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  • 251. Trygg, Louise
    et al.
    Björk, Curt
    Karlsson, Peter
    Rönnelid, Mats
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Djuric Ilic, Danica
    Heat collaboration for increased resource efficiency: A case study of a regional district heating system and a mine2016Conference paper (Other academic)
    Abstract [en]

    To rapidly develop sustainable energy systems is crucial for the whole society's transition towards sustainability. System efficiency and reduced climate impact are important parts of this. Swedish district heating systems are fairly well developed, mainly based on non-fossil fuels, and includes energy-efficient technologies (such as combined heat and power production and fuel gas condensation). Increased use of district heating is therefore considered as a way to increase energy-efficiency, to phase out fossil energy for heating purposes, and subsequently to a reduction of global CO2 emissions. 

    The aim of this paper is to study system impact of increased demand of district heating by analysing a collaboration on heat supply between the local energy supplier of Ludvika in Sweden and a nearby mine. The paper analyses economic potential, as well as the potential for more efficient operation of district heating production plants in the local district heating system. The heat demand in the mine is presently supplied from a small-scale biomass-fuelled heat-only boiler located near to the mine. The system consists of two biomass-fuelled heat-only boilers with fuel gas condensers. The consequences of connecting the heat demand of the mine with the municipal district heating system is analyzed using the cost optimization model MODEST. 

  • 252.
    Trygg, Louise
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Ersson, Hans
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Gradén, Mattias
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Ragnarsson, Marit
    Rehme, Jakob
    Hinder och Drivkrafter: Projekt Branschvis Energieffektivisering2015Report (Other academic)
    Abstract [sv]

    Föreliggande rapport är en del av utvärdering av projektet BEE – Branschvis energieffektivisering.

    Projektet BEE – Branschvis Energieffektivisering

    Projektet genomfördes under 2013-2014 i Dalarna och Gävleborgs län. Projektägare var Länsstyrelsen Dalarna i samarbete med Gävle-Dala Energikontor. Projektet finansierades med medel från Energimyndigheten, Region Gävleborg och Länsstyrelsen Dalarna.

    Samarbete inleddes med små och medelstora industrier (SME) inom följande branscher: sågverk, teknikföretag, träindustrier, kött- och livsmedelsindustrier, alpina skidanläggningar, turisthotell, drivmedelsstationer och livsmedelsbutiker. För varje bransch har projektet anlitat en specialiserad energikonsult som hjälpt företagen med energikartläggningar och gett stöd för planering av åtgärder. 125 företag medverkade i projektet, varav 116 stycken gjorde en heltäckande energikartläggning. Sammanlagt togs mer än 1 750 förslag på åtgärder fram.

    I projektidén för BEE ingick även att engagera energi- och klimatrådgivarna i genomförandet, för att på så sätt bidra till kompetensutveckling. Syftet med projektet var att fokusera på energikartläggningar och genomförande av åtgärder. Själva energikartläggningarna har inte genomförts med finansiering av projektet, utan som en affärsmässig uppgörelse mellan företagen och vald energikonsult.

    Syftet med föreliggande rapport är att studera förutsättningar för en implementering av åtgärder för energieffektivisering som framkommit vid de genomförda energikartläggningarna från projekt BEE. Genom intervjuundersökningar och enkätstudier har drivkrafter och hinder studerats för energieffektivisering samt hur företagen arbetar med internt energieffektivisering. Som komplement till detta är även en analys gjord avseende ekonomiska förutsättning för energieffektivisering i de studerande branscherna (se appendix 1).

    De resultat som presenteras i denna rapport har gjorts med representanter från olika befattningar inom de analyserade industrierna. Alla har gett sin syn på hinder och drivkrafter för energieffektivisering samt hur det interna energieffektiviseringsarbetet fortgår inom deras organisation och hur det kan förbättras.

    Resultat från intervjuundersökningar och enkätstudier visar bl.a. att inom branscherna teknikföretag, kött- och livsmedelsindustrier, alpina skidanläggningar, drivmedelsstationer, turisthotell och livsmedelsbutiker är kostnadsbesparingar är en av de tre främsta gemensamma drivkraften, samt att brist på investeringskapital eller osäkerhet kring investeringsberäkning anges som ett av de främsta hindren för energieffektivisering. Inom branscherna sågverk och träföretag är beteende och attityder rankat som främsta hindret för energieffektivisering samt stöd från högsta ledningen den största drivkraften för att genomföra energieffektiviseringar.

    Resultat från studien visar också att projekt BEE bidragit med ytterligare kunskap om möjligheten att energieffektivisera, samt även att projektet har medfört ett mer aktivt energieffektiviseringsarbete inom den egna organisationen.

  • 253.
    Tuccella, Simone
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Grid Connection of the Existing Off-grid PV system at Mavuno Secondary School in Tanzania2016Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The research investigated the grid connection of the existing off-grid PV system at Mavuno Secondary School in Tanzania. The national power grid reached the area during 2015; therefore the grid connection has been studied together with eventual increases of the PV array size. Such research provided a feasibility study in the unexplored topic of connecting stand-alone systems to the national grid once it becomes available.

    The first part of the study aimed to define the load consumptions of the school. On this regard, a measurement system has been set up. It also measured the values of battery state of charge and PV production. The second part involved the modelling and simulations of the system by means of the software HOMER. The existing system has been simulated showing a cost of energy of 0.42 $/kWh. The modelled results showed an overall similarity with the measured values, although some limitations of both measurement system and simulation tools were present. After that, the optimisations of the system regarding future scenarios have been performed. The investigation involved both PV stand-alone and grid connection configurations. Increased load cases and different grid scenarios have been considered. Depending on the load scenarios, the stand-alone system presented a cost of energy between 0.34 $/kWh and 0.55 $/kWh. Instead, depending on load and grid configurations, the grid connected system showed a cost of energy ranging from negative values to 170 $/kWh. The negative values were due to the higher incomes of the sellback compared to the system expenses.

  • 254.
    Turk, Suheyla
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Sustainable Neighbourhood Design in Jakobsgårdarna, Borlänge2019Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Energy efficient houses benefit communities not only to provide renewable energy shares and generating surplus electricity supporting local economic development. Also, residents in energy efficient houses have less energy usage that reduces household budget expenses. However, one of the obstacles of energy efficient technology installment of residential buildings is high investment cost, which can be solved with the usage of modular housing. In Europe, housing costs have a large share, especially for Sweden, housing expenses is a burden mostly for people who are at the risk of poverty. Also, high investment costs of energy efficient housing are combined with high construction prices leading a large share of budgets and effort to make houses affordable for low income groups. This study develops a scenario to find solutions for affordable housing problem in Sweden with a design proposal. The aim of this study is to investigate if there are ways of achieving socio-economic mix by the production of energy efficient affordable housing and urban gardening to develop a strategy for resource efficiency in Jakobsgårdarna. To achieve the aim, energy efficient affordable housing designed as modular units to achieve a local economic development. This study uses a design-based research method consisting of learning from background cases to transfer lesson learned in design phase of the sustainable neighborhood consisting of energy efficient technologies. Background cases were analyzed with literature review to define sustainable neighborhood, which was then used to develop a hypothesis. Findings of this thesis generates definition of sustainability tools consisting of a collaborative ownership; designing common kitchens; producing electricity and biogas from renewable energy sources; practicing urban agriculture; managing waste and storm and methods to cross subsidize energy efficient affordable housing production. The outcome of this research provides a sustainable neighborhood design proposal for Jacobsgårdarna, Borlänge.

