T-TraCS – an Automated Method to Measure Soiling Losses at Parabolic Trough Receiver Tubes

Soiling of the envelope tubes of parabolic trough collectors can significantly reduce their transmittance and hence the overall collector efficiency. There are only a few methods to quantify soiling losses at absorber tubes of parabolic trough collectors. The existing methods are either laboratory based and cannot be applied automatically or they are personnel intense because they can only be used manually inside of operational solar fields. In this work we present a novel device called T-TraCS capable of automatically measuring the transmission of a sample glass during outdoor exposure with the current solar spectrum and imitating the movement of operational parabolic trough collectors. It can be used in resource assessment campaigns in order to better estimate future soiling losses at the tube level or it can be set up inside a solar field in order to measure the tube soiling losses in real time for CSP plant operation. Scattering simulations are presented that correct the measurement raw values of the T-TraCS and a spectrophotometer for their differences to the optics of a receiver tube. The validation with these final measurements shows good agreement with the reference spectrophotometer with a R2 of 0.996. The T-TraCS is therefore capable of automatically determining the soiling induced transmission losses with high accuracy.