Collecting fog with vertical fibres: Combined laboratory and in-situ study

•The efficiency of fog collection with fibrous nets depends on the net geometry.•A change of structure, using co-fibres pairs, improves the collection efficiency.•There is an optimal solidity at which collection is maximal.•A co-fibre collector gives an accurate and robust description of all fog events. Fog harvesting is an application of aerosol filtration to capture water droplets from fog by using nets, called fog collectors. It is a promising technique for freshwater supply in arid and semi-arid regions. In this study, we investigate the collection efficiency of harp-like fog collectors consisting of vertical fibres. We conduct well-controlled laboratory scale experiments on model fog collectors and develop a predictive theoretical model accounting for the liquid distribution on the fibres and for aerodynamic effects. Without using any adjustable parameter, we obtain a good agreement between our theoretical model and laboratory scale experimental results. Furthermore, we perform collection efficiency measurements on an in-situ pilot scale fog collector, accompanied by a description of the fog's microphysical properties. Comparing the results of our pilot scale and laboratory scale experiments and the theoretical model developed, we propose a method to accurately evaluate the efficiency of our collector, with simultaneous measurements of collected water volume and fog characteristics.