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  • 251.
    Rönnelid, Mats
    et al.
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Perers, Bengt
    Karlsson, Björn
    On the factorization of incidence angle modifiers for CPC-collectors1995In: ISES Solar World Congress, Harare, Zimbabwe, 1995Conference paper (Other academic)
  • 252.
    Rönnelid, Mats
    et al.
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Perers, Bengt
    Karlsson, Björn
    Optical properties of nonimaging concentrators with corrugated reflectors1994In: SPIE Optical Materials Technology for Energy Efficiency and Solar Energy Conversion XIII, Freiburg, Germany, 1994Conference paper (Other academic)
  • 253.
    Rönnelid, Mats
    et al.
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Perers, Bengt
    Karlsson, Björn
    Krohn, Peter
    Cooling of PV modules equipped with low-concentrating CPC reflectors1999In: ISES Solar World Congress, Jerusalem, Israel, 1999Conference paper (Other academic)
  • 254.
    Rönnelid, Mats
    et al.
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Perers, Bengt
    Krohn, Peter
    Spante, Lennart
    Karlsson, Björn
    Active cooling of low-concentrating hybrid PV/Thermal collectors1999In: North Sun, Edmonton, Canada, 1999Conference paper (Other academic)
    Abstract [en]

    A series of measurements on the performance of solar cell string modules with low-concentrating CPC reflectors with a concentration factor C ˜ 4X have been carried out. To minimise the reduction in efficiency due to high cell temperatures, the modules were cooled. Four different way of cooling were tested: 1) The thermal mass of the module was increased, 2) passive air cooling was used by introducing a small air gap between the module and the reflector, 3) the PV cells were cooled by a large cooling fin, 4) the module was actively cooled by circulating cold water on the back. The best performance was given with the actively cooled PV module which gave 2,2 times the output from a reference module while for the output from the module with a cooling fin the value was 1,8. Active cooling is also interesting due to the possibility of co-generation of thermal and electrical energy which is discussed in the paper. Simulations, based on climate data from Stockholm, latitude 59.4°N, show that there are good prospects for producing useful temperatures of the cooling fluid with only a slightly reduced performance of the electrical fraction of the PV thermal hybrid system.

  • 255.
    Rönnelid, Mats
    et al.
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Perers, Bengt
    Krohn, Peter
    Spante, Lennart
    Karlsson, Björn
    Experimental performance of a string module in a CPC reflector cavity1998In: 2nd World Conf. on Photovoltaic Energy Conversion, Vienna, Austria, 1998Conference paper (Other academic)
    Abstract [en]

    The purpose of the work is to develop a cost effective semistationary CPC concentrator for a string PV-module. A novel method of using annual irradiation distribution diagram projected in a north-south vertical plane is developed. This method allows us easily to determine the optimum acceptance angle of the concentrator and the required number of annual tilts. Concentration ranges of 2-5x are investigated with corresponding acceptance angles between 5 and 15°. The concentrator should be tilted 2-6 times per year. Experiments has been performed on a string module of 10 cells connected in a series and equipped with a compound parabolic concentrator with C = 3.3X. Measurement show that the output will increase with a factor of 2-2.5 for the concentrator module, compared to a reference module without concentrator. If very cheap aluminium reflectors are used the costs for the PV-module can be decreased nearly by a factor of two.

  • 256.
    Rönnelid, Mats
    et al.
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Sonderen, Christiaan
    Asymmetrical awnings: a way to increase daylight in buildings without increasing the overheating2006In: Eurosun 2006, Glasgow, Scotland, 2006Conference paper (Other academic)
    Abstract [en]

    Different shapes of asymmetric awnings for east and west windows are investigated mathematically as well as by measurement in a model. A box with 90 cm side and a 30x30 cm window was placed outdoor in overcast weather and the daylight factor was measured at the bottom of the box when the window was unshaded or equipped with different awnings. The average daylight factor in the box decreased from 4.6% for the unshaded window to 1.0% when a full awning was used. With “the best” asymmetrical awning, the average daylight factor was 80% larger than with the full awing. Using Dutch climate, calculation of the energy from direct radiation transmitted through the window during the cooling season showed that this was decreased from 100% as an annual mean for the unshaded window down 22% with a full awing. With “the best” asymmetrical awning, 26% of the energy was transmitted. Calculation of the indoor temperature in a hypothetical row house in Netherlands show that the use of either normal or asymmetrical awnings considerable decrease the indoor temperature during the hot season. Therefore the use of asymmetrical awnings for east or west faced windows considerable can increase the daylight in buildings, with almost no change in overheating, compared to if traditional awnings are used.

