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Das Spektrum des Handelns von Schulleitung und Schulaufsicht als pädagogische Führungskräfte im schulischen Personalmanagement ist vielschichtig, kann mehrebenenanalytisch betrachtet werden, ist direkt und indirekt: Zum einen qualifizieren sich pädagogische Führungskräfte selbst weiter und zum anderen initiieren, begleiten und unterstützen sie die Gewinnung und Professionalisierung von schulischen Akteur*innen bzw. Nachwuchsführungskräften. Ausgerichtet ist schulisches Personalmanagement auf die Sicherung und Weiterentwicklung der Qualität pädagogischer Arbeit. In dieser doppelten Perspektive wird über ein Kooperationsprojekt der Stiftung der Deutschen Wirtschaft (sdw), der Robert Bosch Stiftung (RBS) und des Instituts für Bildungsmanagement und Bildungsökonomie (IBB) der Pädagogischen Hochschule Zug/Schweiz berichtet, das impulsgebend sein könnte für eine schulische Führungskräfteentwicklung als systematischer und kontinuierlicher berufsphasenübergreifender Prozess, der in der Lehrer*innenbildung beginnen sollte. (DIPF/Orig.), Being educational leaders in the school system, the scope of action of school leadership and school administration concerning human resource management is multi-layered, can be analyzed from a multi-level perspective, is direct and indirect: On the one hand, educational leaders care for their own professional development, and on the other hand they initiate, accompany, and support the recruitment and professionalization of school actors or teachers aspiring leadership. Human resource management within the school system is aimed at ensuring and further developing the quality of educational work. Along this double perspective, this paper focuses on a cooperation project of the Foundation of the German Economy (sdw), the Robert Bosch Foundation (RBS) and the Institute for the Management and Economics of Education (IBB) at the University of Teacher Education Zug (PH Zug), Switzerland, which could give impulses for school leadership development as a systematic and continuous process. (DIPF/Orig.)

Gegenstand des Berichts sind die aktuell in Frankreich geltenden Verfahren für die Rekrutierung und Qualifizierung von Schulleiter*innen der Sekundarschulformen collège und lycée. Dargestellt werden das Zulassungs- und Auswahlverfahren (concours) für die spezielle Qualifizierung, der Qualifizierungsverlauf und verschiedene Möglichkeiten für die weitere Karriereplanung und Profilentwicklung. Ziel des Berichts ist es, verständlich zu machen, weshalb Lehrkräfte wie auch Personen aus bestimmten anderen Berufsfeldern sich für eine Schulleitungsstelle interessieren und qualifizieren und welche weiteren Optionen sie damit verbinden. (DIPF/Orig.), The article deals with current recruitment and qualification procedures of headteachers for the secondary school forms collège and lycée in France. The admission and selection procedure (concours) for the special qualification, the qualification process, and different possibilities for further career planning and profile development are presented. The aim of the report is to clarify why teachers as well as people from certain other professional fields are interested in and choose to qualify for a school leadership position and which further options they associate with it. (DIPF/Orig.)

The objective of this work is to quantify de degradation originated by UV radiation and temperature in silvered-glass reflectors exposed in three locations with high solar irradiance and to replicate the degradation mechanisms observed in outdoors through accelerated aging tests.

Parabolic trough (solar) collectors (PTCs) are technical devices to collect the energy in the form of solar radiation and convert it typically into thermal energy at temperature ranges of 150-500°C at industrial scale. The cylindrical trough shape of the reflecting surface with parabolic section of the mirror shape has the ability to concentrate the incident sunlight onto an absorber tube in the focal line of the collectors. Typical width of such PTC is 0.5-10 m, and the typical concentration factor is in the range of 50-100. The main use of PTC is in solar power generation, but also for process heat in industry. In large-scale concentrating solar power applications, the PTC is the most successful type of concentrating collector design. The first troughs are reported at the end of the nineteenth and beginning of the twentieth century for industrial-scale steam generation. The wide expansion of coal, oil, and gas for heat and power generation left solar energy technology behind until oil price shocks initiated a development step in the 1980s, leading to the successful commercial start of the parabolic trough solar power plants SEGS I-IX in California until 1990. Larger scale capacities have been installed in Spain since 2007, and from there and since then they are spreading out worldwide, in particular in USA, North Africa and Middle East, South Africa and China. PTCs are the main technology for large-scale concentrating solar power (CSP) solar fields. The increasing application in CSP is due to the high conversion efficiency in combination with a standardized modular design with relevant economic advantages over other CSP variants.

Existing buildings often have low energy efficiency standards. For the preparation of retrofits, reliable high-quality data about built-in materials is required. Contactless measuring technologies, especially microwave radar, have the potential to enable an easy-to-apply and automatable way to analyse the structures and thermal properties of existing building walls, but the relationship between materials, their thermal properties, and their electromagnetic properties, such as the permittivity, is needed for its application. This article presents an analysis of the relationship between electromagnetic and thermal properties for a variety of building materials. Systematic measurements were performed for samples (burnt clay bricks, calcium silicate bricks, autoclaved aerated concrete and lightweight concrete) mainly originating from demolished buildings. The thermal conductivity, thermal capacitance, and dielectric permittivity were measured and the hypothesis of a correlation between permittivity and thermal parameters was partly confirmed. This information is a prerequisite for using microwave radar sensing technology to determine heat transfer coefficients of existing building walls. The next research step is the development of a corresponding measurement and evaluation method.

Der Autor beschäftigt sich mit der Frage, welche Methoden die postgraduale Methodenausbildung benötigt. Er warnt vor vorschnellen paradigmatischen Zuordnungen oder Dualitäten im Sinne qualitativ vs. quantitativ. Vielmehr komme es darauf an, paradigmenübergreifende Aspekte zu formulieren, die letztlich die Qualität der Forschung verbürgen. Im Rahmen methodischer Weiterbildung in wissenschaftlichen Qualifizierungsphasen sollte es nicht nur um die einfache Vermittlung von Methoden gehen – so wichtig dies auch ist – sondern genauso darum, eine Diskursfähigkeit zu entwickeln, welche die Nachvollziehbarkeit der wissenschaftlichen Vollzüge für andere offenhält. In der Methodenqualifizierung sollte daran gearbeitet werden, über die Grenzen der selbst genutzten und die Möglichkeiten der von anderen genutzten Methoden nachzudenken. (DIPF/Orig.)

