IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia




Much effort and resources are being directed to reduce emissions in the most varied sectors. Today, aviation accounts for less than 5% of human related CO2 emissions, but projections for 2050 indicate that the growth of aviation emissions risks undermining the mitigation progress achieved in other sectors. In aeronautics, increasing fuel efficiency is considered the most effective mean of reducing emissions. Different options are being investigated, from the improvement of the air traffic system, or the adoption of more stringent regulations, to the improvement of aircraft performance. Future airplanes will be more electric and fuel cells represent promising systems to substitute the traditional gas turbine-based Auxiliary Power Units (APUs). Hybrid systems, combining solid oxide fuel cells and gas turbines are lighter than isolated fuel cells and more efficient than conventional gas turbines. This work is concerned with the study of hybrid system design for the application as aeronautical APUs. The state-of-the-art of such a fuel cell auxiliary power unit (FCAPU) was investigated. WTEMP, the software developed by the TPG of University of Genoa, was employed for the design and economic analyse. Physical, weight, and economic models were developed and the design spaces of four fuel cell system configurations were studied. A novel system was proposed (SysS), which is less complex than other hybrid systems proposed in literature, and showed interesting performance characteristics. The design study allowed identifying the n-dimensional space represented by the free variables of the FCAPU design, to identify the constraints of the design space, and to identify the influence of these variables on parameters of interest (e.g. system efficiency and weight). A study of the FCAPU operation in regional jets was performed. The influence of FCAPU design parameters on the economic performance of an airliner was investigated. The investment payback period was used as optimization parameter and optimum fuel cell systems were compared. The influence of the main parameters was analysed, allowing to conclude that a fuel cell weight reduction of 1 kg is equivalent (in terms of ticket price change) to a cost reduction of $3500-$4000. Moreover, fuel cell weights lower than 28 kg/m2 active area represent interesting systems from the environmental aspect, but economic benefits can be obtained only if the weight can be reduced to 7.7 kg/m2, for the economic scenario under study, or to at least 8.3 kg/m2, if the CO2 trading is included in the analysis (30$/tCO2). For economic scenarios with higher jet fuel costs, the breakeven SOFC power density (for economic viability) reduces considerably. The value for the peak jet fuel cost in July 2008 achieved the 0.4 kW/kg (which corresponds to about 12 kg/m2).


apu aeronáutica engenharia mecanica energia célula a combustível ciclo híbrido gas turbines fuel cells hybrid systems aeronautical auxiliary power units - apus transporte aéreo turbina a gás


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