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Lingfors, David, PhDORCID iD iconorcid.org/0000-0001-6586-4932
Alternative names
Publications (10 of 37) Show all publications
Gueymard, C. A., Bright, J. M., Lingfors, D., Habte, A. & Sengupta, M. (2019). A posteriori clear-sky identification methods in solar irradiance time series: Review and preliminary validation using sky imagers. Renewable & sustainable energy reviews, 109, 412-427
Open this publication in new window or tab >>A posteriori clear-sky identification methods in solar irradiance time series: Review and preliminary validation using sky imagers
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2019 (English)In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 109, p. 412-427Article, review/survey (Refereed) Published
Abstract [en]

This study examines all known methods that have been proposed in the literature to identify clear-sky periods in historical solar irradiance time series. Two different types of clear-sky detection (CSD) methods are discussed: those (16 total) that attempt to isolate periods of 1-min or more cloudless conditions, and those (5 total) that only attempt to detect clear-sun periods. All methods are found to rely on a diversity of inputs and on a variety of tests that typically examine the smoothness of the temporal variation of global and/or direct irradiance. Using samples of a few days with variable cloudiness, it is shown that these methods all have obvious strengths and weaknesses. Although this justifies a detailed validation to determine which method(s) could be best suited in the practice of solar radiation modeling or other applications, the current lack of appropriate equipment at high-quality reference radiometric stations prevents such an endeavor. Only a preliminary study is conducted here at seven stations of the SURFRAD network in the U.S., where 1-min irradiance measurements are available, along with sky data from a Total Sky Imager (TSI). The many limitations of the latter prevent its data to be considered "ground truth" here. Nevertheless, the comparison of the results from all CSD methods and 1.2 million TSI observations from all SURFRAD sites provides important qualitative and quantitative information, using a variety of performance indicators. Overall, two CSD methods appear more robust and are recommended, pending better high-resolution and high-performance cloud observations from modern sky cameras to redo these tests.

Keywords
Sky imager, Solar radiation, Global irradiance, Time series, Clear sky, Cloud fraction
National Category
Energy Engineering Energy Systems Meteorology and Atmospheric Sciences
Identifiers
urn:nbn:se:uu:diva-385778 (URN)10.1016/j.rser.2019.04.027 (DOI)000467752400025 ()
Available from: 2019-06-17 Created: 2019-06-17 Last updated: 2019-06-17Bibliographically approved
Åberg, M., Lingfors, D., Olauson, J. & Widén, J. (2019). Can electricity market prices control power-to-heat production for peak shaving of renewable power generation?: The case of Sweden. Energy, 176, 1-14
Open this publication in new window or tab >>Can electricity market prices control power-to-heat production for peak shaving of renewable power generation?: The case of Sweden
2019 (English)In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 176, p. 1-14Article in journal (Refereed) Published
Abstract [en]

100% renewable energy systems require high penetration of variable renewable electricity (VRE) generation. This causes the net load in the system to be more variable and could cause operational problems in local power grids. Demand side management (DSM), such as fuel or energy carrier switching in response to a price signal, can provide flexibility to meet the increased variability. This study investigates the impact of VRE production on electricity prices and their potential to act as an incentive to control district heating power-to-heat (P2H) production in order to shave VRE production peaks. Also, the potential to increase P2H production flexibility with additional heat storages is studied. Electricity prices are simulated by modification of historical electricity market supply curves. A heat storage component is implemented in an existing model for district heat production. The results show that P2H production is significantly increased (up to 98%) when electricity prices are influenced by VRE production. Thermal storages further increase the P2H production by up to 46%. The increased P2H production, however, does not necessarily coincide with the peaks of VRE. Thus, in conclusion, the pricing mechanism on the Nord pool electricity market is insufficient to control P2H production for shaving VRE production peaks. (C) 2019 Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Power-to-heat, District heating, Electricity market prices, Renewable electricity generation, Heat storage, Demand response
National Category
Energy Systems
Identifiers
urn:nbn:se:uu:diva-389819 (URN)10.1016/j.energy.2019.03.156 (DOI)000470939500001 ()
Funder
Swedish Energy Agency, P42904-1
Available from: 2019-07-30 Created: 2019-07-30 Last updated: 2019-07-30Bibliographically approved
Lingfors, D., Johansson, T., Widén, J. & Broström, T. (2019). Target-based visibility assessment on building envelopes: Applications to PV and cultural-heritage values. Energy and Buildings, 204, Article ID 109483.
Open this publication in new window or tab >>Target-based visibility assessment on building envelopes: Applications to PV and cultural-heritage values
2019 (English)In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, ISSN 03787788, Vol. 204, article id 109483Article in journal (Refereed) Published
Abstract [en]

