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  • 1.
    Ayob, Mohd Nasir
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. Univ Malaysia Perlis, Sch Mechatron Engn, Arau 02600, Perlis, Malaysia.
    Castellucci, Valeria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Göteman, Malin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Abrahamsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Engström, Jens
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Waters, Rafael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Small-Scale Renewable Energy Converters for Battery Charging2018In: Journal of Marine Science and Engineering, E-ISSN 2077-1312, Vol. 6, no 1, article id 26Article in journal (Refereed)
    Abstract [en]

    This paper presents two wave energy concepts for small-scale electricity generation. In the presented case, these concepts are installed on the buoy of a heaving, point-absorbing wave energy converter (WEC) for large scale electricity production. In the studied WEC, developed by Uppsala University, small-scale electricity generation in the buoy is needed to power a tidal compensating system designed to increase the performance of the WEC in areas with high tides. The two considered and modeled concepts are an oscillating water column (OWC) and a heaving point absorber. The results indicate that the OWC is too small for the task and does not produce enough energy. On the other hand, the results show that a hybrid system composed of a small heaving point absorber combined with a solar energy system would be able to provide a requested minimum power of around 37.7W on average year around. The WEC and solar panel complement each other, as the WEC produces enough energy by itself during wintertime (but not in the summer), while the solar panel produces enough energy in the summer (but not in the winter).

  • 2. Berggren, Björn
    et al.
    Wall, Maria
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Karlsson, Björn
    Att definiera nollenergibyggnader: En internationell angelägenhet2012In: Bygg & teknik, no 2, p. 21-23Article in journal (Refereed)
  • 3.
    Berggren, Björn
    et al.
    Lund University.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Karlsson, Björn
    Mälardalen University.
    Wall, Maria
    Lund University.
    Evaluation and optimization of a Swedish Net ZEB - Using load matching and grid interaction indicators2012In: Proceedings of the First Building Simulation and Optimization Conference, Loughborough, UK, September 10-11, 2012, 2012Conference paper (Refereed)
    Abstract [en]

    Net Zero Energy Buildings, Net ZEBs, is one of many necessary measures for climate change mitigation as they may reduce the energy consumption in the building sector. The Net ZEB interacts with a grid infrastructure. It is therefore important to consider the interaction with the grid in the design phase.

    This paper reports an evaluation of a proposed designof a Net ZEB in the south of Sweden evaluating load matching and grid interaction using simulated datasets with hourly resolution. The aim was to find a design with as high load matching and as low grid interaction as possible.

    The results show difficulties of achieving a high load matching between the building load and on-site generation, due to the Nordic climate and the relatively low loads during daytime, when the availability of solar energy is high. The building is likely to accomplish the goal of a Net ZEB balance. If higher flexibility is sought, a larger energy storage should be considered.

  • 4. Candanedo, José
    et al.
    Salom, Jaume
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Athienitis, Andreas
    Load matching, grid interaction, and advanced control2015In: Modeling, Design, and Optimization of Net-Zero Energy Buildings / [ed] Athienitis, Andreas; O'Brien, William, John Wiley & Sons, 2015Chapter in book (Refereed)
  • 5. Ellegård, Kajsa
    et al.
    Vrotsou, Katerina
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    VISUAL-TimePAcTS/energy use - a software application for visualizing energy use from activities performed2010In: Proceedings of the 3rd International Conference on Energy Systems with IT, Älvsjö, Sweden, March 16-17, 2010, 2010Conference paper (Refereed)
  • 6. Ellegård, Kajsa
    et al.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Elanvändning i vardagen: En kunskapsöversikt inom ELAN-programmet2006Report (Refereed)
  • 7.
    Ellegård, Kajsa
    et al.
    Linköping University.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Vrotsou, Katerina
    Appliances facilitating everyday life - electricity use derived from daily activities2011In: Proceedings of the World Renewable Energy Congress, Linköping, Sweden, May 8-13, 2011, 2011Conference paper (Refereed)
  • 8.
    Grahn, Pia
    et al.
    KTH.
    Munkhammar, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Alvehag, Karin
    KTH.
    Söder, Lennart
    KTH.
    PHEV Home-Charging Model Based on Residential Activity Patterns2013In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 28, no 3, p. 2507-2515Article in journal (Refereed)
    Abstract [en]

    Plug-in hybrid electric vehicles (PHEVs) have received an increased interest lately since they provide an opportunity to reduce greenhouse gas emissions. Based on the PHEV introduction level in the car park, the charging behaviors in an area will induce changes in the load profiles of the power system. Hence, it becomes important to investigate what impact a given PHEV introduction level has on load profiles due to expected charging behavior of residents. This paper proposes a new model for generating PHEV home-charging patterns by combining PHEV usage with synthetic activity generation of residents' electricity-dependent activities. The synthetic activity data are simulated based on time-use data collected in time diaries, and define the basis for calculations of the PHEV home-charging behavior as well as the resident's electricity consumption. The proposed model is generic and can be used where similar residential time-use data are available. Based on the underlying activities, the model estimates the total load profile due to residential load as well as the variation in the load profile. The resulting load profiles can be used in load shaving studies in order to investigate what type of activities, PHEV usage or other, may be moved to hours with lower demand.

