Experimental Observations on Hybrid RF-Solar Energy Harvesting Circuit for Low Power Applications

Abstract

This paper investigates the performance of hybrid RF-Solar harvesting circuit that can simultaneously harvest power from solar and radio frequency (RF) sources readily available in the surrounding environment. The proposed work utilizes stand-alone RF and solar harvester circuits to realize a hybrid harvester circuit. The stand-alone RF harvester circuit is a dual-band multi-stage harvester that has been designed to work at GSM 900 MHz and Wi-Fi/WLAN bands. The standalone solar harvester circuit comprises of a solar panel with inbuilt rectifier circuit. The output DC voltage is obtained across the load of the two harvester circuits. The load of the two stand-alone harvester circuits are connected in series to provide DC voltage addition ensuring maximum power transfer at the load resistance of the hybrid harvester circuit. The performance of hybrid circuit has been evaluated for outdoor environment at different times over a day. Even when there is a sudden drop in power coming from standalone RF or solar harvester circuit, the power of hybrid harvester circuit does not fall abruptly due to backup from other dominant harvester circuit. This avoids sudden drop in power requirement by a device ensuring its continued operation and safety.