Abstract

As Internet of things (IoT) infrastructures such as BLE beacon networks are gaining more attention, excessive battery consumption and subsequent maintenance operations have proven to be crucial drawbacks. As part of the green IoT trend, light energy harvesting BLE beacons have been proposed in the literature to reduce energy consumption from batteries and extend their lifetime. However, these devices do not consider adjusting the angle of the solar panel, which prevents them from maximizing their energy harvesting capability by adapting to various indoor lighting conditions. Furthermore, an algorithm to compute the angle to optimize the energy harvesting capability has not yet been investigated for small energy harvesting IoT devices. To address such issues, our paper first proposes a model of lighting conditions in an environment with multiple light sources, and based on the proposed model, we present an algorithm to compute the optimal angle of the solar panel that would maximize the harvested energy. Finally, we prototype an energy harvesting BLE beacon with an adjustable solar panel angle and conduct real-life experiments in three different locations with varying lighting conditions. The experiments prove that the proposed design can accelerate the energy storage charging rate by up to 570%.