Integrated Optimization of a Solar-Powered Humidification-Dehumidification Desalination System for Small Communities

Fresh water availability is essential for the economic growth and development, especially in small and semi-isolated communities. In some of these communities fresh water may be scarce, yet brackish water from wells or seawater is often abundantly available. This motivates a need for cost-effective desalination at small scale capacity driven by renewable energy sources. This paper presents an integrated optimization model of a solar powered humidification-dehumidification (HDH) desalination system. The system under investigation is a water-heated system. The design variables include the sizing of solar collectors, storage tank, humidifier and dehumidifier, as well as air circulation flow rate and operating temperature. The objective of the optimization is to minimize the unit cost of the produced fresh water. Thermodynamic performance prediction is done by solving energy and mass balance equations for each of the system components, with consideration to hourly-varying solar irradiance that corresponds to a typical one year cycle. System cost is predicted via first-order estimators. A genetic algorithm is used to obtain the designs optimized for local climate and market. A case study discusses a desalination plant on the Red Sea near the city of Hurgada.