International Conference on Computer and Communication Engineering (ICCCE 2010), 11-13 May 2010, Kuala Lumpur, Malaysia 978-1-4244-6235-3/10/$26.00 ©2010 IEEE Theoretical Modeling and Simulation of MEMS Piezoelectric Energy Harvester Aliza Aini Md Ralib, Anis Nurashikin Nordin Department of Electrical and Computer Engineering Kulliyyah of Engineering International Islamic University Malaysia aliza.aini@gmail.com anis.nordin@gmail.com Hanim Salleh Department of Mechanical Engineering College of Engineering Universiti Tenaga Nasional Malaysia hanim@uniten.edu.my Abstract— Energy harvesting devices, capable of converting wasted ambient energy to electrical power are rapidly gaining popularity as a source of green and renewable energy. This work presents the design and simulation of MEMS based piezoelectric cantilever beam which can both harvest energy as well as monitor critical vibration frequencies in power plant gas turbines. The design of the energy harvesters consists of a cantilever beam structure with the interdigitated electrodes on the zinc oxide piezoelectric layer with nickel proof mass at the end of the beam. A mechanical finite element simulation was conducted using CoventorWare © . This paper illustrates the proposed theoretical modeling and simulation of piezoelectric energy harvesters. Keywords: piezoelectric, energy harvesting, cantilever beam. I. INTRODUCTION Wireless sensor networks have gained tremendous attention and popularity in commercial applications. A critical issue today is how to power these ubiquitous wireless sensor networks. The conventional batteries have become impractical due to their limited lifetimes, expensive replacement cost and the depleting source of lead. Energy harvesting provides the most promising solution, whereby wasted ambient energy such as light and vibration can be converted to useful electrical power and becoming an attractive alternative to the conventional battery. The increasing interest in piezoelectric devices can be seen in the proliferation of recently designed energy harvesting devices. One such MEMS device is a thin film piezoelectric power generator which employs the d33 mode (longitudinal effect) and has resonant frequency of 13.9 kHz with measured output performance of 1μW [2]. Another prototype of piezoelectric cantilever is capable of generating 270nW when operating at the resonance frequency of 229Hz [3]. To improve the power output and to provide frequency flexibility, an array of MEMS piezoelectric power generation has been designed. This device array has measured performance of 3.98μW effective electrical power and 3.93 volts DC output voltages with bandwidth of 226 – 234Hz [4]. There are five main components of fabrication on MEMS piezoelectric micro generator that is thin film composition and deposition technique, device design, fabrication process, electrical connections and packaging [5]. The main focus is to design a piezoelectric energy harvester that is able to harvest mechanical energy (mechanical vibrations) as electrical energy. The energy harvesters will generate power at the critical vibration to activate the condition monitoring sensor meant for maintenance and condition monitoring. This paper emphasizes on the design and simulation of a piezoelectric energy harvesting device used to power a wireless sensor for condition monitoring at power plants. The prototype consists of a cantilever beam structure with interdigitated electrodes on top of the piezoelectric layer. The piezoelectric material used is zinc oxide (ZnO). The proof mass made from nickel is attached at the tip of the beam. The device is designed to operate at the resonance frequency to get maximum electrical power output. This paper is organized as follows. Section II explains on the piezoelectric principle and design of the energy harvesters. Section III presents the theoretical modeling of piezoelectric energy harvester. Section IV presents the simulation, results and the discussion. Finally, the conclusion is given in Section IV. II. PIEZOELECTRIC PRINCIPLE AND DESIGN A. Basic Design Configuration Piezoelectric material deforms in the presence of electric field and vice-versa, it produces electrical charge when mechanically deformed [6].The piezoelectric constitutive equations is defined as follows: (1) (2) Where = mechanical strain (μm/μm) = mechanical stress (μN/μm2) Y = modulus of elasticity (Young Modulus) (μm2/μN) d = piezoelectric strain coefficient