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  • 51. Kovács, P.
    et al.
    Pettersson, U.
    Persson, M.
    Perers, Bengt
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Fischer, S.
    Improving the accuracy in performance prediction for new collector designs2011Conference paper (Refereed)
  • 52.
    Kuhn, Tillmann
    et al.
    Fraunhofer ISE.
    Fath, Karoline
    Fraunhofer ISE.
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Gustafsson, Marcus
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Nouvel, Romain
    ZAFH.
    Fedrizzi, Roberto
    EURAC.
    D2.3 RES availability survey and boundary conditions for simulations2014Report (Other academic)
  • 53.
    Küchler, Stefan
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Solar Energy assessment based on weather station data for direct site monitoring in Indonesia2013Independent thesis Advanced level (degree of Master (One Year)), 12 credits / 18 HE creditsStudent thesis
    Abstract [en]

    This thesis evaluates different sites for a weather measurement system and a suitable PV- simulation for University of Surabaya (UBAYA) in Indonesia/Java. The weather station is able to monitor all common weather phenomena including solar insolation. It is planned to use the data for scientific and educational purposes in the renewable energy studies. During evaluation and installation it falls into place that official specifications from global meteorological organizations could not be meet for some sensors caused by the conditions of UBAYA campus. After arranging the hardware the weather at the site was monitored for period of time.

    A comparison with different official sources from ground based and satellite bases measurements showed differences in wind and solar radiation. In some cases the monthly average solar insolation was deviating 42 % for satellite-based measurements. For the ground based it was less than 10 %. The average wind speed has a difference of 33 % compared to a source, which evaluated the wind power in Surabaya. The wind direction shows instabilities towards east compared with data from local weather station at the airport.

    PSET has the chance to get some investments to investigate photovoltaic on there own roof. With several simulations a suitable roof direction and the yearly and monthly outputs are shown. With a 7.7 kWpeak PV installation with the latest crystalline technology on the market 8.82 MWh/year could be achieved with weather data from 2012. Thin film technology could increase the value up to 9.13 MWh/year. However, the roofs have enough area to install PV. Finally the low price of electricity in Indonesia makes it not worth to feed in the energy into the public grid.

  • 54.
    Lang, Markus
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Performance Study of a PVT Air Collector2016Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    PVT collectors are more and more in focus as they combine electricity generation and generation of heat in one single collector. In this thesis a thin film CIGS PV module is used to replace a conventional solar absorber and create an air ventilated PVT collector. The thesis includes the design and construction of the collector, measurement of important performance parameters as well as analysis of the collected data in terms of thermal and electrical performance.

    A Solibro CIGS PV module is used as solar absorber and a wooden box is constructed around the module. An electric fan is used to control air flow behind the PV module. Inlet and outlet air temperatures of the collector are measured as well as the temperatures of the backside of the PV module and the opposite wall in the air channel and logged together with irradiance level every ten seconds during a period of one week.

    During the measurement period with clear sky conditions quite constant irradiance levels can be measured resulting in a temperature increase between inlet and outlet air temperature of 22 °C. PV module temperatures reached values up to 60 °C while the outlet temperature reached 45 °C. Thermal power reached values above 300 W/m² and efficiency was calculated to 0.33 for high periods with high irradiance (900 W/m).

    Infrared images of the collector show that the heat distribution on the PV module was quite uniform which means that also air flow behind the module can be considered uniformly distributed. Only a small area around the air inlet showed slightly lower temperature levels compared to the opposite side at the same level.

    Electrical performance was analyzed theoretically by comparing output levels under conditions of forced ventilation and with natural ventilation. The temperature difference achieved by the cooling effect on the module by the forced airflow accounted for an increase of about 6 % of power output. In absolute numbers however the needed power for the fan is higher compared to the gain in electricity output from the 100 Wp PV module.

    It can be seen that measured outlet temperatures were slightly delayed compared to corresponding irradiance levels and the temperature changes are less fluctuating thus smoothened compared to the fast changing irradiance values. Pressure drop in the collector is a limiting factor that requires a minimum air gap diameter for a certain airflow.

    Using a CIGS PV module is a suitable option to replace a conventional absorber in a solar collector if the benefit from the produced electricity is of use and maximum thermal output is not the major concern. To achieve higher temperatures air flow needs to be decreased which will have a negative impact on the total electricity output.

    In terms of using such a collector for solar drying it depends on the prevailing climate conditions if desired temperature levels can be reached. The electricity produced by the PV module could directly be used to power an electric fan and in a further step could open for the option to control air flow and air temperature into the drying chamber.

  • 55.
    Leijonhufvud, Gustaf
    et al.
    Högskolan på Gotland, Uppsala universitet.
    Henning, Annette
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Rethinking indoor climate control in historic buildings: The importance of negotiated priorities and discursive hegemony at a Swedish museum2014In: Energy Research & Social Science, ISSN 2214-6296, Vol. 4, p. 117-123Article in journal (Refereed)
    Abstract [en]

    Much effort has in recent years been directed to support sustainable indoor climate control strategies in historic buildings. In this paper we show the necessity to complement the dominant technical approaches with research that take a wider interest in specific contexts, social practicies, and negotiated decisions. The objective of the paper is to illustrate how the interactions between perceptions and experiences of different professional groups are pivotal for the management of the indoor climate. An ethnographic study of decision making in an historic house museum was carried out in 2009 and 2012. Interviews were made with individuals who either took part in management or were affected by the indoor climate. The findings show how discussions among social actors and the way their respective priorities are negotiated are essential features of the management of the indoor climate and have a strong impact on the ability to modify it. It turns out that a hegemonic discourse about preservation as the dominant rationale for indoor climate control in tandem with "acceptable" conditions with respect to preservation have reinforced a state of stability. This explorative study opens up for a re-framing of how a more sustainable management of historic buildings can be achieved.  

  • 56. Li, Guozhen
    et al.
    Tang, Llewellyn
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Dong, Jie
    A review of factors affecting the efficiency of clean-in-place procedures in closed processing systems2019In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 178, p. 57-71Article in journal (Refereed)
    Abstract [en]

    This paper reviews the current state of researches on improvement of Clean-In-Place (CIP) procedures in closed processing system thus saving energy, with a special attention paid to the hydrodynamic effects of cleaning fluid and the numerical and experimental approaches to investigate the identified controlling factors. The paper discussed the fouling problems of processing plants and the importance of sufficient CIP procedures, the forces contributing to cleaning with a special focus on the hydrodynamic effects. In general, it is possible to enhance hydrodynamic removal forces by local introduction of, among others, high wall shear stress and fluctuation rate of wall shear stress without consuming more energy. A theoretical model of particle removal in flow was also reviewed which supports the factors identified. The paper therefore further reviewed and compared the current state of modelling and experimental techniques on CIP improvement. To simulation the CIP process, it is necessary to consider 3D time-resolved Large Eddy Simulation with a Hybrid RANS-LES WMLES as Sub-Grid-Scale model because it captures both the mean and fluctuation rate of flow variables, while affordable for industrial flows. The wall shear stress measurement techniques and cleanablity test methods were also discussed and suggested.

  • 57.
    Lidberg, Tina
    Dalarna University, School of Technology and Business Studies, Energy Technology. Högskolan i Gävle, Energisystem.
    Influences from Building Energy Efficiency Refurbishment on a Regional District Heating System2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Improving energy performance of existing buildings is an important part in decreasing energy use and in turn reduce the greenhouse gas emissions caused by human activity and the primary energy use.

