Citation: Ali, S.; Al-Amri, F.; Saeed, F. Numerical and Experimental Performance Evaluation of a Photovoltaic Thermal Integrated Membrane Desalination System. Energies 2022, 15, 7417. https:// doi.org/10.3390/en15197417 Academic Editors: Sharul Sham Dol and Anang Hudaya Muhamad Amin Received: 9 March 2022 Accepted: 21 April 2022 Published: 10 October 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. 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/licenses/by/ 4.0/). energies Article Numerical and Experimental Performance Evaluation of a Photovoltaic Thermal Integrated Membrane Desalination System Sajid Ali *, Fahad Al-Amri and Farooq Saeed Mechanical and Energy Engineering Department, Imam Abdulrahman Bin Faisal University, Dammam 31441, Saudi Arabia * Correspondence: sakzada@iau.edu.sa Abstract: Membrane desalination (MD) is preferred over other desalination techniques since it requires a lower temperature gradient. Its performance can be further enhanced by preheating the intake of saline water. In this context, a novel solar-assisted air gap membrane desalination (AGMD) system was hypothesized. The motivation was derived from the fact that the use of solar energy to provide power and a pre-heating source for the intake of saline water can offer a sustainable alternative that can further enhance the acceptance of MD systems. Since solar panels suffer from a loss of efficiency as they heat up during operation, a solar-assisted air gap membrane desalination (AGMD) system can help to improve the overall system performance by (1) providing the necessary pumping power to operate the system and (2) improving solar panel performance by exchanging heat using water that is (3) used to pre-heat the saline water necessary for increased performance of the AGMD system. To verify the hypothesis, a solar-assisted AGMD system for freshwater production was theoretically designed, fabricated locally, and then tested experimentally. The effect of the process operating parameters and the ambient conditions on the overall performance of the proposed solar-assisted AGMD desalination unit is presented in detail, both theoretically and experimentally. The results indicated a direct correlation between the permeate flux, saline hot feed temperature, and hot feed flow rate. In addition, an inverse relationship between the cold feed temperature, cold feed flow rate, and the air gap thickness of the module was also observed and reported, thus, validating the hypothesis that a solar-assisted air gap membrane desalination (AGMD) system can help to boost performance. Keywords: membrane desalination; renewable energy; solar-assisted desalination; permeate flux; air gap membrane desalination 1. Introduction The continuing increase in the global human population has led to a continuous decline in access to fresh water [1]. The problem is further compounded by climate change due to the uneven redistribution of freshwater resources around the globe [2]. Well over a billion people around the world do not have access to safe drinking water [3]. It is estimated that by 2025, more than 2.8 billion people worldwide will face water shortages [4]. The urgency of increasing access to fresh water and providing alternatives is a major concern for humanity, in general, and the scientific community. Distillation has the potential to address this concern and it has been acknowledged and duly recognized as a practical approach to overcoming the problem of freshwater scarcity [5,6]. Distillation techniques employing various methods, such as reverse osmosis, multi-effects, multistage flashes, and membranes, are some of the possible ways to desalinate seawater [7,8]. In various regions of the world, large-scale reverse osmosis (RO) has been used to provide drinkable water from seawater [9]. The reverse osmosis and multistage flash techniques share the credit for producing the highest volume of fresh water in the world Energies 2022, 15, 7417. https://doi.org/10.3390/en15197417 https://www.mdpi.com/journal/energies