Effects of amount and mode of input energy on the performance of a multi-stage solar still: An experimental study

• Indoor experiments were performed on two multi-stage active solar stills.
• Effects of the amount and mode of energy input were studied.
• Distillate production was a quadratic function of collector over basin area ratio.
• Impulsive energy input mode increased distillate production by only 5–10%.

Effects of the amount and mode of input energy to an active multi-stage solar still were investigated in this work. To control the input energy, an electrical heater controlled by a PLC was utilized to simulate the energy absorbed by solar collectors. The study of the amount of input energy indicated that the freshwater production was a quadratic function of the collector over basin area (CBA) ratio. It was also found that stages 1 to 4 produced about 36%, 26%, 20% and 18% of the overall yield, respectively. Moreover, the effect of employing a thermal energy storage (TES) on the system performance was studied by comparing the mode of feeding energy according to the daily solar radiation pattern with the impulsive pattern (feed all of the energy at the beginning of the experiment). The current results showed that using TES increased the still's production by merely 5–10%. Thus, TES is suggested to be employed only if the CBA ratio is high and the system is not capable of operating at high temperatures.

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