2, 3, 4 and 16 blades wind turbine speed (efficiency) test at Technopolis

The wind turbines in this video are tested by means of a orientable fan. The green light " should " give the power output. But I guess it only measures the voltage and hence the speed of the blades. But the video can illustrate the efficiency of the different systems.
Filmed @ Technopolis,

Видео 2, 3, 4 and 16 blades wind turbine speed (efficiency) test at Technopolis канала Ecolomeus