Optical Flux Density Monitoring for External Central: Accuracy and Measurement Stability Receivers

Abstract

Most commercial solar tower plants use external tube receivers, which consist of hundreds of tubes arranged in multiple panels to form a circular receiver. To prevent overheating, the operation of these receivers requires regulation of both the incoming solar flux from the heliostat field and the molten salt mass flow through the tubes. Ground-based infrared cameras are typically used to monitor the temperature distribution on the receiver surface in real time to ensure optimal performance and prevent thermal damage. Direct flux density monitoring is an additional promising approach to enhance control, increase efficiency and to extend receiver life by providing more accurate real-time feedback on the incident solar flux. The here presented monitoring technique is based on radiometrically calibrated industrial cameras with telephoto lenses installed on the ground in the solar field, similar to the plant’s infrared cameras. Data has been collected with two cameras operating continuously for several months in an industrial-scale central receiver plant and analyzed for measurement stability and accuracy. The monitoring solution is non-invasive, requires low hardware expenditure, and is commercially applicable to existing as well as new central receiver plants.