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The Increasing Importance of the Substructure for PV Modules Under High Mechanical Loads
Full text linkWith the introduction of new cell formats M10, M10R, and especially M12, PV modules have significantly increased in size. The availability of thin tempered glass (<2 mm) has led to a rise in glass-glass modules, which offer a high moisture barrier and minimize cell breakage by placing cells in the neutral axis. However, this increase in size also results in higher weight. To mitigate this, both glass thickness and frame height are being reduced, which brings the mechanical load-bearing capacity of glass and frames into focus. The mechanical stiffness of current frames (28 to 35mm height) is considerably lower than older frames (40mm and above), leading to greater flexibility and deformation under mechanical loads. As material thickness remains typically constant, the strength requirements for components increase. Increased deflection can cause contact between the PV module and substructure at loads significantly below 2,400 Pa (IEC 61215-2 minimum load). While this was not a major concern in the past, module manufacturers now actively exploit it for load approvals. Installers of small PV systems must carefully read installation manuals to understand permissible loads. The situation is even more critical for large systems that utilize bifaciality, as the entire load is transferred through the frame and clamps/screws. Finite element simulations and mechanical load tests demonstrate the importance of using the correct substructure for testing the mechanical load capacity of PV modules and highlight potential interactions. Various module sizes and substructure variants are simulated to compare deformation and stress results
How to Explain Berlin by a Departed Author: Uwe Johnson: Berliner Sachen. Rostock Edition. Historical-Critical Edition of Works, Essays and Letters of Uwe Johnson, ed. by Holger Helbig, Ulrich Fries and Katja Leuchtenberger, Abt. II, Bd. 1, ed. by Gary Lee Baker, Robert Gillett and Katja Leuchtenberger, Berlin 2025.
No full textFünfzig Jahre nach dem Erscheinen von Uwe Johnsons Berliner Sachen im Mai 1975 liegt mit der sechsten Publikation der hybriden Rostocker Ausgabe eine Neufassung der 13 Texte vor, die einen zeitgeschichtlichen wie poetologischen Blick auf die geteilte Stadt Berlin bietet. Dem Herausgeber:innenteam um Gary Lee Baker, Robert Gillett und Katja Leuchtenberger ist es dabei gelungen, die Texte nicht nur neu zu edieren. Mittels einer ausführlichen Textgenese und eines überaus umfassenden textkritischen sowie Sachkommentars werden die komplizierte Entstehungs- und Veröffentlichungsgeschichte der Texte rekonstruiert, aber auch deren historischen und poetologischen Hintergründe dargelegt. Im Ergebnis steht ein knapp 700 Seiten umfassender Band, der mitunter in der Kommentierung zu akribisch, dabei aber stets sachlich und präzise ein Kaleidoskop der geteilten Stadt Berlin bietet.Fifty years after the publication of Uwe Johnson’s Berliner Sachen in May 1975, the sixth publication of the hybrid Rostock edition presents a new version of the 13 texts, offering a contemporary historical and poetological view of the devided city of Berlin. The editional team led by Gary Lee Baker, Robert Gillett and Katja Leuchtenberger has succeeded in doing more than just re-editing the texts. By means of a detailed text genesis and an extremely comprehensive text-critical and factual commentary, they have reconstructed the complicated history of the texts’ creation and publication, while also presenting their historical and poetological backgrounds. The result is a volume of almost 700 pages, which at times offers a meticulous commentary, but always provides a kaleidoscope of the devided city of Berlin in a factual and precise manner
Evaluation of Alternative Base Materials for Mitigation of Stress Relaxation Cracking in Thermal Energy Storage Tanks
