Optimum collection geometries for copper tube - copper sheet flat plate collectors

Normally the flat plate collector of solar energy for heating liquids features a series of tubes fastened at intervals to a copper collection plate of uniform thickness. Copper can be used in a more cost effective way if the collection plate is not of uniform thickness, but of tapered cross-section between the tubes. A number of different cross-sections were investigated in a study described in this paper, including 'ideal' profiles which are unlikely to be practical, as well as compromise profiles likely to be feasible. It was found that tapered profile material can cost somewhere between 28% and 36% more per unit weight than flat (constant thickness) sheet, and still be equally cost effective as flat sheet.