Performance and feasibility analyses of evacuated U-tube solar collector driven humidification-condensation based wastewater recovery system

• Developed FDM based thermal model to assess sustainable SCHW performance. • Conducted thorough parametric and performance analyses on novel SCHW system. • Performed feasibility analysis of SCHW system for various climatic regions in India. • SCHW is effective in hot and dry region with a 0.78 L/h-m 2 water extraction rate. • SCHW significantly improves sustainable water management in scarce water areas. This research presents a sustainable humidification-condensation system for freshwater extraction from wastewater, utilizing an evacuated U-tube solar collector powered by solar energy. The efficiency of the newly proposed system is evaluated by developing a thermal model and solving it through a finite difference approach. The humidifier and condenser module were validated individually against experimental data, and the maximum possible error is estimated at ±12 % and ±10 %, respectively. The developed thermal model shows strong predictive capability for the humidification-condensation based wastewater recovery system, with R 2 values of 0.9987 (energy exchange), 0.9944 (water extraction rate), 0.9850 (condensate), 0.9492 (humidified air), 0.9793 (humidity ratio), and 0.9559 (cooling water temperature), all within acceptable error margins. Analysis of various parameters alongside the performance evaluation of the proposed novel system was conducted using the developed model. The parametric analysis revealed that the solar exit water temperature significantly impacts the performance of the novel systems. Moreover, performance assessments show that the system benefits from lower water temperatures at sources like dams, rivers, or seawater, as well as from a more effective water condenser and a higher flow rate. Further analysis of condenser effectiveness, fluid flow ratio, and cooling water temperature indicates maximum achievable water condenser energy exchange (WCEE) and water extraction rate (WER) of 1.37 kW/m 2 and 1.445 L/h-m 2 , respectively. The evaluation determined that the proposed sustainable system is ideally suited for hot and dry climates, with a potential WCEE and WER of up to 0.8 kW/m 2 and 0.78 L/h-m 2 based on the system’s specifications and operating parameters. Additionally, WER increased by 71 % and 62 % with an increase in solar energy input at given wastewater temperature and air flow rate in the humidifier. An assessment of the correlation matrix revealed that the specific humidity of humidified air strongly influences moisture energy exchange (correlation ( r ) = 0.92), while air inlet temperature is the key factor affecting WCEE ( r = 0.96) and WER ( r = 0.98), indicating its critical role in system performance for hot and dry regions. The current study provides insights into solar potential hotspots for wastewater recovery across different climatic conditions.