    To be able to evaluate how energy refurbishment influences the greenhouse gas emissions and the primary energy use a wider system perspective is needed that puts the building in its context. This thesis deals with energy refurbishment packages performed on multi-family buildings within district heated areas and how they influence greenhouse gas emissions and primary energy use when the district heating use is altered.

    A simulated building is used to evaluate several energy refurbishment packages. The results are used as input data for models of district heating systems to cost optimize the district heating production. The results from the cost optimization are used to evaluate the impact on greenhouse gas emissions and primary energy use.

    The results show a difference between measures that saves district heating without increasing the use of electricity and measures that increases the use of electricity while district heating is saved. For example, a building refurbishment package including only building envelope improvements saves the same amount of district heating as a package including only mechanical ventilation with heat recovery. Despite this, the emissions of greenhouse gases and the use of primary energy is to a greater extent reduced in the first package because the use of electricity remains unchanged.

    Comparing energy refurbishment packages performed on the same building, but within different district heating systems, show the importance of the design of the district heating system. Depending on the fuel types used and to which extent electricity is co-produced in the district heating system, the results of implementing the energy refurbishment packages vary. The largest reduction of greenhouse gases and primary energy use occurs when a refurbishment package is performed on a building in a district heating system with high share of biofuel and no electricity production.

  • 58.
    Lidberg, Tina
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Olofsson, Thomas
    Dalarna University, School of Technology and Business Studies, Construction. Umeå universitet.
    Trygg, Louise
    Linköpings Universitet.
    System impact of energy efficient building refurbishment within a district heated region2016In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 106, p. 45-53Article in journal (Refereed)
    Abstract [en]

    The energy efficiency of the European building stock needs to be increased in order to fulfill the climate goals of the European Union. To be able to evaluate the impact of energy efficient refurbishment in matters of greenhouse gas emissions, it is necessary to apply a system perspective where not only the building but also the surrounding energy system is taken into consideration.

    This study examines the impact that energy efficient refurbishment of multi-family buildings has on the district heating and the electricity production. It also investigates the impact on electricity utilization and emissions of greenhouse gases.

    The results from the simulation of four energy efficiency building refurbishment packages were used to evaluate the impact on the district heating system. The packages were chosen to show the difference between refurbishment actions that increase the use of electricity when lowering the heat demand, and actions that lower the heat demand without increasing the electricity use. The energy system cost optimization modeling tool MODEST (Model for Optimization of Dynamic Energy Systems with Time-Dependent Components and Boundary Conditions) was used.

    When comparing two refurbishment packages with the same annual district heating use, this study shows that a package including changes in the building envelope decreases the greenhouse gas emissions more than a package including ventilation measures.

  • 59.
    Linde, Daniel
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Evaluation of a Flat-Plate Photovoltaic Thermal (PVT) Collector prototype2016Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This Master thesis, in collaboration with Morgonsol Väst AB, was completed as a part of the Solar Energy engineering program at Dalarna University. It analyses the electrical and thermal performance of a prototype PVT collector developed by Morgonsol Väst AB. By following the standards EN 12975 and EN ISO 9806 as guides, the thermal tests of the collector were completed at the facility in Borlänge. The electrical performance of the PVT collector was evaluated by comparing it to a reference PV panel fitted next to it. The result from the tests shows an improved electrical performance of the PVT collector caused by the cooling and a thermal performance described by the linear efficiency curve ηth=0.53-21.6(Tm-Ta/G). The experimental work in this thesis is an initial study of the prototype PVT collector that will supply Morgonsol Väst with important data for future development and research of the product.

  • 60. Luo, H.
    et al.
    Liang, X.
    Lu, J.
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Applicability analysis of insulation in different climate zones of China2017In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 142, p. 1835-1841Article in journal (Refereed)
    Abstract [en]

    In this paper we evaluated the applicability of the widely-used passive design strategy i.e., insulation, in three typical climate zones of China. Software IES VE was used for modelling and simulation of performance of insulation in a residential house. The practical behavior patterns of Chinese family from survey were utilized for analyzing the thermal characteristics of the house. Four parameters of the results were selected for analyzing the performance of insulation in three cities of China. The conditions varying in time periods and locations were compared on the basis of the simulation.

  • 61.
    Mattsson, Anders
    et al.
    Dalarna University, School of Technology and Business Studies, Forest and Wood Technology.
    Hernandez Velasco, Marco
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Rusu, Cristina
    Acreo Swedish ICT AB.
    Pietrzak, Malgorzata
    Azorina S.A.
    Ferreira, Raquel
    Azorina S.A.
    Radoglou, Kalliopi
    Democritus University of Thrace.
    Smirnakou, Sonia
    Democritus University of Thrace.
    Bantis, Filippos
    Democritus University of Thrace.
    Fulgaro, Nicoletta
    Università degli Studi dell'Insubria.
    Kotilainen, Titta
    Valoya OY.
    ZEPHYR Project – Deliverable D7.6: Articles and peer-reviewed papers2015Report (Other (popular science, discussion, etc.))
  • 62.
    Melo, Manuel
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Economic Evaluation of a Solar Charged Thermal Energy Store for Space Heating2013Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A thermal energy store corrects the misalignment of heating demand in the winter relative to solar thermal energy gathered in the summer. This thesis reviews the viability of a solar charged hot water tank thermal energy store for a school at latitude 56.25N, longitude -120.85W

  • 63. Menegon, D.
    et al.
    Persson, Tomas
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Haberl, R.
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Haller, M.
    Direct characterisation of the annual performance of solar thermal and heat pump systems using a six-day whole system test2020In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 146, p. 1337-1353Article in journal (Refereed)
  • 64.
    Mihaescu, Oana
    et al.
    Dalarna University, School of Technology and Business Studies, Human Geography.
    vom Hofe, Rainer
    University of Cincinnati, School of Planning.
    Using Spatial Regression to Estimate Property Tax Discounts from Proximity to Brownfields: A Tool for Local Policy-Making2013In: Journal of Environmental Assessment Policy and Management, ISSN 1464-3332, E-ISSN 1757-5605, Vol. 15, no 1Article in journal (Refereed)
    Abstract [en]

    This paper assesses the discount in property values due to proximity to brownfields using a spatial hedonic price model. Using two Bayesian hedonic pricing models, namely the spatial lag of X (SLX) model and the spatial Durbin error model (SDEM), this study identifies a significant decrease in property values for properties located within 2,000 feet of a brownfield. The loss in property value and the subsequent decrease in tax revenue for the City of Cincinnati, Ohio, are then calculated based on these results. Using logarithmic transformations of the property value and the distance to the nearest brownfield variables, we calculate that a 1% increase in the average distance to the closest brownfield leads to a 0.0893% increase in market value. This translates into a $2,262,569 total annual revenue loss for the City of Cincinnati that could presumably be recovered following brownfield cleanup. In addition to accounting for the phenomenon of spatial dependence, this study contributes to the urban planning and environmental policy literature by providing a method for local policy-makers to identify and estimate the negative effects of brownfield sites on local tax revenue.

