Aspects of hydrogen accumulation in molten salt parabolic trough systems

Abstract

Hydrogen is a severe issue for heat collecting elements of solar thermal parabolic trough power plants. Due to the high operating temperatures of molten salt systems about 30 times lower hydrogen limits may be required if permeation coefficients of standard receivers can be assumed. Hydrogen sources in molten salt systems are hydrogen pick-up of steels and reaction of water with steel surfaces. In this study, it could be should that even with humid solar salt hydrogen emission from steel is quickly degraded by reaction with nitrate. Accordingly, hydrogen formation with steel surfaces and water is considerably slower than hydrogen conversion by nitrate. Hence, maintaining hydrogen concentrations in the low µbar range should be achieved if no unfavorable operating conditions were applied that allowed for enhanced formation.