Tanja Behrendt’s research while affiliated with Carl von Ossietzky University of Oldenburg and other places

Wie lassen sich PBL-Konzepte erfolgreich in Programmen der wissenschaftlichen Weiterbildung im MINT-Bereich realisieren? Im Rahmen der Bildungsallianz mint.online werden berufsbegleitende Studienprogramme und Zertifikatskurse für die MINT-Fachdisziplinen entwickelt. Sie zielen auf eine schnelle Integration aktueller Forschungsergebnisse, eine zielgruppenadäquate Entwicklung von Curricula und sollen den besonderen Ansprüchen heterogener Studierender Rechnung tragen. Neben der organisationalen Verankerung zeigen drei Programme der Bildungsallianz die Vielfalt und die Herausforderungen der PBL-Methoden auf. 13.05.2016 | Marlen Arnold, Thomas Poppinga, Christian Schöne, Tanja Behrendt, Herena Torio, Kathrin Wetzel (Oldenburg) & Telsche Nielsen-Lange (Bremerhaven)

In laboratory higher education critical evaluation and assessment of obtained data and the implemented measurement procedures are addressed. Typically, to foster this reflection process laboratory reports are requested. Such written assignments are usually carried out individually or by reduced groups of students, therefore more focused on the individual evaluation of one's own experimental experience, than on sharing the results of such evaluation with other students. Sharing results and expectations for a given experiment in a transparent way with one another may help identifying sources of error more easily. But above all it may help sharing their knowledge and the insight they gained from the experiments, thereby facilitating the achievement of a more complete assessment and set of conclusions obtained. To foster such a participation process the Introductory Laboratory of the Postgraduate Program Renewable Energy and the European Master in Renewable Energy at the University of Oldenburg which usually consisted of theoretical lectures, laboratory days and evaluation sessions was extended in autumn 2015 by a " Seminar Blog " a WordPress based collective e-portfolio concept, which makes it possible to depict rising questions, steps and results of a research process. Collective-shared representations function as a gateway for discussions and feedback-activities. The dynamically mapping and representation of the research and learning process open ways of prompt and 'timely' communication about questions and uncertainties. In this paper results from the implementation of the " Seminar Blog " as an online tool for enabling the direct and transparent share of experimental results are discussed.

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 spectrally resolved global horizontal, global tilted and direct normal irradiance. The applicability of the SOLIS spectral irradiance to simulate the spectral effect for different photovoltaic materials is tested by calculating the spectral mismatch and the weighted irradiance at three sites using two different inputs: satellite-derived and measured irradiance. The results are compared to measurements of the short circuit current for various photovoltaic materials. Spectral measurements result in a spectral effect on the yield in the range of 2–6% for amorphous silicon and 1–4% for polycrystalline silicon which is reproduced by the SOLIS method. The differences between various sites under investigation due to weather conditions and inclination of the measurements are by tendency well described by the satellite-derived spectral irradiance with SOLIS. However, the results differ from the results using measurements of the short circuit current which are superimposed by other effects.

One remote sensing and two in-situ methods for quantifying the spectral distribution of the direct normal irradiance and its impact on multi-junction solar cells are compared for three different sites in Southern Europe, on the Arabian Peninsula and in the South West of the USA. For each method, the uncertainty is assessed. The spectral parameter Z is used to quantify the differences between the methods.

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 high accuracy might fill this gap. This paper describes a new approach for the retrieval of spectrally resolved solar surface irradiance from satellite data. The method combines a eigenvector-hybrid look-up table approach for the clear sky case with satellite derived cloud transmission (Heliosat method). The eigenvector LUT approach is already used to retrieve the broadband solar surface irradiance of data sets provided by the Climate Monitoring Satellite Application Facility (CM-SAF). This paper describes the extension of this approach to wavelength bands and the combination with spectrally resolved cloud transmission values derived with radiative transfer corrections of the broadband cloud transmission. Thus, the new approach is based on radiative transfer modeling and enables the use of extended information about the atmospheric state, among others, to resolve the effect of water vapor and ozone absorption bands. The method is validated with spectrally resolved measurements from two sites in Europe and by comparison with radiative transfer calculations. The validation results demonstrate the ability of the method to retrieve accurate spectrally resolved irradiance from satellites. The accuracy is in the range of the uncertainty of surface Remote Sens. 2012, 4 623 measurements, with exception of the UV and NIR (≥ 1200 nm) part of the spectrum, where higher deviations occur.

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 ground based spectral measurements are sparse, satellite based spectral data can provide a good alternative. In this work we have compared two approaches. The SOLIS method can calculate both broadband and spectrally resolved terrestrial solar irradiance from satellite data. The clear sky module of SOLIS is based on a partial parametrisation of radiative transfer calculations, and uses atmospheric data from climatologies or satellite based methods. The cloud module is based on empirical relationships between the cloud albedo values determined from Meteosat visual channels and the cloud transmittance. In parallel we developed a simpler empirical method, that can be more easily implemented in photovoltaic modelling software. It is based on principal component analysis of measured spectrally resolved irradiance and empirical relationships between the principal components and satellite derived clear sky index and sun elevation. Both methods have been validated using the same ground measured data from Stuttgart Germany. The weighted irradiance has been used as metrics to compare the results of the models. It was found that the use of both models gave a significant improvement compared to the use of a constant AM1.5 spectrum. The use of the empirical model resulted in lower bias values, the use of SOLIS resulted in lower RMSE values.

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 of solar energy conversion systems, and solar radiation forecast for electricity grid management are only a few topics of the research field-energy meteorology. Besides the basics of measuring the different quantities of solar radiation as global, direct, diffuse, and spectral irradiance by ground-based instruments and satellite radiometers, a focus is set on the refinement of these data by model approaches to provide ready-to-use information. Furthermore, the utilization of these data in problems and questions on variousapplications that help to integrate solar energy into the mix of tomorrow's energy supply is addressed and recent research results are presented.