Of all types of solar collector, the flat-plate collector (FPC) has the lowest performance, but is the most widely used because of its low cost and easy maintenance. To effectively collect solar light in the conventional FPCs, metal tubes with a high thermal conductivity are installed under an absorption plate. However, in this study, in order to take advantage of the sunlight absorption capacity of coloured water flowing through a tube, a transparent tube was installed on the absorbing plate. The resulting new FPC suggested in this study is a direct absorption solar collector (DASC). To investigate its performance as a function of the colours of the working fluid, four colours of water were supplied to the FPC: transparent (pure water), red, violet and black. From the experimental results, the new FPC suggested in this study was found to have about 5% higher performance than those of the conventional types of FPC, which means that the new concept of FPC can profitably replace the conventional FPCs.
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