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Solar eclipse causes high magnitude fluctuations in the Surface Solar Irradiance (SSI) for a short duration and consequently reduces the output of solar PV systems. Grid operators try to estimate the impending loss in PV power generation prior to the occurrence of an eclipse in order to schedule conventional generators for compensating the loss. The worldwide installed capacity of grid connected solar PV systems is expected to steeply rise in the coming decade as a result of the various policy initiatives aimed to tackle the climate change. In future electric supply networks with a high penetration of solar PV systems, such large ramps in generation could impact the stability of the network. Although a solar eclipse is a purely deterministic phenomenon, it’s impact on the satellite retrieval of Surface Solar Irradiance (SSI) is complicated due to the possibility of cloud presence in the regions affected by the eclipse. The extraterrestrial solar irradiance is reduced by the moon during an eclipse. On the one hand this causes clouds to appear darker and they get assigned lower reflectance values than they should have in reality. This leads to predicting higher values for the solar irradiance under these clouds than expected. On the other hand, the eclipse also reduces the clear sky irradiance reaching the earth surface. We developed a method to make corrections for both of these effects on the High Resolution Visible (HRV) channel images from Meteosat-11 The results are validated against ground measurements of irradiance provided by BSRN, IEA-PVPS, DTN and the National Weather Services networks. The validation is performed for sites with locations across Europe and for the last two eclipses.

Cloud Motion Vector (CMV) estimation from consecutive satellite images is widely used commercially for providing hours-ahead intraday forecasts of solar irradiance and PV power production. The modelling assumptions in these methods are generally satisfied for advective motion which is common in mid-latitudes, but strained for tropical meteorological conditions dominated by convective clouds. The region under analysis in this study encompasses both tropical and sub-tropical climatic zones and is affected by seasonal strong convection, i.e., the South Asian Monsoon. The purpose of this study is to benchmark the monthly forecast error of three commonly used CMV estimation techniques - Block-match, Farnebäck (Optical flow) and TV-L1 (Optical flow), for analysing their performance on a seasonal basis. The main focus of this work is the analysis of the limitations of image processing based Block-match and Optical flow techniques in predicting irradiance during the Monsoon period, which presents frequent convective formation and dissipation. Forecasted Cloud Index (CI) maps are validated against reference analysis CI maps for the period 2018-2019 for forecast lead times from 0 to 5.5 hours ahead using the Peak Signal to Noise Ratio (PSNR) metric for estimating the accuracy. Persistence of analysis cloud index maps are used as the reference worst case scenario forecast. Site-level forecasts of irradiance for the same period are validated against ground measured irradiance from two BSRN stations - Gurgaon and Tiruvallur, located in Northern and Southern India respectively. From the Winter period in March to the Monsoon period in August, there is a marked reduction of the 30 minutes ahead forecast accuracy by 3 dB in terms of Peak Signal to Noise Ratio at the image-wide level. This can be observed for all the three methods and the worst-case persistence scenario. Both optical flow methods outperform Block-match by 0.5 dB for the entire period of analysis. The Gurgaon BSRN site is affected by Summer Monsoon and shows an increase in nRMSE by a factor of 3 for all the methods. This station shows a seasonal pattern of forecast error closely matching the image-wide forecast accuracy. The forecast error for the Tiruvallur BSRN station on the other hand reaches its peak in December (Data for October and November are absent), due to its location in the Winter Monsoon climatic zone. Again, the nRMSE for all methods increase by a factor of almost 3 from March to December. The inter-method difference in accuracy is not significant and a seasonal difference (20% nRMSE) dominates. This highlights the shortcomings of image processing techniques in extrapolating future cloud locations under convective situations, where there is rapid change in cloud content between consecutive images.

37th European Photovoltaic Solar Energy Conference and Exhibition; 1311-1316, The main goal of the present work is to study the sensitivity of shading calculations under a „realistic“ (quasi-continuous) radiance distribution model, as opposed to the „standard“ isotropic assumption. We are interested in the balance between the possible accuracy improvements vs the increased computational expense, assuming the shading calculation is coupled with an accurate electrical mismatch model and applied to large-scale PV systems. Two existing PV plants are modeled under three scenarios: (a) an isotropic 3D view-factor (b) a three-component model (with a horizon-brightening band); and (c) a continuous radiance distribution function modeled as a detailed (43 element) sky-tessellation. To estimate a metric of the sensitivity of the model, a cross comparison of numerical results for a small set of virtual PV plants with diverse configurations and climatic conditions is performed. Finally, indirect validation of the model is attempted by comparison of the simulation output to plant monitoring data, but the data quality and resolution turn out to be completely insufficient to reflect the subtlety of the diffuse shading effect.

Diese Arbeit vergleicht mittels der stationären Verweildauer (VWD) die Antipsychotika erster und zweiter Generation (FGAs, SGAs). Es wurde nachgewiesen, dass FGAs gegenüber den SGAs nicht unterlegen sind, sodass in Übereinstimmung mit internationalen Behandlungsleitlinien die ausschließliche Empfehlung von SGAs zur Akutbehandlung schizophrener Psychosen kritisch zu sehen ist. Die vorliegende Untersuchung legt nahe, den in Leitlinien nicht empfohlenen Wechsel auf FGAs in weiteren Studien zu prüfen. The present work compares first and second generation antipsychotics (FGAs, SGAs) using their influence on the duration of hospital stay (DOS). Regarding the DOS, FGAs are not inferior to SGAs. Thus - according to international guidelines - a clear recommendation of SGAs is questionable. Further research seems necessary to improve the data regarding antipsychotic switchovers to FGAs in the treatment of acute schizophrenic psychosis, which is not recommended in current guidelines.

Viele Anwendungsbereiche der Solarenergie und der Tageslichtnutzung in Gebäuden erfordern räumlich und zeitlich hochaufgelöste Einstrahlungsdaten. Das Ziel dieser Arbeit besteht in der Ableitung solch hochaufgelöster Einstrahlungsdaten aus Meteosat-Aufnahmen. Zu diesem Zweck wird die Heliosat-Methode verwendet, ein statistisches Verfahren zur Berechnung der Globalstrahlung aus Satellitendaten. Diese Methode wird um die Modellierung der Diffusstrahlung erweitert und darüberhinaus in zwei wesentlichen Bereichen verbessert: Zur Normierung des Satellitensignals wird das Rückstreusignal der Atmosphäre in Abhängigkeit von der Sonnen- und Satellitenposition erfasst. Zur Bestimmung der Globalstrahlung wird ein Clearsky-Modell eingesetzt, das die Trübung der Atmosphäre berücksichtigt. Die Untersuchung der Genauigkeit der vorgestellten Methode bildet den Schwerpunkt dieser Arbeit.