Search

Jahresschrift für mitteldeutsche Vorgeschichte, Bd. 12 Nr. 1 (1925): Jahresschrift für die Vorgeschichte der sächsisch-thüringischen Länder

Wie in 2018 gezeigt werden konnte, sind die Wasserstofftechnologien nun technisch soweit ausgereift, dass sie eine praktikable und sichere Lösung zur Speicherung und Bereitstellung großer Energiemengen darstellen und zunehmend profitabler werden. Endsprechend steigen Absatzmengen und Anlagengrößen zunehmend. Bei den brennstoffzellenbetriebenen Automobilen sollen in den nächsten Jahren mehrere Zehntausend Fahrzeuge pro Jahr gefertigt werden und bei den LKW gehen die vorliegenden Bestellungen in die Tausende. Kleine KWK-Anlagen versorgen über 260 000 Wohnungen in Japan mit Energie und in Deutschland wurden knapp 5 700 Förderanträge bewilligt. Die Herstellung von grünem Wasserstoff hat die 10-20 MW-Klasse erreicht, wobei bereits über 100 MW Anlagen nachgedacht wird. Zudem hat sich gezeigt, dass vermehrt auf den Aufbau von Wasserstoffregionen zur Demonstration der Alltagstauglichkeit der Wasserstofftechnologien gesetzt wird.

In the last decades, the investigation of new secondary cells has been increased considerably. Very promising battery systems are the so called “Post Li-ion batteries” with metal anodes: metal-sulfur and metal-air (oxygen) batteries, in particular Li-sulfur, Mg-sulfur, Zn-air and Li-air batteries

Die Nutzung von Wasserstoff als Energieträger im Transportsektor nimmt stetig zu. Alleine in Deutschland hat sich die Anzahl der öffentlichen Wasserstofftankstellen in 2017 etwa verdoppelt, und mit dem Daimler GLC und dem Hyundai Nexo sind zwei neue Fahrzeuge vorgestellt worden. Es ist derzeit zu beobachten, dass die Einführung der Wasserstoffmobilität dabei weniger durch Privatnutzer, sondern vielmehr durch Betreiber von Fahrzeugflotten erfolgt. Zudem nimmt die Anwendungsbreite in diesem Sektor deutlich zu, was sich an neuen Konzepten für Lkw, Busse, Züge und Schiffe bemerkbar macht. Und auch im Industriesektor wurden die Bemühungen deutlich verstärkt, Wasserstoff umweltfreundlich über Elektrolyse herzustellen und sowohl energetisch als auch stofflich zu nutzen sowie wo immer möglich sektorenübergreifend einzusetzen.

In this work we apply concepts from fractional calculus to achieve a time-domain description of parallel resistor-constant-phase-elements for the accurate fitting of time-domain current-step responses. To achieve an accurate description of the fractional equivalent circuit in the time domain we formulate an equation based on the Mittag-Leffler function from fractional mathematics. Advantages of this approach allow a direct evaluation of impedance parameters for the assumed equivalent circuit model function without any further transformation to the frequency domain. To this end we explore the ability of fractional order models to fit the time-domain response of a system and if the real impedance spectrum could be reproduced by comparisons to actually measured impedance spectra of 18650 cells.

The operation of a secondary Li-air battery requires to run the battery in oxygen reduction reaction (ORR) as well as in oxygen evolution reaction (OER). OER represents the charge reaction and requires a sufficient catalyst for oxygen evolution. Currently carbon materials are widely used in cathodes of aqueous alkaline Li-air batteries due to their high electronic conductivity, stability, relatively low costs and catalytic activity towards oxygen reduction reaction (ORR). However, carbon-based cathode materials are non-stable in the potential range of OER as they start to corrode at potentials higher than open circuit voltage (OCV). Corrosion leads to high degradation corresponding to successive capacity loss and ultimately destruction of the cathode. To improve long-term stability and reduce side reactions such as H2 and CO2 evolution carbon-free bifunctional cathodes for aqueous alkaline Li-air batteries are of need. In this poster we present cathodes with a combination of Ag or Ni as conductive additive and Co3O4. Those were prepared with a dry-processed and solvent-free preparation method. Electrocatalytic activity regarding both ORR and OER was investigated by cyclic voltammetry (CV) for up to 300 cycles in half-cells. In addition structural and surface characteristics of the Ag/Co3O4 were investigated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). These combined measurements give new insights in the materials oxidation states and the stability of Ag oxides in Ag/Co3O4 cathodes throughout a complete battery cycle. Cathodes with the combination of Ag and Co3O4 show high activity for both reactions ORR and OER and a significant improvement in performance compared to both pure Ag and pure Co3O4 cathodes. Long-term tests show superior stability of the bimetal cathodes.

Summary. A commercially available planar 10 layer solid oxide electrolysis stack with electrolyte supported cells was characterized in an operating pressure range between 1.4 and 8 bar. Current-voltage characteristics and impedance spectroscopy were carried out by varying reactant gas composition, steam utilization and operating temperature. Abstract. The major part of the prospective power supply system will be based on solar and wind energy. The associated intermittency of energy supply due to varying weather conditions requires flexible storage and usage options. Converting electrical into chemical energy could be an essential constituent in this challenge. One promising path is the solid oxide electrolysis cell (SOEC) technology which can highly efficiently provide chemicals like hydrogen or derived hydrocarbons from electricity. These products can be used as fuels in mobility, for the chemical process industry, for conversion back to electricity or heating. SOECs offer a great potential for a highly efficient energy conversion due to their high operating temperature. Fast kinetics of electrochemical reactions lead to reduced electrochemical losses. Additionally, previous studies have shown that the efficiency of solid oxide cells can be significantly improved by operating at elevated pressure [1, 2]. A further reason for pressurization is the use of pressurized hydrogen in downstream processes like storage or fuel synthesis. Experimental results of a SOEC stack operated under pressurized conditions in water electrolysis mode are presented. For a parameter study a commercially available planar stack consisting of 10 electrolyte supported cells was used. The stack was operated in a pressure range between 1.4 and 8 bar. Parameter sensitivities were examined by varying reactant gas composition (xH2O=0.80…0.98), steam utilization (0.60…0.85) and operating temperature (750…850 °C). Pressure influence on open-circuit voltage (OCV) and reachable power density was examined on the basis of current-voltage curves. Impedance spectroscopy was carried out for further investigations to distinguish between different electrochemical phenomena. Whereas the impedance measurements show strong influences on several electrochemical and physical processes, current-voltage curves show only small changes due to the comparably low current densities reachable with electrolyte supported cells. [1] S. Seidler, Journal of Power Sources Vol. 196, 7195-7202 (2010) [2] L. Bernadet, ECS Transactions Vol. 68, 3369-3378 (2015)