All-sky imager based systems can be used to measure a number of cloud properties. Configurations consisting of two all-sky imagers can be used to derive cloud heights for weather stations, aviation and nowcasting of solar irradiance. One key question for such systems is the optimal distance between the all-sky imagers. This problem has not been studied conclusively in the literature. To the best of our knowledge, no previous in-field study of the optimal camera distance was performed. Also, comprehensive modeling is lacking. Here, we address this question with an in-field study on 93 days using 7 camera distances between 494 m and 2562 m and one specific cloud height estimation approach. We model the findings and draw conclusions for various configurations with different algorithmic methods and camera hardware. The camera distance is found to have a major impact on the accuracy of cloud height determinations. For the used 3 megapixel cameras, cloud heights up to 12,000 m and the used algorithmic approaches, an optimal camera distance of approximately 1500 m is determined. Optimal camera distances can be reduced to less than 1000 m if higher camera resolutions (e.g. 6 megapixel) are deployed. A step-by-step guide to determine the optimal camera distance is provided.

Given the importance that concentrating solar power technologies have had in recent years, the interaction between humid atmospheres in which SO 2 is the main pollutant and the metal reflecting layers of the solar concentrators is a major concern that should be addressed. Previous durability studies have urged the importance of designing an accelerated aging test protocol for simulating aggressive industrial atmospheres that solar reflector materials are bound to encounter. Therefore, three types of reflectors were tested in an acid-rain (or Kesternich) chamber at various temperatures and gas concentrations based on the DIN 50018 and ISO 6988 standards. The results showed the significant effect of high SO 2 concentrations rather than high temperatures on silvered-glass reflectors, although synergy should not be disregarded. Strong reductions in specular reflectance were found for one type of silvered reflector compared to another type, highlighting the significance of material processing and its effects on their final performance. Aluminum reflectors were not damaged as much as silvered-glass reflectors, but under microscopic inspection, a wide range of noticeable corrosion defects could be found in all the materials. Comparisons between the most representative Kesternich test and samples from an outdoor industrial site permitted realistic lifetime correlations for commercial silvered-glass reflectors.

With ramp rate regulations for photovoltaic plants being discussed in many countries, the speed of clouds has gained significant importance lately. Besides, measuring cloud velocities and directions is of interest for validations of numerical weather predictions and solar nowcasting systems. Recently, the Cloud Shadow Speed Sensor (CSS) was developed and validated in San Diego for low cumulus clouds. In this publication, the CSS is studied under different weather and cloud conditions in the desert of Tabernas in southern Spain. Furthermore, a novel shadow camera based low-cost, low-maintenance approach to determine cloud shadow motion vectors is presented and used as a reference to benchmark the CSS. In comparison, the absolute velocities derived from the CSS and the shadow camera on 59 days for ± 5 min temporal medians show deviations of RMSD 2.1 m/s (28.0%), MAD 1.2 m/s (15.7%) and a bias of −0.2 m/s (2.8%). Deviations of the cloud shadow direction are RMSD 47.9° (26.6%), MAD 25.3° (14.0%) and bias 3.7° (2.0%). An adaption of the CSS software yields 91% more measurements on 59 days in comparison to the previously used algorithms at the expense of reduced accuracies, both for the measured velocities and for the measured directions. The CSS and the novel shadow camera based reference system enable long-time, low-maintenance ground measurements of cloud shadow speeds, which were previously not available. The distinct advantages and limitations of the two systems are discussed. In addition to the comparisons between the shadow camera system and the CSS on 59 days, the detection rates of the CSS are classified and measured on 223 days by analyzing CSS radiometer signals. Depending on the shading strength and shading durations, detection rates vary between 3.7% and 21.6%. Furthermore, the basic assumption as well as possible correction approaches of the linear cloud edge – curve fitting method are studied. The CSS was found to be a robust tool with great potential. However, optically thin clouds with diffuse edges pose a challenge and the detection rate leaves room for improvements. The newly developed shadow camera system provides more measurements which scatter less but needs certain geographical requirements. The shadow camera is found to be a feasible validation tool for cloud (shadow) motion vectors.

Various approaches are used to determine direct, sky diffuse, and reflected contributions to the solar irradiance on building surfaces. Among these are ray tracing, pixel counting, and projection and clipping. Projection and clipping is closest to an exact solution but it is often considered as too slow. This paper presents an improved projection and clipping method to determine the direct and the sky diffuse contribution to the irradiance. In a second step a projection and clipping approach is applied to calculate the view factors between building surfaces, so that the reflected contribution can be obtained. The presented approach delivers results which are comparable to those obtained by EnergyPlus in acceptable computation time. This shows that modern building simulation tools can benefit from an approach that applies fewer approximations than common raytracing or pixel counting techniques.

Mentorinnen und Mentoren sind Lernbegleitende an einer wichtigen Stelle: Sie begleiten am sensiblen Übergang, an der Schnittstelle zwischen Hochschule und Schule. Im besten Falle betreuen sie angehende Lehrerinnen und Lehrer so, dass das Wissen und Können beider Orte für diese wirksam werden kann. Ein Team mit Vertreterinnen und Vertretern dreier Universitäten in Mecklenburg-Vorpommern (fünf Fachdidaktiken und Schulpädagogik) entwickelte, mit besonderem Blick für die Vernetzungen aller Ebenen des Lehrens und Lernens, das Lehrkonzept Mentor*innenqualifizierung M-V. Der vorliegende Text bietet erstens Einblicke in das in Form einer Design Based Research Studie über drei Zyklen hinweg entwickelte Lehrkonzept, er referiert zweitens zentrale Designprinzipien für die Entwicklung zukünftiger Qualifizierungsprogramme und entfaltet drittens das im Projektzeitraum entwickelte theoretische Modell des gegenstandsbezogenen Mentoring. (DIPF/Orig.)