  • 255. Turk, Suheyla
    et al.
    Quintana, Samer
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Life-cycle analysis as an indicator for impact assessment in sustainable building certification system: the case of Swedish building market2018In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 153, p. 414-419Article in journal (Refereed)
    Abstract [en]

    This paper assesses the prevailing sustainable building certification systems in Sweden, based on a critical analysis of their characterization for human and environmental impacts through the integration of life-cycle analysis. The aim of this study is to compare sustainable building certifications systems in terms of their assessment categories. In the Swedish market, BREEAM SE, LEED, Green Buildings and Miljobyggnad are the most used building certifications. Therefore, their guidelines are reviewed to evaluate which of them has comprehensively included human health indicators. This research presents useful information for transforming existing and developing future sustainable building certification systems.

  • 256.
    Vangari, Divyanagalakshmi Haribabu
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Fathima, Sumayya
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Design of Distributed Rooftop PV System to Minimize Power Cuts for an Indian Village2018Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    India is a developing country. The national energy production is not enough to fulfill the energy demands of the country. Moreover, there are many villages still needs to be electrified. Among the electrified villages, most of them receive only a few hours of electricity each day making it difficult for people residing there. India has excellent potential for the solar power receiving (4 to 7) kWh/m

    2. Therefore, Government of India sets an ambitious target to install 100 GW of solar capacity by 2022, 40 GW is from rooftop solar. The government is encouraging installation of rooftop PV systems by providing several financial incentives to set up rooftop PV system and policies to purchase the energy. However, the people living in rural areas are not capable of utilizing such financial incentives and understand the procedures due to lack of knowledge and financial ability. Thus, a suitable techno-economical model for grid-connected solar rooftop installations for an Indian village by a third-party investor and project developer is investigated in this thesis.

    The design of a grid-connected rooftop PV system with a battery is considered in this thesis. The sizing of PV system and battery are done based on the village annual day and night load demands. A 72 kW PV system consisting of 3 kW each on 24 roofs is considered to meet the village load demand. Two design methods are discussed for power evacuation from the 72 kW PV system, (1) Centralized design and (2) Decentralized design. In centralized design, all the 3 kW PV strings are connected in parallel to a central inverter, which is integrated with the three-phase grid. A central battery bank is installed and charged by an inverter fed by the utility supply. In decentralized design, the 3 kW PV sting on each roof is integrated to the nearby single phase line through a single phase inverter. The battery bank is equally distributed among the 24 houses, and each battery is charged by a single phase inverter fed by the utility supply.

    The techno-economic study of the two methods are performed, and the key technical and economic performance indices are compared. The assumptions are made wherever needed, and the uncertainties in the inputs data and methods and their impact on the results are discussed. A 10 % of uncertainties in the inputs data for simulations and other parameters are considered for evaluating the impact of PV system performance. The annual produced energy, specific production, and performance ratio for centralized design are 102 MWh, 1411 kWh/kW, and 0.73 respectively. The corresponding performance indices for decentralized design are 108 MWh, 1498 kWh/kW, and 0.77 respectively. The levelized cost of energy and payback period for the centralized design is 3.23 INR and 8 years whereas for decentralized design are 3.13 INR and 7 years for decentralized design by considering 50 % subsidy on the capital cost of the PV system. The payback period increases to 15 years for centralized design and 13 years for decentralized design without any capital subsidy. Therefore, capital subsidy makes the project more attractive to the project investor. The technical and economic performance of the 72 kW PV system with the decentralized design is better than the centralized design, without considering the impact of uncertainty. However, after considering both the positive and negative variation of uncertainty (± 10 %), it is difficult to comment on which design has the better results because both designs have nearly equal range of results.

    The underlying limitations of the study are highlighted, and their impact on the results are discussed. The main limitations are the accurate estimation of load profile and boundary conditions of the village (such as actual dimensions of the house, orientation, and tilt angle of the roofs) to perform the simulations.

    The relevant previous work is cited at appropriate places in the report.

  • 257.
    Verma, Pankaj
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Water saving comparison study between innovative and conventional cleaning systems for CSP technologies2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 258.
    Vidal Lorbada, Ricardo
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Design and implementation of a charge controller with buck converter topology for a Li-ion battery using the component LTC4015.2016Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report presents the process of design and implementation of a battery charger for a Li-ion battery. The development of this battery charger includes the component from Linear Technology LTC4015. This component integrates the functions of a battery charger configured as a buck (step-down) converter. This device must be integrated in a Printed Circuit Board with a specific design. Also, it must be configured using a microcontroller named Raspberry Pi, which also performs the measurements.

    The method of design is divided in two parts. One is focused on developing the printed circuit board, which includes the simulation of the device and the development of the PCB, and the second one is focused on developing the program used in the microcontroller to manage the operation of the LTC4015.

    The result is a charge controller device that can be used with different configurations with a buck converter topology. The different parts of the design process are the simulation, the design and the implementation. Each of these parts have a section of results in this report. The simulation section includes results obtained with LTSpice and the device LTC4020, which is a similar device to the LTC4015 but without the Maximum Power Point Tracking mode, which is not modelled in LTSpice.

    PV is the main power source considered to charge the battery, and is carefully studied in this project. The PV input is studied with LTSpice, first simulating the I-V curve of the schematic of the solar cell. Second, integrating a solar cell in the simulation of the LTC4015. Third, operating the device LTC4015 with a solar panel that is also characterized.

    The design section includes the electronic components used for the development of the board that integrates the charge controller, the LTC4015 in this case, based on the calculations performed for the requirements of the LTC4015. Finally, the implementation section includes the description of the board implemented but also the description of the configuration and measurement code.

    The conclusions presented in this report show that the LTC4015 is a battery buck charger with different functions that make it suitable to be used in different solar applications. Also, this report opens new future work lines, such as the full characterization of the board, the implementation of a test bench and the integration of the board in different applications for solar energy systems.

  • 259.
    Vijay Vichare, Rohan
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Evaluation of Two Solar Heating and Cooling Systems2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The main purpose of this study is to compare a heat pump system with a SunCool collector system based on the key performance factors. SunCool collectors are sorption integrated solar thermal collectors which produce both heating and cooling. This analysis is carried out in TRNSYS software. The heat pump system is designed with the PV system and then it’s been simulated in TRNSYS for certain climate conditions. The SunCool collector system has been simulated in the existing TRNSED application by using the TRNSYS input file of the system. The parametric study has also been done to get the ideal size of the system and to check how the system works under different parametric conditions. The results of the simulations have been evaluated in terms of total electric consumption, solar fraction, self-consumption and total energy production. Both systems have been simulated for the location of Madrid, Spain. The same load data has been used in the simulation of these systems.

    A simulation study shows that the heat pump system provides 405 MWh of energy to DHW system per year and 351 MWh of energy to space heating and cooling system per year. The SunCool collector system provides 391 MWH and 101 MWh of energy to DHW and space cooling system respectively. The control system of SunCool collector system doesn’t provide energy to space heating. The heat pump system has a maximum load at night hence during the night it takes electricity from the grid and during the day it gives it back to the grid. Almost 80% of the total electricity load is provided by the grid.

    The comparison study of the simulation results shows that the PV+heat pump system provides the full amount of load while the SunCool collector system provides 97% of DHW load and 51% of cooling load with the same number of collectors. Even though the heat pump provides the full amount of load, the electricity consumption of the system is quite higher at 246 MWh per year although for SunCool collector system it’s just 20 MWh per year. Solar fraction of the SunCool collector system is 64% whereas for heat pump system it’s 17%. Hence to select the feasible option between heat pump system and SunCool collector system, an economic analysis must be done by considering the price of the collectors, feed-in tariff and price of the grid electricity.

