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Task 36
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The following are publications developed under Task 36:

General Publications

Solar Dataset
United Nations Environment Programme
October 2011 - Posted: 11/4/2012
The United Nations Environmental Programme (UNEP) is hosting an online guide that ISES developed together with UNEP and partners from the German Aerospace Centre (DLR), the U.S. National Renewable Energy Laboratory (NREL) and the State University of New York at Albany. This guide helps users make an educated decision when deciding which solar dataset to use for a specific application and/or at a specific location. Knowledge of solar energy resources is essential for the planning and operation of solar energy systems. Different organisations provide several autonomous solar data covering various spatial and temporal periods with various resolutions. Solar data sets differ in spatial and temporal resolution, time period covered, and methodology used. Some of these datasets are available for free, while some are not, and they all may provide varying results. As a result, most users cannot verify the suitability of a given solar dataset or map for a specific application. This can lead users to abandon their search or make non-appropriate use of the information. This simple guide tool was developed to help alleviate this problem. The online user-friendly guide helps expert and non-expert users to decide which solar resource data sets are the most appropriate depending on a type of application that the user is interested in and the location. The programme relates information back to two information tables: one related to a compilation of a selection of existing satellite based solar datasets and their metadata and the other defines specific requirements a dataset should meet for specific solar application.
Task 36 Poster at Eurosun 2010
Presented at Euroson 2010, Graz, Austria
September 2010 - PDF 0.29MB - Posted: 8/15/2011
By: David Renne
Task 36 is also Task 5 in SolarPACES and a collaboraHve task with PVPS. Task 36 ends on 30 June 2011, but then a new Task will be implemented titled “Solar Resource Assessment and Forecasting”.

Subtask A: Standard Qualification for Solar Resource Products

Five Satellite Products Deriving Beam and Global Irradiance Validation on Data from 23 Ground Stations
February 2011 - PDF 2.22MB - Posted: 8/16/2011
By: Pierre Ineichen, University of Geneva
Models converting satellite images into the different radition components become increasingly performing and give often better estimation of solar irradiance availability that ground measurements if the station is not situated in the near vicinity of the application.

Five different satellite products deriving both global and beam irradiance are validated against data from 23 ground sites. The main conclusions are:

