and mostly used as transport fuel in the region, and for the industry. Gas produced from other sources is either used for heat and electricity production or flared to avoid methane emissions to the environment. The region has 14 buses and more than 500 other vehicles running on biogas. The gas infrastructure is not well developed in the region except for two filling stations situated in Gävle and Forsbacka. However, some developments on building biogas infrastructure for transport are in process.

    Analysis of interviews with actors and literature studies revealed that the region has much more feedstock for biogas production than used in the currently installed capacity of biogas technologies. Many actors showed great interest in its use as transport fuel but had very serious concerns about its future scope. Lack of supporting infrastructure such as filling stations, very low market demand and regional long-term strategies on biogas as transport fuel are considered barriers in the sector´s further development in the region. The value chain actors need to work more closely to get the most out of this valuable resource. Additionally, future planning on biogas should also consider its other uses such as an energy source for manufacturing industry, shipping and as raw material for chemicals or intermediate products.

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  • 14.
    Bahrami, Alireza
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology. Islamic Azad University, Abadan, Iran.
    Heidari, Mahmood
    Islamic Azad University, Abadan, Iran.
    Dynamic analysis of steel eccentrically braced frames with shear link2020In: International Journal of Engineering Research and Technology, ISSN 0974-3154, Vol. 13, no 2, p. 233-239Article in journal (Refereed)
    Abstract [en]

    This paper offers the dynamic analysis of steel eccentrically braced frames (EBFs) with shear link under earthquake loads. The analysis was carried out using the finite element software ABAQUS. The verification of the EBF modelling was established by the comparison of the modelling result with that of the experimental test. Then, an EBF was designed with a shear link. Three different severe earthquake records of Tabas, Northridge, and Chi-Chi were selected for the analyses. Since the modelling accuracy was revealed, the method was utilised for modelling the developed EBF. The EBF was then analysed under the mentioned records. From the obtained results, the lateral displacements and energy dissipations of the frame and also shear link rotations were investigated. With regard to all the effects of the records as the lateral displacement and base shear of the frame and also the shear link rotation, it was found that the hierarchy of the records from their effects viewpoint on the EBF has been the Tabas, Chi-Chi, and Northridge earthquakes. In addition, the hierarchy of the energy dissipations of the records by the EBF has been the Tabas, ChiChi, and Northridge earthquakes, as well. Therefore, the developed EBF demonstrated a good performance in the energy dissipation of the earthquake records. 

  • 15.
    Bahrami, Alireza
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology. Islamic Azad University, Abadan, Iran.
    Matinrad, S.
    Islamic Azad University, Abadan, Iran.
    Resistance of blast-loaded steel and reinforced concrete beam-to-column connections2020In: International Journal of Engineering Research and Technology, ISSN 0974-3154, Vol. 13, no 1, p. 12-27Article in journal (Refereed)
    Abstract [en]

    Resistance of steel and reinforced concrete (RC) beam-to-column connections to blast loading is presented in this paper. The steel and RC connections are analysed nonlinearly using the finite element (FE) software ABAQUS. Comparisons of the obtained results from the connections modelling with those of the experimental tests reveal the modelling accuracy. Then, the ETABS software is utilised to design 4 buildings including 2 steel buildings with 5 and 9 storeys and 2 RC buildings with the same number of storeys. The components of the selected beam-to-column connections of the ground floor of the buildings are designed. Then, different parameters are considered for the nonlinear analyses of the steel and RC connections. The studied parameters for the steel connections are as the size of cross-section, bolts arrangement, and using stiffeners in the beam web of the connections, while the parameters for the RC connections are as the size of cross-section, stirrups space, and making beam non-prismatic in the beam-column connection region. It was found that increasing the cross-sectional sizes of the beams and columns of the steel and RC connections considerably enhances the resistance of the connections. In addition, change of the bolts arrangement in the steel connections and reducing the stirrups space in the RC connections significantly influence the resistance of the connections. However, using stiffeners in the beam web of the steel connections and making the beam non-prismatic in the region of the beam-column RC connections have no remarkable effect on the connections resistance. Failure modes of the connections are also evaluated. 

  • 16.
    Bahrami, Alireza
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology. Department of Civil Engineering, Abadan Branch, Islamic Azad University, Abadan, Iran.
    Matinrad, Sina
    Department of Civil Engineering, Abadan Branch, Islamic Azad University, Abadan, Iran.
    Blast effects on reinforced concrete connections2019In: International Journal of Scientific and Technology Research, ISSN 2277-8616, Vol. 8, no 11, p. 3604-3610Article in journal (Refereed)
    Abstract [en]

    This study is concerned with the blast effects on reinforced concrete (RC) connections. The RC connections are analysed nonlinearly. The analyses are conducted by applying the finite element software ABAQUS. The first step is to do the verification of the modelling. To achieve this goal, an experimental test performed on an RC connection is simulated utilising ABAQUS. Comparing the analysis result with the experimental test result establishes the modelling verification. In the second step, a 5-storey building is designed by the use of the ETABS software. A connection of the ground floor is selected for further analyses in ABAQUS. In the third step, the components of the selected connection are designed. Then, various variables are taken into account as the distance of the connection from the blast centre (2.5 m, 5 m, and 10 m) and the blast power (500 kg, 1000 kg, and 2000 kg TNT equivalent mass of explosive) for the further analyses of the connection. In the fourth step, the connection is analysed considering the variables. Finally, effects of these variables on the behaviour of the connection are investigated and discussed. Failure modes of the connections due to the blast loading are presented. © IJSTR 2019.

  • 17.
    Bahrami, Alireza
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology. Department of Civil Engineering, Abadan Branch, Islamic Azad University, Abadan, Iran.
    Matinrad, Sina
    Department of Civil Engineering, Abadan Branch, Islamic Azad University, Abadan, Iran.
    Response of steel beam-to-column bolted connections to blast loading2019In: International Journal of Recent Technology and Engineering, ISSN 2277-3878, Vol. 8, no 3, p. 3639-3648Article in journal (Refereed)
    Abstract [en]

    In this research, response of steel beam-to-column bolted connections to blast loading is investigated. Nonlinear analyses of the connections are performed using the finite element software ABAQUS. In order to demonstrate the accuracy of the finite element modelling, an experimental test of a steel beam-to-column bolted connection is modelled. Comparison of the obtained result from the modelling with that of the corresponding experimental test verifies the modelling. Then, a 5-storey steel building is designed using ETABS software from which a beam-to-column connection of the ground floor is selected for the nonlinear analysis in ABAQUS. Thereafter, the components of the selected connection are designed. Finally, the connection is nonlinearly analysed considering parameters as the distance from the blast centre (2.5 m, 5 m, and 10 m) and blast power (500 kg, 1000 kg, and 2000 kg TNT equivalent mass of explosive). Effects of these parameters on the response of the connection are evaluated. Failure modes of the connections are assessed, too.

