Title: INFRARED ENERGY HARVESTING USING NANOANTENNA ARRAYS

Program: Electrical and Computer Engineering PhD

Committee Chair: Eklas Hossain

Committee: Eklas Hossain, Kurtis Cantley, Said Ahmed-Zaid

Abstract: This report presents research on development and comparative analysis of two infrared energy-harvesting systems, which are proposed as sustainable alternatives to conventional renewable energy sources. A comprehensive hardware evaluation was conducted to evaluate the impacts of extreme weather conditions on the performance and efficiency of photovoltaic (PV) modules. A mini monocrystalline solar cell was subjected to a range of environmental stressors, including extreme heat, high humidity, wildfire smoke, and combinations of these severe conditions, using a controlled, enclosed-chamber setup. Experiments showed that efficiency of PV cells degraded drastically when subjected to escalating environmental stress levels. Most severe decline of 55.82% occurs during the simultaneous presence of extreme smoke and high humidity. These findings establish clear quantitative loss factors that serve as predictive tools for solar farm operators, enabling improved forecasting of real-world energy output and supporting the formulation of robust mitigation strategies for climate resilient solar energy systems.

The first proposed energy harvesting system targets terrestrial infrared radiation emitted by the Earth’s surface, corresponding to a wavelength of approximately 10 µm. In this system, a bowtie nanoantenna array was designed and optimized using CST Studio Suite to effectively capture circularly polarized infrared waves with a dominant frequency of around 30 THz. The resulting antenna achieved a broad bandwidth extending from 18 THz to 36 THz, representing a fractional bandwidth of approximately 0.66. This bandwidth allows the structure to harness nearly 70% of the incident radiative energy. The 3-dB beamwidth of 134? enables reception from a wide range of incidence angles, eliminating the necessity of mechanical tracking systems. Owing to the linear polarization characteristics of the bowtie configuration, two crossed bowtie antennas were employed to capture the complete set of circularly polarized waves. To minimize mutual coupling between array elements, the inter element spacing was maintained at approximately half the operational wavelength. Theoretical modeling indicated that a one-square-meter array could accommodate approximately 4 × 1010 antennas, collectively capable of harvesting 140 W of power.
The second system collects randomly polarized infrared waves radiated from the Sun with a wavelength starts from 0.7 µm. A bowtie antenna is designed using the CST Studio Suite. The antenna bandwidth extends from 200 to 350 THz (fractional bandwidth 55%). This bandwidth enables the antenna to capture 200 W/m2 of power density. Power density from the Sun at the equator is 1000 W/m2 . The angular 3 dB beamwidth is 140 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 (0.5 µm) to reduce mutual coupling. One square meter contains 4 × 1012 antennas, which give 142.8 W of harvested power. 4-element antenna array is simulated, and it is found that the bandwidth of the array increased to extend from 270 - 500 THz. The received power per square meter increased to be 214.4 W.