SUSTAINABLE ENERGY HARVESTING TECHNOLOGIES – PAST, PRESENT AND FUTURE

Chapter 8: Energy Harvesting Technologies: Thick-Film Piezoelectric Microgenerato

Characterization on piezoelectric cantilever for its linear response at low frequency for measuring acceleration level of vibration

The output response of the piezoelectric cantilever has excellent linearity over a very wide dynamic range. This paper demonstrates the potential of piezoelectric cantilever to be a self-powered accelerometer. Three different-sized piezoelectric cantilevers were tested under a vibration source at 50 Hz, 100 Hz, and 150 Hz. It is proven that the piezoelectric cantilevers can be used as an accelerometer since the output voltage generated by the cantilever is linear and proportional to the vibration acceleration level far before reaching its resonance. Three piezoelectric cantilevers with similar length of 28.6 mm, but different width of 3.2 mm, 6.3 mm and 12.7 mm were used in the experiment in order to observe the linearity of the output voltage from different-sized piezoelectric cantilevers with the same resonance frequency. The length of piezoelectric may affect the resonance frequency of the cantilever, while the width of the piezoelectric will not. Hence, cantilevers with different width are chosen as the subject of the experiment. The linearity of the experiment results show the maximum error percentage obtained is between 5 to 15% when excited at a vibration magnitude in the range of 1 to 5-g

Fabrication and characterization of free-standing thick-film piezoelectric cantilevers for energy harvesting

Research into energy harvesting from ambient vibration sources has attracted great interest over the last few years, largely as a result of advances in the areas of wireless technology and low power electronics. One of the mechanisms for converting mechanical vibration to electrical energy is the use of piezoelectric materials, typically operating as a cantilever in a bending mode, which generate a voltage across the electrodes when they are stressed. Typically, the piezoelectric materials are deposited on a non-electro-active substrate and are physically clamped at one end to a rigid base. The presence of the substrate does not contribute directly to the electrical output, but merely serves as a mechanical supporting platform, which can pose difficulties for integration with other microelectronic devices. The aim of this paper is to describe a novel thick-film free-standing cantilever structure that does not use a supporting platform and has the advantage of minimising the movement constraints on the piezoelectric material, thereby maximising the electrical output power. Two configurations of composite cantilever structure were investigated; unimorph and multimorph. A unimorph consists of a pair of silver/palladium (Ag/Pd) electrodes sandwiching a laminar layer of lead zirconate titanate (PZT). A multimorph is an extended version of the unimorph with two pairs of Ag/Pd electrodes and three laminar sections of PZT

Non-symmetric Mach-Zehnder interferometer wavelength filter

A non-symmetrical Mach-Zehnder configuration with corrugated waveguide at one of its arm which acts as an interferometer is presented. The interference output intensity of the input light power depends on the operating wavelength, hence acting as a wavelength filter. The function of this wavelength filter is demonstrated by beam propagation method within range from 1000nm to 1800nm

Optical waveguide coupler fabrication based on time variation ion-exchange technique

Optical power transfer in a planar waveguide directional coupler is dependent on the geometry and refractive indices of the two waveguides. A method for fabricating optical directional couplers using ion-exchange Ag+/K+/Ca+ processes are presented, where the time of ion-exchange process is used to control the ratio of output power at the two output ports at a fixed temperature of 300 C. As far as the device geometry is still in single-mode regime, this method eliminates the need for high-resolution lithography for producing exact geometry of the device

Broadband Energy Harvesting using Multi-Cantilever based Piezoelectric

Wideband energy harvesting is essential particularly for extracting electrical energy from ambient vibration which is random. Researches show that the frequency bandwidth of the harvested energy can be effectively enhanced by using multiple cantilevers with different resonant frequencies connecting together. This paper investigates the effect of the different electrical configurations towards the output of the piezoelectric array. An array of four similar piezoelectric cantilevers was mounted side-by-side to operate as a system in generating electrical output across frequencies range up to 500 Hz. The resonant frequency of each of the cantilever was varied by introducing a proof mass of 0.15g, 0.50g and 1.00g at the tip of the cantilever. The result shows improvement in the frequency bandwidth of the piezoelectric array, where it is widened to 150 Hz with improved gap when connected in alternating polarities configurations. The piezoelectric array produces higher voltage when connecting in series configuration; but higher power when connecting in parallel configuration

Substrate-free thick-film lead zirconate titanate (pzt) performance measurement using Berlincourt method

Lead Zirconate Titanate or PZT is a high performance piezoelectric material which is able to generate charges when a proportional amount of stress is applied on the material. It has the potential to be used to fabricate micro-power generator for powering low power electronic devices, on top of already existence sensors and actuators. One of the indicators for comparing the performance of the smart materials is the piezoelectric charge coefficient, d33. In this paper, the actual d33 of PZT fabricated in the form of substrate-free thick-films were measured using Berlincourt Method whereby a standard dynamic force is applied to the materials and the resultant value of charges is recorded and compared over a period of time after the thick-films were polarized. The d33 values are compared between substrate-based and substrate-free specimens show a difference of about 45 % as a result of clamping effect contributed by d31. The experiment results also show that the thick-film PZT processed at 950 °C and polarized at 220 V with a thickness of about 120 μm has a piezoelectric charge coefficient of 82 pC/N