Solar simulator based on induction heating to characterize experimentally tubular solar central receivers

Abstract

Solar receiver tubes in solar power tower plants are subjected to non-homogeneous heat flux and temperature that produce early failure derived from the thermal stress. To reduce these problems, the thermomechanical characterization of the receiver is required. However, there are limitations in the data acquisition during operation due to the extreme working conditions, the different scale lengths, and the disturbance of the normal operation, being not possible to determine experimentally the thermomechanical behaviour of this device or to validate specific models developed.In this work an experimental facility able to reproduce the operation conditions of solar receivers has been designed and tested. To obtain the non-homogenous heat flux an induction heating system has been used. The facility has also been equipping of sensors and cameras that allow to measure the temperature distribution, the displacement and the strain field in a tube stretch. It is obtained a circumferential variation of the temperature of 160 °C, and a tube displacement due to the bending produced by the temperature gradient in combination to the mechanical boundary conditions of 2.251 mm. The data obtained with the cameras have been checked with the displacement and temperature sensors, obtaining maximum differences of 3 %, it means 5 °C and 0.05 mm. Thus, it is possible to derivate the tube displacement to obtain the hoop and axial strain field. These results are the first step for the thermomechanical characterization of tubes with non-homogeneous temperature profiles in the three directions. The proposed solar simulator will allow the validation and development of thermomechanical models able to reproduce the operation conditions of the receiver with the final goal of improving the receiver design and operation.