Enhanced dew harvest with porous wind covers

Abstract

Dew harvest with radiative cooling condenser can be a simple and portable solution to extract water from the atmosphere, but its water yield is limited. Implementing wind cover is one of the simplest ways to improve cooling power by reducing convection. However, wind covers usually block water transport and cannot be applied to radiative condensers for dew harvesting. Herein, porous wind covers, including polyethylene (PE) nets and porous PE films, have been adopted, and their effect on radiative condensers has been investigated. These wind covers have good atmospheric window transmittance and convection reduction effect. The two-day radiative cooling experiment has proven that sufficient sub-ambient cooling can be achieved using our radiative cooling film. Afterward, a two-month nocturnal condensation experiment was conducted. Condensers covered with high porosity PE nets on average yield more water than the condenser without cover, with a maximum improvement of 19.5% using a PE net with ∼86% porosity. In particular, at low humidity condition, the average water yield for the condenser without cover is only 1.4 g/m 2 /night. In comparison, the value increases to 23.7 g/m 2 /night and 13.6 g/m 2 /night for condensers covered with a PE net (∼64% porosity) and a porous film (∼4% porosity), respectively. The improvement in water yield indicates that porous wind cover is a simple and essential tool for radiative condensers to provide more water in regions with dry and windy climates. Further analysis has revealed that experimental observations arise from the trade-off between convection suppression and water transportation of the porous wind covers. • Wind cover is a simple tool for radiative condensers to potentially improve water yield. • A maximum water yield increase of 19.5% occurs for condensers in Shanghai with high-porosity cover. • At low water yield, condensers with wind cover can increase the water production by up to 10 times.