A novel axial-type wind harvester design with zero-voltage-threshold mechanical rectifier

Micro wind harvesters show great potential for self-powered sensors in wireless sensor nodes. Horizontal axial wind turbine is first used with a dedicated zero-voltage-threshold mechanical rectifier by utilizing commutator brushes for enhanced performance and addressing energy loss from diode rectifier in low-wind-speed cases. Two different generators, single-phase or three-phase generators, were designed and tested under different wind speeds and load conditions. The three-phase harvester achieves stable voltage output with weak ripples and a maximum power of 323 mW; it is 16 times higher than the case of diode rectification at lower wind speed. In contrast, the single-phase harvester obtains a maximum output power of 1.36 W, four times higher than the case of the three-phase prototype. Furthermore, the voltage ripple can be filtered to be faint with capacitors and inductors. The power density reaches 11.95 mW/cm², which is a significantly high value when compared with the literatures.