  • 9. Kall, Ann-Sofie
    et al.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Det stora i det lilla och det lilla i det stora: Politik och teknik i omställningen av energisystemet2007Report (Other academic)
  • 10.
    Karlsson, Kristina
    et al.
    Linköping University.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hushållens elanvändningsmönster identifierade i vardagens aktiviteter2008Report (Refereed)
  • 11. Karlsson, Magnus
    et al.
    Palm, Jenny
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Interdisciplinary Energy System Methodology: A compilation of research methods used in the Energy Systems Programme2011Report (Refereed)
  • 12.
    Lingfors, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Bright, Jamie M
    Australian National University.
    Engerer, Nicholas A
    Australian National University.
    Ahlberg, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Killinger, Sven
    Australian National University.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Comparing the capability of low- and high-resolution LiDAR data with application to solar resource assessment, roof type classification and shading analysis2017In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 205, p. 1216-1230Article in journal (Refereed)
    Abstract [en]

    LiDAR (Light Detection and Ranging) data have recently gained popularity for use in solar resource assessment and solar photovoltaics (PV) suitability studies in the built environment due to robustness at identifying building orientation, roof tilt and shading. There is a disparity in the geographic coverage of low- and high-resolution LiDAR data (LL and LH, respectively) between rural and urban locations, as the cost of the latter is often not justified for rural areas where high PV penetrations often pose the greatest impact on the electricity distribution network. There is a need for a comparison of the different resolutions to assess capability of LL. In this study, we evaluated and improved upon a previously reported methodology that derives roof types from a LiDAR-derived, low-resolution Digital Surface Model (DSM) with a co-classing routine. Key improvements to the methodology include: co-classing routine adapted for raw LiDAR data, applicability to differing building type distribution in study area, building height and symmetry considerations, a vector-based shading analysis of building surfaces and the addition of solar resource assessment capability.

    Based on the performance of different LiDAR resolutions within the developed model, a comparison between LL (0.5-1 pts/m(2)) and LH (6-8 pts/m(2)) LiDAR data was applied; LH can confidently be used to evaluate the applicability of LL, due to its significantly higher point density and therefore accuracy. We find that the co-classing methodology works satisfactory for LL for all types of building distributions. Roof-type identification errors from incorrect co-classing were rare (< 1%) with LL. Co-classing buildings using LL improves accuracy of roof-type identification in areas with homogeneous distribution of buildings, here from 78% to 86% in accuracy. Contrastingly, co-classing accuracy using LH is marginally reduced for all building distributions from 94.8% to 94.4%. We adapt the Hay and Davies solar transposition model to include shading. The shading analysis demonstrates similarity of results between LL and LH. We find that the proposed methodology can confidently be used for solar resource assessments on buildings when only LiDAR data of low-resolution (< 1 pts/m(2)) is available.

  • 13.
    Lingfors, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Donarelli, Anna
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Department of Art History, Conservation.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Solenergi på kulturhistoriska byggnader2018In: Bygg & Teknik, ISSN 0281-658X, Vol. 5Article in journal (Refereed)
    Abstract [sv]

    År 2040 ska 5-10 procent av den svenska elmixen komma från sol- energi. En stor del av dagens sol- cellsinstallationer är uppförda på byggnader och det är troligt att den trenden kommer att hålla i sig. Samtidigt omfattas en stor del av byggnadsbeståndet av olika lag- skydd på grund av kulturhistoriska värden vilket kräver särskild varsamhet när man installerar sol- celler på dessa byggnader. I ett nystartat forskningsprojekt kom- mer verktyg och riktlinjer tas fram som tar hänsyn till både de tekniska och arkitektoniska aspekterna av solcellsinstallationer på kulturhistoriskt värdefulla byggnader.

  • 14.
    Lingfors, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Marklund, Jesper
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Maximizing PV hosting capacity by smart allocation of PV: A case study on a Swedish distribution grid2015In: Proceedings of ASES Solar 2015, Pennsylvania State University, Pennsylvania, USA, July 28-30, 2015, 2015Conference paper (Other academic)
    Abstract [en]

    Detailed simulations of large amounts of PV production in Swedish rural power grids show that as module and system prices keep declining and thus increasing the profitability and demand for solar power, current grid performance will limit the potential. Simulations have been made on a case distribution grid (10 kV) with actual hourly load data for 2014 and calculated hourly production with respect to building roof area, tilt and azimuth together with irradiation data. At high production, especially voltage rises along cables in the outer part of the grid is problematic, but also currents in cables close to transformer buses increases substantially at these conditions. Resulting hosting capacity for the case grid is 32%, as of annual production compared to annual demand. What is limiting the hosting capacity is the tolerated voltage rise, which is set to 5% of nominal grid voltage. Through smart allocation of PV systems to the strongest nodes in the grid the hosting capacity of the same grid can be increased to 74%.

  • 15.
    Lingfors, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Shepero, Mahmoud
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Good, Clara
    The Arctic University of Norway.
    Bright, Jamie M
    Australian National University.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Boström, Tobias
    The Arctic University of Norway.
    Munkhammar, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Modelling City Scale Spatio-temporal Solar Energy Generation and Electric Vehicle Charging Load2018In: Proc. of the 8th International Workshop on the Integration of Solar Power into Power Systems / [ed] Energynautics GmbH, 2018Conference paper (Refereed)
    Abstract [en]

    This study presents a model for estimatingbuilding-applied photovoltaic (PV) energy yield and electric ve- hicle (EV) charging temporally over time and spatially on a city scale. The model enables transient assessment of the synergy between EV and PV, thus is called the EV-PV Synergy Model. Spatio-temporal data on solar irradiance is used in combination with Light Detection and Ranging (LiDAR) data to generate realistic spatio-temporal solar power generation profiles. The spatio-temporal EV charging profiles are produced with a stochastic Markov chain model trained on a large Swedish data set of travel patterns combined with OpenStreetMap (OSM) for deterministically identifying parking spaces in cities. The modelled estimates of solar power generation andEV charging are combined to determine the magnitude and correlation between PV power generation and EV charging over time on city scale for Uppsala, Sweden. Two months (January and July) were simulated to represent Sweden’s climate extremes. The EV penetration level was assumed to be 100% and all the roofs with yearly irradiation higher than 1000 kWh/m2 were assumed to have PV panels. The results showed that, even in January with the lowestsolar power generation and maximum EV load, there can be a positive net-generation (defined as the integration of PV generation minus EV charging load over time) in some locations within the city. Central locations exhibited a positive temporal correlation between EV charging load and PV generation. Negative temporal correlations were observed in the outskirts of the city, where typically night time home-charging was prevalent. In the highest PV power generation month (July) the solar generation was 16 times higher than the EV charging load. Spatially, the net-generation was positive in almost the entire city. However, the time-series correlation between the EV charging load and the PV generation reached more extreme positive and negative values in comparison with January. This was a result of the higher variability in irradiance during July in comparison with January. In summary, we find that there is a favorable synergy of EV-PV technology within the city center with assumptions of workplace charging behaviors for both winter and summer months. An unfavorable synergy with suburban areas where typically nighttime charging behaviors negatively correlate to PV generation. This suggests that distributed PV should be targeted around city center/workplace EV charging stations.

