uu.seUppsala universitets publikasjoner
Endre søk
Begrens søket
1234567 51 - 100 of 608
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Treff pr side
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 51.
    Broström, Tor
    Tekniska högskolan i Stockholm. Institutionen för energiteknik.
    Uppvärmning i kyrkor: fukt- och värmetekniska beräkningar för dimensionering och klimatstyrning1996Doktoravhandling, monografi (Annet vitenskapelig)
  • 52.
    Broström, Tor
    et al.
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    Hagentoft, Carl-Eric
    Chalmers University of Technology.
    Wessberg, Magnus
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    Humidity Control in Historic Buildings through Adaptive Ventilation: a Case Study2011Inngår i: NSB 2011: 9th Nordic Symposium on Building Physics, 2011, s. 1-8Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Adaptive ventilation, controlled with respect to absolute humidity inside and outside a building, canbe used to reduce RH below risk levels for biodeterioration. In the present case study, adaptiveventilation was used in a historic stone building with severe moisture problems. Measurementscarried out over a year shows that ventilation had a significant drying effect. The mould risk is keptat an acceptable level with exception of two short periods .Short term variations in RH are acceptableaccording to conservation standards. Heating or dehumidification as an auxiliary measure would beneeded only for a short period of time. The performance can be improved by increased fan capacityand improving air tightness of the building.

  • 53.
    Broström, Tor
    et al.
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    Klenz Larsen, Poul
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    Climate control strategies for occasionally used churches: heat, dehumidify, ventilate – or do nothing2012Inngår i: Cultural heritage preservation : EWCHP- 2012: proceedings of the 2nd European workshop on cultural heritage preservation / [ed] Elin Dahlin, Kjeller: NILU, Norwegian Institute for Air Research , 2012, s. 124-130Konferansepaper (Fagfellevurdert)
  • 54.
    Broström, Tor
    et al.
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    Leijonhufvud, Gustaf
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    Heat pumps for conservation heating2008Inngår i: Proceedings of the 8th symposium on building physics in the Nordic countries: Copenhagen, June 16-18, 2008 / [ed] Carsten Rode, Lyngby: Technical university of Denmark , 2008, s. 1143-1150Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Conservation heating is used to control relative humidity in order to better preserve historic buildings and their interiors. The heating load for conservation heating when applied in a Nordic climate was characterized in order to investigate if and how air-to-air heat pumps can be used for conservation heating. Heating for conservation results in indoor temperatures that follow the seasonal variation of the outdoor temperature. Depending on the season and moisture load on the building, the indoor temperature will be 0-10 °C higher than the ambient temperature. The heating load is much smaller and more stable over the year as compared to heating for comfort. In the south of Sweden conservation heating is motivated mainly by preservation aspects, whereas in northern Sweden the potential for energy saving is considerable. Heat pumps in general and air-to air heat pumps in particular, have properties that match the requirements of conservation heating and can provide a cost effective solution. Heat pumps specially designed for conservation heating could improve the performance radically in relation to standard heat pumps.

  • 55.
    Broström, Tor
    et al.
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    Leijonhufvud, Gustaf
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    Hållbarhet och byggnadsvård2011Inngår i: Energiboken: energieffektivisering för småhusägare / [ed] Eva Löfgren & Paul Hansson, Stockholm: Svenska byggnadsvårdsföreningen , 2011, s. 34-45Kapittel i bok, del av antologi (Annet (populærvitenskap, debatt, mm))
  • 56.
    Broström, Tor
    et al.
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    Leijonhufvud, Gustaf
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    The Indoor Climate in Skokloster Castle2010Inngår i: Historical buildings as museums: Systems for climate control and heritage preservation / [ed] Davide Del Curto, Firenze: Nardini Editore , 2010, s. 84-93Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Skokloster castle is a heavy stone and brick building without any active climatization. It houses a large collection of artefacts shown in their historic environment without any showcases. The objective of this study is to analyse the indoor climate, make a risk assessment and to propose interventions to improve the indoor climate with respect to the long term preservation of the collection. Relative humidity and temperature have been monitored within the castle for more than one year. Air exchange in selected rooms has been measured quarterly using diffusive sampling. The indoor climate is characterized by extremely low temperatures and high relative humidity in the winter. Even though the building does reduce the effect of outdoor variations, the variations in the indoor climate are larger than one would prefer in a museum. The primary risks associated with the indoor climate are mould growth, mechanical damages and chemical degradation. The variations in RH can be reduced by enhancing the effective hygrothermal inertia of the building through a reduction of the air exchange. In order to substantially reduce the mould risk, conservation heating and/or dehumidification would be needed.

  • 57.
    Broström, Tor
    et al.
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    Linden, Elisabet
    University of Gavle, Department of Built Environment.
    Lindström, Svante
    University of Gavle, Department of Built Environment.
    Mattsson, Magnus
    University of Gavle, Department of Built Environment.
    Sandberg, Mats
    KTH Research School, University of Gavle.
    Convective heating in a medieval church: Effects of air-to-air heat pumps on air movements, particle deposition and temperature distribution2009Inngår i: Proceedings of the 11th International Conference on Air Distribution in Rooms (Roomvent) 2009, Busan, Korea, 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In Europe many historic buildings use direct electric heating. Air-to-air heat pumps are an interesting alternative, in particular for conservation heating. However, the convective heating may accelerate soiling of walls and artefacts by increasing the velocity and turbulence. The objective of the present paper is to discuss the general problem, the methodology for studying air motions and temperature distribution, and to present the results from a case study where air-to-air heat pumps and bench heaters were used for heating in a medieval church. The temperatures, velocities and humidity in the church have been measured for four different heating modes. The present study does not indicate any major disadvantages of using heat pumps for background heating in stone churches of the studied kind. More detailed long term studies are needed to ascertain the effects over time.

  • 58.
    Broström, Tor
    et al.
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    Nilsen, Lisa
    Energy Efficiency in Historic Buildings: Postprints from the Conference : Visby, February 9–11, 20112012Konferanseproceedings (Annet vitenskapelig)
    Abstract [en]

    Energy efficiency is an issue that brings the trade-off between aspects of use and preservation to a head. On the one hand, interventions for energy efficiency facilitate long-term use by reducing operating costs; on the other hand, the interventions may have both a physical and a visual impact on the cultural heritage value and the fabric of the building.

    In order to promote a sustainable use and preservation of historic buildings, The Swedish Energy Agency instituted a National Research Program for Energy Efficiency in HistoricBuildings. The first stage of the program ranfrom 2007 to 2010 with a total budget of around 4 million Euro. Additional funding was provided by the Church of Sweden and the NationalHeritage Board. There were fifteen projects involving some thirty researchers from different Swedish universities and research institutes.

    To mark the end of the first stage of the national research program the international conference Energy Efficiency in Historic Buildings was held in Visby in February 2011. Most of the projects within the program were presented at the conference and international key-note speakers were invited to each session, giving a total of 24 papers. More than one hundred participants, representing ten countries, participated in the conference.

  • 59.
    Broström, Tor
    et al.
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Historisk-filosofiska fakulteten, Konstvetenskapliga institutionen, Kulturvård.
    Nilsen, LisaLisa Nilsen Kulturvård, Stockholm.Carlsten, SusannaUppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Historisk-filosofiska fakulteten, Konstvetenskapliga institutionen, Kulturvård.
    Conference Report: The 3rd International Conference on Energy Efficiency in Historic Buildings2018Konferanseproceedings (Fagfellevurdert)
    Abstract [en]

    We proudly present the postprints of the third International Conference on Energy Efficiency in Historic Buildings, held in Visby, Sweden September 26th to 27th, 2018.

    The conference was organized jointly by the Swedish Energy Agency, Uppsala University and the Swedish National Heritage Board as part of their collaboration in the Swedish national research program on energy efficiency in historic buildings. The Region of Gotland kindly sponsored the conference dinner.

    There were close to one hundred abstracts submitted to the conference. We gratefully acknowledge the contributions from the Scientific Committee in the review process.

    Our thanks to Lisa Nilsen who has been the conference coordinator and editor of the papers, Susanna Carlsten who has been in charge of information and conference planning and Alice Sunnebäck who finished the layout of the papers and the report as a whole.

    The organizing committee for EEHB2018,

    Tor Broström Uppsala University

    Jörgen Sjödin Swedish Energy Agency

    Camilla Altahr-Cederberg Swedish National Heritage Board

  • 60.
    Broström, Tor
    et al.
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    Nilsson, Håkan
    WSP Environmental, Department of Building Physics.
    Climate Comfort Measurements in Swedish Churches Equipped with New Heating System2008Inngår i: Proceedings of the 7th International Thermal Manikin and Modeling Meeting, University of Coimbra , 2008Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Many church buildings in Sweden have problems with rising heating costs combined with deterioration of inventories as a consequence of an inappropriate indoor climate. Gotland University has in collaboration with Gotland's churches installed a new radiant heating system for churches. The developed system has floor heating and bench heating pads combined with radiant heaters hanging from above the bench rows. These new installations have now been evaluated with respect to thermal climate comfort. The results show that the clothing of course plays an important role even with help radiant heaters and bench heat pads. Persons on both sides of the instrument as well as the height of the heaters do seem to play a smaller role in this investigation. An important parameter to check is the risk for drought that clearly is dependent on of the construction of the church benches.

  • 61.
    Broström, Tor
    et al.
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    Nordström, Anders
    Historiska Hus, Umeå, Sweden.
    Climate Control in Churches in Northern Sweden2009Inngår i: Proceedings Cold Climate HVAC Sisimiut, Greenland, 16-19 March 2009, 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In the extreme north of Sweden, the indoor climate and energy performance of 50 churches is being monitored in order to improve energy efficiency and to improve the indoor climate with respect to the preservation. The objective of the present paper is to investigate if and how both indoor climate and energy efficiency can be improved through better climate control. Three cases were chosen to study churches with no heating, permanent heating and intermittent heating. In each case the actual indoor climate was compared to climate criteria for preservation to determine the consequences in terms of climate control. The results show that there is a conflict between the climate criteria for preservation and the present use of the churches that cannot be resolved by technical solutions only. In order to come up with reasonable compromise research is needed on climate criteria and risk management at extremely low ranges of RH.

