A Report On
As a future energy source
Submitted by: Nikhil Gupta (5th Sem)
Mechanical Engg. Dept., JEC,Jabalpur
The Future Smart House is going to have a large number of sensors and microelectronic devices located throughout the house. These devices will need a clean, reliable source of energy that won’t need constant maintenance. The goal of this report is to get awareness about the piezoelectric energy sources to provide power to certain applications in the house. Initially the researchers were planning to create an energy scavenging floor that used piezoelectric transducers to harvest wasted energy in the foot strike of a human being. In consideration of the high cost and minimal power output of these piezo-sources, it seems more feasible to create small, localized energy sources rather than one large unified system. This idea has lead to several potential applications. The first is to combine a piezoelectric power source with sensors such that there would be no need to ever change the batteries in these sensors. The next application is to use piezoelectric cable throughout the floors of the house as a means of tracking. The final application is to combine piezoelectrics with a device to eliminate vibrations in household appliances.
So generally Piezoelectric Energy Harvesting is based upon the piezoelectric effect.The essence of the piezoelectric effect works as follows: by applying a mechanical stress to a crystal, one can generate a voltage or potential energy difference, and thus a current. Also by applying a current to a piezoelectric one can stress or strain the material. The mechanical stress can be supplied by any source. But with so many people walking around from place to place, why not harness that kinetic energy to power stuff, right?
Piezoelectric materials exhibit the unique property known as the piezoelectric effect. When these materials are subjected to a compressive or tensile stress, an electric field is generated across the material, creating a voltage gradient and a subsequent current flow. This effect stems from the asymmetric nature of their unit cell when a stress is applied. As seen in Figure 1, the unit cell contains a small positively charges particle in the center. When a stress is applied this particle becomes shifted in one direction which creates a charge distribution, and subsequent electric field. These materials come in several different forms. The most common is crystals, but they are also found as plastics and ceramics.
Fig.1: Lead Zirconate Titanate unit cell
There are several companies and research institutes throughout the world who are focusing on finding useful applications for piezoelectric energy sources. Several years ago a project was done at MIT entitled, “Energy Scavenging with Shoe-Mounted Piezoelectrics.” In this project the researchers lined the bottom of a shoe with piezoelectric transducers and saw what kind of power they got out of it. They eventually attached an RF-transmitter to the shoe that was powered by the piezoelectrics. The two materials they used were polyvinylidene fluoride (PVDF) and lead zirconate titanate (PZT). Their initial results were that the PVDF material produced 1.3 mW per foot strike and the PZT produced around 8.4 mW. They went back and tried numerous other approaches but they were confined to working with the limitation of a shoe. In this report they...