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  • 18.
    Bahrami, Alireza
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Najarnasab, Mahdi
    Islamic Azad University, Abadan, Iran.
    Analysis of steel plate girders with elliptical web openings2020In: Journal of Engineering and Applied Sciences, ISSN 1819-6608, E-ISSN 1819-6608, Vol. 15, no 4, p. 556-563Article in journal (Refereed)
    Abstract [en]

    In this research work, steel plate girders (SPGs) having the web openings with the elliptical shape are analysed. The finite element ABAQUS software is applied. An experimentally tested SPG is used for the modelling verification. Then, the SPGs are developed. Three-dimensional (3D) finite element models of the SPGs are analysed nonlinearly considering various variables. The variables are adopted in order to deeply examine the performance of the SPGs using the finite element method. These variables include: 1) number of the openings, 2) arrangement of the openings, 3) using steel frame around the openings, 4) utilising diagonal steel stiffeners to connect the steel frame around the openings to the corners of the SPGs, and 5) thicknesses of the steel frame and the diagonal steel stiffeners. The obtained results are compared and discussed considering the effects of the variables. It is concluded that increasing the number of the openings has an adverse impact on the ultimate strength of the SPGs. The arrangement of the openings in the SPGs significantly affects their performance. The horizontal openings are superior to the vertical ones. Utilising the steel frame around the openings and/or the steel stiffeners improves the ultimate strength. Enhancing the thickness of the steel frame and/or stiffeners increases the ultimate strength. The assessment of the failure modes of the SPGs is also done. 

  • 19.
    Bahrami, Alireza
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Najarnasab, Mahdi
    Islamic Azad University, Abadan, Iran.
    Ultimate behaviour of perforated steel plate girders subjected to shear loading2020In: Open Construction & Building Technology Journal, ISSN 1874-8368, Vol. 14, p. 70-83Article in journal (Refereed)
    Abstract [en]

    Background:

    The Perforated Steel Plate Girders (PSPGs) are those Steel Plate Girders (SPGs) that have openings in their web. The PSPGs are significantstructural members to withstand bending mainly. The proper combination of steel plates is applied to fabricate the PSPGs. When the availablerolled steel profiles cannot carry the applied loads, the use of beams made of the steel plates is unavoidable.

    Objective:

    The present paper presents the ultimate behaviour of PSPGs subjected to shear loading.

    Methods:

    In order to carry out the study, the finite element method is used as a practical design tool for predicting the ultimate behaviour of the PSPGs undershear loading. Two experimentally tested PSPGs are selected to conduct the modelling accuracy using ABAQUS. All the features of the testedspecimens are considered in the modelling. The finite element modelling results are compared with the experimental tests results, which verify themodelling. Since the accuracy of the modelling is demonstrated, thereafter, the method is used for the nonlinear analysis of the developed PSPGshaving different circular and rectangular openings. Various parameters are adopted in the analysis to vastly evaluate their effects on the ultimatebehaviour of the PSPGs. The parameters include shape of the openings (circular and rectangular openings), number of the openings (2 and 4openings), arrangement of the openings (horizontal and vertical openings), using steel frame around the openings, utilising diagonal steel stiffenersto connect the steel frame to the corners of the PSPGs, and thicknesses (2 mm and 4 mm) of the steel frame and the diagonal steel stiffeners.

    Results:

    The obtained results from the nonlinear analysis of the PSPGs are summarised considering various parameters. The results are compared anddiscussed, taking into account the effects of the parameters on the ultimate behaviour of the PSPGs.

    Conclusion:

    The study highlights that the shape of the openings affects the behaviour of the PSPGs. Accordingly, circular openings are preferred comparedwith the rectangular ones. Also, as the number of the openings is increased, the ultimate capacity of the PSPGs is reduced. The behaviour of thePSPGs is considerably affected by the arrangement of the openings in which the horizontal openings have better performance than the verticalones. If the steel frame and/or the steel stiffeners are utilised, the ultimate capacity is enhanced. The ultimate capacity of the PSPGs is improved byincreasing the thickness of the steel frame and/or stiffeners. The failure modes of the PSPGs with circular and rectangular openings are indicatedand evaluated.

  • 20.
    Bahrami, Alireza
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Yavari, M
    Islamic Azad University, Abadan, Iran.
    Analysis of composite shear walls with a gap between reinforced concrete wall and steel frame2020In: Archives of Civil Engineering, ISSN 1230-2945, Vol. 66, no 1, p. 41-53Article in journal (Refereed)
    Abstract [en]

    In this research, nonlinear analysis of composite shear walls (CSWs) with a gap between reinforcedconcrete wall and steel frame is investigated under cyclic loading by the use of the finite element method (FEM)software ABAQUS. For the purpose of the verification, an experimental test is modelled and comparison of itsobtained result with that of the experimental test demonstrates an inconsiderable difference between them;therefore, the reasonable accuracy of the modelling is revealed. Then, effects of different parameters on thebehaviour of the CSWs are examined. Gap size between reinforced concrete wall and steel frame, reinforcementpercentage, steel sections of beams and columns, and existence of reinforced concrete wall are considered asparameters. It is concluded that change of the parameters affects the ultimate strength, ductility, and energydissipation of the system. A steel shear wall (SSW) is also modelled and compared with the CSWs. Buckling ofthe walls is presented as well.

  • 21.
    Bahrami, Alireza
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Yavari, Mojtaba
    Department of Civil Engineering, Abadan Branch, Islamic Azad University, Abadan, Iran.
    Hysteretic assessment of steel-concrete composite shear walls2019In: International Journal of Recent Technology and Engineering, ISSN 2277-3878, Vol. 8, no 2, p. 5640-5645Article in journal (Refereed)
    Abstract [en]

    This paper focuses on the hysteretic assessment of steel-concrete composite shear walls with reinforced concrete on one side of the steel plate. Finite element software ABAQUS is utilised to conduct this research. An experimental test on a composite shear wall is simulated to do the verification of the modelling. Then, modelling result is compared with the experimental test result which shows an insignificant difference between them and therefore uncovers the accuracy of the modelling. Thereafter, different parameters are considered to investigate their effects on the response of the walls. Thickness of reinforced concrete, steel plate thickness, and number of shear studs are studied as parameters. It is concluded that changing reinforced concrete thickness and number of shear studs do not considerably affect the ultimate load capacity, ductility, and energy dissipation of the walls. However, increasing the steel plate thickness enhances the ultimate load capacity, ductility, and energy dissipation. In addition, out-of-plane displacement of the walls is evaluated.

