Abstract
Dew water is water vapour that passively condenses from air. Once properly collected, it can provide a useful supplementary water resource for plants and humans. Its production can be significantly improved by using specific materials and particular geometry. In this context, new shapes for dew collectors arepresented and their water yields are compared with those of a 1 m2, 30°, inclined planar condenser usedas a standard. The experiments were carried out in Pessac (SW France), situated about 45 km from the Atlantic Ocean, during summer and fall 2009. In addition to conical shapes, which have 30 % larger yields than the planar reference condenser and whose functioning was simulated numerically, two new families of forms are considered: egg-box and origami types. The egg-box shape yields 9 % more water as compared to the reference planar condenser, a result nearly independent of the dew yield. In contrast, the origami shape gives yields 150 % larger than the reference planar condenser for events with high dew volumes and can show 400 % greater yields for low dew volumes. These results are analysed and discussed in terms of (i) radiative effects correlated with the angular variation of sky emissivity, (ii) heat losses by free and forced (wind) air convection and (iii) gravity water flow. General rules to increase dew collection are outlined.
