Batteryless Bluetooth Low Energy Prototype With Energy-Aware Bidirectional Communication Powered by Ambient Light

Abstract

With the emerging deployment of Internet of Things devices, the industry is moving toward batteryless, maintenance-free, and sustainable solutions. Energy harvesting from ambient sources becomes crucial to support the uninterrupted execution of such applications. We choose the Bluetooth Low Energy (BLE) mesh network to analyze a batteryless node using the BLE Low power node (LPN) feature. We develop a prototype using a mini photovoltaic solar panel for indoor light harvesting using sunlight or a light bulb to power the BLE LPN. Due to the unpredictability of energy harvesting and the use of a small capacitor instead of a battery, the BLE LPN’s power can become intermittent. This causes the device to frequently switch between the ON and OFF states as it is unaware of its available energy while trying to perform scheduled tasks. In contrast, an energy-aware LPN can try to avoid the OFF state. With the knowledge of the capacitor voltage, it can proactively delay the execution of upcoming sensing or communication tasks and provide some time to recharge the capacitor while consuming a minimum amount of energy by switching itself to the SLEEP state. This article presents the developed prototype and evaluates an energy-unaware and -aware batteryless BLE LPN communicating uni-directional downlink only or bi-directional for different capacitor sizes at different light-harvesting powers. The experimental results conclude that the energy-aware batteryless LPN performs better for both uni- and bi-directional communication with improved DL data latency up to 74% and avoiding restarts.