  • 260.
    Vijayan, Veenaaishwarya
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Simulation Study for Optimal Inverter Sizing of Grid-Connected PV Systems in Swedish Locations2016Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In present scenario grid connected photovoltaic systems are widely deployed in towns and cities as they can contribute to better environment. They also have advantage of generating significant quality of energy near the consumption point by avoiding transmission and distribution losses. In any grid connected system one of the main components needed would be the inverter for delivering AC output to the grid. The key issue to have best output merely depends on the sizing of the component. Factors influencing the sizing of the components in the PV system are components technology, climatic aspects of placements of inverter installed and solar radiation distribution characteristics that, of which location and climatologically plays a major role. In places like Sweden and most parts of northern European countries, under sizing of the inverter in PV grid-connected systems is recommended. This is because solar radiation reaches seldom values around 1000 W/m2 which PV modules are rated for. There are also many cloudy days when the inverter would operate in 5-20% of the nominal range where inverter efficiencies are significantly lower than for higher radiation. Thus leading to cost efficient photovoltaic grid connected systems though there might be certain amount of energy losses in the system.

    Operating at higher or lower ranges reduces the efficiencies of inverters to some extend due to technical implications of the device. In this thesis, the optimal sizing factor of inverter will be studied, besides the energy yield, the cost and expected life time of the inverter shall also be taken into account. For more appropriate results three different locations that covers south, middle and north part of Sweden is taken into account. A life cycle analysis is also done based on system yield simulations, data from the literature and cost data provided by the government norms of Sweden.

    The thesis will also investigate on the effect on life time of the inverters data influences the results due to undersize compared to the PV array and how much the maxima smoothes out due the time resolution of the radiation. One hour average data might mislead as it averages out some of the peak radiation. Comparisons between hourly averages and minute wise global solar radiation is done and analyzed.

  • 261.
    Vijayaragavan, Krishna Prasad
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Feasibility of DC microgrids for rural electrification2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    DC system and DC microgrids are gaining popularity in recent times. This thesis suggests a method to state the workability of a DC based PV system using the softwares Simulink, PVsyst and HOMER. The aims of this project include suggesting a DC based architecture, finding out the performance ratio and a cost analysis. The advantages of the DC based system, the cost benefits associated with it and its performance will determine its feasibility.

     

    Not many softwares have the functionality to simulate DC based PV systems. PVsyst is considered as one of the most sought-out softwares for the simulation of PV systems. It can simulate a DC based PV system but has a lot of limitations when it comes to the architecture and voltage levels. Due to these factors, the results from softwares Simulink, Homer and PVsyst are used to calculate the performance ratio of the suggested DC system. 

     

    The simulation of the DC system involves modelling of a DC-DC converter. DC-DC converters are used in HVDC transmission and are being considered for small scale and medium scale microgrids. The DC-DC boost converter is coupled with a MPPT model in Simulink. P and O algorithm is chosen as the MPPT algorithm as it is simple and widely used. The Simulink model of PV array and MPPT based boost converter provides the power output at the needed voltage level of 350V. The input for the Simulink model is obtained from the results of HOMER. The inputs include solar irradiation data and cell temperature. The same input data is used for the simulations in HOMER and PVsyst. The performance ratio is obtained by combining the power output from Simulink with the other aspects of the system from PVsyst. The performance ratio is done only for the month of January due to the limitations in Simulink. The performance ratio is found out to be 65.5 %.

     

    The cost estimation is done for the distribution and power electronics aspects of the system. It is found out that the cost associated with the conductors will have an impact on the total cost

    only if the conductors used for distribution is more in length. The cost associated with the power converters will make a difference in total cost only if the system is within the range of 100kW. The study shows the workability of the PV based DC system based on the above mentioned aspects

  • 262.
    Wallin, Elisabeth
    Dalarna University, School of Technology and Business Studies, Energy Technology. SLU.
    From growth cessation to bud burst: conifer seedling development in response to nursery culture and environmental stimuli2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

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

  • 263.
    Wallin, Elisabeth
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology. SLU.
    Gräns, Daniel
    Dalarna University, School of Technology and Business Studies, Forest and Wood Technology. SLU.
    Jacobs, Douglass F
    Purdue Univ, Dept Forestry & Nat Resources, W Lafayette, IN 47907 USA..
    Lindström, Anders
    Dalarna University, School of Technology and Business Studies, Forest and Wood Technology. SLU.
    Verhoef, Nathalie
    NSure, Binnenhaven 5, NL-6700 AA Wageningen, Netherlands..
    Short-day photoperiods affect expression of genes related to dormancy and freezing tolerance in Norway spruce seedlings2017In: Annals of Forest Science, ISSN 1286-4560, E-ISSN 1297-966X, Vol. 74, no 3, article id 59Article in journal (Refereed)
    Abstract [en]

    Key message: Gene expression analysis showed that prolonged short day (SD) treatment deepened dormancy and stimulated development of freezing tolerance of Picea abies seedlings. Prolonged SD treatment also caused later appearance of visible buds in autumn, reduced risks for reflushing, and promoted earlier spring bud break.

    Context: Short day (SD) treatment of seedlings is a common practice in boreal forest tree nurseries to regulate shoot growth and prepare the seedlings for autumn planting or frozen storage. Aims The aim of this study was to examine responses of Norway spruce (Picea abies (L.) Karst.) to a range of SD treatments of different length and evaluate gene expression related to dormancy induction and development of freezing tolerance.

    Methods: The seedlings were SD treated for 11 h a day during 7, 14, 21, or 28 days. Molecular tests were performed, and the expression profiles of dormancy and freezing tolerance- related genes were analyzed as well as determination of shoot growth, bud set, bud size, reflushing, dry matter content, and timing of spring bud break.

    Results: The 7-day SD treatment was as effective as longer SD treatments in terminating apical shoot growth. However, short (7 days) SD treatment resulted in later activation of dormancy-related genes and of genes related to freezing tolerance compared to the longer treatments which had an impact on seedling phenology.

    Conclusion: Gene expression analysis indicated an effective stimulus of dormancy-related genes when the SD treatment is prolonged for at least 1-2 weeks after shoot elongation has terminated and that seedlings thereafter are exposed to ambient outdoor climate conditions.

  • 264.
    Wallin, Elisabeth
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology. SLU.
    Gräns, Daniel
    Stattin, Eva
    Dalarna University, School of Technology and Business Studies, Forest and Wood Technology.
    Verhoef, Nathalie
    Mikusiński, Grzegorz
    Lindström, Anders
    Dalarna University, School of Technology and Business Studies, Forest and Wood Technology.
    Evaluating methods for storability assessment and determination of vitality status of container grown Norway spruce transplants after frozen storage2019In: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 34, no 6, p. 417-426Article in journal (Refereed)
    Abstract [en]

    Autumn sown small seedlings for later transplanting into large containers have been introduced in Swedish forest tree nurseries. Containerized transplants of Norway spruce (Picea abies (L.) Karst.) from three Swedish nurseries were frozen stored during the autumn of 2014 to find out storability and post-storage vitality. Seedling storability was determined by measuring electrolyte leakage after freezing shoots to −25°C (SELdiff−25), by measurements of dry matter content (DMC) of seedling shoots and by the commercial molecular test ColdNSure™. Vitality of seedlings after storage was determined by measuring the leakage of electrolytes from shoots (SEL), and seedlings were also tested in regrowth tests. All three methods for storability assessment gave similar predictions, except in one case where DMC showed “not storable” for successfully stored seedlings. Our results indicated that young transplants can be successfully short term stored before reaching the target levels for safe long-term storage of conventional seedlings. Early storage of young transplants resulted in low post-storage survival and vitality expressed as root growth capacity and shoot electrolyte leakage (SEL). A prolonged duration in storage generally resulted in lower survival as well as lower root growth capacity and higher levels of SEL, especially for seedlings stored at earlier dates. 

