Subtask A: Standard Qualification of Solar Resource Products

A common structure for the presentation of first-order measures for the quality model (Mean Bias MB and Root Mean Square RMS-deviations) was agreed upon.

Two different procedures for the characterization of second order measures (match of modeled to measured distribution functions) had been applied to various data ensembles. Both methods offer qualitatively similar results. Qualitative ranking of the procedures remains to be done.

The European Solar Radiation Atlas algorithm for computing irradiance on inclined surfaces was implemented as a prototype service in SoDa for application to the HelioClim-1 or –2 databases. It was recently tested against measurements made in PVPS Task 2. Preliminary results show fairly good agreement between measurements and satellite estimates. This agreement is better than observed between measurements and RetScreen outcomes (which exploits ground stations) which is encouraging. Nevertheless, it was concluded that the software should be further checked before performing more detailed analyses.

As a forerunner of the possible outcome of a benchmarking scheme taking end-use accuracy into account, intercomparison applying global horizontal irradiance products from different sources was performed for a selected region in Germany, using data for 2005. The yield of PV-systems in that region was analyzed as an end-use metric. The results were presented at the 21^st European Photovoltaic Solar Energy Conference. [Beyer, H. G., Drews, A., Rindelhardt, U. (2006): 'Irradiance maps applied for the performance assessment of PV systems - a case study for the federal state of Saxony', 21st European Photovoltaic Solar Energy Conference & Exhibition, Dresden, Germany, 04.09. -08.09.2006]

As an example of the analysis of long-term accuracy of satellite-derived irradiance products, a study was performed using 9 years of data from a large number of radiation stations operated by the German weather service. The results have been summarized in an article submitted to Theoretical and Applied Climatolog, [Drews, A., Lorenz, E., Hammer, A. and Heinemann, D.: 'Long-term accuracy assessment of satellite-derived global irradiance time series with respect to solar energy applications'].

Work Planned for 2007

Hochschule Magdeberg (H2M) and CIEMAT will continue comparison of procedures for checking the quality of modeled distribution functions for design a common method.

The application of the proposed measures and schemes will be tested for various data sets, building upon the work on the long-term accuracy started at Oldenburg. Universität Oldenburg, H2M, Meteocontrol and CIEMAT will continue to analyze models for the spectral characteristics of the irradiance. This will include the development of respective measures of model quality, applicable for benchmarking.

Testing irradiance estimates against Task 2 PVPS measurements will be continued. This will cover both the irradiance on inclined surfaces and the resulting energy yield of the PV-systems (Ecole des Mines / Armines, H2M).

NASA/LaRC is making GEWEX Radiative Flux Assessment datasets available to the Task. These include:

• The intention of making the extended GEBA database available for validation

• The PNNL analysis of BSRN measurements for use in SRKM validation and benchmarking activities

This activity will implement and validate current and new NASA products with agreed upon sets of statistics using common surface radiometer measurements, contributing results to the team for validation in clear and cloudy conditions as a function of location.

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