Experimental investigation of hydrogen reduction in PTC receivers by back-permeation into HELISOL® XLP silicone based HTF with accompanying venting of the HTF

Abstract

Hydrogen accumulation in Parabolic Trough Collector (PTC) receivers can significantly increase their heat losses and reduce PTC power plant efficiency and revenue. An experimental demonstration of hydrogen reduction in PTC receivers to restore their performance by hydrogen back-permeation into the heat transfer fluid (HTF) is set up at the KONTAS PTC test rig at the Plataforma Solar de Almería (PSA), Spain. Within this thesis KONTAS is adapted for the experiment and an operation and data evaluation strategy is developed. The operation parameters are selected to simulate conditions of a PTC power plant changing its HTF from the state-of-the-art DPO/BP to the silicone based HTF HELISOL® XLP. An expansion vessel venting procedure is developed to reduce the hydrogen concentration in the HTF, which is required to enable hydrogen back-permeation from the receivers to the HTF. It is observed that the amount of condensate formed during venting significantly increases with higher venting temperatures. To balance expansion vessel cooldown time and condensate formation, the venting temperature is set at 150 °C. Analysis of HTF samples show that a 40 % reduction of hydrogen concentration in the HTF is achieved through the developed venting procedure. During operation the HCEs glass envelope temperatures are measured and graphically visualized so potential long termchanges of HCE heat losses can be detected. At the submission time of this thesis, the experiment just started and KONTAS had been in operation for 175 hours of the expected 3000 hours. So far, no HCE temperature reduction has been observed.