The Effect of Construction Material on the Desalination Plant Using Solar Mirrors

The objective of this study is to determine the best material for building the direct Solar desalination plant using concentrated mirrors. The study was applied on three pilot plants that were erected in the experimental laboratory site area of faculty of engineering, Ain Shams University, Cairo, Egypt. This study was made in four months covered spring and summer seasons which simulated the best climatic period to help in obtaining the best performance of the pilot plants. The three applied materials were steel, glass & acrylic. The applied raw water were prepared in the lab using sodium chloride and distilled water. Each pilot occupies 2m2 and consisted from three serial channels on three levels inside the trapezoidal shape room with flat bottom and inclined roof. The system used three mirrors of galvanic steel to concentrate sun rays on saline water channels for the all sunshine period. The system used a very small pump with flow rate 40 l/h to ensure enough retention time in the pilot to heat water and evaporate it. The measurements for water temperature, TDS, pH, and flow rates of inlet and outlet were made. Also air temperature & humidity ratio out and inside each pilot were measured. The sunshine period had been taken during all days of the study period. The results of fresh water were varied from 8 l/h to 18 l/h with acrylic plant and 8 to 20 l/h with glass plant and with steel it achieved variation between 15 – 30 l/h which were good in quality and quantity of produced fresh water with minimum cost. The study show that the recovery ratio was (10%-45%) with acrylic plant and (20%-50%) with glass plant and from (37% - 75%) with steel plant which is a good ratio for all solar desalination plants compared with other systems of desalination. The produced TDS from all plants in the fresh water was between 20 -60 ppm that may need some salt additives to meet the range of WHO recommendation No. 7. The retention time inside all units was almost the same to ensure the comparison validity. The steel plant achieved the higher productivity with also the lower in construction cost but it need also the higher running cost before the need of repainting every year