Selective Emitters Design and Optimization for Energy Harvesting Using Rectennas

Recently, rectennas have drawn attention as an attractive option to harvest radiative thermal energy from the sun and terrestrial thermal sources. In order to achieve the potential high energy conversion efficiencies by this technology, matching conditions between the incident electromagnetic wavelength and the rectenna characteristic length must be satisfied. Therefore, a selective emitter is a key element in high efficiency rectennas. Photonic structures were designed for selective emission using the transfer matrix method and genetic algorithm optimization. Two types of emitters were developed using aluminum as the supporting substrate. This paper presents narrowband selective emitters with a peak emissivity at 9.45 μm made of alternating layers of Al₂O₃ and SiO₂ on a substrate, and broadband selective emitters made of alternating layers of Al₂O₃ and SiC on a substrate with a high emissivity band between 9.5 μm and 10.5 μm.