An energy harvesting system surveyed for a variety of unattended electronic applications

All energy-harvesting schemes require some form of “intermediate” storage – batteries or capacitors that reservoir energy harvested from the environment. There are a number of reasons for this requirement. Ambient energy fluctuates and intermediate storage smoothes out the impact of these fluctuations on the power delivered to a load. In addition, energy must be “conditioned” to be useful in a given application. It must be set to a certain voltage or made capable of delivering a desired current to load. In this article, a complete energy harvesting system including storage and conditioning electronics is described with a concentration on radio frequency (RF) harvesting. The system is capable of harvesting energy from a commercially available hand-held communication device, and exhibits an overall energy harvesting efficiency of 13.2%. Several potential applications have been investigated based on the performance of this system. Highlighted example applications include power sources for nodes in an architectural structural integrity monitor, and limb prosthesis.

► An ultra-thin, flexible battery can be re-charged at an exceptionally low voltage. ► A voltage boost converter with energy transfer efficiency as high as 40.5%. ► An RF energy harvesting system for a variety of applications with an overall efficiency of 13.2%. ► An investigation to potential applications including WSNs and a prosthetics system.