The impact of altitude, latitude, and endurance duration on the design of a high altitude, solar powered unmanned aerial vehicle

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In this paper, a previously developed conceptual design tool has been used to study the impact of the latitude, altitude, and the flight duration on the weight estimation and the main characteristics of a high altitude, long endurance and solar powered unmanned aerial vehicle. The available solar energy during the daylight hours has been calculated at given locations and altitudes for specific periods to be used in the pre-conceptual design stage. The pre-conceptual design methodology is based on an analytical and continuous method, which consists of establishing the relationships between all the components with analytical functions using the component characteristics. This design approach can directly provide a unique and optimal design. This study is conducted for a solar aircraft designed for a surveillance mission over Iraq. It is concluded that increasing the operational altitude can lead to a heavier aircraft in spite of the high levels of the available solar energy that can be absorbed. Hence, at high altitude, the surface area required for solar power generation is less than that needed to obtain adequate lift. Increasing the maximum solar irradiance during the daylight hours can lead to further lowering of the aircraft weight. Moreover, an increase in the daylight hours can be beneficial if the charging and discharging losses of the fuel cells are considered.