Annette Hammer

Annette Hammer
DLR Institute of Networked Energy Systems · Energy Systems Analysis

PhD
Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR) German Aerospace Center Institute of Networked Energy Systems

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51
Publications
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1,590
Citations

Publications

Publications (51)
Conference Paper
Atmospheric aerosols have the highest impact on the solar irradiance reaching the surface of the Earth under cloudless conditions. Aerosols scatter and absorb solar irradiance, resulting in an attenuation of the Direct Normal Irradiation (DNI) and an increase in the Diffused Horizontal Irradiation (DHI). Ultimately this causes the total Global Hori...
Conference Paper
Full-text available
Cloud Motion Vector (CMV) estimation from consecutive 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, common in mid-latitudes, but strained for tropical meteorological conditions domin...
Conference Paper
Full-text available
This work explores the general problem of combining an arbitrary set of noisy ground sensor measurements (horizontal, tilted, diffuse, direct, satellite-derived, etc. all for the same point) together with empirical and physical models (separation, transposition, and forecasting), to estimate a discrete set of irradiance components (in the simplest...
Conference Paper
A huge amount of observations (radiometers, ceilometers, sky images, satellites as well as solar plants) are used to derive solar nowcasts as well as the initial state of the atmosphere used by improved numerical weather models. The evolution of which is then predicted by NWP and LES. For solar power prediction, both observations from the ground an...
Conference Paper
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 calculat...
Article
The poor spatial resolution of available ground data provides an opportunity to estimate solar irradiation from computational models based on the satellite data. The developed model employs various spectral bands of the satellite data and focuses on distinguish weather signatures, such as: dust, aerosols, fog, and clouds. These parameters affect th...
Article
Modelling clear-sky index increments (i.e. changes in normalized surface irradiance over specified intervals of time) and their spatial autocorrelation structures is important for the reliable grid integration of photovoltaic power systems. In order to capture increment correlation structures under mixed sky conditions, we apply a fractal cloud mod...
Article
The Faiman model is used to assess the PV module temperature at outdoor conditions for four different module technologies at five test sites with different climates. The model makes use of two parameters which are derived from measurements of the module temperature, plane of array irradiance, ambient temperature, and wind speed following recommenda...
Article
Full-text available
Due to an oversight by the authors, the following correction is necessary in this publication [1].[...]
Article
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The cloud index is a key parameter of the Heliosat method. This method is widely used to calculate solar irradiance on the Earth’s surface from Meteosat visible channel images. Moreover, cloud index images are the basis of short-term forecasting of solar irradiance and photovoltaic power production. For this purpose, cloud motion vectors are derive...
Article
A detailed estimation of the expected yield from photovoltaic systems requires not only broadband solar irradiance but as well its spectral distribution. The SOLIS method to calculate spectrally resolved irradiance from satellite data is presented here. It is evaluated in two ways: using radiative transfer calculations and measurements of spectrall...
Article
Satellite images are heavily used for the estimation of solar irradiation at the Earth’s surface. The accuracy yet should be improved to attain more reliable input values for the use of all types of solar energy systems. This paper presents two new alternative approaches to increase the estimation accuracy of daily solar irradiation by coupling the...
Article
Full-text available
Accurate solar surface irradiance data is a prerequisite for an efficient planning and operation of solar energy systems. Further, it is essential for climate monitoring and analysis. Recently, the demand on information about spectrally resolved solar surface irradiance has grown. As surface measurements are rare, satellite derived information with...
Article
Full-text available
The use of satellite measurements for the estimation of solar irradiation at the Earth surface is rapidly increased in the 21st century. The accuracy of such estimations yet should be modified to attain more reliable input values for the use of all types of solar energy systems. This paper presents a new alternative approach aiming to increase the...
Conference Paper
Full-text available
The varying spectral distribution of the terrestrial irradiance can cause significant differences between the actual and the rated efficiency of solar cells. To account for this effect it is necessary to calculate the weighted irradiance which depends on the solar cell spectral response and on the spectral distribution of the irradiance. Because gr...
Article
Full-text available
The paper gives recommendations to reach high quality, traceable and reproducible yield prognosis for solar thermal power plants. The whole process chain from solar resources to simulation is evaluated to identify main error sources. Three main fields are identified, which have significant impact on accuracy of potential electricity yields: Firstly...
Chapter
The specific characteristics of solar energy production make the meteorological knowledge on solar radiation to a product of increasing importance. Assessing information on the available resources to describe the potential of energy production, providing historical up to near-real-time data on various spatial scales to support a most efficient use...