  • 265.
    Wallinder, Maria
    et al.
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    Perman, Karin
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Könsfördelningen i energiproduktionsbolag i Dalarna: Förstudie om kvinnors upplevelser i en mansdominerad värld2014Report (Other academic)
    Abstract [sv]

    Behovet att förbättra jämställdheten finns över hela Sverige och arbetsmiljöverket har tjugofem miljoner kronor för de följande två åren till förbättringsåtgärder. De fjorton strategier som finns i Dalarna för jämställdhet har inte implementerats helt. Behov finns att undersöka kvinnors upplevelse inom mansdominerade arbetsplatser. Fem kvinnor blev intervjuade inom energiproducentbolag i Dalarna. Resultatet visar att kvinnorna trivs på sina arbetsplatser trots en ständigt påslagen riskkalkylering vid kontakt med sina manliga kollegor. Deras erfarenhet avspeglar sig med att de lämnar flera praktiska strategier till förbättringar.    

  • 266.
    Wallinder, Maria
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Perman, Karin
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Causse, Emmanuelle
    Schröpfer, Veronika
    Gyori, Gabriella
    Grauer, Marlene
    Mohammadi, Max
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Gustafsson, Marcus
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Report on Non-Technical Barriers to the market placement2016Report (Other academic)
    Abstract [en]

    The iNSPiRe project addresses the need for energy efficiency measures by focussing on making so called deep renovations using multifunctional, industrialised kits in order to speed up the on-site installation process and reduce costs. Energy renovation investment is a multi-factor decision and many of these factors are not technical, which is why this report analyses the non-technical barriers to this investment decision. The study focusses on the kits developed within the iNSPiRe project, but many of the findings are relevant for other single stage deep renovation projects. Both the planning and implementation phases are considered. The aim was to develop suggestions for overcoming these non-technical barriers so that the iNSPiRe kits can more easily be deployed in the market.

    The report is based on a study of policy documents, the experiences of European umbrella organisations for architects, property owners and local governments as well as on a large number of in-depth interviews with relevant stakeholders. Many of the 60 participants were made in conjunction with stakeholder workshops that were organised for specific focus groups such as architects, private property owners, public procurers and the stakeholders of the European Housing Forum. The non-technical barriers have been split into economic, political and social barriers, with most interviewed stakeholders emphasising the economic aspects.

    Subsidies are considered by most as essential for property owners to take the decision to make a deep renovation, but stability of the subsidy programs is essential to have a good impact. Low-interest loans are not as favoured. Other key economic issues are the increase in the asset value of the property after such a renovation and the green value of the resulting low energy building. These are both difficult to quantify, partly due to the fact that such renovated buildings are not as yet so common, and vary in the different property markets.

    The EU has many policies on energy efficiency that are relevant for renovation of buildings, with the 2010 Energy Performance of Buildings Directive (EPBD recast) and the 2012 Energy Efficiency Directive (EED) being the most important. Many member states were late in implementing these and most have problems with forcing compliance with them. National tenancy laws can also make energy renovations difficult by restricting the possibility of raising rents for. For the iNSPiRe kits, regulations and standards are seen as a barrier in the short term as the kits combine several different functions into one product that are covered by several different regulations and/or standards.

    The social barriers are mostly concerned with the tenants, while architectural considerations are also important. In buildings with owner-occupied flats, the decision process for renovation is difficult and even more so when deep renovation is to be considered. In rental properties the owners and tenants have different interests and incentives, leading to possible conflicts. All have uncertainties about the use of multifunctional kits and how well they will perform technically as well as about how much they will save economically.

    The report makes a number of suggestions for overcoming these barriers. Especially important for the iNSPiRe kits is training of relevant installers and planners and use of Life Cycle Cost calculations to show the expected benefits over the lifetime of the products.

    In each section of the report, in addition to the analysis of the specific barrier, there are sections with specific comments from the interviewed stakeholders.

  • 267.
    Walusimbi Kizanyiro, Samuel
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Soiling Effects on Photovoltaic Modules, Modelling of Specific Cleaning Frequency Optimization for a 10 MW PV Power Plant inTororo, Uganda2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The accumulation of dust on the photovoltaic (PV) modules for the PV plant result in energy loss and therefore, there was a need to assess the impact of soiling on the PV modules since soiling losses are location specific. In this work, the approach of quantifying soiling loss experimentally which involved comparing the temperature corrected short circuit current values for the naturally soiled string to the frequently cleaned string had higher accuracy than the method of extracting soiling loss from the PV plant production data. This was due to the uncertainties associated with the plant production data.

    The average soiling loss values were determined experimentally and from the plant production data. The month of January 2018 was found to have the highest soling loss of 6 % and March 2018 had the lowest soiling loss was less than 1 %. The soiling for the month of January 2018 was used to determine an optimum cleaning interval which balances out with the revenue lost due to soiling and the cost of the cleaning event using the cleaning schedule model and the optimum interval was 21 days from the last date when the plant last cleaned. This optimum cleaning interval reduces the total cost per unit energy generated by the PV plant and therefore, the levelized cost of electricity. However, the optimum cleaning interval may vary depending on the cost of the cleaning event as well as the seasonal variations in the soiling loss and energy generated. The cleaning schedule model developed can be used to determine when the PV plant should be cleaned. However, this model should be used as a guideline since soiling loss highly depends on the climate of the area and it is always changing.

  • 268. Wang, Xinru
    et al.
    Xia, Liang
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Copertaro, Benedetta
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Pan, Song
    Wu, Jinshun
    A systematic review of recent air source heat pump (ASHP) systems assisted by solar thermal, photovoltaic and photovoltaic/thermal sources2020In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 146, p. 2472-2487Article in journal (Refereed)
  • 269. Wei, Yixuan
    et al.
    Xia, Liang
    Pan, Song
    Wu, Jinshun
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Han, Mengjie
    Dalarna University, School of Technology and Business Studies, Statistics.
    Zhang, Weiya
    Xie, Jingchao
    Li, Qingping
    Prediction of occupancy level and energy consumption in office building using blind system identification and neural networks2019In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 240, p. 276-294Article in journal (Refereed)
    Abstract [en]

    Occupancy behaviour plays an important role in energy consumption in buildings. Currently, the shallow understanding of occupancy has led to a considerable performance gap between predicted and measured energy use. This paper presents an approach to estimate the occupancy based on blind system identification (BSI), and a prediction model of electricity consumption by an air-conditioning system is developed and reported based on an artificial neural network with the BSI estimation of the number of occupants as an input. This starts from the identification of indoor CO2 dynamics derived from the mass-conservation law and venting levels. The unknown parameters, including the occupancy and model parameters, are estimated by using a frequentist maximum-likelihood algorithm and Bayesian estimation. The second phase is to establish the prediction model of the electricity consumption of the air-conditioning system by using a feed-forward neural network (FFNN) and extreme learning machine (ELM), as well as ensemble models. To analyse some aspects of the benchmark test for identifying the effect of structure parameters and input-selection alternatives, three studies are conducted on (1) the effect of predictor selection based on principal component analysis, (2) the effect of the estimated occupancy as the supplementary input, and (3) the effect of the neural network ensemble. The result shows that the occupancy number, as the input, is able to improve the accuracy in predicting energy consumption using a neural network model.