  • 22.
    Bahrami, Alireza
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology. Department of Civil Engineering, Abadan Branch, Islamic Azad University, Abadan, Iran.
    Yavari, Mojtaba
    Department of Civil Engineering, Abadan Branch, Islamic Azad University, Abadan, Iran.
    Performance of Steel Concrete Shear Walls with Two Sided Reinforced Concrete2019In: International Journal of Engineering and Technology Innovation, ISSN 2223-5329, E-ISSN 2226-809X, Vol. 9, no 3, p. 228-239Article in journal (Refereed)
    Abstract [en]

    Abstract

    This paper deals with the performance of Steel-Concrete Shear Walls (SCSWs) which have reinforced concrete on both sides of the steel plate subjected to cyclic loads. Finite element software ABAQUS is applied to analyze the SCSWs. Accuracy of the finite element modeling is verified by comparison of the theoretical results with those obtained experimentally. Then, various variables are studied in order to evaluate their effects on the performance of the SCSWs. These variables include thickness of concrete, steel plate thickness, number of bolts, gap size between reinforced concrete and steel frame, the percentage of reinforcement in reinforced concrete, and beam and column profiles of the steel frame. It is concluded that the change of the variables influences the ultimate load capacity, ductility, and energy dissipation of the SCSWs. Moreover, buckling of the walls is discussed.

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  • 23.
    Balciunas, Dominykas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Thermoeconomic analysis of LNG physical exergy use for electricity production in small-scale satellite regasification stations2019Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Liquefied natural gas (LNG) cold utilization in small scale regasification stations is a novel topic in the industry, while such systems have been proven feasible in large scale LNG facilities. Cold recovery and utilization in LNG regasification facilities would increase the thermodynamic efficiency and reduce cold pollution. The aim of the study is to analyze the possibility to apply industry-proven thermodynamic cycles in small scale satellite regasification stations for electricity production, taking the characteristics of a real-world regasification station project in Druskininkai, Lithuania for which useful cold utilization is not currently planned.

    Direct Expansion (DE) and Rankine (ORC) Cycles are analyzed together with cascading using Aspen Hysys software to find the optimal solution considering thermal and exergy efficiency as well as the payback period.

    Thermoeconomically feasible retrofit solutions of approximately 13% thermal efficiency and approximately 17% exergy efficiency showing payback periods of 5 to 10 years and 3.3 to 6 thousand euro additional capital expenditure (CAPEX) per net kW of power production are found.

    Increase in complexity of thermodynamic cycles is directly proportional to both increased thermodynamic efficiencies and capital costs and the study proves that there is a limit at which increase in thermodynamic efficiency of a cycle by cascading becomes economically infeasible. Future work is suggested to improve the accuracy of the results by rigorous design to evaluate pressure drops as well as improvements in economic analysis by utilizing the discounted cash flow methodology. Sensitivity analysis of LNG physical and chemical conditions as well as ambient air could be performed whereas changes in working fluid and better engineering of the part related to intial heat exchange could improve thermodynamic efficiencies. Alternative solutions with a higher temperature heat source are also suggested.

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  • 24.
    Barthel, Stephan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science. Stockholm University.
    Isendahl, Christian
    Göteborgs Universitet.
    Vis, Ben
    University of Kent, UK.
    Drescher, Axel
    University of Erlangen-Nuernberg, Germany.
    Evans, Dan
    Lancaster University, UK.
    van Timmeren, Arjan
    TU Delft, The Netherlands.
    Global urbanization and food production in direct competition for land: Leverage places to mitigate impacts on SDG2 and on the Earth System2019In: The Anthropocene Review, ISSN 2053-0196, Vol. 6, no 1-2, p. 71-97Article in journal (Refereed)
    Abstract [en]

    Global urbanization and food production are in direct competition for land. This paper carries outa critical review of how displacing crop production from urban and peri-urban land to other areas– because of issues related to soil quality – will demand a substantially larger proportion of theEarth’s terrestrial land surface than the surface area lost to urban encroachment. Such relationshipsmay trigger further distancing effects and unfair social-ecological teleconnections. It risks also settingin motion amplifying effects within the Earth System. In combination, such multiple stressors set thescene for food riots in cities of the Global South. Our review identifies viable leverage points on whichto act in order to navigate urban expansion away from fertile croplands. We first elaborate on thepolitical complexities in declaring urban and peri-urban lands with fertile soils as one global commons.We find that the combination of an advisory global policy aligned with regional policies enablingrobust common properties rights for bottom-up actors and movements in urban and peri-urbanagriculture (UPA) as multi-level leverage places to intervene. To substantiate the ability of aligningglobal advisory policy with regional planning, we review both past and contemporary examples whereempowering local social-ecological UPA practices and circular economies have had a stimulatingeffect on urban resilience and helped preserve, restore, and maintain urban lands with healthy soils.

  • 25.
    Bengtsson Asplin, Björn
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science.
    Norén, Tommy
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science.
    Fasadpanelens fuktskydd: Har droppnäsan någon betydelse?2020Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The moisture content of wooden façades changes over time due to external factors, for example the frequency of driving rain. Wooden façades can take damage from penetrating moisture and therefore should be protected so they do not lose their primary function of stopping snow and rain from getting inside the climate shell of the building. Science studies have shown that a fundamental protection from moisture can be created through surface treatment of the façade and choosing the right type of wood. Another known moisture protecting advice within the field of construction is to mitre the corners on the lower part of the façades (also known as dripping channel) but no studies could be found that confirmed that it actually effect the moisture content of the material. To investigate this a little further an irrigation model was created which the purpose to find out the significance of the dripping channel for the moisture protection of the façades. Hypothesis 1 was that façades with dripping channels generally absorb less moisture then façades with an end grain without a mitred corner, regardless of treatment. This was based on the assumption that a more narrow angle on the end grain causes the water from the water film to drip of the façades instead of getting trapped on the surface, and be absorbed by capillary forces. Hypothesis 2 was that treated façades with dripping channels absorb less moisture then treated façades without dripping channels, based on the attempt to mimic the advice regarding mitre and surface treatment, where the surface treatment is used for the purpose of reducing capillary uptake.

    The experiment consisted of three testing riggs with vertical wooden façades which were sorted by the angle of the end grain and surface treatment. The results from the three testing riggs could then be compared to each other to evaluate the reliability of the study. To mimic the water film that can appear during driving rain, the façades were irrigated through a wooden gutter.

    The results showed that the moisture ratio for façades with dripping channels was fluctuating under and above the moisture ratio for façades where the corner of the end grain was not mitred, regardless of treatment. The same results could be seen even when the treatment was considered. Façades with mitred end grains could therefore not be seen as better then façades without mitred end grains, so none of the hypotheses could get any support. However, a slightly smaller moisture ratio could be observed on surface treated façades, regardless the angle of the end grain.

    The conclusion based on the used irrigation model was that the dripping channel is of no significance for the moisture protection of the wooden façades. Instead there were indications that it is the surface treatment which makes a difference on the moisture content, something that is supported by existing research.