  • 16.
    Lingfors, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Development and validation of a wide-area model of hourly aggregate solar power generation2016In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 102, p. 559-566Article in journal (Refereed)
    Abstract [en]

    The impact of photovoltaics (PV) on the power system becomes increasingly important to study as the penetration of PV has increased rapidly over the last decade. A physical model for aggregated PV generation has been developed for the Swedish spot market areas. Information about PV systems within the Swedish electricity certificate system and irradiance data from the meteorological model STRÅNG were used as inputs. The model was trained and validated against production data reported to the Swedish transmission system operator. Our model shows high correlation (0.95-0.99) to reported historical production data. However, it overestimates extreme 1h ramp rates, which are -20% and 22% for down- and up-ramps respectively, compared to -13% and 14% for the reported data. Furthermore a weighting function was developed, which takes demography, available solar irradiance and today's PV deployment into account, to model likely deployment in a Swedish high penetration scenario, where PV covers 6% of the total annual power demand. The difference in extreme 1 and 4 hour step changes before and after introducing PV is small. The model could thus be used with confidence to model the impact on the power system for future scenarios of high PV penetration.

  • 17.
    Lingfors, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Evaluation of Datasets and Methods to Derive 3D Building Models and their Influence on PV Power Integration Studies2018In: Proc. of the 8th International Workshop on the Integration of Solar Power into Power Systems / [ed] Energynautics GmbH, Energynautics GmbH, 2018Conference paper (Refereed)
    Abstract [en]

    A Geographic Information System (GIS) is apowerful tool for studying the impact of building-applied PV systems on the power system. The grid operator can be advised on exactly which parts of the grid may suffer from problems with operational performance (e.g., over-voltages and over- currents). However, this requires the PV power generation to be realistically modelled, for which a crucial first step is to find representative building models. In this study, we compare the accuracy of two types of aerial data, LiDAR (Light Detection And Ranging) and photogrammetry data, and two methods for identifying building models from these data, a raster- based and a vector-based model. The results show that with photogrammetry data, the roof topology of buildings is not identified correctly as often as with LiDAR data, and the vector- based method gives a far better representation of the roofs than the raster-based method. We exemplify this by comparing the results of power-flow simulations on a distribution grid with about 5000 customers where PV systems have been deployed on the roofs according to the two different methods. For the raster-based method the PV power potential is almost four times higher than for the vector-based method, which overestimates impacts on the simulated performance of the grid. The conclusion of the study is therefore that for accurate simulations of the impact of building-applied PV on grid performance based on GIS data, the proposed vector-based method should be used, rather than the raster-based, and it should be based on LiDAR data rather than photogrammetry data.

  • 18.
    Lingfors, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Solenergipotentialen för Blekinges bebyggelse enligt två framtidsscenarier2014Report (Other academic)
  • 19.
    Lingfors, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Solenergipotentialen för Skånes bebyggelse enligt två framtidsscenarier2018Report (Other academic)
    Abstract [sv]

    Under de senaste åren har det skett en mycket snabb utbyggnad av solenergi i bebyggelsen i många länder, initialt i europeiska länder som Tyskland, Italien och Spanien men idag sker en snabb utveckling i de flesta länder i världen. I Sverige har användningen av solenergi tagit fart lite senare än i de södra grannländerna, mycket på grund av låga elkostnader från vatten- och kärnkraft. I samband med att investeringsstöd för solceller introducerades 2009 har dock solcellsmarknaden tagit fart om än från en låg nivå (se Figur 1). Från att solenergi framförallt nyttjats för uppvärmning eller för elgenerering vid fritidshuset eller båten sker nu installeringar av solcellsystem på framförallt villatak och lokaler i Sverige.För att möta både internationella såväl som lokala målsättningar att minskaklimatpåverkan är det viktigt att få en bild av potentialen för olika typer av förnybar energitillförsel. Den här studien är genomförd på uppdrag av Länsstyrelsen i Skåne med syfte att bedöma potentialen för solenergi på takytor inom hela länet, men även uppdelat på kommunnivå, både i närtid och med en längre tidshorisont. Utifrån trenden med sjunkande priser på solceller har potentialen för solvärme bedömts mycket liten, men kan delvis vara intressant för småhus.Potentialberäkningarna utgår från byggnadsbeståndet i fastighetskartan, uppdelat på olika byggnadstyper, där kvalificerade antaganden gjorts för vilken grad takytor för olika byggnadstyper kan utnyttjas för solenergi.Resultaten visar att det finns ungefär 105 km2 tillgänglig takyta för solenergi. Den realiserbara potentialen bedöms vara 3.1 TWh i scenario A samt 7.5 TWh i scenario B. Detta kan jämföras med elkonsumtionen i Skåne län som uppgick till 12.1 TWh 2014.