  • 62.
    Broström, Tor
    et al.
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    Svanström, Karin
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    Solar energy and cultural-heritage values2011Inngår i: World Renewable Energy Conference, Linköping, May 2011: Volume 8 (Low-Energy Architecture) / [ed] Moshfegh, Bahram, Linköping: Linköping University Electronic Press, 2011, s. 2034-2040Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The use of solar energy in a building of cultural-heritage value is an issue that brings the trade-off between aspects of use and preservation to a head. A sustainable use and preservation of historic buildings requires broad and long term compromises between social, economic and environmental aspects. The objective of the present paper is to present and discuss a decision framework for such compromises regarding the use of solar energy in historic buildings.

  • 63.
    Brunskog, Maria
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    Energieffektivisering i byggnader av kulturhistoriskt intresse med avseende på kyrkor i Luleå stift2011Rapport (Annet vitenskapelig)
  • 64. Bughrara, K.S.M.
    et al.
    Durmuş Arsan, Z.
    Gökçen Akkurt, G.
    Effect of intervention strategies on seasonal thermal comfort conditions in a historic mosque in the Mediterranean climate2018Inngår i: Conference Report: The 3rd International Conference on Energy Efficiency in Historic Buildings / [ed] Tor Broström, Lisa Nilsen and Susanna Carlsten, Uppsala University, 2018, s. 363-371Konferansepaper (Fagfellevurdert)
  • 65. Burgholzer, J.
    et al.
    Héberlé, E.
    Valkhoff, H.
    Costes, J.P.
    Borderon, J.
    Development of a knowledge centre for responsible retrofit of traditional buildings in France2018Inngår i: Conference Report: The 3rd International Conference on Energy Efficiency in Historic Buildings / [ed] Tor Broström, Lisa Nilsen and Susanna Carlsten, Uppsala University, 2018, s. 274-282Konferansepaper (Fagfellevurdert)
  • 66.
    Bydell, Linn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Evaluation of the thermal-hydraulic software GOTHIC for nuclear safety analyses2013Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    The aim of this master theses was to evaluate the thermal-hydraulic calculation software GOTHIC for the purpose of nuclear containment safety analyses. The evaluation was performed against some of the Marviken full scale containment experiments and a comparison was also made against the two codes RELAP5 and COPTA. Models with different complexity were developed in GOTHIC and the parameters pressure, temperature and energy in different areas of the enclosure was investigated.

    The GOTHIC simulations in general showed a good agreement with the Marviken experimental results and had an overall better agreement then RELAP5. From the results it was possible to conclude that the developed GOTHIC model provided a good representation of the Marviken facility. 

  • 67. Båverman, Gabriel
    et al.
    Tavoosi, Edris
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Evaluation of a solar powered water pumping system in Mutomo, Kenya: Comparison between a submersible induction motor and a PMSM system2019Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    An existing solar-powered water pumping system located in Mutomo, Kenya has beenevaluated in this paper. The requirement for this system is to produce a minimum of25m³ water per day throughout the year.The aim of this thesis is to investigate theperformance of the currently installed system and find a suitable replacement in termsof efficiency and economic viability. In order to acquire the necessary knowledge forthis project, a literature study was carried out to analyse the research within the area.Three simulation models were created which all include an electric motor driven by aphotovoltaic array and are connected to a submersible groundwater pump. Allmodels utilise space vector pulse width modulation. One model of an inductionmotor that represents the currently installed system, one induction motor thatdelivers a minimum of 25 m³ water per day, and one model of a permanent magnetsynchronous motor for comparison. Simulations using weather data, representing anaverage day for each month of the year were carried out. It was shown that thecurrently installed system does not fulfil the requirement of producing 25 m³ waterper day, and in addition produces a significant amount of energy that can not beutilised. It was also shown that the efficiency of the permanent magnet synchronousmotor was superior to the induction motors. In order to compare the systems interms of economic viability, price quotations from world leading manufacturers wereacquired. The results of the economic comparison show that the superior efficiencyof the permanent magnet synchronous motor was not enough to compensate for thehigher investment cost.

  • 68.
    Bülow, Fredrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    A Generator Perspective on Vertical Axis Wind Turbines2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The wind energy conversion system considered in this thesis is based on a vertical axis wind turbine with a cable wound direct drive PM generator. Diode rectifiers are used to connect several such units to a single DC-bus and a single inverter controls the power flow from the DC-bus to a utility grid. This work considers the described system from a generator perspective i.e. the turbine is primarily seen as a torque and the inverter is seen as a controlled load.

    A 12 kW VAWT prototype with a single turbine has been constructed within the project. The power coefficient of this turbine has been measured when the turbine is operated at various tip speed ratios. This measurement determines both how much energy the turbine can convert in a given wind and at what speed the turbine should be operated in order to maximise the energy capture. The turbine torque variation during the revolution of the turbine has also been studied.

    A PM generator prototype has been constructed in order to study power loss in the stator core at low electrical frequencies. Heat exchange between the stator and the air-gap between the stator and the rotor has been studied. Heat exchange between the stator and the air-gap is increased by turbulence caused by the rotor. The generator was also used in a demonstration of a DC-grid where two diode rectified PM generators supplied power to a single DC load.  An initial study of an inverter suitable for grid connection of the 12 kW PM generator has been performed.

    Several turbine control strategies are evaluated in simulations. The control strategies only require the parameter "turbine speed" to determine the optimal system load.

    Delarbeid
    1. Offshore underwater substation for wave energy converter arrays
    Åpne denne publikasjonen i ny fane eller vindu >>Offshore underwater substation for wave energy converter arrays
    Vise andre…
    2010 (engelsk)Inngår i: IET Renewable Power Generation, ISSN 1752-1416, Vol. 4, nr 6, s. 602-612Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    In this study, the design, construction, deployment and operation of an offshore underwater substation is discussed. The seabed placed substation interconnects three linear generator wave energy converters (WECs) at the Swedish Lysekil wave energy research site. The power from the WECs fluctuates because of their direct-driven topology. The generator voltage has varying electrical frequency and amplitude. To reduce the fluctuations, the individual voltages of the WECs are rectified and the power is added on a common DC-bus in the substation. The voltage is inverted, transformed and power is transmitted to an on-shore resistive load. The substation was retrieved on two occasions since the deployment in the spring of 2009. The functionality of the substation is validated by comparing voltage and current wave forms from Simulink with measured results from laboratory experiments. In addition, a sample of results from real offshore operation is illustrated and discussed. With a proportional-integral-derivative (PID)-regulator in the inverter control, the small fluctuations in the DC-bus voltage could be minimised. However, this would reduce the energy storage capability of the DC-link smoothing capacitors.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-112954 (URN)10.1049/iet-rpg.2009.0180 (DOI)000284511300013 ()
    Tilgjengelig fra: 2010-01-22 Laget: 2010-01-22 Sist oppdatert: 2018-05-31bibliografisk kontrollert
    2. Power coefficient measurement on a 12 kW straight bladed vertical axis wind turbine
    Åpne denne publikasjonen i ny fane eller vindu >>Power coefficient measurement on a 12 kW straight bladed vertical axis wind turbine
    Vise andre…
    2011 (engelsk)Inngår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 36, nr 11, s. 3050-3053Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    A 12 kW vertical axis H-rotor type wind turbine has been designed and constructed at Uppsala University. A measurement campaign has been performed to collect data to calculate the power coefficient using the method of bins. The measurement was performed at different constant rotational speeds on the turbine during varying wind speeds to observe the power coefficients dependence on tip speed ratio. The power coefficient peaked at 0.29 for a tip speed ratio equal to 3.3.

    Emneord
    VAWT, H-rotor, Experimental, Measured, Cp
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-156579 (URN)10.1016/j.renene.2011.03.031 (DOI)000292441400035 ()
    Tilgjengelig fra: 2011-08-07 Laget: 2011-08-04 Sist oppdatert: 2018-05-30bibliografisk kontrollert
    3. Adapting a VAWT with PM generator to telecom applications
    Åpne denne publikasjonen i ny fane eller vindu >>Adapting a VAWT with PM generator to telecom applications
    Vise andre…
    2010 (engelsk)Inngår i: European Wind Energy Conference & Exhibition, Warsaw, Poland, 2010Konferansepaper, Publicerat paper (Fagfellevurdert)
    sted, utgiver, år, opplag, sider
    Warsaw, Poland: , 2010
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-142522 (URN)
    Konferanse
    European Wind Energy Conference & Exhibition
    Tilgjengelig fra: 2011-01-14 Laget: 2011-01-14 Sist oppdatert: 2018-05-30bibliografisk kontrollert
    4. No-load core loss prediction of PM generator at low electrical frequency
    Åpne denne publikasjonen i ny fane eller vindu >>No-load core loss prediction of PM generator at low electrical frequency
    2012 (engelsk)Inngår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 43, s. 389-392Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    A method for measurement of frequency dependent electromagnetic core loss of a permanent magnet generator is presented. Core loss of a PM generator is measured at electrical frequencies ranging from 4 to 14 Hz. Core loss in the same interval is simulated using the finite element method and frequency domain loss separation. The specific loss is both extrapolated from specific loss at 50 Hz and measured directly at 4, 8, 12 and 16 Hz. Core loss simulations based on extrapolated specific loss are 38–53% smaller than measured loss. Core loss simulations based on specific loss measured at 4, 8, 12 and 16 Hz are 19–23% smaller than measured loss.

