Abstract
Attempts to build solar High Altitude Long Endurance (HALE) airplanes are more and more frequent. In the future such airplanes may appear very useful for the economy because they may replace geostationary satellites in several applications for a fraction of cost. Unfortunately, necessary data on altitude effect on photovoltaic cells and batteries performance are not easily available. Therefore, flying testbed for their inexpensive testing is needed. Flat–upper surface airfoil was designed for application in small UAV dedicated for photovoltaic cells investigation at various altitudes. It should enable installation of rigid cells on the top of the wing without significant reduction of aerodynamic performance. It should also decrease a risk of damage of flexible cells due to the significant bending of long aspect ratio, elastic wings. This paper contains description of the design methodology, design assumptions and obtained results. Moreover experiment undertaken to evaluate the design is described as well. The wind tunnel and a semi–span model used for this experiment are presented together with obtained results. The model has exactly the same structure as envisaged structure of UAV, so flexibility of the wing is taken into account.
Highlights
Interest in aeronautical electric propulsion systems has been growing for several years
A few successful attempts to fly at high altitudes with solar electric propulsion have been already performed (Aerovironment Helios [6], Quinetic Zephyr [7]) as well as attempts to fly with very long endurance (Solar Impulse [8])
In the contrary the airplane for photovoltaic cells testing at high altitudes should be inexpensive, so small and simple in operations
Summary
Interest in aeronautical electric propulsion systems has been growing for several years. Application of good vacuum chamber is usually quite expensive and does not allow for the simulation of radiation intensity and spectrum in full range experienced in the flight These circumstances suggest that flight testing on the real airplane would be more useful. A few successful attempts to fly at high altitudes with solar electric propulsion have been already performed (Aerovironment Helios [6], Quinetic Zephyr [7]) as well as attempts to fly with very long endurance (Solar Impulse [8]) These airplanes were quite large and expensive. In the contrary the airplane for photovoltaic cells testing at high altitudes should be inexpensive, so small and simple in operations The weight of such an experimental UAV could be minimized because long endurance would not be required, so heavy load of lithium batteries is not necessary. The research was focused on maximization of lift to drag ratio and power factor, assuming low Reynolds numbers conditions since it was designed for small UAV
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