Underground condensation of humid air: a solar driven system
for irrigation and drinking-water production

Abstract: The objective was to investigate the feasibility of using warm, humid air
for subsurface irrigation and drinking water production. By letting air flow
over the water surface in a solar still with saline or polluted water,
vapour mixed with the air and saturated it. The vapour-saturated airflow was
conducted down into buried pipes, where the air gradually cooled and the
water precipitated along the pipe surface. For the irrigation system,
drainage pipes were used, in which the condensed water penetrated the slits
out to the soil. Replacing the drainage pipes with common PVC-pipes resulted
in a system for drinking-water production, where the condensed water could
be collected at the end of the pipes. In order to drive the air through the
pipes, a fan was used in the irrigation system and a solar chimney in the
drinking-water system. To visualise the cooling process in a buried pipe and
the temperature distribution in the soil, a small-scale field test was
conducted at the Çukurova University in Adana, Turkey. A secondary purpose
was to get a feeling for the planning and execution process of a field
experiment. The designed irrigation system was found to be more water-
efficient, involve less transportation and be a sustainable solution. In
addition, the economic estimations showed that condensation irrigation
system has the potential of being competitive with traditional irrigation
methods.