Hybrid RF-Solar Energy Harvesting Systems Utilizing Transparent Multiport Micromeshed Antennas

The design of a hybrid radio frequency (RF) and solar energy harvesting (EH) system utilizing a transparent multiport antenna for indoor applications is described. The system incorporates an eight-port transparent antenna, operating in the unlicensed 2.4-GHz band, and is constructed from transparent copper micromeshed planar conductor. The antenna is integrated on the top surface of a solar cell with rectifiers positioned underneath to form a hybrid RF-solar indoor EH system. A key advantage of this approach is that the surface area of the solar cell is reused for the antenna saving space. Another novelty is the use of a multiport antenna for increasing the RF harvested energy. It is demonstrated that with a light intensity of 360 lux, the solar cell can obtain 1.68-mW power while the rectenna can achieve an additional 4.8%-45.8% harvested power when the incident RF input power density is varied from 13.30 to 52.96 mW/m
²
. The transparent antenna achieves 72.4% efficiency and is one of the highest reported results. In addition, the rectifiers obtain 53.2% RF-to-dc conversion efficiency for an RF input power of -10 dBm. These results demonstrate that the proposed RF-solar energy harvester can increase harvested energy and provide energy diversity.