Full text linkConcentrating solar power (CSP) plants with thermal energy storage (TES) face challenges related to stress relaxation cracking (SRC) in molten hot salt tanks. While alloy 347H stainless steel (SS) is commonly employed due to its stress corrosion cracking (SCC) resistance and sufficient mechanical properties, it suffers from SRC in the weld region. This study explores alloy 1.4910 as a potential alternative, known for its superior creep strength and molten salt corrosion resistance. Thermomechanical testing using a Gleeble® 3500 physical simulator reveals promising results for alloy 1.4910 heat affected zone (HAZ) and 16-8-2 filler (ER16.8.2) fusion zone (FZ), with no cracking observed within a 22-hour test period at elevated temperatures ranging from 600 to 800°C and initial true stress conditions of 650 MPa (0.174 strain) for HAZ and 460 MPa (yield strength) for FZ. In contrast, alloy 347H HAZ and matching filler FZ experienced cracking within a few hours at 800°C. Metallurgical characterization and fractography are additionally conducted on cross welded 1.4910 samples with 16-8-2 filler and thermomechanical Gleeble® samples
Home Energy Management Systems (HEMS): 2nd Market Overview for Germany (2025)
Full text linkThe integration of increasing renewable energies requires the use flexibility on the demand side. Single-family houses (SFHs) play a key role as they connect electricity consumption with decentralized generation. Home Energy Management Systems (HEMS) are central to coordinating flexible loads, such as electric vehicles (EVs), heat pumps (HPs), heating elements, and battery storage systems (BSS), with renewable supply. HEMS enable optimization of self-consumption from photovoltaic (PV) systems and can respond to dynamic electricity tariffs and grid signals, allowing households to shift usage to periods of high renewable availability. With 13 million SFHs in Germany, HEMS offer considerable flexibility potential. Next to optimizing energy flows, they provide economic benefits by reducing electricity and grid-related costs. Despite their potential, the growing HEMS market suffers from a lack of transparency regarding available systems, functionalities, and interoperability. This makes it difficult for consumers and installers to identify and implement suitable solutions. Without HEMS, millions of decentralized generation and consumption units in SFHs would operate uncoordinated. However, operating HPs or charging electric vehicles with zero-emission electricity requires systems that can respond to the availability of renewable energy. This paper provides a comprehensive analysis of the German HEMS market. It presents current HEMS solutions, identifies and compares core system functionalities, and outlines expected developments. The study also includes insights from electrical installers and evaluates the added value HEMS can offer to installation companies
Development of a Small Aquavoltaic System for Co-Production of Microalgae and Electricity
Full text linkIn this study, a small aquavoltaic system was developed to simultaneously generate solar electricity and improve the conditions for the cultivation of microalgae. The key operating parameters of the system — dissolved oxygen, pH, water temperature and dead zones — were evaluated to gain insights into the dual benefits of integrating solar energy into aquaculture systems. In this context, the independent variable parameters of the rotation speed of a paddle wheel in the pond at 10, 20, and 30 rpm, the water depth at 15, 25, and 35 cm, and the reaction time at 0.5, 1 and 1.5 h were evaluated on May 9-15, 2023. The Response Surface Methodology, the Central Composite Design, and the experimental design were used to optimize the independent variables on the amount of dissolved oxygen for microalgae production in the open raceway pond. In this case, a maximum dissolved oxygen of 6.94 mg/l was achieved after 1 hour, at a water depth of 25 cm, and at a rotation speed of 20 rpm. Increasing the rotation speed from 10 to 30 rpm brought the dissolved oxygen content in the water to the desirable range of 6 to 7 mg/l and resulted in a decrease in stagnant areas from 21.05% to 9.16%. In addition, the shading effect of the photovoltaic system on the open pond was more than 80%, which led to a decrease in water temperature and dissolved oxygen
Numerical Investigation of Dual Metal Hydride Bed Based Thermochemical Energy Storage System
