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An optically transparent microstrip patch mounted on the surface of a commercially available solar module is proposed. The patch comprises a thin sheet of clear polyester with a conductive coating. The amorphous silicon solar cells in the module are used as both a photovoltaic generator and the antenna ground plane. The proposed structure provides a peak gain of 3.96 dBi in the 3.4-3.8 GHz range without significantly compromising the light transmission in the module. A comparison between copper and transparent conductors is made in terms of antenna and solar performance. The proposed technique is considerably simpler than previous integration approaches.
Introduction: There is increased interest in the integration of antenna and photovoltaic technologies for terrestrial applications owing to the smaller footprint and reduced costs, which improve the economic viability of renewable energy. Various integration arrangements have been reported where the solar cell provided a ground plane function for microstrip antenna elements, but this resulted in a reduced efficiency solar cell owing to partial shading by the opaque antenna [1, 2]. Materials that are both transparent and conductive such as AgHT-4, comprising a clear polyester film coated with nano-layers of metal oxides, have been developed [3].
A number of transparent antennas have been studied which show promising characteristics [4]. Recent work reports lower gain for transparent antennas compared to their copper counterparts; a transparent PIFA fabricated on a sheet of resistivity 20 V/sq yielded approximately 10 dB lower gain at 2.4 GHz [5], and a planar monopole UWB antenna on AgHT-4 was reported to have 5 dB lower gain owing to the inherent low conductivity of the transparent film [6].
This Letter presents a novel approach to solar antennas by mounting an optically transparent square microstrip patch made of AgHT-4 film on the surface of a glass covered solar module. This post-manufacture technique considerably simplifies the integration process by placing the radiator on the superstrate of commercially available solar modules. The transparent patch is fed using an electromagnetically-coupled microstrip feedline in a two-layer arrangement of glass-Perspex, which provides improved...