  • 20.
    Lingfors, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Marklund, Jesper
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Boork, Magdalena
    SP Technical Research Institute of Sweden.
    Larsson, David
    School of Business Society and Engineering, Mälardalen University.
    Photovoltaics in Swedish agriculture: Technical potential, grid integration and profitability2015In: Proceedings of the ISES Solar World Congress 2015, Daegu, Korea, November 8-12, 2015, 2015Conference paper (Other academic)
    Abstract [en]

    This paper investigates the realizable potential for photovoltaic (PV) systems in Swedish agriculture. Marginal lands and available building areas for PV systems are quantified, and factors limiting the potential are analyzed. It is shown that the potential for PV in Swedish agriculture is high, but what is fully realizable is limited by the capacity of the rural power grid. A case study in the rural municipality of Herrljunga was conducted and scaled to national level. The study shows that the risk of surges in the medium voltage grid (10 kV) in rural areas are small in case where all roof surfaces with an annual solar irradiance of over 950 kWh/m2 are used for solar power. The total electricity production from the Swedish agriculture, if all roof areas with this irradiance level were used, is estimated to 4 TWh annually. With solar power on all roof surfaces with an annual irradiance of at least 900 kWh per m2 problems with voltage rise and overloads in the electricity grid might occur. The electrical grid capacities thus substantially limit how much solar power can be installed. Our results also show that the profitability limits the potential to 0.2 TWh on a national level, but that it could increase if more optimistic economic conditions are assumed.

  • 21.
    Lingfors, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Seipel, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Visual Information and Interaction. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis and Human-Computer Interaction.
    Interactive visual simulation for photovoltaic design and planning in the built environment2013Conference paper (Other academic)
  • 22.
    Lingfors, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Zimmermann, Uwe
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Determining Intra-hour Solar Irradiance Variability with a Low-cost Solar Logger Network2014In: Proceedings of 4th International Workshop on Integration of Solar Power into Power Systems, Berlin, Germany, 10-11 November, 2014, 2014Conference paper (Other academic)
    Abstract [en]

    The study of solar irradiance is of vital importance in order to quantify the fluctuation that the transmission system needs to handle in case of large scale solar power integration. In this paper, early results from a low-cost solar irradiance logger network are presented. The main advantages of the solar logger are its low cost (~$50) and mobility. Our results confirm previous models of the station pair correlation of clear sky index step changes, with the modification that the isotropic correlation appears to decrease exponentially as a function of Δt-1/2 rather than Δt-1 as has been proposed earlier.

  • 23.
    Luthander, Rasmus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lingfors, David
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Munkhammar, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Self-consumption enhancement of residential photovoltaics with battery storage and electric vehicles in communities2015In: Proceedings of the eceee 2015 Summer Study on energy efficiency, 1–6 June 2015, Presqu’île de Giens, Toulon/Hyères, France, 2015, p. 991-1002Conference paper (Refereed)
    Abstract [en]

    Grid-connected photovoltaic (PV) systems have been dependent on supporting schemes to be competitive with conventional electricity generation. Selling prices of PV power production are now lower than buying prices in several countries, making it profitable to match generation with household consumption. Self-consumption, calculated as in situ instantaneous consumption of PV power production relative to total power production, can be used to improve the profitability with higher buying than selling prices of electricity. Another measure, self-sufficiency, similar to self-consumption but calculated relative to the yearly consumption, can also be used. Battery storage and electric vehicle (EV) home-charging are interesting alternatives to increase the self-consumption, since the PV power production can be stored for later use. This study uses high-resolution consumption data for 21 single-family houses in Sweden and irradiance data for the year 2008 to examine the potential for battery storage and EV home-charging for communities of single-family houses with PV systems. The aim is to compare how self-consumption and self-sufficiency are affected by individual power grid connections for all households versus one shared grid connection for the whole community. These scenarios are combined with battery storage and EV charging (individual versus centralized). It is found that total consumption profiles level out when several houses are connected together, the self-consumption increases from 52 to 71 % and the self-sufficiency from 12 to 17 %. The size of a centralized storage can be reduced compared to the aggregated size of storages in every house to reach the same level of self-consumption. The potential for EV charging is limited due to mismatch between irradiance and charging patterns. The extra revenue from increased self-consumption with battery storage is too low for all the cases to justify an investment in batteries since the prices are still too high. With dedicated support schemes, higher buying prices of electricity and cheaper battery, PV-battery systems can still be an interesting solution in countries with high solar irradiance throughout the year.

  • 24.
    Luthander, Rasmus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lingfors, David
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Large-scale integration of photovoltaic power in a distribution grid using power curtailment and energy storage2017In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 155, p. 1319-1325Article in journal (Refereed)
  • 25.
    Luthander, Rasmus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lingfors, David
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Munkhammar, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Preventing overvoltage in a distribution grid with large penetration of photovoltaic power2016In: Proceedings of the 6th International Workshop on Integration of Solar into Power Systems / [ed] Uta Betancourt / Thomas Ackermann, Darmstadt, Germany: Energynautics GmbH, 2016, p. 113-118Conference paper (Other academic)
    Abstract [en]

    Photovoltaic (PV) power generation is an important component in the future energy system. High penetration of PV power in a distribution power grid might however lead to overvoltage, i.e. +10% of rated voltage, for end-users. This study compares PV power curtailment and decentralized energy storage for overvoltage prevention in a 400V/10 kV distribution grid with large penetration of PV. LiDAR analysis is used to identify rooftops suitable for PV in a Swedish distribution grid with more than 5000 end-users. Results show that power curtailment allows 22% PV electricity (19 GWh) relative to total consumption on a yearly basis without overvoltage. PV production is reduced with 0.35 GWh due to curtailment. Decentralized energy storage of in total 86 MWh capacity achieves the same result.

  • 26.
    Luthander, Rasmus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Shepero, Mahmoud
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Munkhammar, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Photovoltaics and opportunistic electric vehicle charging in a Swedish distribution grid2017In: Proceedings of the 7th International Workshop on Integration of Solar into Power Systems, Darmstadt, Germany: Energynautics GmbH, 2017Conference paper (Refereed)
    Abstract [en]

    Renewable distributed generation and electric vehicles (EVs) are two important components in the transitions to a more sustainable society. However, both distributed generation and EV charging pose new challenges to the power system due to intermittent generation and high-power EV charging. In this case study, a power system consisting of a low- and medium-voltage distribution grid with more than 5000 customers, high penetration of roof-top mounted photovoltaic (PV) power systems and a fully electrified car fleet is used to assess the impact of the intermittent PV generation and high-power EV charging loads. Two summer weeks and two winter weeks with and without EV charging and a PV penetration varying between 0% and 100% of the annual electricity consumption are examined using measured and simulated data. Results show that the electricity consumption increases with 9% and 18% during the studied periods, and that EV charging only marginally can contribute to lowering the risk of overvoltage for customers resulting from PV overproduction. The most significant result is the increase in undervoltage in the winter when EV charging is introduced. The share of customers affected by undervoltage increases from 0% to close to 1.5% for all PV penetration levels.

