# Unveiling the Potential of Solar-Powered Multistage Hollow Fiber WGMD: A Transient Performance Evaluation

## TL;DR

This study evaluates a solar-powered hollow fiber membrane distillation system, showing how it can efficiently produce freshwater using solar energy.

## Contribution

A novel CFD model coupled with a solar collector model is developed to evaluate transient performance of solar-driven desalination systems.

## Key findings

- Increasing collector area from 10 to 50 m² boosts average water flux by 6.4 times.
- Multistage configurations reduce solar energy demand and improve desalination efficiency to 57.5%.
- A 40-stage system with 10 m² collectors achieves 51.5 kg/day freshwater productivity.

## Abstract

Solar-energy-driven membrane distillation provides a sustainable pathway to mitigate freshwater scarcity by utilizing an abundant renewable heat source. This study develops a two-dimensional axisymmetric computational fluid dynamics (CFD) model to simulate the transient performance of a hollow fiber water gap membrane distillation (HF-WGMD) module integrated with flat-plate solar collectors (FPCs). A lumped-parameter transient FPC model is coupled with the CFD framework to predict feed water temperature under time-varying solar irradiation, evaluated across four representative days in a Mediterranean city. The model is validated against experimental data, showing strong agreement. A comprehensive parametric analysis reveals that increasing the collector area from 10 to 50 m2 enhances the average water flux by a factor of 6.4, reaching 10.9 kg/(m2h), while other parameters such as collector width, tube number and working fluid flow rate exert comparatively minor effects. The module flux strongly correlates with solar intensity, achieving a maximum instantaneous value of 18.4 kg/(m2h) with 35 m2 collectors. Multistage HF-WGMD configurations are further investigated, demonstrating substantial reductions in solar energy demand due to internal thermal recovery by the cooling stream. A 40-stage system operating with only 10 m2 of solar collectors achieves an average specific thermal energy consumption of 424 kWh/m3, while the overall solar desalination efficiency improves dramatically from 2.6% for a single-stage system with 50 m2 collectors to 57.5% for the multistage configuration. The proposed system achieves a maximum freshwater productivity of 51.5 kg/day, highlighting the viability and optimization potential of solar-driven HF-WGMD desalination.