Design and Evaluation of the Compact and Autonomous Energy Subsystem of a Wave Energy Converter

Abstract

This paper presents the results of the design process focused on the development of the energy subsystem (ES) of a wave energy converter (WEC). The ES is an important electrical part that significantly affects the energy reliability and energy efficiency of the entire WEC device. The designed ES was intended for compact WECs powering IoT network devices working in the distributed grid. The developed ES is an electronic circuit consisting of three cooperating subsystems used for energy conversion, energy storage, and energy management. The energy conversion subsystem was implemented as a set of single-phase bridge rectifiers. The energy storage subsystem was a battery-less implementation based on the capacitors. The energy management subsystem was implemented as a supervisory circuit and boost converter assembly. The designed ES was verified using the physical experiment method. The model experiment reflected the operation of the designed ES with a piezoelectric PZT-based WEC. The experimental results showed a 41.5% surplus of the energy supplied by ES over the energy demanded by the considered load at a duty cycle of ca. 6 min—37.2 mJ over 26.3 mJ, respectively. The obtained results have been evaluated and discussed. The results confirmed the designed ES as a convenient solution, which makes a significant contribution to the compact WECs that can be applied among others to a distributed grid of autonomous IoT network devices powered by free and renewable energy of sea waves. Finally, it will also enable sustainable development of mobile and wireless communication in those maritime areas where other forms of renewable energy may not be available.

Design and Performance Evaluation of the Energy Subsystem of a Hybrid Light and Wave Energy Harvester

“…The involved device consists of a 2.71" monochrome electronic paper display (e-paper) [32] and an ARM Cortex-M4 microcontroller enabling LoRa (longrange) modulation [33]. This IoT device and its features, including energy consumption, are detailed in [26,34]. According to the experiments carried out there, its energy demand per operating cycle is equal to 26.3 mJ, wherein, apart from the idle part of the cycle, the communication and actuation consume the amount of energy 21.5 mJ in 7.1 s, i.e., 3.03 mW of mean power [26].…”

“…This converted energy is stored in tantalum capacitors C1-C6. The process of wave energy conversion was reported in [26,34]. The light energy harvested with the use of PVP is applied to the I N3 terminal and is also collected and stored in a battery-less manner in C1-C6.…”

“…The light energy harvested with the use of PVP is applied to the I N3 terminal and is also collected and stored in a battery-less manner in C1-C6. Energy management is realized with the use of supervisory circuit IC3 with RESET output, low-voltage input boost regulator IC4, low dropout (LDO) regulator IC5, P-channel enhancement mode MOSFET transistor Q1, and their circuits passive components: diodes D, capacitors C, and resistors R. The electronic components applied to the ES are detailed including the manufacturers' parts numbers in [34]. The electronic circuit designed and implemented by the first author operates as follows.…”

“…This resulted in a deformation of the membrane with an amplitude of 3 mm, corresponding to 6 mm peak-to-peak deformation. The model experiment on wave energy harvesting was performed in line with the method detailed in [34]. A PVP made of polycrystalline silicon was connected to the I N3 terminal.…”

“…In the experiments, the V S voltage of the energy stored in C1-C6 and the V O voltage supplied to the load were measured using an AGILENT TECHNOLOGIES DSO-X 2004A digital oscilloscope. The energy stored in the C1-C6 capacitors can be calculated as E H (1), wherein C S is the total capacitance of the energy storage equal to 6 mF [34].…”