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Descripción
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| The increasing interest in finding power systems that use fuels other than oil derivatives has promoted in recent decades the study of fuel cells, being in general the aircraft industry one of the fields that has shown outstanding interest. Even if air traffic is responsible for only 3% of the total greenhouse emissions, aircraft manufacturers are working to achieve a more efficient aircraft, which is leading to more electric or all-electric aircraft concepts. The unmanned aerial vehicles (UAV) represent a case of particular interest from the point of view of the fuel cells incorporation into aircraft propulsion systems. This is especially true for the small size UAV, with low maneuverability and long operation time, which are currently the most developed, with interest in both military and commercial civil applications. Airships are also a new field of application potential of fuel cells. Besides causing low environmental impact, the use of fuel cells in unmanned aircraft presents clear benefits that are intrinsic to this type of devices, which include its low noise level and its modularity. After the study of the state of the art and the feasibility of the implementation of different types of fuel cells in UAV, a sensitivity study of two types of fuel cells (hydrogen PEMFC and DMFC direct methanol) has been dealt with, compared to the same environmental conditions. The PEM/H2 fuel cell working at low temperatures (65-80 °C) have a quick start, provide high current, high specific energy density and low specific power density. The fuel used is hydrogen stored in different ways. On the other hand, fuel cells of DMFC?s have a lower power density and efficiency than the PEMFC, but they present greater simplicity and also higher energy density. Virtually all fuel cells are designed for operation on earth, so it is of capital interest to study how variation of environmental conditions during the flight of an aircraft affects the fuel cell performance. To do this, polarization curve models for both type of fuel cell that allow later use when studying 'stacks' have been defined. Thus, the analysis of the results obtained by varying parameters such as pressure, humidity and temperature of operation through the numerical simulation of these systems allows reaching conclusions about the influence of those parameters on the fuel cell performance for different cases. The atmosphere model used in the simulation is the ISA international standard atmosphere. In the PEMFC H2/air fuel cell simulations a 1-D model has been used to obtain the curve of polarization and the concentration overvoltage has not been taken into account. The operating temperature of the studied fuel cells (PEMFC and DMFC) is a determining factor in their performance, so the output voltage decreases when the temperature does due to an altitude increment. Therefore, the obtained results show that if it is compatible with the weight and endurance requirements, it is more appropriate to design a system on board an aircraft that maintains a constant optimal operating temperature regardless of the altitude. Moreover, the pressure decrement with the altitude has a harmful effect on the operation of both types of battery, PEMFC and DMFC, being more important on the PEMFC than in the DMFC. For the DMFC case, the temperature influence is by far the most important since it makes the battery voltage practically constant if it remains constant, regardless of the value of the atmospheric pressure, while the PEMFC H2/air battery behavior is more affected by the value of the atmospheric pressure. | |
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Internacional
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Si |
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Nombre congreso
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European Hydrogen Energy Conference 2014 |
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Tipo de participación
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960 |
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Lugar del congreso
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Sevilla |
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Revisores
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Si |
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ISBN o ISSN
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DOI
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Fecha inicio congreso
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12/05/2014 |
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Fecha fin congreso
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14/05/2014 |
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Desde la página
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371 |
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Hasta la página
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372 |
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Título de las actas
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European Hydrogen Energy Conference Proceedings |