Die Intention des vorliegenden Bandes ist es, ein Blitzlicht auf das stetig wachsende Forschungsfeld zu werfen und einen Überblick über aktuelle Forschungstendenzen zu gewinnen. Das Konzept der Lernbegleitung wird in diesem Sinne bewusst in mehrfacher Hinsicht weit gefasst. [...] Während sich einige Beiträge verstärkt auf die Reflexion von Unterricht als das Kerngeschäft des Lehrerinnen- und Lehrerberufs konzentrieren, fokussieren andere auch professionsübergreifende Aspekte wie z.B. das allgemeine Wohlbefinden oder Fragen der beruflichen und persönlichen Selbstfindung. (DIPF/Orig.)

Die Autorinnen diskutieren, inwiefern ein sensibler und reflektierter Umgang von (angehenden) Lehrkräften mit den vielfältigen Heterogenitätsdimensionen von Schüler*innen als grundlegende Voraussetzung für die Gestaltung inklusiven Unterrichts gelten kann. Sie skizzieren, wie die Facetten adaptiver Lehrkompetenz durch das Konstrukt Heterogenitätssensibilität ethisch-normativ fundiert und für eine inklusionssensible Lehrkräftebildung fruchtbar gemacht werden können. (DIPF/Orig.)

Universitäten [...] sehen sich spätestens seit der fluchtbedingten Migration seit 2015 verstärkt mit den Weiterbildungsbedarfen von Menschen mit Fluchthintergrund konfrontiert und sind mitunter dazu gezwungen, sich damit zu beschäftigen. […] In diesem Kapitel wird zunächst auf die Situation geflüchteter Schüler*innen eingegangen, bevor die Situation von Lehrkräften mit Fluchthintergrund dargestellt werden wird. Beide Aspekte sind untrennbar miteinander verwoben: (Pflicht-)Schüler*innen mit Fluchthintergrund werden in das Schul- und Bildungssystem des Ziellandes aufgenommen; geflüchtete Lehrer*innen vermögen dieses durch ihre akademische Bildung und damit einhergehend ihre Expertise, aber auch durch ihre Erfahrung als Lehrende sowie als positiv besetzte Vorbilder sowohl für geflüchtete wie auch aus dem Zielland stammende Schüler*innen zu unterstützen. Im Zentrum steht dabei der Versuch, zu erläutern, welche Bedarfe sich an Schulen und anderen Bildungseinrichtungen durch die Fluchtbewegungen ergeben. Dies soll dazu beitragen, die in den nachfolgenden Kapiteln erörterte Forschung und die daraus resultierende Maßnahme grundlegend zu kontextualisieren. (DIPF/Orig.)

Hochschuldidaktik 4.0 überträgt das in der jüngsten Vergangenheit vielfach implementierte und beforschte Konzept des Flipped Classroom auf Veranstaltungen der Lehrendenqualifizierung. Es soll auch bei der Qualifizierung von Lehrenden eine Möglichkeit aufzeigen, von den positiven Effekten des Konzeptes zu profitieren und mithilfe von drei Phasen eine intensivere Beteiligung und einen stärkeren Austausch unter den Teilnehmenden zu befördern. Der Beitrag beschreibt den Stand der Forschung und bietet einen Einblick in die konzeptionelle Gestalt eines Flipped-Classroom-Modells für die Hochschuldidaktik. Our model for a new course design in the field of Higher Education transfers the widely discussed concept of the Flipped Classroom to the strands of staff development and especially to university teacher training. We will show how lecturers or professors can benefit from the positive effects of an up-to-date training including digital interactive learning settings. Moreover, our model will promote more intensive participation and exchange among the participants along the lines of three sequential phases. The article describes the state of research and offers an insight into the conceptual design of a flipped classroom model for teacher training in the field of higher education.

All sky imager (ASI) based nowcasting system can provide spatially and temporally highly resolved solar irradiance information for the next minutes ahead. Nowcasts, which capture the intra-hour variability of the incoming downward shortwave solar irradiance, have the potential to optimize the operation of solar power plants as well as electrical grids. Such automatized optimizations require a deep understanding of the accuracy in the nowcasting system at any given moment. State of the art validation procedures of ASI based nowcasting systems use scalar error metrics without regards to the actual weather conditions. Yet, the performance of nowcasting systems varies strongly with the prevailing weather conditions. Deviations increase for more complex and variable conditions, for which it is more challenging to detect and model the clouds in the sky. Thus, depending on the used data set such validation results may not be meaningful to describe the expected accuracy in realistic and individual optimization situations. A novel validation procedure is presented in this work, which discretizes the validation data set in distinct temporal DNI variability classes. Individual error metrics are determined as function of the lead time and DNI variability class. This approach is applied for a two ASI based nowcasting system as operated on five distinct sites distributed in Spain, Portugal and Germany, over a combined period of more than 4.5 years. The obtained validation results emphasize that the novel classification method enables a comparison in nowcast performance between the sites despite of distinct local meteorological conditions. The presented method allows the estimation of the overall accuracy of nowcasting systems at a new site if DNI data in 1 min resolution are available.

Heating energy represents a significant proportion of the total energy consumption of theFederal Republic of Germany. Thus, a reduction of heating energy demand in buildings is one of the central points of German energy saving and climate goals. Considering that the current rate of new building construction is approximately 1 %, the most significant energy saving potential lies in existing buildings. The analysis of existing buildings will thus become more important in the years to come. As a result, the development of new measurement systems to assess the need for renovation is required. In this context, detailed Information about heat insulation and airtightness is essential. The current approaches to detect air leakage in building envelopes are mostly time consuming and expensive. Therefore, the development of an advanced and more inexpensive method is a vital step. In this paper, we2 present a study about the feasibility and suitability of ultrasound technology to evaluate the size of air leakages in building envelopes. The advantage of ultrasound technology is that the corresponding wavelengths are small enough to penetrate small openings and that disturbing background noise is usually low. Moreover, the frequencies are above the human threshold of hearing; hence, working and living inside the building would be affected less by the measurement than by a blower door test or leakage detection with audible sound. To examine the suitability of this technology, we use an experimental setup of ultrasound microphones and a speaker in a test chamber. Within this setup, we measured different hole sizes and assessed whether they could be detected using ultrasonic frequency swept signals.