- the global irradiance is retrieved with a negligible bias and an average standard deviation around 16% for best algorithm. For the beam irradiance, the bias is around several percents, and the standard deviation around 35%,
- the main deviation comes from the knowledge of the aerosol optical depth,
- the high latitude sites give not poorer results than the other sites.
Five Satellite Products Deriving Beam and Global Irradiance Validation on Data from 23 Ground Stations
Developing a Guide for Non-experts to Determine the Most Appropriate Use of Solar Energy Resource Information
July 2010 - PDF 0.31MB - Posted: 4/14/2012
By: Carsten Hoyer-Klick, Jennifer McIntosh, Magda Moner-Girona, David Renné, Richard Perez, Daniel Puig
Knowledge of the solar energy resource is essential for the planning and operation of solar energy systems. There are a large number of different data sources available which makes it difficult for the non-expert in solar resource assessment to judge which source might be appropriate for a specific application. The United Nations Environmental Programme (UNEP) therefore supported the development of a Guide which will help users to make an educated decision about which data set to choose among several different available. The Guide basically consists of two tables. The first one is a description of the data sources. The second table consists of recommendations of minimum requirements in the characteristics of the data depending on different applications.
Task 36 Poster at Eurosun 2010
July 2010 - PDF 0.19MB - Posted: 4/14/2012
By: C. Hoyer-Klick, H.G. Beyer, D. Dumortier, M. Schroedter-Homscheidt, L. Wald, M. Martinoli, C. Schilings, B. Gschwind, L. Menard, E. Gaboardi, L. Ramirez-Santigosa, J. Polo, T. Cebecauer,T. Huld, M. Suri, M. de Blas, E. Lorenz, R. Pfatischer, J. Remund, P. Ineichen, A. Tsvetkov, J. Hofierka
Knowledge of the solar energy resource is essential for the planning and operation of solar energy systems. In past years there has been substantial European and national funding to develop information systems on solar radiation data, leading to the situations that several data bases exist in parallel, developed by different approaches, various spatial and temporal coverages and resolutions including those exploiting satellite data. By comparing these products the users may end up with different results for the same requested sites. The MESoR project has defined a number of benchmarking measures and rules and applied them in several benchmarking exercises. This paper will show key results. To ease access to the data a new broker portal has been developed. The paper will show how it can be used to retrieve data or to make data available within the portal.
Task 36 Paper - Management and Exploitation of Solar Resource Knowledge - 2010
July 2010 - PDF 0.47MB - Posted: 4/14/2012
By: C. Hoyer-Klick, H.G. Beyer, D. Dumortier, M. Schroedter-Homscheidt, L. Wald, M. Martinoli, C. Schillings, B. Gschwind5, L. Menard, E. Gaboardi, L. Ramirez-Santigosa, J. Polo, T. Cebecauer,T. Huld, M. Suri, M. de Blas, E. Lorenz, C. Kurz, J. Remund, P. Ineichen, A. Tsvetkov, J. Hofierka
Knowledge of the solar energy resource is essential for the planning and operation of solar energy systems. In past years there has been substantial European and national funding to develop information systems on solar radiation data, leading to the situations that several data bases exist in parallel, developed by different approaches, various spatial and temporal coverages and resolutions including those exploiting satellite data. By comparing these products the users may end up with different results for the same requested sites. The MESoR project has defined a number of benchmarking measures and rules and applied them in several benchmarking exercises. This paper will show key results. To ease access to the data a new broker portal has been developed. The paper will show how it can be used to retrieve data or to make data available within the portal.
Analysis of different comparison parameters applied to solar radiation data from satellite and German radiometric stations
January 2009 - Posted: 8/12/2011
By: Bella Espinara, Lourdes Ramíreza, Anja Drewsb, Hans Georg Beyerc, Luis F. Zarzalejoa, Jesús Poloa, , and Luis Martín
In this paper new comparison parameters are defined for assessing statistical similarity between two data sets. The new parameters are based on the commonly used Kolmogorov–Smirnov test. They allow quantifying differences between the cumulative distribution functions of each data series. These parameters are applied to global horizontal daily irradiation values from pyranometric measurements and satellite data. The test data from 38 stations distributed throughout Germany cover the time from 1995 until 2003. The results affirm that the new parameters contribute valuable information to the comparison of data sets complementing those that are found with the mean bias and root mean squared differences.
Task 36 Paper - Management and Exploitation of Solar Resource Knowledge - 2008
July 2008 - PDF 0.72MB - Posted: 4/14/2012
By: C. Hoyer-Klick, H.G. Beyer, D. Dumortier, M. Schroedter-Homscheidt, L. Wald, M. Martinoli, C. Schilings, B. Gschwind, L. Menard, E. Gaboardi, L. Ramirez-Santigosa, J. Polo, T. Cebecauer,T. Huld, M. Suri, M. de Blas, E. Lorenz, R. Pfatischer, J. Remund, P. Ineichen, A. Tsvetkov, J. Hofierka
Knowledge of the solar energy resource is essential for the planning and operation of solar energy systems. In past years there has been substantial European and national funding to develop information systems on solar radiation data, leading to the situations that several data bases exist in parallel, developed by different approaches, various spatial and temporal coverages and resolutions including those exploiting satellite data. The user of these products may end up with different results for the same requested sites. To better guide the users, a benchmarking exercise is under preparation. A set of reference data has been collected and benchmarking measures and rules have been defined. The results of the benchmarking and the feedback from stakeholders will be integrated into a guide of best practices in the application of solar resource knowledge. Access to data has been quite fragmented. Each service has its own way of access to the data and delivery format. A new broker portal based on the experience of the project Soda aims to unify and ease the access to distributed data sources and applications providing solar resource information.
Task 36 Poster at Eurosun 2008
July 2008 - PDF 1.25MB - Posted: 4/14/2012
By: C. Hoyer-Klick, H.G. Beyer, D. Dumortier, M. Schroedter-Homscheidt, L. Wald, M. Martinoli, C. Schilings, B. Gschwind, L. Menard, E. Gaboardi, L. Ramirez-Santigosa, J. Polo, T. Cebecauer,T. Huld, M. Suri, M. de Blas, E. Lorenz, R. Pfatischer, J. Remund, P. Ineichen, A. Tsvetkov, J. Hofierka
Knowledge of the solar energy resource is essential for the planning and operation of solar energy systems. In past years there has been substantial European and national funding to develop information systems on solar radiation data, leading to the situations that several data bases exist in parallel, developed by different approaches, various spatial and temporal coverages and resolutions including those exploiting satellite data. By comparing these products the users may end up with different results for the same requested sites. The MESoR project has defined a number of benchmarking measures and rules and applied them in several benchmarking exercises. This paper will show key results. To ease access to the data a new broker portal has been developed. The paper will show how it can be used to retrieve data or to make data available within the portal.

