Greenhouse dehumidification by a desiccant absorption system

Conventional control of high humidity in the greenhouse involves ventilation with simultaneous heating, this method increases the greenhouse heating costs.
An alternative method of reducing air humidity is the absorption/adsorption of moisture by a solid or a liquid hygroscopic material.
Hygroscopics are materials that have a high coherence for water vapour.
Research on the application of hygroscopic greenhouse dehumidification is minimal.
The aim of the present study was the design, construction and experimental testing of a dehumidification system using a hygroscopic material, CaCl₂ solution, for greenhouse dehumidification.
For this purpose a dehumidification system was designed, constructed and tested in a greenhouse.
CaCl₂ aqueous solution was used as desiccant.
The desiccant solution flowed over a porous Celdek structured pad and greenhouse air was forced to pass through the pad by a fan whose speed could be varied and adjusted.
The system was tested in a cucumber growing greenhouse and operated when the relative humidity (RH) exceeded 80%. The results show that greenhouse air temperature, specific humidity, greenhouse air flow rate through the system and desiccant concentration have an important influence on the moisture removal rate by the system.
The water vapour removal capacity of the tested hydroscopic absorption system at greenhouse temperature of 15°C and RH 80% was found to be 1155 g h^‑1 (or 4812 g h^‑1 m^‑2 of cross pad surface). Greenhouse dehumidification by the tested system significantly reduced the relative humidity of greenhouse air and leaf temperature was always higher than dew-point of greenhouse air.

I International Symposium on Protected Cultivation, Nettings and Screens for Mild Climates

I. Lycoskoufis, G. Mavrogianopoulos

evapotranspiration, condensation, relative humidity, hydroscopic material, CaCl₂

https://doi.org/10.17660/ActaHortic.2025.1437.17