Zusammenfassung Neben den anerkannten dualen Ausbildungsberufen gibt es zahlreiche Berufe, die im Rahmen einer vollzeitschulischen Ausbildung erworben werden konnen. Dieser Beitrag geht der Frage nach, wie der modernisierte zweijahrige doppelqualifizierende Bildungsgang der Berufsfachschule (BFS) „Staatlich geprufte Assistentin/Staatlich geprufter Assistent fur Ernahrung und Versorgung, Schwerpunkt Service“ mit Berufsabschluss nach Landesrecht in NRW inhaltlich strukturiert ist und welchen Nutzen er fur die Absolventinnen und Absolventen sowie zur Sicherung des Fachkraftebedarfs im Berufsfeld Ernahrung und Hauswirtschaft haben kann. Schlusselworter: Berufsfachschule, berufliche und schulische Qualifizierung im Berufsfeld Ernahrung und Hauswirtschaft, Chancenverbesserung, Fachkraftesicherung ----- Bibliographie: Brand, Rita: Struktur und Nutzen einer vollzeitschulischen Ausbildung in einer Berufsfachschule, HiBiFo, 1-2018, S. 54-68. https://doi.org/10.3224/hibifo.v7i1.04

Concentrated solar thermal technologies play an essential role in the energetic transition which is currently facing our society. The energy generation in this technology vastly depends on the optical behaviour of the reflector materials of the solar field. Corrosion of solar reflectors might be an issue in locations with high corrosive environments because an excessive corrosion of the solar mirror could be catastrophic for the profitability of the concentrated solar thermal plant. This research is focusing on modelling the durability of four different solar reflector materials exposed outdoors by accelerated aging tests. For this purpose, ten locations suitable for concentrating solar thermal applications were classified depending on their corrosive aggressiveness. Commercial, free-lead and low-cost reflectors samples were exposed in all the sites to determine the influence of the corrosion in its durability. Corrosion defects appeared in the solar reflectors during outdoor exposure were properly reproduced by CASS test. Novel lifetime prediction models were developed for all the solar reflectors depending on the corrosive aggressiveness of the place. Number and thickness of the paint coatings employed in the solar mirrors were identified as one of the most important parameters to improve the energy generation of a CSP plant in corrosive environments. A reduction of the capital invested in the solar mirror purchase is expected for sites with low corrosivity.

Strong efforts are being made to drive heliostat cost down. These efforts are summarised to give an update on heliostat technology comprising: determination of wind loads, heliostat dimensioning, solutions for the different sub-functions of a heliostat, a review of commercially available and prototype heliostat designs, canting, manufacturing, qualification, heliostat field layout, and mirror cleaning. There is evidence that commercial heliostat costs have dropped significantly in the past few years, with commercial suppliers of heliostat technologies now claiming heliostat field costs around 100 USD/m2. With new approaches even target cost of 75$/m2 seem to be realistic.

The air return ratio is a key factor for the overall efficiency of the open volumetric receiver concept. Although first measurements of the air return ratio exist for smaller setups of the open volumetric receiver concept, so far no measurement of the air return ratio has been presented for the Solar Thermal Test and Demonstration Power Plant Julich ( ≈ 1.5 MW, ≈10 (kg air)/s; ≈700 °C). This paper describes the application of a tracer gas method at the solar tower Julich to determine this substantial ARR. As tracer gas the environmentally friendly helium has been chosen. The helium is injected dynamically into the circular air flow of the system and the helium mole fraction is measured using a mass spectrometer. The dynamic concentration response of the system is used to determine the air return ratio. This dynamic method only requires one location of measurement. First measurements with this dynamic method were conducted at the solar tower Julich. The ARR of STJ was measured with and without irradiation of the main receiver with high accuracy. Under low-wind conditions and without irradiation of the main receiver the air return ratio was measured to be ( 67.7 ± 0.5 ) % for an air mass flow of ( 9.96 ± 0.04 ) kg / s . A slightly higher air return ratio of ( 68.6 ± 0.7 ) % was measured under irradiation with an air mass flow of ( 9.94 ± 0.04 ) kg / s . The air return ratio was sensitive to the air mass flow, showing significantly lower rates when moving further away from the 10 kg / s design air mass flow to 5 kg / s .

Soiling puts operators of solar power plants before the challenge of finding the right strategy for the cleaning of their solar fields. The trade-off between a low cleanliness and thus low revenues on the one hand and elevated cleaning costs and high field efficiency on the other hand has to be met. In this study we address this problem using a reinforced learning algorithm. Reinforced learning is a trial and error based learning process based on a scalar reward. The algorithms improve with an increasing number of training runs, each performed on a different one-year data set. The reward being the profit of the CSP project. In order to prevent overfitting to a special case, the training data has to be sufficiently large. To increase our 5 year soiling-rate and 25 year meteorological measurement data set from CIEMAT’s Plataforma Solar de Almeria (PSA). We first present a method to create artificial long term data sets based on These measurements that are representative of the sites’ weather conditions. With the extended datasets we are able to train the algorithm sufficiently before testing it on the validation dataset. The algorithm is given the daily choice to deploy up to two cleaning units in day and/or night shifts. In a second step, it is given soiling rate forecasts with different forecast horizons. At PSA our trained algorithm can increase a project’s profit by 1.28 % compared to a reference constant cleaning frequency (RPI) if only the current cleanliness of the solar field is known. If it is given a one day soiling-rate forecast the profit can be increased by 1.33 %. A three day soiling-rate-forecast can increase the profit by 1.37 %. An extended forecast horizon does not seem to increase the RPI further. For sites with higher dust loads than PSA the RPI is expected to be significantly higher than at PSA. Reinforced learning in combination with the data extension algorithm can be a useful method to increase a CSP project’s profit over its lifetime.