  • 65.
    Nielsen, Caroline
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Travel Report from the first field trip within the SIDA supported project "Mini-grids supplied by renewable energy - improving technical and social feasibility: Including visits to Ihushi Development Center, Tweyambe Secondary School and Mavuno Project in Tanzania. Conducted in April 20112011Report (Other academic)
    Abstract [en]

    This report describes the outcome of the first visit to Tanzania, within the project "Mini-grids supplied by renewable energy - improving technical and social feasibility". The trip included visits to three different organizations; Ihushi Development Center (IDC) near Mwanza, TIDESO near Bukoba, and Mavuno Project in Karagwe. At IDC, a brief evaluation of the current power system was done and measuring equipment for long term measurements were installed. At all three locations investigations regarding the current and future electricity demand were conducted and connections to people relevant to the study were established. The report is including as well some technical specifications as some observations regarding organization and management of the technical systems. The trip was including only short visits and therefore only brief introductions to the different organizations, based on observations done by the author. The report is hence describing the author’s understanding of the technical system and social structures after only short visits to each of the organizations, and may differ from observations done at another point in time, over a different time period, or by some other person.This report describes the outcome of the first visit to Tanzania, within the project "Mini-grids supplied by renewable energy - improving technical and social feasibility". The trip included visits to three different organizations; Ihushi Development Center (IDC) near Mwanza, TIDESO near Bukoba, and Mavuno Project in Karagwe. At IDC, a brief evaluation of the current power system was done and measuring equipment for long term measurements were installed. At all three locations investigations regarding the current and future electricity demand were conducted and connections to people relevant to the study were established. The report is including as well some technical specifications as some observations regarding organization and management of the technical systems. The trip was including only short visits and therefore only brief introductions to the different organizations, based on observations done by the author. The report is hence describing the author’s understanding of the technical system and social structures after only short visits to each of the organizations, and may differ from observations done at another point in time, over a different time period, or by some other person.

  • 66.
    Pamidi R., Sreenivaasa
    et al.
    Exergy Ltd..
    Polidori, Carlo
    Veltha IVZW.
    Mattsson, Anders
    Dalarna University, School of Technology and Business Studies, Forest and Wood Technology.
    Hernandez Velasco, Marco
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Ghrissi, Meftah
    Robosoft SA.
    Carrel, Aubert
    Robosoft SA.
    Menta, Andrea
    CO.MET.ART. SAS.
    Ramiro, Manuel
    ADVANTIC Sistemas y Servicios.
    Kotilainen, Titta
    Valoya OY.
    Aikala, Lars
    Valoya OY.
    ZEPHYR Project – Deliverable D2.4: Technical specification for the Power system with solar panels2013Report (Other (popular science, discussion, etc.))
  • 67.
    Pamidi, Sreenivaasa R
    et al.
    Exergy Ltd..
    Hernandez Velasco, Marco
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Reducing the impact of forest plant production - Design of a stand-alone PV-hybrid system for powering an innovative forestry incubator2014In: 29th European Photovoltaic Solar Energy Conference and Exhibition Proceedings, 2014, p. 3811-3814Conference paper (Other academic)
    Abstract [en]

    Nowadays, the high demand of forestry products imposes a high pressure on the ecosystems and can derive in biodiversity lost and other ecological problems. Planted forests can contribute to more sustainable practices and help addressing other problems of global concern such as climate change, erosion and desertification. Large scale production of seedling is required to offset the high harvesting rates; however these intensive methods often have a negative impact on the environment. Funded by the European Commission under the Seventh Framework Programme (FP7), the ZEPHYR project consortium is developing innovative and cost-friendly technologies for the pre-cultivation of forestry species. These will be integrated into a functional and transportable system for pre-cultivation of seedlings, with zeroimpact on the environment and not affected by outdoor conditions. To achieve this, the incubator will be powered mainly by solar energy. This work aims to present the efforts made to design and optimize the solar photovoltaic (PV) system which will be mounted on the roof of the unit. Especially developed devices such as LED growth lamps and wireless sensors will be used to reduce energy consumption and monitor the cultivation process. A load profile study was conducted and the growth protocols were adapted to perform most of the tasks during daytime to use the energy from the PV panels directly. A battery bank will be designed to provide at least one day of autonomy in central European latitudes. Moreover, the power system will also be capable of connecting to the electricity grid or use a diesel generator as a backup.

  • 68. Pan, S.
    et al.
    Wang, H.
    Pei, F.
    Yang, L.
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    An investigation on energy consumption of air conditioning system in Beijing subway stations2017In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 142, p. 2568-2573Article in journal (Refereed)
    Abstract [en]

    This paper initially depicted on the energy consumption of air conditioning systems in Beijing subway stations. An investigation was conducted among ten underground subway stations to the examination of practical operation conditions of their cooling units. The overall field testing included information such as air conditioning system formation, equipment types, system operation parameters, energy consumption and system operation efficiency. The results showed that the COP value of refrigerators in the tested subway stations were generally high at about 4.4 in average. Nevertheless, the mean EER and SCOP values were nearly 27% and 48% lower than the average COP value due to the large amount of energy consumption in water pumps, cooling towers and fans. There was a big difference among each station in terms of the instantaneous power consumption of air conditioning systems. The most energy consuming station was nearly seven times higher than the least one. It was observed that there was a lack of maintenance and system operation strategy for these underground air condition systems. A promising potential for energy saving was found out within the air conditioning systems in Beijing subway stations.

  • 69. Pan, Song
    et al.
    Du, Saisai
    Wang, Xinru
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Xia, Liang
    Liu, Jiaping
    Pei, Fei
    Wei, Yixuan
    Analysis and interpretation of the particulate matter (PM10 and PM2.5) concentrations at the subway stations in Beijing, China2019In: Sustainable cities and society, ISSN 2210-6707, Vol. 45, p. 366-377Article in journal (Refereed)
    Abstract [en]

    The particulate matters (PM10 and PM2.5) inside urban subway stations greatly influence indoor air quality and passenger comfort. This study aims to analyze and interpret the concentrations of PM10 and PM2.5, measured in several subway stations from October 9th to 22nd, 2016 in Beijing, China. The overall methodology was based on the Statistical Package for Social Science (SPSS) software while General linear model (GLM) and correlation analysis were further applied to examine the sensitivities of different variables to the particle concentrations. The data analysis showed the average overall mass ratio of PM concentrations inside subway station is about 68.7%, much lower than outdoor condition (79.6%). In the areas of the station hall and platform, the real-time PM10 and PM2.5 concentrations varied periodically. In working and operation offices, all rooms had much higher PM concentrations than the outdoor environment when its pollution level was level 3, in which the facility room reached the highest level, while the closed meeting room had the lowest. Correlation analysis results indicated that PM10 and PM2.5 concentrations were mutually correlated (average R2 = 0.854), and a strong linear correlation (R2 = 0.897) of the subway-station PM concentrations to the outdoor PM conditions, regardless of the outdoor atmospheric PM concentrations pollution level was. Nevertheless, the impact of passenger number and temperature & humidity on the station PM concentrations was less, when compared to the outdoor environment. This paper is expected to provide useful information for further research and design of effective prevention measures on PM in local subway stations, towards a more sustainable and healthier built environment in the city underground. 

  • 70.
    Perers, Bengt
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Anderssen, E.
    Nordman, R.
    Kovacs, P.
    A simplified heat pump model for use in solar plus heat pump system simulation studies2012In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 30, p. 664-667Article in journal (Refereed)
    Abstract [en]

    Solar plus heat pump systems are often very complex in design, with sometimes special heat pump arrangements and control. Therefore detailed heat pump models can give very slow system simulations and still not so accurate results compared to real heat pump performance in a system. The idea here is to start from a standard measured performance map of test points for a heat pump according to EN 14825 and then determine characteristic parameters for a simplified correlation based model of the heat pump. By plotting heat pump test data in different ways including power input and output form and not only as COP, a simplified relation could be seen. By using the same methodology as in the EN 12975 QDT part in the collector test standard it could be shown that a very simple model could describe the heat pump test data very accurately, by identifying 4 parameters in the correlation equation found. © 2012 The Authors.

