The effects of design parameters on productivity performance of a solar still for seawater desalination: A review

This paper aims to investigate the different parameters that affect solar still productivity when the solar still productivity is very low compared with other desalination systems, such as other thermal processes or membrane processes. These parameters include environmental, design and operational parameters. The results show that productivity was highly affected by environmental parameters due to the unpredictability of metrological factors. When design and operational parameters were varied, increases in productivity were observed. The results indicated that the solar still was inversely affected by evaporation area, water depth, a minimization in the angle of the solar still cover during summer seasons and maximization during winter seasons. Stepped solar still techniques enhanced the productivity, and the addition of wicks in a stepped solar still was proposed. Insulating the sun tracking system positively affected the productivity because the insulation increased the heating capability and evaporative effects inside the still basin. © 2016 Elsevier B.V. All rights reserved.

Fig. 19. Energy flow in Single basin single slope solar still [95,98]. This study reviews the parameters that influence solar still productivity. The parameters include climatic, operation and design parameters. The productivity of a solar still is directly correlated with the amount of solar radiation, the surrounding temperature, relative humidity, wind speed and the maintenance of the cover. These metrological parameters cannot be controlled. The most essential controllable parameters are design parameters. Based on this detailed review, an optimum design to achieve a superior system performance can be summarized as: follows (a) a condensing cover angle, which is strongly dependent on still location, time of operation, and condensing material. However, it has been generally [14,49,70] suggested that angles of 30° and 45° [20] and smooth and low thermal capacity glass are optimal; (b) a still constructed of copper has a higher thermal conductivity 390 W/mK; (c) a still with a stainless steel frame; (d) a black basin liner; (e) the use of glass wool or sawdust insulation; (f) a recommended basin water depth of 3 cm; and (g) a dynamic water feeding mode. A stepped solar still also results in increased evaporation area and increased productivity. Furthermore, a high productivity rate can be achieved by using a combination of additive materials (e.g., fin and sponge) integrated in a stepped solar still. Internal and external (top and bottom) reflectors can also increase the productivity of stepped solar stills. Insulation materials, such as saw dust can enhance the productivity by preventing thermal heat losses. A spray system can also result in a high productivity rate. The production rate of a solar still is maximized when it is correctly positioned with respect to the direction of solar radiation during operation. The maintenance of a solar still system is highly recommended to ensure high operative efficiencies.