Abstract. In the present paper, a humidification-dehumidification desalination unit integrated with solar system is considered. In the first step mathematical model of the whole plant is represented. Next, taking into account the logical constraints, the performance of the system is optimized. On one hand it is desired to have higher energetic efficiency, while on the other hand, higher efficiency results in an increment in the required area for each subsystem which consequently leads to an increase in the total cost of the plant. In the present work, the optimum solution is achieved when the specific energy of the solar heater and also the areas of humidifier and dehumidifier are minimized. Due to the fact that considered objective functions are in conflict, conventional optimization methods are not applicable. Hence, multi objective optimization using genetic algorithm which is an efficient tool for dealing with problems with conflicting objectives has been utilized and a set of optimal solutions called Pareto front each of which is a tradeoff between the mentioned objectives is generated.
IntroductionWater demand already exceeds supply in many parts of the world and as the world population continues to rise, so does the water demand. It is expected that by 2025, more than 60% of world's population will have water shortages [1]. Regarding the fact that seawater is one of the most convenient sources of water, desalination can be a practical solution to this concern. Desalination refers to a process which removes salt and other minerals from water resulting in having fresh water. The required energy for this purpose can be provided by different sources including refrigeration cycle [2], combined cogeneration cycle, heat pump [3] or solar system. Limitation of natural gases and oil in addition to their undesired effect on environment arises more interest in application of renewable sources of energy. Due to the fact that solar energy has a good consistency with climatic conditions in regions which need potable water, it can be considered as an appropriate source of energy. It is noteworthy that among the various desalination technologies in use, only those based on a thermal principle of operation must be considered in combination with solar ponds [4].Additionally, many of the remote arid areas need low capacity desalination systems, while conventional desalination methods such as MSF, MEE, VC and RO are suitable for large and medium capacity of fresh water production; therefore utilizing mentioned methods for small capacity systems is not economical. Humidification-dehumidification desalination is a suitable choice for production of fresh water when the demand is decentralized [5]. A significant advantage of the HD technology