Density of air da= 1.25 kg/m^3
Average velocity of the wind Vw= 4 m/s
Area of the inlet A= 4 m^2
Average force of the wind Fw= 0.5 x da x Vw^2 x A = 40 N
Average radius of the turbine r= 0.65 m
Torgue of the turbine T= r x Fw = 26 Nm
Rotational speed n= 8.33 rps (500 rpm)
Power of the turbine P= T x 2 x PI() x n / 1000 = 1.36 kW
Energy of the turbine in an hour Eh= 1.36 kWh
Hours in a year hy= 24 x 365 = 8760 h
Energy efficiency factor ef= 0.7
Energy in a year Ey= ef x Eh x hy = 8348 kWh