Using radiative cooling to condense atmospheric vapor: a study to improve water yield

An inexpensive radiative condenser for collecting atmospheric vapor (dew) was tested in Grenoble (France). The surface temperature measurements are correlated with meteorological data (wind velocity, air temperature) and compared to the corresponding surface temperature of a horizontal Polymethylmethacrylate (Plexiglas) reference plate located nearby. The condenser surface is a rectangular foil (1 X 0.3 m(2)) made of TiO2 and BaSO4 microspheres embedded in polyethylene. The foil has an angle theta with respect to horizontal. The under-side of the device, thermally isolated, faces the direction of the dominant nocturnal wind. Both a 2D numerical simulation of the air circulation around the foil and experimental measurements shows that the angle theta = 30degrees is a good compromise between weak wind influence, large light-emission solid angle and easy drop collection. The study was conducted from November 25, 1999 to January 23, 2001. In comparison to the reference plate, it is found that water yield can be increased by up to 20% and water collection greatly facilitated. (C) 2003 Elsevier Science B.V. All rights reserved.