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

Study on the effect of lowering steam to carbon ratio in combined reforming of natural gas to the synthesis gas.

The objective of this research is to study the effect of lowering Steam to Carbon ratio in a combine reformer to produce syngas in order to optimize the performance of the combine reformer. A combine reformer in this project refers to the combination of steam methane reformer (SMR) and autothermal partial oxidation reformer (POX). Currently the steam to carbon molar ratio is maintaining at 3:1 ratio in order to prevent carbon deposition on the nickel catalyst active surface. To achieve this, a simulation model of the reformer unit using HYSYS simulation software version 3.01 was develops. The preliminary stage of this research will focus on literature review of natural gas reforming technology. Then second stage will focus on research for reaction kinetics on the SMR and POX reaction. A simulation model will then be developed to further analyze the reforming process by manipulating the operating condition and S/C ratio. Finally the last stage of the research will focus on optimizing the operation of both reformers. Based on the simulation result and analysis on various S/C ratio, this project suggest that operating the steam methane reformer using S/C molar ratio of 2:1 instead of 3:1 is favorable to methanol synthesis since carbon monoxide and carbon dioxide molar is increased at S/C ratio of 2:1 and the amount of hydrogen produced is still in excess to cope for the methanol synthesis requirement. However, since there is no physical experiment to determine the actual carbon boundary, there is no strong basis to prove that operating at S/C ratio at 2:1 will curb the carbon deposition problem. A conservative suggestion will be to lower down the S/C ratio to 2.5:1, saving 14 tons per hour of steam and its associated boiler feed water BFW treatment cost while increasing methanol production. A detail experiment to determine the actual carbon boundary is recommended since literature has been reported that optimum S/C ratio between 1.9 and 4.5 for SMR

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

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