Toward Small-Scale Wind Energy Harvesting: Design, Enhancement, Performance Comparison, and Applicability

Table 6

Summary of various wake galloping energy harvester devices.

Author	Transduction	Prism shape	Cut-in wind speed (m/s)	Cut-out wind speed (m/s)	Maximum power (mW)	Wind speed at max power (m/s)	Dimensions	Power density per volume (mW/cm^3)	Advantages/disadvantages and other information
Jung and Lee [27]	Electromagnetic	Circular cylinder	≈1.2	—	370.4	4.5	Two identical cylinders: 5 cm in dia., 85 cm in length.; Spacing distance:  cm.	0.111	(i) Determining the proper distance between the parallel cylinders for wake galloping energy harvesting, as 4-5 times the cylinder diameter, that is, = 4~5.; (ii) High output power.; (iii) Wide operational wind speed range.; (iv) Device volume is too big.
Abdelkefi et al. [74]	Piezoelectric	Windward: circular cylinder.; Leeward: square cylinder	0.4	—	0.04~0.05	3.05	Circular cylinder: 1.25 cm in dia., 27.15 cm in length.; Square cylinder: 1.28 × 1.28 × 26.67 cm^3.; Spacing distance: 24 cm.; Piezoelectric two identical cantilevers: 15.24 × 1.8 × 0.0305 cm^3.	5.72 × 10^−4	(i) Power from a galloping square cylinder was greatly enhanced by wake effects of an upstream circular cylinder.; (ii) Operational wind speed range was widened by wake galloping.; (iii) Diameter of the upstream cylinder and the spacing distance between two cylinders require careful adjustment.