A multi-scale solar receiver with peak receiver efficiency over 90% at 720 °C for the next-generation solar power tower

To reduce the receiver's energy loss at high temperatures for the next-generation concentrating solar power plant, a novel multi-scale receiver is proposed by combing fin-like structures in the macroscale and light-trapping coatings in the nanoscale. The fin-like structure can reabsorb the reflected solar energy while the light-trapping nanostructured coating can increase solar absorption and reduce infrared emissivity. A multi-scale numerical model is developed to evaluate the receiver's optical and thermal performance. It is found that the multi-scale solar receiver can achieve a receiver efficiency of 0.904 at the solar time of 12:00 on spring equinox. However, it is also found that the maximum film temperature of the leading-edge tube will exceed 800 °C, which may decompose the current nitrate salt. To solve this problem, a white coating is used for leading-edge tubes to reduce the temperature by decreasing the maximum heat flux. The results show that this method can effectively regulate the overheating of the leading-edge tube. The maximum film temperature was successfully reduced to less than 800 °C at nearly no expenses of the absorbed solar energy. The study provides a new sight to achieve a receiver efficiency of more than 0.9 for the next generation concentrating solar power plants.