Solar energy applications have, in recent years, become a common element in the urban landscape, especially on roofs and facades. However, it is important that the integration of solar energy in the built environment do not distort the fabric or expression of the existing building envelope, not at least in areas of high cultural-heritage values. The aesthetics depend, to a large extent, on how visible the new technology, such as photovoltaic (PV) panels, is. This paper describes a method for visibility assessment of building envelopes. It is referred to as target-based as it, in contrast to previously reported methods, bases the assessment from the perspective of the building envelope itself, rather than possible vantage points on the ground. The method was evaluated for two Swedish cities; Stockholm and Visby. In Stockholm, each building was evaluated based on its cultural-heritage values, solar irradiation and visibility. Deploying PV only on the roofs with the lowest cultural-heritage values, with insolation > 900 kWh/m2, and with no visibility from ground, results in a total PV yield of up to 2% of the total electricity demand. In Visby, various definitions of the vantage area were evaluated, from which the building envelope can be seen. It was found that the choice of vantage area greatly impacts the solar energy potential. If the vantage area is defined by the public domain, i.e., streets and other public open spaces, the non-visible roof area doubles compared to if all ground/terrain defines it. Compared to previous studies, the use of a vantage area, instead of discrete vantage points, seems to result in higher visibility of the roofs.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Visibility assessment; Photovoltaics; Building preservation
National Category
Building Technologies
Research subject
Engineering Science with specialization in Civil Engineering and Built Environment
Identifiers
urn:nbn:se:uu:diva-397881 (URN)10.1016/j.enbuild.2019.109483 (DOI)
Funder
Swedish Energy Agency, 45891-1
Available from: 2019-11-27 Created: 2019-11-27 Last updated: 2019-11-28Bibliographically approved
Etherden, N., Ahlberg, J., Lingfors, D. & Kvamme, K. (2018). Calculating the hosting capacity of electrical network with high penetration of solar PV. In: Energynautics GmbH (Ed.), Proc. of the 8th International Workshop on the Integration of Solar Power into Power Systems: . Paper presented at 8th International Workshop on the Integration of Solar Power into Power Systems, 16 – 17 October 2018, Stockholm, Sweden (pp. 1-6).
Open this publication in new window or tab >>Calculating the hosting capacity of electrical network with high penetration of solar PV
2018 (English)In: Proc. of the 8th International Workshop on the Integration of Solar Power into Power Systems / [ed] Energynautics GmbH, 2018, p. 1-6Conference paper, Published paper (Refereed)
Abstract [en]

This paper describes a method to determine the Hosting Capacity (HC) for solar Photovoltaics (PV) in distribution networks. The method uses hourly load data and roof-top PV power production simulation data in a commercial Network Information System (NIS). The HC – defined as the maximum amount of new PV that can be connected without endangering the reliability or quality for other customers - is monitored for each node in the network with different proportions of the buildings having PV installations. The times- series of PV power generation are influenced by both local weather conditions and shading to ensure that only profitable installations are simulated. The method captures the variability of load and production and enables simultaneous evaluation of several of the most common mitigation actions in networks with high PV penetration. Presented is a case study of a network with 51 secondary substations and 534 customer networks in central Sweden. With PV applied to 10% of the best roof locations, some local voltage issues arise. With limited mitigation actions at critical locations the network can host as much of 30% of the best roof-top locations having PV.

