RF Energy Harvesting

This paper presents the results of a project in RF Energy Harvesting for scavenging energy from the ubiquitous radio-frequency (RF) electromagnetic waves. Such a device can be very useful to charge mobile phone in jungles and in remote areas or where the electric utility is not available or not reliable. In comparison to other methods of energy harvesting, RF has the smallest energy density and therefore poses big challenges. Based on the experiments, we find that the most efficient range of operation lies in the medium wave frequency band: 531-1,611 kHz. The experiment uses an antenna, LC tuning circuit, 5-stage of Villard voltage multiplier circuit and super-capacitor as energy storage. The experiment could harvest a RF signal from 1-mile distant transmitter that generates a field-strength of 103.724 dBu at the location of the receiver. The maximum charge on storage capacitor achieved was recorded 2.8V. A limitation of using this band of frequency is the large size of antenna that limits its portability.