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Seasonal evolution of Antarctic supraglacial lakes in the Sentinel satellite era
No full textSupraglacial lakes in Antarctica play a crucial role in ice sheet dynamics, as they influence ice stability by accelerating meltwater-driven processes such as meltwater injection and basal lubrication. The accumulation of meltwater on ice surfaces reduces albedo, causing more solar energy absorption, which in turn accelerates melting in a self-reinforcing cycle. Therefore, it is essential to monitor the seasonal evolution of surface meltwater features and get a better understanding of their dynamics. Earth observation data provide continuous and long-term observations of the vast and remote Antarctic ice sheet, but extracting reliable information on supraglacial lakes requires more than one satellite sensor. During the short period of lake occurrence, optical satellite imagery might miss shortly occurring dynamics in supraglacial lake extent due to heavy cloud cover. In contrast, the extent of supraglacial lakes is very difficult to interpret in cloud and illumination independent SAR data, as slightly overfrozen lakes become easily invisible due to backscatter similarities with the surrounding ice. The Sentinel mission provides the best source to combine advantages from both worlds and monitor the seasonal evolution of supraglacial lakes at best possible accuracy. We developed a deep learning-based classification algorithm to infer the extent of supraglacial lakes based on their spectral and backscattering properties, as well as their spatial appearance. The algorithm is based on a U-Net architecture with an Atrous Spatial Pyramid Pooling module to widen the receptive field and improve the detection of differently sized lakes. For each sensor, we trained the networks separately and reached classification accuracies with an F1-Score of 93% for Sentinel-1 and 91% for Sentinel-2. A final post-processing step combines both classification result to a bi-weekly recurrence map of maximum supraglacial lake extents during the austral summer months (November to March). This presentation addresses advantages and challenges of supraglacial lake mapping with Sentinel-1 and Sentinel-2 data and presents bi-weekly recurrence maps for 19 Antarctic ice shelves and regions with repeated supraglacial lake formation. Statistics on anomalies in maximum lake extents provide a circum-Antarctic picture on the seasonal evolution of supraglacial lakes during the Sentinel era 2014 to 2024. The circum-Antarctic data availability allows to compare the differences in supraglacial lake dynamics between years with high (e.g. 2019/2020) and low (e.g. 2023/2024) circum-Antarctic surface melt occurrence and regionally intense melt years (e.g. Dronning Maud Land 2017/2018). Accurate information on lake dynamics can inform hydrological and surface mass balance models to improve their ability to model surface melt processes
Supporting Technology Development with REMix: Identifying Key Properties for Future Energy System Relevance
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Unlocking Energy Flexibility: MGT with Integrated Power-to-Heat-to-Power Technology
No full textThe rising integration of renewable energy sources leads to a more volatile power grid. At the same time, limited grid expansion forces more efficient use of existing infrastructure and the integration of decentralized flexible energy storages. Solutions like Power-to-Heat-to-Power offer a cost-effective approach: while their electrical round-trip efficiency is lower than that of batteries, combined heat and power integration ensures high overall efficiency. An additional key factor is system resilience. Sector-coupled concepts - including co-firing of hydrogen and other renewable fuels - enable continued operation even when stored heat becomes insufficient.
Therefore, we propose a new concept that integrates a ceramic high-temperature energy storage (HTES) directly into the high-pressure path of an MGT between the recuperator and combustor. In times of low electricity prices, the HTES will be heated via a high-temperature induction heater. Heating the ceramic storage to the regular turbine inlet temperature (TIT) of about 1000°C allows for efficient reconversion to electricity and process heat. When the outlet temperature of the HTES decreases, the combustor keeps the TIT constant, providing a gradually increasing temperature rise, starting from minimal fuel input and ramping up to the regular temperature lift required when the HTES is depleted. To enable this wide operating range of air-to-fuel ratios with low pollutant emissions, a novel variable-geometry combustor is developed.
