IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING IEEJ Trans 2018 Published online in Wiley Online Library (wileyonlinelibrary.com). DOI:10.1002/tee.22733 Paper Analysis of Batteries or Supercapacitor as Energy Storage Device for a Sound Energy Harvester System Hui Fang Liew * a , Non-member Rosemizi Abd Rahim ** , Non-member Muzamir Isa * , Non-member Baharuddin Ismail * , Non-member Syed Idris Syed Hassan * , Non-member This study focuses on the concept analysis of the suitability of batteries or a supercapacitor as an alternative storage device in low-power electronic devices. Sound waves were utilized as a source of energy for charging the supercapacitor, and a piezoelectric Q220-A4-503YB device was used as the energy transducer. A respectable performance of the piezoelectric in terms of the output force and voltage was found at the operating frequency of 68 Hz with an input source of 96 dB sound intensity level. Based on our experiments, it was found that the supercapacitor is more efficient as a storage device for a low-power source when compared to batteries because of the charging current. The charging time of the 0.22-F supercapacitor used in either the Villard or Dickson mode is higher when compared to the others. The charging time of the supercapacitor with the voltage regulator of 0.5 and 1.0 W by the Villard multiplier was longer compared to the Dickson multiplier, which produced an output voltage of 9.817 and 9.647 V, respectively. From this study, it is proven that the delivery of the voltage stored in a supercapacitor with a higher capacitance would take a longer time in terms of process charging and discharging as compared to one with a lower capacitance. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. Keywords: batteries; energy harvesting system; noise; piezoelectric materials; supercapacitor; sound wave Received 2 August 2017; Revised 8 December 2017 1. Introduction The field of power harvesting has undergone significant evo- lution over the past few years due to the ever-increasing needs and desire to produce portable and wireless electronics with pro- longed lifespan. An energy harvesting system is critical, as the process is associated with the capability of capturing, convert- ing, storing, and delivering energy in a form that can be used to provide the power needed by the system it serves, and it is therefore considered energy-free. Energy harvesters (EHs) exploit efficient renewable and environmental energy sources, including solar [1,2], wind [3,4], acoustic [5,6], thermal [7], heat [8], hydro energy [9], ambient vibration energy [10,11], temperature gradi- ent [12], magnetic energy [13], and mechanical vibration [14], all of which have been attracting the attention of a wide range of engineering specialties. Unfortunately, the output power of vibration and acoustic sources are lower than that of solar and wind energy sources. This is the main issue for the wide practical application of vibration and acoustic energy harvesting. However, vibration and acoustic energy exhibit several unique advantages compared to solar and wind energy. First, harvesting vibration and acoustic energy is not limited by weather and time. Vibration energy largely exists in motions of vehicles and airplanes, the human body, operating machines, etc. Acoustic energy can be easily found in noise from traffic, airplane engine, stadiums, etc. The ubiquitous nature of vibration and acoustic energies will provide great opportunities to a Correspondence to: Hui Fang Liew. E-mail: alicefang88@yahoo.com *School of Electrical System Engineering, University Malaysia Perlis, Pauh Putra Campus 02600, Arau, Perlis, Malaysia **School of Computer and Communication Engineering, University Malaysia Perlis, Pauh Putra Campus 02600, Arau, Perlis, Malaysia allow us to utilize such energies. Most importantly, the amount of vibration and acoustic energy collected over a period may be significant. Then, the extracted energy is converted into usable electric energy to power a battery-less system to overcome the frequent bat- tery replacement problem. As the piezoelectric-based micro-energy harvesting system is starting to replace the use of conventional battery systems, the use of micro-energy harvesting systems has increased dramatically in recent years. The ambient sources of energy harvesting produce mechanical energy, which is then con- verted to electrical energy using a transduction mechanism, such as electromagnetic (inductive) [15–17], electrostatic (capacitive) [18,19], or piezoelectric [20,21]. These piezoelectric cantilevers also deliberated as a useful transduction mechanism to convert the available vibrational energy from the surroundings into a func- tional form to power small electronic devices in current studies, as shown in Table I. Another advantage of the energy harvesting system is the reduction in the cost and problems involved during the changing of the batteries occasionally. To harvest energy such as ambient vibration, such harvesters are commonly designed to work at one frequency, i.e. their resonant frequency, which produces the maximum output voltage when the resonant frequency matches the ambient vibration frequency of the sources. This is the reason why piezoelectric transducers are chosen in this study, as they are the most efficient devices to implement such energy transformation and harvesting. Recent researchers have cited the above and focused on develop- ing optimal energy harvesting structures [24,25]. Nevertheless, the electrical outputs of these devices are often too small to power up electrical devices directly. Consequently, the methods of collecting and storing parasitic energy are also one of the important keys to acquire self-powered systems. Sodano et al. [26] investigated © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.