The biggest problem i see with folding panel VAWT's is the niose they would make "slapping" into position. Here's a down and dirty description of a similar device I've had bouncing around in my brain.

 The wind force would act on the panels forcing them open and closed when in the respective positions, due to the offset of the pivot point, so no complicated gearing mechanism would be required.

 Stops on the cross bracing would prevent the panels from going past the center point,when in fully closed position. I believe a design of this nature would increase the efficiency of a VAWT greatly, at the expense of keeping everyone awake for several city blocks!