Harvesting Vibration Energy: Technologies and Challenges

The battery is probably the most commonly used power supply for electronic devices. However, batteries are gradually becoming insufficient for powering many of the emerging devices that have started to dominate our lives, such as portable electronics, wearable smart devices, and wireless sensor networks. The general reason for this insufficiency is the high cost of replacing the batteries. Take the wireless sensor network as an example; the sensor device might not be easily accessible and the number of the sensor nodes is often very large (more than thousands) [1]. One of the major costs of battery replacement is the loss of productivity due to the machine downtime and the effort to reintegrate the offline device into the network. In some critical applications, preventive battery replacement is often practiced owing to the difficulty of determining the state of charge of a battery [2], further increasing the frequency of battery replacement. In addition, the cost of battery replacement is further boosted by the cost of labor and inventory, as well as the cost of the equipment and the consumables needed. Perpetua Corporation has estimated that the cost for battery replacement per component for certain industries can be as high as US$550 [3]. Furthermore, there is a growing concern over the recyclability of batteries and their disposal-related environmental issues. Therefore, it is ideal to gain the energy for electronic devices from the environment in which they operate. Vibration-such as from human motions, machinery vibrations, vehicle vibrations, and building vibrations-is an attractive energy source for powering those electronic devices owing to its abundance in the environment.