Subtask C: Improved Techniques for Solar Resource Characterization and Forecasting

Subtask C-1: Enhanced Satellite Methodologies

Direct Normal Irradiance for CSP Based on Satellite Images of Meteosat Second Generation
2009 - Posted: 12/8/2011
We present a method to derive the direct normal irradiance (DNI) from MSG data. For this, we apply the Heliosat method and a new model for the direct fraction of the irradiance. The clear sky irradiance is mainly determined by the aerosol optical depth (AOD) and water vapour content, which are taken from suitable climatologies. The accuracy of satellite derived DNI data has been analyzed for Spanish sites, more sites will be evaluated within the project SESK (Standardisierung der Ertragsprognose Solarthermischer Kraftwerke – standardization of yield prognosis for solar thermal power plants). As for concentrating solar power (CSP) the frequency distribution of DNI is of special importance, special attention is given to correct modeling of this feature.
Combining Solar Irradiance Measurements and Various Satellite-Derived Products to a Site-Specific Best Estimate
July 2008 - Posted: 12/8/2011
By: Hoyer-Klick, C., Lorenz, E., Hammer, A. Beyer, H.G
Combining Solar Irradiance Measurements and Various Satellite-Derived Products to a Site-Specific Best Estimate', Proceedings of the 14th biennial SolarPACES Symposium, Las Vegas, NE (USA), 04.03.-07.03.2008
Evaluation of a new model to calculate direct normal irradiance based on satellite images of Meteosat Second Generation
2008 - Posted: 12/8/2011
By: A. Kemper, E. Lorenz, A. Hammer and D. Heinemann
We present a method to derive the direct normal irradiance DNI from MSG data. For this we apply the Heliosat method to extract cloudiness from the satellite images. Clouds are causing high fluctuations in the DNI. A new model for the direct fraction of the irradiance is introduced to calculate DNI. The clear sky irradiance is mainly determined by the aerosol optical depth (AOD) and water vapour content, which are taken from suitable climatologies. The accuracy of satellite derived DNI data is analyzed here for Spanish sites.

Subtask C-2: Climatological and Interannual Variability of Solar Resources

Trends in Global Radiation Between 1950 and 2100
September 2010 - PDF 0.34MB - Posted: 8/16/2011
By: Jan Remund and Stefan C. Müller
This analysis is based on long time series of global radiation with a duration of at least 40 years and the forecasts of global radiation till 2100, based on results of IPCC [1]. For the mean and most of the individual 25 examined sites the dimming for the period 1950 – 85 and the brightening [2, 3] for the period 1985 – 2009 is statistically significant. The negative trend during the dimming period is clearly stronger (approx. factor 2) than the positive trend during the brightening phase. The individual regions and groups of measurement sites show a great variety of different trends for the analyzed sub periods. The variation depending on the duration of measurement is also quite different from site to site. Most sites have a standard deviation of 5 – 7% for a 12 month mean which goes down to 2-4% at 10 years and 2% at 20 years. The biggest decline happens in the first years.
Trends in Global Radiation Between 1950 and 2100

