A large share of the primary energy is consumed to provide space heating. Geothermal energy offers a regenerative alternative. For reasons of efficiency and environmental protection, it is important to ensure the system integrity of a borehole heat exchanger (BHE). Previous investigations have focused on the individual components of the BHE or on the grout and pipe systems’ integrity. This study focused on the analysis of the hydraulic system integrity of the complete subsoil–grout–pipe system as well as possible thermally induced changes. For this purpose, a pilot-scale experiment was built to test a 1-m section of a typical BHE under in situ pressure, hydraulic and temperature conditions. During the tests the hydraulic system permeability of the soil and the BHE was measured continuously and separately from each other. In addition, the temperature monitoring array was installed in a 50-cm cross-sectional area. Significant temperature-related fluctuations in the sealing performance could be observed. Hydraulic conductivity limits required by VDI 4640-2 (Thermal use of the underground—ground source heat pump systems, 2019) were exceeded without frost action. The succeeding application of freeze–thaw cycles further enhances the system permeability. The study shows that the thermally induced effects on the system integrity of the BHE are larger and more significant than the subsequent frost-induced effects. The hydrophobic character of the high-density polyethylene (PE-HD) pipes as well as its high coefficient of thermal expansion seem to be the main points of weakness in the system. Optimization research should focus on the interface connection between grout and pipe, whereby hydrophilic pipe materials such as stainless steel or aluminum should also be considered as well as manipulation of the pipe surface properties of PE-HD.
Wie in anderen Alpenregionen auch, erfolgt die Trinkwasserversorgung in den Zillertaler Alpen vorwiegend privat oder in Genossenschaften aus nahe gelegenen Quellen, typischerweise mit kleinen Einzugsgebieten. Durch eine Veränderung der österreichischen Trinkwasserverordnung wurde der Arsengrenzwert von 50 µg/l auf 10 µg/l herabgesetzt, wodurch Quellwässer vielerorts nicht mehr den Anforderungen genügen. Es sind Maßnahmen zur Einhaltung des Grenzwertes herbeizuführen. In dieser Studie werden Ergebnisse der Stichtagsbeprobung des Zemmbacheinzugsgebietes auf einer Gesamtfläche von 225 km 2 vorgestellt. Binnen elf Tagen wurden 135 Quellen und Oberflächengewässer beprobt. Die Untersuchungen dienten der Auswahl alternativer Quellen anhand trinkwasserrechtlich relevanter Kennwerte mit Fokus auf Arsen und Uran. In einigen Teilen des Untersuchungsgebietes variiert die Grundwasserbeschaffenheit aufgrund diverser Wechsel petrographischer Einheiten kleinräumig. Das angewendete Konzept einer Stichtagsbeprobung ist gut dazu geeignet, einen weiträumigen Überblick der Grundwasserbeschaffenheit zu erhalten und Quellen zur Ergänzung oder Ersetzung der lokalen Wasserversorgung zu identifizieren. Diese Quellen sind intensiver zu beobachten, um letztlich mittels Zeitreihen Entscheidungen zu treffen.
low-κ dielectric LTCC was developed, to realize successful co-firing with NiCuZn ferrite tapes. A critical high-temperature process in the production of highly integrated LTCC modules is the migration of silver from inner conductors into the LTCC glass phase. Intensive silver migration causes strong deformation of LTCC multilayers during firing in air. Silver migration into the LTCC glass phase depends on oxygen content of the sintering atmosphere and can be minimized by sintering in nitrogen atmosphere. However, partial decomposition of NiCuZn-ferrite and formation of cuprite was observed during sintering in nitrogen and, consequently, the permeability of the ferrite decreases. As shown by a combined XRD/ thermogravimetric study the co-firing of LTCC modules with silver metallization and integrated ferrite layer demands precise adjustment of oxygen partial pressure.
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