  • 27.
    Luthander, Rasmus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Stridh, Bengt
    Mälardalens högskola.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    PV system layout for optimized self-consumption2014In: Proceedings of the 29th European Photovoltaic Solar Energy Conference, 2014Conference paper (Other academic)
    Abstract [en]

    With decreasing subsidies for PV systems, increased self-consumption of PV electricity could improve the profitability of grid-connected residential PV systems. Self-consumption is in this paper defined as the share of the PV production consumed in a building on an hourly basis. With higher prices for buying than selling electricity, the revenue due to self-consumption is higher than the profit of selling electricity to the grid. The focus of this paper is the potential to increase the self-consumption with alternative PV system layouts, i.e. several different azimuth and tilt angles, called 3DPV. Hourly data from an existing PV system on a detached house outside Västerås, Sweden, combined with meteorological and spot price data of electricity has been used, all from 2011. The results of one-year simulations show increased self-consumption and decreased PV production with 3DPV compared to a south-oriented PV system. The revenue decreases with 3DPV when using historical hourly spot market data. However, there are other benefits with 3DPV such as decreased rated power of the inverter due to lower PV peak production.

  • 28.
    Luthander, Rasmus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Munkhammar, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lingfors, David
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Self-consumption enhancement and peak shaving of residential photovoltaics using storage and curtailment2016In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 112, p. 221-231Article in journal (Refereed)
    Abstract [en]

    Increasing the self-consumption of photovoltaic (PV) power is an important aspect to integrate more PV power in the power system. The profit for the PV system owner can increase and the stress on the power grid can be reduced. Previous research in the field has focused on either self-consumption of PV power in individual buildings or PV power curtailment for voltage control. In this paper self-consumption of residential PV power in a community of several single-family houses was investigated using high-resolution irradiance and power consumption data. Cases with individual or shared battery energy storages for the houses were examined. PV power curtailment was investigated as a method to reduce feed-in power to the grid, i.e. peak shaving. Results indicated that the self-consumption ratio increased when using shared instead of individual storage. Reducing the feed-in power from the community by almost 50% only led to maximum 7% yearly production losses due to curtailment and storage losses. The economics for shared storage are slightly better than for individual ones. These results suggest that residential PV-battery systems should use (i) shared energy storage options if local regulations allow it and (ii) PV power curtailment if there are incentives to lower the feed-in power.

  • 29.
    Luthander, Rasmus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nilsson, Daniel
    Linköpings universitet.
    Palm, Jenny
    Linköpings universitet.
    Photovoltaic self-consumption in buildings: A review2015In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 142, p. 80-94Article, review/survey (Refereed)
    Abstract [en]

    The interest in self-consumption of PV electricity from grid-connected residential systems is increasing among PV system owners and in the scientific community. Self-consumption can be defined as the share of the total PV production directly consumed by the PV system owner. With decreased subsidies for PV electricity in several countries, increased self-consumption could raise the profit of PV systems and lower the stress on the electricity distribution grid. This review paper summarizes existing research on PV self-consumption and options to improve it. Two options for increased self-consumption are included, namely energy storage and load management, also called demand side management (DSM). Most of the papers examine PV-battery systems, sometimes combined with DSM. The results show that it is possible to increase the relative self-consumption by 13-24% points with a battery storage capacity of 0.5-1. kW. h per installed kW PV power and between 2% and 15% points with DSM, both compared to the original rate of self-consumption. The total number of papers is however rather limited and further research and more comparative studies are needed to give a comprehensive view of the technologies and their potential. Behavioral responses to PV self-consumption and the impact on the distribution grid also need to be further studied.

  • 30.
    Molin, Andreas
    et al.
    Linköpings universitet.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Moshfegh, Bahram
    Linköpings universitet.
    Increasing photovoltaic power supply self-consumption by on-site batteries for a large flat-roof industrial premise2013In: Proceedings of the 28th European Photovoltaic Solar Energy Conference (EU PVSEC), Paris, France, September 30 - October 4, 2013., 2013Conference paper (Refereed)
  • 31. Molin, Andreas
    et al.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Stridh, Bengt
    Karlsson, Björn
    Konsekvenser av avräkningsperiodens längd vid nettodebitering av solel2010Report (Refereed)
  • 32.
    Monie, Svante
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nilsson, Annica
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lingfors, David
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Åberg, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Thermal Energy Storages in Residential Areas: – a potential to increase renewable power generation?2018In: 2018 ACEEE Summer Study on Energy Efficiency in Buildings: Making Efficiency Easy and Enticing / [ed] Fred Grossberg, Washington D.C., 2018, Vol. 20, p. 11-1-11-12, article id 0194_0286_000156Conference paper (Refereed)
    Abstract [en]

    With an increased ambition of implementing renewable electricity production in our energy systems follows the need of handling the inherent variability from some of these production sources (e.g. wind and solar). This could be via curtailments, infrastructural reinforcements of the power grid, and/or increased utilization of power system reserves. The aim of this study was to investigate if power surplus and deficit due to mismatch between intermittent power generation and power demand could be reduced with electric heat pumps (used for power-to-heat purposes), combined heat and power (CHP) production (for power balancing), and seasonal thermal energy storage (STES) (as buffering capacity). A residential area consisting of buildings refurbished for improved energy performance, roof top solar photovoltaic (PV) systems, a local heat distribution system, a small-scale CHP plant, central heat pumps, and a STES, was simulated. The heat pumps were given priority to use surplus power from roof top PV generation or surplus from the grid (e.g. wind power). The CHP plant produced power during power deficits. Surplus heat from the CHP plant as well as from the heat pumps was stored in the STES. The results showed a reduction of the surplus power from the local PV systems towards the upstream power grid. Also, the possibility to offer regulative service towards upstream power grid by using CHP was demonstrated. The conclusion is that power-to-heat and CHP can significantly reduce the mismatch between variable power generation and power demand.

