Numerical investigation and comparison of tubular solar cavity receivers for simultaneous generation of superheated steam and hot air

Solar cavity receivers are a crucial technology to transform solar energy into easily usable thermal energy. Various cavity receiver structures employing helical absorber tubes were investigated to provide either super-heated steam or hot air efficiently. However, few studies have focused on receivers that generate both hot fluids simultaneously. The simultanoues generation can lead to a more compact and cheaper system, and can be used for applications such as a high-temperature electrolysis to produce green hydrogen or syngas. In our study, three different tubular solar cavity receivers were proposed and numerically investigated. Each receiver consists of three different processes: (1) water evaporation, (2) superheating steam, and (3) heating air. The 1D-3D model developed in our previous study was used to investigate the various aspects such as lamp-to-thermal (solar simulator was used as a light source) and exergy efficiencies. The numerical results have proven that the receiver employing both cylindrical and conical helical tubes can obtain the highest lamp-to-thermal (67.0%) and exergy efficiencies (46.9%). A parameter study was also conducted based on the chosen optimal receiver. The obtained results can become a basis for further implementation, and especially the use in high-temperature electrolysis could become crucial in a future energy system.