Qualification test procedure for solar absorber surface durability

A general test procedure for the qualification of solar absorber surface durability has been developed based on the results of a comprehensive case study performed within the framework of the IEA Solar Heating and Cooling Programme Task X. It was assumed, in the development of the qualification procedure, that the intended use of the absorber surface to be qualified, was in single-glazed flat plate solar collectors for domestic hot water production. The absorber surface should be considered qualified if it met the requirement of a design service life of 25 years with maximum loss in the optical performance of the absorber surface corresponding to a 5% relative reduction in the performance of a solar domestic hot water system. The testing procedure, consisting of three kinds of constant load-accelerated life-time tests, was limited to simulation of the following three kinds of absorber surface degradation processes: (a) high-temperature degradation, e.g. oxidation, (b) degradation by the action of moisture or condensed water on the absorber surface, e.g. hydration or hydrolysis, and (c) degradation caused by high humidity air containing a small concentration of sulphur dioxide as an airborne pollutant, e.g. atmospheric corrosion. To quantify expected environmental stress on the absorber surface related to the environmental factors of interest, microclimate data, representing typical service conditions for absorbers in single-glazed flat plate collectors for domestic hot water production were used. (C) 2000 Elsevier Science B.V. All rights reserved.