Experimental Investigation of the Performance of Evacuated-Tube Solar Collectors under Eastern Mediterranean Climatic Conditions

Experimental investigation of the overall performance of solar collectors under local weather conditions as encountered along the eastern coast of the Mediterranean Sea is carried out for two kinds of evacuatedtube solar collectors, namely, the water-in-glass tubes and the heat-pipe designs. An experimental set-up, involving full scale collectors made of a row of 20 evacuated tubes and their tank, and a circulation system with measurement tools, was constructed and used. The experiments were carried out during the period of November to January, i.e. under winter-like conditions, at days where the sky was almost clear with some clouds scattered here and there. The results show that the heat-pipe-based collectors are better than the water-in-glass designs and their efficiency is almost 15 to 20% higher. Their payback periods are however, much higher owing to their larger initial cost in the local market.