A hardy, high-yield solar distiller of brackish water

• Published in: Desalination Vol. 67; pp. 43 - 52
• Main Authors: Ouahes, R., Ouahes, C., Le Goff, P., Le Goff, J.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.1987
• ISSN: 0011-9164; 1873-4464
• DOI: 10.1016/0011-9164(87)90230-X

The aim of our research work has been to devise a solar distiller for arid zones, that should be very simple, hardy, easy to maintain and repair by every village artisan with limited technical means, the unit being however of a yield much higher than that of present units. In its single-stage version, which is the simplest one, the apparatus is composed of a 2 to 4 cm thick parallelepipedic cell, inclined on the horizontal plane, so as to be directed perpendicular to the sun rays. Brackish water to be distilled streams slowly within a thin fabric (absorbent gauze) sticking to the “ceiling” of the cell by capillarity, therefore on the back face of the wall heated by the sun rays. The steam that escapes from it, condenses on the cold wall situated on the opposite. Whence the name DIFICAP given to the system, for DI stiller with a FI lm in CAP illary motion. In its three-stage version, the DIFICAP is composed of three identical eveporation/condensation cells, in thermal series. The heat dissipated by the condensation of steam on the front face of a metal plane, is used on the back face of the plane for the evaporation of an equivalent quantity of water. Sun energy is thus used three times in succession. The difference in temperature between plates in each cell is 5 to 10°C. The apparatus produces 15 liters of distilled water, per m 2 and per day, under the same sunshine conditions, that give rise to a production of 2.5 to 3 litres/m 2 day in a conventional distiller, that is the “Single Basin Solar Still”. Its average production capacity is therefore 4 to 7 times that of the conventional distiller. Two identical three-stage DIFICAP have been constructed and are now in operation, one in real conditions in a village near TOUGGOURT (Algerian Sahara), the other under artificial insolation in our laboratory in Nancy (France). In this latter case, experimentation and mathematical modeling have given us better knowledge of the heat and mass transfer by free convection between opposite planes in each cell. As a consequence we have been able to optimize the geometrical shape, the dimensions and the operating conditions of the apparatus.