Enhancing tubular solar still productivity: A novel rotational absorber, ultrasonic atomizer, and hygroscopic fabric integration

Abstract

Freshwater scarcity is a growing global challenge, particularly in regions with abundant solar energy but limited access to clean water. Conventional solar stills offer a sustainable solution for freshwater production but suffer from low productivity and efficiency, limiting their practical application. This study addresses these limitations by introducing a novel tubular solar still design with operational enhancements aimed at significantly improving freshwater productivity and thermal efficiency. Key innovations include a centrally suspended rectangular absorber plate with an adjustable rotational mechanism, microcontroller-regulated rotational velocity control, and an ultrasonic atomizer at the still's apex to intermittently disperse water droplets for enhanced evaporation. Hygroscopic burlap fabrics (cotton and jute) were layered on the absorber to amplify surface evaporation. Comprehensive experiments optimized rotational speeds (0–2 rpm) and atomizer duty cycles (fixed 1-min activation with varied deactivation intervals: 2–10 min) to maximize freshwater yield through parametric refinement of rotational dynamics and misting cycles. Key parameters contributing to the system's performance include thermal efficiency, freshwater yield, cost-effectiveness, environmental impact, and durability. Experimental results demonstrated that the modified tubular solar distiller (MTSD) with a rotational suspended absorber increased freshwater yield by 18 % compared to the reference system (RTSD). Jute cloth outperformed cotton, achieving a 90 % productivity improvement versus 82 % for cotton. Optimal performance occurred under conditions combining jute cloth, 1 rpm rotation, and an atomizer duty cycle of 1 min ON/8 min OFF, yielding a 97 % productivity increase (6795 mL/m² for MTSD versus 3450 mL/m² for RTSD) and 49 % thermal efficiency, significantly surpassing the RTSD baseline. Life-cycle cost analysis demonstrated a 52 % reduction in unit production costs for the MTSD configuration with jute-based rotational operation (1 rpm), achieving 0.013/L, compared to 0.025/L for RTSD. These results underscore the efficacy of the design enhancements in maximizing solar still productivity, offering a promising solution to address freshwater scarcity in resource-limited settings.