  • 257.
    Rönnelid, Mats
    et al.
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Tepe, Rainer
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Solvärme och värmepump: utvärdering av ett värmesystem i Uppsala2004Report (Other academic)
  • 258.
    Sartori, Igor
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Solar-Pellet Combisystems: A feasibilityStudy in Toscana, Italy2003Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Solar thermal technology, and pellet as well, seem to be on a breakthrough to a scale market. Several barriers hamper their penetration in the society. In this work is demonstrated that non-technical barriers are the most significant. Inte target area, Val d’Orcia, where ETA is developing a project to start a pellet production plant, the feasibility of solar-pellet combisystems is investigated under different points of view. A technological investigation on solar-pellet combisystems demonstrate their technical and economical feasibility. A survey on installers underline the necessity of increasing their knowledge and skills on solar thermal plants via professional courses. A survey on farmtourisms shows that these social actors, due to their perception of solar collectors as unaesthetic, presently are not the suitable vector for diffusion of solar technology as could be expected. The economical accessibility to a solar-pellet combisystem is limited by the relatively high upfront cost. This matter has several directions of improvement. The most significant, in my opinion, is the development of ESCO’s market, which also means development for solar thermal and pellet, RES market in general.

  • 259.
    Satvasheel, Powar
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Characterizing Performance of Dye Sensitized Solar Cells2005Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The present study comprises the fabrication of dye sensitized solar cells (DSC) and evaluating their performance and stability at 60oC under light soaking with 1 sun light irradiation (1000W/m2, AM 1.5). In order to achieve the long-term stability of devices we designed novel low volatile electrolytes containing ionic liquids in combination with high molar extinction coefficient sensitizers. The initial performances of the devices are between 7 and 8% efficiency at one sun light irradiation. Even after keeping these cells under light and thermal stress the devices show excellent stability over 1000 h, retained more than 90% of their initial values.

  • 260. Schubnell, Markus
    et al.
    Gabler, Hansjörg
    Broman, Lars
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Overview of European activities in thermophotovoltaics1997In: Third NREL Conference on Thermophotovoltaic Generation of Electricity, Colorado Springs, CO, USA, 1997Conference paper (Other academic)
    Abstract [en]

    In Europe several research institutes and private companies are currently working or have been working in thermophotovoltaics. At the Solar Energy Research Center SERC in Sweden, the possibility of using wood as a fuel for a TPV-system emphasizing the aspect of co-generation of heat and electricity is investigated. SERC also does work on characterization on TPV cells and on TPV generator optics. The Fraunhofer Institute for Solar Energy Systems in Germany plans to develop a TPV-generator to assure the supply reliability for small off grid photovoltaic systems and in Switzerland the research foundation of the Swiss gas industry has approved a project proposed by the Paul Scherrer Institute to develop a residential TPV-gas-burner for co-generation of heat and electricity. We also report on activities in the United Kingdom as well as on a past research program in the Netherlands.

  • 261. Setterwall, F
    et al.
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Thermo Chemical Accumulator - TCA2003In: Proceedings ISES 2003, Gothenburg, Sweden, 2003Conference paper (Other academic)
  • 262.
    Shamsujjoha, MD
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Maximum Power Point (MPPT) in a Stand-alone System2005Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The electrical power in a stand alone PV system is expensive; generated power should be delivered to battery as much as possible. If the panel can generate more power, this extra power should deliver to the battery. Normally in cold temperature, panel produces more power. The conventional charge controller can not deliver this extra power to the battery. Especial types of charge controller called Maximum Power Point Tracker (MPPT) can extract more power and deliver to the storage. The charge controller is an important device for the power conditioning and controlling of a stand alone system. Nowadays, different types of charge controllers are available in the market - conventional charge controller, MPPT charge controller etc. Some charge controllers have inbuilt MPPT function in order to increase energy gain. If using a MPPT charge controller in a system, the PV module can generated more power by neglecting battery voltage, and it can deliver the maximum power. Typically, in the MPPT charge controller, the generated voltage step down, and at the same time current step up at the same ratio. Thus it can deliver more power. The MPPT regulators are useful in the winter months, in the cloudy or hazy days or when the battery is deeply discharged. The main purpose of this thesis work is to investigate the gain improvement of existing MPPT charge controller and market survey of charge controllers. The experimental work should be performed in cold climate, like Sweden, and with the equipments available here.

