Estimation of dew yield from radiative condensers by means of an energy balance model

SummaryThis paper presents an energy balance modelling approach to predict the nightly water yield and the surface temperature (Tf) of two passive radiative dew condensers (RDCs) tilted 30° from horizontal. One was fitted with a white hydrophilic polyethylene foil recommended for dew harvest and the other with a black polyethylene foil widely used in horticulture. The model was validated in south-eastern Spain by comparing the simulation outputs with field measurements of Tf and dew yield. The results indicate that the model is robust and accurate in reproducing the behaviour of the two RDCs, especially in what refers to Tf, whose estimates were very close to the observations. The results were somewhat less precise for dew yield, with a larger scatter around the 1:1 relationship. A sensitivity analysis showed that the simulated dew yield was highly sensitive to changes in relative humidity and downward longwave radiation. The proposed approach provides a useful tool to water managers for quantifying the amount of dew that could be harvested as a valuable water resource in arid, semiarid and water stressed regions.

► Surface temperature and dew yield of RDCs are estimated from the energy balance.
► Surface emissivity and emitted radiance are two key parameters when modelling dew.
► The applied filter was an appropriate strategy for a good performance of the model.
► Dew yield is very sensitivity to the meteorological input variables/parameters.
► Our energy balance model explained about 70% of the total variance of dew.