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  • 251.
    Vestlund, Johan
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Ett bad när som helst: Dimensioneringsråd för varmvatten2011Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Rapporten Ett bad när som helst - Dimensioneringsråd för varmvatten är framtagen av Johan Vestlund inom delprojekt Sol- och biovärme. Syftet med studien är att utreda vilka kriterier som gäller i en ackumulatortank med dubbla varmvattenslingor för att i alla situationer kunna leverera tillräckligt med varmvatten för en badkarsuppfyllning. Enkla underlag för att beräkna erforderlig slinglängd har tidigare saknats och tidsödande provning har behövt genomföras för att optimera varmvattenkapaciteten i ackumulatortankar. I denna rapport presenteras ett nomogram (figur 4, sida 13) som visar sambandet mellan be-redskapsvolym, temperaturnivå och slinglängd för att uppfylla Boverkets byggregler för ett småhus. Att tillräcklig varmvattenkomfort erhålls är viktigt, också för att kunden ska bli nöjd med ett solvärmesystem. Att detta kan ske vid rimliga tanktemperaturer på 60-65 °C är viktigt för att solvärmetillskottet ska bli högt. Ökad varmvattenkomfort ökar energibehovet och minskar solvärmebidraget varför det är viktigt att dimensionera korrekt. Utgångspunkten för att bygga ett effektivt solvärmesystem är därför att först utgå från en korrekt dimensionerad varmvattenkapacitet. Mängd varmvatten som det går att få ut från en ackumulatortank bestäms av volymen på det uppvärmda vattnet i tankens topp, temperaturen i tanken, och slingornas längd och placering.

  • 252.
    Vestlund, Johan
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Gas-filled, flat plate solar collectors2012Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    This work treats the thermal and mechanical performances of gas-filled, flat plate solar collectors in order to achieve a better performance than that of air filled collectors. The gases examined are argon, krypton and xenon which all have lower thermal conductivity than air. The absorber is formed as a tray connected to the glass. The pressure of the gas inside is near to the ambient and since the gas volume will vary as the temperature changes, there are potential risks for fatigue in the material. One heat transfer model and one mechanical model were built. The mechanical model gave stresses and information on the movements. The factors of safety were calculated from the stresses, and the movements were used as input for the heat transfer model where the thermal performance was calculated. It is shown that gas-filled, flat plate solar collectors can be designed to achieve good thermal performance at a competitive cost. The best yield is achieved with a xenon gas filling together with a normal thick absorber, where normal thick means a 0.25 mm copper absorber. However, a great deal of energy is needed to produce the xenon gas, and if this aspect is taken into account, the krypton filling is better. Good thermal performance can also be achieved using less material; a collector with a 0.1 mm thick copper absorber and the third best gas, which is argon, still gives a better operating performance than a common, commercially produced, air filled collector with a 0.25 mm absorber. When manufacturing gas-filled flat plate solar collectors, one way of decreasing the total material costs significantly, is by changing absorber material from copper to aluminium. Best yield per monetary outlay is given by a thin (0.3 mm) alu-minium absorber with an argon filling. A high factor of safety is achieved with thin absorbers, large absorber areas, rectangular constructions with long tubes and short distances between glass and absorber. The latter will also give a thin layer of gas which gives good thermal performance. The only doubtii ful construction is an argon filled collector with a normal thick (> 0.50 mm) aluminium absorber. In general, an assessment of the stresses for the proposed construction together with appropriate tests are recommended before manufacturing, since it is hard to predict the factor of safety; if one part is reinforced, some other parts can experience more stress and the factor of safety actually drops.

  • 253.
    Vestlund, Johan
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Dalenbäck, Jan-Olof
    Rönnelid, Mats
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Design of gas filled solar collectors2010Ingår i: Eurosun 2010 / [ed] Vestlund, Johan, Graz, 2010Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    With a suitable gas filling used between cover glass and absorber in a flat plate solar collector, it is possible achieving better thermal performance at the same time as the distance between absorber and glass can be reduced. Though, even if there is no vacuum inside the box, there will be potential risks for exhaustion due to stresses depending on the gas volume varies as the temperature varies. This study found out that it is possible build such a collector with less material in the absorber and the tubes and still getting better performance, without risks for exhaustion.

