A Wind Turbine Efficiency Limit Higher than the Lanchester (Betz) Limit

TL;DR

This paper demonstrates that the maximum efficiency of wind turbines can be approximately 78%, exceeding the traditional Betz limit of 59%, by analyzing flow constraints and equations.

Contribution

It introduces a new theoretical upper limit for wind turbine efficiency that surpasses the Betz limit, based on flow assumptions and physical constraints.

Findings

Maximum efficiency limit is about 78%.

Traditional Betz limit of 59% is challenged.

Flow constraints prevent exceeding this new limit.

Abstract

It is shown that the upper limit on the fraction of power that can be extracted from an airstream approaching a wind turbine is about 78% rather than the historical value of 59%. This higher limit is based on the assumption that the wind turbine cannot accelerate the flow at its exit plane above the freestream velocity. The derivation of the historical limit of 59% must either violate the angular momentum equation or the continuity equation.