We demonstrate the first self-powered system driven by a nanogenerator (NG) that works wirelessly and independently for long-distance data transmission. The NG was made of a free cantilever beam that consisted of a five-layer structure: a flexible polymer substrate, ZnO nanowire textured films on its top and bottom surfaces, and electrodes on the surfaces. When it was strained to 0.12% at a strain rate of 3.56% S(-1), the measured output voltage reached 10 V, and the output current exceeded 0.6 μA (corresponding power density 10 mW/cm(3)). A system was built up by integrating a NG, rectification circuit, capacitor for energy storage, sensor, and RF data transmitter. Wireless signals sent out by the system were detected by a commercial radio at a distance of 5-10 m. This study proves the feasibility of using ZnO nanowire NGs for building self-powered systems, and its potential application in wireless biosensing, environmental/infrastructure monitoring, sensor networks, personal electronics, and even national security.

http://www.nanoscience.gatech.edu/paper/2011/11_NL_02.pdf

Self-powered system with wireless data transmission.

Harvesting unexploited energy in the living environment to power small electronic devices and systems is attracting increasing massive attention. [ 1–7 ] As the size of the devices has shrunk to the nanoor microscale, the power consumption also decreased to a modest level, i.e., the microwatts to milliwatts range. It is entirely possible to drive such a device by directly scavenging energy from its working environment. This self-powered technology makes periodic battery replacement or recharging no longer necessary and it is thus attractive for portable or inaccessible devices. Mechanical energy is a very conventional energy source in our living environment, with sources including the vibration of a bridge, friction in mechanical transmission systems, deformation in the tires of moving automobiles, etc., all of which are normally wasted. This form of energy is particularly important when other sources of energy, such as sun light or thermal gradients, are not available. A nanogenerator (NG) is designed to transfer such energy into electric energy by the piezoelectric effect. [ 8–14 ] The fundamental mechanism of a NG is that, when it is dynamically strained under an extremely small force, a piezoelectric potential is generated in the nanowire and a transient fl ow of electrons is induced in an external load, as driven by the piezopotential to balance the Fermi levels at the two contacts. For bicycles, cars, trucks, and even airplanes, a self-powered monitoring system for measuring the inner tire pressure is not only important for the safe operation of the transportation tool, but also for saving energy. In this work, a NG was integrated onto the inner surface of a bicycle tire, demonstrating the possibility for energy harvesting from the motion of automobiles. A small liquid-crystal display (LCD) screen was lit directly using a NG that scavenges mechanical energy from deformation of the tire during its motion. The effective working area of the nanogenerator was about 1.5 cm × 0.5 cm and the maximum output power density approached 70 μ W cm − 3 . Integration of many nanogenerators is presented for scale-up. Furthermore, the NG showed the potential to work as a self-powered tire-pressure sensor and speed detector. This work provides a simple demonstration of the broad application prospects of NGs in the fi eld of energy harvesting and self-powered systems.

http://www.nanoscience.gatech.edu/paper/2011/11_AM_06.pdf

A nanogenerator for energy harvesting from a rotating tire and its application as a self-powered pressure/speed sensor.

This paper presents a novel autonomous method for condition monitoring of rotating machines during operation based on radio frequency (RF) pulse transmission using energy harvesting from operational vibration. An energy harvesting unit is designed to generate and rectify the energy harvested from the machine vibration using Voltage Multiplier (VM) circuit and to store the energy into a capacitor. Then, this energy harvesting unit runs a smart system consisting of a microcontroller and the RF transmitter designed to send a pulse at specific capacitor voltage. A pulse-based condition monitoring approach is introduced which monitors the state of the machine during the operation. In order to estimate power output of the piezoelectric harvester for a realistic vibration signal, the Fourier Transform concept for signal decomposition is incorporated into the well-known electromechanical distributed parameter model. Using experimental data, performance of this autonomous condition monitoring system is tested for a water pump at different conditions. To do so, acceleration data from a centrifugal water pump are acquired with an accelerometer, which then decomposed into a series of harmonics using Fast Fourier Transform. Then using analytical distribute model, a bimorph energy harvester with two Piezoceramic layers is optimized to generate maximum power from the water pump vibration. Consequently, the condition monitoring of the water pump is performed using the presented pulse-based approach. Results of this study show that, the fault diagnosis can be performed autonomously by applying the pulse-based method presented in this work, and by using the piezoelectric harvesting device as an energy source.

A novel method for autonomous remote condition monitoring of rotating machines using piezoelectric energy harvesting approach

An attachable electromagnetic-energy-harvester driven wireless vibration-sensing system for monitoring milling-processes and cutter-wear/breakage-conditions is demonstrated. The system includes an electromagnetic energy harvester, three single-axis Micro Electro-Mechanical Systems (MEMS) accelerometers, a wireless chip module, and corresponding circuits. The harvester consisting of magnets with a coil uses electromagnetic induction to harness mechanical energy produced by the rotating spindle in milling processes and consequently convert the harnessed energy to electrical output. The electrical output is rectified by the rectification circuit to power the accelerometers and wireless chip module. The harvester, circuits, accelerometer, and wireless chip are integrated as an energy-harvester driven wireless vibration-sensing system. Therefore, this completes a self-powered wireless vibration sensing system. For system testing, a numerical-controlled machining tool with various milling processes is used. According to the test results, the system is fully self-powered and able to successfully sense vibration in the milling processes. Furthermore, by analyzing the vibration signals (i.e., through analyzing the electrical outputs of the accelerometers), criteria are successfully established for the system for real-time accurate simulations of the milling-processes and cutter-conditions (such as cutter-wear conditions and cutter-breaking occurrence). Due to these results, our approach can be applied to most milling and other machining machines in factories to realize more smart machining technologies.

/pdf/an-attachable-electromagnetic-energy-harvester-driven-57nxoon721.pdf

An Attachable Electromagnetic Energy Harvester Driven Wireless Sensing System Demonstrating Milling-Processes and Cutter-Wear/Breakage-Condition Monitoring.

Feasibility of a fully autonomous wireless monitoring system for a wind turbine blade

Purpose – The purpose of this paper is to demonstrate the feasibility of using kinetic energy harvesting to power wireless condition monitoring sensors. Design/methodology/approach – The system presented duty cycles its operation depending upon the energy being harvested. The harvested energy is stored on a supercapacitor and the system samples sufficient vibration data to enable an FFT to be performed at the receiver. Findings – The results of this study show it is perfectly feasible to power practical wireless condition monitoring sensors entirely from the vibrations of the machines being monitored. Originality/value – Energy harvesting techniques can be used to power wireless sensors in a range of applications. Removing the need for a battery power supply presents obvious environmental benefits and avoids the need to periodically replace batteries.

Stefan Kestermann

Papers

Self powered wireless sensors for condition monitoring applications