Design and Modeling of a Soil-Based Energy Harvester for Underground Wireless Sensor Nodes
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Date
2020-04-28
Authors
Bhuyian, Md Rubayatur
Journal Title
Journal ISSN
Volume Title
Publisher
University of Waterloo
Abstract
Wireless Sensor Networks (WSN) have emerged as a reliable and viable solution for monitoring complex large-scale strategic assets that are placed in harsh and hostile environments. Some of the major application areas include environmental monitoring, disaster management, infrastructure monitoring, and security. A large number of such infrastructures are buried underground and have a limited service life. It is important to assess their condition throughout their life cycle to avoid possible catastrophic failures due to their deterioration. Monitoring such infrastructures creates a complex wireless sensor network with thousands of sensor nodes that are required to be functional with zero maintenance for 10∼20 years once deployed. Powering such Wireless Sensors (WS) for decades is a key challenge in the design and operation of WSN.
Sacrificial Anode Cathodic Protection (SACP) technique is a well-known technique for corrosion protection. In this technique, steel structures are protected from natural corrosion by enabling an externally connected anode material to deplete over time. To model the depletion rate of the anode for replacement purposes, human readers visit each Sacrificial Anode (SA) site to take voltage and current measurements once a month. This approach is expensive and prone to human errors. Moreover, there is a large number of such sites in a city. The main challenge in using WSN in such scenarios is providing a reliable source of energy to power the sensor nodes. As the majority part of the structure is buried underground, traditional renewable energy sources, such as solar, wind, and thermal do not offer any lucrative solution due to their requirements for additional setup, space, and periodic maintenance.
Thus, an underground soil-based energy harvester using the existing setup has been carefully researched, designed, developed, and implemented as part of this research. The technique exploits the electric current flowing from the cathode to the anode to energize the sensor nodes. The prototype developed in the lab uses the harvested energy from soil to power sensor nodes to communicate the data to the cloud. To develop and implement the prototype two test benches were set up, one indoor and the other outdoor. The outdoor setup facilitated the experiments under varying weather conditions and with the indoor one, experiments were conducted under a controlled environment.
The prototype developed in the lab will be buried underground for security purposes, as a result, data needs to be transmitted through the soil between nodes. Radio Frequency (RF) transmission through the soil is one of the main challenges for this project. Various parameters affect RF signal attenuation in soil (i.e. transmission frequency, burial depth, soil dielectric properties, etc.). In this research, we have investigated, tested and implemented several wireless technology modules such as Global System for Mobile Communications (GSM), Wireless Fidelity (Wi-Fi), Zigbee, Narrow Band-Internet of Things (NB-IoT) to meet the desired requirements.
The research also outlines the complete operation of the developed module. In addition to that, to estimate the energy harvesting rate, energy harvesting efficiency and to analyze the charging behavior several experiments were conducted to obtain the Current-Voltage (I-V) and the Power-Voltage (P-V) characteristics of the energy source. This study is later used to develop a model for the energy source. The model is validated with measurement data from the field trials. This developed model is helpful to easily realize a system and can be useful to solve numerical problems, find information about operating point or to analyze a circuit.
Description
Keywords
Energy Harvesting, Wireless Sensor Network, Cathodic Protection, Corrosion Monitoring