Analytical and experimental study of performance of Pyrex glass Q-dot based passive solar still glass evaporator

Abstract

• Solar still’s performance is investigated with Pyrex glass-based Q-dot material and results are compared with conventional SS. • Solar still’s theoretical performance validated by experimental work with 7.6 % deviation at maximum. • QD concentrations of 0gm, 5gm, 10gm and 15gm with black paint are used to enhance the performance of SS. • With 0gm and 15gm Q-dot, unit produces 991 ml/m 2 and 2710 ml/m 2 experimentally with 15.21% and 41.22% energy efficiency and 0.50% and 2.75% exergy efficiency. • Economic analysis shows 2.62 and 1.14 Rs./l of distilled water and payback period of 4.81 and 1.98 years for SS with 0gm and 15gm QD. The present work demonstrates the experimental and analytical study of passive single slope Solar still (SSSS) under the tropical condition of Varanasi (25.3176° N, 82.9739° E), India. A novel Pyrex glass-based quantum dot (QD) material is used that has high solar absorptance property which is governed by its shape and size to absorb a range of solar radiation. Two sets of experiments were performed on two similar solar still of equal absorber area of 1 m 2 made of fiber-reinforced plastic (FRP) placed at a tilt angle of 25° from the horizontal surface and facing southward. Four different concentrations of QD material were developed as 0gm (conventional SS), 5gm, 10gm, and 15gm with the black dye of 500 ml and coated on the inner surface of the basin. Several experimental investigations were conducted in October month at a basin water depth of 0.02 m. The experimental result showed a maximum yield of 991 ml, 1282 ml, 2010 ml, and 2710 ml with energy and exergy efficiencies of 15.21% and 0.50%, 19.68% and 0.84%, 30.57% and 1.41%, 41.22% and 2.75% for SS with 0gm, 5gm, 10gm, and 15gm QD material respectively. It was observed that QD-black dye coating enhances the absorptance of FRP that enabling it to attain the high temperature. Also, the convective heat transfer coefficient (HTC) from the basin to the water gets affected by different concentrations of QD that further triggered the HTCs from water to glass. Convective heat transfer coefficient increases with wind velocity, on average 3 m/s velocity on a day convective HTC reached at 11.8 W/m 2 K. Theoretical modeling was also performed which was validated by experimental results that shows a maximum 7.6 % deviation. Moreover, the economical study was also performed to check the feasibility of SS that predict 1.14 Rs./l and 2.62 Rs./l of distilled water for 15 years of life span and at a payback period of 1.98 years and 4.81 years at a selling prize of Rs. 5 only