Exergy and energy analysis of a novel solar powered fog desalination system

A novel system that applied fogging as a desalination technique was recently published, which could be considered a further development of the humidification-dehumidification desalination system (HDH), that provides an advantage through its ability to desalinate high salinity levels. This involves spraying hot saline water at high pressure vertically upwards, creating a mist instead of large water droplets. This increases productivity since the fine mist facilitates evaporation and the low-saline mist can go upwards more than the large high-salinity droplets. However, experiments showed that this methodology, in terms of productivity, performance and cost, was between other technologies. It was noted that the performance of this system peaked at -39 %. Therefore, in this paper, an exergy analysis of the system is presented to determine the location of the highest exergy destruction and also highlight its comparative feasibility. The results indicated that the exergetic efficiency of the system reached 17.3 % while the main source of irreversibility is the fogging process itself (-75 %). Additionally, increasing the water temperature from 33 to 76 degrees C increased the exergetic efficiency of the fogger from 4 % to 20 %. Therefore, the authors recommend using a combination of humidification and atomization via nozzles of larger orifices with different spraying angles.