Indoor thermal loss test on small-size solar receiver (UF-RT01) for process heat application

The parabolic trough collector is one of the most promising technologies for medium temperature application. The energy of solar radiation is directed by parabolic mirrors into cylindrical receivers and transmitted to a heat transfer fluid. Thus, the characteristics of absorber tubes have a direct influence on overall thermal efficiency of the system. A novel receiver (UF-RT01) for small-size parabolic trough collectors is tested using two coaxial tubes made from stainless-steel with a selective coating, inserted in a glass envelope. In this layout, the fluid inlet and outlet are at the same side. The paper describes the realization of a laboratory test stand for thermal loss measurement of small-size receivers in steady-state condition, based on Joule effect heating supplied by multiple electric resistances. A prototype tube is analyzed experimentally and performances are evaluated as a function of different operating temperatures, reaching up to 180°C. A maximum value for thermal loss amounts at about 24 W when the receiver average temperature is 180°C.