Recent advances in the development of ultra-low power electric devices have drawn attention to the study of wind power generation flags based on piezoelectric elements. However, the piezoelectric film wind power generation method has been a challenge to improve power generation density and durability. Therefore, a new piezoelectric cylindrical shell wind power generation flag had been proposed by the authors as a flexible and durable power generation structure that utilizes vortex excitation vibrations. Preliminary experiments showed that it was expected to generate more than 10 times power than the conventional planar-shaped wind power generation flag. It is also shown through theoretical considerations that in order to construct a cylindrical generator flag using piezoelectric film that increased power generation in the low wind speed region, it was necessary to excite the vibration mode of circumferential wavenumber n=2 in order to utilize Kalman vortex excitation in this wind region. Moreover, in order to make the conventional structure, which generates power at high wind speeds, resonate at lower wind speeds, the radius of the cylinder must be large when the thickness was fixed and the thickness must be thin when the radius was fixed. However, the effect of variation of size on power generation characteristics has not been verified experimentally. In this report, wind energy harvesting experiments were performed with a number of flexible cylindrical shell type piezoelectric harvester flags, which has different dimensions and also thickness/radius ratios, and the structural design method to construct superior energy harvesting shell type generator, which will be able to generate large power at low wind speed, was discussed.