  • 270. Wei, Yixuan
    et al.
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Shi, Yong
    Xia, Liang
    Pan, Song
    Wu, Jinshun
    Han, Mengjie
    Dalarna University, School of Technology and Business Studies, Microdata Analysis.
    Zhao, Xiaoyun
    Dalarna University, School of Technology and Business Studies, Microdata Analysis.
    A review of data-driven approaches for prediction and classification of building energy consumption2018In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 82, no 1, p. 1027-1047Article in journal (Refereed)
    Abstract [en]

    A recent surge of interest in building energy consumption has generated a tremendous amount of energy data, which boosts the data-driven algorithms for broad application throughout the building industry. This article reviews the prevailing data-driven approaches used in building energy analysis under different archetypes and granularities, including those methods for prediction (artificial neural networks, support vector machines, statistical regression, decision tree and genetic algorithm) and those methods for classification (K-mean clustering, self-organizing map and hierarchy clustering). The review results demonstrate that the data-driven approaches have well addressed a large variety of building energy related applications, such as load forecasting and prediction, energy pattern profiling, regional energy-consumption mapping, benchmarking for building stocks, global retrofit strategies and guideline making etc. Significantly, this review refines a few key tasks for modification of the data-driven approaches in the context of application to building energy analysis. The conclusions drawn in this review could facilitate future micro-scale changes of energy use for a particular building through the appropriate retrofit and the inclusion of renewable energy technologies. It also paves an avenue to explore potential in macro-scale energy-reduction with consideration of customer demands. All these will be useful to establish a better long-term strategy for urban sustainability.

  • 271.
    Weldemariam, Ashenafi
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Analyzing the Effect of Soiling on the Performance of a Photovoltaic System of Different Module Technologies in Kalkbult, South Africa2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The fact that most of the large scale solar PV plants are built in arid and semi-arid areas

    where land availability and solar radiation is high, it is expected the performance of the PV

    plants in such locations will be affected significantly due to high cell temperature as well as

    due to soiling. Therefore, it is essential to study how the different PV module technologies

    will perform in such geographical locations to ensure a consistent and reliable power

    delivery over the lifetime of the PV power plants.

    As soiling is strongly dependent on the climatic conditions of a particular location a test

    station, consisted of about 24 PV modules and a well-equipped weather station, was built

    within the fences of Scatec’s 75 MW Kalkbult solar PV plant in South Africa.

    This study was performed to a better understand the effect of soiling by comparing the

    relative power generation by the cleaned modules to the un-cleaned modules. Such

    knowledge can enable more quantitative evaluations of the cleaning strategies that are

    going to be implemented in bigger solar PV power plants.

    The data collected and recorded from the test station has been analyzed at IFE, Norway

    using a MatLab script written for this thesis project. This thesis work has been done at

    IFE, Norway in collaboration with Stellenbosch University in South Africa and Scatec

    Solar a Norwegian independent power producer company.

    Generally for the polycrystalline modules it is found that the average temperature

    corrected efficiency during the period of the experiment has been 15.00±0.08 % and for

    the thin film-CdTe with ARC is 11.52% and for the thin film without ARC is about

    11.13% with standard uncertainty of ±0.01 %.

    Besides, by comparing the initial relative average efficiency of the polycrystalline-Si

    modules when all the modules have been cleaned for the first time and the final relative

    efficiency; after the last cleaning schedule which is when all the reference modules E, F, G,

    and H have been cleaned for the last time it is found that poly3 performs 2 % and 3 %

    better than poly1 and poly16 respectively, poly13 performs 1 % better than poly15 as well

    as poly5 and poly12 performs 1 % and 2 % better than poly10 respectively. Besides, poly5

    and poly12 performs a 9 % and 11 % better than poly7. Furthermore, there is no change

    in performance between poly6 and poly9 as well as poly4 and poly15. However, the

    increase in performance of poly3 to poly1, poly13 to poly15 as well as poly5 and poly12 to

    poly10 is insignificant.

    In addition, it is found that TF22 perform 7% better than the reference un-cleaned module

    TF24 and similarly; TF21 performs 7% higher than TF23. Furthermore, modules with

    ARC glass (TF17, TF18, TF19, and TF20) shows that cleaning the modules with only

    distilled water (TF19) or dry-cleaned after cleaned with distilled water(TF20) decreases the

    performance of the modules by 5 % and 4 % comparing to its respective reference uncleanedmodules TF17 and TF18 respectively.

  • 272.
    Wilson, Jason Clifford
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    A techno-economic environmental approach to improving the performance of PV, battery, grid-connected, diesel hybrid energy systems: A case study in Kenya2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

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

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

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

  • 273.
    Win, Kaung Myat
    Dalarna University, School of Technology and Business Studies, Energy Technology. Mälardalens högskola.
    Emissions from realistic operation of residential wood pellets heating systems2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Emissions from residential combustion appliances vary significantly depending on the firing behaviours and combustion conditions, in addition to combustion technologies and fuel quality. Although wood pellet combustion in residential heating boilers is efficient, the combustion conditions during start-up and stop phases are not optimal and produce significantly high emissions such as carbon monoxide and hydrocarbon from incomplete combustion. The emissions from the start-up and stop phases of the pellet boilers are not fully taken into account in test methods for ecolabels which primarily focus on emissions during operation on full load and part load.

    The objective of the thesis is to investigate the emission characteristics during realistic operation of residential wood pellet boilers in order to identify when the major part of the annual emissions occur. Emissions from four residential wood pellet boilers were measured and characterized for three operating phases (start-up, steady and stop). Emissions from realistic operation of combined solar and wood pellet heating systems was continuously measured to investigate the influence of start-up and stop phases on total annual emissions. Measured emission data from the pellet devices were used to build an emission model to predict the annual emission factors from the dynamic operation of the heating system using the simulation software TRNSYS.

    Start-up emissions are found to vary with ignition type, supply of air and fuel, and time to complete the phase. Stop emissions are influenced by fan operation characteristics and the cleaning routine. Start-up and stop phases under realistic operation conditions contribute 80 – 95% of annual carbon monoxide (CO) emission, 60 – 90% total hydrocarbon (TOC), 10 – 20% of nitrogen oxides (NO), and 30 – 40% particles emissions. Annual emission factors from realistic operation of tested residential heating system with a top fed wood pelt boiler can be between 190 and 400 mg/MJ for the CO emissions, between 60 and 95 mg/MJ for the NO, between 6 and 25 mg/MJ for the TOC, between 30 and 116 mg/MJ for the particulate matter and between 2x10-13 /MJ and 4x10-13 /MJ for the number of particles. If the boiler has the cleaning sequence with compressed air such as in boiler B2, annual CO emission factor can be up to 550 mg/MJ. Average CO, TOC and particles emissions under realistic annual condition were greater than the limits values of two eco labels. These results highlight the importance of start-up and stop phases in annual emission factors (especially CO and TOC). Since a large or dominating part of the annual emissions in real operation arise from the start-up and stop sequences, test methods required by the ecolabels should take these emissions into account. In this way it will encourage the boiler manufacturers to minimize annual emissions.