    Emneord
    Core loss Variable speed PM generator Cable wound generator Loss separation
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-190099 (URN)10.1016/j.renene.2011.12.002 (DOI)000301311500042 ()
    Tilgjengelig fra: 2013-01-07 Laget: 2013-01-07 Sist oppdatert: 2017-12-06bibliografisk kontrollert
    5. Robust VAWT control system evaluation by coupled aerodynamic and electrical simulations
    Åpne denne publikasjonen i ny fane eller vindu >>Robust VAWT control system evaluation by coupled aerodynamic and electrical simulations
    2013 (engelsk)Inngår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 59, s. 193-201Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    A control system for a vertical axis wind turbine is presented.The control strategy is to determine the electric load solely from the rotational velocity and the characteristics of the turbine, thus measurement of the incoming wind velocity is not required.The control system is evaluated with an aerodynamic vortex model coupled with an electrical model.Three different sets of control system parameters are tested, due to the trade off between high power absorption and achieving a fast system with high stability.The control systems are tested against a reference strategy where the wind speed is known.The simulations show that the three control systems provide a similar power absorption as the reference case.For dynamic cases, with fast changes in wind speed, the fast control strategies are beneficial.All control strategies are stable throughout the simulations when proper power absorption characteristics of the turbine are used. It is also shown that if peak power absorption is estimated at a too low tip speed ratio, the control strategies may inadvertently stop the turbine.

    sted, utgiver, år, opplag, sider
    Elsevier, 2013
    Emneord
    Wind power, VAWT, Darrieus Turbine, Control system, Numerical simulation, Vortex method
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-183738 (URN)10.1016/j.renene.2013.03.038 (DOI)000320827300024 ()
    Tilgjengelig fra: 2012-11-01 Laget: 2012-11-01 Sist oppdatert: 2017-12-07bibliografisk kontrollert
    6. Aerodynamic and electrical evaluation of a VAWT farm control system with passive rectifiers and mutual DC-bus
    Åpne denne publikasjonen i ny fane eller vindu >>Aerodynamic and electrical evaluation of a VAWT farm control system with passive rectifiers and mutual DC-bus
    2013 (engelsk)Inngår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 60, s. 284-292Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    A wind farm with a simple electrical topology with passive rectifiers and a single inverter (mutual topology) is compared to a more complex topology where each turbine has a separate inverter (separate topology).In both cases, the turbines are controlled electrically by varying the extracted power with the rotational velocity as control signal.These two electrical topologies are evaluated with respect to absorbed power for a farm of four turbines placed either on a line or in a square formation.The evaluation is done with an aerodynamic vortex model coupled with an electrical system model.Simulations predict that individual control is beneficial for aerodynamically independent turbines if flow velocities differ significantly between turbines. If the differences in flow velocities are caused by one turbine operating in the wake of another, the deviations in power output between the topologies are less prominent.The mutual topology even deliver more power than the separate topology when one turbine is in the wake of another turbine if the wind speed changes rapidly.

    sted, utgiver, år, opplag, sider
    Elsevier, 2013
    Emneord
    Wind power, Wind farm, VAWT, Vortex model, Control system
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-183739 (URN)10.1016/j.renene.2013.05.028 (DOI)000323628600031 ()
    Tilgjengelig fra: 2012-11-01 Laget: 2012-11-01 Sist oppdatert: 2017-12-07bibliografisk kontrollert
    7. Torque ripple of a straight-bladed Darrieus turbine with PM generator estimated from diode rectifier output current.
    Åpne denne publikasjonen i ny fane eller vindu >>Torque ripple of a straight-bladed Darrieus turbine with PM generator estimated from diode rectifier output current.
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-197853 (URN)
    Tilgjengelig fra: 2013-04-05 Laget: 2013-04-05 Sist oppdatert: 2013-08-30
    8. Stator cooling by axial flow through air-gap of high torque PM generator.
    Åpne denne publikasjonen i ny fane eller vindu >>Stator cooling by axial flow through air-gap of high torque PM generator.
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-197854 (URN)
    Tilgjengelig fra: 2013-04-05 Laget: 2013-04-05 Sist oppdatert: 2013-08-30
    9. Laboratory verification of system for grid connection of a 12 kW variable speed wind turbine with a permanent magnet synchronous generator
    Åpne denne publikasjonen i ny fane eller vindu >>Laboratory verification of system for grid connection of a 12 kW variable speed wind turbine with a permanent magnet synchronous generator
    2012 (engelsk)Inngår i: EWEA 2012 Annual Event, Copenhagen, Denmark, 2012, 2012Konferansepaper, Poster (with or without abstract) (Fagfellevurdert)
    Abstract [en]

    In this paper the first laboratory tests of the gridconnection system, connected to a resistiveload, for a vertical axis wind turbine (VAWT)with a permanent magnet generator arepresented. The system is based on a taptransformertopology with a voltage sourceinverter and an LCL-filter. The use of a taptransformer topology eliminates the need for aDC-DC converter to handle the variations inDC voltage. The harmonic content of thecurrents from experiments and simulationsperformed in Simulink using different taps onthe transformer are presented. The simulatedcurrents, fed to the resistive load, have a totalharmonic distortion (THD) of 0.5% to 0.9% forthe different taps. The experimental systemhas a current THD ranging from 1.8% to 2.8%.The difference is expected to be due tounbalances, delays and dead times in theexperimental set-up as the major THDcontribution is from harmonic orders below 11.The results show that an LCL filter can bedesigned to meet the demands on powerquality for grid connection of the system withall the taps of the tap transformer inaccordance with IEEE 519-1992.

    Emneord
    VAWT, Tap transformer, LCL-filter, voltage source inverter
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-182434 (URN)
    Konferanse
    EWEA 2012 Annual Event, Copenhagen, Denmark, 2012
    Tilgjengelig fra: 2012-10-10 Laget: 2012-10-10 Sist oppdatert: 2018-05-30
  • 69.
    Bülow, Fredrik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Apelfröjd, Senad
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Bernhoff, Hans
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Stator cooling by axial flow through air-gap of high torque PM generator.Manuskript (preprint) (Annet vitenskapelig)
  • 70.
    Bülow, Fredrik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Kjellin, Jon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Bernhoff, Hans
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Torque ripple of a straight-bladed Darrieus turbine with PM generator estimated from diode rectifier output current.Manuskript (preprint) (Annet vitenskapelig)
  • 71. Candanedo, José
    et al.
    Salom, Jaume
    Widén, Joakim
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Athienitis, Andreas
    Load matching, grid interaction, and advanced control2015Inngår i: Modeling, Design, and Optimization of Net-Zero Energy Buildings / [ed] Athienitis, Andreas; O'Brien, William, John Wiley & Sons, 2015Kapittel i bok, del av antologi (Fagfellevurdert)
  • 72.
    Catarina, Sparre
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Scenarier för framtida effektbalans i elområde tre2019Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
  • 73.
    Cederholm, Simon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Verification of the program PowerGrid and establishment of reference grid for calculations2015Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Fortum Distribution AB uses a program called PowerGrid (PG) in its daily work. PG is a combined Network information system and grid calculation program. The development of this program is an ongoing process, so Fortum desired a reference program be set up as a means of controlling the continued accuracy of PG’s calculation results. Fortum is aware that PG has had difficulties in calculating some grid designs. An important goal, therefore, is to verify if these problems still exist so that Fortum if so can put increased pressure on their program developer to resolve them.

    This thesis includes work on 9 different grid set-ups that were known or thought to cause problems in PG. They are drawn up and calculated in PG and then modeled in Matlab where e.g. power flow and short-circuit calculations are carried out. Results are compared, the goal being to discover problems and deviations in PG and to understand more about how PG works.

    In short, a number of problems are discovered with PG’s calculations, and most grid set-ups that were suspected to be problematic are confirmed to be so. The largest problems occur when alternatives to the single 2-winded main-transformer set-up are tested. Otherwise, it is in the transitions between voltage levels that most of the problems arise. A related observation is that having more than one medium-voltage level or more than one low-voltage level is difficult for PG to handle.

    Finally, an Excel macro is introduced – a macro that can be used to compare results from different PG calculation engines and highlight any found differences. In short, it can be used as a quick-check before more thorough investigations are launched.

  • 74.
    Chen, Yingchao
    et al.
    China Univ Petr, Sch Business Adm, Beijing, Peoples R China..
    Feng, Lianyong
    China Univ Petr, Sch Business Adm, Beijing, Peoples R China..
    Wang, Jianliang
    China Univ Petr, Sch Business Adm, Beijing, Peoples R China..
    Höök, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Naturresurser och hållbar utveckling.
    Emergy-based energy return on investment method for evaluating energy exploitation2017Inngår i: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 128, s. 540-549Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To consider the environmental impacts of energy resource exploitation and better estimate the energy return of investment (EROI), this paper establishes a new emergy-based method (EmEROI) that can capture the essence of energy resource exploitation. The EmEROI method treats environmental impacts and labor as particular forms of energy, and all forms of energy can be quantified by solar transformity, which is expressed in emjoules as a common unit. The Daqing oilfield is used as an example, and the corresponding EmEROI value is calculated via the proposed method. The results are then compared with standard EROI estimates. Our EmEROI result is much lower than the standard EROI result and presents a more pronounced declining trend. Our results also indicated that the EmEROI estimates conform well to actual conditions and are not as affected by industrial energy intensity levels as the standard EROI. Thus, EmEROI has the potential for use as an integral aspect of energy resource exploitation project evaluations. (C) 2017 Elsevier Ltd. All rights reserved.

  • 75. Choudhary, Ar. S.
    et al.
    Pipralia, Dr. S.
    Kumar, Dr. N.
    Energy efficiency assessment of Indo-Saracenic buildings in India2018Inngår i: Conference Report: The 3rd International Conference on Energy Efficiency in Historic Buildings / [ed] Tor Broström, Lisa Nilsen and Susanna Carlsten, Uppsala University, 2018, s. 199-206Konferansepaper (Fagfellevurdert)
  • 76.
    Constanda, Daniel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Control Rod Effect at Partial SCRAM: Upgrade of Plant Model for Forsmark 2 in BISON After Power Uprate2015Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    This study aims to improve the modeling of partial SCRAM in the BISON plant model for the Forsmark 2 nuclear reactor after power uprate. Validation of the BISON model against tests performed from March to May in 2013 have shown that this is one of the areas in which there is room for improvement. After partial SCRAM is performed, the model underestimates the reactor power, recirculation flow and steam flow when compared to the measurement data.

    In BISON the partial SCRAM is modeled using a relative control rod effect vector (ASC vector). The aim is to replace the old values in this vector to improve the model. The new model was shown to give an improved result for the reactor power, recirculation flow and steam flow. The study gives recommendations on how to apply the new model and what values of the relative control rod effect vector that can be used in the future.

  • 77.
    Dahl, Emma
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för samhällsbyggnad och industriell teknik, Byggteknik och byggd miljö.
    Wallerström, Carolina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för samhällsbyggnad och industriell teknik, Byggteknik och byggd miljö.
    Hur placering av solceller kan bidra till att möta en byggnads effektbehov2020Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    The solar power accounts for only 0.2% of the Swedish power production in 2019. However, the solar power market is growing at a fast rate. Solar power production needs to be utilized instantly locally, for example in a building or else it is fed to the grid. Therefore, a challenge is how to utilize as much solar power as possible. This study aims to answer how solar panels should be placed in an optimal way in order to meet the load in a building similar to Vasakronan's property Kransen 2 in Uppsala. Two types of measures are used in the study to evaluate the solar power systems. The measure self-consumption describes the amount of solar production that is instantly used in a building. The measure self-sufficiency describes how much of the consumed solar power that covers the building's total load. The solar power production varies during the day. Therefore, the placement of panels affects the production profile during the day. The methodology in this study consists of a simulation model which provides optimal solar power systems regards to self-consumption and self-sufficiency. An economic model is also developed which calculates the payback time of solar power investments. The results shows that self-sufficiency is an important measure in order to increase the matching between a building's load and solar power production, and thereby reduce the proportion of purchased electricity from the grid. A solar power system should be optimized with regards to high self-sufficiency, and use the self-consumption to measure the amount of overproduction a system would have. A high self-sufficiency also provides a shorter payback time due to less amount of purchased electricity. The value and the relationship between self-consumption and self-sufficiency depends on the size of the system installed power. 

