Efficient direction-independent fog harvesting using a corona discharge device with a multi-electrode structure

Efficient collection of water from fog can effectively alleviate the problem of water shortages in foggy but water-scarce areas, such as deserts, islands and so on. Unlike inefficient fog meshes, corona discharge can charge water droplets and further enhance the water-collecting effect. This study proposes a novel multi-electrode collecting structure that can achieve efficient and direction-independent water collection from fog. The multi-electrode structure consists of three parts: a charging electrode, an intercepting electrode and a ground electrode. Four types of water-collecting structures are compared experimentally, and the collection rates from a traditional fog mesh, a wire-mesh electrode with fog coming from a high-voltage electrode, a wire-mesh electrode with fog coming from a ground electrode and a multi-electrode structure are 2–3 g h^-1, 100–120 g h^-1, 60–80 g h^-1 and 200–220 g h^-1, respectively. The collection rate of the multi-electrode structure is 100‒150 times that of a traditional fog mesh and 2–4 times that of a wire-mesh electrode. These results demonstrate the superiority of the multi-electrode structure in fog collection. In addition, the motion equation of charged droplets in an electric field is also derived, and the optimization strategy of electrode spacing is also discussed. This structure can be applied not only to fog collection, but also to air purification, factory waste gas treatment and other fields.