Combined Measurement of Thermal and Optical Properties of Receivers for Parabolic Trough Collectors

Kurzfassung

Two new test benches have been developed for the combined measurement of the thermal properties and overall optical efficiencies of receivers for the use in parabolic trough collectors. In the first test bench two receivers are simultaneously irradiated by natural sunlight via parabolic troughs that are mounted on a two axis tracking stage. Shutters enable the variation of the aperture for quasi constant solar input power over the test period. The second, the solar simulator test bench consists of an elliptical cylinder with flat end reflectors. Metal halide lamps (HMI) and the receiver are positioned in the two respective focal lines. The test benches are operated in two modes: Cold performance tests with water flow through the receiver at near ambient temperature in order to measure the optical efficiency in the stationary enthalpy increase, secondly hot testing with the empty receiver at typical operating temperature in order to compare irradiant power and steady state thermal loss power and calculate the efficiency. The test benches are operated in combination with classic heat loss measurement, together the three test benches form a complementary set. First comparative measurements with cold testing on the solar simulator test bench show high reproducibility and a measurement precision relevant for qualification and comparison of different receiver types at industrial and research level.