15.8% (AWES style), and 13.8% (wind power style), i.e. power coefficients (Cp) respectively of 0.158 and 0.138. I remember having seen other measures, but I don’t remember where, maybe in @Ollie 's publications.
Concerning Kiwee:
Swept area is approximately 1 m². 210 Watt at 10 m/s wind speed lead to a power coefficient (Cp) of 0.35 with air density of 1.2. Simple calculation: 210 / (1/2 x 1000 x 1.2).
