Modelling Theory and Applications of the Electromagnetic Vibrational Generator

There is rapidly growing interest over the last decade on the topics of energy harvesting devices as a means to provide an alternative to batteries as a power source for medical implants, embedded sensor applications such as buildings or in difficult to access or remote places where wired power supplies would be difficult [1-13]. There are several possible sources of ambient energy including vibrational, solar, thermal gradients, acoustic, RF, etc that can be used to power the sensor modules or portable electronic devices. The most promising ambient energy sources of these are solar, thermo-electric and vibrational. A significant amount of research has already been done in this area over the past few years and several energy scavenger products are already available in the market such as the solar calculator, thermoelectric wristwatch and wireless push button switches etc. The Solar energy is a mature technology and represents a very straight forward approach to generate energy from ambient light. However, solar cell is not cost effective and devices using solar cell need larger areas which would not be compatible with small MEMS powering. Furthermore sufficient sunlight is necessary which also limits the application areas. In thermoelectric generators, large thermal gradients are essential to generate practical levels of voltage and power. It would be very difficult to get more than 10°C in a MEMS compatible device. On the other hand, vibrational energy scavenger could be a reliable option for autonomous sensor modules or body-worn sensor, in automotive, industrial machine monitoring or other applications where ambient vibrational energy is available. This vibrational energy can be converted into electrical energy using three different principles: electromagnetic, electrostatic and piezoelectric.