The Hub of this Nice Wind Turbine seems to be low . Assuming it functionnal in open field like shown in others pictures , in this case, the wind trubine is in the town (city) in the middle of the buildings higher than the vertical Hub.
According to me , in fluid mechanics and dynamics , the winds flowing here will be turbulated and the forces and paths will be deformed (changed) . In order words the winds will be decelarated by buildings turbulations and won't reach the
blades of the vertical wind Turbine.
Even for classic 3 flat blades wind turbines , this hub is to low.
With these classic wind turbines, the wind are decelerated at the bottom of the blades and accelerated at the top of
the blades creating vortex.
Similar dispersion of the wind at the extremities of the vertical turbines blades must be observed at normal functionning conditions. But, with high pressured winds, the force applied on the surface of the vertical turbine blades can deforme the blades shape and decelerate the rotation. It can be used as a mechanical control of flexible vertical turbines blades and even assure continuous nominal torque generation.
Brief, You must increase the Heigth of your wind tour Hub.
and good luck.