  • 71.
    Perers, Bengt
    et al.
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Kovacs, P.
    Olsson, M.
    Persson, M.
    Pettersson, U.
    A new tool for standardized collector performance calculations2011Conference paper (Refereed)
    Abstract [en]

    A new tool for standardized calculation of solar collector performance has been developed in cooperation between SP Borås Sweden, DTU Denmark and SERC Dalarna University. The tool is designed to calculate the annual performance for a number of representative cities in Europe on the basis of parameters from collector tests performed according to EN12975, without any intermediate conversions. The main target group for this tool is test institutes and certification bodies that intend to use it for conversion of collector model parameters derived from performance tests, into a more user friendly quantity i.e. the annual energy output. Energy output both per m2 and per collector module can be calculated.

  • 72.
    Perers, Bengt
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Kovacs, P.
    Olsson, M.
    Persson, M.
    Pettersson, U.
    A tool for standardized collector performance calculations including PVT2012In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 30, p. 1354-1364Article in journal (Refereed)
    Abstract [en]

    A tool for standardized calculation of solar collector performance has been developed in cooperation between SP Technical Research Institute of Sweden, DTU Denmark and SERC Dalarna University. The tool is designed to calculate the annual performance of solar collectors at representative locations in Europe. The collector parameters used as input in the tool are compiled from tests according to EN12975, without any intermediate conversions. The main target group for this tool is test institutes and certification bodies that are intended to use it for conversion of collector model parameters (derived from performance tests) into a more user friendly quantity: the annual energy output. The energy output presented in the tool is expressed as kWh per collector module. A simplified treatment of performance for PVT collectors is added based on the assumption that the thermal part of the PVT collector can be tested and modeled as a thermal collector, when the PV electric part is active with an MPP tracker in operation. The thermal collector parameters from this operation mode are used for the PVT calculations. © 2012 The Authors.

  • 73.
    Perers, Bengt
    et al.
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Kovacs, P.
    Pettersson, U.
    Experiences and lessons learned from 30 years of dynamic collector testing, modelling and simulation2011Conference paper (Refereed)
    Abstract [en]

    Dynamic testing and modeling (in contrast to Steady State line of action) of solar collectors is to prefer in most climates, except for the most extreme locations with clear skies every day. A very important part of dynamic testing and modeling is not only the thermal capacitance correction, but also the split of the solar radiation absorption modeling, into beam and diffuse and the modeling of the collectors' incidence angle dependency for both beam and diffuse radiation. These optical features are in most situations more important than the accuracy of the dynamic and thermal loss part of the model. This can be seen from the statistical analyze when evaluating test data. The t-ratios i.e. the parameter values divided by their standard deviations, are generally much higher (often 10 times higher) for the optical parameters than for the thermal loss ones. There are also important details concerning solar radiation measurements for beam and diffuse including alignment of sensors and test object, that are often not considered, which will be discussed and lessons learned will be given. A misalignment of just a few degrees of the collector test stand or the solar sensors will immediately show up in a dynamic test evaluation, especially when analyzing the incidence angle modifier behavior and thermal capacitance of a collector. To achieve good results in dynamic testing it is essential to understand the basic concepts of the method and to use this understanding when designing a test rig and collecting data during a test for later analyze. It is very desirable to use a continuous parameter feedback during the test, so that the test conditions can be changed hour by hour to derive more accurate results and shorten the testing time. Such advice will be discussed in the paper. Some of these findings has not yet reached the EN12975 standard level, and suggestions for revisions and improvements will be presented that have general application also for non standardized testing, for example research and development testing.

  • 74.
    Perers, Bengt
    et al.
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Kovacs, P.
    Pettersson, U.
    Björkman, J.
    Martinsson, C.
    Eriksson, J.
    Validation of a dynamic model for unglazed collectors including condensation: Application for standardised testing and simulation in TRNSYS and IDA2011Conference paper (Refereed)
    Abstract [en]

    An improved unglazed collector model has been validated for use in TRNSYS and IDA and also for future extension of the EN12975 collector test standard. The basic model is the same as used in the EN12975 test standard in the QDT dynamic method. In this case with the addition of a condensation term that can handle the operation of unglazed collectors below the dew point of the air. This is very desirable for simulation of recharging of ground source energy systems and direct operation of unglazed collectors together with a heat pump. The basic idea is to have a direct connection between collector testing and system simulation by using the same dynamic model and parameters during both testing and simulation. The model together with the parameters will be validated in each test in this way. This work describes the method applied to an unglazed collector operating partly below the dew point under real dynamic weather conditions, for a long period during the autumn 2010. The validation results also show that the model can handle operation of such a collector during the night. This is a common mode of operation for this collector type in a real system.

  • 75.
    Perez de la Mora, Nicolas
    et al.
    Universidad de las Islas Baleares.
    Bava, Federico
    Technical University of Denmark.
    Andersen, Martin
    Dalarna University, School of Technology and Business Studies, Energy Technology. Chalmers University of Technology.
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Lennermo, Gunnar
    Mälardalens Hogskola.
    Nielsen, Christian
    PanEnergi.
    Furbo, Simon
    Technical University of Denmark.
    Martínes-Moll, Víctor
    Universidad de las Islas Baleares.
    Solar district heating and cooling: A review2017In: International journal of energy research (Print), ISSN 0363-907X, E-ISSN 1099-114X, p. 1-23Article in journal (Refereed)
    Abstract [en]

    Both district heating and solar collector systems have been known and imple- mented for many years. However, the combination of the two, with solar collec- tors supplying heat to the district heating network, is relatively new, and no comprehensive review of scientific publications on this topic could be found. Thus, this paper summarizes the literature available on solar district heating and presents the state of the art and real experiences in this field. Given the lack of a generally accepted convention on the classification of solar district heating systems, this paper distinguishes centralized and decentralized solar district heating as well as block heating. For the different technologies, the paper describes commonly adopted control strategies, system configurations, types of installation, and integration. Real‐world examples are also given to provide a more detailed insight into how solar thermal technology can be integrated with district heating. Solar thermal technology combined with thermally driven chillers to provide cooling for cooling networks is also included in this paper. In order for a technology to spread successfully, not only technical but also eco- nomic issues need to be tackled. Hence, the paper identifies and describes dif- ferent

  • 76. Petrovic, Bojana
    et al.
    Myhren, Jonn Are
    Dalarna University, School of Technology and Business Studies, Construction.
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Wallhagen, Marita
    Eriksson, Ola
    Life cycle assessment of a wooden single-family house in Sweden2019In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 251, p. 113-253, article id 113253Article in journal (Refereed)
    Abstract [en]

    To understand the reasons behind the large environmental impact from buildings the whole life cycle needs to be considered. Therefore, this study evaluates the carbon dioxide emissions in all stages of a single-family house in Sweden from the production of building materials, followed by construction and user stages until the end-of-life of the building in a life cycle assessment (LCA). The methodology applied is attributional life cycle assessment (LCA) based on ‘One Click LCA’ tool and a calculated life span of 100 years. Global warming potential (GWP) and primary energy (PE) are calculated by using specific data from the case study, furthermore the data regarding building materials are based on Environmental Product Declarations (EPDs). The results show that the selection of wood-based materials has a significantly lower impact on the carbon dioxide emissions in comparison with non-wood based materials. The total emissions for this single-family house in Sweden are 6 kg CO 2 e/m 2 /year. The production stage of building materials, including building systems and installations represent 30% of the total carbon dioxide equivalent emissions, while the maintenance and replacement part represents 37%. However, energy use during the in-use stage of the house recorded lower environmental impact (21%) due to the Swedish electricity mix that is mostly based on energy sources with low carbon dioxide emissions. The water consumption, construction and the end-of-life stages have shown minor contribution to the buildings total greenhouse gas (GHG) emissions (12%). The primary energy indicator shows the largest share in the operational phase of the house.

