A KOH Solution Electrolyte-Type Electric Double-Layer Supercapacitor for a Wireless Sensor Network System

In this article, a supercapacitor is developed as a power supply for wireless sensor network (WSN) systems. The proposed supercapacitor is an electric double-layer capacitor (EDLC) that employs an environment-friendly electrolyte comprising potassium hydroxide (KOH) solution along with charcoal and a steel plate. The EDLC does not contain heavy metals and toxic substances and does not adversely affect the environment. Furthermore, the use of aqueous KOH as an electrolyte eliminated the possibility of ignition, ensuring the safety of the capacitor. The charcoal EDLC was fabricated and experimentally demonstrated. The supercapacitor was used as power supply for a WSN system, and a 10-W photovoltaic module was coupled with the charcoal EDLC for a 25-Wh power storage. The WSN system was continuously operated outdoors for 24 h with a power consumption of approximately 0.7 W. These results proved that the WSN system can be successfully operated in a continuous manner for 24 h by employing the charcoal EDLC as the power supply. At night, the WSN system consumed 35% (8.4 Wh) of the power that was stored in the charcoal EDLC. From these results, we can conclude that the proposed environment-friendly charcoal EDLC may be a solution to serve as a reliable and safe power supply for WSN systems.