Author(s)

J. Lindblom & B. Nordell

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. Keywords: condensation, irrigation, subsurface, solar driven, desalination, modelling, mass and heat transfer. 1 Introduction The accelerating land degradation and declining agricultural productivity in Africa constitute major problems for its population’s future economic and food security. Predictions indicate that the continent only will be able to feed 40% of its population in another 20 years [1]. Since only 10% of the African land has the potential of rain-fed cultivation, and since water availability often is the most limiting factor for root growth [2], irrigation expansion is of highest importance for Africa’s future development. However, more than 90% of the available freshwater is already used for irrigation in some parts of Africa [3], and groundwater tables in some areas are dropping rapidly due to increasing tube well installations [4].

Keywords

condensation, irrigation, subsurface, solar driven, desalination, modelling, mass and heat transfer.