Following World War I propeller aerodynamic design methodology was applied to the development of an efficient windmill for electricity generation in rural areas. H.R. Stuart experimented with combinations of windmills and direct-drive generators; while E.N. Fales, who had worked in aerodynamics at the U.S. Army’s McCook Field, conducted tests of scale-model windmills in wind tunnels.

This type of windmill provides slightly more power than the common multi-blade type while rotating six times faster; thus reducing gearing problems in wind electric power plants.

The artifact, invented and patented by Stuart and Fales, charged a 32-volt storage battery for lighting a farm near Springfield, Ohio beginning in 1922. It produced 230 watts in a 20 mile-per-hour wind (32 km/hr), reaching 1000 watts in higher winds. Similar propeller-driven units appeared subsequently using either direct drive or geared drives in larger sizes.