Elke Streicher

Impact of Ageing on Thermal Efficiency of Solar Thermal Collectors

Today it is common practice to calculate the performance of solar thermal systems or solar collectors based on the results of a thermal performance test carried out with a new solar collector. However, for an integral assessment of solar thermal collectors and systems, it is necessary to consider the change of performance with time due to degradation effects. Degradation effects like a reduced transmittance due to deposits on the transparent collector cover or a reduction in the absorption coefficient of the absorber due to high temperature oxidation mechanisms may result in decreased collector efficiency. Up to now it is not possible to take these degradation effects into account, systematically.