  • 263.
    Shresta, Shyam Sundar
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Performance Evaluation od a Concentrator Photovoltaic/Thermal Hybrid Prototype2004Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Concentrator photovoltaic/Thermal (PV/T) hybrid systems produce both electricity and thermal energy; this increases the overall efficiency of the system and reduces the cost of solar electricity. These systems use concentrators which are optical devices that concentrate sunlight onto solar cells and reduce expensive solar cell area.This work deals with the performance evaluation of a concentrator PV/T hybrid system prototype with a single-axis tracking single-mirror two-stage (SMTS) concentrator and a mono-crystalline solar cell string bonded to a thermal receiver. The concentration ratio of system is between 11 and 5.6, and was measured by a customized circuit added to a micrologger instrument. The optical efficiency of the concentrator is 33% and was measured using short-circuit current method. This value is less compared to a SMTS system which has a theoretical maximum optical efficiency of 90%. The average thermal efficiency is 15% and the electrical efficiency is 4.6% under corrected solar concentration ratio of 17.1. The overall energy efficiency of the system is 19.6%. The low efficiency is mainly explained by improper reflector geometry. The prototype’s concentrator was built using geometrical ray tracing which is generally used for drawing conic sections. However, for surfaces other than conic, like SMTS, the surface interaction of the incident rays at two or more points make ray tracing a computationally intensive process and often the surfaces are far away from ideal surface. This work includes a review of current concentrator PV/T hybrid activities which shows that a variety of systems are in use and the combined thermal and electrical efficiency one such system has approached up to 70%. A wide range of concentrator reflector material are available for solar energy use, but long term performance and durability of low cost materials for application in high concentration systems which operates at high temperature need to be studied thoroughly.

  • 264.
    Sohail, Ahmed
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Generation of Electricity by using Thermophotovoltaic Devices with Photonic Techniqes and Combination of Selective Edge Filters2002Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The purpose of this thesis to conduct a research study on manufacturing cones and squared Q-Faberge with reflecting hard paper material with reflectivity approximately 85%, which can have even light distribution at the exit aperture. For the constructions of certain Faberge cones I calculated the specific Faberge curve with the help of mathematical expressions and finally find the equation and draw it on maple computer software. As I was a part of a research group of SERC for TPV so the part of project, I was supposed to do, was to construct cones and squared Quasi-Faberge and check their performance with the help of spectrophotometer and compare the results with previous calculated results of square cornet made with flat mirrors. It must be noted that normal circular curved cones CPC cones which have uneven light distribution and cause hot spot at the exit aperture. Measurements and calculations on silver coated and aluminium coated cones indicated that arrangements with cones having a TPV cell at the exit aperture are technically worthwhile. The concentration depends on the geometry of the cone and the reflector material of the surface. The low cost, compared to PV cells of polished and coated 0.7 mm aluminium makes it probably that the use of cone concentrators would reduce the cost per produced kWh. Factors to take account are higher labour and material costs for manufacturing models.

  • 265.
    Sonderen, Christiaan
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Improved awnings and overhangs for increasing the daylight factor2004Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Light that enters a room through the windows exist of short wavelength radiation (visible radiation) and out long wavelength radiation (thermal radiation). The visible radiation contributes to the increasing of the daylight factor. The thermal radiation contributes to the increasing of the temperature in the room. In the summer the contribution of the thermal radiation may become so big that the room will be overheated. The cheapest option is to reduce the thermal radiation due making use of shading devices. The disadvantage by making use of shading devices is that it not only reduces the thermal radiation but also reduce the visible radiation. This will decrease the daylight factor inside the room. In this work the shape of the awning and overhang is changed to increase the daylight factor without increase the heating due to thermal radiation. Different geometries are studied and daylight measurements are done with help of a scale model. For south faced windows, there is only a little difference between the daylight factor for a rectangular overhang and the daylight factor for a trapezium overhang. Therefore is there not calculated any more with overhangs for south faced windows. However this difference in daylight factor is bigger for the awnings of an east or west faced window. At the same time the amount of energy transmitted through the window is calculated. The best awning for an east or west faced window in the Dutch climate (latitude 52oN) studies show that it is possible to increase the average daylight factor by approximately 80% while the irradiation increase due to reduced shading with only 16%. Calculations have shown a negligible difference in the indoor temperature between the two awnings, although the daylight factor can be increased considerable.

