Search

Die zunehmende Modularisierung und Standardisierung von Komponenten der Leit- und Sicherungstechnik erlauben umfängliches und frühzeitiges Testen von Produkten oder Produktkombinationen im Labor. Im Folgenden wird vorgestellt, welche Methoden bereits etabliert sind und was künftig im Labor noch folgen wird. Die Möglichkeiten der Labore am Deutschen Zentrum für Luft- und Raumfahrt (DLR) werden ebenso erläutert wie die Grenzen, die sich für Labortests ergeben.

Solid oxide electrolysis cells (SOECs) belong to the most efficient and cost-effective electrochemical devices for the energy storage application via power to gas (P2G) concept. Intermittent energy in form of electricity or heat from renewable sources can be stored long-termly in the magnitude of GWh level as chemical energy in H2 and CO through the electrolysis process occurs in SOEC systems. In comparison to conventional anode-supported and electrolyte-supported full ceramic cells, metal supported cells has many advantages, such as reduced manufacturing and maintenance cost, fast start-up features, excellent mechanical, thermal and redox cycle stability, and etc. In this work, novel metal-supported cells were fabricated on robust porous ferritic steel. Nickel free composite made of La0.1Sr0.9TiO3-α (LST) and gadolinium doped ceria (GDC) was applied as fuel electrode material. 3 m thick thin-film bilayer electrolyte of GDC/yttrium-stabilized zirconia (YSZ) was prepared by a combination of physical vapour deposition (PVD) and wet ceramic processing. The fuel electrode and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) air electrode were both deposited by screen printing. The gas-tightness of the electrolyte was monitored by differential air leakage tests at room temperature. Half cells with low leakage rate were selected and loaded with nickel nanoparticles as catalysts into the LST-GDC backbones to improve the electrochemical performance of the fuel electrode. Cells were tested under fuel cell mode and electrolysis mode, respectively. Performance and aging characteristics during operation were analysed by electrochemical impedance spectroscopy (EIS) and chronopotentiometry. Subsequently, the post mortem analysis was applied to facilitate the understanding of the degradation features and mechanisms specific to the electrolysis operation of the metal-supported cells.

A metal foam supported solid oxide fuel cell (SOFC) with yttria-stabilized zirconia (YSZ) and gadolinium doped ceria (GDC) bi-layer electrolyte is proposed. The prepared cells are supported by NiCrAl metal foam, which has been impregnated with La-substituted SrTiO3 (LST) as electrical conductive material. An LST-GDC anode functional layer was tape cast into green tape and then laminated onto the metal foam support. The measured thickness of the anode functional layer is approximately 20 μm after calcination at 1000 oC. Gas-tight YSZ electrolyte layers were deposited by vacuum plasma spray (VPS). Alternatively, porous YSZ layers were dip-coated with a fine suspension containing YSZ nanoparticles in order to obtain thin-film electrolytes. Successively, a gas-tight GDC electrolyte was deposited by EB-PVD method. The thickness of the gas-tight VPS YSZ electrolyte and the thin film YSZ-GDC bi-layer electrolyte was approximately 100 μm and 3 μm, respectively. The pore size distribution of NiCrAl foam supported substrates was characterized by mercury porosimetry analysis, the microstructure was demonstrated with SEM and the gas-tightness of the half cells was evaluated.

Cloud contamination is a challenge for optical remote sensing. This is especially true for the recording of a fast changing radiative quantity like land surface temperature (LST). The substitution of cloud contaminated pixels with estimated values - gap filling - is not straightforward but possible to a certain extent, as this research shows for medium-resolution time series of MODIS data. Area of interest is the Upper Mekong Delta (UMD). The background for this work is an analysis of the temporal development of 1-km LST in the context of the WISDOM project. The climate of the UMD is characterized by peak rainfalls in the summer months, which is also the time where cloud contamination is highest in the area. Average number of available daytime observations per pixel can go down to less than five for example in the month of June. In winter the average number may reach 25 observations a month. This situation is not appropriate to the calculation of longterm statistics; an adequate gap filling method should be used beforehand. In this research, two different algorithms were tested on an 11 year time series: 1) a gradient based algorithm and 2) a method based on ECMWF era interim re-analysis data. The first algorithm searches for stable inter-image gradients from a given environment and for a certain period of time. These gradients are then used to estimate LST for cloud contaminated pixels in each acquisition. The estimated LSTs are clear-sky LSTs and solely based on the MODIS LST time series. The second method estimates LST on the base of adapted ECMWF era interim skin temperatures and creates a set of expected LSTs. The estimated values were used to fill the gaps in the original dataset, creating two new daily, 1 km datasets. The maps filled with the gradient based method had more than the double amount of valid pixels than the original dataset. The second method (ECMWF era interim based) was able to fill all data gaps. From the gap filled data sets then monthly mean, anomaly, and trend maps were calculated. The accuracy of these two gap filling methods was assessed calculating RMS, mean absolute differences (MAD), and r2 of modelled values versus original MODIS LST values for clear-sky pixels only. These first statistical values showed that the adapted era interim data suites well to fill the data gaps. The gradient based method however should be used more carefully.

This work focus on the investigation of electrochemical properties of ABO3 perovskite based anode materials. Materials from the familly of Strontium titanate doped either on the A site with Lanthanum or on the B site with Niobium were investigated. Results about compatibility tests with other cell component, electrochemical performance are presented and discussed.