| Summary: | Remote sensing equipment are widely used in buildings to monitor building health and collect usage data. A lot of interest has been generated in self-powered remote sensing equipments due to the fact that these sensing devices are embedded inside the building and replacing their batteries can become impractical of costly. Self-powered devices convert various forms of energy from the surrounding environment and convert them to electrical energy.
The sources of energy in the ambient environment include solar, heat, vibration and wind. Among them vibration energy is the most ubiquitous and underutilized sources of energy.
Electromagnetic, electrostatic and more recently piezoelectric transduction mechanisms can be used to convert vibration energy to electrical energy. The high energy density of piezoelectric transduction mechanism makes it the most suitable method of harvesting energy from vibrations. Strain in a piezomaterial caused by vibrations generates electrical energy.
Various types of wind action produce vibration. They include vortex shedding, buffeting, fluttering and galloping. One of traditional design for wind energy harvester consists of a cantilever beam with a proof mass attached to one end of the beam. Previous studies have shown that a cantilevered beam with a square shaped tip mass with the piezoelectric material bonded to the cantilever beam is able to produce electricity based on the translational galloping phenomenon. Translational galloping is a self-excited aerolastic phenomenon, giving rise to transverse oscillations normal to the direction of wind flows in structures with weak damping when wind velocity exceeds a critical value. The study concluded that energy harvesting based on this design is superior to some of the other methods mentioned and the power generated is sufficient to power remote sensing equipment(Zhao, Tang, & Yang, 2012).
The harvester mentioned above is known as a linear vibration resonator. It can be modeled as a spring mass system with a single degree of freedom (SDOF) which utilizes resonance phenomenon to obtain peak amplitude. A single vibrating body inherently has more than one degree of freedom (DOF), up to six in space and three in plane. It may be possible to further improve the efficiency of this type of harvester by utilizing multiple DOF’s and obtaining multiple peak amplitude for power output.In addition, as part of an effort to improve the efficiency of Piezoelectric Harvesters, this project will study the effectiveness of using mechanical frequency up conversion techniques using magnets. Frequency conversion techniques have been used in the past to increase the frequency, hence the effectiveness of low frequency vibrating body energy harvesters to higher frequencies with increased outputs (Zorlu, et al., 2011).
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