  • 77.
    Poppi, Stefano
    Dalarna University, School of Technology and Business Studies, Energy Technology. KTH.
    Solar heat pump systems for heating applications: Analysis of system performance and possible solutions for improving system performance2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Solar heat pump systems (SHPs) are systems that combine solar energy and heat pumps. SHPs have been investigated for several decades and have been proven to increase the share of renewable energy and reduce electric energy demand in residential heating applications. Many solar thermal heat pump systems have become market-available in recent years; however these systems are still not widely employed in the residential sector. This is due mainly to the high initial costs (investment and installation costs) of solar thermal heat pump systems, which limits their cost-effectiveness. Enhancing cost-effectiveness of solar thermal heat pump systems is necessary for a more effective and broader market penetration.

    In this thesis, solar thermal and photovoltaic systems combined with heat pumps for heating applications are treated. The overall aims of the thesis are to: 1) investigate techno-economics of SHPs and 2) investigate possible solutions for improving system performance of a reference solar thermal and heat pump system for residential heating applications.

    In the first part of the thesis, the influence of climatic boundary conditions on economic performance of SHPs has been investigated by means of: a) an economic comparison of SHPs found in the relevant literature and b) system simulations of the reference solar thermal heat pump system.

    In the second part of the thesis, potential solutions for improving system performance of the reference solar thermal heat pump system with limited change in system’ costs are investigated. A systematic approach was used for investigating cost-effectiveness of the system improvements in the reference system.

    Based on results of the cost-effectiveness analysis, some of the investigated system improvements were chosen for being included in the design of a novel solar thermal and air source heat pump system concept. The novel system was designed for a house standard with relatively high operating temperatures (55°C/45°C) in the space heating distribution system and for high space heating demand (123 kWh/m2·year). Finally, the thesis ends with a cost-effectiveness analysis of the novel system.

  • 78.
    Poppi, Stefano
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology. Department of Energy Technology, KTH.
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Influence of hydraulics and control of thermal storage in solar assisted heat pump combisystems2014In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 48, p. 946-955Article in journal (Refereed)
    Abstract [en]

    This paper studies the influence of hydraulics and control of thermal storage in systems combined with solar thermal and heat pump for the production of warm water and space heating in dwellings. A reference air source heat pump system with flat plate collectors connected to a combistore was defined and modeled together with the IEA SHC Task 44 / HPP Annex 38 (T44A38) “Solar and Heat Pump Systems” boundary conditions of Strasbourg climate and SFH45 building. Three and four pipe connections as well as use of internal and external heat exchangers for DHW preparation were investigated as well as sensor height for charging of the DHW zone in the store. The temperature in this zone was varied to ensure the same DHW comfort was achieved in all cases. The results show that the four pipe connection results in 9% improvement in SPF compared to three pipe and that the external heat exchanger for DHW preparation leads to a 2% improvement compared to the reference case. Additionally the sensor height for charging the DHW zone of the store should not be too low, otherwise system performance is adversely affected

  • 79.
    Poppi, Stefano
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology. KTH.
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Haller, Michel Y.
    University of Applied Sciences HSR, Switzerland.
    Heinz, Andreas
    Institute of Thermal Engineering, Graz University of Technology.
    Influence of boundary conditions and component size on electricity demand in solar thermal and heat pump combisystems2016In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 162, p. 1062-1073Article in journal (Refereed)
    Abstract [en]

    Solar thermal and heat pump combisystems are used to produce domestic hot water (DHW) and space heating (SH) in dwellings. Many systems are available on the market. For an impartial comparison, a definite level of thermal comfort should be defined and ensured in all systems. This work studied the influence of component size on electricity demand for a state of the art solar thermal and heat pump system. A systematic series of parametric studies was carried out by using TRNSYS to show the impact of climate, load and size of main components as well as heat source for the heat pump. Penalty functions were used to ensure that all variations provided the same comfort requirements. Two reference systems were defined and modelled based on products on the market, one with ambient air and the other with borehole as heat source for the heat pump. The results show that changes in collector area from 5 to 15 m2 result in a decrease in system electricity of between 305 and 552 kW h/year. Changes in heat exchanger size for DHW preparation were shown to give nearly as large changes in electricity use due to the fact that the set temperature in the store was changed to give the same thermal comfort in all cases. Decrease in heat pump size was shown to give a decrease in electricity use for the ASHP in the building with larger heat demand while it increased or had only a small change for other boundary conditions. Heat pump losses were shown to be an important factor highlighting the importance of modelling this factor explicitly

  • 80.
    Poppi, Stefano
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology. KTH.
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Heinz, Andreas
    Hengel, Franz
    Cheze, David
    Mojic, Igor
    Cialani, Catia
    Dalarna University, School of Technology and Business Studies, Economics.
    Analysis of system improvements in solar thermal and air source heat pump combisystems2016In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 173, p. 606-623Article in journal (Refereed)
    Abstract [en]

    A solar thermal and heat pump combisystem is one of many system alternatives on the market for supplying domestic hot water (DHW) and space heating (SH) in dwellings. In this study a reference solar thermal and air source heat pump combisystem was defined and modelled based on products available on the market. Based on the results of an extensive literature survey, several system variations were investigated to show the influence of heat pump cycle, thermal storage and system integration on the use of electricity for two houses in the climates of Zurich and Carcassonne. A singular economic cash flow analysis was carried out and the “additional investment limit” of each system variation was determined for a range of economic boundary conditions. This is the maximum extra investment cost for the system variant compared to the reference system that will give a break even result for a 10 year period. The results show that variations in electricity price affects the additional investment limit far more than the other economic parameters. Several of the variants show potential for achieving a cost benefit, but the potential varies a lot depending on load and climate boundary conditions. For all variants, the biggest difference in electricity savings was found for Zurich rather than in Carcassonne, which is explained by the larger heating load. However, in three cases the largest savings were for the SFH45 house despite the fact that the annual electricity use of the system is much lower than that for the SFH100 house, 3581 kW h/year compared to 8340 kW h/year. This was attributed to the fact that, in these cases, the operating level of the space heating circuit played a significant role, the SFH45 house being supplied with a 35/30 °C heating system while the SFH100 was supplied with a 55/45 °C heating system.

