Flux Density Measurement for Industrial-Scale Solar Power Towers Using the Reflection off the Absorber

Flux density measurement is precious for operation as well as for performance testing of solar power towers. The radiation reflected off the absorber can be used for this task. The disturbance of the plant operation is close to zero. Besides a digital camera, a computer and optionally a radiometer, almost no further hardware is required. That's why it is suitable for industrial-scale receivers. This paper presents several enhancements for this measuring process. Especially the so-called scan method appears promising, because it leads to significantly smoother flux density results compared to formerly presented methods. The article also deals with the determination of the irradiation's directional composition as well as with calibration routines. The proposed innovations were demonstrated at the Juelich Solar Tower with its open volumetric receiver and are likely to be suitable for external tube receivers, too. A plausibility check using CFD simulations was carried out. In summary, the discussed techniques show promise for future application at large-scale solar towers.