Abstract

Fog is an important water resource especially in arid and semi-arid zones. The usual method to collect fog water is placing a rectangular mesh perpendicular to the wind which traps fog droplets. A fraction of the water droplets contained in fog are caught by the collector, where they can grow by coalescence until they are large enough to fall by gravity, where they can be collected. Fog events can last from minutes to hours, or even more. The goal of this paper was to evaluate the efficiency (η) of a standard fog collector (SFC) to collect fog water. It is defined as the ratio between the water which reach the collector’s gutter (CW) and the liquid water flux (LWF) normal to the collector’s mesh, integrated in a period of time. Because after the starting of a fog event, mesh collectors requires some time to reach saturation and begin dripping and the system does not achieve stationary state at field conditions, in the evaluation of the efficiency entire fog events were considered. The CW was measured by a rain gauge and the LWF was calculated from liquid water content (LWC) obtained through a fog droplet spectrometer, and data of wind velocity registered by a meteorological station. The duration of the analyzed events ranged between 20 min and 11 h 40 min. A lag between the arrival of fog and the beginning of the measured water output of up to one hour was found. Both processes started simultaneously when preceded by another fog event.