Concentrating solar thermal technologies have experienced an important boost in the last few years. Besides the production of electricity, they are particularly useful for the supply of industrial process heat. The industrial atmospheres affecting these solar plants typically contain gaseous pollutants that are likely to promote corrosion on the components of the solar facility, specifically solar reflectors, thereby compromising their optimal performance and the overall system efficiency. Seven accelerated aging tests were designed to study the effects of three air pollutants (H2S, SO2 and NO2) on the durability of two commercially available reflector types (silvered glass and aluminum), both in single-gas tests and in multicomponent gas mixtures. Additionally, the same material types were exposed outdoors at five representative polluted sites, including industrial, urban and coastal environments. Reflectance and optical microscope monitoring corroborated which degree of corrosion was developed on a specific type of reflector in the different tests with gaseous pollutants, as well as the synergistic effects of gas combinations. For example, tests with sulfur were harmful for silvered-glass reflectors (up to a total of 16 corrosion spots), whereas aluminum was particularly affected by tests with NO2 (numerous micro spots of around 50 pm size). Moreover, comparisons of the corrosion patterns found in accelerated-aging and outdoor exposures revealed which laboratory test reproduced the different real polluted atmospheres in the most realistic way, which is the main goal of this work. For instance, the degradation found at Site 2 was reproduced by Test NO2+SO2, with an acceleration factor of 27. info:eu-repo/semantics/publishedVersion

Anti-soiling coatings for solar reflectors are one of the most useful technical tools to reduce the amount of soiling accumulated on the reflector surfaces, contributing to reduce the water consumption and to increase efficiency in concentrating solar fields. A new anti-soiling coating formulation based on the hydrophilic effect has been recently developed by Tekniker and Rioglass. Reflector samples with this innovative coating were assessed through an accelerated aging test campaign as well as an outdoor exposition at the PSA by CIEMAT and DLR. According to the results obtained, the coating exhibited an appropriate behavior, which implies that the new product represents a promising solution to reduce water consumption.

This paper focuses on the technology mix proposed for the Diego de Almagro “Solar Technology District” (DTS), intended to be built at the south of the Atacama Desert in Chile, which combines Concentrated Solar Power (CSP) with Photovoltaic (PV) plants to take advantage of both systems attributes: easy installation and low levelized cost of electricity (LCOE) of PV and dispatchability and low cost for storing energy of CSP. Thermal energy storage systems as well as batteries are considered. Local conditions such as solar irradiation, water cost and availability and energy demand profile in Chile are noteworthy and important to be discussed. The methodology followed to optimize the power plant configurations focused on minimizing the LCOE and also considered the available land and the water consumption. Additionally, a rather new PV technology was investigated and selected for the solar park: Bifacial PV modules. The results obtained are useful to project developers seeking for combinations of PV and CSP to satisfy specific electricity demand in an economic, clean and reliable way

Current parabolic trough collector development mainly aims at cost reduction. Within the project ConSol the goal was to reduce material and production costs by using high-performance concrete for the parabola shell itself and also for part of the tracking system. A high amount of manufacturing at the power plant site (“mobile factory”) by delivery of the raw materials and semi-finished products is foreseen, adding value to the local content. Within the project a collector prototype consisting of an extraordinary thin concrete shell was realised based on FEM calculations. The shell is moved via a novel sickle-shaped hill with a newly developed drive system. The collector’s shape was measured by photogrammetry and its optical performance deduced. A part of the ConSol project was dedicated to the improvement of a PVD coated mirror multilayer system on electrochemical polished aluminium strip substrate. With these new layer systems the reflective properties could be increased significantly. Finally, the costs of the system was summarised and cost benchmarks with existing collector Technology.

HELISOL® 5A has been subject to continuous research since 2012. This paper presents at selection of the most relevant test and measurement results gained along the parabolic trough collector application related qualification of this new HTF. HELISOL® 5A successfully demonstrated its loop scale functionality achieving the proof of concept at Plataforma Solar de Almería (PSA) after 480 hours of operation at 425 °C. The degradation processes induced Formation of low boiling and gaseous products is shown for the aging tests in lab environment and for the loop scale application. In terms of operational safety five key investigations are presented. Three of which include the direct comparison with the commonly used mixture of diphenyl oxide and biphenyl (DPO/BP) the wick flame persistence test, the reaction of HELISOL® 5A and DPO/BP with molten salt and the spray ignition test. The other two tests cover the flammability of HELISOL® 5A in contact with hot (475 °C) surfaces and the worst case scenario of a tube rupture at collector level at 420 °C / 17 bar which both don’t lead to ignition of the HTF.

Heat loss testing of parabolic trough receivers with heating cartridge is well-established. In that technique temperature is measured by pressing thermocouples against the inside surface of the absorber tube. As the temperature of the thermocouple is influenced by radiation temperature and air temperature in the annulus, the temperature of the thermocouple is higher than the absorber temperature. The paper presents a measurement of absorber temperature over- prediction as function of heating power between 89 °C and 577 °C for three different insulation configuration yielding over-prediction between 4.4 K and 15.3 K. This shows, that absorber temperature over-prediction is at a relevant order of magnitude for heat loss measurements of parabolic trough receivers. Interpolation using 2nd- and 3rd-order 2d polynomials with the additional condition of disappearing over-prediction at HL=0 for correction of heat loss measurements is demonstrated.

The precise measurement of the reflected energy form a solar reflector to the Receiver is a challenging Task because of ist dependency on three different Parameters: the wavelength of the incident lieght, ist incidence angle and the acceptance angle of the Receiver. Up to today, the commonly empleyed measurement Equipment is not able to fully characterize the mirrors in the required range of Parameters which is relevant for CSP. Within this work, four reflectometers were upgraded to overcome the current drawbacks. A Round Robin test among the different characterization methods has been carried out on four reflector materials. The conclusions drawn from the comparison of the measurement results help to improve the current SolarPACES Reflectance Guideline.

