Durability testing of parabolic trough receivers - Overheating, thermal cycling, bellow fatigue and antifreflex-coating abrasion

Kurzfassung

This paper describes accelerated aging tests on parabolic trough receivers. Overheating of parabolic trough receivers about 80-100 K over the nominal operating temperature is applied for accelerated aging of the absorber coating. A lifetime prediction based on the Arrhenius parameters requires extensive testing; A reduced test with heating receivers to 478 °C for 1000 hours is applied on receivers for oil fluid in order to compare heat loss and optical efficiency before and after such accelerated aging. In a further test set, such receivers are thermally cycled between 200 °C and 478 °C for 100 times. A bellow fatigue test has been developed for testing of the bellows stability for the compression and expansion. Receivers are subjected to 20,000 cycles and rested for a 24 hour waiting period. The receiver heat loss during the bellow fatigue test shall not increase more than 30 %. Durability of the antireflex coating on the glass is tested with the Taber linear abrasor using the CS-10F rubber (¾”) and MIL 12397 Eraser (¼”). Both abrasive materials proved to be suited to obtain reproducible results, although the discussion is still ongoing on which material should be used. The larger diameter of the CS-10F rubber offers the advantage that transmittance measurement with the Lambda 950/1050 spectrophotometer can be performed without the necessity for multiple abrading stripes.