The annual results for this system are shown in Table 4. As can be seen the poorer the collector characteristics the poorer the system performance indicated by the useful energy delivered from the solar system (Qu) and consequently more auxiliary is required (Qaux). However the differences between ordinary painted collectors (type C & D, є=0.9) with the corresponding selective coated collectors (type A & B, є=0.1), is about 16% for Nicosia and 20% for Athens.

Typical monthly results for type A collectors for both Nicosia and Athens are shown in Table 5. As can be seen the solar system can satisfy almost all needs during the summer months represented by the small value of Qaux during these months. The column Qins in Table 5 refers to the radiation incident on the collector surface and the Qenv to the heat loses from the storage tank envelope.

Comparative graphs of the monthly useful energy (Qu) and auxiliary energy (Qaux) for the four types of collectors considered are shown in Figs 2 and 3 for Nicosia and Athens respectively. In all cases the performance of the color collectors is somewhat lower than that of the respective black absorber collectors.