Engineering of contact interface, device structure, sensor system of wind based triboelectric energy harvester

Abstract

Energy harvesting generates electrical energy from various ambient environments energy sources such as vibration, water, wind, etc. Moreover, there are various energy harvesting methods to generate electrical energy from electromagnetic, electrostatic, piezoelectric properties. In recent, triboelectric based energy harvesting has been actively studied. Triboelectric energy harvester (TEH) is getting attention, because of high output power, simple fabrication, a wide material spectrum, and low-cost fabrication process. Moreover, TEH collects various mechanical energy sources in various environments. Among the various environment energy sources, wind is the one of the cleanest, sustainable, semi-permanent source for energy harvesting.

In the first part, we report a simple and effective route to forming nanostructures on the metal surface was proposed, using a water-assisted oxidation (WAO) process. The one-step WAO process requires only hot water without any complicated equipment and treatment. Using the WAO process, densely packed micro and nanostructures were successfully formed on three target metal surfaces: aluminum, copper, and zinc. The output power of the TEH was enhanced after the nanostructure formation because of the increased contact area. The influence of the process conditions on the nanostructure morphology was additionally analyzed to maximize the output power. The simple and low-cost WAO process is advantageous in terms of practicality.

In the second part, we demonstrated a multi direction tied wind based triboelectric energy harvester (MD WTEH) with a single stack structure, which stably collects wind energy blowing from all directions. The proposed MD WTEH is composed of two metal electrodes at the top and the bottom with an intercalated polymer membrane, which is driven to alternately flip and flop between both metal electrodes by an external wind. The overall shape is square, and the polymer membrane is supported by spacers at 4 corners. Structural parameters such as the thickness of the polymer membrane, the length or width of the square device, and the height of the spacers were optimized to investigate the relation between wind frequency and the amount of transferred charge. The analyzed data were supported by numerical simulations. By providing in-depth understanding this study can contribute to the development of general WTEH s.

In the third part, we reported self-sustained wind speed sensor system (SSWSSS) operation with onmi-directional wind based triboelectric energy harvester (OD WTEH). The proposed OD WTEH provide the both signal for sensing and energy for storing. The SSWSSS composed of wind speed sensor part and energy storage part. In the wind speed sensor part, it count the frequency of electrical signal from OD WTEH which cross the reference voltage. As wind speed is increased, frequency of electrical signal from OD WTEH also increased. Therefore, wind speed can be sensed from linear correlation between each other. In the energy storage part, it storing the electrical energy from OD WTEH. For transferring maximized power the partial energy from OD WTEH control the rectifier voltage, ant the rest energy stored to capacitor or battery. These self-sustained sensor system was operated as planned, and it will be guideline for self-powered sensor system.

In the last part, we reported about output performance of the multi direction tied wind based triboelectric energy harvester (MD WTEH) in various environment. For practical using, the TEH device will be exposed to various environments, such as low or high humidity, low or high temperature, and dusty air. And these environment factors are greatly affected to power performance of the TEH. Therefore, we studied about MD WTEH operation in various environment. We newly designed enclosed measurement setup with aluminum shielding box for measuring humidity, temperature and dust effect. The output performance of the MD TEH was degraded in high relative humidity, high temperature, and any dusty conditions. The relative humidity and temperature are reversible environment factors in output performance of the MD WTEH. However, the dust can be irreversible environment factor in output performance of the MD WTEH