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  • 26.
    Bergström, Viktor
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science.
    Tölli, Emil
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science.
    Kolfiberförstärkning av limträbalkar: Fuktens inverkan på förstärkningen2019Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The point with this exam-essay is to study how the strength in glulam beams reinforced with carbon fiber will differentiate with an increased relative humidity (RH). The literature study brings up older work and science in the field that focuses on different reinforcement that can improve the strength in glulam beams.Glulam has higher strength than regular wood, this is due to how glulam is being constructed. When the usage limit condition is being determined the length of the beam will be a factor in deciding highest allowed bending on the beam. Carbon fiber, that has a greater strength than glulam can be used as a reinforcement on the glulam to give it higher strength. When the relative humidity is increased the glulam’s strength will decrease, the goal was to study how great the strength of the reinforced glulam beams would be when the relative humidity in the beams was being increased.In this essay a total of 26 glulam-samples was bent until they reached breaking point, out of these 26 samples half of them will be reinforced with carbon fiber underneath the beam. Half of the samples will be submerged in water, both reinforced and regular beams, where they will stay in two weeks until they are brought up again for bending-tests.The reinforced beams did not show an increase in torque capacity when compared to the non-reinforced beams when analyzing the average force. When analyzing the calculated 95 % -fractile the reinforced beams did show an increase in torque capacity. The dry reinforced glulam-beams showed an increase with 4,8 % and the wet reinforced glulam-beams showed an increase with 13,3 %.

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    Kolfiberförstärkning av limträbalkar
  • 27.
    Blomberg, Emil
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Boqvist, Simon
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Lauridsen, Markus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Tvärkraftsförstärkning av limträ med inlimmade gängstänger2019Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Syftet med studien var att undersöka hur tvärkraftskapaciteten i limträ påverkades om den förstärktes med inlimmade gängstänger samt att studera samverkan mellan limträ och gängstänger.

    En litteraturstudie genomfördes för att ta del av tidigare forskning. Förstärkning av tvärkraftskapaciteten hos limträbalkar är ett område där begränsad forskning skett. Ahlskog och Ross (2015) berörde detta område om hur limträ förstärkts mot tvärkraftbrott med pålimmade träribbor på utsidan. Resultatet från Ahlskog och Ross (2015) visade att deras förstärkningsmetod medförde en ökad tvärkraftskapacitet på 11 %. Denna studie var en vidareutveckling på Ahlskog och Ross (2015) arbete men med en ny förstärkningsmetod med inlimmade gängstänger i olika vinklar mot fiberriktningen.

    Testet bestod av fem olika provserier med åtta prover i varje serie. Provserie 1 var oförstärkt. Provserie 2 och 4 var förstärkta med inlimmade gänstänger i två olika vinklar mot fiberriktningen och testades med avseende för tvärkraftkapaciteten och jämfördes mot den oförstärkta. Provserie 3 och 5 var förstärkta på samma sätt som provserie 2 och 4 men provbitarna var klyvda i mitten och testades med avseende på gängstängernas hållfasthet och jämfördes mot provserie 2 och 4 för att undersöka samverkan. Provbitarna skruvades fast i två anhåll som placerades i tryckprovmaskinen som utsatte provbitarna med belastning tills brott inträffade. Maskinen var kopplad till en dator som registrerade samtliga värden i maskinens datorprogram Trapezium X.

    Studien resulterade i en ökning av tvärkraftkapaciteten på 13 % för provserie 2 förstärkt 45° och 1,0 % för provserie 4 förstärkt 90° jämfört med provserie 1. Samverkan mellan limträ och gängstänger resulterade i 32 % samverkan för provserie 2 förstärkt 45° och 4 % samverkan för provserie 4 förstärkt 90°. Resultatet hade förbättrats och visat en tydligare ökning av tvärkraftskapaciteten om fler felkällor hade beaktats i ett tidigare skede. En av dessa felkällor var torrsprickor, vilket resulterade i att provbitarna gav ett lägre värde gentemot de teoretiska beräkningarna.

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  • 28.
    Blomqvist, Stefan
    et al.
    Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Amiri, Shahnaz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology. Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Rohdin, Patrik
    Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Ödlund, Louise
    Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Analyzing the performance and control of a hydronic pavement system in a district heating network2019In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, no 11, article id 2078Article in journal (Refereed)
    Abstract [en]

    A hydronic pavement system (HPS) is an alternative method to clear snow and ice, which avoids the use of salt, sand, and fossil fuel in conventional snow clearance, and minimizes the risk of accidents. The aim is to analyze the performance of different control strategies for a 35,000 m2 HPS utilizing heat from a district heating and cooling (DHC) system. The key performance indicators are (1) energy performance of the HPS, and (2) primary energy use, (3) electricity production and (4) greenhouse gas (GHG) emissions from the DHC system. The methodology uses a simulation model of the HPS and an optimization model of the DHC system. Three operational strategies are analyzed: A reference scenario based on the current control strategy, and scenarios where the HPS is shut down at temperatures below −10 ◦C and −5 ◦C. The study shows that the DHC return temperature is suitable for use. By operational strategies, use during peak demand in the DHC system can be avoided, resulting in reduced use of fossil fuel. Moreover, the energy use of the HPS could be reduced by 10% and the local GHG emissions by 25%. The study emphasizes that the HPS may have positive effects on global GHG emissions, as it enables electricity production from renewable resources. 

  • 29. Blomqvist, Stefan
    et al.
    La Fleur, Lina
    Linköpings universitet.
    Amiri, Shahnaz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Rohdin, Patrik
    Linköpings universitet.
    Ödlund, Louise
    The Impact on System Performance When Renovating a Multifamily Building Stock in a District Heated Region2019In: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 11, no 8, article id 2199Article in journal (Other academic)
    Abstract [en]

    In Sweden, 90% of multifamily buildings utilize district heat and a large portion is in need of renovation. The aim is to analyze the impact of renovating a multifamily building stock in a district heating and cooling system, in terms of primary energy savings, peak power demands, electricity demand and production, and greenhouse gas emissions on local and global levels. The study analyzes scenarios regarding measures on the building envelope, ventilation, and substitution from district heat to ground source heat pump. The results indicate improved energy performance for all scenarios, ranging from 11% to 56%. Moreover, the scenarios present a reduction of fossil fuel use and reduced peak power demand in the district heating and cooling system ranging from 1 MW to 13 MW, corresponding to 4–48 W/m2 heated building area. However, the study concludes that scenarios including a ground source heat pump generate significantly higher global greenhouse gas emissions relative to scenarios including district heating. Furthermore, in a future fossil-free district heating and cooling system, a reduction in primary energy use will lead to a local reduction of emissions along with a positive effect on global greenhouse gas emissions, outperforming measures with a ground source heat pump.