  • 266. Spante, L
    et al.
    Andersson, M
    Perers, B
    Krohn, P
    Helgesson, A
    Karlsson, B
    Setterwall, C.M.
    Gröndalen, O
    Sunér, M
    Holmström, S
    Stolt, L
    Wennerberg, J
    Rönnelid, Mats
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Kjellsson, E
    Selhagen, L
    Sandell, P
    Forssander, M
    Andersson, B
    Ulvönäs, S
    Romero, M.A.
    Solel 97-99. Ett branchgemensamt FoU-program: Årsrapport 19971998Report (Other academic)
  • 267. Spante, L
    et al.
    Andersson, M
    Perers, B
    Krohn, P
    Karlsson, B
    Sunér, M
    Joensen, A
    Dahlöf, P
    Sporrborn, D
    Selhagen, L
    Sandell, P
    Forssander, M
    Stolt, L
    Wennerberg, J
    Rönnelid, Mats
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Kjellsson, E
    Johannesson, C.M.
    Andersson, G
    Romero, M.A.
    Solel 97-99. Ett branchgemensamt FoU-program: Årsrapport 19981999Report (Other academic)
  • 268.
    Sridhar, Gopu
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Simulation Of a solar absorption cooling system for hot climate2002Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    A detailed study of solar absorption cooling has been initiated at European Solar Engineering School, Högskolan Dalarna for the first time. As the initial step, in this work the various absorption technologies are reviewed. A TRNSYS model has been built to size the solar circuit and to find the optimum values for hot water temperature, cooling water temperature and chilled water set point temperatures; to get higher COP and solar faction values. A 650 m2 commercial office building (Bank) is used with TYPE 56 to estimate the cooling load. The cooling load is estimated as approximately 100 KW and Yazaki WFC-30 commercial chiller is selected and the same data is used with the TRNSYS Type 680 (Single effect hot-water fired absorption chiller) in sizing the solar circuit. The optimum value of solar collector area is found as 500 m2 flat plate collector, 6 m3 Storage volume and 80oCof hot water, 15oC Chilled water set point. Same results are achieved with a 250 m2 Evaluated tube collector under the same conditions.

  • 269. Streicher, W.
    et al.
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Chapter 5: Combistores2005In: Thermal energy storage for solar and low energy buildings - State of the art / [ed] Hadorn, J-C., Lleida, Spain: Lleida University , 2005Chapter in book (Other academic)
  • 270. Streicher, W
    et al.
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Bony, J
    Brender, E
    Material Demand and Energy Payback Time of Solar Combisystems2003In: Proceedings ISES 2003, Gothenburg, Sweden, 2003Conference paper (Other academic)
  • 271. Streicher, W
    et al.
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Bony, J
    Heimrath, R
    Elements and Examples of "Dream Systems" of Solar Combisystems2002Report (Other academic)
  • 272.
    Syed, Haseebuddin
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Dynamic Thermal Simulation of Solar Combi-system and Direct Solar Floor Heating System2006Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    A solar combisystem consists of a solar collector, a storage tank along with an auxiliary heater for backup and short term storage facility. Solar combisystem can be a feasible alternative for space heating as well as for Domestic hot water services. Two house types and three system concepts have been simulated in this study. The model includes collector, collector loop, auxiliary heater, bivalent shunt, pumps, heat exchangers, buffer storage tank, control valves and control system. The goal of this study was to improve the system by maximising solar gain and minimizing the auxiliary power and to investigate if there is any possibility for improvements in system with varying different parameters and connecting the collector circuit directly to the floor via an external heat exchanger. An assumption was made that by utilizing the storage capacity of the floor will make it possible to store more solar heat and therefore increase the solar gains and decrease auxiliary energy. Simulations were done with two different houses type A and type B, Type A was a low energy house i.e., a well insulated house and type B was a high energy house or con-ventional house. Both the houses type A and type B were divided into three zones: zone1, zone2, zone3. In this study three system concepts were simulated for comparison purpose, namely the base case sys-tem, the advance control system and the direct solar floor concept. Three parametric variations have been performed in this study for comparison purpose, with two different Buffer storage tanks, with two different collector slopes and with two different comfort criteria’s. The comparative study of these three systems has shown significant improvements in energy savings i.e. increased solar energy utilization and decreased auxiliary energy consumption with the improvements in the control systems. It can be con-cluded from these results that the concrete floor can be utilized to store energy and that with more im-proved control strategies and parametric variations, more and more solar energy can be utilized and more and more auxiliary power can be saved.

