Research Center for Energy Technology

Oldenburg, Germany

Research Center for Energy Technology

Oldenburg, Germany
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Uhlig L.M.,Research Center for Energy Technology | Uhlig L.M.,Carl von Ossietzky University | Sievers G.,Leibniz Institute for Plasma Science and Technology | Bruser V.,Leibniz Institute for Plasma Science and Technology | And 2 more authors.
Science Bulletin | Year: 2016

Plasma-synthesized cobalt oxide supported on carbon has been analyzed for its use for electrocatalytic oxygen reduction reaction (ORR) in alkaline anion exchange membrane fuel cells (AEMFC). This work presents the ORR activity in 0.1 mol L−1 KOH and 0.1 mol L−1 K2CO3 at 25 °C. Cyclic voltammetry (CV) was used to determine the potentials at which the ORR occurs and to evaluate the stability of catalyst. Moreover, a rotating ring-disk electrode (RRDE) was used to investigate the activity of the catalysts and the formation of the by-product hydroperoxide anion (HO2 −) as well as to identify the preferred pathway of the ORR. Calculated kinetic parameters for the ORR for the cobalt catalysts are shown in this work together with a comparison to a commercial platinum catalyst. However, the cobalt oxide produced more by-products which could lead to damage of the membrane in a fuel cell through a radical attack of the polymer backbone. © 2016, Science China Press and Springer-Verlag Berlin Heidelberg.


Lin Y.H.,Research Center for Energy Technology | Lin Y.H.,National Cheng Kung University
Journal of Taiwan Society of Naval Architects and Marine Engineers | Year: 2016

This study aims to develop an virtual-image navigation mode to support the optimal route plan of Autonomous Underwater Vehicle (AUV) for the inspection task. For the safety of navigation, the results present the inspection process by virtual image and obstacle-avoidance as well. In terms of path planning, the optimal route is chosen by adopting the method of Multi-Objective Particle Swarm algorithm (MOPSO) with respect to virtual images of obstacles. Thus, each feasible route is searched iteratively according to two objectives, i.e. sailing time and joules consumption. In the process of image virtualization, the detecting points will be distributed over the limited space and the environmental depths for identifying the features of obstacles will be visualized referring to the stereo vision technique. In summary, the system is not only beneficial to optimize feasible routes but also identify features of obstacles for the purpose of tracking. Eventually, several underwater objects would be constructed and tested in the simulation for combining the image navigation with the underwater inspection of AUV.


Germer W.,Research Center for Energy Technology | Dekel D.,Cellera Inc. | Kerres J.,University of Stuttgart | Varcoe J.,University of Surrey | And 2 more authors.
Fuel Cells Bulletin | Year: 2015

Alkaline membranes and their applications were the main topic of the Workshop on Ion Exchange Membrane Applications, held in June 2014 in Bad Zwischenahn, Germany. The workshop saw 35 experts from nine nations listen to 19 talks given by membrane specialists from academic research facilities and professionals from industry. To give an impression of the workshop programme, this article presents four excerpts from the scientific talks.


Helmers H.,Fraunhofer Institute for Solar Energy Systems | Bett A.W.,Fraunhofer Institute for Solar Energy Systems | Parisi J.,Carl von Ossietzky University | Agert C.,Research Center for Energy Technology
Progress in Photovoltaics: Research and Applications | Year: 2014