  • 78.
    Dahlborg, Elin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Frequency control: Pay for performance2015Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    The frequency control in the Nordic grid is to a large extent delivered by hydropower plants. The hydropower plants deliver frequency control of varying quality, meaning that a remuneration method based on more than just the static gain of the power plant is called for. This thesis has examined how three remuneration methods based on the hydropower plant output and the grid frequency deviation affects the grid stability.

    Using frequency data, the remunerated work along with the bandwidth and phase-crossover frequency was plotted and compared for varying governor settings.

    The results show that all three remuneration methods examined need constructive technical specifications (for example based on the frequency response) to not decrease the grid stability. The first remuneration method, where the power plant is remunerated for being on the right side of the power set point value as the grid frequency deviates, gave incentives for increased bandwidth, but no particular incentives regarding the phase-crossover frequency. The second remuneration method, where the power plant is remunerated for how well it matches the output power from a plant with no dynamics using a proportional controller, gave incentives for moderately high bandwidth and phase-crossover frequency. The third remuneration method, which remunerates how well the plant power output matches the load disturbance that gave rise to the grid frequency deviation, needs to be investigated further, but the initial analysis show that it did neither give incentives for increased bandwidth nor phase-crossover frequency.

  • 79.
    Dahmén, Viktor
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Holgersson, Martin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Larsson, Aron
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Norman, Joel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    How bright does the sun shine over Storvreta IK?: Mapping the energy use of a local Swedish sports club2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    In 2011 Storvreta IK installed two solar collector systems in order to reduce the club’s electricity demand for domestic hot water. However, electricity use from 2012 to 2015 shows that the expected reduction in the electricity demand has not occurred. This project investigates the solar collector systems and the heat demand of Storvreta IK’s buildings in order to explain the “failure” in electricity savings. The results of the simulations show that the heat production of the solar collectors is lower than Storvreta IK’s expectations. This could be explained by that the domestic hot water is not used as much as Storvreta IK thought and the system is therefore over-dimensioned for their need. The rebound effect could be another reason to why the electricity saving is lower than expected.

  • 80.
    Dalborg, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    MCNP-modell för beräkning av neutrondos och DPA på reaktortanken vid Ringhals 22013Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this report an MCNP (Monte Carlo N-Particle) model is described for the reactor vessel at Ringhals 2. The model is validated against the specific activity in neutron dosimeters, extracted in 1977, 1984 and 1994. The validation showed that the calculations of the model are within the requirements of a maximum of 20 percent uncertainty for every neutron dosimeter except one, extracted after the first cycle. The uncertainty of this cycle was mostly due to the operation data rather than to the MCNP model.

    The model has been used to investigate various questions concerning radiation damage. The reliability of the traditional measure of radiation damage, fast neutron flux (En > 1MeV) has been evaluated.  This has been done by taking the ratio for this and another measure of radiation damage, DPA (Displacement Per Atom), for various positions and layers. The results show good reliability, except for at the outer layers of the vessel wall, where the traditional measure underestimates the radiation damage.

    Inspections are carried out in connection with the change of fuel to investigate any possible cracking on the internal structures of the reactor vessel.  New data on local differences in the radiation of these have therefore been calculated for future evaluations.  This is in order to be able to focus the inspections mainly on those internal parts that are exposed to the highest dose of radiation. An estimation of the neutron dose after 40, 50 and 60 years of operation has been calculated for the surface of the reactor vessel that is being exposed to the highest neutron flux. The result confirms earlier appreciation that the radiation damage to the reactor vessel is not a limiting factor for the future operation of Ringhals 2. The report also presents which surface of the vessel wall that has been exposed to a neutron dose of 1017 n/cm2 for neutrons with En > 1 MeV.

  • 81.
    Davidsson, Simon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Naturresurser och hållbar utveckling.
    Global energy transitions: Renewable energy technology and non-renewable resources2015Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The global energy system is dominated by the use of fossil fuels. This system suffers from several problems, such as different environmental issues, while the long-term energy security is sometimes questioned. As an alternative to this situation, a transition to a global energy system based on renewable energy technologies, to a large extent solar and wind energy, is commonly proposed. Constructing the technology needed for such a transition requires resources and how fast this could happen is somewhat disputed. This thesis explores methods to assess the potential constraints for realizing such a transition by looking at potential technology growth rates and outlooks of production of the required natural resources.

    The thesis is based on three papers presenting case studies that look at growth rates of wind energy as well as future production outlooks of lithium and phosphate rock. Using different types of growth patterns reaching proposed installed capacities of wind power, annual commissioning requirements are investigated, taking account for the limited life expectancy oftechnology. Potential outlooks of mineral production are explored using resource constrained curve-fitting models on global lithium production. A more disaggregated model looking at individual countries are used on phosphate rock production to investigate new perspectives on production outlooks.

    It is concluded that the growth rates of individual energy technologies affect the resource requirements and prospective constraints on energy transitions. Resource constrained modelling of resource production can provide spans of potential outlooks for future production of resources required for anenergy transition. A higher disaggregation of the modelling can provide new perspectives of potential constraints on future production. These aspects should be further investigated when proposing alternative future energy systems.

    Delarbeid
    1. Growth curves and sustained commissioning modelling of renewable energy: Investigating resource constraints for wind energy
    Åpne denne publikasjonen i ny fane eller vindu >>Growth curves and sustained commissioning modelling of renewable energy: Investigating resource constraints for wind energy
    2014 (engelsk)Inngår i: Energy Policy, ISSN 0301-4215, E-ISSN 1873-6777, Vol. 73, s. 767-776Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Abstract Several recent studies have proposed fast transitions to energy systems based on renewable energy technology. Many of them dismiss potential physical constraints and issues with natural resource supply, and do not consider the growth rates of the individual technologies needed or how the energy systems are to be sustained over longer time frames. A case study is presented modelling potential growth rates of the wind energy required to reach installed capacities proposed in other studies, taking into account the expected service life of wind turbines. A sustained commissioning model is proposed as a theoretical foundation for analysing reasonable growth patterns for technologies that can be sustained in the future. The annual installation and related resource requirements to reach proposed wind capacity are quantified and it is concluded that these factors should be considered when assessing the feasibility, and even the sustainability, of fast energy transitions. Even a sustained commissioning scenario would require significant resource flows, for the transition as well as for sustaining the system, indefinitely. Recent studies that claim there are no potential natural resource barriers or other physical constraints to fast transitions to renewable energy appear inadequate in ruling out these concerns.

    Emneord
    Growth curves, Natural resources, Renewable energy, Wind energy, Sustainability, Energy systems
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot globala energiresurser
    Identifikatorer
    urn:nbn:se:uu:diva-225554 (URN)10.1016/j.enpol.2014.05.003 (DOI)000341474100072 ()
    Forskningsfinansiär
    StandUp
    Tilgjengelig fra: 2014-06-04 Laget: 2014-06-04 Sist oppdatert: 2017-12-05bibliografisk kontrollert
    2. Lithium availability and future production outlooks
    Åpne denne publikasjonen i ny fane eller vindu >>Lithium availability and future production outlooks
    2013 (engelsk)Inngår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 110, nr 10, s. 252-266Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Lithium is a highly interesting metal, in part due to the increasing interest in lithium-ion batteries. Several recent studies have used different methods to estimate whether the lithium production can meet an increasing demand, especially from the transport sector, where lithium-ion batteries are the most likely technology for electric cars. The reserve and resource estimates of lithium vary greatly between different studies and the question whether the annual production rates of lithium can meet a growing demand is seldom adequately explained. This study presents a review and compilation of recent estimates of quantities of lithium available for exploitation and discusses the uncertainty and differences between these estimates. Also, mathematical curve fitting models are used to estimate possible future annual production rates. This estimation of possible production rates are compared to a potential increased demand of lithium if the International Energy Agency’s Blue Map Scenarios are fulfilled regarding electrification of the car fleet. We find that the availability of lithium could in fact be a problem for fulfilling this scenario if lithium-ion batteries are to be used. This indicates that other battery technologies might have to be implemented for enabling an electrification of road transports.

    Emneord
    Peak lithium, Electric vehicles, Lithium production, Lithium supply, Resource-constrained modelling, Lithium battery cars
    HSV kategori
    Forskningsprogram
    Fysik med inriktning mot globala energiresurser
    Identifikatorer
    urn:nbn:se:uu:diva-199784 (URN)10.1016/j.apenergy.2013.04.005 (DOI)000321601900024 ()
    Prosjekter
    Stand
    Tilgjengelig fra: 2013-05-14 Laget: 2013-05-14 Sist oppdatert: 2017-12-06bibliografisk kontrollert
    3. Phosphate rock production and depletion: Regional disaggregated modeling and global implications
    Åpne denne publikasjonen i ny fane eller vindu >>Phosphate rock production and depletion: Regional disaggregated modeling and global implications
    2014 (engelsk)Inngår i: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 93, s. 178-187Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Abstract Numerous recent studies discuss phosphate rock extraction, and some even propose that a peak in production could be reached in coming decades. This would have great consequences as phosphate rock based fertilizers are irreplaceable in modern agriculture. Studies suggesting an impending peak commonly use curve fitting models where mathematical functions are fitted to historical world production data, while studies using other methods reach completely different results. Also, a sudden increase in global reserve estimates is commonly used to dismiss these warnings, and has somewhat altered the debate. The recent multiplication of estimated reserves is mostly based on an increase of the Moroccan reserve estimate, leading to Morocco currently making up most of the global reserves. This study models global phosphate rock production using a disaggregated curve fitting model based on the production in individual major producing countries, providing a somewhat different view than most studies, and show that the global trade of phosphate rock could be completely dependent on Morocco in the future. There are several different factors that can potentially limit global production and these factors should be considered for the individual producing countries. Society’s total dependence on phosphate rock should be further investigated despite claims of large resource occurrences.