Full text linkThermochemical energy storage system is known for good thermal stability and high energy storage density. Metal hydride based thermochemical energy storage systems are reported to store thermal energy at higher temperatures. In this analysis, NaMgH2F and Mg2NiH4 are used as high temperature and low-temperature metal hydrides. One kg of NaMgH2F is used as thermal energy storage media, while Mg2NiH4 is used as hydrogen storage media. The analysis includes the study of energy charging and discharging characteristics with heat transfer phenomenon in metal hydride with variation in thermal conductivity of high temperature metal hydride bed. With the increase in thermal conductivity of high temperature metal hydride bed, the heat transfer between heat transfer fluid and metal hydride bed during the energy charging and discharging process has improved. A marginal increase in thermal energy stored and discharged in/from the metal hydride bed system has been observed with an increase in the thermal conductivity of the metal hydride bed. Thermal energy stored in the MH beds for thermal conductivity of 0.5 W/m K, 0.75 W/m K, and 1 W/mK, are 270.88 kJ, 273.39 kJ, and 274.96 kJ, respectively. The energy desorbed from the system for thermal conductivity 0.5 W/mK, 0.75 W/mK, and 1 W/mK are observed as 251.25 kJ, 258.22 kJ, and 260.57 kJ, respectively. The three cases of thermal conductivity have reported an energy storage efficiency of 92.75%, 94.45%, and 94.77%, respectively
Inline Mapping of Amorphous Silicon Layer Thickness of Heterojunction Precursors Using Multispectral Imaging
Full text linkIn this paper, we present an inline characterization technique to determine spatially resolved thickness maps of ultra-thin layers on textured silicon substrates. The technique is based on multispectral imaging and optical modelling of discrete spectral reflectance data using rigorous polarization ray tracing and the transfer matrix method. The study demonstrates that quantitative inspection of ultra-thin amorphous silicon (a-Si) layers on textured silicon substrates requires an extension of the standard RGB illumination by two additional LED wavelengths in the near-UV. As the required five images are measured in less than a second, the tool is a suitable candidate for inline applications. The optical modelling requires reflectance-calibrated images which are obtained via linear calibration functions and allows the a-Si thickness to be determined at each pixel. The thin-film thickness can be determined either by a direct modelling of the measured reflectance spectra or by a differential approach using the reflectance spectra before and after coating to eliminate effects from non-idealities due to scattering as well as instrumental errors. The a-Si thickness extracted from the reflection data at the five chosen LED wavelengths shows good quantitative agreement with reference values from spectrally-resolved differential reflectance data. Evaluating a test sample with an intentional a-Si thickness variation, we compared the results from the multispectral thickness map and reference values from spectroscopic ellipsometry. We found good quantitative agreement for a-Si thicknesses above 10 nm and a slight overestimation of about 1.5 nm for thinner layers. Overall, the multispectral approach based on only five different channels proves to allow quantitative thickness maps with reasonable accuracy at inline speed
A Lightweight Approach to FDOs via Bioschemas, RO-Crate and Signposting on GitHub Pages
Full text linkHere we present a proof-of-concept using Bioschemas, RO-Crate and Signposting as a lightweight approach to FDOs describing research outcomes exposed on GitHub pages. Research artifacts produced by a research and development team, namely the SemTec team at ZB MED, are exposed via GitHub pages and enriched with structured metadata using schema.org and Bioschemas. Research artifacts corresponding to the same research project are put together in an RO-Crate. Signposting is used on the GitHub landing pages. The combination of these three elements facilitates rich FAIR metadata for research artifacts
Overheating-Dependent Heterogeneous Crystal Nucleation in a Lithium Disilicate Melt
Full text linkThe influence of thermal history on the kinetics of liquid-solid transformations is investigated for heterogeneous crystal nucleation near the liquidus temperature in a melt with lithium disilicate composition in contact with a PtRh10 carrier. It is shown that the achieved undercooling depends on the preceding superheating protocol. This is explained by a distribution of nano-sized cavities on the surface of the precious metal, in which crystalline clusters can persist above the liquidus temperature for a characteristic time. In series of different surface quality of the PtRh10 carrier and for air purging, these times are in the range of 5-20 s, which seems relatively long compared to metallic melts, where this phenomenon was first observed in the millisecond range. The high viscosity of the silicate melt at the liquidus temperature is discussed as the reason for the difference in the persistence time