  • 33.
    Munkhammar, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Grahn, Pia
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Quantifying self-consumption of on-site photovoltaic power generation in households with electric vehicle home charging2013In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 97, p. 208-216Article in journal (Refereed)
    Abstract [en]

    Photovoltaic (PV) power production and residential power demand are negativelycorrelated at high latitudes on both annual and diurnal basis. If PVpenetration levels increase, methods to deal with power overproduction in the localdistribution grids are needed to avoid costly grid reinforcements. Increased local consumption isone such option. The introduction of a home-chargedplug-in electric vehicle (PEV) has a significant impact on the household load and potentiallychanges the coincidence between household load and photovoltaic power production.This paper uses a stochastic model to investigate the effect on the coincidence between householdload and photovoltaic power production when including a PEV load. The investigationis based on two system levels: (I) individual householdlevel and (II) aggregate household level. The stochastic model produces theoretical high-resolutionload profiles for household load and home charged PEV load over time.The photovoltaic power production model is based on high-resolution irradiance data for Uppsala, Sweden.It is shown that the introduction of a PEV improves the self-consumption of the photovoltaicpower both on an individual and an aggregate level, but the increase is limited due to thelow coincidence between the photovoltaic power production pattern and the charging patterns of the PEV.

  • 34.
    Munkhammar, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Rydén, Jesper
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Mathematics.
    Widen, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Characterizing probability density distributions for household electricity load profiles from high-resolution electricity use data2014In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 135, p. 382-390Article in journal (Refereed)
    Abstract [en]

    This paper presents a high-resolution bottom-up model of electricity use in an average household based on fit to probability distributions of a comprehensive high-resolution household electricity use data set for detached houses in Sweden. The distributions used in this paper are the Weibull distribution and the Log-Normal distribution. These fitted distributions are analyzed in terms of relative variation estimates of electricity use and standard deviation. It is concluded that the distributions have a reasonable overall goodness of fit both in terms of electricity use and standard deviation. A Kolmogorov-Smirnov test of goodness of fit is also provided. In addition to this, the model is extended to multiple households via convolution of individual electricity use profiles. With the use of the central limit theorem this is analytically extended to the general case of a large number of households. Finally a brief comparison with other models of probability distributions is made along with a discussion regarding the model and its applicability.

  • 35.
    Munkhammar, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Rydén, Jesper
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Mathematics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lingfors, David
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Simulating dispersed photovoltaic power generation using a bimodal mixture model of the clear-sky index2015Conference paper (Refereed)
    Abstract [en]

    Improved probability distribution models for power generation are useful e.g. forprobabilistic power flow simulations. This paper presents a distribution modelfor photovoltaic (PV) power generation based on the clear-sky index.With the use of minute-resolution data on globalhorizontal irradiation (GHI) we fit unimodal normal,bimodal normal and trimodal normal mixture distributionfamilies to the clear-sky index. Based on Kolmogorov-Smirnov (K-S) teststhe best fit distribution family consisting of a bimodal normal distribution isthen used for estimating an aggregate clear-sky index for multipledispersed locations that are assumed to be uncorrelated in terms of sky clearness.For five or more locations the aggregate clear-sky indexfollows a normal distribution due to the central limit theorem.Models for solar radiation on tilted planes and PV power generation areapplied to the clear-sky index to generate probability distributions for anarbitrary PV system.

  • 36.
    Munkhammar, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    A flexible Markov-chain model for simulating demand side management strategies with applications to distributed photovoltaics2012In: Proceedings of the World Renewable Energy Forum 2012, Denver, Colorado, USA, May 13-17, 2012, 2012, p. 1858-1865Conference paper (Refereed)
    Abstract [en]

    In this paper a stochastic model for load shifting was utilized for the purpose of investigating the potential for increased self-consumption of photovoltaic (PV) generation in households. We show the results in terms of power consumption, PV power production and solar fraction from a number of scenarios involving end-user flexibility on the order of a few percent. Simulations are performed on both an individual and an aggregate level. Results indicate that the solar fraction is only improved by a few percent both on an aggregate and individual level even for the most extreme scenarios of load shifting. The lack of substantial increase in solar fraction from imposed flexibility can partly be attributed to complementary energy use; when certain energy-demanding activities are downshifted in probability other activities are up-shifted. Another explanation for the lack of increased solar fraction is the total available fraction of flexible activities at a certain time.

  • 37.
    Munkhammar, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    A Markov-chain probability distribution mixture approach to the clear-sky index2018In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 170, p. 174-183Article in journal (Refereed)
    Abstract [en]

    This paper presents a Markov-chain probability distribution mixture approach to the clear-sky index (CSI). The main assumption is that the temporal variability of the state of clear and the state of cloudy can be described by a two-state Markov-chain, and the variability within each state can be approximated by a probability distribution, unique for each state. Measurables such as the mean clear-sky index, fraction of bright sunshine, expected duration of clearness and expected duration of cloudiness events are shown to be related to the parameters of the method. Additionally, the \AA ngstr\"om equation, which relates mean normalized solar irradiance to the fraction of bright sunshine, is shown to arise as the expectation of the method. In order to numerically verify the method, a simulation model is constructed based on data sets for two different climatic regions: Norrk\"oping, Sweden and Oahu, Hawaii, USA. Results from the simulation model based on training data shows good agreement with testing data, and when comparing the results to existing models in the literature it is comparable to the state of the art. It is shown that the simulation model generates a non-trivial, generally non-zero, autocorrelation function. Finally, challenges with the method and open problems are discussed.