    Emneord
    Phosphorus, Phosphate rock, Peak minerals, Resource depletion, Fertilizer, Curve fitting modeling
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-238213 (URN)10.1016/j.resconrec.2014.10.011 (DOI)000347594000017 ()
    Forskningsfinansiär
    StandUp
    Tilgjengelig fra: 2014-12-10 Laget: 2014-12-10 Sist oppdatert: 2017-12-05bibliografisk kontrollert
  • 82.
    Davidsson, Simon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Naturresurser och hållbar utveckling.
    Natural resources and sustainable energy: Growth rates and resource flows for low-carbon systems2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Large-scale deployment of low-carbon energy technologies is important for counteracting anthropogenic climate change and achieving universal energy access. This thesis explores potential growth rates of technologies necessary to reach a more sustainable global energy system, the material and energy flows required to commission these technologies, and potential future availability of the required resources.

    These issues are investigated in five papers. Potential future growth rates of wind energy and solar photovoltaics, and the associated material requirements are explored, taking the expected service life of these technologies into account. Methodology for assessing net energy return and natural resource use for wind energy systems are analyzed. Potential future availability of lithium and phosphate rock are also investigated.

    Estimates of energy and materials required for technologies such as wind energy and photovoltaics vary, and depend on the assumptions made and methods used. Still, it is clear that commissioning of low-carbon technologies on the scale required to reach and sustain a low-carbon energy system in coming decades requires significant quantities of both bulk materials and scarcer resources. For some technologies, such as thin film solar cells and electric vehicles with lithium-ion batteries, availability of materials could become an issue for potential growth rates. Future phosphate rock production could become highly dependent on few countries, and potential political, social and environmental aspects of this should be investigated in more detail.

    Material and energy flows should be considered when analyzing growth rates of low-carbon technologies. Their estimated service life can indicate sustainable growth rates of technologies, as well as when materials are available for end-of-life recycling. Resource constrained growth curve models can be used to explore future production of natural resources. A higher disaggregation of these models can enable more detailed analysis of potential constraints. This thesis contributes to the discussion on how to create a more sustainable global energy system, but the methods to assess current and future energy and material flows, and availability of natural resources, should be further developed in the future.

    Delarbeid
    1. Growth curves and sustained commissioning modelling of renewable energy: Investigating resource constraints for wind energy
    Åpne denne publikasjonen i ny fane eller vindu >>Growth curves and sustained commissioning modelling of renewable energy: Investigating resource constraints for wind energy
    2014 (engelsk)Inngår i: Energy Policy, ISSN 0301-4215, E-ISSN 1873-6777, Vol. 73, s. 767-776Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Abstract Several recent studies have proposed fast transitions to energy systems based on renewable energy technology. Many of them dismiss potential physical constraints and issues with natural resource supply, and do not consider the growth rates of the individual technologies needed or how the energy systems are to be sustained over longer time frames. A case study is presented modelling potential growth rates of the wind energy required to reach installed capacities proposed in other studies, taking into account the expected service life of wind turbines. A sustained commissioning model is proposed as a theoretical foundation for analysing reasonable growth patterns for technologies that can be sustained in the future. The annual installation and related resource requirements to reach proposed wind capacity are quantified and it is concluded that these factors should be considered when assessing the feasibility, and even the sustainability, of fast energy transitions. Even a sustained commissioning scenario would require significant resource flows, for the transition as well as for sustaining the system, indefinitely. Recent studies that claim there are no potential natural resource barriers or other physical constraints to fast transitions to renewable energy appear inadequate in ruling out these concerns.

    Emneord
    Growth curves, Natural resources, Renewable energy, Wind energy, Sustainability, Energy systems
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot globala energiresurser
    Identifikatorer
    urn:nbn:se:uu:diva-225554 (URN)10.1016/j.enpol.2014.05.003 (DOI)000341474100072 ()
    Forskningsfinansiär
    StandUp
    Tilgjengelig fra: 2014-06-04 Laget: 2014-06-04 Sist oppdatert: 2017-12-05bibliografisk kontrollert
    2. Material requirements and availability for multi-terawatt deployment of photovoltaics
    Åpne denne publikasjonen i ny fane eller vindu >>Material requirements and availability for multi-terawatt deployment of photovoltaics
    (engelsk)Artikkel i tidsskrift (Annet vitenskapelig) Submitted
    Emneord
    solar energy, photovoltaics, critical materials, energy metals, renewable energy, recycling
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-301946 (URN)
    Eksternt samarbeid:
    Forskningsfinansiär
    StandUp
    Tilgjengelig fra: 2016-08-26 Laget: 2016-08-26 Sist oppdatert: 2018-05-08
    3. A review of life cycle assessments on wind energy systems
    Åpne denne publikasjonen i ny fane eller vindu >>A review of life cycle assessments on wind energy systems
    2012 (engelsk)Inngår i: The International Journal of Life Cycle Assessment, ISSN 0948-3349, E-ISSN 1614-7502, Vol. 17, nr 6, s. 729-742Artikkel, forskningsoversikt (Fagfellevurdert) Published
    Abstract [en]

    Purpose

    Several life cycle assessments (LCA) of wind energy published in recent years are reviewed to identify methodological differences and underlying assumptions.

    Methods

    A full comparative analysis of 12 studies were undertaken (10 peer-reviewed papers, 1 conference paper, 1 industry report) regarding six fundamental factors (methods used, energy use accounting, quantification of energy production, energy performance and primary energy,  natural resources, and recycling). Each factor is discussed in detail to highlight strengths and shortcomings of various approaches.

    Results

    Several potential issues are found concerning the way LCA methods are used for assessing energy performance and environmental impact of wind energy, as well as dealing with natural resource use and depletion. The potential to evaluate natural resource use and depletion impacts from wind energy appears to be poorly exploited or elaborated on in the reviewed studies. Estimations of energy performance and environmental impacts are critically analyzed and found to differ significantly.

    Conclusions and recommendations

    A continued discussion and development of LCA methodology for wind energy and other energy resources are encouraged. Efforts should be made to standardize methods and calculations. Inconsistent use of terminology and concepts among the analyzed studies are found and should be remedied. Different methods are generally used and the results are presented in diverse ways, making it hard to compare studies with each other, but also with other renewable energy sources.

    Emneord
    life cycle assessment, wind energy, wind power, natural resource use, primary energy conversion, energy accounting
    HSV kategori
    Forskningsprogram
    Fysik med inriktning mot globala energiresurser
    Identifikatorer
    urn:nbn:se:uu:diva-168922 (URN)10.1007/s11367-012-0397-8 (DOI)000304879800008 ()
    Prosjekter
    StandUp for Energy
    Tilgjengelig fra: 2012-02-20 Laget: 2012-02-19 Sist oppdatert: 2017-12-07bibliografisk kontrollert
    4. Lithium availability and future production outlooks
    Åpne denne publikasjonen i ny fane eller vindu >>Lithium availability and future production outlooks
    2013 (engelsk)Inngår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 110, nr 10, s. 252-266Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Lithium is a highly interesting metal, in part due to the increasing interest in lithium-ion batteries. Several recent studies have used different methods to estimate whether the lithium production can meet an increasing demand, especially from the transport sector, where lithium-ion batteries are the most likely technology for electric cars. The reserve and resource estimates of lithium vary greatly between different studies and the question whether the annual production rates of lithium can meet a growing demand is seldom adequately explained. This study presents a review and compilation of recent estimates of quantities of lithium available for exploitation and discusses the uncertainty and differences between these estimates. Also, mathematical curve fitting models are used to estimate possible future annual production rates. This estimation of possible production rates are compared to a potential increased demand of lithium if the International Energy Agency’s Blue Map Scenarios are fulfilled regarding electrification of the car fleet. We find that the availability of lithium could in fact be a problem for fulfilling this scenario if lithium-ion batteries are to be used. This indicates that other battery technologies might have to be implemented for enabling an electrification of road transports.

    Emneord
    Peak lithium, Electric vehicles, Lithium production, Lithium supply, Resource-constrained modelling, Lithium battery cars
    HSV kategori
    Forskningsprogram
    Fysik med inriktning mot globala energiresurser
    Identifikatorer
    urn:nbn:se:uu:diva-199784 (URN)10.1016/j.apenergy.2013.04.005 (DOI)000321601900024 ()
    Prosjekter
    Stand
    Tilgjengelig fra: 2013-05-14 Laget: 2013-05-14 Sist oppdatert: 2017-12-06bibliografisk kontrollert
    5. Phosphate rock production and depletion: Regional disaggregated modeling and global implications
    Åpne denne publikasjonen i ny fane eller vindu >>Phosphate rock production and depletion: Regional disaggregated modeling and global implications
    2014 (engelsk)Inngår i: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 93, s. 178-187Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Abstract Numerous recent studies discuss phosphate rock extraction, and some even propose that a peak in production could be reached in coming decades. This would have great consequences as phosphate rock based fertilizers are irreplaceable in modern agriculture. Studies suggesting an impending peak commonly use curve fitting models where mathematical functions are fitted to historical world production data, while studies using other methods reach completely different results. Also, a sudden increase in global reserve estimates is commonly used to dismiss these warnings, and has somewhat altered the debate. The recent multiplication of estimated reserves is mostly based on an increase of the Moroccan reserve estimate, leading to Morocco currently making up most of the global reserves. This study models global phosphate rock production using a disaggregated curve fitting model based on the production in individual major producing countries, providing a somewhat different view than most studies, and show that the global trade of phosphate rock could be completely dependent on Morocco in the future. There are several different factors that can potentially limit global production and these factors should be considered for the individual producing countries. Society’s total dependence on phosphate rock should be further investigated despite claims of large resource occurrences.

    Emneord
    Phosphorus, Phosphate rock, Peak minerals, Resource depletion, Fertilizer, Curve fitting modeling
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-238213 (URN)10.1016/j.resconrec.2014.10.011 (DOI)000347594000017 ()
    Forskningsfinansiär
    StandUp
    Tilgjengelig fra: 2014-12-10 Laget: 2014-12-10 Sist oppdatert: 2017-12-05bibliografisk kontrollert
  • 83.
    Davidsson, Simon
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Naturresurser och hållbar utveckling.
    Grandell, Leena
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Naturresurser och hållbar utveckling.
    Wachtmeister, Henrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Naturresurser och hållbar utveckling.
    Höök, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Naturresurser och hållbar utveckling.
    Growth curves and sustained commissioning modelling of renewable energy: Investigating resource constraints for wind energy2014Inngår i: Energy Policy, ISSN 0301-4215, E-ISSN 1873-6777, Vol. 73, s. 767-776Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract Several recent studies have proposed fast transitions to energy systems based on renewable energy technology. Many of them dismiss potential physical constraints and issues with natural resource supply, and do not consider the growth rates of the individual technologies needed or how the energy systems are to be sustained over longer time frames. A case study is presented modelling potential growth rates of the wind energy required to reach installed capacities proposed in other studies, taking into account the expected service life of wind turbines. A sustained commissioning model is proposed as a theoretical foundation for analysing reasonable growth patterns for technologies that can be sustained in the future. The annual installation and related resource requirements to reach proposed wind capacity are quantified and it is concluded that these factors should be considered when assessing the feasibility, and even the sustainability, of fast energy transitions. Even a sustained commissioning scenario would require significant resource flows, for the transition as well as for sustaining the system, indefinitely. Recent studies that claim there are no potential natural resource barriers or other physical constraints to fast transitions to renewable energy appear inadequate in ruling out these concerns.

