A concentrated sunlight energy wireless transmission system for space solar energy harvest

Advancements in spacecraft formation and space solar power plant technologies promote wireless energy transmission among satellites and the Earth. Although microwave-based, laser-based, and sunlight-based wireless energy transmission technologies have been reported previously, none of them have been practically deployed because of major limitations. In this paper, a concentrated sunlight energy wireless transmission system (CSEWTS) using single plano-convex lenses to harvest space sunlight and a single corresponding optical fibre bundle (OFB) to realize flexible energy transmission is schematically developed and its prototype is established experimentally. This system utilizes sunlight as the transmission media to avoid intermediate energy conversion and where energy efficiency can be enhanced compared to microwave-based or laser-based energy wireless transmission. Furthermore, the OFB-based CSEWTS can lighten the mirror-based system, which was developed previously. Various effects of optical coupling, condenser outline in the energy receiver, smog, distance, and bending were experimentally or theoretically investigated. An optimized coupling incident angle into OFB of 18 degrees was attained theoretically and validated experimentally where an improvement of 19.9% in system efficiency was acquired from a wrong angle to an optimal one. Besides, aspheric lenses were experimentally proved to be more appropriate to condense sunlight where a 16.5% - 19.5% enhancement was obtained. In addition, lens coating, condenser outline in the energy receiver, smog, and distance effects were also analyzed. Smog harms energy transmission which casts shadows on its space-Earth application. Energy transmission to a no-cloud area is the only probable option. The developed technologies can also be used in solar sail spacecraft, contributing to global carbon neutrality and clean aerospace flight.