Effects of clouds on thermal performance of the receiver in the concentrated solar power tower system

For the concentrated solar power tower system, the cloud cover blocks the heliostats, and the concentrated heat flux fluctuates, resulting in thermal stress and thermal fatigue failure of the receiver. To mitigate the effects of the clouds, a method that could project cloud shadows onto a heliostat field was proposed. Then, we investigated the effects of the cloud shadows on the heliostat field and thermal performance of the receiver. The results indicated that the cloud features had a huge impact on the performance. The concentrated heat flux fluctuated when the cloud shadows varied, bringing challenges to the safe operation of the receiver. With the same shadow ratio, the heliostats blocked might be different, so that the concentrated heat flux distribution varied. The shadow ratio could be used to predict energy production of the receiver under cloudy conditions, but it was not reasonable for evaluating the safe operation of the receiver. The moving cloud cover resulted in fluctuation of the concentrated heat flux, brought risk of thermal fatigue for the tubes. For a shadow ratio reduction of 22.51%, the maximum concentrated heat flux could increase by 343.89%, and the tubes might suffer from severe thermal shock loads. If the transmittance was lower than 0.6, the concentrated heat flux distribution was significantly affected. For the safe operation of the receiver, it is necessary to monitor the cloud features, and an advanced cloud detection method should be developed.