Solar‐Charged Supercapacitor Powering of Wireless Sensor Network Nodes for Environmental Monitoring

This work describes a novel strategy for designing and building a solar energy harvester that can continuously and autonomously supply power to wireless sensor nodes for long‐term applications. The system depends on solar‐charged supercapacitors instead of batteries and is designed to require very low solar radiation; for a 12 V 1.5 W rated photovoltaic panel, the minimum solar radiation was 55 W/m 2 . Consequently, the system is efficient even on cloudy days and under scarce sunlight conditions. On average, considering sleep and active cycles, the node consumed a total of 0.28 mW. More than a year of consecutive field experiments was conducted in a variety of environments, including the understory of dense vegetation, confirming the feasibility and long‐term viability of the harvester system in challenging environments. Two 3 V 50F supercapacitors connected in series can power the system in the absence of sunlight for 5 days. To enhance reliability, emergency backup coin‐cell batteries are provided. The proposed solution guarantees that the system is always powered, reducing data loss due to power outages as well as the number of site maintenance visits. Supercapacitors offer longer lifetime and faster charging than batteries, while having a higher cost and lower energy density. However, the system footprint is not larger than a battery‐based system, and life‐cycle cost analysis shows that higher costs are offset for long‐term deployment.