Keywords
Hosting Capacity, Solar PV, Network Integration
National Category
Energy Engineering
Research subject
Engineering Science
Identifiers
urn:nbn:se:uu:diva-363676 (URN)978-3-9820080-0-4 (ISBN)
Conference
8th International Workshop on the Integration of Solar Power into Power Systems, 16 – 17 October 2018, Stockholm, Sweden
Projects
UPGRID project no. 646.531A.B
Available from: 2018-10-19 Created: 2018-10-19 Last updated: 2018-10-25Bibliographically approved
Bright, J. M., Gueymard, C. A., Killinger, S., Lingfors, D., Sun, X., Wang, P. & Engerer, N. A. (2018). Climatic and Global Validation of Daily MODIS Precipitable Water Data at AERONET Sites for Clear-sky Irradiance Modelling. In: Proceedings of the ISES EuroSun 2018 Conference: 12th International Conference on Solar Energy for Buildings and Industry. Paper presented at 12th International Conference on Solar Energy for Buildings and Industry (ISES EuroSun), Fachhochschule Ostschweiz, Hochschule Technik Rapperswil, Rapperswil, Switzerland, September 10-13, 2018 (pp. 1490-1501). International Solar Energy Society
Open this publication in new window or tab >>Climatic and Global Validation of Daily MODIS Precipitable Water Data at AERONET Sites for Clear-sky Irradiance Modelling
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2018 (English)In: Proceedings of the ISES EuroSun 2018 Conference: 12th International Conference on Solar Energy for Buildings and Industry, International Solar Energy Society, 2018, p. 1490-1501Conference paper, Published paper (Refereed)
Abstract [en]

Precipitable water (PW) is an influential variable in regards to clear-sky radiation modelling and solar resource assessment. Thus, the accuracy of solar energy estimates depends on the accuracy of PW measurements. Gridded satellite information is commonly used for solar modelling because of its benefit of a broad geographical coverage, thus a global validation of commonly utilised PW products is imperative. Here, all Level-3 Moderate Resolution Imaging Spectroradiometer (MODIS) daily PW products from the Aqua and Terra satellites (at 1° × 1° spatial resolution) from 01/2000 to 02/2018 are compared and validated against all of NASA’s ground-sensing Aerosol Robotic NETwork (AERONET) V3 Level-2 PW daily averages from sites that have at least one year of observa- tions during 2000–2018 (452 sites representing 675,158 observations). Furthermore, sub-categorisation by Kö- ppen-Geiger climate regions enables climate specific validation to ascertain any distinct climatic influence. The results demonstrate significant climatological influences that impact the derived PW products. It is found that the Terra PW is more accurate than the Aqua PW, and that blending these two products yields a higher accuracy of daily PW estimates. The MODIS PW product also suffers from overestimation at larger magnitudes (>3 cm). The absolute errors do not reduce linearly with the PW magnitude, so that relative errors are far worse in areas of low PW, such as the polar climate. The equatorial climate, with the highest PW records, behaves best. Finally, a simple sensitivity test using the REST2 clear-sky radiation model shows that the global PW RMSE (0.511 cm) of the combined MODIS data would result in a 1.5-2.5% under- or overestimate on direct normal irradiance (DNI) de- pending on latitude relative to using the AERONET mean PW of 1.8971 cm. It is thus concluded that the daily MODIS PW product is not ideal for clear-sky radiation modelling, at least whenever accurate DNI predictions are necessary on a global scale.

