Qualification test procedure for solar absorber surface durability

A general test procedure for the qualification of solar absorber surface du rability has been developed based on the results of a comprehensive case st udy performed within the framework of the IEA Solar Heating and Cooling Pro gramme Task X. It was assumed, in the development of the qualification proc edure, that the intended use of the absorber surface to be qualified, was i n single-glazed flat plate solar collectors for domestic hot water producti on. The absorber surface should be considered qualified if it met the requi rement of a design service life of 25 years with maximum loss in the optica l performance of the absorber surface corresponding to a 5% relative reduct ion in the performance of a solar domestic hot water system. The testing pr ocedure, consisting of three kinds of constant load-accelerated life-time t ests, was limited to simulation of the following three kinds of absorber su rface degradation processes: (a) high-temperature degradation, e.g. oxidati on, (b) degradation by the action of moisture or condensed water on the abs orber 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 envir onmental stress on the absorber surface related to the environmental factor s of interest, microclimate data, representing typical service conditions f or absorbers in single-glazed flat plate collectors for domestic hot water production were used. (C) 2000 Elsevier Science B.V. All rights reserved.