  • 273.
    Szever, Istvan
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Solar Heated Outside Pool2005Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    In my thesis work I would like to show the system of heating up an outside swimming pool. - Make essential calculation for the heat demand to heat up the pool. - Try to estimate how many people use the pool. The water replacement need every day. How many collectors should be used for this system. - Choose the necessary system components. - Create the pool plan documentation

  • 274.
    Szmola, Roland
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Collector Testing and Methods2005Independent thesis Advanced level (degree of Master (Two Years))Student thesis
  • 275.
    Tarigan, Elieser
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Design of a Curriculum for a Course on Renewable Energy Suitable for the Faculty of Engineering, University of Surabaya, Indonesia2003Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Consciousness of importance of renewable energy and its possibilities to be developed should be socialised and introduced. It can be done through the formal education, and if it is the teaching curriculum should be designed. It is interesting to know and explore what is going on in the world universities regarding teaching renewable energy. Such surveying had been done by searching through Internet, and for some institutions by contacting the contact persons, to collect information about course and program on renewable energy at the world universities. In this thesis project it is also tried to design a suitable curriculum of a course on renewable energy as an approaching for faculty of engineering of the University of Surabaya, Indonesia. The curriculum consists of course content and lesson plan. It is designed by taking into account the aspects of: Current problems as well as ways and means of developing instrument; scientific knowledge combining natural, physical, and social environments; and the social and cultural needs of the region to provide an adequate and appropriate place for practical work and co-curricular activities. The components of the lesson plan are goals, objectives, prerequisites, materials, lesoon description, lesson procedure, and assessment/evaluation.

  • 276.
    Tejada, Carlos
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Solar design for cooling and heating with TCA for Demonican Republic (tropical climates)2004Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The DB 220 is a new technology that provides cooling and heating with the use of solar energy or other sources of heat. It has the ability to store energy for operation conditions; this technology is being developed by Climate Well is Sweden. One of the aims of this work is to size a system that can provide cooling for a house in tropical climates. This was done by selecting external components (fan coils, solar collectors and dry coolers) integrated to the DB 220 using specialised software together with correlation equations of version of the Climate Well machine. The system comprises separate fan coil units for each of the rooms to be cooled, two dry coolers and 20 m2 solar collector. This calculation does not take into account the total required load during the design day, only the design condition, and implicity assumes that if the energy collected from the collector field and stored in the DB 220 machine is not sufficient, heat is supplied from another source. The other aim was to take measurements with DB 220 installed at SERC (Borlänge, Sweden) in order to compare them to results given by the manufacturer. Measurements were acquired over a period of 5 days. The results of these measurements prove that the tested DB 220 is machine performed unreliably and that the steady state performance was worse than that stated by the manufacturer. The main causes of the problems were loss of vacuum and unwanted crystallization.

  • 277. Tepe, R.
    et al.
    Lorenz, Klaus
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Façade and Roof Integrated Solar Collectors with a Combination of Elastomer Tubes and Metal Form Sheet Elements. System Concepts and Simulation: Technical Report EU-Project JOR3-CT98-02362000Report (Other academic)
  • 278. Tepe, R.
    et al.
    Lorenz, Klaus
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Swan, T.
    Bartelsen, B.
    Rockendorf, G.
    Heusel, H.
    Pasberg, H.
    Façade and Roof Integrated Solar Collectors with a Combination of Elastomer Tubes and Metal Form Sheet Elements. Absorber Form Sheet Production: Technical Report EU-Project JOR3-CT98-02362000Report (Other academic)
  • 279.
    Tepe, Rainer
    et al.
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Rönnelid, Mats
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Solfångare och värmepump: Marknadsöversikt och preliminära simuleringsresultat2002Report (Other academic)
  • 280. Tepe, Rainer
    et al.
    Rönnelid, Mats
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Perers, Bengt
    Swedish solar systems in combinations with heat pumps2003In: ISES World Congress, Gothenburg, 2003Conference paper (Other academic)
  • 281. Thür, Alexander
    et al.
    Furbo, Simon
    Fiedler, Frank
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Development of a Compact Solar Combisystem2006In: Eurosun 2006, Glasgow, UK, 2006Conference paper (Other academic)
    Abstract [en]

    Within the frame of the project REBUS, "Competitive solar heating systems for residential buildings", which is financed by Nordic Energy Research, a new type of compact solar combisystem with high degree of prefabrication was developed. A hydraulic and control concept was designed with the goal to get highest system efficiency for use with either a condensing natural gas boiler or a pellet boiler. Especially when using the potential of high peak power of modern condensing natural gas boilers, a new operation strategy of a natural gas boiler/solar combisystem can increase the energy savings of a small solar combisystem by about 80% compared to conventional operation strategies.