Subtask C-3: Solar Resource Forecasting

Solarleistungsvorhersage zur Netzintegration von Solarstrom
German
2009 - PDF 0.12MB - Posted: 12/8/2011
By: Elke Lorenz, Johannes Hurka, Detlev Heinemann, Hans Georg Beyer, Martin Schneider
Der steigende Anteil von Strom aus Photovoltaikanlagen lässt Solarleistungsvorhersagen für eine wirtschaftlich und technisch effiziente Einbindung der fluktuierenden Einspeisung immer wichtiger werden.
Weiterentwicklung von Verfahren zur Solarleistungsvorhersage - Prognose von Verbundleistungen und deren Vertrauensbereiche
German
2008 - PDF 0.46MB - Posted: 12/8/2011
By: Elke Lorenz, Johannes Hurka, Detlev Heinemann, Hans Georg Beyer, Martin Schneider
Die zeitliche und räumliche Variabilität der Einstrahlung und die daraus resultierenden Fluktuationen der nutzbaren Energie stellen für die Einbindung von Solarenergie in das bestehende Energieversorgungsnetz eine besondere Herausforderung dar. Bei steigender PV-Netzdurchdringung ist zu erwarten, dass - analog zur Entwicklung auf dem Gebiet der Windenergieeinspeisung – eine verlässliche Solarleistungsprognose für das Netz- und Erzeugungsmanagement unabdingbar sein wird.
Weiterentwicklung von Verfahren zur Solarleistungsvorhersage: Prognose von Verbundleistungen und deren Vertrauensbereiche - Poster
German
2008 - PDF 3.14MB - Posted: 12/8/2011
By: E. Lorenz, J. Hurka, D. Heinemann, H.G. Beyer, M. Schneider
Eine verlässliche Solarleistungsprognose wird mit steigender PV-Netzdurchdringung für das Netz- und Erzeugungsmanagement immer wichtiger. Wir stellen einen verbesserten Ansatz zur Strahlungsvorhersage vor und gehen dabei insbesondere auf die Vorhersagequalität von Verbundleistungen und die Bestimmung von Vetrauensintervallen ein.
Weiterentwicklung von Verfahren zur Solarleistungsvorhersage: Prognose von Verbundleistungen und deren Vertrauensbereiche - Poster
Qualified Forecast of Ensemble Power Production by Spatially Dispersed Grid-connected PV Systems
2007 - PDF 0.34MB - Posted: 12/8/2011
By: Elke Lorenz, Johannes Hurka, Giota Karampela, Detlev Heinemann, Hans Georg Beyer, Martin Schneider°
The contribution of power production by Photovoltaic (PV) systems to the electricity supply is constantly increasing. An efficient use of the fluctuating solar power production will highly benefit from forecast information on the expected power production. This forecast information is necessary for the management of the electricity grids and for energy trading.
Solarleistungsvorhersage f ¨ur die Netzintegration von verteilten Photovoltaikanlagen
German
2007 - PDF 0.25MB - Posted: 12/8/2011
Die zeitliche und r¨aumliche Variabilit¨at der Einstrahlung und die daraus resultierenden Fluktuationen der nutzbaren Energie stellen f¨ur die Einbindung von Solarenergie in das bestehende Energieversorgungsnetz eine besondere Herausforderung dar. Eine Vorhersage der erwarteten Leistung erm¨oglicht eine an die schwankende Energieproduktion angepasste Steuerung von Systemen mit einem hohen Anteil an Solarenergie und kann so zu einer effizienten und wirtschaftlichen Nutzung von Solarenergie beitragen.
Validierung und Optimierung eines Solarstromprognosesystems unter Berücksichtigung von Ensemble-Effekten
German
2007 - PDF 0.58MB - Posted: 12/8/2011
By: Stefan Bofinger, Hans Georg Beyer, Elke Lorenz, Hashini Wikramarathne
Photovoltaik liefert im Sommer schon einen nennenswerten, und beständig wachsenden Beitrag zur Stromversorgung. Um diese Einspeisung möglichst effizient zur Netzregelung einsetzten zu können, ist ein Solarstromprognosesystem in Entwicklung.
Benchmarking of Different Approaches to Forecast Solar Irradiance - Poster
PDF 0.34MB - Posted: 12/8/2011
By: Elke Lorenz, Jan Remund, Stefan C. Müller, Wolfgang Traunmüller, Gerald Steinmaurer, David Pozo, José Antonio, Ruiz-Arias, Vicente Lara Fanego, Lourdes Ramirez, Martin Gaston Romeo, Christian Kurz, Luis Martin Pomares, Carlos Geijo Guerrero
