SMA Solar Technology (Germany)

As part of the transition to an energy system with 100% renewable generation, renewable energy power plants must increasingly take over responsibility for system stability. A key element in ensuring system stability is grid forming control of generation and storage units. In Germany, scenarios predict a significant expansion of renewable energy generation and storage systems in distribution networks. Integration of grid-forming systems into distribution networks raises several open questions, among them are power system oscillations and temporary island operation: Grid forming inverters may unintentionally lead to oscillation issues like those found in traditional transmission systems. A study reveals that as the level of virtual inertia in the distribution grid increases, these oscillations may become more pronounced which highlights the importance of implementing effective damping measures. Temporary island operation: In principle, grid-forming inverters enable the stable continued operation of critical sub-grids after a fault-related disconnection from the supply grid. Both disconnection and interception of the grid, as well as resynchronization and reconnection of the sub-grid with active generators and consumers are simulated in a series of laboratory tests and the basic suitability of this technology and the necessary requirements for this application are explained.

The increasing global reliance on renewable energy sources, particularly solar energy, underscores the critical importance of accurate solar irradiance forecasting. As solar capacity continues to grow, precise predictions of solar irradiance become essential for optimizing the performance and reliability of photovoltaic (PV) systems. This study introduces a novel hybrid forecasting model that integrates Nonlinear Autoregressive with Exogenous Inputs (NARX) with Long Short-Term Memory (LSTM) networks. The purpose is to enhance the precision of predicting daily solar irradiance in fluctuating meteorological scenarios, particularly in southwestern France. The hybrid model employs the NARX model’s capacity to handle complex non-linear relationships and the LSTM’s aptitude to manage long-term dependencies in time-series data. The performance metrics of the hybrid NARX-LSTM model were thoroughly assessed, revealing a mean absolute error (MAE) of 9.58 W/m2, a root mean square error (RMSE) of 16.30 W/m2, and a Coefficient of Determination (R2) of 0.997. Consequently, the proposed hybrid model outperforms the benchmark model in all metrics, showing a significant improvement in prediction accuracy and better alignment with the observed data. These results highlight the model’s effectiveness in enhancing forecasting accuracy under unpredictable conditions, improving solar energy integration into power systems, and ensuring more reliable energy predictions.

The research population is all students of Narotama University, 1633 students. There are 286 document results of urban solar articles on scopus.com. Select year range to analyze: 2011 to 2022, documents per year by source. More than 10 papers: Solar Energy 26 documents, Energy Procedia 16, Renewable Energy 13, IOP Conference Series Earth And Environmental Science 11. There are 286 document results of urban solar articles on scopus.com. Select year range to analyze: 2011 to 2022, documents by affiliation. More than 5 paper: Ecole Polytechnique Fédérale de Lausanne 13 documents,

Premagnetization of inductors with a permanent magnet seems to be a constantly recurring subject for power magnetic designers. Perhaps because there is not much literature on this topic available, the common considerations about it focus on obvious problems of the use of permanent magnets in high-frequency magnetic fields. This paper discusses the main degradation mechanisms of permanent magnets in premagnetized inductors and how they can be calculated in applications. After a short introduction to magnetic materials this paper addresses the reliability concerns and discusses degradation effects and their calculations. The calculations of acceleration factors are shown, which are important for the calculation of the reliability based on mission profiles.

Optical losses are a major source for current and power reduction in solar modules. Hence, various improvements aiming at reducing these losses have been suggested. In this work, we have evaluated the effects of anti-reflective coating, front glass thickness, polyvinyl butyral ultraviolet+ encapsulant, and light harvesting strings on the module performance individually and in combination. The individual and combined contributions were quantified by spectrally resolved optical measurements on the module components and simulations as well as electrical measurements on 1-cell and 54-cell modules. Optical gains and their impact on short circuit current are discussed in relation to a maximum current obtained from the solar cells internal quantum efficiency. The results of the electrical characterization are in good agreement with the optical analysis substantiating our approach. They show that a combined, relative current enhancement of 5% can be obtained for an optimized module, which compares to an increase of 1% absolute efficiency. Copyright © 2014 John Wiley & Sons, Ltd.

Abstract Mit längerfristigen Nutzerbefragungen in zwei unmittelbar benachbarten Bürogebäuden in Freiburg wurden das Temperaturempfinden der Nutzer und deren Zufriedenheit mit dem thermischen Raumkomfort zweimal täglich erfasst. Ein Bürogebäude wird im Sommer mit einem maschinellen Nachtlüftungskonzept konditioniert und das zweite verfügt über eine Betonkerntemperierung und eine Zu‐ und Abluftanlage. Auf Basis der vorhandenen Daten aus der Erhebung wurde mit Hilfe von Regressionsanalysen ein Modell zur Vorhersage der Komforttemperatur berechnet und mit den Modellen in DIN EN 15251 verglichen.User satisfaction with thermal comfort in office buildings applying environmental energy concepts. This paper presents results of a long‐term evaluation of occupant perception of and satisfaction with thermal comfort in two neighbouring office buildings in Freiburg. They were obtained in field surveys by daily questioning and accompanying measurements in high temporal resolution. One office building is conditioned during summer according to a night‐time ventilation concept and the second uses concrete core conditioning and a supply/exhaust ventilation system. Based on the survey data and a regression analysis, a model was calculated to predict the comfort temperature depending on the cooling concept employed. Results were compared to the comfort models of DIN EN 15251.

In this paper, we improve the first step in the arrival time algorithm used for shear wave speed recovery in transient elastography. In transient elastography, a shear wave is initiated at the boundary and the interior displacement of the propagating shear wave is imaged with an ultrasound ultra-fast imaging system. The first step in the arrival time algorithm finds the arrival times of the shear wave by cross correlating displacement time traces (the time history of the displacement at a single point) with a reference time trace located near the shear wave source. The second step finds the shear wave speed from the arrival times. In performing the first step, we observe that the wave pulse decorrelates as it travels through the medium, which leads to inaccurate estimates of the arrival times and ultimately to blurring and artifacts in the shear wave speed image. In particular, wave ‘spreading’ accounts for much of this decorrelation. Here we remove most of the decorrelation by allowing the reference wave pulse to spread during the cross correlation. This dramatically improves the images obtained from arrival time identification. We illustrate the improvement of this method on phantom and in vivo data obtained from the laboratory of Mathias Fink at ESPCI, Paris.

This contribution summarizes recent efforts to apply transmission electron microscopy (TEM) techniques to recombination-active extended defects present in a low density. In order to locate individual defects, electron beam induced current (EBIC) is applied in situ in a focused ion beam (FIB) machine combined with a scanning electron microscope. Using this approach defect densities down to about 10cm-2 are accessible while a target accuracy of better than 50nm is achieved. First applications described here include metal impurity related defects in multicrystalline silicon, recombination and charge collection at NiSi2 platelets, internal gettering of copper by NiSi2 precipitates and site-determination of copper atoms in NiSi2.