  • 254.
    Vestlund, Johan
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Dalenbäck, Jan-Olof
    Rönnelid, Mats
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Movement and mechanical stresses in sealed, flat plate solar collectors2012Ingår i: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 86, nr 1, s. 339-350Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This article describes movements and mechanical stresses in sealed, gas-filled, flat plate solar collectors. The advantage of a sealed space between a collector absorber and glass cover is that it (i) eliminates the influence of humidity condensation and dust and (ii) it lowers the heat losses when the enclosed space is filled with a suitable gas at normal pressure. However as the solar collector temperature varies, volume and pressure changes cause movement and mechanical stresses. In this study, the finite element method was used to determine movements and mechanical stresses. Several geometries were analyzed and it was found that the stresses in the investigated collectors are a factor 2–4 below the critical stress levels. Furthermore, it was found to be possible to reduce the stresses and improve the factor of safety by (i) using a larger area and/or reducing the distance between the glass and the absorber and/or (ii) changing the length and width so the tubes are longer.

  • 255.
    Vestlund, Johan
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Dalenbäck, Jan-Olof
    Rönnelid, Mats
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Movements and mechanical stresses in gas-filled flat plate solar collectors2008Ingår i: Eurosun 2008, Lissabon, 2008Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Sealed gas filled flat plate solar collectors will have stresses in the material since volume and pressure varies in the gas when the temperature changes. Several geometries were analyzed and it could be seen that it is possible reducing the stresses and improve the safety factor of the weakest point in the construction by using larger area and/or reducing the distance between glass and absorber and/or change width and height relationship so the tubes are getting longer. Further it could be shown that the safety factor won't always get improved with reinforcements. It is so because when an already strong part of the collector gets reinforced it will expose weaker parts for higher stresses. The finite element method was used for finding out the stresses.

  • 256.
    Vestlund, Johan
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Dalenbäck, Jan-Olof
    Rönnelid, Mats
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Thermal and mechanical performance of sealed, gas-filled, flat plate solar collectors2012Ingår i: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 86, nr 1, s. 13-25Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The study includes calculations for both the thermal performance and the mechanical behaviour of a gas-filled, flat plate solar collector without external gas expansion, i.e., a collector with varying gas volume and gas pressure and movement in both cover glass and absorber. Classical theories for the thermal performance are combined with a finite-element method to investigate which factors have an impact from the mechanical stress point of view. This article describes major results for collectors with copper and aluminium absorbers combined with different inert gases. It is shown that a collector may be designed which uses less material than a standard collector but achieves at least the same thermal performance, by using a thinner collector and a thinner absorber and a suitable gas filling other than air. If copper is used in absorber and tubes, a 0.15 mm thick absorber together with a tube-to-tube distance of 103 mm results in the same performance as a 0.3 mm absorber with a 144 mm tube-to-tube distance, but the former will use 25% less material. The use of copper can be further reduced if the absorber is made of aluminium and the tubes are made of copper. The factor of safety for thick (>0.5 mm) aluminium absorbers is, however, not as large as it is for copper absorbers.

  • 257.
    Vestlund, Johan
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Dalenbäck, Jan-Olof
    Rönnelid, Mats
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Thermal losses in sealed, gas-filled flat plate solar collectors2007Ingår i: Solar World Congress, Peking, 2007, Vol. 1, s. 651-655Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    A sealed space between absorber and cover glass makes it possible reducing the influence of humidity condensate and dust at the same time as the enclosed space can be filled with a suitable gas for lowering the losses. This paper is about the size of the losses in these collectors. A calculating model of a gas-filled flat plate solar collector was built in Matlab with standard heat transfer formulas. It showed that the total loss can be reduced up to 20% when changing to an inert gas. It is also possible using a much shorter distance and still achieve low losses at the same time as the mechanical stresses in the material is reduce.

  • 258.
    Vestlund, Johan
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Persson, Tomas
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Win, Kaung Myat
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Effektiviseringspotential för värmesystem med sol och pellets: Parameterstudier, emissionsfaktorer och simuleringsresultat2012Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Syftet med denna studie är att hitta driftsbetingelser som sänker pelletsförbrukning och utsläpp och därmed även de totala kostnaderna för ett värmesystem. Värmesystemet har två huvudsakliga energikällor; sol och pellets. En elpatron används också, för att täcka upp med värme när solen lyser med sin frånvaro och pelletsystemet inte har hunnit börja leverera värme, till exempel i samband med start av brännaren. Lasten utgör värme till ett småhus av dagens standard och tappvarmvattenbehov.