An energy balance model for concentrating photovoltaic and thermal (CPVT) systems is presented. In the model, the CPVT system and its environment are represented using a set of input parameters. The main outputs of the model are the system's electrical and thermal efficiencies. The model accounts for optical losses. Thermal losses are derived from a thermal network model of the hybrid receiver. The solar cell performance is modeled as a function of the temperature and the irradiance. The robustness of the model is demonstrated by a sensitivity analysis of all input parameters. The influence of the operating temperature on the electrical and thermal performances and the overall efficiency of the CPVT system are discussed. The limiting cases of maximum electrical and thermal power outputs are presented. Further, the influence of the concentration ratio on the electrical and thermal performance and on the partitioning of these two power outputs is analyzed in detail. It is shown that high concentration reduces the thermal losses considerably and increases the electrical efficiency. At concentration ratios above 300, the system operates with an overall efficiency of 75% at temperatures up to 160 °C. Copyright © 2012 John Wiley & Sons, Ltd. An energy balance model for concentrating photovoltaic and thermal systems is presented and applied to investigate the influence of operating temperature and concentration ratio on the hybrid performance, that is, the electrical and thermal efficiencies. It is shown that high concentration offers several advantages to a hybrid photovoltaic and thermal system. As the concentration increases, the electrical efficiency also increases and, at the same time, thermal losses are reduced significantly, enabling overall conversion efficiencies of 75% at operating temperatures up to 160 °C. © 2014 John Wiley & Sons, Ltd.


Das P.R.,Research Center for Energy Technology | Komsiyska L.,Research Center for Energy Technology | Osters O.,Research Center for Energy Technology | Wittstock G.,Carl von Ossietzky University
Synthetic Metals | Year: 2016

Rheological measurements were used to study the flow behavior of composite slurries consisting of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) polyelectrolyte complex as binder and LiFePO4 as a model active material for the preparation of positive electrodes for lithium ion batteries. Various aqueous slurries containing 92% LiFePO4 and 8% PEDOT:PSS with different solid loadings were prepared. All slurries showed solid-like behavior due to formation of a network structure of LiFePO4 bridged by PEDOT:PSS chains. However, the solid loading of the slurries influences the distribution of the agglomerates and the binder affecting also the thickness, the adhesion and the electrical conductivity of the coatings casted from the different slurries under the same conditions. Hence, the electrochemical performance of single cells prepared with these coating changed with the solid loading of the slurry. The optimum electrochemical performance is achieved with slurries containing 40% solid loading. © 2016 Elsevier B.V. All rights reserved.


Derendorf K.,Fraunhofer Institute for Solar Energy Systems | Derendorf K.,Research Center for Energy Technology | Essig S.,Fraunhofer Institute for Solar Energy Systems | Oliva E.,Fraunhofer Institute for Solar Energy Systems | And 9 more authors.
IEEE Journal of Photovoltaics | Year: 2013

GaInP/GaAs//Si solar cells with three active p-n junctions were fabricated by surface activated direct wafer bonding between GaAs and Si. The direct wafer bond is performed at room temperature and leads to a conductive and transparent interface. This allows the fabrication of high-efficiency monolithic tandem solar cells with active junctions in both Si and the III-V materials. This technology overcomes earlier challenges of III-V and Si integration caused by the large difference in lattice constant and thermal expansion. Transmission electron microscopy revealed a 5-nm thin amorphous interface layer formed by the argon fast atom beam treatment before bonding. No further defects or voids are detected in the photoactive layers. First triple-junction solar cell devices on Si reached an efficiency of 23.6% under concentrated illumination. © 2011-2012 IEEE.


Lacombe J.,Research Center for Energy Technology | Sergeev O.,Research Center for Energy Technology | Chakanga K.,Research Center for Energy Technology | Von Maydell K.,Research Center for Energy Technology | Agert C.,Research Center for Energy Technology
Journal of Applied Physics | Year: 2011

In this paper, modeling of light propagation in silicon thin film solar cells without using any fitting parameter is presented. The aim is to create a realistic view of the light trapping effects and of the resulting optical generation rate in the absorbing semiconductor layers. The focus is on real three dimensional systems. Our software Sentaurus tcad, developed by Synopsys, has the ability to import real topography measurements and to model the light propagation using the finite-difference time-domain method. To verify the simulation, we compared the measured and simulated angular distribution functions of a glass/SnO2:F transparent conducting oxide system for different wavelengths. The optical generation rate of charge carriers in amorphous silicon thin film solar cells including rough interfaces is calculated. The distribution of the optical generation rate is correlated with the shape of the interface, and the external quantum efficiencies are calculated and compared to experimental data. © 2011 American Institute of Physics.