  • 30.
    Bondsman, Benjamin
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Al, Barzan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Hedlund, Felix
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Dimensionering av höga balkar enligt fackverksanalogi: -En parametrisk studie2019Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
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  • 31.
    Bordes Roca, Adria
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science.
    Impacts of implementation of electric scooters in daily transport: case study in Gavle2019Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
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  • 32.
    Braat-Eggen, Ella
    et al.
    Avans University of Applied Sciences, Tilburg, the Netherlands; Eindhoven University of Technology, the Netherlands .
    Keus van de Poll, Marijke
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science.
    Hornikx, Maarten
    Eindhoven University of Technology, the Netherlands.
    Kohlrausch, Armin
    Eindhoven University of Technology, the Netherlands.
    Auditory distraction in open-plan study environments: Effects of background speech and reverberation time on a collaboration task2019In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 154, p. 148-160Article in journal (Refereed)
    Abstract [en]

    Previous research has shown that semantic-based tasks are negatively influenced by semantic aspects in background speech. Collaboration is an important task in open-plan study environments and is a semantic task which might be disrupted by background speech. Therefore, the aim of this study was to analyze the influence of irrelevant background speech on student-collaboration. Participants worked in pairs to solve spot-the-difference puzzles, by using the 'DiapixUK' collaboration task, while they were exposed to different background sound scenarios. The composed sound scenarios varied in semantic content (mother tongue and foreign language background speech)and reverberation time (short vs long), the latter affecting speech intelligibility. Although a longer reverberation time decreases the intelligibility of background speech and a foreign language decreases meaningfulness of speech, no significant changes in performance were found. On the other hand, the data show an increased perceived disturbance for a longer reverberation time, which we interpret as an increased difficulty of interpersonal communication in the collaboration task due to the increased level of the background speech. The quiet reference condition was the most preferred sound condition which is in line with both the effect of a low background sound level and the absence of semantic interference. 

  • 33.
    Buccolieri, Riccardo
    et al.
    Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, University of Salento, Lecce, Italy.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Di Sabatino, Silvana
    Department of Physics and Astronomy, University of Bologna, Bologna, Italy.
    The drag force distribution within regular arrays of cubes and its relation to cross ventilation – Theoretical and experimental analyses2019In: Journal of Wind Engineering and Industrial Aerodynamics, ISSN 0167-6105, E-ISSN 1872-8197, Vol. 189, p. 91-103Article in journal (Refereed)
    Abstract [en]

    A novel set of wind tunnel measurements of the drag force and its spatial distribution along aligned arrays of cubes of height H and planar area index λ p (air gap between cubes) equal to 0.028 (5H) to 0.69 (0.2H) is presented and analysed. Two different types of measurements are compared: one type where the drag force is obtained using the standard load cell method, another type where the drag force is estimated by measuring the pressure difference between windward and the leeward façades. Results show that the drag force is nearly uniformly distributed for lower λ p (0.028 and 0.0625), it decreases up to 50% at the second row for λ p = 0.11, and it sharply decreases for larger λ p (from 0.25 to 0.69) where the force mostly acts on the first row. It follows that for the lowest λ p the drag force typically formulated as a drag area corresponds to the total frontal area of the array, whereas for large λ p the drag area corresponds to the area of the first row. By assessing the driving pressure for ventilation from the drag force, the analysis is extended to estimate the cross ventilation as an example of application of this type of measurements. 

  • 34.
    Bäcklin, Malin
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science.
    Söderlund, Sandra
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science.
    Nudging mot hållbara transportbeteenden: Med framing som verktyg?: En experimentell enkätstudie om framings påverkan på studenters skattning av miljöattityder, intentioner och attityder till resvanor och val av färdmedel2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Greenhouse gas emissions from passenger cars have a negative impact on the climate and have led us to face major challenges today. To reduce greenhouse gas emissions, people need to change their transport behavior. Nudging is a concept that is used to supplement existing measures and is based on the fact that a selection situation is arranged in a way that helps man to make a desirable decision without limiting the individual's freedom of choice. There are different types of nudge tools, one of which is about producing information. Framing means that a certain type of information is presented in a certain way by highlighting a particular problem via communication texts. The main purpose of the present study is to demonstrate, by means of a questionnaire survey, whether, and if so, how, presentation of information and images affect how people estimate their environmental attitudes, as well as attitudes and intentions to travel habits and choice of means of transport. A sub-purpose is also to investigate whether framing of geographical distance affects the estimation in the survey differently.

    The survey was answered by 120 students at the University of Gävle. The questionnaire contained questions that measured general environmental attitudes and self-constructed issues that measured the students' attitudes and intentions to their travel habits and choice of means of transport. Three questionnaires were designed, two of which contained information on the problem of greenhouse gas emissions from passenger cars, and a supplementary picture from a geographically local and global perspective. The results showed that framing had no significant impact on how the students estimated their environmental attitudes, or their attitudes and intentions to travel habits and choice of means of transport. The results also did not indicate any differences between how geographical framing affected the estimate. Based on the results, the methodical procedure has been discussed. One assumption is that the framing had a greater chance of giving an effect if the message was sharper and more worrying, and if the selection was made in a different population than students. The results, however, demonstrate the importance of continuing to test different nudges, including the nudge tool framing, in different contexts and that they are tested on a small scale before being implemented on a larger scale.

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  • 35.
    Cabral, Diogo
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Gomes, João
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Karlsson, Björn O.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Performance Evaluation of Non-Uniform Illumination on a Transverse Bifacial PVT Receiver in Combination with a CPC Geometry2019In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 194, p. 696-708Article in journal (Refereed)
    Abstract [en]

    PVT collectors co-generate electricity and heat from the same gross area, thus achieving higher combined heat and electric yields. A comprehensive evaluation has been carried out on non-uniform solar irradiation profile distributions on four symmetric low concentration CPC PVT (LCPVT) solar collector design concepts. Additionally, an electrical and thermal performance evaluation of symmetric truncated LCPVT solar collectors based on a CPC reflector geometry with a central transverse bifacial PVT receiver has been carried out, through a numerical ray-tracing model software and a multi-paradigm numerical computing environment software. A simplified thermal (quasi-dynamic testing method for liquid heating collectors described in the international standard for solar thermal collectors ISO 9806:2017) and electrical performance models were employed to evaluate the LCPVT design concepts. The evaluation was carried out for heating Domestic Hot Water (DHW) for a Single Family House (SFH) in Fayoum (Egypt), where energy yields between 351 and 391 kWh/m2/year have been achieved. The non-uniform solar irradiation assessment showed that the PV cells are exposed to high levels of radiation due to the specific reflector geometry. Furthermore, the study showed that the CPC geometries are very sensitive to the shading effect, as partial shadowing is substantial for high incidence angles.

