Screening testing is thereafter conducted with the purpose of qualitatively assessing the importance of the different degradation mechanisms and degradation factors identified in the initial risk analysis of potential life-limiting processes.

When selecting the most suitable test methods for screening testing, it is important to se­lect those with test conditions representing the most critical combination of degradation factors.

Using artificially aged samples from the screening testing, changes in the key functional properties or the selected degradation indicators are analysed with respect to associated material changes. This is made in order to identify the predominant degradation mecha­nisms of the materials in the component. When the predominant degradation mechanisms have been identified also the predominant degradation factors and the critical service con­ditions determining the service life will be known.

Screening testing and analysis of material change associated with deterioration in per­formance during ageing should therefore be performed in parallel. Suitable techniques for analysis of material changes due to ageing may vary considerably.

On the static solar materials of Task 27, a number of accelerated screening have been performed including simulation of possible degradation in performance under the influence of high temperature, high humidity/condensation, UV, and corrosion loads; either single or combined loads; see Table 5.

In Figure 3 the results from a series of screening tests on pure aluminium, used as refer­ence reflector material, are shown as an example of result from the Task 27 study. Degra­dation in optical performance is observed mainly, as expected, in the corrosion tests. In Figure 4 the result from the testing of a number of antireflective glazing materials at 80 °C and 95 %RH is given. The cause of degradation in optical performance is in this case not understood and the degradation therefore needs to further analysed. To identify degrada­tion mechanisms for the tested materials various analytical techniques are presently em­ployed.