Application of Neural Networks for Assistance Systems in Wastewater Treatment: Optimisation of the Biological Treatment Stage
No full textDie Berliner Wasserbetriebe (BWB) haben sich das Ziel gesetzt, bis 2030 klimaneutral zu arbeiten und die Energiewende zu unterstützen. Großes Optimierungspotenzial für die Abwasserreinigung liegt in der biologischen Behandlungsstufe, welche mit ca. 60 % den größten Energieverbrauch hat. Im Kooperationsprojekt „ANNA“ wurde erstmals die Belüftungssteuerung der biologischen Reinigungsstufe unter Anwendung künstlicher neuronaler Netze (KNN) in einer ausgewählten Prozesslinie auf dem Klärwerk Münchehofe untersucht. Ziel des Projektes war es, ein am Markt erhältliches Echtzeitassistenzsystem zur Reduzierung des Energieverbrauchs bei gleichzeitiger Einhaltung der Grenzwerte unter Betriebsbedingungen zu testen. Zur Modellierung des Prozesses kamen KNN zum Einsatz, um die Ablaufkonzentration der Versuchslinie zu prognostizieren. Die KNN wurden mit physikalisch relevanten historischen Daten trainiert. Mit Hilfe der modellbasierten Prognosen ließen sich Vorschläge für Soll-Sauerstoffkonzentration oder Soll-Luftmengen berechnen und umsetzen. Die Implementierung des Assistenzsystems erfolgte schrittweise. Im ersten Schritt wurde die Anwendung des Assistenzsystems manuell getestet. Die vom Betriebspersonal umgesetzten Handlungsempfehlungen führten zu einem reduzierten Luftverbrauch von ca. 10 %. Gleichzeitig wurde eine Erhöhung der Ammoniumkonzentration (NH4-N) im Ablauf der Versuchslinie (2,2 mg/l) im Vergleich zur Vergleichslinie (1,6 mg/l) um 0,6 mg/l festgestellt. Innerhalb der Versuchsphase wurde die Abwasserbeaufschlagung in der Versuchs- und Vergleichslinie teilweise um 10 % erhöht. Hierbei konnte beobachtet werden, dass die Handlungsempfehlungen eine präzise frachtbasierte Belüftungssteuerung ermöglichten. Auch Regenereignisse erkannte das Assistenzsystem frühzeitig, wodurch rechtzeitig, entsprechend des eintretenden Frachtstosses, die Belüftung erhöht und anschließend wieder herabgesetzt wurde. Auf Grundlage der positiven Ergebnisse wurde das Assistenzsystems in den automatischen Betrieb genommen, um seinen Einfluss auf das Optimierungspotenzial und die Ablaufqualität zu untersuchen.Berliner Wasserbetriebe (BWB) has set itself the goal of becoming climate-neutral by 2030 and supporting the energy transition. There is great potential for optimising wastewater treatment in the biological treatment stage, which has the highest energy consumption at around 60%. In the "ANNA" cooperation project, the aeration control of the biological treatment stage was analysed for the first time using artificial neural networks (ANN) in a selected process line at the Münchehofe wastewater treatment plant. The aim of the project was to test a real-time assistance system available on the market for reducing energy consumption while simultaneously complying with the limit values under operating conditions. ANNs were used to model the process in order to predict the effluent concentration of the test line. The ANNs were trained with physically relevant historical data. The model-based predictions were used to calculate and implement suggestions for target oxygen concentrations or target air volumes. The assistance system was implemented in stages. In the first step, the use of the assistance system was tested manually. The recommendations for action implemented by the operating personnel led to a reduction in air consumption of approx. 10 %. At the same time, an increase in the ammonium concentration (NH4-N) in the effluent of the test line (2.2 mg/l) compared to the reference line (1.6 mg/l) by 0.6 mg/l. During the test phase, the wastewater treatment in the test and reference line was increased by 10 % in some cases. It was observed that the recommendations for action enabled precise load-based aeration control. The assistance system also recognised rain events at an early stage, whereby the aeration was increased and then reduced again in good time, depending on the freight impact. Based on the positive results, the assistance system was put into automatic operation in order to investigate its influence on the optimisation potential and process quality