  • 36.
    Campbell, T. A.
    et al.
    Department of Psychology and Logopedics, Faculty of Medicine, University of Helsinki, Helsinki, Finland.
    Marsh, John E.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science. School of Psychology, University of Central Lancashire, Preston, UK.
    On corticopetal-corticofugal loops of the new early filter: from cell assemblies to the rostral brainstem2019In: NeuroReport, ISSN 0959-4965, E-ISSN 1473-558X, Vol. 30, no 3, p. 202-206Article in journal (Refereed)
  • 37.
    Carlander, Jakob
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Trygg, Kristina
    Technology and Social Change, Linköping University, Linköping, Sweden.
    Moshfegh, Bahram
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology. Division of Energy Systems, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Integration of measurements and time diaries as complementary measures to improve resolution of BES2019In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, no 11, article id 2072Article in journal (Refereed)
    Abstract [en]

    Building energy simulation (BES) models rely on a variety of different input data, and the more accurate the input data are, the more accurate the model will be in predicting energy use. The objective of this paper is to show a method for obtaining higher accuracy in building energy simulations of existing buildings by combining time diaries with data from logged measurements, and also to show that more variety is needed in template values of user input data in different kinds of buildings. The case studied in this article is a retirement home in Linköping, Sweden. Results from time diaries and interviews were combined with logged measurements of electricity, temperature, and CO2 levels to create detailed occupant behavior schedules for use in BES models. Two BES models were compared, one with highly detailed schedules of occupancy, electricity use, and airing, and one using standardized input data of occupant behavior. The largest differences between the models could be seen in energy losses due to airing and in household electricity use, where the one with standardized user input data had a higher amount of electricity use and less losses due to airing of 39% and 99%, respectively. Time diaries and interviews, together with logged measurements, can be great tools to detect behavior that affects energy use in buildings. They can also be used to create detailed schedules and behavioral models, and to help develop standardized user input data for more types of buildings. This will help improve the accuracy of BES models so the energy efficiency gap can be reduced. 

  • 38.
    Carlos-Pinedo, Sandra
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science.
    Wang, Zhao
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science.
    Eriksson, Ola
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science.
    Methane yield from SS-AD: Experiences to learn by a full spectrum analysis at laboratory-, pilot- and full-scale2019In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 127, article id 105270Article, review/survey (Refereed)
    Abstract [en]

    Solid-state anaerobic digestion (SS-AD) takes place when solid content of the substrate is higher than 15%. Some advantages of this technology have been recognized as e.g., less required water added to raw feedstock and consequently minimized digester size and cost, higher volumetric organic loading rates (OLR) that may lead to higher efficiency methane yield and better acceptance of a wide range of feedstocks. However, scientific studies of SS-AD at pilot- and full-scale are very few and difficulties have been reported in operating SS-AD, especially when the system undergoes a scale-up, where methane production is the purpose. As a result, this review gives a summary of scientific studies for SS-AD processes at laboratory-, pilot- and full-scale, where a great diversity of substrate composition, reactor design and operational parameters have been categorized, and their performances in terms of methane yield have been analyzed. This, in turn, helps to identify that factors affecting methane yields at different scales arise mainly from operational conditions as well as the characteristic of feedstocks. This review even contributes to suggest several strategies for improvement of methane yield at full-scale.

  • 39.
    Carlos-Pinedo, Sandra
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Wang, Zhao
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science.
    Eriksson, Ola
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science.
    Soam, Shveta
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science.
    Study of the digestion process at a full-scale solid-state biogas plant by using ORWARE: Model modification and implementation2020In: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456, Vol. 107, p. 133-142Article in journal (Refereed)
    Abstract [en]

    The configuration of the reactor influences the digestion process and thus the product yields; other factors such as the rate of biogas production or biogas loss also affect the process specifically with high solid configuration. With these in mind, the ORganic WAste REsearch (ORWARE) anaerobic digestion sub-model was modified to be able to study solid-state anaerobic digestion (SS-AD) (using plug-flow reactor). The simulation results from the updated model agreed with the operational data with respect to methane yield, digestate yield and energy turnover. The model was found to be sensitive to changes in feedstock composition but to a lesser extent to changes in process temperature and retention time. By applying the model on several cases of liquid anaerobic digestion (L-AD), it was noticed that L-AD at mesophilic condition with 25 retention days seemed to be superior to other cases of L-AD with regard to energy turnover. However, even if similar methane production were observed for L-AD and SS-AD, the model suggested higher energy turnover for the case of SS-AD at thermophilic condition, being 10% more in average in comparison with cases of L-AD.

  • 40.
    Carlos-Pinedo, Sandra
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Wang, Zhao
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science.
    Eriksson, Ola
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science.
    Soam, Shveta
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science.
    Study of the digestion process at a full-scale solid-state biogas plant by using ORWARE: Model modification and implementation2020In: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456, p. 133-142Article in journal (Refereed)
    Abstract [en]

    The configuration of the reactor influences the digestion process and thus the product yields; other factors such as the rate of biogas production or biogas loss also affect the process specifically with high solid configuration. With these in mind, the ORganic WAste REsearch (ORWARE) anaerobic digestion sub-model was modified to be able to study solid-state anaerobic digestion (SS-AD) (using plug-flow reactor). The simulation results from the updated model agreed with the operational data with respect to methane yield, digestate yield and energy turnover. The model was found to be sensitive to changes in feedstock composition but to a lesser extent to changes in process temperature and retention time. By applying the model on several cases of liquid anaerobic digestion (L-AD), it was noticed that L-AD at mesophilic condition with 25 retention days seemed to be superior to other cases of L-AD with regard to energy turnover. However, even if similar methane production were observed for L-AD and SS-AD, the model suggested higher energy turnover for the case of SS-AD at thermophilic condition, being 10% more in average in comparison with cases of L-AD.

  • 41.
    Casanaba, Pablo
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Development of a Simple and Cheap Equipment for monitoring the solar Irradiance on PV modules.2019Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Increased use of renewable energies that is taking place all over the world is having a very important impact on the photovoltaic solar energy industry. This means of obtaining electrical energy is one of the most promising ones nowadays, thanks to the fact that it is a technology of easy installation and maintenance. However, the number of hours that a photovoltaic system works at maximum power depends almost entirely on environmental conditions, mainly in terms of solar irradiance.Solar irradiance is a magnitude that measures the power released by sunlight per unit area; the higher it is, the more power the photovoltaic system will generate.Therefore, it is very important to measure this magnitude in order to obtain data that either can give information about which is the best place to install a photovoltaic system or expect the device performance.Unfortunately, sensors used nowadays to measure this magnitude are quite expensive. The most widely used are the so-called pyranometers, with an average cost of between 8000 SEK to 10000 SEK, and solar reference cells, which can be quite cheaper (1000 SEK), but also can be the most expensive devices on the market depending on the features they have (some reference cells cost 20000 SEK).In this thesis, a solar irradiance sensor based on the treatment of a current generated by a silicon photodiode has been designed, built and calibrated. The signal generated by the device is a voltage that has been obtained by means of a current-to-voltage converter amplifier stage. Once the construction of the circuit was completed, it was tested on the roof of Hall 45 located in the University of Gävle. The testing was carried out on 13, 14 and 15 May 2019, and it consisted in the comparison of the signal generated by the new device and the signals generated by a pyranometer and a solar cell.The result is a device priced at 200 SEK, which shows acceptable levels of accuracy during central daylight hours but shows a strong angular dependence on incident light during sunrise and sunset.