    The annual emissions of residential pellet heating system can be reduced by optimizing the number of start-ups of the pellet boiler. It is possible to reduce up to 85% of the number of start-ups by optimizing the system design and its controller such as switching of the boiler pump after it stops, using two temperature sensors for boiler ON/OFF control, optimizing of the positions of the connections to the storage tank, increasing the mixing valve temperature in the boiler circuit and decreasing the pump flow rate. For 85 % reduction of start-ups, 75 % of CO and TOC emission factors were reduced while 13% increase in NO and 15 % increase in particle emissions was observed.

  • 274.
    Win, Kaung Myat
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Persson, Tomas
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Emissions from residential wood pellet boilers and stove characterized into start-up, steady operation and stop emissions2014In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 28, no 4, p. 2496-2505Article in journal (Refereed)
    Abstract [en]

    Gaseous and particulate emissions from three residential wood pellet boilers and a stove were characterized and quantified at start-up, steady (full, medium and low combustion power), and stop phases. The aim was to characterize the emissions during the different phases of boiler operation and to identify when the major part of the emissions occur to enable actions for emission reduction where the savings can be highest. The investigated emissions comprised carbon monoxide (CO), nitrogen oxide (NO), total organic carbon (TOC), and particulate matter (PM 2.5). In this study, particle emissions were characterized by both number and mass concentration. The emission characteristics at high combustion power were relatively similar for all tested devices while significant differences in CO and TOC were observed at lower combustion power. Highest CO and TOC emissions are produced by the bottom fed boiler at low combustion power. The accumulated start-up emissions of the tested devices varied in the ranges of 0.5−12 g CO, 0.1−0.7 g NO, 0.1−2 g TOC, 0.12−2.9 g PM2.5, and 2.4 × 1013 to 3.1 × 1014 particles PM2.5. The accumulated stop emissions varied in the ranges 4−15.5 g CO, 0.01−0.11 g NO, 0.02−1.6 g TOC, 0.1−1.3 g PM2.5, and 3.3 × 1013 to 1.4 × 1014 particles PM2.5. The bottom fed boiler B1 had higher start-up and stop emissions than the tested top fed boilers and more particle emissions were accumulated in start-up phase than in stop phases of boiler B1, B3, and stove S1. Number of particles emitted from residential wood pellet combustion is dominated by fine particles smaller than 1 μm and similar particle distribution both in number and mass were observed for the tested devices. The start-up phase generated higher accumulated particle mass than the stop phase.

  • 275. Wu, J.
    et al.
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Shen, Jingchun
    University of Nottingham, Ningbo.
    Wu, Y.
    Connelly, K.
    Yang, T.
    Tang, L.
    Xiao, M.
    Xu, P.
    Wang, H.
    A review of thermal absorbers and their integration methods for the combined solar photovoltaic/thermal (PV/T) modules2017In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 75, p. 839-854Article in journal (Refereed)
    Abstract [en]

    Thermal absorbers and their integration methods are critical to solar photovoltaic/thermal (PV/T) modules. These two elements directly influence the cooling effort of PV layers and as a result, the related electrical/thermal/overall efficiency. This paper conducts a critical review on the essential thermal absorbers and their integration methods for the currently-available PV modules for the purpose of producing the combined PV/T modules. A brief overview of different PV/T technologies is initially summarized, including aspects of their structure, efficiencies, thermal governing expressions and their applications. Seven different types of thermal absorbers and four corresponding integration methods are subsequently discussed and summarized in terms of their advantages/disadvantages and the associated application for various PV/T modules. Compared to traditional thermal absorbers, such as sheet-and-tube structure, rectangular tunnel with or without fins/grooves and flat-plate tube, these four types, i.e. micro-channel heat pipe array/heat mat, extruded heat exchanger, roll-bond heat exchanger and cotton wick structure, are promising due to the significant enhancement in terms of efficiency, structure, weight, and cost etc. The appropriate or suitable integration method varies in different cases, i.e. the ethylene-vinyl acetate (EVA) based lamination method seems the best option for integration of PV layer with thermal absorber when compared with other conventional methods, such as direct contact, thermal adhesive and mechanical fixing. Finally, suggestions for further research topics are proposed from five aspects. The overall research results would provide useful information for the assistance of further development of solar PV/T modules with high feasibility for widespread application in energy supply even at district or city-level in the near future. © 2016 Elsevier Ltd.

  • 276.
    Wäckelgård, Ewa
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Svedung, Harald
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Optical characterization and modelling of paint top-coatings for low-emittance applications2016In: Infrared physics & technology, ISSN 1350-4495, E-ISSN 1879-0275, Vol. 78, p. 275-281Article in journal (Refereed)
    Abstract [en]

    The study reports on characterization of low-infrared-emittance paint top-coatings for interior building applications in which the thermal radiation becomes important in comparison with thermal conductance. The top-coating that consist of a binder with aluminium flakes has been optically characterized in the infrared wavelength range in order to determine single flake and binder emittance from reflectance measurements. The single flake emittance was found to be 0.12 for non-leafing cornflake. The absorption coefficient that determines the binder emittance as a function of binder thickness was 0.060 [μm]−2 and 0.085 [μm]−2 for Lumiflon and polyester respectively. These results were used as parameters in a simple model of the flake-binder top-coating to investigate how the emittance of the top-coating was influence by the two components and compared with a state-of-art low-emittance commercial paint. It was found from the modelling that replacing the polyester binder with Lumiflon reduces the infrared emittance (at room temperature) from 0.36 to 0.30. Increasing flake reflectance from 0.88 to 0.96 and at the same time reduce flake thickness from 2 to 1 μm gives an emittance of 0.20. However, the real samples prepared with Lumiflon showed a severe degradation caused by the flakes floating up closer to the surface which indicates a viscosity problem that needs to be solved for practical use. Thinner flakes with higher reflectance can be found if vacuum metallised pigments are used instead of ball-milled.

  • 277. Xiao, M
    et al.
    Tang, L
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Yu-Fat-Lun, I
    Li, G
    Analysis on cooling technologies of concentrated solar power system: a review2017Conference paper (Refereed)
    Abstract [en]

    The application of the Concentrated Solar Power (CSP) system has attracted an ever-increasing attention with the deepening worldwide energy crisis. Operating temperature is one of the most important factors for CSP system that affects the solar photoelectric conversion efficiency. Reasonable cooling method cannot only decrease the operative temperature, balance flare inhomogeneity, also should display the characteristics of convenient installation, low power consumption and high reliability. Based on a comprehensive literature review, this work conducted a thorough compilation on different cooling techniques of CSP system. It includes the commonly used air cooling and water cooling, also illustrates the promising ground coupled cooling, impinging jet cooling, liquid immersion cooling, microchannel cooling, heat pipe cooling and Phase Change Material systems etc. Besides, the advantages and disadvantages of different cooling technologies are briefly analysed. It is expected that this paper could provide guidance for development and optimization of cooling technologies in CSP system.

  • 278. Xiao, Manxuan
    et al.
    Tang, Llewelly
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Lun, Isaac Yu Fat
    Yuan, Yanping
    A Review on Recent Development of Cooling Technologies for Concentrated Photovoltaics (CPV) Systems2018In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, no 12, article id 3416Article in journal (Refereed)
    Abstract [en]

    Concentrated Photovoltaics (CPV) technology, as an energy saving method which can directly generate electricity from the Sun, has attracted an ever-increasing attention with the deepening worldwide energy crisis. However, operating temperature is one of the main concerns that affect the CPV system. Excess cell temperature causes electrical conversion efficiency loss and cell lifespan decrease. Thus, reasonable cooling methods should decrease the operating temperature and balance the flare inhomogeneity. They also need to display high reliability, low power consumption, and convenient installation. This paper presented the architectural, commercial, and industrial usage of CPV system, reviewed the recent research developments of different cooling techniques of CPV systems during last few years, including the spectral beam splitting technology, cogeneration power technology, commonly used and promising cooling techniques, active and passive cooling methods. It also analysed the design considerations of the cooling methods in CPV systems, introduced the classification and basic working principles and provided a thorough compilation of different cooling techniques with their advantages, current research limitations, challenges, and possible further research directions. The aim of this work is to find the research gap and recommend feasible research direction of cooling technologies for CPV systems. 

