Energy Harvesting from Earth's Radiation for Internet of Things Applications

This paper aims to design an array of infrared nanoantennas to collect energy radiated from the earth. The Earth radiates circularly polarized infrared waves with a frequency around 30 THz (wavelength um). A bowtie antenna is designed using the CST Studio Suite. The antenna bandwidth extends from 18 to 36 THz (0.66 fractional bandwidth). This bandwidth enables the antenna to capture 0.7 of the energy incident upon it from Earth. The angular 3dB beamwidth is 134 degrees, which enables the antenna to capture energy coming from diverse directions and avoids using any tracking system. Since the bowtie antenna is linearly polarized, two crossed bowtie antennas are used to capture all incident energy. The distance between elements in the array is taken to be half a wavelength to reduce mutual coupling. It is found that one square meter contains 40e9 antennas, which give 140 W of harvested power.Exploration of suitable materials and fabrication techniques, and integration with low power IoT networks is a future work plan.