Power generation from photovoltaic systems is highly variable due to its dependence on meteorological conditions. An efficient use of this fluctuating energy source requires reliable forecast information for management and operation strategies. Due to the strong increase of solar power generation the prediction of solar yields becomes more and more important. As a consequence, in the last years various research organisations and companies have developed different methods to forecast irradiance as a basis for respective power forecasts. For the end-users of these forecasts it is important that standardized methodology is used when presenting results on the accuracy of a prediction model in order to get a clear idea on the advantages of a specific approach.
Benchmarking of Different Approaches to Forecast Solar Irradiance - Poster
Advances in Radiation Forecast Based on Regional Weather Models MM5 and WRF
PDF 0.09MB - Posted: 8/16/2011
By: Stefan C. Müller, Jan Remund
With growing installations of solar power plants and integration into the electricity grid there is a demand for forecasting the energy production on a short-term basis for the entire electricity Management. Within IEA SHC Task 36, which ran from mid 2005 until mid 2011, METEOTEST made tests in the Alpine region with its operational numerical weather forecast models to forecast hourly global radiation of the next 72 hours or three days. With the regional weather models MM5 and WRF, setups with different horizontal resolutions were tested. Forecast data series were validated at Swiss measurement sites from the national meteorological network for each forecasted day separately. The first tests analyzed only the direct model output while at project end statistical post-processing methods were applied. In order to have comparable datasets only periods of more than 6 months are shown. As a measure for the quality of the forecast the root mean square error (RMSE) was chosen. Improvements in setups and post-processing techniques resulted in lowering the relative RMSE from 55% to 41% on hourly global radiation. With relatively low effort significant enhancements are possible.
Advances in Radiation Forecast Based on Regional Weather Models MM5 and WRF
Comparison of Solar Radiation Forecasts for the USA
PDF 0.06MB - Posted: 8/16/2011
By: J. Remund, R. Perez and E. Lorenz
Global radiation short time forecast of three different models (ECMWF, NDFD and GFS/WRF) have been compared. The comparison was made for a half year period (summer 2007) at three different climates in the USA. ECMWF shows the best results, followed by NDFD and GFS/WRF. Uncertainty varies strongly from place to place. At Desert Rock NV all models have an uncertainty of 18%. The biggest uncertainty is seen with GFS/WRF model at Boulder CO (50%). The breakeven with persistence is reached after 2-3 hours. Distributions of hourly values do differ from measured values, but are quite similar to global radiation data based on satellite data.
Comparison of Solar Radiation Forecasts for the USA
Benchmarking of Different Approaches to Forecast Solar Irradiance
PDF 0.33MB - Posted: 8/16/2011
By: Elke Lorenz, Jan Remund, Stefan C. Müller, Wolfgang Traunmüller, Gerald Steinmaurer, David Pozo, José Antonio
Power generation from photovoltaic systems is highly variable due to its dependence on meteorological conditions. An efficient use of this fluctuating energy source requires reliable forecast information for management and operation strategies. Due to the strong increase of solar power generation the prediction of solar yields becomes more and more important. As a consequence, in the last years various research organisations and companies have developed different methods to forecast irradiance as a basis for respective power forecasts. For the end-users of these forecasts it is important that standardized methodology is used when presenting results on the accuracy of a prediction model in order to get a clear idea on the advantages of a specific approach.

In this paper we introduce a benchmarking procedure to asses the accuracy of irradiance forecasts and compare different approaches of forecasting. The evaluation shows a strong dependence of the forecast accuracy on the climatic conditions. For Central European stations the relative rmse ranges from 40 % to 60 %, for Spanish stations relative rmse values are in the range of 20 % to 35 %.
Benchmarking of Different Approaches to Forecast Solar Irradiance

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