In this experimental work, the performance of a nanofluid-based solar still equipped with a dual-axis solar tracker system (STS) has been investigated through various viewpoints, i.e., daily and nightly fresh-water production, hourly and daily efficiency and cost. The proposed solar still consists of a conventional solar still (CSS), three Fresnel lens concentrator, and an active automatic STS. Moreover, the effects of deionized water, MWCNTs/water nanofluid with two mass fractions of 0.15 and 0.3%, as the heat transfer fluid (HTF), are studied on freshwater productivity to evaluate the appropriate HTF type. The daily, nightly, and total freshwater produced by the CSS with internal condenser is found to be 2180, 560, and 2740 mL/(m2.day), respectively. However, the CSS integrated with STS and Fresnel lens can produce daily, nightly, and total fresh-water of 5310, 1080, and 6390 mL/(m2.day), respectively. In addition, the results indicate that using MWCNTs/water nanofluid with a mass fraction of 0.3% enhances fresh-water productivity by 31.6, 7.4, and 27.5%, respectively, compared to that of pure water as HTF. The results reveal that by using the nanofluid with a mass fraction of 0.15 and 0.3%, the daily average efficiency is increased about 9.56 and 17.85%, respectively, compared to that of pure water as HTF.

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