Place, publisher, year, edition, pages
International Solar Energy Society, 2018
National Category
Energy Engineering
Research subject
Engineering Science
Identifiers
urn:nbn:se:uu:diva-363677 (URN)10.18086/eurosun2018.09.07 (DOI)000475550900156 ()978-3-9820408-0-6 (ISBN)
Conference
12th International Conference on Solar Energy for Buildings and Industry (ISES EuroSun), Fachhochschule Ostschweiz, Hochschule Technik Rapperswil, Rapperswil, Switzerland, September 10-13, 2018
Available from: 2018-10-19 Created: 2018-10-19 Last updated: 2019-08-22Bibliographically approved
Bright, J. M., Killinger, S., Lingfors, D. & Engerer, N. A. (2018). Improved satellite-derived PV power nowcasting using real-time power data from reference PV systems. Solar Energy, 168, 118-139
Open this publication in new window or tab >>Improved satellite-derived PV power nowcasting using real-time power data from reference PV systems
2018 (English)In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 168, p. 118-139Article in journal (Refereed) Published
Abstract [en]

Rapid growth in the global penetration of solar photovoltaic (PV) systems means electricity network operators and electricity generators alike are increasingly concerned with the short-term solar forecasting (nowcasting) of solar irradiance. This paper proposes a methodology that considers a varying number of available reference PV systems for supporting satellite-derived PV power real-time nowcasting. We evaluate conventional satellite-only and upscaling-only PV fleet estimate methodologies and compare them to two newly developed correction and hybrid cases. When using only a single reference PV system to estimate the aggregated power of 48 independent target PV systems for the location of Canberra, Australia; we show that the newly proposed correction or hybrid cases improve the performance of the satellite-derived PV power estimate medians in terms of MBE, rMBE, RMSE and rRMSE from 0.031 W/W-p, 7.46%, 0.079 W/W-p and 23.4%, down to 0.006 W/W-p,-0.711%, 0.068 W/W-p and 20.0%, representing relative improvements of 80.6%, 90.5%, 13.9% and 14.5%, respectively. Similarly, when using 30 reference PV systems, we report median improvements from 0.036 W/W-p, 8.25%, 0.083 W/W-p and 24.8%, down to 0.01 W/W-p, 1.41%, 0.049 W/W-p and 11.4%, representing relative improvements of 72.2%, 82.9%, 41.0% and 54.0%, respectively. We discuss the fundamental challenges facing the use of reference PV systems, satellite-derived power estimates, combining the two data sources, and the knowledge required to address these issues. We ultimately conclude that combining satellite-based PV power estimates with data from reference PV systems is always more beneficial than either on their own.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2018
Keywords
Real-time nowcasting, Reference PV systems, PV fleet estimates, Satellite irradiance
National Category
Energy Engineering
Identifiers
urn:nbn:se:uu:diva-361102 (URN)10.1016/j.solener.2017.10.091 (DOI)000437814800008 ()
Available from: 2018-09-21 Created: 2018-09-21 Last updated: 2018-10-19
Lingfors, D., Shepero, M., Good, C., Bright, J. M., Widén, J., Boström, T. & Munkhammar, J. (2018). Modelling City Scale Spatio-temporal Solar Energy Generation and Electric Vehicle Charging Load. In: Energynautics GmbH (Ed.), Proc. of the 8th International Workshop on the Integration of Solar Power into Power Systems: . Paper presented at 8th International Workshop on the Integration of Solar Power into Power Systems. Stockholm, 16-17 October, 2018..
Open this publication in new window or tab >>Modelling City Scale Spatio-temporal Solar Energy Generation and Electric Vehicle Charging Load
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2018 (English)In: Proc. of the 8th International Workshop on the Integration of Solar Power into Power Systems / [ed] Energynautics GmbH, 2018Conference paper, Published 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.

