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Portable Applications (portable + application)
Selected AbstractsModelling Approach for Planar Self-Breathing PEMFC and Comparison with Experimental Results,FUEL CELLS, Issue 4 2004A. Schmitz Abstract This paper presents a model-based analysis of a proton exchange membrane fuel cell,(PEMFC) with a planar design as the power supply for portable applications. The cell is operated with hydrogen and consists of an open cathode side allowing for passive, self-breathing, operation. This planar fuel cell is fabricated using printed circuit board,(PCB) technology. Long-term stability of this type of fuel cell has been demonstrated. A stationary, two-dimensional, isothermal, mathematical model of the planar fuel cell is developed. Fickian diffusion of the gaseous components,(O2, H2, H2O) in the gas diffusion layers and the catalyst layers is accounted for. The transport of water is considered in the gaseous phase only. The electrochemical reactions are described by the Tafel equation. The potential and current balance equations are solved separately for protons and electrons. The resulting system of partial differential equations is solved by a finite element method using FEMLAB,(COMSOL Inc.) software. Three different cathode opening ratios are realized and the corresponding polarization curves are measured. The measurements are compared to numerical simulation results. The model reproduces the shape of the measured polarization curves and comparable limiting current density values, due to mass transport limitation, are obtained. The simulated distribution of gaseous water shows that an increase of the water concentration under the rib occurs. It is concluded that liquid water may condense under the rib leading to a reduction of the open pore space accessible for gas transport. Thus, a broad rib not only hinders the oxygen supply itself, but may also cause additional mass transport problems due to the condensation of water. [source] Portable Size DMFC-StackFUEL CELLS, Issue 3 2004A. Oedegaard Abstract A small, low temperature, direct methanol fuel cell stack for portable applications has been developed. Several flow field designs were investigated with respect to stable operation and high performance. Due to carbon dioxide and water production on the anode and cathode, respectively, methanol and oxygen access to the electrodes is hindered. During single cell operation the effect of both carbon dioxide evolution and water production on the current output was observed. The difference between parallel and serial feeding of both fuel and oxidant to the DMFC stack was also investigated. It was found that it is very important to remove reaction products from the active cell surface in order to ensure stable stack operation at low temperatures. The maximal power realised with the 12-cell direct methanol fuel cell stack was 30 W. [source] Assessment of Fuel-Cell-Based Passenger CarsFUEL CELLS, Issue 3 2004T. Grube Abstract Highly efficient energy conversion systems with fuel cells for vehicles, as well as for stationary and portable applications, are currently being discussed all over the world. Fuel cell technology is expected to help reduce primary energy demand and emissions of limited and climate-relevant pollutants. The high flexibility of fuel cell systems with respect to energy carriers opens up possibilities of modifying the energy sector in the long term. Introducing new fuels based on low-carbon, or in the long term carbon-free, energy carriers can contribute to reducing greenhouse gas emissions as well as locally and regionally active atmospheric pollutants. The use of hydrogen as feed gas for fuel cells on the basis of it being a non-fossil, renewable energy, leads to special benefits with respect to conserving resources and climate protection, but at present still represents a medium- to long-term prospect. A major milestone on the road to market success for all energy conversion systems with fuel cells is the reduction of costs. The definition of the ,appropriate" fuel represents a serious obstacle to the market introduction of fuel-cell-powered vehicles. Presenting data from a well-to-wheel analysis of various vehicle fuel systems at FZJ this article aims to discuss the potential benefits of future vehicle concepts with fuel cells in terms of primary energy use and greenhouse gas emissions. Results from a comparison of international studies on this subject will be used to identify relevant assumptions that lead to different answers in the evaluation process. [source] Anode-Supported Tubular Micro-Solid Oxide Fuel CellINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2 2007Partho Sarkar A tubular anode-supported "micro-solid oxide fuel cell" (,SOFC) has been developed for producing high volumetric power density (VPD) SOFC systems featuring rapid turn on/off capability. An electrophoretic deposition (EPD)-based, facile manufacturing process is being refined to produce the anode support, anode functional and electrolyte layers of a single cell. ,SOFCs (diameter <5 mm) have two main potential advantages, a substantial increase in the electrolyte surface area per unit volume of a stack and also rapid start-up. As fuel cell power is directly proportional to the active electrolyte surface area, a ,SOFC stack can substantially increase the VPD of an SOFC device. A decrease in tube diameter allows for a reduction in wall thickness without any degradation of a cell's mechanical properties. Owing to its thin wall, a ,SOFC has an extremely high thermal shock resistance and low thermal mass. These two characteristics are fundamental in reducing start-up and turn-off time for the SOFC stack. Traditionally, SOFC has not been considered for portable applications due to its high thermal mass and low thermal shock resistance (start-up time in hours), but with ,SOFCs' potential for rapid start-up, new possibilities for portable and transportable applications open up. [source] A portable multi-dimensional gas chromatographic system for field applicationsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 12-13 2003Jon H. Wahl Abstract We have constructed and tested a multi-dimensional gas chromatographic system that can be utilized for field portable applications. The chromatographic system is capable of one-dimensional separations and multi-dimensional gas chromatographic (MDGC) separations in a single compact package. Three different general multi-dimensional separation approaches are possible: column switching; traditional heart-cutting; and comprehensive analyses. The MDGC system utilizes a simple 10-port valving approach to accomplish these separations to a single point detector. Because of this valving scheme no hardware change is required to switch between the heart-cut and the comprehensive separation modes, only a software methodology change is required. An additional advantage of this valving approach is that 100% of the first-dimensional effluent is sampled to the second dimension for separation. The system is capable of rapid column heating (room temperature to 250°C in approximately 10 s) and rapid column cooling (250°C to room temperature within approximately 30 s). Preliminary results for heart-cut and comprehensive separations that target five compounds against high concentration levels of complex background are illustrated. [source] Very high efficiency solar cell modulesPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 1 2009Allen Barnett Abstract The Very High Efficiency Solar Cell (VHESC) program is developing integrated optical system,PV modules for portable applications that operate at greater than 50% efficiency. We are integrating the optical design with the solar cell design, and have entered previously unoccupied design space. Our approach is driven by proven quantitative models for the solar cell design, the optical design, and the integration of these designs. Optical systems efficiency with an optical efficiency of 93% and solar cell device results under ideal dichroic splitting optics summing to 42·7,±,2·5% are described. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||