During last few decades, booming of wireless sensor network (WSN) require a reliable power source. Generally the power sources to these microsystems are the conventional battery. However, the battery has a finite lifespan and once extinguished of its power, these sensors must be retrieved and the battery replaced . With these sensors being placed in remote location it can become an expensive task to obtain and replace the battery. Therefore, it becomes necessary to provide them source, which can provide them energy reliably.
Technological developments in the MEMS industry have lead to miniaturization of many of the transducer systems. With this effort, the power consumption of these devices has been reduced to the order of W to mW level. These developments have opened a new source for supplying energy to these micro systems as an alternative to batteries, which have a finite life and are large in size. Researchers are working on alternative energy sources like solar, thermal, acoustics, and vibration.
These sources are clean and have theoretically infinite life compared to batteries. Considering implantable and embedded microsystems that should operate and survive on their initial energy supply, these ambient energy sources are attractive alternatives. Among these alternative sources, environmental vibration is particularly attractive because it is almost everywhere in our living environment and can be readily found in the environment in abundance. Through these transducers ambient vibrational energy can be efficiently converted into electrical energy.
In this report vibration based scavenging technique like piezoelectric and electromagnetic conversions are explained and how the ambient vibrational energy can be used to charge these microsystems through piezoelectric and electromagnetic transducer. Inspite of development of MEMS industry, there are some of technical limitation of vibration energy harvesting systems which are to be mitigated. Among these limitations, the ways to remove narrow bandwidth frequency limitation are discussed.