Must be somekind of high torque blade design. Surely they can't go fast. Looks like it captures the wind somehow, but the blades is not pitched very much. Hmm.. Hard to think it's effecient in any kind of way.
Yes - large surface area, therefore high torque slow speed. Also note how the blades are broader nearer the tip, the opposite to the usual aerodynamic design.
Each blade is at least 1m long. Perhaps the diameter is about 2.5m. As far as I know, its intended as a new design which is claimed to be more efficient than the more usual thin blade design.