  • 282.
    Upadhyay, Kiran Kumar
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Low scale irrigation system in terraced mountain sites for agricultural production at rural areas of Nepal2005Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Low scale solar irrigation systems have shown their potential in rural irrigation projects around the world, especially where there is no grid connection and no transportation facility. With continuing price decreasing of solar module and solar pump due to market competition, they are becoming economically attractive and growing experiences is gained in irrigation such as low scale multistage irrigation, medium head and high head irrigation system. There is still lack of information although it has wide scope. The main purpose of this study is to contribute to a better understanding of the potential of low scale solar pump to deliver water at different height distributing equal power from a small Photovoltaic panel according to interlock system of the pumps. It is, in fact, of paramount importance to identify the potential contribution of solar irrigation system for rural development in order to gain further financial commitment for low scale irrigation projects and program and to design appropriate solar irrigation projects for terrace field. It helps to provide the option for irrigation facility for terrace field in Nepal. One of the main lessons learnt through this study is that the pay back period is very short and there are no maintenances for the system also. It is hoped that this document contributes to the generation of ideas and discussions among the different institutions involved in providing low scale multistage solar irrigation services to rural area.

  • 283.
    Ureta, Maite Butragueno
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Thermosyphon Solar Charging Unit2005Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The thesis research and development have been carried out in the Technical University of Denmark in Copenhagen. The solar combisystem of the REBUS project will have a plate heat exchanger for transferring the solar energy from the collector loop to the solar store. Based on previous investigations at DTU, the heat exchanger might operate without a pump in the secondary loop, driven just by thermal forces between cold and hot water. The purpose of this study is to calculate the hydraulic loop of a thermosyphon system. Theoretical and experimental investigations have been carried out in order to find out all the important parameters of the secondary loop of the system that consists basically of a tank and a plate heat exchanger. First of all, a theoretical study of how to calculate a thermal driven hydraulic loop for different boundary conditions has been done. Then a test stand has been built up and it has been tested under typical operating conditions in a solar thermal system. A further study to find out the pressure droå of the heat exchanger has been done. In order to carry out all this research, an Excel tool has been developed.This Excel tool calculates the hydraulic loop from some necessary basic input data. The final goal of that tool is to calculate the “?” value of the heat exchanger, necessary to calculate the entire secondary hydraulic loop. The above mentioned tool will be very useful for the REBUS project and for future studies of thermosyphon systems since it will make it easier to calculate all the important parameters of the hydraulic loop.

  • 284.
    van Wieringen, Bastiaan Alexander
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Control Strategy for a Solar Combisystem2004Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The purpose of this thesis was to design a control strategy for a solar combi-system. This combi-system has two storage tanks, one for floor heating and one for domestic hot water, but it has only one auxiliary heater. The purpose of the research was to find a control strategy in order to make the best use of this single auxiliary heater, but this goal has been adapted. In the first chapter, Introduction, the framework of projects surrounding this thesis is outlined; this thesis forms a part of the research done in the Rebus project. It is directly linked to three of Rebus’ participants; SERC, UiO and SolarNor. Furthermore is the main goal stated and it is explained why it has been slightly altered. This change of goal makes Chapter 3 the back bone of this thesis, instead of Chapter 5 and 6 what might be expected judging from the title. The second chapter, System description, starts with a general overview of solar heating systems. Then a more specific description of the analysed system is given. This second part emphasizes on place and type of sensors and the measurements that are done. The third chapter, Submerged buoyant jet, forms the center point of this thesis. The submerged buoyant jet forms a very important passive control mechanism in the whole system. An analytical analysis based on literature and publications was used and validated with measurements. It turned out that the buoyant behaviour does not have an substantial contribution to the heat exchange of this jet. It is proven that the heat exchange is mainly caused by forced convection. A crude mathematical model is proposed. The fourth chapter, Immersed DHW tank with internal heat exchanger, was supposed to have a model for the thermal behaviour of the immersed DHW store as the outcomming. This goal it not reached to a satisfying level, due to practical limitation. The practical limitations are outlined and recommendations are made to improve the model. In the fifth chapter, System model, the proposed models of Chapters 3 and 4 are implied in Matlab Simulink and are simulated. It shows that the models do not resemble the system behaviour. Recommendations are made for improvements. The sixth chapter, Control strategy, contains only recommendations, due to the lack of a proper model. The recommendations are made for the on/off control strategy that SolarNor wants to implement. The seventh chapter, Conclusions and recommendations, outlines once more the conclusions and recommendations of the previous chapters.

