Original Authors: Karim Awad, Mohamed Awad, Ahmed Kandel
Introduction:
As fresh water sources dwindle, innovative methods are needed to meet the rising demand for clean water. One such method is extracting water from atmospheric air using solar energy and condensation techniques. This study explores the efficiency of a double slope condensation surface system, which utilizes solar energy as the primary heat source and Calcium Chloride (CaCl₂) as a desiccant to capture and condense water from atmospheric air.
Key Findings:
The system involves two key parts: an absorber bed, where Calcium Chloride absorbs moisture from the air at night, and a transparent condensation surface in the form of a prism. The collected water condenses on the sloping surface during the day, driven by solar energy. Experimental results revealed several important findings:
The maximum water yield recorded was 735 grams per square meter per day under a cumulative solar radiation of 7806 W·hr/m²/day on August 19th, 2015.
The absorber surface temperature increased significantly during the day due to solar radiation, promoting the evaporation of the absorbed moisture and subsequent condensation on the cooler surface.
Experimental Setup:
The apparatus was designed with a triangular prism-shaped condensation surface covering a Calcium Chloride bed. The system was exposed to the atmosphere at night to allow for moisture absorption, and then covered during the day for the evaporation-condensation cycle. The apparatus was tested outdoors, and key parameters such as solar radiation intensity, ambient temperature, and amount of water collected were measured during several periods in 2015.
Mathematical Model and Validation:
A mathematical model was developed to predict the system's water productivity based on solar radiation and temperature data. The model demonstrated a reasonable agreement with the experimental results, validating the system’s performance under various environmental conditions. The model predicted that water productivity is highly dependent on the temperature difference between the condensation surface and the surrounding air.
Challenges and Future Directions:
Although the system showed promise, the daily efficiency was relatively low, peaking at only 7%. This was primarily due to the limited condensation surface area and losses from evaporated water. Future improvements could include enhancing the surface area of the condensation surface and optimizing the positioning of the absorber to maximize exposure to sunlight.
Conclusion:
The use of a double slope condensation surface with solar energy and Calcium Chloride as a desiccant offers a viable approach to extracting water from atmospheric air in arid regions. With further optimization, this method could become a sustainable solution for remote and water-scarce areas, offering clean water without the need for extensive infrastructure.
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