Water 2022, 14, 3424. https://doi.org/10.3390/w14213424 www.mdpi.com/journal/water Review Solar Desalination by Humidification–Dehumidification: A Review Nejib Ghazouani 1,2, *, Alaa A. El-Bary 3 , Gasser E. Hassan 4 , Nidhal Becheikh 1 , Abdulhakim Bawadekji 5 and Mahmoud M. Elewa 3, * 1 College of Engineering, Northern Border University (NBU), Arar 73222, Saudi Arabia 2 Civil Engineering Laboratory, National Engineers School of Tunis (ENIT), University of Tunis El Manar, Tunis 1002, Tunisia 3 Arab Academy for Science, Technology and Maritime Transport, College of Engineering and Technology, P.O. Box 1029, Alexandria 21934, Egypt 4 City for Scientific Research and Technological Applications, New Borg El Arab City, Alexandria 21934, Egypt 5 College of Science, Northern Border University (NBU), Arar 73222, Saudi Arabia * Correspondence: nejib.ghazouani@nbu.edu.sa (N.G.); mahmoud.elewa@aast.edu (M.M.E.) Abstract: The scarcity of drinkable water supplies is becoming a serious and troubling challenge to long-term development. This issue emphasises the urgency of implementing rapid water desalina- tion options. However, desalination is a capital-intensive process that requires a significant amount of energy, and since it is now mostly powered by fossil fuels across the globe, it has the potential to leave a significant carbon footprint. In this light, transitioning to green energy sources for desalina- tion is a necessity in today’s society. Humidification–dehumidification (HD) is one of the most ef- fective desalination procedures to consider for distant places with modest fresh water demands for household and agricultural demands. This is mostly because it requires minimal operational and maintenance concerns. The current article examines the many kinds of HD desalination systems driven by solar energy sources and their key components. The current study established that the seawater HD system is viable for producing fresh water, especially for greenhouses and dispersed demand. HD is an effective technique for eluting fresh water from concentrated brines, boosting production, and minimising harmful environmental impact, benefitting ecosystems and human ser- vices. The packed bed humidifier is the most commonly used kind of humidifier in the HD water desalination system. Additionally, as compared to an indirect dehumidifier, the direct dehumidifier improves the performance of the HD desalination system. According to the findings of this research, hybrid energy systems have the greatest gain output ratio (GOR). Solar water heating significantly increases system productivity as compared to solar air heating. When combined with a heat pump, the HD delivers optimal system productivity and GOR at the lowest cost per litre. The conclusion is that, even though humidification–dehumidification is a promising method for decentralised small-scale fresh water production applications, it needs additional improvement to optimise sys- tem performance in terms of economy and gain output ratio. Keywords: greenhouse desalination; humidification–dehumidification of air; renewable energy 1. Introduction Water is essential to the beginning and continued existence of humanity. Because it covers almost three-quarters of the earth’s surface, water is one of the most abundant re- sources on the planet. The oceans contain approximately 97% of the water on Earth, which is salt water. The remaining 3% of the water on Earth is fresh water, which can be found at the poles (in the form of ice), in ground water, lakes, and rivers. Fresh water supplies the majority of the water that is needed by humans and animals. Glaciers, areas with Citation: Ghazouani, N.; El-Bary, A.A.; Hassan, G.E.; Becheikh, N.; Bawadekji, A.; Elewa, M.M. Solar Desalination by Humidification–Dehumidification: A Review. Water 2022, 14, 3424. https://doi.org/10.3390/w14213424 Academic Editors: Chunyan Wang, Lu Lin, Chao Zhang and Shen Qu Received: 15 September 2022 Accepted: 19 October 2022 Published: 27 October 2022 Publisher’s Note: MDPI stays neu- tral with regard to jurisdictional claims in published maps and institu- tional affiliations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/license s/by/4.0/).