  • 38.
    Munkhammar, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    A stochastic model for collective resident activity patterns and energy use: preliminaries2012In: Future technology press, 2012, p. 1-4Conference paper (Other academic)
  • 39.
    Munkhammar, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    An autocorrelation-based copula model for generating realistic clear-sky index time-series2017In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 158, p. 9-19Article in journal (Refereed)
    Abstract [en]

    This study presents a method for using copulas to model the temporal variability of the clear-sky index, which in turn can be used to produce realistic time-series of photovoltaic power generation. The method utilizes the autocorrelation function of a clear-sky index time-series, and based on that a correlation matrix is set up for the dependency between clear-sky indices at Ntime-steps. With the use of this correlation matrix an N-dimensional copula function is configured so that correlated samples for these N time-steps can be obtained. Results from the copula model are compared with the original data set and an uncorrelated model based on zero correlated clear-sky index data in terms of distribution, autocorrelation, step changes and distribution. The copula model is shown to be superior to the uncorrelated model in these aspects. As a validation the model is tested with solar irradiance for two different geographical regions: Norrköping, Sweden and Hawaii, USA. The copula model is also applied to a set of bins of daily mean clear-sky index and the use of bins is shown to improve the results.

  • 40.
    Munkhammar, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    An autocorrelation-based copula model for producing realistic clear-sky index and photovoltaic power generation time-series2017In: Photovoltaic specialist conference, Washington, 2017, p. 1-6Conference paper (Refereed)
    Abstract [en]

    This study presents a method for using copulas to model the temporal variability of the clear-sky index. The method utilizes the autocorrelation function and correlated outputs for N time-steps are obtained. Results from the copula model are, in terms of distribution, autocorrelation, step changes and mean daily distribution, compared with the original data set and with an uncorrelated model based on random clear-sky index data. The copula model is shown to be superior to the uncorrelated model in all these aspects.

  • 41.
    Munkhammar, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    An N-state Markov-chain mixture distribution model of the clear-sky index2018In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 173, p. 487-495Article in journal (Refereed)
    Abstract [en]

    This paper presents an N-state Markov-chain mixture distribution approach to model the clear-sky index. The model is based on dividing the clear-sky index data into bins of magnitude and determining probabilities for transitions between bins. These transition probabilities are then used to define a Markov-chain, which in turn is connected to a mixture distribution of uniform distributions. When trained on measured data, this model is used to generate synthetic data as output. The model is an N-state generalization of a previously published two-state Markov-chain mixture distribution model applied to the clear-sky index. The model is tested on clear-sky index data sets for two different climatic regions: Norrköping, Sweden, and Oahu, Hawaii, USA. The model is also compared with the two-state model and a copula model for generating synthetic clear-sky index time-series as well as other existing clear-sky index generators in the literature. Results show that the N-state model is generally on par with, or superior to, state-of-the-art synthetic clear-sky index generators in terms of Kolmogorov–Smirnov test statistic, autocorrelation and computational speed.

  • 42.
    Munkhammar, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Copula correlation modeling of aggregate solar irradiance in spatial networks2016In: Proceedings of the 6th lnternational Workshop on Integration of Solar Power into Power Systems, Wien, 2016Conference paper (Refereed)
    Abstract [en]

    Estimating solar irradiance over several locations in a spatial network is of interest for a wide variety of applications, in particular for simulations of distribution grid with high photovoltaic (PV) penetration. This paper presents a method for estimating the clear-sky index for N locations in any spatial network of locations. The model is based on the clear-sky index distribution for one location, and the cross-correlation of clear-sky index between all location pairs. The correlated clear-sky index for each location is obtained from a copula model of correlation based on the station pair correlations and the clear-sky index for a single location. In this paper the clear-sky index for a single location is obtained by a bimodal mixture distribution model and the correlation between station pairs is modeled via an exponential model. The model bridges the gap between estimating the clear-sky index for adjacent and maximally dispersed locations. Applications of this model to simulations of aggregate photovoltaic power generation is also discussed.

  • 43.
    Munkhammar, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Correlation modeling of instantaneous solar irradiance with applications to solar engineering2016In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 133, p. 14-23Article in journal (Refereed)
    Abstract [en]

    Estimating solar irradiance, in particular its variability, on Earth's surface is paramount for solar engineering and for improving the utilization of solar energy. This paper presents a novel approach to statistical modeling of instantaneous solar irradiance by using a multivariate probability distribution-a copula-to describe the dependency between beam and diffuse indices. This approach significantly simplifies certain calculations for solar energy engineering, which is shown with simulated outputs for photovoltaic (PV) systems for different orientations. The PV power generation is expressed as probability distributions, which is directly applicable for power system operation and design. It is also shown that an Angstrom-type equation, which is historically useful in relating time of bright sunshine to average solar radiation, is the statistical expectation of solar irradiance in this model.

  • 44.
    Munkhammar, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    On a Probability Distribution Convolution Approach to Clear-Sky Index and a Generalized Ångström EquationManuscript (preprint) (Other academic)
    Abstract [en]

    We show that by modeling solar beam irradiance approximately as a simple Bernoulli distribution and diffuse irradiance as a Gamma distribution, a generalized Ångström equation relating solar irradiation to sunshine hours follows directly as aconsequence of the convolution of beam and diffuseirradiance distributions into a distribution for the clear-sky index.

  • 45.
    Munkhammar, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Grahn, Pia
    KTH.
    Rydén, Jesper
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Mathematics.
    A Bernoulli Distribution Model for Plug-in Electric Vehicle Charging based on Time-use Data for Driving Patterns2014In: Proceedings of IEEE International Electric Vehicle Conference (IEVC), 2014Conference paper (Refereed)
    Abstract [en]

    This paper presents a Bernoulli distribution model for plug-in electric vehicle (PEV)charging based on high resolution activity data for Swedish drivingpatterns. Based on the activity ``driving vehicle" from a time diary studya Monte Carlo simulation is made of PEV state of chargewhich is then condensed down to Bernoulli distributions representingcharging for each hour during weekday and weekend day. Thesedistributions are then used as a basis for simulations of PEVcharging patterns. Results regarding charging patterns for a numberof different PEV parameters are shown along with a comparison with resultsfrom a different stochastic model for PEV charging. A convergence test forMonte Carlo simulations of the distributions is also provided.In addition to this we show that multiple PEV charging patterns are representedby Binomial distributions via convolution ofBernoulli distributions. Also the distribution for aggregatecharging of many PEVs is shown to be normally distributed. Finally a fewremarks regarding the applicability of the model are given along witha discussion on potential extensions.

