Abstract
HAPS (high-altitude pseudosatellites) are flight machines, airplane type, generally without pilot which fly in a definite zone at 18-22 km altitude, providing communication and surveillance services. These flight machines do not leave the atmosphere, and their purpose is to maintain a constant flight level for as long time as possible in the interest zone (e.g., five years) to fulfill their mission. HAPS energetic system proposed in this paper has to feed the electric propulsion system of HAPS (12.5 kW) and also to feed on-board equipment (navigation, data links, scientific equipment, etc.). On-board energy sources have to maintain HAPS in the interest zone for long periods. For this reason, it is used in the present solar power sources. A part of the generated energy is consumed on board; the rest is stored daytime and consumed nighttime. So, the system is provided with energy generation systems and also with storage and management systems. HAPS energetic system is a hybrid type, with two or more power sources. In this case, power sources are photovoltaic panels are used daytime and fuel cell are used nighttime, and also, a battery and/or a supercapacitor is used in transition periods from day to night and in peak load periods. In this paper, an electric power system used nighttime is designed and analysed. In this situation, the primary power source is the fuel cell and the secondary power sources are battery and/or supercapacitor. There are used numerical simulations models, developed in Matlab/Simulink, for all hybrid power source components: fuel cell stack, battery system, supercapacitors, conversion system, and fuzzy logic power management system. For a part of these components, there are used existing simulation models in Matlab/Simulink, adapted to these simulation requirements, and for others, there are designed and implemented simulation schemes according to these simulation requirements. An important component of the hybrid power source is the power conversion system which adapts the power sources parameters to consumer input requirements. A fuzzy logic power management system is designed.
Highlights
Pseudosatellite UtilityHigh-altitude pseudosatellites (HAPS) are UASs (Unmanned Aircraft Systems) recently considered by the big aviation companies as Boeing and Airbus and by spatial agencies NASA and ESA
Fuel cell simplicity and efficiency focused on—in the beginning by curiosity and by necessity—considerable scientific efforts which led to their diversification: Alkaline Fuel Cells (AFC), Proton Change Membrane Fuel Cells (PEMFC), Phosphoric Acid Fuel Cells (PAFC), Carbonate Melting Fuel Cells (MCFC), Oxide Materials Fuel Cells (SOFC), and so on [17]
The fuel cell hybrid power system is designed based on the load profile of pseudosatellites which consist of the following: 12.5 kW; 30-60 V PEM fuel cell power module (FCPM), with a nominal power of 10 kW; 48 V, 40 Ah, Li-ion battery system; 291.6 V, 15.6 F, supercapacitor system (6 × 48:6 V cells in series); 12.5 kW fuel cell DC to DC boost converter, with regulated output voltage and input current limitation; two DC to DC converters for discharging (4 kW boost converter); and charging (1.2 kW buck converter) the battery system
Summary
High-altitude pseudosatellites (HAPS) are UASs (Unmanned Aircraft Systems) recently considered by the big aviation companies as Boeing and Airbus and by spatial agencies NASA and ESA. The Zephyr 7 project for HAPS from Airbus Defence & Space will be used for surveillance, communication, and monitoring services on surfaces about tens of thousands km2 It owns the longest flight record—336 hours in July 2010, performed on wintertime at Great Britain latitude, when day is considerably shorter than springtime [5]. Zephyr 8 version was expected to have 28 m span and to fly in 2016 As it can be observed, propulsion solution varies from internal combustion engine with cryogenic store hydrogen for Phantom Eye to electric propulsion using solar energy stored in Li-ion batteries for night flight at SOLARA 50, SOLARA 60, and ZEPHYR. This program intended to combine extreme flight time
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