Environmentally friendly electrolyte type electric double layer supercapacitor for wireless sensor network system

Abstract

In this study, we report the development result of a supercapacitor as a power supply system for wireless sensor network (WSN) systems. Our supercapacitor is an electric double layer capacitor (EDLC) using an environmentally friendly electrolyte, which is made of a potassium hydroxide (KOH) solution and a charcoal and a steel plate. The EDLC using a charcoal, a steel and KOH as element materials (charcoal EDLC) does not contain heavy metals and a toxic substance. The charcoal EDLC, even if it is discarded by failure, does not almost influence the environment. Moreover, since a KOH solution is used for the electrolyte, there is no fear of ignition and so it is safe. We fabricated the charcoal EDLC and performed demonstration experiment. In the demonstration experiment with a WSN system, as power supplies, we used a 10 W solar cell and a charcoal EDLC with the power storage of 25 Wh. The WSN system continuously operating for 24 hours with the power consumption of about 0.7 W outdoors was used in the experiment. As a result, we could confirm that the WSN system was operated successfully even in the nighttime through the charcoal EDLC. In the nighttime, the WSN system consumed 35 % (8.4 Wh) of power stored in the charcoal EDLC. We conclude that our environmentally friendly charcoal EDLC is one of solutions for a reliable and safe power supply for the WSN system.