  • 84.
    Davidsson, Simon
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Naturresurser och hållbar utveckling.
    Höök, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Naturresurser och hållbar utveckling.
    Material requirements and availability for multi-terawatt deployment of photovoltaicsArtikkel i tidsskrift (Annet vitenskapelig)
  • 85.
    Davidsson, Simon
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Globala energisystem.
    Höök, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Globala energisystem.
    Wall, Göran
    Gotland University, Department of Culture, Energy and Environment.
    A review of life cycle assessments on wind energy systems2012Inngår i: The International Journal of Life Cycle Assessment, ISSN 0948-3349, E-ISSN 1614-7502, Vol. 17, nr 6, s. 729-742Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Purpose

    Several life cycle assessments (LCA) of wind energy published in recent years are reviewed to identify methodological differences and underlying assumptions.

    Methods

    A full comparative analysis of 12 studies were undertaken (10 peer-reviewed papers, 1 conference paper, 1 industry report) regarding six fundamental factors (methods used, energy use accounting, quantification of energy production, energy performance and primary energy,  natural resources, and recycling). Each factor is discussed in detail to highlight strengths and shortcomings of various approaches.

    Results

    Several potential issues are found concerning the way LCA methods are used for assessing energy performance and environmental impact of wind energy, as well as dealing with natural resource use and depletion. The potential to evaluate natural resource use and depletion impacts from wind energy appears to be poorly exploited or elaborated on in the reviewed studies. Estimations of energy performance and environmental impacts are critically analyzed and found to differ significantly.

    Conclusions and recommendations

    A continued discussion and development of LCA methodology for wind energy and other energy resources are encouraged. Efforts should be made to standardize methods and calculations. Inconsistent use of terminology and concepts among the analyzed studies are found and should be remedied. Different methods are generally used and the results are presented in diverse ways, making it hard to compare studies with each other, but also with other renewable energy sources.

  • 86. de Place Hansen, E.J.
    et al.
    Møller, E.B.
    How to estimate material properties for external walls in historic buildings before applying internal insulation2018Inngår i: Conference Report: The 3rd International Conference on Energy Efficiency in Historic Buildings / [ed] Tor Broström, Lisa Nilsen and Susanna Carlsten, Uppsala University, 2018, s. 41-49Konferansepaper (Fagfellevurdert)
  • 87. de Place Hansen, E.J.
    et al.
    Wittchen, K.B.
    Energy savings due to internal façade insulation in historic buildings2018Inngår i: Conference Report: The 3rd International Conference on Energy Efficiency in Historic Buildings / [ed] Tor Broström, Lisa Nilsen and Susanna Carlsten, Uppsala University, 2018, s. 22-31Konferansepaper (Fagfellevurdert)
  • 88. Del Curto, D.
    et al.
    Joppolo, C.M.
    Luciani, A.
    Valisi, L.P.
    Energy efficiency and preservation of 20th century architecture: The case of the Urbino University Colleges2018Inngår i: Conference Report: The 3rd International Conference on Energy Efficiency in Historic Buildings / [ed] Tor Broström, Lisa Nilsen and Susanna Carlsten, Uppsala University, 2018, s. 401-412Konferansepaper (Fagfellevurdert)
  • 89. Delhaye, P.
    The approach of the Walloon Heritage Agencyon the energy upgrade of listed buildings2018Inngår i: Conference Report: The 3rd International Conference on Energy Efficiency in Historic Buildings / [ed] Tor Broström, Lisa Nilsen and Susanna Carlsten, Uppsala University, 2018, s. 207-215Konferansepaper (Fagfellevurdert)
  • 90. Demetriou, Demetris
    et al.
    Polatidis, Heracles
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Haralambopoulos, Dias
    Integrated Energy Planning for the Residential Sector: The case-study of Cyprus’, Energy Sources2014Inngår i: Energy sources, ISSN 0090-8312, E-ISSN 1521-0510Artikkel i tidsskrift (Fagfellevurdert)
  • 91.
    Djärv, Oskar
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Åtgärdsplan för energieffektiviseringav ett flerbostadshus från 1940-talet: En fallstudie av Vindelgatan 15 i Ludvika2015Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    A housing association in Ludvika owns an apartment building built 1942 with a heating system based on district heating. The housing association is interested in reducing their annual energy cost, which corresponds to reducing their energy consumption. The yearly energy consumption for the building at the moment is about 40 % above the average for Swedish apartment buildings. This report investigates the possibilities of reducing the total energy consumption for the building, in a profitable way, and at the same time meeting the governmental targets for 2050 and the maximum specific energy demand for new buildings presented by the building regulation.

    The method used in this report was to conduct simulations of models of the building where proposals in terms of reducing the use of heat were evaluated. The proposals were related to the ventilation system, the building envelope, and solar power installations.

    The simulations returned results of many proposals that could reduce the energy consumption, but just a few turned out to be financially viable. Installing an exhaust air heat pump in combination with solar panels for heat supply and solar cells for electricity was found to be the most viable solution.

    A combination of these three proposals was calculated to reduce the yearly heat consumption with 188 MWh and the total energy consumption by 50 %, which meets the 2050 target. The specific energy consumption of the building per square meter of heated area is 97 kWh, which means that the maximum specific energy demand of 110 kWh is met. 

  • 92.
    Donzel-Gargand, Olivier
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    The Multiple Faces of Interfaces: Electron microscopy analysis of CuInSe2 thin-film solar cells2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The CIS solar cell family features both a high stability and world-class performances. They can be deposited on a wide variety of substrates and absorb the entire solar spectrum only using a thickness of a few micrometers. These particularities allow them to feature the most positive Energy returned on energy invested (EROI) values and the shortest Energy payback times (EPBT) of all the main photovoltaic solar cells. Using mainly electron microscopy characterization techniques, this thesis has explored the questions related to the interface control in thin-film photovoltaic solar cells based on CuInSe2 (CIS) absorber materials. Indeed, a better understanding of the interfaces is essential to further improve the solar cell conversion efficiency (currently around 23%), but also to introduce alternative substrates, to implement various alloying (Ga-CIS (CIGS), Ag-CIGS (ACIGS)…) or even to assess alternative buffer layers.

    The thread of this work is the understanding and the improvement of the interface control. To do so, the passivation potential of Al2O3 interlayers has been studied in one part of the thesis. While positive changes were generally measured, a subsequent analysis has revealed that a detrimental interaction could occur between the NaF precursor layer and the rear Al2O3 passivation layer. Still within the passivation research field, incorporation of various alkali-metals to the CIS absorber layer has been developed and analyzed. Large beneficial effects were ordinarily reported. However, similar KF-post deposition treatments were shown to be potentially detrimental for the silver-alloyed CIGS absorber layer. Finally, part of this work dealt with the limitations of the thin-barrier layers usually employed when using steel substrates instead of soda-lime glass ones. The defects and their origin could have been related to the steel manufacturing process, which offered solutions to erase them.

    Electron microscopy, especially Transmission electron microscopy (TEM), was essential to scrutinize the local changes occurring at the different interfaces within a few nanometers. The composition variation was measured with both Electron energy loss spectroscopy (EELS) and Energy dispersive X-ray spectroscopy (EDS) techniques. Finally, efforts have been invested in controlling and improving the FIB sample preparation, which was required for the TEM observations in our case.

    Delarbeid
    1. On the assessment of CIGS surface passivation by photoluminescence
    Åpne denne publikasjonen i ny fane eller vindu >>On the assessment of CIGS surface passivation by photoluminescence
    Vise andre…
    2015 (engelsk)Inngår i: Physica Status Solidi. Rapid Research Letters, ISSN 1862-6254, E-ISSN 1862-6270, Vol. 9, nr 5, s. 288-292Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    An optimized test structure to study rear surface passivation in Cu(In,Ga)Se-2 (CIGS) solar cells by means of photoluminescence (PL) is developed and tested. The structure - illustrated in the abstract figure - is examined from the rear side. To enable such rear PL assessment, a semi-transparent ultrathin Mo layer has been developed and integrated in place of the normal rear contact. The main advantages of this approach are (i) a simplified representation of a rear surface passivated CIGS solar cell is possible, (ii) it is possible to assess PL responses originating close to the probed rear surface, and (iii) a stable PL response as a function of air exposure time is obtained. In this work, PL measurements of such structures with and without rear surface passivation layers have been compared, and the measured improvement in PL intensity for the passivated structures is associated with enhanced CIGS rear interface properties. [GRAPHICS] Transmission electron microscope (TEM) bright field cross-section image of the rear illuminated test structure fabricated for PL characterization.

