IMPROVEMENT OF THE EFFICIENCY OF A SMALL DESALINATION UNIT FUNCTIONING BY AIR HUMIDIFICATION AND DEHUMIDIFICATION BY USING AIR FLAT-PLATE SOLAR COLLECTORS

摘要

The south Mediterranean area is suffering from lack of drinking water. However, brackish water is abundant. Desalination of such water can be a solution to provide the needs of the local population. Different solutions for brackish water desalination have been developed and many prototypes have been built and tested. Bourouni et al (1999) have developed a water desalination plant based on Aero-Evapo-Condensation Process (AECP). A prototype has been built and tested in the south of Tunisia. A geothermal brackish water source has been used to feed the unit. Promising results have been found (Bourouni et al, 1999). A second study (Bourouni et al 2003), has shown that the geothermal source can be replaced by solar preheated water. Two different configurations of the plant have been studied by detailed simulations. An economical analysis has shown that the desalination of brackish water using this process can be very competitive. For a small unit producing 2.73 m{sup}3 of fresh water per day, the cost was as low as 1.58 USD per cubic meter of fresh water produced in the case of using solar energy. On the other hand, when the unit is coupled to geothermal spring this cost can be reduced to 1.2 USD per cubic meter of fresh water. These studies have shown that the AEC process can be fed either with geothermal source or a solar water heating system. The aim of the actual work is to improve the efficiency of the whole system by using air flat-plate solar collectors to preheat the air entering the evaporator of the AEC system. Warm air has a higher evaporative capacity than ambient air, and thus, the evaporation of brackish water will be faster and more efficient. TRNSYS simulations will be held to predict the performances of the new design of the system. A life cycle cost analysis of the new system design will be held to evaluate the cost of a cubic meter of fresh water produced by this innovative process.