Solar power and solar cells
To retrieve this energy, solar cells cover the wing (around 0.512 [m2] for the 3.2 m wingspan airplane). In terms of efficiency, the better choice would have led us to GaAs Triple Junction cells with efficiencies of 27-28 [%]. However, those cells have a mass density of around 90 [mg/cm2]. As weight has a major impact on the required power for leveled flight, the better choice is silicon cells (e.g. RWE-32 cells) that reach 16-18 [%] efficiency with only 32 [mg/cm2]. Furthermore, the flexibility of those thin cells will also be an advantage for their integration on the wing.
Finallly, a total of 216 solar cells will be installed on the demonstrator plane. They will be divided in 3 modules connected in parallel, each of them composed of 2 series of 36 cells. The cells will be encapsulated using a mechanically favorable symmetrical laminate combined with a fiber glass reinforced plastic coating. This encapsulation is non-reflective. Thus, we will obtain a flexible arrangement easily integrable on the plane and connectable to the power circuit. At maximum sun conditions, the available power will be 28 [W] for each module, which makes a total of 84 [W].