  • 81.
    Psimopoulos, Emmanouil
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Bee, E.
    Luthander, R.
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Smart control strategy for PV and heat pump system utilizing thermal and electrical storage and forecast services2017Conference paper (Refereed)
  • 82.
    Psimopoulos, Emmanouil
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology. Uppsala University.
    Bee, Elena
    University of Trento, Trento, Italy.
    Luthander, Rasmus
    Uppsala University.
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Smart control strategy for PV and heat pump system utilizing thermal and electrical storage and forecast services2017Conference paper (Refereed)
    Abstract [en]

    In this study, a detailed model of a single-family house with exhaust air heat pump, PV system and energy hub developed in the simulation software TRNSYS 17 is used to evaluate energy management algorithms that utilize weather and electricity price forecasts. A system with independent PV and heat pump is used as a base case. The proposed control strategy is applied to the base case to optimize the available PV electricity production using short-term weather and electricity price forecasts. The three smart and predictive control algorithms were developed with the scope to minimize final energy by the use of the thermal storage of the building, the hot water tank and electrical storage. The results show reduction of the final energy of 26.4%, increase of the self-consumption to 60% and decrease of the annual cost of 15% when using the forecast services in combination with thermal and electrical storage compared to the base case.

  • 83.
    Psimopoulos, Emmanouil
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology. Uppsala University.
    Bee, Elena
    Widén, Joakim
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Techno-economic analysis of control algorithms for an exhaust air heat pump system for detached houses coupled to a photovoltaic system2019In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 249, p. 355-367Article in journal (Refereed)
    Abstract [en]

    Operational control strategies for the heating system and “smart” utilization of energy storage were developed and analyzed in a simulation based case study of a single-family house with exhaust air heat pump and photovoltaic system. Rule based control algorithms that can easily be implemented into modern heat pump controllers were developed with the aim to minimize final energy and maximize self-consumption by the use of the thermal storage of the building, the hot water tank and electrical storage. Short-term weather and electricity price forecasts are used in some of the algorithms. Heat supply from an exhaust air heat pump is limited by the ventilation flow rate fixed by building codes, and compact systems employ an electric heater as backup for both space heating and hot water. This heater plays an important role in the energy balance of the system. A typical system designed for new detached houses in Sweden was chosen for the study. This system, together with an independent photovoltaic system, was used as a base case and all results are compared to those for this base case system. TRNSYS 17 was used to model the building and system as well as the control algorithms, and special care was taken to model the use of the backup electric heater as this impacts significantly on final energy use. Results show that the developed algorithms can reduce final energy by 5–31% and the annual net cost for the end user by 3–26%, with the larger values being for systems with a battery storage. Moreover, the annual use of the backup electric heater can be decreased by 13–30% using the carefully designed algorithms.

  • 84.
    Ramírez Villegas, Ricardo
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology. University of Gävle.
    Eriksson, O.
    Olofsson, T.
    Life cycle assessment of building renovation measures–trade-off between building materials and energy2019In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, no 3, article id 344Article in journal (Refereed)
  • 85.
    Rönnelid, Mats
    et al.
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Wik, Tina
    Träbyggande och energieffektivt byggande i Tyskland, Österrike och Lichtenstein: Rapport från Forum Holzbau09 och en studieresa i december 20092010Report (Other academic)
  • 86.
    Schnabel, Thomas
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Use of Photovoltaic on an E-bike?: A Feasibility Study2013Independent thesis Advanced level (degree of Master (One Year)), 12 credits / 18 HE creditsStudent thesis
    Abstract [en]

    In recent years the number of bicycles with e-motors has been increased steadily. Within the pedelec – bikes where an e-motor supports the pedaling – a special group of transportation bikes has developed. These bikes have storage boxes in addition to the basic parts of a bike. Due to the space available on top of those boxes it is possible to install a PV system to generate electricity which could be used to recharge the battery of the pedelec. Such a system would lead to grid independent charging of the battery and to the possibility of an increased range of motor support. The feasibility of such a PV system is investigated for a three wheeled pedelec delivered by the company BABBOE NORDIC.The measured data of the electricity generation of this mobile system is compared to the possible electricity generation of a stationary system.To measure the consumption of the pedelec different tracks are covered, and the energy which is necessary to recharge the bike battery is measured using an energy logger. This recharge energy is used as an indirect measure of the electricity consumption. A PV prototype system is installed on the bike. It is a simple PV stand alone system consisting of PV panel, charge controller with MPP tracker and a solar battery. This system has the task to generate as much electricity as possible. The produced PV current and voltage aremeasured and documented using a data logger. Afterwards the average PV power is calculated. To compare the produced electricity of the on-bike system to that of a stationary system, the irradiance on the latter is measured simultaneously. Due to partial shadings on the on-bike PV panel, which are caused by the driver and some other bike parts, the average power output during riding the bike is very low. It is too low to support the motor directly. In case of a similar installation as the PV prototype system and the intention always to park the bike on a sunny spot an on-bike system could generate electricity to at least partly recharge a bike battery during one day. The stationary PV system using the same PV panel could have produced between 1.25 and 8.1 times as much as the on-bike PV system. Even though the investigation is done for a very specific case it can be concluded that anon-bike PV system, using similar components as in the investigation, is not feasible to recharge the battery of a pedelec in an appropriate manner. The biggest barrier is that partial shadings on the PV panel, which can be hardly avoided during operation and parking, result in a significant reduction of generated electricity. Also the installation of the on-bike PV system would lead to increased weight of the whole bike and the need for space which is reducing the storage capacity. To use solar energy for recharging a bike battery an indirect way is giving better results. In this case a stationary PV stand alone system is used which is located in a sunny spot without shadings and adjusted to use the maximum available solar energy. The battery of the bike is charged using the corresponding charger and an inverter which provides AC power using the captured solar energy.

  • 87.
    Selva Marti, Salvador
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Aerial Thermography Inspections in Large-Scale PV Plants2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In order to successfully compete against the use of fossil fuels to generate electricity, one of the challenges in the photovoltaic (PV) business currently in focus is on the asset management of large PV plants, in which developing control techniques to prognosticate and evaluate the future energy performance will be essential. Infrared thermography inspections can give meaningful support to assess the quality and performance of PV modules. However, the implementation of a cost-effective method to scan and check huge PV plants represents different challenges, such as the cost and time of detecting PV module defects with their classification and exact localization within the solar plant. In this context, it has recently been investigated the potential of a new innovative technology in the PV plants monitoring operations by using drones.

    The main purpose of this work is to establish a scientific basis for the interpretation of thermographic images taken by drones, in particular, regarding the influence of thermographic irregularities which will negatively influence the performance of PV plants.

    The drone is employed to monitor PV modules conditions by using special thermography sensors mounted on it in order to scan images. The captured images are then automatically sent to a technical office database for the image processing software. This special software receives, stores and analyses the captured images to detect the specific defect on the PV modules. Then, all information is processed and reported to the final decision-making team to decide about the best solution for the particular degraded PV module, in relation with the requirements from the operation and maintenance (O&M) services.

    In this particularly study project of the inspected PV plant situated in the UK, which has been carried out by trained personnel at Quintas Energy (QE), the majority of identified faults, which influence the PV module performance (especially the power output significantly), are on a sub-panel level, either individual cells or uneven hot spots. There are also some modules with bypass diode faults as well as a string fault was detected. Such faults must be repaired by the PV module manufacturer, in relation to the manufacturer’s warranties, without any cost at all since the PV modules are indeed still in warranty.

    It has been concluded that, in comparison with traditional manned systems by using hand-held cameras, the main functionality of using drones is the early fault diagnosis which could reduce corrective maintenance activities, since defects are easily and quickly identified and, then, repaired. This fact could reduce defects to become more serious and, thus, more difficult to be repaired, along with their correspondent production losses and costs.

