Enhancing tubular solar still performance using double effect with direct sunrays concentration

Water scarcity, energy and demographic nature are real challenges facing many countries worldwide. These are maximized in rural communities where using the conventional energy resources for freshwater production may not be available. Thus the present study develops a novel double-effect tubular solar still installed at a focal line of a parabolic concentrator solar tracking system as an efficient solution. The developed device is experimentally examined under the climatic conditions of Ha'il city, Saudi Arabia. The results showed a significant enhancement in the performance of the developed device compared with the conventional single-effect device. The developed device increased the freshwater productivity and efficiency by 31.65% and 26.65%, respectively, with almost no increase in the freshwater production cost. A 5.2 L/m(2)day freshwater productivity was achieved with almost 40.4% daily thermal efficiency. Under the same operating conditions, the developed device presented 13%-50% higher productivity compared with the related published studies. The freshwater yield of the second effect was 25.8% of the total device yield, with a tube surface temperature of 73 degrees C compared with 88.6 degrees C for that of the single-effect device. This lower temperature along with the lower water mass in the second effect led to a significant decrease in the heat loss to the surrounding. It can be said that one square meter of the developed system can produce the essential freshwater needs per day for one person in rural and isolated communities.