  • 285.
    Vlooswijk, Ard
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Experimenting with the sun: Experiments for the exhibition "Nedkalla solkraften!" at the Museum of Science and Technology in Stockholm2003Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The main aim of this thesis work was to develop, test and build good, simple solar energy experiments to illustrate the possibilities of solar energy. These experiments should support the exhibition “Nedkalla solkraften” by showing the possibilities and different forms of solar in “hands on” experiments. The main aim has been reached, mainly illustrated by the fact that - the experiments are good representations of solar energy technology, even showing the problems encountered with these techniques in practice; - a cheap good-working dye-sensitized solar cell demonstration has been developed; - existing experiments have been efficiently implemented (like the s(ch)olar collector); - standard manual were made; - the whole process has been performed within the financial outline set by the Tekniska Museet But of course there were also some problems, like - there was not enough knowledge about the environment in which the experiments were going to be used; - not all experiments were robust enough; - the standard manuals contained too much (complicated) text and too few illustrations to be used easily; - the time to develop and build the experiments was not very long; - the evaluation of the exhibition is not reliable, because too few questionnaires were handed out and returned. The penultimate problem is one of the main causes that no advanced testing has been performed. After implementation, it seemed that it might have been interesting to compare “research results” with field results. This in order to see how easy experiments are to reproduce. Based on this “lack of research”, it can be said that this thesis work was maybe too much demand-led (experiments finished in time) and not so much scientific interest-led. A lot of practical problems of solar energy were encountered but not quantitatively investigated.

  • 286. Wennerberg, J
    et al.
    Kessler, J
    Hedström, J
    Stolt, L
    Karlsson, B
    Rönnelid, Mats
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    CIGS thin film PV modules for low-concentrating systems2000In: Eurosun 2000, Copenhagen, Denmark, 2000Conference paper (Other academic)
  • 287.
    Williams, Sheryl
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    A systematic analysis of a large grid-connected amorphus double-junction photovoltaic system in high latitude application2000Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The loss mechanisms for large grid-connected amorphous double-junction photovoltaic (PV) system application under high latitude climate conditions were systematically analysied. A two years analysis of data from the 10 kWp façade double-junction amorphous system, which forms part of the 60 kWp grid-connected PV system that was installed at the IKEA main office building in Älmhult (56.6?Sweden, in November 1997, forms the basis of this investigation. The analysis found that the system performance ratio (PR) relative to Standard Test Conditions (STC) specifications in 1998 and 1999 were 47% and 41%, respectively, with monthly values as low as 23% in December 1998. The investigation’s aim was to ascertain the numerical contribution made by each of the different loss mechanism, as they relate to PV system operations, to the performance of the system. The effect on the system’s performance by the following four losses were investigated: a) air mass (AM) effect, PRAM b) irradiance and incident angle effect, PRIRR&INC c) inverter effect, PRINV and d) mismatch and others effect, PRMIO. The numerical analysis employed in this study showed that the performance of the double-junction amorphus façade system due to the different loss mechanism (PRX) was seasonal dependent. Where PRAM and PRINV decrease by 28% and 10%, respectively, from June to December and PRIRR&INC and PRMIO increase by 10% and 6%, respectively, over the same period in 1999.

  • 288.
    Woldegiorgis, Abraham
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Improved Inverters for Grid Connected PV Systems2004Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    In this thesis work the performances of two inverters are compared. The inverters are connected to a grid-connected PV system located on the roof of the main building of Hogskolan Dalarna. The system totally consists of 72 photovoltaic modules of 45Wp each. One system has 40 modules and an inverter of type SOLWEX 2065, which was functioning starting from 1994. The other system consists of 32 modules and a new inverter of model NT1800. An overall performance evaluation of the inverters was done. The DC current, DC voltage, AC current and AC voltage of the two systems were measured using a data logger and the result was analyzed and compared. Further the output power of the two systems was calculated and the annual yield estimated. It is found out that the old SOLWEX inverter performs below the manufacturer’s specifications. Its efficiency is more than 10% less. It doesn’t always track the maximum power point of the PV array and its threshold power is more than three times higher than the value given by the manufacturer. The new NT 1800 inverter has a wider MPPT voltage range and tracks the maximum power effectively. The daily output of both systems is plotted as a function of daily global irradiation. The new inverter has a better performance for all irradiation levels. Especially for days with low irradiation levels the new inverter gives much higher yield. It is found out that the new inverter connected system delivers 38% more annual yield as compared to the system with old inverter.

