I saw a claim on the Internet that wind turbines can keep spinning for hours after the wind has dropped. Sounds incredible to me. So I decided to do a calculation based on the turbines at Watchtree. I used an approximation where I calculated the kinetic energy at rated power and divided by the rated power, assuming it would generate at that power until it stopped. I modelled the three blades as uniform spinning rods using data from here. I = 1/3.m.L^2 = 1/3 x 1500 x 23^2 = 264500kgm^2. Rotational speed = 1650 U/min. The units are in German: Umdrehungen pro Minute is revs per minute. That's 172 rad/s. Rotational ke = 1/2 I.w^2 = 4 x 10^9 Joules. At 660kW output, it would take roughly 100 minutes to use all that energy in the generator. Maybe there is some truth in the claim.