  • 259.
    Vestlund, Johan
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Rönnelid, Mats
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Dalenbäck, Jan-Olof
    Thermal performance of gas-filled flat plate solar collectors2009Ingår i: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 83, nr 6, s. 896-904Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A sealed space between absorber and cover glass in a flat plate solar collector makes it possible to reduce the influence of humidity condensate and dust at the same time as the enclosed space can be filled with a suitable gas for lowering the heat losses. This article describes the influence of different gases on the heat losses in a typical flat plate solar collector. A model of a gas-filled flat plate solar collector was built in Matlab with standard heat transfer formulas. The results show that the overall heat loss can be reduced by up to 20% when changing from air to an inert gas. It is further possible to reduce the distance between absorber and cover in order to reduce the mechanical stresses in the material with similar heat losses.

  • 260.
    Wadström, Maria
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Evaluation of seasonal storage for passive houses in Ireland2010Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    To be able cover most of the heating demand in buildings in northern Europe with solar energy it is necessary to store energy from summer to winter. Scandinavian Homes is an Irish construction company that has come up with an idea of a solar seasonal storage system for one of their passive houses. The system basically consists of 6 vacuum tube collectors (absorber area 10.8 m2), one large underground store with a low height-to-diameter ratio and one smaller DHW (domestic hot water) store placed inside the house. In the seasonal store there are three coils: one for the solar circuit, of for pre-heating the DHW and one for a floor heating circuit. The collectors will primarily heat the DWH store and secondly the seasonal store. The main aim of this study is to evaluate the system described above. The aims are also to examine the influence of different parameters on the system performance and to suggest an alternative design of a seasonal storage system and to compare this to Scandinavian Homes’ system. The performance of Scandinavian Homes’ system was examined using the simulation program Polysun 4.4. Parametric studies of the collector area, the flow rate in the collector circuit and the tank height were performed and the effects of lowering the settings of the thermostats in the system were examined. After a literature study focusing on solar seasonal storage systems for single family houses, two alternative system designs were chosen. The first system included one large tank used for both DWH and space heating and an external heat exchanger for the solar loop. The second system included one large tank with an internal tank for DHW heating. In this case two internal heat exchangers for the solar loop were used. The seasonal stores in these systems both had a high height-to-diameter ratio. The systems were simulated in Polysun with the same boundary conditions as Scandinavian Homes’ system. In order to compare the three systems to each other, the key figure fractional extended energy savings was used. The results were also compared to a simple solar DWH system with an array of 3 collectors. The results from the simulations of Scandinavian Homes’ system showed that variations in flow rate and tank height had little impact on the system performance. The total need of primary auxiliary energy was however decreased by 13% when the temperature required at tap was lowered from 55 to 50°C. When comparing the systems to each other it was found that the solar fractions for Scandinavian Homes’ system and the second alternative system were very similar. Six collectors (10.8 m2) resulted in fractional savings of nearly 60% and 20 collectors (36 m2) gave fractional savings of about 85%. The fractional savings never exceeded 90%, even though the collector area was increased to 70 m2. The simulation results of the first alternative system showed that it failed in delivering the requested DHW temperature at tap. This system could therefore not be compared to the other two. According to the simulations results achieved in this study Scandinavian Homes’ solar seasonal storage system works well in comparison to other seasonal storage system designs. A much larger collector array than the one originally intended by Scandinavian Homes’ would however be needed to cover most of the heating demand in their passive houses with solar energy. The solar fractional savings of the simulated DWH system consisting of 3 collectors turned out to be similar to the savings achieved when a seasonal storage system with 3 collectors was used.

  • 261.
    Wang, Guandong
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Evaluation of Monitored Pellet & Solar Heating Systems2009Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    In this study, three solar and pellet heating systems have been studied with the help of monitoring system. The main technology of these three systems is generally the same. The main target system is located in Hedemora which has an extra shunt loop in the boiler circuit. The following data have been monitored during this period: the solar irradiation, the outdoor and indoor temperature, the return and supply temperature of each circuit, the flow rate of each loop, the 3-phase and 1-phase electricity consumption. The aim of this thesis work is to evaluate the thermal performance of the system and through analysis of the detailed data find whether each component of the system functions as it should do. Also the main ambition is to make some improvements based on analysis of the one minute step monitoring data. The whole system can be divided into four different circuits: solar collector circuit, DHW circuit, space heating circuit and boiler circuit. In the process of study, a special excel sheet should be used to calculate the energy balance and operational curve of each component. In general, we found that the monitoring result varies with design setting. And more heat losses have been found in the process of the operating. For a two person detached house, ten square meter solar collector and 750 litres buffer store are both oversized. Based on these findings, in the future work, more simulations are needed. To pursuit more efficiency thermal performance, some temperature setting of the control system should be changed.