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  • 42.
    Cebollada Alvarez, Virginia
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science.
    Evaluation of the performance of optimizerbased PV systems under shading conditions2019Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Total or partial shading conditions have a detrimental impact in the output energy ofphotovoltaic (PV) systems and in the semiconductor materials PV technologies are made of.Residential PV installations are very likely to be exposed to shade projected by nearbyobjects such as buildings or neighboring trees. The electrical configuration of PV systems iscrucial to mitigate the shading effect, as it is the use of power optimizers. This study assessesthe shading impact on two different types of residential PV systems to verify gains associatedwith SolarEdge optimizers and support product marketing. It aspires to help PV ownersselect power inverters that maximize the annual energy produced. Experiments have beenperformed simulating snow coverage and tree shading on a string-based system (Fronius)and an optimizer-based system (SolarEdge). Findings demonstrated the decrease in lossesfrom partial shading conditions with power optimizers. SolarEdge optimizers reduceshading power losses from 50% to 29% in comparison to a standard string system whensimulated snow coverage is applied. Results also showed that SolarEdge system decreasedtree shading losses from 17% to 13% in comparison to string-based system.

  • 43.
    Cehlin, Mathias
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Mapping tracer gas concentrations using a modified Low Third Derivative method: numerical study2019In: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044, Vol. 18, no 2, p. 136-151Article in journal (Refereed)
    Abstract [en]

    In indoor applications, computed tomography is the process of transforming a network of intersecting attenuation measurements into a spatially resolved two-dimensional concentration map. In this study the Low Third Derivative method (LTD) was numerically evaluated and optimized for different conditions. A modified version of the LTD algorithm (LTDm) was proposed and evaluated against the original version. Eight test maps were reconstructed under different conditions, such as weight ratio, pixel resolution, beam density and measurement noise. Performance of both LTD algorithms was found to be intimately related to the number of peaks and complexity in the test map and the steepness of the peaks. The LTDm algorithm improved the quality, especially for concentration maps including steep gradients and regions with very low concentrations. The LTDm method heavily lessened aliasing distortions and efficiently minimized the effects of noise.

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  • 44.
    Cehlin, Mathias
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Karimipanah, Taghi
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Larsson, Ulf
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Ameen, Arman
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Comparing thermal comfort and air quality performance of two active chilled beam systems in an open-plan office2019In: Journal of Building Engineering, E-ISSN 2352-7102, Vol. 22, p. 56-65Article in journal (Refereed)
    Abstract [en]

    The traditional air distribution and supply devices in ventilated rooms are not always able to effectively remove excess heat from the space. Therefore, chilled beams, especially the active systems, are used to achieve the desired cooling demand. The focus of this paper was the potential benefit of a newly designed active chilled beam (ACB) system, to improve heat removal effectiveness local thermal condition and indoor air quality in the occupants’ breathing zone. The system based on 1-way flow design (1W-ACB) was installed in an open-plan office and its performance was studied by analysing the temperatures, velocities and tracer gas concentrations in predetermined risky zones. The system was compared against a traditional 4-way flow design (4W-ACB).

    The obtained results showed that heat removal effectiveness was slightly higher for the 1W-ACB system compared to the 4W-ACB system. The local thermal condition was very good close to the workstations when using 1W-ACB. The benefits of the new system were also shown in the occupied zone by analysing the mean age of air and air-change effectiveness (ACE) in the breathing level at the workstation locations. The 1W-ACB system provided air with lower mean age (fresher air), and therefore higher ACE, near the breathing zone at the workstations compared to the 4W-ACB. On the other hand, the 4W-ACB system had the advantage of providing high thermal and mean age of air uniformity throughout the room.

  • 45.
    Chacin, Luís
    et al.
    Loughborough University, UK.
    Rangel, Simon
    FEUP, Porto, (Portugal.
    Cabral, Diogo
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Gomes, João
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Impact study of operating temperatures and cell layout under different concentration factors in a CPC-PV solar collector in combination with a vertical glass receiver composed by bifacial cells2019In: Impact study of operating temperatures and cell layout under different concentration factors in a CPC-PV solar collector in combination with a vertical glass receiver composed by bifacial cells / [ed] SWC-SHC, 2019Conference paper (Refereed)
    Abstract [en]

    Solar Collectors with Compound Parabolic Concentrator (CPC) reflectors redirect solar irradiance into the receiver (placed in optimal position). The concept of such devices is to reduce the installation area and energy costs [1]. This research focuses on the behaviour and efficiency of a stationary CPC-PV solar collector. Each trough of this collector has different concentration factors (1.25 and 1.66) with vertically placed bi-facial cell receivers. An analysis of the electrical efficiency is performed in order to evaluate the viability of a CPC geometry with a vertical bifacial PV receiver. Furthermore, an investigation on bifacial cells performance due to concentration (and consequently increased cell temperature) is carried out. A numerical simulation of the yearly available radiation and the Incident Angle Modifiers (IAM) for each geometry is also conducted. Finally, a comparison between the simulations and the outdoor testing on the prototype collector is detailed. The tests took place in Gävle, Sweden (61º Latitude). The results showed that higher concentration factors led to larger operating temperatures (114ºC for a concentration factor of 1.66 and 96ºC for a concentration factor of 1.25). Although this may compromise the cell performance and shorten the device’s life cycle, it is shown that appropriate ventilation will allow manageable operating temperatures.

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    Impact study of operating temperatures and cell layout under different concentration factors in a CPC-PV solar collector in combination with a vertical glass receiver composed by bifacial cells
  • 46.
    Choonya, Gasper
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Experimental investigation of ventilation performance of corner placed stratum ventilation in an office environment2019Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    Energy use in buildings account for about one third of the total global energy supply and contributes as much as 30% of the anthropogenic greenhouse gas emissions. It is estimated that energy use in buildings will increase to 67% by 2030. The need for better thermal comfort and air quality in indoor environments is the leading cause for high energy use in buildings.  Heating, ventilation and air conditioning systems take up about 50% of the total energy use in buildings which is about 10-20% of the national energy use in most developed countries. The development and adoption of sustainable ventilation systems is a viable solution to mitigate climate change and curtail carbon emissions.

    The experimental study was conducted in a room resembling a modern office in a laboratory environment. The study involved investigating the ability of the system to provide cooling and heating. Concentration decay tracer gas technique using Sulphur hexafluoride (SF6) gas was used to determine the local air change index and air change efficiency in the room. Low-velocity omni-directional thermistor anemometer type CTA88 were used to measure the air velocity and temperature in the room. Smoke was used to visualise the flow patterns created in the room.  The climate chamber was used to mimic climatic conditions in winter. Fifteen cases were investigated with five air flow rates set points (30, 40, 50, 60 and 70 l/s) at three supply air temperatures, i.e., 17.6 °C, 21.0 °C and 25.3 °C.

