Effects of solar geometry and operation period on stability of solar desalination systems: a review

The sun is the primary source of life on the earth. The heating effect of the sun provides a more fruitful environment for mankind. In addition, solar energy in the form of thermal radiation has been utilized for solar thermal applications and space heating. With abundant solar radiation, the emergence of the solar desalination has been emerged as a viable solution for water purification by utilizing solar stills. However, solar-powered distillation is relatively a slow process due to the requirement of bulk heating. To suppress thermal conduction to bulk water, various photothermal materials were employed. However, there are many governing parameters which influence the productivity, including solar intensity, cloud, wind, ambient air temperature, humidity, solar absorption of blackened surface, depth of bulk water, feed water type, angle of condensation surface, water film thickness, underneath the condensing surface, and experiment period. Further, systematic and continuous experiments for extended periods are essential for determining the stability and durability of a solar desalination system. The main objective of this article is to review all the experimental studies conducted for two months at minimum up to 1-year duration. In addition, all the SDSs handled in this study further were examined by solar geometrical factors, including day length (DL) and position of the sun or zenith angle (θ_z). As a result, the sunshine hours, day length, and the solar zenith angle play an important role in the water evaporation rate. Lower solar zenith angle and longer day length (more sunshine hours) are desirable for higher water productivity.