Lifetime prediction methods for the components of concentrated solar power (CSP) plants have been in the focus of interest of manufacturers and plant developers for the past years. Recently, an accelerated aging standard for solar mirrors was published by the Spanish AENOR committee [1]. This standard allows performing comparative testing but it is not suited to derive meaningful life-time estimations. Firstly, the testing defined in the standard is not aggressive enough to produce significant degradation on most of the materials and secondly, it has been shown that the passing of these tests does not guarantee a high durability during outdoor exposure [2]. These findings have proven the need for the investigation of more realistic procedures. To provoke the mechanisms that are detected during outdoor exposure, a more realistic application of environmental stresses is being investigated. In this work a series of tests is conducted in which several weathering stresses are combined and applied in a cyclic manner. Some of these cycles have shown to correlate better with real outdoor behavior. N/A

In Germany, demographic change has had far-reaching effects regarding the education system. Particularly in rural, non-urban areas, the existing netwwork of schools is at risk - most of all, this concerns vocational education and training schools. Even more striking, however, are the consequences regarding the qualification of young people because a generation of "baby boomers" needs to be replaced by a low-birthrate generation while at the same time the labour market demands higher qualification levels. Moreover, a growing number of students are from immigrant backgrounds and/or from disadvantaged families: they represent the potential that would still allow for increases in qualification levels. (DIPF/Orig.)

Zusammenfassung Der folgende Beitrag stellt das Konzept und die Ziele der fachspezifischen Lernbegleitung im Lernzentrum Ernahrung, Konsum und Gesundheit (LEKG) vor, das im Rahmen des Programms „Heterogenitat als Chance“ an der Universitat Paderborn eingerichtet worden ist, zeigt Herausforderungen und Grenzen aus der Praxis auf und diskutiert weitere Perspektiven fur das Studienfach Hauswirtschaft im Institut fur Ernahrung, Konsum und Gesundheit. Schlusselworter: Lernbegleitung, Peer-Learning, Tutorenausbildung ----- Bibliographie: Hellweg, Joanna: Fachspezifische Lernbegleitung durch Peer-Learning im Lernzentrum Ernahrung, Konsum und Gesundheit der Universitat Paderborn, HiBiFo, 4/2015, S. 63-77. http://dx.doi.org/10.3224/hibifo.v4i4.21294

Open Access Journal, In diesem Artikel wird der Frage nachgegangen, was denn eine gute Qualifizierung zum Coach ausmacht. Zuerst werden dazu Anforderungen an Coach und Coaching-Weiterbilder/innen beschrieben und mit den wichtigsten Wirkfaktoren im Coaching in Zusammenhang gestellt. Darauf aufbauend geht es um Anforderungen an die Coaching-Weiterbildungen, um am Schluss der Frage nachzugehen, was denn professionelle Coachs für ihre Weiterqualifizierung brauchen.

Author(s): Walker, Iain; kolsch, benedikt | Abstract: In many countries, the fan pressurization method is the most frequently chosen approach for measuring the air leakage of houses. The measurements are usually performed at pressures that far exceed pressures to which buildings are exposed to under normal conditions. A fit of these tests to the power-law formulation allows an extrapolation to data points outside the measured pressure range. With the Ordinary Least Square (OLS) fitting method, the pressure exponent and flow coefficient can be determined. However, the measurement results are highly sensitive to uncertainties induced by external factors like changing wind conditions during the tests, which is neglected by OLS. This may lead to errors in the prediction of flows at lower pressures. The Weighted Line of Organic Correlation (WLOC) is an alternative approach and takes measurement uncertainty into account. In this paper, a statistical analysis of an extensive data set of pressurization measurements has been performed. Both regression techniques have been compared for almost 7500 fan pressurization measurements of six houses in 109 different house leak configurations. The variability in predicting pressure exponent and flow coefficient for both WLOC and OLS regression was analyzed using probability density functions. It was found that the Weighted Line of Organic Correlation significantly decreases the uncertainty in predicting pressure exponent, flow coefficient, and other low-pressure air leakage metrics compared to the Ordinary Least Square fitting. The authors highly recommend the implementation of WLOC in current measurement standards and test equipment.

A clamp-on measurement system for flexible and accurate fluid temperature measurements for turbulent flows with Reynolds numbers higher than 30,000 is presented in this paper. This noninvasive system can be deployed without interference with the fluid flow while delivering the high accuracies necessary for performance and acceptance testing for power plants in terms of measurement accuracy and position. The system is experimentally validated in the fluid flow of a solar thermal parabolic trough collector test bench, equipped with built-in sensors as reference. Its applicability under industrial conditions is demonstrated at the 50 MWel AndaSol-3 parabolic trough solar power plant in Spain. A function based on large experimental data correcting the temperature gradient between the measured clamp-on sensor and actual fluid temperature is developed, achieving an uncertainty below ±0.7 K (2σ) for fluid temperatures up to 400 °C. In addition, the experimental results are used to validate a numerical model. Based on the results of this model, a general dimensionless correction function for a wider range of application scenarios is derived. The clamp-on system, together with the dimensionless correction function, supports numerous combinations of fluids, pipe materials, insulations, geometries, and operation conditions and should be useful in a variety of industrial applications of the power and chemical industry where temporal noninvasive fluid temperature measurement is needed with good accuracy. The comparison of the general dimensionless correction function with measurement data indicates a measurement uncertainty below 1 K (2σ).