  • 279. Xiong, Y
    et al.
    Bo, L
    Qiang, M
    Wu, Y
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology. University of Nottingham.
    Xu, P
    Ma, C
    A characteristic study on the start-up performance of molten-salt heat pipes: Experimental investigation2017In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 82, p. 433-438Article in journal (Refereed)
    Abstract [en]

    This paper reports a fundamental experimental investigation of the start-up characteristics of heat pipes using a dedicated molten-salt mixture as the working fluid. Based on four single salt, i.e. NaNO3(AR), KNO3(AR), LiNO3(AR) and Ca(NO3)2(AR), a quaternary molten-salt working fluid was developed and charged at different masses into four heat pipes with the same dimensions of 980 mm in length and 22 mm in diameter. A parallel comparison on the start-up performance of these heat pipes was then conducted to observe the influence of the charging mass and the inclination angle under the consistent lab-controlled conditions. The experimental results showed the heat pipe with molten-salt charge of 40 g responded much quicker than those with molten salt charge of 60 g, 70 g and 80 g respectively; meanwhile, the molten-salt heat pipe achieved the maximum condensation temperature at inclination angle of 50°. Comparing to the conventional naphthalene heat pipe, the dedicated molten-salt heat pipe had a much shorter start-up time when they were charged with the same amount of 40 g. The overall research result is expected to provide certain guidance for further design and operation of molten-salt heat pipe in high-and-medium-temperature heat transfer and storage scenarios. 

  • 280.
    Yeneneh, Getu Temasgen
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Testing of Apis System Platform in Grid-Connected Photovoltaic System and Comparison with Metrum for Fault Detection and Diagnosis2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A real time data management web-based software-platform for PV plant monitoring called Apis was tested for fault detection and diagnosis of large scale grid-connected photovoltaic systems. This method was compared with Metrum system which is also another web based monitoring system used in grid connected PV systems. The objective of testing and comparisons were to observe the Apis system performance in large scale PV systems particularly for fault detection, and to identify which of the two systems could give more information to easily identify type of fault and point out the fault location in PV plants.

    The experiment were carried out in the selected two different arrays that have a capacity of 18.4kW and 17.6 kW with four string inverters each, to test three cases at Glava energy center solar park, Sweden. The first demonstrates the response of the systems when the wiring loose or cable disconnection fault occurs in the plant. The second demonstrates the output of the inverters when partial shading is gradually increased and the third demonstrates the output when the fault at components (i.e. at inverter, fuse and circuit breaker) is applied. Both systems collect data from inverters. However, in Apis system, data from individual inverters of the plant could be collected separately in both AC and DC sides while Metrum system was measuring the total output of the whole inverters in the plant.

    During the string disconnection, the Apis monitoring system showed a power drop to zero from the defected strings making it possible to identify them. In the same way during the inverters’ fault the power output of the failed inverter was dropped to zero. However, the normal strings and inverters were still working properly. Meanwhile the Metrum system only displayed a reduced power output which doesn’t directly identify the problem and requires manual inspection. In the case of partial shading there was a persistent difference occurred between the defected string and normal one but it did not dropped to zero at all.

    Apis system is able to differentiate and locate the faults by comparing input and output results of different inverters within the plant, unlike Metrum system which measures the total output of the plant. Nevertheless, Apis system still has less possibility to determine the type of fault further than estimation.

  • 281. Yuan, Y
    et al.
    Ouyang, L
    Sun, L
    Cao, X
    Xiang, B
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Effect of connection mode and mass flux on the energy output of a PVT hot water system2017In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 158, p. 285-294Article in journal (Refereed)
  • 282. Yuhan, Z.
    et al.
    Jinshun, W.
    Mu, L.
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Lining, Z.
    Weiya, Z.
    Weijie, Z.
    Jun, W.
    Liang, X.
    Yixuan, W.
    Research on Operation Strategy of Solar Assisted Air Source Heat Pump System2019In: IOP Conference Series: Materials Science and Engineering, 2019, Vol. 56, no 1, article id 012028Conference paper (Refereed)
  • 283.
    Zare, Kourosh Abbas
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Development of a Predictive Control Model for a Heat Pump System Based on Artificial Neural Networks (ANN) approach2019Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
  • 284. Zhang, Nan
    et al.
    Chen, Xiangjie
    Su, Yuehong
    Zheng, Hongfei
    Ramandan, Omar
    Zhang, Xingxing
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Chen, Hongbin
    Riffat, Saffa
    Numerical investigations and performance comparisons of a novel cross-flow hollow fiber integrated liquid desiccant dehumidification system2019In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 182, p. 1115-1131Article in journal (Refereed)
    Abstract [en]

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

  • 285.
    Zhang, Xingxing
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Lovati, Marco
    Vigna, Ilaria
    Widén, Joakim
    Han, Mengjie
    Dalarna University, School of Technology and Business Studies, Microdata Analysis.
    Gál, Csilla V
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Feng, Tao
    A review of urban energy systems at building cluster level incorporating renewable-energy-source (RES) envelope solutions2018In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 230, p. 1034-1056Article in journal (Refereed)
    Abstract [en]

    The emergence of renewable-energy-source (RES) envelope solutions, building retrofit requirements and advanced energy technologies brought about challenges to the existing paradigm of urban energy systems. It is envisioned that the building cluster approach—that can maximize the synergies of RES harvesting, building performance, and distributed energy management—will deliver the breakthrough to these challenges. Thus, this paper aims to critically review urban energy systems at the cluster level that incorporate building integrated RES solutions. We begin with defining cluster approach and the associated boundaries. Several factors influencing energy planning at cluster scale are identified, while the most important ones are discussed in detail. The closely reviewed factors include RES envelope solutions, solar energy potential, density of buildings, energy demand, integrated cluster-scale energy systems and energy hub. The examined categories of RES envelope solutions are (i) the solar power, (ii) the solar thermal and (iii) the energy-efficient ones, out of which solar energy is the most prevalent RES. As a result, methods assessing the solar energy potentials of building envelopes are reviewed in detail. Building density and the associated energy use are also identified as key factors since they affect the type and the energy harvesting potentials of RES envelopes. Modelling techniques for building energy demand at cluster level and their coupling with complex integrated energy systems or an energy hub are reviewed in a comprehensive way. In addition, the paper discusses control and operational methods as well as related optimization algorithms for the energy hub concept. Based on the findings of the review, we put forward a matrix of recommendations for cluster-level energy system simulations aiming to maximize the direct and indirect benefits of RES envelope solutions. By reviewing key factors and modelling approaches for characterizing RES-envelope-solutions-based urban energy systems at cluster level, this paper hopes to foster the transition towards more sustainable urban energy systems.

