Enhanced productivity in passive solar desalination using fresnel lens and conductive particle assisted phase change material in tropical climate

Tan, Jia Hui (2026) Enhanced productivity in passive solar desalination using fresnel lens and conductive particle assisted phase change material in tropical climate. Master dissertation/thesis, UTAR.

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Abstract

Solar desalination provides a sustainable solution to freshwater shortages caused by environmental issues like water pollution and global warming. However, conventional solar stills often produce insufficient water, unable to meet even a single household's needs. Ongoing research aims to improve their productivity, with promising approaches such as Thermal Energy Storage (TES) systems and sunlight concentrators. TES stores excess energy during peak sunlight hours, enabling continued water production during cloudy periods or after sunset, improving efficiency and reliability. Sunlight concentrators, like lenses, focus solar radiation onto the evaporative surface, increasing temperature and evaporation rates, thus enhancing the distillation process. This study combines concentrators and TES to enhance the performance of a simple passive single-slope solar still. The Fresnel lens was used as the concentrator, while paraffin wax, a phase change material (PCM) with added conductive particles, served as the TES. Four sizes of Fresnel lenses (FL 12.7 cm, FL 9.9 cm, FL 20 cm, and FL 33 cm) were tested, along with four types of conductive particles: Al scrap, Al2O3 nanoparticle, Cu nanoparticle, and Al2O3 + Cu nanoparticle. In indoor tests, Al2O3 + Cu nanoparticle showed the best performance. Outdoor tests revealed that the largest Fresnel lens resulted in over 150% higher water yield than the other smaller Fresnel lenses used in the study; regardless of the conductive particle used, with Cu and Al2O3 + Cu particles showing similar high performance. Interestingly, the performance of Al scrap was similar or higher in performance in some experiments. After conducting an economic analysis, it was discovered that the model implementing Al scrap PCM has the lowest cost per litre per area. Hence, the actual size prototype proceeded with the combination of FL 33 cm Fresnel lens and Al scrap Fresnel lens, which achieved a water yield of 3.3030 kg/m2, productivity of 2.34 g/kJ.m2, efficiency of 35.34 %, and the estimated cost per litre per unit area is 0.004 $/(kg/m2). Keywords: Solar desalination, single slope passive solar still, phase change material, nanoparticles, aluminium scrap, Fresnel lens, concentration ratio

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