The Betz-Joukowsky limit for the maximum power coefficient of wind turbines

The article addresses to a history of an important scientific result in wind energy. The maximum efficiency of an ideal wind turbine rotor is well known as the ‘Betz limit’, named after the German scientist that formulated this maximum in 1920. Also Lanchester, a British scientist, is associated with this limit, but his analysis relies on assumptions.

A study of early Russian publications on rotor aerodynamics now shows that the Russian aerodynamic school also produced the same result in the same year; in 1920 its leader Joukowsky derived the maximum efficiency for an ideal wind turbine based, like Betz, on a rigourous proof. Consequently, in order to honour all, this ideal efficiency should be named the ‘Betz-Joukowsky limit’.