Conference Paper
Full-text available
Energy yields of concentrating solar thermal power plants depend strongly on the availability of beam irradiance. Direct solar irradiance is highly variable in space and time and thus, requires in-depth analysis of measurements with high quality, well tracked calibrations and approved quality control to achieve reliable results. Strong vari-ability...
Article
Full-text available
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 t...
Conference Paper
Full-text available
1. Einführung Für die Planung und den Betrieb von PV-Anlagen in Brasilien ist aufgrund des dünneren Strahlungsmessnetzes der Einsatz von flächendeckenderen satellitenge- stützten Einstrahlungsinformationen sinnvoll. Zur Demonstration dieses Einsatzes zeigen wir die Nutzung der aus Aufnahmen des Meteosat-Satelliten abgeleiteten Ein- strahlungsdaten...
Article
Full-text available
Forecasting of solar irradiance will become a major issue in the future integration of solar energy resources into existing energy supply structures. Fluctuations of solar irradiance have a significant influence on electric power generation by solar energy systems. An efficient use of solar energy conversion processes has to account for this behavi...
Conference Paper
Full-text available
A Web service has been developed for answering the needs of industry and research for information on solar radiation parameters with a satisfactory quality. It intends to solve the three major problems identified by customers: i) improving access to information, ii) improving knowledge on space and time structure and iii) improving matching of deli...
Article
About 20% of the final energy consumed in Europe is used in buildings. The active and passive use of solar energy is an approach to reduce the fossil energy consumption and the greenhouse gas emissions originated by buildings. Consideration of solar energy technologies in urban planning demands accurate information of the available solar resources....
Conference Paper
Full-text available
1-University of Oldenburg, 2-University of Appl. Sciences Magdeburg, 3-Ecole des Mines de Paris, 4-University of Bergen, 5-Ecole Nationale des Travaux Publics de l'Etat, 6-University of Geneva, 7-Instituto Tecnologico de Canarias, 8-Fraunhofer Institute for Solar Energy Systems, 9-German Aerospace Center Geostationary satellites such as Meteosat pr...
Article
Full-text available
The project SoDa (solar data) answers the needs of industry and research for information on solar radiation parameters with a satisfactory quality. The methodology is user-driven with a large involvement of users in the project, who gauge the progresses and achievements. A prototype service has been developed, using Internet technology, that integr...
Article
Forecasting of solar irradiance will become a major issue in the future integration of solar energy resources into existing energy supply structures. As far as short-term time horizons (up to 2h) are concerned, satellite data are a high quality source for information about radiation with excellent temporal and spatial resolution. Due to the strong...
Conference Paper
Full-text available
Solar energy technologies such as photovoltaics, solar thermal power plants, passive solar heating/cooling systems and day lighting in buildings are expected to continue their very rapid growth. In this context the availability of reliable solar radiation data is of high economic value both for planning and operating these systems. HELIOSAT-3 aims...
Conference Paper
Full-text available
In this paper, we describe a surveillance procedure for grid connected photovoltaic (PV) systems. The site specific solar irradiation data will be derived from satellite images rather than from ground based measure-ments. No additional hardware installation will be necessary on site. On the basis of hourly irradiance time series, monthly values of...
Article
Satellite data have significantly improved the availability of solar radiation data with high spatial and temporal resolution for design, operation and performance analysis of solar energy systems. The basic concept of an operational method for the estimation of surface solar irradiance which is independent on ground truth data is outlined. The met...
Article
Short-term forecasting of solar irradiance is an important issue for many fields of solar energy applications. As the solar surface irradiance can be inferred from satellite measurements with a high temporal and spatial resolution, we use satellite images as a data source for forecasting. The satellite data provide information on cloudiness, the mo...
Article
Hourly images registered by the Meteosat satellite are used to derive the global irradiance at ground level. Keeping almost the full spatial information of the original images, maps of irradiance characteristics for Africa are derived with a resolution of approx. 10 × 10 km2. Monthly irradiance conditions are characterized by means and standard dev...
Article
A method for the analysis of small scale, short term characteristics of radiations fields under intermediate sky conditions (clouds of cumulus type) is described. It is based on the extraction of cloud field strutures from sky photographs. The cloud structures are described as fractal objects. Based on this representation a procedure for the genera...
Article
Full-text available
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 sate...
Article
Dateiformat: zip, Dateien im PDF-Format. Oldenburg, Universiẗat, Diss., 2000. Computerdatei im Fernzugriff.

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Project (1)
Project
I am interested in spatial and temporal variability of solar irradiance. This topic can be studied with sky imagers, satellite data or distributed ground based sensors .