Contents lists available at ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy Signifcant power enhancement method of magneto-piezoelectric energy harvester through directional optimization of magnetization for autonomous IIoT platform Jae Yong Cho a,1 , Jihoon Kim b,1 , Kyung-Bum Kim a,1 , Chul Hee Ryu a , Wonseop Hwang a , Tae Hee Lee b , Tae Hyun Sung a, ⁎ a Department of Electrical Engineering, Hanyang University, Seoul 04763, Republic of Korea b Department of Automotive Engineering, Hanyang University, Seoul 04763, Republic of Korea HIGHLIGHTS • The directional optimization of magnetization was considered to enhance output power. • The harvester generated 39.2 mW as 2.13 to 784 times enhanced power. • The autonomous IoT and IIoT sensor systems were successfully constructed. • This method can signifcantly improve the energy harvesting using a magnetic feld. ARTICLE INFO Keywords: Piezoelectric energy harvester Magnetic feld Autonomous Wireless sensor network Power cable Lorentz force ABSTRACT Unlike previous piezoelectric energy harvesters that generate electrical energy from a magnetic feld according to the magnetic strength or magnetostrictive material, the proposed method achieves signifcant power en- hancement using directional optimization of magnetization. This method can serve as a ubiquitous autonomous energy source that converts a magnetic feld into usable electrical energy in a wireless sensor network for an (Industrial) Internet of Things (IIoT). The key approach in the proposed model is to increase of the Lorentz force by vertically adjusting the magnetic fux direction of a power cable and the magnetic direction of a tip magnet. In the simulation, a 3592 times higher y-axis Lorentz force was obtained in the vertical pole array, which resulted in about a 1.6 times higher output voltage. Then, we experimentally compared the electrical output performance of six diferent types of pole array according to the size and direction of the tip magnet. In a one-tip magnet (10 × 10 × 10 mm 3 ), the output power values were 2.34 mW (Vertical) and 1.23 mW (Horizontal) at 8 kΩ matching impedance. For two-tip magnets (20 × 10 × 10 mm 3 ), the output power values of the harvester were 39.2 mW (Planar-Vertical), 18.4 mW (Orthogonal-Vertical), 8.64 mW (Planar-Horizontal), and 0.05 mW (Orthogonal-Horizontal) at 5 kΩ matching impedance. It was found that the power generation difered by 2.13 to 784 times. With this method of power enhancement using multi-disciplinary research, we successfully con- structed autonomous IoT and IIoT sensor systems for smart homes, smart buildings and smart factories. 1. Introduction A keyword in the era of the fourth industrial revolution is the Internet of Things (IoT), along with the Industrial Internet of Things (IIoT), which enables interactive networks between devices, vehicles, home appliances and other items embedded with electronics, software, sensors, actuators, etc [1,2]. To realize the IoT world, one of the key technologies is energy management for powering many diferent sen- sors [3,4]. In particular, for energy management, many studies have been carried out on self-powering, battery-less, autonomous devices in energy harvesting technology [5,6]. Energy harvesting is a self-powering, battery-less, autonomous so- lution that is accomplished through scavenging ambient energy from external resources, such as the sun, wind, water, etc., and converting https://doi.org/10.1016/j.apenergy.2019.113710 Received 25 May 2019; Received in revised form 4 August 2019; Accepted 5 August 2019 ⁎ Corresponding author. E-mail address: sungth@hanyang.ac.kr (T.H. Sung). 1 Contributed equally to this work. Applied Energy 254 (2019) 113710 0306-2619/ © 2019 Elsevier Ltd. All rights reserved. T