  • 286.
    Zhang, Xingxing
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Pan, Song
    Wu, Jinshun
    Xia, Liang
    China leans balance to distributed solar-power projects: challenge and opportunities2017Conference paper (Refereed)
  • 287.
    Zhang, Xingxing
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Pan, Song
    Wu, Jinshun
    Xia, Liang
    Recycling discarded shipping containers for reliable building envelopes: a design case for senior citizens in Solar Decathlon China 20172017Conference paper (Refereed)
  • 288.
    Zhang, Xingxing
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Wang, X.
    Zhao, Xiaoyun
    Dalarna University, School of Technology and Business Studies, Microdata Analysis.
    Solar System Design and Energy Performance Assessment Approaches2019In: Advanced Energy Efficiency Technologies for Solar Heating, Cooling and Power Generation, Springer, 2019, p. 417-451Chapter in book (Refereed)
    Abstract [en]

    Recently, solar system has gained a rapid development in many countries because it is clean and sustainable. Many solar systems including the solar photovoltaic/loop-heat-pipe (PV/LHP), solar loop-heat-pipe (LHP), solar photovoltaic/micro-channel heat pipe (PV/MCHP) system, and solar thermal facade system (STF) have been designed for energy saving. To assess these systems’ performance, there are many approaches such as energy and exergy assessment which is used in this chapter to analyze their performance. Besides the system design, the authors set up dedicated experimental models in combination with computer models to test the systems’ performance. Furthermore, some systems are compared with the conventional system, and the performance of these solar systems is better than the conventional system. In addition, these solar systems are applied in many real buildings and their performance is examined, the results show that the solar systems have more potential to boost the building energy efficiency and create the possibility of solar development in buildings. © 2019, Springer Nature Switzerland AG.

  • 289.
    Zhang, Xingxing
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Wei, Y.
    He, W.
    Qiu, Z.
    Zhao, Xiaoyun
    Dalarna University, School of Technology and Business Studies, Microdata Analysis.
    Solar Systems’ Economic and Environmental Performance Assessment2019In: Advanced Energy Efficiency Technologies for Solar Heating, Cooling and Power Generation / [ed] Xudong Zhao, Xiaoli Ma, Springer, 2019, p. 453-486Chapter in book (Refereed)
    Abstract [en]

    The economic and environmental performance assessment of the solar system plays a critical role in building design, operation and retrofit. A dedicated economic model is necessary to assess the investment feasibility on a new technology, which allows investors to decide on a profitable investment, compare investment projects and know about the benefits of the best investment. An environmental model is adopted to predict carbon emission reduction in the solar system relative to the traditional heating and electronic systems. This chapter introduced three up-to-date solar system models and corresponding assessments related to their applications, including solar photovoltaic/loop heat pipe (PV/LHP) heat pump water heating system, loop heat pipe-based solar thermal facade (LHP-STF), heat pump water heating system as well as solar thermal facade (STF). The research results will be able to assist in decision-making in implementation of the proposed PV/T technology and analyses of the associated economic and environmental benefits, thus contributing to realization of regional and global targets on fossil fuel energy saving and environmental sustainability.

  • 290.
    Zhang, Xingxing
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Wu, J.
    Pan, S.
    Han, Mengjie
    Dalarna University, School of Technology and Business Studies, Microdata Analysis.
    An economic analysis of the solar photovoltaic/thermal (PV/T) technologies in Sweden: A case study2019In: IOP Conference Series: Materials Science and Engineering, 2019, Vol. 556, no 1, article id 012002Conference paper (Refereed)
  • 291.
    Zhang, Xingxing
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Wu, J
    Zhang, Y
    Pan, S
    Wei, Y
    Xia, L
    Zhang, W
    Numerical study on thermal performance of a gravity assisted loop heat pipe2017Conference paper (Refereed)
    Abstract [en]

    This article carried out a parametric study of the thermal performance of a novel gravity assisted loop heat pipe (GALHP)with composite mesh-screen wick structure. A refined three-way structure with interior liquid-vapour separator wasdeveloped on top of the evaporator to enable a gravity-assisted operation, which not only simplified the correspondingwick structure but also eliminated the ‘dry-out’ potential in conventional GALHPs. A dedicated simulation model wasdeveloped on basis of the heat transfer and the flow characteristics derived from the governing equations of mass, energyand momentum. The essential impact parameters to the GALHP thermal performance were further discussed. It was foundthat the GALHP thermal performance, represented by the reciprocal of overall thermal resistance, varies directly withapplied heat load, evaporator diameter, and vapour-liquid separator diameter. The research results would be useful fordesign, optimisation and application of such GALHP in the gravity-assisted circumstance for thermal management.

  • 292.
    Zhang, Xingxing
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Xiao, M.
    He, W.
    Qiu, Z.
    Zhao, Xiaoyun
    Dalarna University, School of Technology and Business Studies, Microdata Analysis.
    Heat Pump Technologies and Their Applications in Solar Systems2019In: Advanced Energy Efficiency Technologies for Solar Heating, Cooling and Power Generation / [ed] Xudong Zhao, Xiaoli Ma, Springer, 2019, p. 311-339Chapter in book (Refereed)
    Abstract [en]

    As the well known that global energy demand is on a trend of continuous growth, reducing energy demand and making good use of renewable energy are thought to be the major routes toward low carbon and sustainable future, in particular for the building sector. Compared to traditional gas-fired heating systems, heat pumps have been proved to be an energy-efficient heating technology which can save fossil fuel energy and consequently reduce CO2 emission. However, the most outstanding challenges for the application of heat pumps lie in their high demand for electrical power, and the insufficient heat transfer between the heat source and the refrigerant. To overcome these difficulties, a solar-assisted heat pump has been proposed to tackle these challenges. A solar-assisted heat pump combines a heat pump with a solar collector, enabling the use of solar energy to provide space heating and hot water for buildings. This chapter introduces heat pump technologies and their applications in solar systems. Two types of solar-assisted heat pump, direct and indirect expansion, are illustrated in details. This work has provided the fundamental research and experience for developing a solar heat pump system and contributing to a significant fossil fuel saving and carbon reduction in the global extent.

  • 293. Zhu, Chaoyi
    et al.
    Gluesenkamp, Kyle R
    Yang, Zhiyao
    Blackman, Corey
    Dalarna University, School of Technology and Business Studies, Energy Technology. SaltX Technology; Mälardalens högskola.
    Unified thermodynamic model to calculate COP of diverse sorption heat pump cycles: Adsorption, absorption, resorption, and multistep crystalline reactions2019In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 99, p. 382-392Article in journal (Refereed)
    Abstract [en]

    A straightforward thermodynamic model is developed in this work to analyze the efficiency limit of diverse sorption systems. A method is presented to quantify the dead thermal mass of heat exchangers Solid and liquid sorbents based on chemisorption or physical adsorption are accommodated. Four possible single-effect configurations are considered: basic absorption or adsorption (separate desorber, absorber, condenser, and evaporator); separate condenser/evaporator (two identical sorbent-containing reactors with a condenser and a separate direct expansion evaporator); combined condenser/evaporator (one salt-containing reactor with a combined condenser/evaporator module); and resorption (two sorbent-containing reactors, each with a different sorbent). The analytical model was verified against an empirical heat and mass transfer model derived from component experimental results. It was then used to evaluate and determine the optimal design for an ammoniate salt-based solid/gas sorption heat pump for a space heating application. The effects on system performance were evaluated with respect to different working pairs, dead thermal mass factors, and system operating temperatures. The effect of reactor dead mass as well as heat recovery on system performance was also studied for each configuration. Based on the analysis in this work, an ammonia resorption cycle using LiCl/NaBr as the working pair was found to be the most suitable single-effect cycle for space heating applications. The maximum cycle heating coefficient of performance for the design conditions was 1.50 with 50% heat recovery and 1.34 without heat recovery.

    The full text will be freely available from 2020-06-30 23:36
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