This paper reports experimental results for accelerated ageing test campaigns performed on four different solar receiver coatings applied on T91 and VM12 steel substrates. VM12 tubular samples are exposed at a dish test facility in order to perform thermal cycles under concentrated solar flux. No significant optical degradation could be observed on coated samples after 100 thermal cycles (50 hours at 650 °C), while bare and polished reference substrates oxidized during testing. Three solar receiver coatings achieved a stable solar weighted absorptance αs above 95 % after exposure. A selective coating further showed a thermal emittance of 25 % at 650 °C, instead of 65-75 % for non-selective coatings, thus achieving a thermal efficiency above 90 % at 250 kW/m2, instead of 85 % for non-selective coatings. T91 coated metal coupons were tested in four standard climate test chambers for condensation, damp heat, humidity freeze and neutral salt spray. Two non-selective coatings passed all climate tests without significant optical degradation, while the selective coating did not pass the neutral salt spray test due to severe corrosion.

The solar-thermal parabolic trough power plant Andasol 3 (AS3) near Granada/Spain operated by Marquesado Solar SL (MQS) was commissioned in autumn 2011. The installed capacity of 49.9 MWel in combination with thermal energy storage (TES) capacity for 7.5 hours at full load results in a net annual energy production of more than 165 GWh1 (Dinter and Gonzalez 2014). The German Aerospace Center (DLR) has developed a tool for airborne characterization of entire parabolic trough plants. The approach called QFlySURVEY uses an unmanned aerial vehicle (UAV) equipped with a high resolution digital still camera and delivers effective mirror slope deviation and the absolute orientation of the optical axis of each solar collector element (SCE). In order to validate and demonstrate QFlySURVEY, a comprehensive measurement campaign was undertaken in the AS3 power plant in cooperation with MQS between 2016-10-24 and 2016-11-14. The main objective was to demonstrate the advantages of airborne solar field characterization in terms of rapid data acquisition, negligible interference with plant operation, and without the need of any additional installation of measurement equipment in the solar field. QFlySURVEY provides accurate quantitative measures of optical performance of the solar field and supports the maximization of the thermal energy collected from the solar field by identifying low performing areas and the causes for optical losses.The solar-thermal parabolic trough power plant Andasol 3 (AS3) near Granada/Spain operated by Marquesado Solar SL (MQS) was commissioned in autumn 2011. The installed capacity of 49.9 MWel in combination with thermal energy storage (TES) capacity for 7.5 hours at full load results in a net annual energy production of more than 165 GWh1 (Dinter and Gonzalez 2014). The German Aerospace Center (DLR) has developed a tool for airborne characterization of entire parabolic trough plants. The approach called QFlySURVEY uses an unmanned aerial vehicle (UAV) equipped with a high resolution digital still camera and delivers effective mirror slope deviation and the absolute orientation of the optical axis of each solar collector element (SCE). In order to validate and demonstrate QFlySURVEY, a comprehensive measurement campaign was undertaken in the AS3 power plant in cooperation with MQS between 2016-10-24 and 2016-11-14. The main objective was to demonstrate the advantages of airborne solar field characterization i...

Back-silvered glass mirrors exposed in Abu Dhabi outdoor conditions for 7 years along with corresponding as-received mirrors from the same manufacturing batch which were preserved in a warehouse are analyzed in the present study. The availability of both the as-received mirrors and the exposed ones over a time longer than that in previous studies presents an opportunity to validate accelerated aging tests through comparison with naturally aged mirrors. The exposed mirrors showed substantial reflectance degradation. Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) was used to characterize both as-received and exposed samples and compare the as-received sample to a reference mirror from the state-of-the-art commercial solar mirrors. The analyses identified 5 possible causes of the rapid degradation observed for the mirrors in question in comparison to the lifetime expectation for commercial solar mirrors. The findings will serve to guide ongoing and future accelerated-aging studies on the same mirrors.

Two spectra of solar direct normal irradiance (including circumsolar) are estimated based on spatio-temporal averages of the relevant atmospheric parameters extracted from two different databases: MODIS satellite sensor retriev-als and AERONET sun photometer network. The satellite database is used to calculate an average spectrum for the area of the Atacama Desert. The AERONET database is used for two purposes: (i) to apply bias-removal linear methods to correct the MODIS parameters over Atacama Desert, and (ii) to calculate an average local spectrum for the Paranal station. The SMARTS radiative transfer model is used to obtain the three representative spectra developed in this study. Both the Atacama Desert and Paranal spectra are compared against each other and also to the world reference, ASTM G173. In one of the cases, significant differences are found for short wavelengths. In order to quantify the relative im-portance of these spectral differences, the propagation of errors due to the use of each spectrum is evaluated for CSP applications over the Atacama Desert, considering twelve different scenarios involving the reflectance, transmittance or ab-sorptance of various materials.

Solar reflectors for Concentrating Solar Technologies require a high reflectance in the terrestrial solar spectrum (280–4000 nm). Besides the wavelength, the reflectance of solar mirror materials is also dependent on the incidence angle of the incoming sunlight. The commonly used measurement equipment measures the reflectance at fixed near-normal incidence angles, typically between 8° and 15°. In this work, the annual incidence angle frequency distribution has been calculated for a LS3/Eurotrough-type parabolic-trough collector located at different sites, and for the heliostat field of the solar tower system CESA-1 located at the Plataforma Solar de Almería in Tabernas, southern Spain. It was found that the most frequent incidence angles registered in the solar field are quite higher than the ones at which reflectance is measured with state of the art instruments, obtaining mean incidence angles in the range of 28–35° depending on the type and location of the solar field. A methodology to predict the off-normal reflectance of silvered-glass mirrors based on near-normal reflectance and transmittance measurements of the uncoated glass is presented. The complex refractive index of 2, 4 and 5 mm thick solar glass and the deposited silver was determined and used to model the solar weighted reflectance of silvered-glass mirrors at different incidence angles. The model was compared to experimental measurements. For this purpose, the Spectral Specular Reflectometer (S2R) has been improved and updated with a polarizer crystal to measure reflectance at perpendicular (s-pol) and parallel (p-pol) polarizations up to incidence angles of θ = 70°. Eight solar mirror materials (three silvered-glass mirrors of different glass thicknesses, two anti-soiling coated glass mirrors, two enhanced aluminum reflectors and a silvered polymer film) have been measured over a broad range of incidence angles and the results have been weighted with the annual incidence angle frequency distribution. The obtained incidence angle-weighted reflectance is a suited parameter to compare the efficiency of solar mirror materials taking into account their use in a specific collector type and location. © 2017 Elsevier B.V.

