Water Desalination Using Solar Energy

Abstract

Water desalination is receiving increasing attention due to water scarcity in many places in the world. Although two third of the earth is covered with water, most of this water is salty (97.5%) and therefore not suitable for human, animal or plant needs. Furthermore, most of the fresh water available throughout the work is not accessible such as icebergs and some deep ground water. Water uneven distribution throughout the world creates another problem of water scarcities in arid places. Africa and Middle East are having the smallest share of natural, pure water resources. Fortunately, these areas of arid climate and low fresh water are rich in the most significant renewable energy source, solar energy. In this chapter, the potential of the utilization of renewable energy sources is discussed. Several desalination techniques that can be powered by renewable energy are discussed. Those techniques include the non-conventional ones such as the solar stills, humidification dehumidification desalination and membrane distillation. What is common within all of these techniques is the relatively low temperatures needed to operate the plants (around 80 °C) that can be afforded easily using solar collectors for heating water (and sometimes air). Several layouts of humidification dehumidification systems and membrane distillation system are also discussed in details taking into consideration the improvement of performance due to energy recovery systems and the recent trends of such technologies. Although the solar energy is basically free source of energy, how good this energy is utilized in operating the desalination systems is considered in the gain output ratio (GOR) that allows for comparison of different systems comparison and shows the room for improvement.