Improving the performance of volumetric solar receivers with a spectrally selective gradual structure and swirling characteristics

The radiation loss at the front region of the volumetric solar receiver limits the solar to thermal efficiency of the receiver. With respect to the purpose of moving the highest temperature front of the receiver from the entrance to the inner position of the solar receiver, a spectrally selective gradual structure receiver with swirling characteristics is designed. A three-layer structure along the receiver depth, namely a radiation-transmitting layer, a radiation-absorbing layer, and a pressure-regulating layer, is designed to increase the radiation depth and suppress the pressure drop. The heat transfer and flow properties of the receiver are investigated, and a design rule of the gradual structure is summarized. The volumetric effect is achieved by using the gradual structure receiver. Such novel volumetric solar receiver with gradual structures achieves the volumetric effect, boosting the solar to thermal efficiency to 87%. Although parameters of each layer can be discretionarily selected based on the optical depth, higher porosity of the gradual structures allows for higher efficiency.