In this presentation, we introduce the overall concept, with its main advantages and technical challenges. This is followed by an overview of key component development, namely the variable-geometry combustor, the high-temperature induction heater and the solid media HTES, including initial experimental results from laboratory-scale tests. The presentation concludes with an overview of the ongoing work to virtually couple the MGT test rig with the integrated induction heater and HTES system, which is scheduled for completion early next year. Finally, we present initial plans for an industrial-scale demonstration
Konzeptionierung, Vorauslegung und Simulation von Kühlsystemen für NT-PEM Brennstoffzellen-Flugzeuge
No full textExtending the vertiport management tool VERTIGER for IAM scenarios: A drone cage demonstration
No full textEnhancing Machine Learning Model Performance through Synthetic Time-Series Eyetracking Data
No full textIn dieser Masterarbeit wird die Generierung synthetischer Zeitreihendaten aus der Blickbewegungsanalyse zum Zweck der Datenerweiterung zur Verbesserung der Klassifikationsleistung untersucht. Die synthetischen Daten werden mit Hilfe eines Variational Autoencoders (VAE) generiert und im Vergleich zu traditionellen Zeitreihenerweiterungstechniken bewertet. Es wurden verschiedene VAE-Architekturen, Eingabeeinbettungen und vorgegebene Verteilungen untersucht. Keines dieser Verfahren lieferte jedoch zufriedenstellende Ergebnisse in Bezug auf die Erzeugung von Daten, die den Originaldaten sehr ähnlich sind oder die Klassifikationsleistung effektiv verbessern. Im Gegensatz dazu führten traditionelle Augmentierungsmethoden, die Transformationen entlang der Zeitachse beinhalten, zu bescheidenen Verbesserungen der Testgenauigkeit.
Eine detaillierte Analyse des latenten Raums der VAE ergab eine ungleichmäßige Verteilung der kodierten Informationen über die latenten Dimensionen. Eine kleine Untergruppe von Dimensionen erfasste einen bedeutenden Teil des Inhalts, der für die Klassifizierung relevant war, während die Mehrheit einen minimalen Beitrag leistete. Darüber hinaus führte die Einbeziehung von domänenspezifischem Wissen in die VAE-Architektur nicht zu einem nennenswerten Leistungszuwachs, da das
Modell diese zusätzlichen Informationen nur in begrenztem Umfang nutzte
Multifunctional flexible carbon aerogels based on sustainable bacterial cellulose
No full textWe demonstrate that a combination of bacterial cellulose (BC) and resorcinol-formaldehyde (RF) imparts flexibility to its hybrid (BC + RF) and carbon aerogels (CAs). The microstructures of the produced aerogels exhibit continuous fibers from BC over which aggregates of RF particles are formed. The flexible CAs are able to recover from repeated compressive deformation with maximum compressive strain of 80%. These flexible CAs based on sustainable BC are achieved by a simple infiltration processing route and are suitable for applications in various fields such as gas adsorption, oil absorption, catalysis, energy storage, sensors, etc
NICOLHy - Preliminary design of novel insulation concepts for LH2 storage tanks
No full textAs the world transitions toward sustainable energy sources, hydrogen has emerged as a key player in the clean energy landscape due to its versatility and potential for widespread application. Liquid hydrogen (LH2) offers a promising solution for large-scale energy storage and transportation, owing to its high energy density. However, the storage and transport of LH2 pose significant technical challenges, primarily due to its extremely low boiling point of -253°C, which demands advanced cryogenic storage systems. Large-scale LH2 storage is crucial for establishing a robust hydrogen economy. However, upscaling the storage technology poses several hurdles. The existing technologies used in small and medium-sized storage systems are not suitable for large-scale applications due to long production times, low failure tolerance, and the limitations of spherical tank designs, which can reduce payload efficiency by up to 50 %.The NICOLHy project is at the forefront of addressing these challenges by developing a novel insulation concept based on vacuum insulation panels (VIP). This innovative approach aims to enable the safe, cost-effective, and energy-efficient storage of large quantities of LH2, with capacities ranging from 40.000 m³ to over 200.000 m³. This project seeks to overcome the existing limitations of LH2 tanks by developing a modular, open-form storage system that is time- and cost-efficient across production, operation, and service phases. The system is designed to be multi-failure tolerant and applicable for both onshore and offshore installations. Deliverable 1.2 aims to propose new insulation
concepts suitable for large-scale liquid hydrogen storage. The proposed concepts are founded
on the expertise of the project participants, as well as on the comprehensive literature review
conducted within the framework of WP1. The advantages and drawbacks of each LH2
insulation system are based on the experience gained from large-scale LNG tanks. The
utilisation of new designs based on VIPs is explored, owing to the promising features of these
technical solutions regarding scalability, safety, and costs. The current limitations in terms of
materials' performance, weight, size, scalability, vacuum degree, and construction process are
attentively analyzed to develop safer and more efficient concepts for stationary and maritime
applications. The critical aspects of the novel solutions developed are also highlighted