A New Transient Thermography Method For Parabolic Trough Receiver Heat Loss Measurement

This paper describes a new transient method to measure the heat loss of parabolic trough receiver tubes using transient thermography. The method complements already existing stationary measurement methods which use energy balances or the observed glass enve-lope temperature to deduce thermal losses. It is shown that by a thermal excitation of the absorber tube and by both measuring the absorber tube and the glass envelope temperature responses, the receiver heat loss can be calculated. Additionally, the emissivity of the se-lective coating and the quality of the annulus vacuum can be derived. The advantages, challenges and limits of the new method are presented and compared to the established sta-tionary methods. Simulation results and first measurements which validate the simulations and findings are described. An uncertainty analysis shows that used in the solar field, this method reduces the measurement uncertainty from about 15 to 20% (conventional station-ary field measurement technique) to about 6% (new transient method)