Using Weak Light Sources to Power Sensor Nodes for Sustainable IoT

This paper introduces a novel Internet of Things (IoT) node design, WISE, which can operate autonomously using weak light sources, e.g., indoor lights or weak sunlight. As IoT systems are increasingly deployed, a fundamental question is drawing attention: How can we sustainably power the vast number of IoT nodes? Traditional batteries are insufficient due to their limited lifetime and high replacement costs in scalable IoT systems. Energy harvesting thus recently emerged as a promising solution, where nodes can harvest enough energy from outdoor sunlight. Regarding recent works, this paper focuses on an important but understudied segment of deployment scenarios that mainly contain weak light sources, e.g., indoors where lamps are the main light source. Our key innovation for powering nodes using weak light sources is a new node architecture featuring a timing supply control part, reducing quiescent current to nano-ampere (nA) levels, and optimizing energy use. We further propose a scheme to optimize the selection of hardware components in customizing WISE nodes, according to different design requirements, and an energy-aware scheduling method. We develop and test three WISE node configurations in real-world environments, achieving substantial improvements in communication rate and energy efficiency compared to the state-of-the-art node designs.