National Category
Energy Engineering
Research subject
Engineering Science
Identifiers
urn:nbn:se:uu:diva-363672 (URN)978-3-9820080-0-4 (ISBN)
Conference
8th International Workshop on the Integration of Solar Power into Power Systems. Stockholm, 16-17 October, 2018.
Available from: 2018-10-19 Created: 2018-10-19 Last updated: 2018-10-29Bibliographically approved
Killinger, S., Lingfors, D., Saint-Drenan, Y.-M., Moraitis, P., van Sark, W., Taylor, J., . . . Bright, J. M. (2018). On the search for representative characteristics of PV systems: Data collection and analysis of PV system azimuth, tilt, capacity, yield and shading. Solar Energy, 173, 1087-1106
Open this publication in new window or tab >>On the search for representative characteristics of PV systems: Data collection and analysis of PV system azimuth, tilt, capacity, yield and shading
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2018 (English)In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 173, p. 1087-1106Article in journal (Refereed) Published
Abstract [en]

Knowledge of PV system characteristics is needed in different regional PV modelling approaches. It is the aim of this paper to provide that knowledge by a twofold method that focuses on (1) metadata (tilt and azimuth of modules, installed capacity and specific annual yield) as well as (2) the impact of shading. Metadata from 2,802,797 PV systems located in Europe, USA, Japan and Australia, representing a total ca-pacity of 59 GWp (14.8% of installed capacity worldwide), is analysed. Visually striking interdependencies of the installed capacity and the geographic location to the other parameters tilt, azimuth and specific annual yield motivated a clustering on a country level and between systems sizes. For an eased future utilisation of the analysed metadata, each parameter in a cluster was approximated by a distribution function. Results show strong characteristics unique to each cluster, however, there are some commonalities across all clusters. Mean tilt values were reported in a range between 16.1° (Australia) and 35.6° (Belgium), average specific annual yield values occur between 786 kWh/kWp (Denmark) and 1426 kWh/kWp (USA South). The region with smallest median capacity was the UK (2.94 kWp) and the largest was Germany (8.96 kWp). Almost all countries had a mean azimuth angle facing the equator. PV system shading was considered by deriving viewsheds for ≈48,000 buildings in Uppsala, Sweden (allranges of solar angles were explored). From these viewsheds, two empirical equations were derived related to irradiance losses on roofs due to shading. The first expresses the loss of beam irradiance as a function of the solar elevation angle. The second determines the view factor as a function of the roof tilt including the impact from shading and can be used to estimate the losses of diffuse and reflected irradiance.

Keywords
PV system characteristics, Metadata, Shading, Data analysis
National Category
Energy Engineering
Research subject
Engineering Science
Identifiers
urn:nbn:se:uu:diva-363680 (URN)10.1016/j.solener.2018.08.051 (DOI)000452940800106 ()
Available from: 2018-10-19 Created: 2018-10-19 Last updated: 2019-01-16Bibliographically approved
Lingfors, D., Donarelli, A. & Widén, J. (2018). Solenergi på kulturhistoriska byggnader. Bygg & Teknik, 5
Open this publication in new window or tab >>Solenergi på kulturhistoriska byggnader
2018 (Swedish)In: Bygg & Teknik, ISSN 0281-658X, Vol. 5Article in journal (Refereed) Published
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.

National Category
Energy Engineering
Research subject
Engineering Science
Identifiers
urn:nbn:se:uu:diva-363689 (URN)
Projects
Byggnadsantikvarisk solkartering: Potential för solelproduktion i kulturhistoriskt värdefull bebyggelse, Spara & Bevara nr. 45891-1
Available from: 2018-10-19 Created: 2018-10-19 Last updated: 2019-02-14Bibliographically approved
Lingfors, D. & Widén, J. (2018). Solenergipotentialen för Skånes bebyggelse enligt två framtidsscenarier. Lund: Energikontoret Skåne
Open this publication in new window or tab >>Solenergipotentialen för Skånes bebyggelse enligt två framtidsscenarier
2018 (Swedish)Report (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.

Place, publisher, year, edition, pages
Lund: Energikontoret Skåne, 2018. p. 65
National Category
Energy Engineering
Research subject
Engineering Science
Identifiers
urn:nbn:se:uu:diva-363683 (URN)
Available from: 2018-10-19 Created: 2018-10-19 Last updated: 2018-10-23Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-6586-4932

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