The solar humidification–dehumidification method (HDH) is a thermal water desalination method. It is based on evaporation of sea water or brackish water and subsequent condensation of the generated humid air, mostly at ambient pressure. This process mimics the natural water cycle, but over a much shorter time frame.
The simplest configuration is implemented in the solar still, evaporating the sea water inside a glass covered box and condensing the water vapor on the lower side of the glass cover. More sophisticated designs separate the solar heat gain section from the evaporation-condensation chamber. An optimized design comprises separated evaporation and condensation sections. A significant part of the heat consumed for evaporation can be regained during condensation. An example for such an optimized thermal desalination cycle is the multiple-effect humidification (MEH) method of desalination.
Solar humidification takes place in every greenhouse. Water evaporates from the surfaces of soil, water and plants because of thermal input. In this way the humidification process is naturally integrated within the architecture of the greenhouse. Several companies like Seawater greenhouse utilize this inherent feature of a greenhouse in order to conduct desalination inside the atmosphere of the facility. The integrated biotectural system, or IBTS Greenhouse mimics the natural process of cloud formation respectively desalination exactly.
There are successful small-scale agricultural experimentation done in arid regions such as Israel, West Africa, and Peru. The major difficulty lies in effectively concentrating the energy of sun on a small area to speed up evaporation.
- Encyclopedia of Desalination and Water Resources
- The MEH-Method (in German with English abstract): Solar Desalination using the MEH method, Diss. Technical University of Munich
- Desalination Systems using the MEH-Process
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