A bioinspired ladder-like harp Fog Water Collector. I. Model design, simulations and laboratory testing

A bioinspired three-dimensional fog collector composed of harp-like filament strips arranged in a ladder shape is proposed as an alternative structurally stable devise for fog water harvesting. The 3D-printed models were tested inside an instrumented wind tunnel. The length, diameter, geometry, surficial microtexture of the filaments, solidity, inclination, number of rows, and curvature of the model's strips were optimized through a series of experiments with artificial fog. The optimum filaments were 5-cm-long smooth conical cylinders (0.6° conicity), with a diameter of 1.5 mm at the circular base, ending on an acute pointing tip. A 60° inclination of the filament screen improved 1.5-fold the fog water collection yield with respect to that obtained using the screen positioned vertically. In addition, although the collection yield increased with the screen curvature (either concave or convex), this improvement was compensated if corrected by the number of filaments, i.e., equal projected shading. Fog water yield was 1.5-times higher as the number of overlapping impacting screens increased from 1 up to 4. However, not much improvement was achieved beyond the third layer, such that the fog water collection leveled off up to a plateau after this. A sequence of screens comprising smooth conical slender filaments with an intermediate shading coefficient (SC ≈ 35 %; 2.7 mm center-to-center spacing) and distributed in partly overlapping parallel rows was found to render maximal water yield with an efficiency of 10–20 % (at wind velocities between 2 and 6 m s⁻¹).