  • 262.
    Wang, Qiong
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    PV standalone system in traffic signal application2010Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    A PV standalone system in traffic signal application was researched and designed based on the energy shortage worldwide and to settle some problems on traffic signal lights against actual application. This system was able to leave out the construction project of the road, economization of funds, energy saving and environmental protection, and which will not result in the traffic jam in the process of fixing and debugging. The traffic control conveniently becomes true at the area where is far away from the grid. The main aim of the thesis is to design a PV standalone system in traffic light application in Shenyang, China. Additional aim is to find the most energy-efficient ways of working for LED load in solar PV lighting application. The PWM technology was studied and the energy consumption under different conditions will be tested. The system design feeds the relevant industry standards. The method for system sizing is used extensively by Telecon in Australia and represents a very conservative approach in which array size is optimized as a function of battery capacity. Through theoretical and practical research, a multi-view understanding can be gained in the PV application. A standalone system in traffic signal is sized and the results of sizing are 275W PV panel and 390Ah battery totally. The system includes three same systems with the sizing of 55W PV panel and 80Ah battery and one bigger system with the sizing of 110W PV panel and 150Ah battery. The required capital cost is ?25770. The discount payback is 17.1 years. The saved electricity per year is 151.8KWh. A cost effective system could be gained with the increased intensity of financial incentive and decreased price of PV panel.

  • 263.
    Weiss, Philipp
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Byggnadssektorn och framtiden: Session 1, Dalarnas Energi- och klimatseminarium 10 maj 20112011Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    En enkel Delphi-enkät skickades till drygt 100 beslutsfattare och experter inom Dalarnas byggsektor. Enkätdeltagarna tog ställning till 15 framtidsteser om bebyggelsens energiomställning. Enkätutfallet visar att få deltagare tror att energieffektiviseringsmålen kommer att kunna nås i tid. Staten och fastighetsägarna anses vara de viktigaste aktörerna för att förverkliga framtidsteserna. Lite förtroende finns det för frivilliga beteendeförändringar hos brukarna och stor oenighet råder kring renoveringens betydelse för energiomställningen.

  • 264.
    Weiss, Philipp
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Dalarnas byggnadsbestånd: Sammansättning och energianvändning 20082011Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Dalarnas byggnadsbestånd kännetecknas av en stor andel bostäder, i synnerhet småhus. Permanentbebodda småhus och fritidshus utgör 60% av den uppvärmda arean i länet och bostäderna uppskattas stå för över 80% av energianvändningen i länets bebyggelse. En stor andel av bebyggelsen är byggt före 1961 och nybyggnationstakten har varit mycket låg sedan mitten av 1990 ‐talet. Detta i kombination med en låg rivningstakt gör att energiomställningen måste ske i den befintliga bebyggelsen, förutsatt att rådande trender inte bryts radikalt. Ägarstrukturen av den befintliga bebyggelsen är mycket fragmenterad på grund av den höga andelen småhus, vilket måste påverka strategin för omställningsarbetet. Tänkbara kommande analyser av bl.a. specialenheterna (skolor, allmänna byggnader, idrottsanläggningar etc.), fritidshusen och socioekonomiska faktorer relaterade till länets bebyggelse skulle kunna förfina problembilden och underbygga det långsiktiga strategiska arbetet för energieffektiviseringen i länet.

  • 265.
    Weiss, Philipp
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Energy savings potential in existing houses: Energy simulation results for Dalarna's single-family housing stock2012Rapport (Övrigt vetenskapligt)
  • 266.
    Weiss, Philipp
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik. 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 Use2014Licentiatavhandling, monografi (Övrigt vetenskapligt)
    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.

  • 267.
    Weiss, Philipp
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Vägar till en halverad energianvändning i Dalarnas småhusbebyggelse2014Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Denna rapport är en svensk sammanfattning av licentiatavhandlingen med titeln "Simple Question, Complex Answer. Pathways towards a 50% Decrease in Building Energy Use", som publicerades vid Uppsala Universitet i februari 2014. I denna rapport har jag samman-ställt det som jag anser vara de viktigaste resultaten ur ett länsperspektiv och rapporten riktar sig därför i första hand mot aktörer inom byggnadssektorn i Dalarna. Mer omfattande bild-material, diagram, tabeller och hänvisningar till källmaterial återfinns för den intresserade i licentiatavhandlingen. Min förhoppning är att denna sammanfattning kan ligga till grund för diskussioner och beslut om framtiden för Dalarnas småhusbestånd.

