Advancing Low-Power Self-Sustaining IoT Sensors Through CdTe PV-Driven LoRa Communication

This paper explores the practical application and subsequent performance comparison of second-generation solar cells such as cadmium telluride (CdTe) and amorphous silicon (a-Si) photovoltaic (PV) cells to energize an ultra-low power wireless LoRa-based indoor internet of things (IoT) system. The significant advantages of the second-generation panels in terms of reduced capital cost, high-temperature performance, and good adaptation to low-light density compared to first-generation PV panels make them suitable for indoor IoT devices to provide better communication range and lifetime. A fully-functional CdTe PV-powered remote temperature and humidity station is designed and developed with a maximum effective communication range of 50 meters. The CdTe PV module used has an efficiency of 16%, which generates an output power of 3. $3mW$ with an effective area of 215cm ² under a 200 lux (1x) indoor environment. This module powers an ESP32-based LoRa node which operates in either normal or deep-sleep mode. The LoRa node consumes $165\mu W$ and $260mW$ of power while operating in deep-sleep mode and normal mode, respectively. With the implementation of a quiescent buck-boost converter and a supplementary energy storage system (ESS), the developed system can sustain the operation without any light at night. The developed prototype shows that compact and affordable PV cells are capable of providing continuous power to fulfill the demanding energy requirements of autonomous LoRa-based IoT systems, thus enabling fully autonomous operation for ultra-low power applications.