Durability Testing of Solar Receiver Coatings: Experimental Results for T91 and VM12 Substrates

Abstract

In Central Receiver Systems, the receiver coating absorbs the concentrated sunlight from the heliostat field and needs to withstand high thermal stresses in harsh desert climates. Coating degradation is associated to high repair and down-time costs and therefore several research activities have been conducted in the past years to increase the Service lifetime of receiver coatings. This paper presents the durability test results of six novel receiver coatings developed for operation temperatures of 600°C. The coatings were deposited on ferritic-martensitic steel coupons made of T91 and VM12-SHC. The testing program involved a sequential accelerated aging test: on-sun testing with an average flux Level of 300 kW/m² was combined with isothermal furnace testing and humidity testing at low temperature to mimic condensation on the receiver during night-time. In addition, climate chamber tests have been carried out. This paper summarizes test results and identifies the most promising coating developments.