  • 46.
    Munkhammar, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hinkelman, Laura M.
    Joint Institute for the Study of the Atmosphere and Ocean, University of Washington, 3737 Brooklyn Ave. NE, Seattle, WA 98105, United States..
    A copula method for simulating correlated instantaneous solar irradiance in spatial networks2017In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 143, p. 10-21Article in journal (Refereed)
    Abstract [en]

    This paper presents a method for generating correlated instantaneous solar irradiance data for an arbitrary set of spatially dispersed locations. Based on the empirical clear-sky index distribution for one location and the cross-correlation between clear-sky index data at all location pairs, a copula is used to represent the dependence between locations. The method is primarily intended for probabilistic simulations of electricity distribution grids with high penetrations of photovoltaic (PV) systems, in which solar irradiance data for nodes in the grid can be sampled from the model. The method is validated against a 10-s resolution solar irradiance data set for 14 locations, dispersed within an array of approximately 1 km 1.2 km, at the Island of Oahu, Hawai’i, USA. The results are compared with previous results for along- and cross-wind pairs of locations, and with models for adjacent (completely correlated) and dispersed (completely uncorrelated) locations. It is shown that the copula approach performs better than the adjacent model for a majority of all location pairs and for all but one pair of locations separated more than 500 m. It outperforms the dispersed model for all pairs of locations. In conclusion, the proposed method can generate correlated data and estimate the aggregate clear-sky index for any set of locations based only on the distribution of the clear-sky index for a single location.

  • 47.
    Munkhammar, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nilsson, Annica
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Photovoltaic self-consumption potential of alternative year-round daylight savings time2013In: Proceedings of the 28th European Photovoltaic Solar Energy Conference (EU PVSEC), Paris, France, September 30 - October 4, 2013., 2013, p. 4753-4757Conference paper (Refereed)
    Abstract [en]

    In a mature photovoltaic (PV) market where feed-in tariffs have declined, managing of the hosting capacity of the distribution grid becomes essential by maximizing the utilization of PV. One way to increase hosting capacity is to increase self-consumption of the self-produced PV power. This paper investigates the effect of an alternative year-round daylight savings time (DST) – where the time of the entire society is changed relative to the sun - on the level of self-consumption in terms of solar fraction and load fraction of PV power both on household- and national level. Household electricity use was modeled with a Markov-chain model, PV power production was modeled from solar irradiance data, and the national level was simulated using national electricity data. Results show that one hour year-round DST shifted ahead might increase self-consumption by a fraction of one percentage point for a net-zero energy household. For a 30 GWp PV installation on a national scale with a 140 TWh annual electricity use one hour DST shift ahead had almost no effect on self-consumption. The optimal self-consumption of PV power on the national level was concluded to be the current DST setup.

  • 48.
    Munkhammar, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Rydén, Jesper
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Mathematics, Applied Mathematics and Statistics.
    On a probability distribution model combining household power consumption, electric vehicle home-charging and photovoltaic power production2015In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 142, p. 135-143Article in journal (Refereed)
    Abstract [en]

    In this paper we develop a probability distribution model combining household power consumption, electric vehicle (EV) home-charging and photovoltaic (PV) power production. The model is set up using a convolution approach to merge three separate existing probability distribution models for household electricity use, EV home-charging and PV power production. This model is investigated on two system levels: household level and aggregate level of multiple households. Results for the household level show the power consumption/production mismatch as probability distributions for different time bins. This is further investigated with different levels of PV power production. The resulting yearly distribution of the aggregate scenario of multiple uncorrelated households with EV charging and PV power production is shown to not be normally distributed due to the mismatch of PV power production and household power consumption on a diurnal and annual basis.

  • 49.
    Munkhammar, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wickman, Per
    Electric Vehicle Charging and Photovoltaic Power Production from Eight Solar Charging Stations in Sweden2014In: 4th Solar Integration Workshop: Proceedings of the 4th International Workshop on Integration of Solar Power into Power Systems, Darmstadt: Energynautics , 2014, p. 425-429Conference paper (Refereed)
    Abstract [en]

    This paper quantifies and analyzes data for electric vehicle (EV) charging and photovoltaic(PV) power production from eight charging stations in Sweden withadjacent PV power production provided by Solelia Greentech AB. This study aims toshow the grid interaction of EV charging and PV power production from these solar charging stationswhich are distributed in pairs at four different locations across Sweden. This study utilizesone minute resolution data on power consumption and production from between 281 and310 consecutive days depending on available solar charging station data. Each site, correspondingto two adjacent solar charging stations, has a specific setup regarding EV charging consumer availability.EV charging at two of the sites were available only for the local company/municipality employees and visitors to the company/municipalitywhile the other two sites were public. There was no economical charge for EV charging at any of the stations.Results show that EV charging magnitude and use patterns over timevaried considerably between the stations. Half of the stations had a net consumption of electricityand the other half of stations had a net production of electricity during the metering period.Self-consumption of PV power production was estimated to be between 0.2 and 10 percentdepending on station.

  • 50. Norberg, Ida
    et al.
    Pettersson, Ola
    Gustavsson, Alf
    Kovacs, Peter
    Boork, Magdalena
    Ollas, Patrik
    Widén, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lingfors, David
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Marklund, Jesper
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Larsson, David
    Ingman, Daniel
    Jältorp, Hans
    Solel i lantbruket: Realiserbar potential och nya affärsmodeller2015Report (Other academic)
123 1 - 50 of 111
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