We investigated the forced convective heat loss from a model of a multi-MW cavity receiver of a concentrated solar power (CSP) tower system in a high-pressure wind tunnel. Measurements of 5 geometrical configurations of this model are reported in this contribution. The experiment covered a Reynolds number range of between 2 ⋅ 106 and 8 ⋅ 106, based on the external flow field. The results show that the maximum forced convective heat loss for all configurations occurs when the wind blows from frontal directions of between 60° and 80° relative to the tower symmetry plane. We found that the peak location does not vary for different inclinations, but does vary for different apertures. Also, the results show that the direction of the wind causes the forced convective heat loss to vary with a factor of up to 6.3. Last but not least, we augmented the interpretation of our heat loss measurements with images produced with a Background-oriented Schlieren Imaging (BOS) setup.

Concentrating solar thermal (CST) technologies are a feasible and promising option to tackle worldwide energy problems. These solar facilities are sometimes located near industrial sites, where their main components&mdash, including concentrating solar reflectors&mdash, are prone to significant degradation caused by corrosive agents, especially in the presence of sulfurous atmospheres such as H2S and SO2. This paper focuses on analyzing the influence of sulfurous atmospheres on the durability of reflector materials used in CST technologies. To this end, accelerated aging tests were performed on the most commonly used materials found in solar reflectors (i.e., thick silvered glass and aluminum-based reflectors) by applying the same concentrations of H2S and SO2 under the same conditions of temperature and relative humidity. The results showed that the solar reflectors based on a silver reflective layer are significantly corroded by H2S atmospheres&mdash, several corrosion defects were found in the samples tested. However, those based on aluminum were barely affected by sulfurous environments in the conditions tested. Nonetheless, the study suggests that both reflector types are suitable candidates, depending on the purpose of the CST technology in question and the specific environmental conditions.

This paper presents results from a characterization of DLR’s second generation sun simulator test facility (OptiRec) for determining the optical performance of parabolic trough receivers. The configuration of the test bench is an elliptical mirror trough with flat end mirrors. Solar simulator lamps are situated in one focal line, the receiver in the other focal line. Water at ambient temperature flows through the receiver and allows for a calorimetric measurement of the absorbed power. Compared to the first generation test bench (ElliRec) the mirror material is changed from aluminum to glass, the ellipse size is changed and the handling is improved. Based on 34 measurements of the absorbed power the repeatability for OptiRec measurements is measured to 0.13% (1σ), compared to 0.2% in the ElliRec. Seven receivers from different manufacturers are measured in both test benches yielding consistent relative optical efficiency with

Qualifizierung ist eine zentrale Forderung in der Indust­rie­4.0­-Debatte. Allerdings zeigt sich, dass gering qualifizierte Beschäftig­tengruppen nur begrenzt an Weiter­ildungsmaßnahmen in Betrieben teilnehmen. Eine Fallstudie in einem deutschen Industriebetrieb zeigt, dass dies nicht mit fehlender individueller Motivation zum Lernen zusammen­hängt. Vielmehr führen eingeschliffe­ne Praktiken und Budgetrestriktionen dazu, dass Geringqualifizierte von Vorgesetzten seltener für Weiterbil­ungsmaßnahmen ausgewählt wer­den. Nicht zuletzt aufgrund fehlender Weiterbildungsangebote erleben viele gering qualifizierte Beschäftigte die Einführung der neuen digitalen Tech­nologien im Betrieb als Stress und Überforderung.

International audience; The issue of reflector soiling becomes more important as concentrating solar thermal power plants (CSP) are being implemented at sites subject to high dust loads. In an operational power plant, a trade-off between reducing cleaning costs and cleaning related collector availability on the one hand and keeping the solar field cleanliness (xi (field)) high to minimize soiling induced losses on the other hand must be found. The common yield analysis software packages system advisor model (SAM) and greenius only allow the input of a constant mean xi (field) and constant cleaning costs. This oversimplifies real conditions because soiling is a highly time-dependent parameter and operators might adjust cleaning activities depending on factors such as soiling rate and irradiance. In this study, time-dependent soiling and cleaning data are used for modeling the yield of two parabolic trough plant configurations at two sites in Spain and Morocco. We apply a one-year soiling rate dataset in daily resolution measured with the tracking cleanliness sensor (TraCS). We use this as a basis to model the daily evolution of the cleanliness of each collector of a solar field resulting from the application of various cleaning strategies (CS). The thus obtained daily average xi (field) is used to modify the inputs to the yield analysis software greenius. The cleaning costs for each CS are subtracted from the project's financial output parameters to accurately predict the yield of a CSP project over its lifetime. The profits obtained with different CSs are compared in a parameter variation analysis for two sites and the economically best CS is identified. The profit can be increased by more than 2.6% by the application of the best strategy relative to a reference strategy that uses a constant cleaning frequency. The error in profit calculated with constant soiling and cleaning parameters compared to the simulation with variable soiling and cleaning can be as high as 9.4%. With the presented method, temporally variable soiling rates and CS can be fully integrated to CSP yield analysis software, significantly increasing its accuracy. It can be used to determine optimum cleaning parameters.

The degradation of reflector materials for concentrating solar thermal applications is analysed. Corrosion of their metallic reflective layer is considered a major problem in facilities which are located near industrial sites, where reduced sulphur gases may be present. Accelerated ageing tests were performed to study the influence of H2S on the corrosion of two types of silvered glass reflectors and one aluminium reflector. Different degradation patterns were found for silvered glass reflectors, whereas aluminium reflectors did not corrode in the presence of the sulphurous gas. Therefore, industrial pollution caused by this type of gas may decrease the solar collectors’ performance.