    QE has learned by making mistakes during this project study and gained experience of this unmanned aerial vehicles (UAV) technology. Currently, they are in the process of improving this technique and will continue to implement it to all their PV plants since the efficiency of PV systems can be significantly improved by appropriate use of O&M instruments and benefit from innovative monitoring tools, such as the unmanned aerial technology.

  • 88. Sotnikov, A.
    et al.
    Nielsen, C. K.
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Dalenbäck, J. -O
    Andersen, Martin
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Psimopoulos, Emmanouil
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Simulations of a Solar-Assisted Block Heating System2017Conference paper (Refereed)
  • 89.
    Tjäder, Jonas
    et al.
    STRI.
    Ackeby, Susanne
    STRI.
    Bastholm, Caroline
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    The role and interaction of microgrids and centralized grids in developing modern power systems2016Conference paper (Refereed)
  • 90.
    Täubert, Henry
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Analysis of an Existing Solar Thermal DHW System of a Multifamily House in Germany2015Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This study was conducted to investigate operational problems of a larger solar thermal plant (> 100m²) supporting

    domestic hot water (DHW) preparation. Already at the beginning of the 15 years of operation effective solar gains

    fell beyond the T-SOL pre-simulated figures. In addition to that collectors were found leaking after 10 years. The

    aim of the study was also to determine the causes for damaged collectors and to deliver improvement suggestions

    if applicable. The solution was approached by a set of different methods. Literature review and analysis of plans,

    notes and documents of the plant were accompanied by measurements and (re)-calculations and site visits.

    Problems in different sectors of the plant were found. In the secondary circuit, the pump action of the heat

    exchange station was permanent instead of a recommended on demand action. In terms of the DHW preparation

    the lower DHW store sensor was placed in DHW circulation pipe instead of inside the store. In the primary circuit

    the size of the expansion vessel was designed to small. The conception of the solar circuit and the application of

    safety valving were not appropriate in terms of a partial evaporation system. Essential temperature differences

    among collector cases could be attributed to incorrect assigned sensor characteristics in the system control panel.

    Therefore the solar pump was not regulated well, which led to stagnation and overheating. The boiling of solar

    fluid caused the safety valves to blow off and might have led to a loss of the fluids frost protection characteristics.

    During the study, it was asserted that the system design as much as its implementation and maintenance (regularity

    and intensity) were insufficient and led to irreversible plant damage. Different system improvements depending on

    effort can be concluded from that. One example would be the adaption of layout of the existing system to the

    requirements of a partial evaporation system whereas the number of collectors remains the same. Amongst others

    the complete replacement of the plant is discussed.

  • 91.
    Wallin, Elisabeth
    Dalarna University, School of Technology and Business Studies, Energy Technology. SLU.
    From growth cessation to bud burst: conifer seedling development in response to nursery culture and environmental stimuli2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In Sweden, 350-400 million seedlings are produced annually for forest regeneration. About one third of these are overwintered in frozen storage, necessitating accurate methods to assess storability. Young transplants of Norway spruce (Picea abies (L.) Karst.) intended for short-term frozen storage were considered storable before reaching target levels for safe storage using shoot dry matter content, freezing tolerance and the molecular test ColdNSure™. Results also indicated that using shoot dry matter content for storability assessment can be misleading, not only for Norway spruce but also for Scots pine (Pinus sylvestris (L.)). Post-storage vitality can easily and rapidly be determined by measuring the electrolyte leakage from shoots (SEL) of pine and spruce seedlings. SEL and regrowth tests showed that the vitality of young transplants decreased when the time in storage was prolonged from 3-4 to 5-7 months. Short-day (SD) treatment of seedlings shortens the time for dormancy induction and makes seedlings storable at an earlier date. The activity level of dormancy related genes, and genes associated with freezing tolerance reflects the effect of different treatments e.g., the importance of combining longer periods of SD treatment (21-28 days) with low temperature exposure to rapidly obtain storable seedlings. Gene expression profiles have the potential to be used for assessment of seedling dormancy status, predict the development of freezing tolerance, bud set, the risk for a second bud flush in autumn and the timing of bud burst in spring. The interest in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) has increased in Sweden. Frost risks in spring make bud burst timing important when selecting suitable provenances of Douglas-fir for planting. A field trial and a greenhouse study showed the same pattern concerning time of bud burst for a number of Douglas-fir provenances, indicating that greenhouse screening tests can be used for provenance selection. Considering bud burst patterns together with previously reported winter hardening characteristics the interior provenance Three Valley would have a good chance of successful field establishment in southern Sweden.

  • 92.
    Weiss, Philipp
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Energy savings potential in existing houses: Energy simulation results for Dalarna's single-family housing stock2012Report (Other academic)
  • 93.
    Weiss, Philipp
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Simple Question, Complex Answer: Pathways Towards a 50% Decrease in Building Energy Use2014Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Addressing building energy use is a pressing issue for building sector decision makers across Europe. In Sweden, some regions have adopted a target of reducing energy use in buildings by 50% until 2050. However, building codes currently do not support as ambitious objectives as these, and novel approaches to addressing energy use in buildings from a regional perspective are called for. The purpose of this licentiate thesis was to provide a deeper understanding of most relevant issues with regard to energy use in buildings from a broad perspective and to suggest pathways towards reaching the long-term savings objective. Current trends in building sector structure and energy use point to detached houses constructed before 1981 playing a key role in the energy transition, especially in the rural areas of Sweden. In the Swedish county of Dalarna, which was used as a study area in this thesis, these houses account for almost 70% of the residential heating demand. Building energy simulations of eight sample houses from county show that there is considerable techno-economic potential for energy savings in these houses, but not quite enough to reach the 50% savings objective. Two case studies from rural Sweden show that savings well beyond 50% are achievable, both when access to capital and use of high technology are granted and when they are not. However, on a broader scale both direct and indirect rebound effects will have to be expected, which calls for more refined approaches to energy savings. Furthermore, research has shown that the techno-economic potential is in fact never realised, not even in the most well-designed intervention programmes, due to the inherent complexity of human behaviour with respect to energy use. This is not taken account of in neither current nor previous Swedish energy use legislation. Therefore an approach that considers the technical prerequisites, economic aspects and the perspective of the many home owners, based on Community-Based Social Marketing methodology, is suggested as a way forward towards reaching the energy savings target.

  • 94.
    Wilson, Jason Clifford
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    A techno-economic environmental approach to improving the performance of PV, battery, grid-connected, diesel hybrid energy systems: A case study in Kenya2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Backup diesel generator (DG) systems continue to be a heavily polluting and costly solution for institutions with unreliable grid connections. These systems slow economic growth and accelerate climate change. Photovoltaic (PV), energy storage (ES), grid connected, DG – Hybrid Energy Systems (HESs) or, PV-HESs, can alleviate overwhelming costs and harmful emissions incurred from traditional back-up DG systems and improve the reliability of power supply. However, from project conception to end of lifetime, PV-HESs face significant barriers of uncertainty and variable operating conditions. The fit-and-forget solution previously applied to backup DG systems should not be adopted for PV-HESs.

    To maximize cost and emission reductions, PV-HESs must be adapted to their boundary conditions for example, irradiance, temperature, and demand. These conditions can be defined and monitored using measurement equipment. From this, an opportunity for performance optimization can be established. The method demonstrated in this study is a techno-economic and environmental approach to improving the performance of PV-HESs. The method has been applied to a case study of an existing PV-HES in Kenya. A combination of both analytical and numerical analyses has been conducted. The analytical analysis has been carried out in Microsoft Excel with the intent of being easily repeatable and practical in a business environment. Simulation analysis has been conducted in improved Hybrid Optimization by Genetic Algorithms (iHOGA), which is a commercially available software for simulating HESs.

