Numerical simulation of the enhancing effect of micro–nano protrusions on electrostatic fog harvesting

Abstract

Fog harvesting is one potential approach to provide supplementary water resources in arid areas. Considerable research has been devoted to electrostatic fog harvesting technology, but there are still some problems, such as high voltage, complex structures and expensive cost. Decorating micro–nano protrusions on the electrode is an effective method to lower the operating voltage and improve fog harvesting efficiency, and the enhancement effect of protrusions has already been experimentally demonstrated. However, the enhancement mechanism at the microscopic level is less reported. This manuscript tries to explain why micro–nano protrusions can enhance the discharge and electrostatic fog harvesting, via numerical simulation. Three key processes of corona discharge, fog droplet migration and fog harvesting efficiency are discussed in detail, especially the influence of droplet size, the tip radius of the protrusion, the protrusion–protrusion angle and so on. The numerical simulation results show that the inception voltage of the barbed electrode decreases from 7 kV to 3 kV (a decrease of 57%), and the current increases significantly (e.g. by 68% at 15 kV). At 15 kV, the fog harvesting efficiency of the barbed electrode is higher (29.8%) than that of the smooth wire (25.7%), even with a less-effective collection area. The collection efficiency increases with the droplet size, and there is an optimized ratio (∼1‰) of the protrusion tip radius and wire radius to gain high collection efficiency. These research results are beneficial for understanding the microscopic mechanism of protrusions that enhance electrostatic fog harvesting, and provide guidance for further fog harvesting equipment improvement.