Integrated optimization of a solar-powered polytetrafluoroethylene–air gap membrane distillation system for freshwater production

Abstract

This research examines the combined optimization of a solar-powered air gap membrane distillation (AGMD) system using a polytetrafluoroethylene membrane for eco-friendly freshwater generation. A blend of numerical simulations and experimental testing was used to study heat and mass transfer and to improve critical operational parameters under solar conditions outdoors. The system utilized a 6-m2 flat-plate solar thermal collector, functioning under peak solar irradiance of 960 W·m−2, capable of generating as much as 150 l·day−1 of distilled water. Experimental results indicated that the flux of permeate increased significantly with the temperature of the feed, peaking at 7.4 kg·m−2·h−1 at 83°C using an air gap thickness of 1.04 mm and a feed flow rate of 5 l·min−1. Adjusting the air gap from 1 to 5 mm resulted in a decline of permeate flux from 10.0 to 4.5 kg·m−2·h−1 at 60°C, highlighting the significant impact of diffusion resistance. The numerical model estimated flux values with variances of less than ±0.5 kg·m−2·h−1, which indicates a strong correlation with experimental outcomes. The conductivity of the permeate stayed under 20 μS·cm−1, showcasing excellent salt rejection capabilities. The findings support that a solar-driven AGMD system is an effective decentralized desalination method for regions with high solar irradiance, though future enhancements should focus on integrating thermal storage and evaluating long-term fouling issues.