  • 268.
    Win, Kaung Myat
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Evaluation of a large PV installation in Falun2008Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    The study summarizes the performance of a large PV system, a 150 kWp plant, during 14th February and 16th April in Falun, Sweden. It has been in operation since the end of January 2008. It feed the generated energy into the grid and is used by the building. The system consists of 4 photovoltaic arrays 861 modules of 175 Wp with 26 inverters which are connected to each string array. The strings array configuration has 7 different configurations. The 4 main arrays are installed on the roof of the building in two orientations. The performance parameters are calculated as defined in IEC 61724 and daily and monthly energy balance are investigated. The possible shading is also studied and the measured radiation is reviewed relative to the power production. A radiation measured by sensor 1 is revised as there is substantial differences are detected. This is corrected by a correlation developed with measured DC power production normalized to the module verses measured irradiance. A same system is modelled in the PVSyst program to simulate for the expected energy production and performance parameters which are then compared with the measured results on an emphasis on the module temperature as the module has a black tedlar coating. A performance evaluator in Excel is also created following the same procedure as the evaluation is done. It can be used to evaluate the performance of the system in the future. The system generated about 16.8 MWh. The average electricity generated per day is 266 kWh. It ranges from 30 kWh/day in February to 662 kWh/day in April. The final yield Yf ranged from 0.2 to 3.4 h/day and the performance ratio PR range from 0.35 to 0.98.

  • 269.
    Win, Kaung Myat
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Paavilainen, Janne
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Persson, Tomas
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Emissions Characterisation of residential pellet boilers during start-up and stop periods2010Ingår i: 3rd International Scientific Conference on “Energy systems with IT”, Älvsjö, Stockholm, Sweden, 2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this study, gaseous emissions and particles are measured during start-up and stop periods for an over-fed boiler and an under-fed boiler. Both gaseous and particulate matter emissions are continuously measured in the laboratory. The measurement of gaseous emissions includes oxygen (O2), carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxide and (NO). The emissions rates are calculated from measured emissions concentrations and flue gas flow. The behaviours of the boilers during start-up and stop periods are analysed and the emissions are characterised in terms of CO, NO, TOC and particles (PM2.5 mass and number). The duration of the characterised periods vary between two boilers due to the difference in type of ignition and combustion control. The under-fed boiler B produces higher emissions during start-up periods than the over-fed boiler A. More hydrocarbon and particles are emitted by the under-fed boiler during stop periods. Accumulated mass of CO and TOC during start-up and stop periods contribute a major portion of the total mass emitted during whole operation. However, accumulated mass of NO and PM during start-up and stop periods are not significant as the duration of emission peak is relatively short.

  • 270.
    Win, Kaung Myat
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Persson, Tomas
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    EMISSIONS CHARACTERISTICS OF A RESIDENTIAL PELLET BOILER AND A STOVE2010Ingår i: World Bioenergy 2010, Jönköping Elmia, Sweden, 2010Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Gaseous and particulate emissions from a residential pellet boiler and a stove are measured at a realistic 6-day operation sequence and during steady state operation. The aim is to characterize the emissions during each phase in order to identify when the major part of the emissions occur to enable actions for emission reduction where the savings can be highest. The characterized emissions comprised carbon monoxide (CO), nitrogen oxide (NO), total organic carbon (TOC) and particulate matter (PM 2.5). In this study, emissions were characterised by mass concentration and emissions during start-up and stop phases were also presented in accumulated mass. The influence of start-up and stop phases on the emissions, average emission factors for the boiler and stove were analysed using the measured data from a six-days test. The share of start-up and stop emissions are significant for CO and TOC contributing 95% and 89% respectively at the 20kW boiler and 82% and 89% respectively at the 12 kW stove. NO and particles emissions are shown to dominate during stationary operation.

