Effects of mist spray cooling on freshwater production and thermal efficiency of stepped solar desalination system

This research discusses the experimental investigation of utilizing fans on a stepped solar still (SSS) to increase the condensation rate and improve efficiency. A stepped solar still has 12 galvanized steps, with a total evaporation area of 0.275 square meters tested under the weather conditions of Semnan City, located in Semnan province, Iran, at a latitude of 35°. The test was carried out using two fans with saline water spray capability, and it was examined in three modes: without fans, with fans, and using fans and spray. Four different inlet flow rates were considered over 12 days of testing. The parameters examined in this test included ambient temperature, glass cover temperature, inlet saline water temperature, outlet brine temperature, the amount of freshwater produced, wind speed, humidity, and solar intensity. The desired data were recorded and analyzed every day for 9 h, from 9 am to 5 pm, and the device’s efficiency was investigated. According to the findings, the best performance in terms of daily water production was achieved with the fan and spray mode at a flow rate of 90 mL min⁻¹, which resulted in 1.41 L of fresh water per day. The device demonstrated its highest daily efficiency of 49.4% when using the fans and spray at 30 mL min⁻¹. Moreover, the highest exergy efficiency of 77.4% was obtained with the fans and spray at 30 mL min⁻¹. The modified stepped solar still boosts annual productivity by 24.44% at the expense of a 58.41% increase in CPL, presenting economic challenges needing further research.