Sustainable desalination through hybrid photovoltaic/thermal membrane distillation: Development of an off-grid prototype
Farzaneh Mahmoudi, Derrick Ng, Kian Siong Ang, Zongli Xie
Abstract
• Developed an innovative hybrid PV/T-MD system for sustainable desalination. • Necessitated robust control in outdoor trials due to environmental fluctuations. • Achieved 8–16 kg/m 2 h permeate flux outdoors vs. 22–30 kg/m 2 h indoor operation. • Estimated PV/T panel efficiencies at 10–18 % (electrical) and 15–20 % (thermal) • Proposed enhancements for scalability and practical application in remote regions. Global freshwater scarcity is a critical challenge, particularly severe in remote Australian communities where seawater intrusion and aquifer salinisation exacerbate the need for alternative water resources. Conventional desalination technologies are energy-intensive and unsuitable for rural areas. This study introduces a novel, off-grid, sustainable desalination solution utilising solar-integrated membrane distillation (MD) technology. An innovative, stand-alone prototype combining a hybrid photovoltaic/thermal (PV/T) system with direct contact MD (DCMD) has been designed and developed. This fully integrated PV/T collector efficiently supplies the thermal and electrical energy required for the MD process. The photovoltaic panel generates the necessary electrical energy, while the heat from the PV panel warms the MD system’s feed solution, enhancing overall efficiency through the solar cell cooling effect. In addition, an innovative fan-cooled radiator equipped with two DC fans with a low power consumption rating was designed and customized to be applied as MD system cooling medium within the outdoor setting. The concept development and feasibility of the system are explored in detail through a comprehensive experimental investigation employing an innovative and practical approach to design and examine the integrated hybrid solar MD unit. This unique system was designed, constructed, and tested under dynamic outdoor conditions, during the summer season in Melbourne, to assess the integration strategy and evaluate its long-term operational performance. The performance of the integrated PV/T-MD system was evaluated using two commercial hydrophobic membranes with different pore sizes under various outdoor conditions and PV/T fluid flow rates. Key performance metrics analysed include solar irradiance intensity, temperature profiles of the PV/T panel and MD module, power, current and voltage profiles of the unit components, permeate flux, specific water productivity ( SWP ) and the thermal ( η thermPV/T ) and electrical ( η elecPV/T ) efficiencies, along with the gained output ratio ( GOR ). Comprehensive experimental assessments in indoor and outdoor settings were undertaken to confirm the technical viability of the system. The study demonstrates the feasibility of such systems through real-world trials and addresses key challenges in energy efficiency and internal heat recovery. The experimental trials demonstrated permeate flux values ranging between 8–16 kg/m 2 h outdoors, compared to 22–30 kg/m 2 h indoors, reflecting the impact of fluctuating environmental conditions. The system’s power consumption was measured 130–140 W, about one-third of the PV/T power rating. The maximum power generation reached 280 W in battery charging mode. achieving a maximum η thermPV/T of 20 % and an η elecPV/T of 18 %. Additionally, the cooling effect of the PV/T panel resulted in a 1.5–2 °C temperature reduction, improving electrical power output by 0.8–1.2 %. The findings highlight the significant potential of the system in providing reliable and efficient freshwater production in remote, off-grid communities, offering a scalable solution to address global water scarcity challenges.