  • 289.
    Yong, Lim Say
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Design of a portable powered Stirling engine2005Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    This paper presents a feasibility study of developing a portable solar power Stirling engine. A generator is to be coupled to the Stirling engine to generate electricity. This system is proposed to be used for low power electrical equipments such as laptop computer and battery charging at remote area inaccessible to grid-connected electricity supply. The anticipated power of the system is about 30W. Two main components that are critical for the performance of the system are solar thermal collector and Stirling engine. Therefore, in this study, many possible choices for solar thermal collector and Stirling engine have been reviewed. Fresnel reflector is chosen as the solar thermal collector because it is portable and able to concentrate solar radiation to high temperature. A prototype Fresnel reflector was constructed and tested. Although the Stirling engine has been designed preliminarily, it was not constructed due to time constraints. However, a piece of steel was used as the receiver. The rate of energy absorbed by the steel is calculated by measuring the rate of change of the temperature of the steel. The test has shown that, if selective coating is used, a stagnation temperature of above 500°C is possible to be achieved. Moreover, the reflector can remain unadjusted for a duration of 35 minutes. From the calculation, it is found that the optimum operating temperature of the system is about 200°C. However, with an aperture diameter of 1.05m for the Fresnel reflector, the system can only deliver 18.3W of electrical power at an overall efficiency of 3.417%. The system has to be optimized to meet the expected electrical power of 30W. Testing on the prototype has shown that selective coating should be applied directly onto the receiver’s surface without any adhesive in between for achieving high temperature. On cloudy day or at night, the Stirling engine can be heated by other heat sources such as candles, natural gas, wood fuel etc. The Fresnel reflector can also be used as solar cooker when a cooking pot is placed at the focal point of the reflector.

  • 290. Yong, Lim Say
    et al.
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Design and fabrication of a portable Fresnel reflector2006In: Eurosun 2006, Glasgow, UK, 2006Conference paper (Other academic)
    Abstract [en]

    This paper presents a feasibility study of a portable Fresnel reflector that was designed and constructed using inexpensive materials and then tested. An aluminium plastic laminated reflector was chosen for its cost, reflectance and flexibility. The prototype Fresnel reflector had nine rings of 5 cm width held in place by a lightweight wooden construction, giving a diameter of 1.05 m. All rings and wooden holders can be assembled and disassembled and be stored in a small bag. In the tests, a piece of steel was used as receiver. Two different types of surface on the receiver were tested, namely Maxorb sheet and black paint. The tests showed that the Maxorb achieved a stagnation temperature of above 500 °C while the black paint achieved less than 400 °C. The optical efficiency for both was 0.26. Moreover, the collector could remain unadjusted for a duration of 35 minutes without the receiver temperature dropping lower than 300°C at the center.

  • 291.
    Yribarren, Pedro
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Evaluation and simulation of a combined system based on heat pump, solar collectors and borehole storage2002Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The combination of solar collectors with heat pumps and any kind of ground storage offers further possibilities to reduce the electricity demand in buildings significantly compared to standard heat pump systems. On one hand the solar collector enables to deliver higher temperatures to the evaporator of the heat pump and to generate the ground storage much faster, on the other handthe solar heat can be used directly although this requires more advanced system designs and control strategies. In this thesis work the system combination mentioned above has been analysed in two different ways. First, measured data from a system placed in the garden at SERC have been evaluated and second, system simulation with the program TRNSYS have been carried out analysing different designs and configurations for single components in the system. For the evaluation of the measured data files were created that enable to run the whole procedure automatically and to create diagrams for the most important values at the same time. The analysis of the test system at SERC showed that the coefficients of performance of the heat pump for different source and load temperatures do not correspond with the curves from the heat pump company. The simulation work was concentrated mainly on the analysis of the borehole model, further calculations included different system designs for the combination of different solar collectors with a heat pump and borehole storage. In both parts the influence of different parameters on the system performance was analysed regarding as well as energetic values as the temperatures in the ground storage. The advantage of this system combination and the possibilities to increase the system performance were emphasised although it became obvious that further investigations are necessary to open up the whole potential.

  • 292.
    Zatyko, Judit
    Dalarna University, School of Technology and Business Studies, Environmental Engineering.
    Solar Radiation from Sisimiut2004Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The topic of this project was to deal with measured solar radiation and other weather data from Asiaq station 515, sisimiut, Greenland in spring 2004 to make investigations and determinations about the available solar energy in high latitudes; determine the solar radiation on tilted surfaces from radiation on horizontal with the help of different solar radiation models for the test period, and compare the results to the measurements, Determine the ground reflectance during the test period.

3456 251 - 292 of 292
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