Bohn P.,Audi AG | Barragan S.A.G.,Research Center for Energy Technology | Komsiyska L.,Research Center for Energy Technology | Wittstock G.,Carl von Ossietzky University
Journal of the Electrochemical Society | Year: 2015

A new laboratory lithium ion cell in two electrode arrangement has been developed in order to apply in-situ short-term thermal stress tests to both electrodes. Cells were made from commercially available LiCoO2 cathodes, graphite anodes and electrolyte. A 60 s thermal stress was applied with different temperatures ranging from 100 to 250°C at the anode side after the cell formation and capacity tests. By comparison of the charge-discharge behavior of the cells before and after the thermal stress, capacity losses, increasing overvoltages and self-discharge have been observed as a function of the stress temperature. For detection of changes in the anode properties scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and computed tomography (CT) characterizations were used, and changes in the morphology and composition of the solid electrolyte interfaces (SEI) layer were observed. © 2015 The Author(s). All rights reserved.


Bohn P.,Audi AG | Garnica Barragan S.A.,Research Center for Energy Technology | Komsiyska L.,Research Center for Energy Technology | Wittstock G.,Carl von Ossietzky University
ECS Transactions | Year: 2014

A new laboratory lithium ion cell in two electrode arrangement has been developed in order to apply in-situ short-term thermal stress tests on both electrodes. Cells were made from commercially available LiCoO2 cathodes, graphite anodes and LP30 electrolyte. A 60 seconds thermal stress with different temperatures ranging from 100 to 250 °C has been performed at the anode side after the cell formation and capacity tests. By comparison of the charge-discharge behavior of the cells before and after the thermal stress, capacity losses, increasing overvoltages and self-discharge have been observed as a function of the stress temperature. For detection of changes in the anode properties SEM, TGA and CT characterizations were used, and changes in the morphology and composition of the SEI layer were observed. © The Electrochemical Society.


Kirchner C.N.,Carl von Ossietzky University | Trauble M.,Research Center for Energy Technology | Wittstock G.,Research Center for Energy Technology
Analytical Chemistry | Year: 2010

Scanning electrochemical microscopy has been used to analyze the flux of p-aminonophenol (PAP) produced by agglomerates of polymeric microbeads modified with galactosidase as a model system for the bead-based heterogeneous immunoassays. With the use of mixtures of enzyme-modified and bare beads in defined ratio, agglomerates with different saturation levels of the enzyme modification were produced. The PAP flux depends on the intrinsic kinetics of the galactosidase, the local availability of the substrate p-aminophenyl-β- D-galactopyranoside (PAPG), and the external mass transport conditions in the surrounding of the agglomerate and the internal mass transport within the bead agglomerate. The internal mass transport is influenced by the diffusional shielding of the modified beads by unmodified beads. SECM in combination with optical microscopy was used to determine experimentally the external flux. These data are in quantitative agreement with boundary element simulation considering the SECM microelectrode as an interacting probe and treating the Michaelis-Menten kinetics of the enzyme as nonlinear boundary conditions with two independent concentration variables [PAP] and [PAPG]. The PAPG concentration at the surface of the bead agglomerate was taken as a boundary condition for the analysis of the internal mass transport condition as a function of the enzyme saturation in the bead agglomerate. The results of this analysis are represented as PAP flux per contributing modified bead and the flux from freely suspended galactosidase-modifled beads. These numbers are compared to the same number from the SECM experiments. It is shown that depending on the enzyme saturation level a different situation can arise where either beads located at the outer surface of the agglomerate dominate the contribution to the measured external flux or where the contribution of buried beads cannot be neglected for explaining the measured external flux. © 2010 American Chemical Society.

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