  • 271.
    Win, Kaung Myat
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Persson, Tomas
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Bales, Chris
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Particles and gaseous emissions from realistic operation of residential wood pellet heating systems2012Ingår i: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 59, s. 320-327Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Gaseous and particulate emissions from six residential wood pellet heating systems are determined at a realistic six day operation sequence. The study aims to investigate the total emissions from a realistic operation of the heating systems including start-up and stop phases. Five combined solar and pellet heating systems and one reference boiler without solar system with an integrated DHW preparation was tested in a laboratory at realistic operation conditions. The investigated emissions comprised carbon monoxide (CO), nitrogen oxide (NO), total organic carbon (TOC) and particulate matter (PM2.5). In this study, the emissions are presented as accumulated total emissions from the whole six days period and the emissions from start-up and stop phases are also presented separately to evaluate the influence of the emissions from these phases on the total emissions. Emission factors of the measured systems from the six day period are between 192 and 547 mg MJ1 for the CO emissions, between 61 and 95 mg MJ1 for the NO, between 6 and 45 mg MJ1 for the TOC, between 31 and 116 mg MJ1 for the particulate matter and between 2.1 × 1013 and 4 × 1013 for the number of particles. The emissions from the start-up and stop phases are significantly high for the CO (63–95 %) and the TOC (48–93 %). NO and particles emissions are shown to dominate during stationary operation. However, 30–40 % of the particle emissions arise from the start and stop periods. It is also shown that the average emissions of CO, TOC and particles under the realistic annual conditions were higher than the limit values of two eco labels.

  • 272.
    Wäckelgård, Ewa
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Broman, Lars
    Lindberg, Eva
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Reflection properties of uncoated metal surfaces: A literature study1988Rapport (Övrigt vetenskapligt)
  • 273. Yazdanshenas, Eshagh
    et al.
    Furbo, Simon
    Bales, Chris
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Theoretical comparison between solar combisystems based on bikini tanks and tank-in-tank solar combisystems2008Ingår i: Eurosun 2008, Lisbon, 2008Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Theoretical investigations have shown that solar combisystems based on bikini tanks for low energy houses perform better than solar domestic hot water systems based on mantle tanks. Tank-in-tank solar combisystems are also attractive from a thermal performance point of view. In this paper, theoretical comparisons between solar combisystems based on bikini tanks and tank-in-tank solar combisystems are presented. The investigations are carried out for different designs and sizes of the two solar heating system types installed in different houses. The investigations show which types of solar combisystems are suitable for low energy houses, new houses built according to the building codes and old houses.

  • 274.
    Zhang, Baoxin
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    How the different time steps weather data affect the simulation results of solar combisystems2009Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    The hourly time step weather data are very common used in the field of evaluations and predictions of the performance of solar heating systems, especially in the computer simulation area. However, studies in [3] states that using the hourly weather data in simulation of solar systems may ignore the variations of solar radiation during one hour, it will cause a inaccurate simulation results. Using the smaller time step weather data instead can resolve this problem and make the simulation results very close to the fact. In this paper, the variations of solar radiation during hourly will be found through comparison of the same weather data based on different time steps (hourly and 6min). A whole weather data reference year based on 6min, 12min, 18min, 30min and 60min in Borlänge, Sweden will be built. Then the total radiation on a sloped surface, clearness index and solar utilizability based on these different time steps weather data will be calculated and compared with each other respectively. The results show that same weather data based on different time steps do not affect the calculation results of total radiation on a sloped surface (collector surface) but they may affect the beam and diffuse fractions and estimate of collector performance. After that all the weather based on different time steps will be used in the simulations of three different solar combisystems. As the result shows, using the hourly weather data leads to relative conservative estimate of solar heating systems compare with that based on shorter time step weather data, although the difference is very limited.

  • 275.
    Zhang, Xiaoxue
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Sun, Qiao
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Performance Evaluation of a Grid-connected PV system in Falun2009Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    The photovoltaic system of 150WP in Falun is on the sloped roof which is 14 degree with east and west orientations. A calibration of the radiation sensors has been done in order to correct the voltage drop caused by the extended cable length. The radiation sensors are calibrated by comparing the measured irradiance of the PV system with the reference irradiance which is measured by a portable data logger system. The annual performance of the system is evaluated over one year from April 08 to March 09 according to IEC 61724. Two other PV systems are compared with Falun system based on the annual performance of each system. The total system energy production of one year is about 96 MWh and the performance ratio PR is 0.817.

  • 276.
    Ålander, Atte
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Electricity Supply Solutions for an Educational Center in Tanzania2013Självständigt arbete på avancerad nivå (magisterexamen), 12 poäng / 18 hpStudentuppsats (Examensarbete)
    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.

  • 277.
    Šumić, Mersiha
    Högskolan Dalarna, Akademin Industri och samhälle, Energi och miljöteknik.
    Thermal Performance of a Solarus CPC-Thermal Collector2014Självständigt arbete på avancerad nivå (magisterexamen), 40 poäng / 60 hpStudentuppsats (Examensarbete)
    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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