    Emneord
    solar cells, thin films, CuInGaSe2, surface passivation, photoluminescence
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-256541 (URN)10.1002/pssr.201510081 (DOI)000354888300002 ()
    Tilgjengelig fra: 2015-06-25 Laget: 2015-06-24 Sist oppdatert: 2018-08-12bibliografisk kontrollert
    2. Surface defect passivation by a thin metallic barrier for Cu(InxGa1-x)Se2 co-evaporation on Cr-steel substrates
    Åpne denne publikasjonen i ny fane eller vindu >>Surface defect passivation by a thin metallic barrier for Cu(InxGa1-x)Se2 co-evaporation on Cr-steel substrates
    Vise andre…
    2016 (engelsk)Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 619, s. 220-226Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    The use of Cr-steel substrates for the fabrication of Cu(In,Ga)Se2 (CIGS) solar cells is highly desirable and is a topic of considerable research interest. However, solar cells on non-treated steel substrates often exhibit decreased performance compared to their homologues on soda lime glass substrates. This is partly attributed to out-diffusion of steel components (Fe, Cr, Mn, etc.) into the solar cell. To avoid this contamination, thin film barriers can be added on top of the steel surface, but they do not always prevent the diffusion completely. In this paper we study the potential of using Cr and Ti as thin barrier layers. We find that local surface defects on the steel, several micrometers in height, lead to cracks in the back contact as well as in the barrier layers. Advanced transmission electron microscopy (TEM) techniques reveal that elemental diffusion and chemical reactions occur at these openings during heat treatments in Se atmosphere. TEM-energy dispersive X-ray spectroscopy (TEM-EDX) analysis in combination with calculation of the solid state diffusion coefficient demonstrate that a Cr-barrier sacrificially protects the Cr-steel substrate, blocking most of the Fe out-diffusion, whereas a Ti-barrier is less efficient.

    sted, utgiver, år, opplag, sider
    Elsevier, 2016
    Emneord
    Back contact; Thin film; Solar cell; Steel substrate; CuInGaSe2; Electron microscopy; Diffusion; Barrier
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot materialanalys; Teknisk fysik med inriktning mot materialvetenskap
    Identifikatorer
    urn:nbn:se:uu:diva-307368 (URN)10.1016/j.tsf.2016.10.063 (DOI)000389610900033 ()
    Tilgjengelig fra: 2016-11-14 Laget: 2016-11-14 Sist oppdatert: 2018-08-12bibliografisk kontrollert
    3. Rear Surface Optimization of CZTS Solar Cells by Use of a Passivation Layer With Nanosized Point Openings
    Åpne denne publikasjonen i ny fane eller vindu >>Rear Surface Optimization of CZTS Solar Cells by Use of a Passivation Layer With Nanosized Point Openings
    Vise andre…
    2016 (engelsk)Inngår i: IEEE Journal of Photovoltaics, ISSN 2156-3381, E-ISSN 2156-3403, Vol. 6, nr 1, s. 332-336Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Previously, an innovative way to reduce rear interface recombination in Cu(In, Ga)(S, Se)(2) (CIGSSe) solar cells has been successfully developed. In this work, this concept is established in Cu-2(Zn, Sn)(S, Se)(4) (CZTSSe) cells to demonstrate its potential for other thin-film technologies. Therefore, ultrathin CZTS cells with an Al2O3 rear surface passivation layer having nanosized point openings are fabricated. The results indicate that introducing such a passivation layer can have a positive impact on open-circuit voltage (V-OC; +17% rel.), short-circuit current (J(SC); +5% rel.), and fill factor (FF; +9% rel.), compared with corresponding unpassivated cells. Hence, a promising efficiency improvement of 32% rel. is obtained for the rear passivated cells.

    Emneord
    Aluminum oxide, Cu(In, Ga)(S, Se)(2), Cu-2(Zn, Sn)(S, Se)(4), nanosized point contacts, solar cells, surface passivation layer, thin-film
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-274909 (URN)10.1109/JPHOTOV.2015.2496864 (DOI)000367251900048 ()
    Forskningsfinansiär
    Swedish Research CouncilSwedish Energy AgencyEU, FP7, Seventh Framework Programme, 300998EU, FP7, Seventh Framework Programme, 327367
    Tilgjengelig fra: 2016-01-27 Laget: 2016-01-26 Sist oppdatert: 2018-08-12bibliografisk kontrollert
    4. Deep surface Cu depletion induced by K in high-efficiency Cu(In,Ga)Se2 solar cell absorbers
    Åpne denne publikasjonen i ny fane eller vindu >>Deep surface Cu depletion induced by K in high-efficiency Cu(In,Ga)Se2 solar cell absorbers
    Vise andre…
    2018 (engelsk)Inngår i: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159X, Vol. 26, nr 9, s. 730-739Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    In this work, we used K‐rich glass substrates to provide potassium during the coevaporation of Cu(In,Ga)Se2 (CIGS) absorber layers. Subsequently, we applied a postdeposition treatment (PDT) using KF or RbF to some of the grown absorbers. It was found that the presence of K during the growth of the CIGS layer led to cell effi- ciencies beyond 17%, and the addition of a PDT pushed it beyond 18%. The major finding of this work is the observation of discontinuous 100‐ to 200‐nm‐deep Cu‐ depleted patches in the vicinity of the CdS buffer layer, correlated with the presence of K during the growth of the absorber layer. The PDT had no influence on the forma- tion of these patches. A second finding concerns the composition of the Cu‐depleted areas, where an anticorrelation between Cu and both In and K was measured using scanning transmission electron microscopy. Furthermore, a steeper Ga/(In+Ga) ratio gradient was measured for the absorbers grown with the presence of K, suggesting that K hinders the group III element interdiffusion. Finally, no Cd in‐diffusion to the CIGS layer could be detected. This indicates that if CdCu substitution occurs, either their concentration is below our instrumental detection limit or its presence is contained within the first 6 nm from the CdS/CIGS interface.

    Emneord
    CIGS, Cu depletion, EELS, OVC, Raman, solar cell, TEM
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-357120 (URN)10.1002/pip.3010 (DOI)000442501000004 ()
    Forskningsfinansiär
    Swedish Research CouncilSwedish Energy AgencyEU, Horizon 2020, 720887
    Tilgjengelig fra: 2018-08-12 Laget: 2018-08-12 Sist oppdatert: 2018-11-13bibliografisk kontrollert
    5. Surface Modification And Secondary Phase Formation From a High Dose KF-Post Deposition Treatment of (Ag,Cu)(In,Ga)Se2 Solar Cell Absorbers
    Åpne denne publikasjonen i ny fane eller vindu >>Surface Modification And Secondary Phase Formation From a High Dose KF-Post Deposition Treatment of (Ag,Cu)(In,Ga)Se2 Solar Cell Absorbers
    Vise andre…
    (engelsk)Inngår i: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159XArtikkel i tidsskrift (Fagfellevurdert) Submitted
    Abstract [en]

    In this study we assessed the potential of KF-Post Deposition Treatment (PDT) performed on a silver-alloyed Cu(Inx,Ga1-x)Se2 (ACIGS) solar absorber. ACIGS absorbers with Ag/Ag+Cu ratio (Ag/I) close to 20% were co-evaporated on a Mo-coated glass substrate and exposed to in-situ KF-PDT of various intensities. The current-voltage characteristics indicated that an optimized PDT can be beneficial, increasing in our study the median Voc and efficiency values by +48 mV and +0.9 %abs (from 728 mV and 16.1 % efficiency measured for the sample without PDT), respectively. However, an increased KF-flux during PDT resulted in a net deterioration of the performance leading to median Voc and efficiency values as low as 503 mV and 4.7 %. The chemical composition analysis showed that while the reference absorber without any PDT was homogeneous, the KF-PDT induced a clear change within the first 10 nm from the surface. Here, the surface layer composition was richer in K and In with an increased Ag/I ratio, and its thickness seemed to follow the KF exposure intensity. Additionally, high-dose KF-PDT resulted in substantial formation of secondary phases for the ACIGS. The secondary phase precipitates were also richer in Ag, K and In, and Electron and X-ray diffraction data match with the monoclinic C 1 2/c 1 space group adopted by the Ag-alloyed KInSe2 (AKIS) phase. It could not be concluded whether the performance loss for the solar cell devices originated from the thicker surface layer or the presence of secondary phases, or both for the high-dose KF-PDT sample.

    Emneord
    TEM, EDS, ACIGS, XPS, KF-PDT, KInSe
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-357122 (URN)
    Tilgjengelig fra: 2018-08-12 Laget: 2018-08-12 Sist oppdatert: 2018-08-13bibliografisk kontrollert
    6. Effect of different Na supply methods on thin Cu(In,Ga)Se2 solar cells with Al2O3 rear passivation layers
    Åpne denne publikasjonen i ny fane eller vindu >>Effect of different Na supply methods on thin Cu(In,Ga)Se2 solar cells with Al2O3 rear passivation layers
    Vise andre…
    2018 (engelsk)Inngår i: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 187, nr 1, s. 160-169Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    In this work, rear-contact passivated Cu(In,Ga)Se2 (CIGS) solar cells were fabricated without any intentional contact openings between the CIGS and Mo layers. The investigated samples were either Na free or one of two Na supply methods was used, i) a NaF precursor on top of the Al2O3 rear passivation layer or ii) an in situ post- deposition treatment with NaF after co-evaporation of the CIGS layer. The thickness of the ALD-Al2O3 passi- vation layer was also varied in order to find an optimal combination of Na supply and passivation layer thickness. Our results from electrical characterization show remarkably different solar cell behavior for different Na supplies. For up to 1nm thick Al2O3 layers an electronically good contact could be confirmed independently of Na deposition method and content. When the Al2O3 thickness exceeded 1 nm, the current was blocked on all samples except on the samples with the NaF precursor. On these samples the current was not blocked up to an Al2O3 layer thickness of about 6 nm, the maximum thickness we could achieve without the CIGS peeling off the Al2O3 layer. Transmission electron microscopy reveals a porous passivation layer for the samples with a NaF precursor. An analysis of the dependence of the open circuit voltage on temperature (JVT) indicates that a thicker NaF precursor layer lowers the height of the hole barrier at the rear contact for the passivated cells. This energy barrier is also lower for the passivated sample, compared to an unpassivated sample, when both samples have been post-deposition treated.

    Emneord
    Alkali, Back contact, CIGS, Passivation, Thin films, Rear contact, Tunneling
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-357123 (URN)10.1016/j.solmat.2018.07.017 (DOI)000445308300019 ()
    Forskningsfinansiär
    Swedish Research Council, 43523-1StandUpEU, Horizon 2020, 720887
    Tilgjengelig fra: 2018-08-12 Laget: 2018-08-12 Sist oppdatert: 2019-08-08bibliografisk kontrollert
  • 93.
    Donzel-Gargand, Olivier
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Larsson, Fredrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Törndahl, Tobias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Stolt, Lars
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik. Solibro Research AB, Vallvägen 5, Uppsala,Sweden.
    Edoff, Marika
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Secondary phase formation and surface modification from a high dose KF-post deposition treatment of (Ag,Cu)(In,Ga)Se-2 solar cell absorbers2019Inngår i: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159X, Vol. 27, nr 3, s. 220-228Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, we assessed the potential of KF-post deposition treatment (PDT) performed on a silver-alloyed Cu (In,Ga)Se-2 (ACIGS) solar absorber. ACIGS absorbers with Ag/Ag + Cu ratio (Ag/I) close to 20% were co-evaporated on a Mo-coated glass substrate and exposed to in-situ KF-PDT of various intensities. The current-voltage characteristics indicated that an optimized PDT can be beneficial, increasing in our study the median V-oc and efficiency values by +48 mV and + 0.9%(abs) (from 728 mV and 16.1% efficiency measured for the sample without PDT), respectively. However, an increased KF-flux during PDT resulted in a net deterioration of the performance leading to median V-oc and efficiency values as low as 503 mV and 4.7%. The chemical composition analysis showed that while the reference absorber without any post deposition treatment (PDT) was homogeneous, the KF-PDT induced a clear change within the first 10 nm from the surface. Here, the surface layer composition was richer in K and In with an increased Ag/I ratio, and its thickness seemed to follow the KF exposure intensity. Additionally, high-dose KF-PDT resulted in substantial formation of secondary phases for the ACIGS. The secondary phase precipitates were also richer in Ag, K, and In, and electron and X-ray diffraction data match with the monoclinic C 1 2/c 1 space group adopted by the Ag-alloyed KInSe2 phase. It could not be concluded whether the performance loss for the solar cell devices originated from the thicker surface layer or the presence of secondary phases, or both for the high-dose KF-PDT sample.

