Solar thermal energy combined with humidification–dehumidification process for desalination brackish water: Technical review

Abstract Water scarcity has become a chronic problem aggravated by climate change. One third of the world's population already lives in areas suffering moderate to high water stress; some 1.5 billion people lack ready access to drinking water. Desalination is in the course of becoming a major source of fresh water by tapping into the vast reserves of seawater and brackish water. Large scale desalination plants use either thermal or membrane processes which consume a great deal of energy. Economic implications of large energy requirements coupled with environmental concerns about carbon emissions spurred a growing interest in developing desalination processes that use renewable energy sources. Among these processes the humidification dehumidification (HD) of air, using solar energy, is a simple technology particularly suited for regions in developing countries where there is very low infrastructure and unskilled manpower. In this paper we review various technologies under investigation to desalinate saline water through HD of air and using solar thermal energy. A particular emphasis will be put on the various types of solar water heaters as well as the various designs of solar air heaters.