    Using six months of measurement data, the method presented identifies performance inefficiencies and explores corrective interventions. The proposed interventions are evaluated, by simulation analyses, using a set of techno-economic and environment key performance indicators, namely: Net Present Cost (NPC), generator runtime, fuel consumption, total system emissions, and renewable fraction. Five corrective interventions are proposed, and predictions indicate that if these are implemented fuel consumption can be reduced by 70 % and battery lifetime can be extended by 28 %, net present cost can be reduced by 30 % and emissions fall by 42 %. This method has only been applied to a single PV-HES; however, the impact this method could have on sub-Saharan Africa as well as similar regions with unreliable grid connections is found to be significant. In the future, in sub-Saharan Africa alone, over $500 million dollars (USD) and 1.7 billion kgCO2 emissions could be saved annually if only 25 % of the fuel savings identified in this study were realized. The method proposed here could be improved with additional measurement data and refined simulation models. Furthermore, this method could potentially be fully automated, which could allow it to be implemented more frequently and at lower cost.

  • 95.
    Zare, Kourosh Abbas
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Development of a Predictive Control Model for a Heat Pump System Based on Artificial Neural Networks (ANN) approach2019Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
  • 96. Zhang, Nan
    et al.
    Chen, Xiangjie
    Su, Yuehong
    Zheng, Hongfei
    Ramandan, Omar
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Chen, Hongbin
    Riffat, Saffa
    Numerical investigations and performance comparisons of a novel cross-flow hollow fiber integrated liquid desiccant dehumidification system2019In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 182, p. 1115-1131Article in journal (Refereed)
    Abstract [en]

    The heat and mass transfer process of a novel cross-flow hollow fiber integrated liquid desiccant dehumidification system is analysed numerically. Compared with other porous media or packing towers in dehumidification applications, hollow fibre membranes have significant advantages including low weight, corrosion resistant and no liquid droplet carryover. A novel air-KCOOH cross-flow dehumidification system was designed and manufactured, with 5500 hollow fibres formed into a circular module. The variations of the dehumidification effectiveness and moisture removal rates were studied numerically and validated against experimental results under the incoming air mass flow rates of 0.08-0.26kg/s and relative humidity from 55% to 75%. The dehumidification performance comparisons for the proposed system using CaCl2, LiCl and KCOOH as the desiccants have been conducted as well. The results demonstrated that under the same m*(ratio between solution mass flow rate to the air mass flow rate), the proposed system using 62% KCOOH could achieve approximately the same latent effectiveness compared with 40% CaCl2 and 32% LiCl, with the at least 3.1% sensible effectiveness increased by. Therefore, it could be concluded that the proposed system using KCOOH as desiccant could be more applicable for dehumidification purpose compared with other systems using conventional liquid desiccants.

  • 97.
    Ålander, Atte
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Electricity Supply Solutions for an Educational Center in Tanzania2013Independent thesis Advanced level (degree of Master (One Year)), 12 credits / 18 HE creditsStudent thesis
    Abstract [en]

    The aim of this study was to investigate electricity supply solutions for an educationalcenter that is being built in Chonyonyo Tanzania. Off-grid power generation solutions andfurther optimization possibilities were studied for the case.The study was done for Engineers Without Borders in Sweden. Who are working withMavuno Project on the educational center. The school is set to start operating in year 2015with 40 girl students in the beginning. The educational center will help to improve genderequality by offering high quality education in a safe environment for girls in rural area.It is important for the system to be economically and environmentally sustainable. Thearea has great potential for photovoltaic power generation. Thus PV was considered as theprimary power generation and a diesel generator as a reliable backup. The system sizeoptimization was done with HOMER. For the simulations HOMER required componentdata, weather data and load data. Common components were chose with standardproperties, the loads were based on load estimations from year 2011 and the weather datawas acquired from NASA database. The system size optimization result for this base casewas a system with 26 kW PW; 5.5 kW diesel generator, 15 kW converter and 112 T-105batteries. The initial cost of the system was 55 875 €, the total net present cost 92 121 €and the levelized cost of electricity 0.264 €/kWh.In addition three optimization possibilities were studied. First it was studied how thesystem should be designed and how it would affect the system size to have night loads(security lights) use DC and could the system then be extended in blocks. As a result it wasfound out that the system size could be decreased as the inverter losses would be avoided.Also the system extension in blocks was found to be possible. The second study was aboutinverter stacking where multiple inverters can work as one unit. This type of connectionallows only the required number of inverters to run while shutting down the excess ones.This would allow the converter-unit to run with higher efficiency and lower powerconsumption could be achieved. In future with higher loads the system could be easilyextendable by connecting more inverters either in parallel or series depending on what isneeded. Multiple inverters would also offer higher reliability than using one centralizedinverter. The third study examined how the choice of location for a centralized powergeneration affects the cable sizing for the system. As a result it was found that centralizedpower generation should be located close to high loads in order to avoid long runs of thickcables. Future loads should also be considered when choosing the location. For theeducational center the potential locations for centralized power generation were found outto be close to the school buildings and close to the dormitories.

  • 98.
    Šumić, Mersiha
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Thermal Performance of a Solarus CPC-Thermal Collector2014Independent thesis Advanced level (degree of Master (One Year)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    The  aim  of  this  master  thesis  is  an  investigation  of  the  thermal  performance  of  a  thermal compound parabolic concentrating (CPC) collector from Solarus. The collector consists of two troughs with absorbers which are coated with different types of paint with  unknown  properties.  The  lower  and  upper  trough  of  the  collector  have  been  tested individually.

    In  order  to  accomplish  the  performance  of  the  two  collectors,  a  thorough  literature  study  in  the  fields  of  CPC  technology,  various  test  methods,  test  standards  for  solar thermal  collectors  as  well  as  the  latest  articles  relating  on  the  subject  were  carried  out. In addition, the set‐up of the thermal test rig was part of the thesis as well. The thermal  performance  was  tested  according  to  the  steady  state  test  method  as  described in the European standard 12975‐2. Furthermore, the thermal performance of  a  conventional  flat  plate  collector  was  carried  out  for  verification  of  the  test  method.

    The  CPC‐Thermal  collector  from  Solarus  was  tested  in  2013  and  the  results  showed  four  times  higher  values  of  the  heat  loss  coefficient  UL (8.4  W/m²K)  than  what  has been reported for a commercial collector from Solarus. This value was assumed to be too large and it was assumed that the large value was a result of the test method used that time. Therefore, another aim was the comparison of the results achieved in this work with the results from the tests performed in 2013.

    The results of the thermal performance showed that the optical efficiency of the lower trough of the CPC‐T collector is 77±5% and the corresponding heat loss coefficient UL 4.84±0.20  W/m²K.  The  upper  trough  achieved  an  optical  efficiency  of  75±6  %  and  a  heat loss coefficient UL of 6.45±0.27 W/m²K. The results of the heat loss coefficients  are  valid  for  temperature  intervals  between  20°C  and  80°C.  The  different  absorber paintings have a significant impact on the results, the lower trough performs overall better.  The  results  achieved  in  this  thesis  show  lower  heat  loss  coefficients UL and higher optical efficiencies compared to the results from 2013. 

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