Abstract
Solar-powered aircraft can perform long-term flights with clean solar energy. However, the energy derived from solar irradiation is influenced by the time of year and latitude, which limits the energy acquisition ability of solar aircraft with a straight-wing configuration. Hence, unconventional configurations based on increasing wing dihedral to track the sun are proposed to improve energy acquisition at high-latitude regions in winter, which may involve power loss caused by mismatch in the photovoltaic system. However, mismatch loss is seldom considered and may cause energy to be overestimated. In this paper, the energy acquisition characteristics of a joint-wing configuration are presented based on the simulation of an energy system to investigate the mismatch power loss. The results indicate a 4~15% deviation from the frequently used estimation method and show that the mismatch loss is influenced by the curved upper surface, the severity of shading and the circuit configuration. Then, the configuration energy acquisition factor is proposed to represent the energy acquisition ability of the joint-wing configuration. Finally, the matching between the aircraft configuration and flight trajectory is analyzed, demonstrating that the solar-powered aircraft with an unconventional wing configuration is more sensitive to the coupling between configuration and trajectory.
Highlights
Solar-powered aircraft are capable of performing long flights lasting for a day and night, or even several weeks, while relying on solar energy [1]
The energy acquisition model of solar-powered aircraft with a joint-wing design accounting for partial shading and the mismatch problem is established by the integration of a solar model, an energy system model and wing geometry
The effects of the airfoil surface, the severity of shading and circuit configurations are analyzed to clarify the energy acquisition characteristics when considering mismatch based on a 24 h flight simulation
Summary
Solar-powered aircraft are capable of performing long flights lasting for a day and night, or even several weeks, while relying on solar energy [1]. The wing structure, having low stiffness and strength, is prone to deformation or even damage, which contributed to the fall of the “Helios” drone, the experimental failure of Facebook’s Aquila and Google’s Solara 50, and Google’s shift to the high-altitude ball [10]. It is still a considerable challenge for solar-powered aircraft to achieve long-term flights in high-latitude areas in winter because a small sun elevation means a large angle of incidence on PV modules, low direct solar irradiance and limited energy harvesting. Energy acquisition calculation methods applied to solar-powered aircraft with unconventional designs need to be proposed
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