    The results of the local air change index and air change efficiency for the nominal supply temperature of 17.6 °C showed that the system had strong characteristics of a mixing ventilation system. At the supply air temperature of 21.0 °C, the performance of the system deteriorated slightly to below that of a mixing ventilation system and could not satisfactorily provide heating at supply temperature of 25.3 °C. Better performance of the system at all supply air temperature setpoints was observed at lower airflow rates. At all supply air temperature setpoints, relatively higher degree of temperature stratification was observed at lower supply. The draught rate levels decreased with increase in supply air temperature and height. The location of the air inlet terminals in relation to the workstations had significant effect on the performance of the system. The stratum ventilation system did not work efficiently because the air streams were heavily mixed before reaching the occupants.

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  • 47.
    Christopher, Magnusson
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science.
    Förbättrat inomhusklimat med lägre energiförbrukning i öppet kontorslandskap: Ventilationens påverkan på inomhusklimatet och termisk komfort2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Idag spenderas en stor del av vår tid inomhus, det ställer krav på inomhusluften.  Koldioxid och andra föroreningar, som stannar i luften vid dåligt ventilerade  lokaler, påverkar negativt och är bevisat att påverka prestationen och produktiviteten  hos människor i specifika uppgifter. Idag läggs mycket fokus på miljösmarta  lösningar och effektiviseringar, men ibland glöms inomhusklimatet bort. För att  människor ska få en behaglig upplevelse av inomhusklimatet krävs  kvalité på inomhusluften men också på den termiska komforten. Huvudsyftet med examensarbetet är att förklara hur det går att uppnå  förbättrat inomhusklimat och samtidigt minska energiförbrukningen. Genom att minska energibehovet kan företag bli mer konkurrenskraftiga och samtidigt rusta sig mot de stigande elpriserna. Det finns även en ekonomisk fördel för företag såväl som för privata bostäder. Examensarbetet består utav en fallstudie, där luftenstemperatur och fuktighet kommer at loggas och data genereras. Loggning kommer att  ske vid två tillfällen. Först i början för att få en uppfattning om varför  personalen upplever dåligt inomhusklimat och sedan efter justering av luftflödena  för att se skillnaden i förändringen av inomhusklimatet och energipåverkan.   Genom att justera systemet och sammanställa resultat har forskningsfrågan ”Kan inomhusklimatet förbättras samtidigt och samtidigt minska energiförbrukningen?”  besvarats. Litteraturstudien visar att om alternativa ventilationsprinciper  används, istället för det konventionella omblandande systemet, går det att minska  energiförbrukningen samtidigt som inomhusklimatet förbättras. Detta har gjorts  genom att golvventilation använts där tilluften tillförts lågt och undertempererad för att luften ska stiga genom de termiska krafterna. Resultatet visar att termisk komfort försämrats enligt enkätstudierna, men samtidigt visar det en förbättring av  inneklimatet i enskilda frågor. Mätresultaten indikerar även på förbättrad  ventilation och inomhusklimat. Slutligen presenterades energibesparingsåtgärder som företaget kan göra för att minska energibehovet och samtidigt förbättra den termiska komforten.

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    Förbättrat inomhusklimat med lägre energiförbrukning i öppet kontorslandskap
  • 48.
    Chrysochoou, Christos
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science.
    Convert an Anaerobic Digestion Slaughterhouse to a Money Maker2019Independent thesis Advanced level (degree of Master (One Year)), 40 credits / 60 HE creditsStudent thesis
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  • 49.
    Colding, Johan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science. The Beijer Institute of Ecological Economics, The Royal Swedish Academy of Sciences, Sweden; Stockholm Resilience Centre, Stockholm University, Sweden.
    Barthel, Stephan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science. Stockholm Resilience Centre, Stockholm University, Sweden.
    Exploring the social-ecological systems discourse 20 years later2019In: Ecology & society, ISSN 1708-3087, E-ISSN 1708-3087, Vol. 24, no 1, p. 423-432, article id 2Article in journal (Refereed)
    Abstract [en]

    This paper explores the 20-year evolution of the social-ecological systems framework (SESs). Although a first definition of SES dates back to 1988, Berkes and Folke more thoroughly used the concept in 1998 to analyze resilience in local resource management systems. Since then studies of interlinked human and natural systems have emerged as a field on its own right, promoting interdisciplinary dialogue and collaboration in a wide set of fields and practices. As the SES concept celebrates its 20-year existence we decided to make an overview of how authors use the concept in relation to research that deals with social and ecological linkages. Hence, we conducted a review of the SES concept using the Scopus database, analyzing a random set of journal articles on social-ecological systems (n = 50) regarding definitions of SES, authors’ main sources of inspiration in using the concept, as well as document type, subject area, and other relevant information. Although there is a steady increase of SES publications, we found that 61% of the papers analyzed did not even provide a definition of the term social-ecological system(s), a shortcoming that makes case comparisons difficult and reduces the usefulness of the concept. We also found three common SES frameworks that authors seem to be most commonly inspired by, referred to here as the original, the robustness, and multitier frameworks, respectively. The first can be characterized as a descriptive framework, the latter two more as diagnostic frameworks, useful for modeling. Although it would be a bit presumptuous of us to come up with a more thorough definition of the SES concept in this paper, we urge SES scholars to be more meticulous in making explicit what they mean by a social-ecological system when conducting SES research. 

  • 50.
    Colding, Johan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science. Stockholm Resilience Centre, Stockholms Universitet; Royal Swedish Academy of Sciences.
    Barthel, Stephan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science. Stockholm Resilience Centre, Stockholms Universitet.
    Sörqvist, Patrik
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Environmental Science.
    Wicked Problems of Smart Cities2019In: Smart Cities, ISSN 2624-6511, Vol. 2, no 4, p. 512-521Article in journal (Refereed)
    Abstract [en]

    It is often uncritically assumed that, when digital technologies are integrated into the operation of city functions, they inevitably contribute to sustainable urban development. Such a notion rests largely on the belief that Information and Communication Technology (ICT) solutions pave the way for more democratic forms of planning, and that ‘smart’ technological devices result in a range of environmental benefits, e.g., energy efficiency and the mitigation of global warming. Drawing on the scientific literature that deals with ‘smart cities’, we here elaborate on how both propositions fail to consider drawbacks that could be characterized as ‘wicked’, i.e., problems that lack simplistic solutions and straightforward planning responses, and which often come about as ‘management surprises’, as a byproduct of achieving sustainability. We here deal with problems related to public choice constraints, ‘non-choice default technologies’ and the costs of automation for human learning and resilience. To avoid undemocratic forms of planning and too strong a dependence on non-choice default technologies, e.g., smart phones, we recommend that planners and policy makers safeguard redundancy in public-choice options by maintaining a wide range of alternative choices, including analog ones. Resilience thinking could help planners deal more effectively with the ‘wickedness’ of an increasingly hyper-connected society.

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