Subsurface irrigation by condensation of humid air

Abstract

Condensation Irrigation (CI) is a combined system for solar desalination and irrigation. Solar stills are used to humidify ambient air flowing over the saline water surface in the stills. This warm, humid air is then led into an underground system of drainage pipes where it is cooled and vapour precipitates as freshwater. The condensed water and some humid air percolate through the pipe perforations and irrigate and aerate the ground. Mass and heat transfer in the soil-pipe system has been modelled to evaluate the theoretical productivity for these types of systems. For a presumed pipe configuration and climate, 3.1 kg water per pipe-meter and day was condensed inside the buried pipe, yielding 2.3 mm/d irrigation water. Pilot plants on the CI system and are now in operation in Tunisia and Algeria. Another CI plant is planned in Libya.