Design and analysis of portable loadless wind power source for ubiquitous sensor network

Nowadays, green technology solution using natural power such as solar, wind, waves et al. has been interested as an alternative power source instead of battery. This paper presents a portable power source driven by natural wind power. One of very efficient energy conversion mechanisms to change mechanical energy of natural power with electrical energy is a direct piezoelectric effect. However, this scheme requires AC stress with relative high frequency, which cannot be obtained from wind in the natural environment, because mechanical energy induced by wind shows almost constant power level. We propose a novel and simple mechanism, which converts the constant wind power to AC-like wind power using a propeller. Then, the resultant AC-like flow induces the vibration of piezoelectric cantilever, whose material is polyvinylidene fluoride (PVDF), and thereby electrical energy can be generated. Under 3.5 m/s wind speed condition (mean wind speed in city of Seoul), constant wind was converted to AC-like wind with 42.724 Hz frequency successfully and maximum output voltage from of PVDF cantilever was 4.05 V. This system, combined with processing and storage of the electrical energy, is expected to be a practical solution of wireless energy supply to ubiquitous sensor network.