  • 94.
    Donzel-Gargand, Olivier
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Larsson, Fredrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Törndahl, Tobias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Stolt, Lars
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik. Solibro Research AB.
    Edoff, Marika
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Surface Modification And Secondary Phase Formation From a High Dose KF-Post Deposition Treatment of (Ag,Cu)(In,Ga)Se2 Solar Cell AbsorbersInngår i: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159XArtikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study we assessed the potential of KF-Post Deposition Treatment (PDT) performed on a silver-alloyed Cu(Inx,Ga1-x)Se2 (ACIGS) solar absorber. ACIGS absorbers with Ag/Ag+Cu ratio (Ag/I) close to 20% were co-evaporated on a Mo-coated glass substrate and exposed to in-situ KF-PDT of various intensities. The current-voltage characteristics indicated that an optimized PDT can be beneficial, increasing in our study the median Voc and efficiency values by +48 mV and +0.9 %abs (from 728 mV and 16.1 % efficiency measured for the sample without PDT), respectively. However, an increased KF-flux during PDT resulted in a net deterioration of the performance leading to median Voc and efficiency values as low as 503 mV and 4.7 %. The chemical composition analysis showed that while the reference absorber without any PDT was homogeneous, the KF-PDT induced a clear change within the first 10 nm from the surface. Here, the surface layer composition was richer in K and In with an increased Ag/I ratio, and its thickness seemed to follow the KF exposure intensity. Additionally, high-dose KF-PDT resulted in substantial formation of secondary phases for the ACIGS. The secondary phase precipitates were also richer in Ag, K and In, and Electron and X-ray diffraction data match with the monoclinic C 1 2/c 1 space group adopted by the Ag-alloyed KInSe2 (AKIS) phase. It could not be concluded whether the performance loss for the solar cell devices originated from the thicker surface layer or the presence of secondary phases, or both for the high-dose KF-PDT sample.

  • 95.
    Donzel-Gargand, Olivier
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Thersleff, T.
    Stockholm University, Department of Materials and Environmental Chemistry 106 91 Stockholm.
    Keller, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Törndahl, Tobias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Larsson, Fredrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Wallin, E.
    Solibro Research AB, Vallvägen 5, Uppsala, Sweden.
    Stolt, Lars
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik. Solibro Research AB, Vallvägen 5, Uppsala, Sweden.
    Edoff, Marika
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Cu-depleted patches induced by presence of K during growth of CIGS absorbers2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The conversion efficiency of the CIGS thin film solar cells has rapidly increased since introduction of the heavier alkali-doping (K, Rb, Cs). While the exclusive introduction of Na in the CIGS films has led to efficiencies up to 20,4% 1, the latest K, Rb or Cs post deposition treatments (PDT) have increased the efficiency to 22,6% 2. The exact role of this heavy-alkali PDT is still under discussion but three explanations have been discussed in the literature. First, that the heavy alkali PDT facilitates CdCu substitution, that results in an enhanced absorber type inversion, moving the p-n junction further into the CIGS bulk 3. Second, that the main effect from heavy alkali PDT is due to the formation of a K-In-Se2 layer, that passivates defects at the CIGS surface, reducing interface recombination 4. And third, that the heavy alkali PDT induces a Cu depletion at the surface of the CIGS which, by increasing the local Fermi level, increases the band bending; thus creating a higher potential barrier for holes to recombine 5.

  • 96.
    Donzel-Gargand, Olivier
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Thersleff, Thomas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Fourdrinier, Lionel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Leifer, Klaus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Edoff, Marika
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Surface defect passivation by a thin metallic barrier for Cu(InxGa1-x)Se2 co-evaporation on Cr-steel substrates2016Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 619, s. 220-226Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The use of Cr-steel substrates for the fabrication of Cu(In,Ga)Se2 (CIGS) solar cells is highly desirable and is a topic of considerable research interest. However, solar cells on non-treated steel substrates often exhibit decreased performance compared to their homologues on soda lime glass substrates. This is partly attributed to out-diffusion of steel components (Fe, Cr, Mn, etc.) into the solar cell. To avoid this contamination, thin film barriers can be added on top of the steel surface, but they do not always prevent the diffusion completely. In this paper we study the potential of using Cr and Ti as thin barrier layers. We find that local surface defects on the steel, several micrometers in height, lead to cracks in the back contact as well as in the barrier layers. Advanced transmission electron microscopy (TEM) techniques reveal that elemental diffusion and chemical reactions occur at these openings during heat treatments in Se atmosphere. TEM-energy dispersive X-ray spectroscopy (TEM-EDX) analysis in combination with calculation of the solid state diffusion coefficient demonstrate that a Cr-barrier sacrificially protects the Cr-steel substrate, blocking most of the Fe out-diffusion, whereas a Ti-barrier is less efficient.

  • 97.
    Donzel-Gargand, Olivier
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Thersleff, Thomas
    Stockholms Univ, Nat Skapliga Fak, Inst Mat & Miljokemi, Stockholm.
    Keller, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Törndahl, Tobias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Larsson, Fredrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Wallin, Erik
    Solibro Research AB, Uppsala, Sweden.
    Stolt, Lars
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik. Solibro Research AB, Uppsala, Sweden.
    Edoff, Marika
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Deep surface Cu depletion induced by K in high-efficiency Cu(In,Ga)Se2 solar cell absorbers2018Inngår i: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159X, Vol. 26, nr 9, s. 730-739Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, we used K‐rich glass substrates to provide potassium during the coevaporation of Cu(In,Ga)Se2 (CIGS) absorber layers. Subsequently, we applied a postdeposition treatment (PDT) using KF or RbF to some of the grown absorbers. It was found that the presence of K during the growth of the CIGS layer led to cell effi- ciencies beyond 17%, and the addition of a PDT pushed it beyond 18%. The major finding of this work is the observation of discontinuous 100‐ to 200‐nm‐deep Cu‐ depleted patches in the vicinity of the CdS buffer layer, correlated with the presence of K during the growth of the absorber layer. The PDT had no influence on the forma- tion of these patches. A second finding concerns the composition of the Cu‐depleted areas, where an anticorrelation between Cu and both In and K was measured using scanning transmission electron microscopy. Furthermore, a steeper Ga/(In+Ga) ratio gradient was measured for the absorbers grown with the presence of K, suggesting that K hinders the group III element interdiffusion. Finally, no Cd in‐diffusion to the CIGS layer could be detected. This indicates that if CdCu substitution occurs, either their concentration is below our instrumental detection limit or its presence is contained within the first 6 nm from the CdS/CIGS interface.

  • 98. Dubois, S.
    et al.
    de Bouw, M.
    Vanhellemont, Y.
    Stiernon, D.
    Trachte, S.
    Combining multi-view photogrammetry and wireless sensor networks when modelling the hygrothermal behaviour of heritage buildings2018Inngår i: Conference Report: The 3rd International Conference on Energy Efficiency in Historic Buildings / [ed] Tor Broström, Lisa Nilsen and Susanna Carlsten, Uppsala University, 2018, s. 154-162Konferansepaper (Fagfellevurdert)
  • 99.
    Dyachuk, Eduard
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Goude, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Berhnoff, Hans
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Simulating Pitching Blade With Free Vortex Model Coupled With Dynamic Stall Model For Conditions Of Straight Bladed Vertical Axis Turbines2014Inngår i: 33Rd International Conference On Ocean, Offshore And Arctic Engineering, 2014, Vol 9A: Ocean Renewable Energy, AMER SOC MECHANICAL ENGINEERS , 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This study is on the straight bladed vertical axis turbines, which can be utilized for both wind and marine current energy. Vertical axis turbines have the potential of lower installation and maintenance cost. However complex unsteady fluid mechanics of these turbines imposes significant challenges to the simulation tools. Dynamic stall is one of the phenomena associated with the unsteady conditions, and it is in the focus of the study. The dynamic stall effects are very important for vertical axis turbines, since they are usually passively controlled through the dynamic stall. A free vortex model is used to calculated unsteady attached flow, while the separatedflow is handled by the dynamic stall model. This is compared to the model based solely on the Leishman-Beddoes algorithm. The results are assessed against the measured data on pitching airfoils. A comparison of force coefficients between the simulations and experiments is done at the conditions similar to the conditions of H-rotor type vertical axis turbines.

  • 100.
    Edberg, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Reläskyddssystem för småskalig vattenkraft: En fallstudie för rekommenderad uppgradering av reläskyddssystem2016Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    This thesis aims to propose a recommended upgrade for the generator protectionsystems in small hydropower stations. The hydropower stations examined areBrantafors, Djupafors, Horkoneryd, Kallinge ,Karlsnäs, Ronneby and Verperyd. Therecommended generator protection systems are developed from regulations basedon constitutions from Svenska Kraftnät and Elsäkerhetsverket. The recommendationpresented in this thesis is a lowest recommendation for the generator protectionsystems of small hydropower stations and in some cases the owner of the powerplant may request above this lowest level of protection.

    The overall documentation of the stations has been inadequate and many parametersare unknown in the stations and therefore assumptions have been made. Theassumptions have a big influence on the short circuit calculations which affects therecommended settings for short circuit protection and therefore a conservativeapproach has been used.

    The result of this thesis is that the hydro power station Ronneby can’t manage therequirements specified from Svenska Kraftnät, and therefore the protection system inthe hydro power station need to be adjusted. The hydropower stations Brantaforsand Verperyd can with minor adjustments meet the recommended generatorprotection. On the stations Djupafors, Horkoneryd, Kallinge and Karlsnäs largerupgrades of the generator protection systems need to be done to fulfill therecommended protection system.

1234567 51 - 100 of 608
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf