Performance of a solar still integrated with evacuated tube collector in natural mode

•Thermal modeling of an ETC integrated solar still carried out in natural mode.•Performance evaluation for yield, energy and exergy efficiencies.•System has been optimized to find best combination between in the size of ETC and water depth.

This paper presents the thermal analysis of a solar still integrated with evacuated tube collector in natural mode. Performance has been predicted theoretically in terms of water and inner glass cover temperatures, yield, energy and exergy efficiencies during typical summer day of New Delhi (India). The variation of instant overall energy and exergy efficiencies has been found to be in the range of 5.1–54.4% and 0.15–8.25% respectively during the sunshine hours for 0.03 m water depth, which decreases with increase in depth. Further, the system has been optimized for the number of evacuated tubes integrated and water depth in basin for nearly the same maximum water temperature attainable (≈ 94 °C) in each combination. The best combination among has been found by integration of 10 evacuated tubes with water depth of 0.03 m (total 52.5 kg water mass) in the basin. The respective daily energy and exergy efficiencies have been obtained as 33.0% and 2.5% and maximum among with daily yield of 3.8 kg/m2.