Experimental investigation of innovative hybrid solar desalination tower using heat storage and packing materials

Freshwater scarcity remains a critical global challenge, with solar desalination systems offering sustainable solutions for water-stressed regions. However, conventional solar stills suffer from limited productivity and efficiency constraints. While humidification-dehumidification (HDH) systems show promise for enhanced freshwater production, their integration with pyramid solar stills and thermal storage mechanisms remains underexplored. This study addresses this research gap by investigating a novel hybrid solar desalination system that combines a pyramid solar still with an HDH unit, enhanced by waste engine oil thermal storage and auxiliary air heating to extend operational hours and improve overall system performance. A comprehensive experimental investigation was conducted under authentic field conditions in Suez City, Egypt (29.87° N latitude, 32.53° E longitude) from 8:00 a.m. to 11:00 p.m., systematically examining the influence of critical operational parameters including feed water flow rate, air flow rate, and water height variation on system productivity. Three distinct packing materials were evaluated to identify optimal configurations for maximum freshwater yield. Results demonstrate significant synergistic effects of the hybridization approach: increasing feedwater flow rates from 0.156 kg/s to 0.233 kg/s enhanced hourly productivity by 163.3 %, while optimal airflow rate of 0.0442 kg/s yielded maximum daily water production of 9.03 L/m2. The HDH system achieved maximum daily productivity of 10.96 L/m2/day using Loaf packing material at optimized flow rates, while the pyramid solar still produced 6.09 L/m2/day at 1.5 cm water height. Economic analysis revealed competitive production costs of 0.0391 $/L for the HDH system and 0.01156 $/L for the pyramid solar still, demonstrating the technical and economic viability of this hybrid approach for sustainable freshwater production in off-grid applications. The study concludes that the integration of HDH units with pyramid solar stills, coupled with thermal storage and optimized operational parameters, significantly enhances freshwater productivity while maintaining economic feasibility, offering a promising solution for water-scarce regions with abundant solar resources.