Transpiration Electrokinetic Power Generation and Zinc Ion Battery for Autonomous Leak Detection

Abstract

Every year $6 billion worth of water is lost in residential homes caused by undetected leaks creating nearly $20 billion in property damage annually in the U.S alone. These leaks also raise environmental concerns due to energy consumption in water treatment plants and declining freshwater sources. Additionally, water leaks can create extremely dangerous situations, having been the cause of data center fires, by undetected leaks traveling into battery rooms creating short circuits and extremely dangerous lithium battery fires. Because of these concerns researchers have developed many types of leak detection systems that have become commercially available for years by employing acoustic detection principles. While these detectors have shown success deployed in oil pipelines, they often suffer from low signal to noise ratios and poor sensitivity in water pipelines. Recently conductive carbon nanotube paper developed by Goodman et al. was applied as a leak detector with the ability to sense leaks as small as 45 µL by monitoring changes in the resistance of the paper as it gets wet. While this system is highly sensitive and uses low power it requires constant or intermittent monitoring and continuous power consumption needing a power line connection or battery that will often require replacement. While this application is great for industrial applications where wired connection and continuous power consumption are not a problem, it is not ideal for situations involving hidden pipelines where regular access is not possible, and the device needs to last for a very long time. To solve this problem the concept of a fully autonomous leak detection system was envisioned and the research presented here aims to develop leak activated power devices to operate wireless sensing applications. In this study two mechanisms of leak triggered power generation were developed for leak detection: an electrochemically enhanced transpiration driven electrokinetic power generator (TEPG) and a wick activated zinc air battery. Carbon nanotube paper was implemented as a TEPG using an active zinc anode to harness energy from moisture wicking and electrochemical processes, achieving a maximum theoretical power output of 1.4 mW. A single device could then be used to activate a latching circuit allowing a battery to operate an internet of things (IOT) device for WI FI signaled leak detection. To reach higher power outputs a zinc air battery was developed using recyclable paper-based materials to create a fibrous zinc anode and a wicking battery separator. The zinc anode was developed by embedding zinc microspheres into a carbon nanotube/paper based 3D structure that was also evaluated for the improvement of zinc ion batteries. A comparison of a typical zinc foil to the engineered anode showed an increase in battery capacity retention from 55% to 60% respectively. Lastly, a wick was developed to optimize the porosity of a bleached softwood paper to increase wicking speed, reaching a wick capable of transporting water 4 cm vertically in ~25 seconds. This wick was then combined with the developed zinc anode and smart paper to create a zinc air battery capable of wicking water to activate the battery in the event of a leak. By the developments presented in this dissertation two novel leak detection mechanisms were developed, capable of eliminating the need for continuous monitoring and thus external power sources, increasing the reliability and longevity of leak sensors.