Energy and Power Engineering, 2012, 4, 496-505 http://dx.doi.org/10.4236/epe.2012.46063 Published Online November 2012 (http://www.SciRP.org/journal/epe) Power Analysis for Piezoelectric Energy Harvester Wahied G. Ali, Sutrisno W. Ibrahim Electrical Engineering Department, King Saud University, Riyadh, KSA Email: wahied@ksu.edu.sa, suibrahim@ksu.edu.sa Received September 24, 2012; revised October 29, 2012; accepted November 7, 2012 ABSTRACT Piezoelectric energy harvesting technology is used to design battery less microelectronic devices such as wireless sensor nodes. This paper investigates the necessary conditions to enhance the extracted AC electrical power from exciting vi- brations energy using piezoelectric materials. The effect of tip masses and their mounting positions are investigated to enhance the system performance. The optimal resistive load is estimated to maximize the power output. Different ca- pacitive loads are tested to store the output energy. The experimental results validated the theoretical analysis and high- lighted remarks in the paper. Keywords: Vibration; Energy Harvesting; Piezoelectric Materials; Power Analysis; Resonant Frequency 1. Introduction Energy harvesting technology is used to generate electri- cal power from natural (green) energy sources. The con- cept of energy harvesting generally relates to the process of using ambient energy, which is converted into electri- cal energy. Research on energy harvesting technology became progressively larger over the last decade to de- sign self-powered microelectronic devices. With the ad- vances being made in wireless technology and low power microelectronics, wireless sensors are being developed and can be placed almost anywhere. Wireless sensor networks are progressively used in many applications such as: structure health monitoring, automation, robotics swarm, and military applications. However, these wire- less sensors require their own power supply which in most cases is the conventional electrochemical battery. Once these finite power supplies are discharged, the sensor battery has to be replaced. The task of replacing the battery is tedious and can be very expensive when the sensor is placed in a remote location. These issues can be potentially alleviated through the use of power harvesting devices. One of typical wasted energy is an ambient vibration that presents around most of machines and biological systems. This source of energy is ideal for the use of piezoelectric materials, which have the ability to convert mechanical strain energy into electrical energy and vice versa [1]. In general, there are three techniques to harvest the energy from the vibration: electrostatic, electromag- netic, and piezoelectric. Piezoelectric materials have a superior performance to be used for energy harvesting from ambient vibrations, because they can efficiently convert mechanical strain to an electric charge without any additional power and have a simple structure for real time applications [2,3]. In general, a piezoelectric energy harvesting can be represented as shown in Figure 1. The mechanical ener- gy (e.g., applied external force or acceleration) is con- verted into mechanical energy in the host structure. Then, this energy is converted into electrical energy by the use of piezoelectric material, and is finally transferred into electrical form to a load and/or a storage stage [4]. There- fore, three basic processes are performed: conversion of the input energy (vibration) into mechanical energy (strain) using a cantilever structure, electromechanical conversion using piezoelectric material, and electrical Figure 1. Schematic diagram of piezoelectric energy harvester [4]. Copyright © 2012 SciRes. EPE