You can define

The energy efficiency of the SS is defined as the ratio of the

transferred thermal heat for water evaporation to the total net solar

energy over the SS trough surface area.

Exergy efficiency

Energy efficiency gives a quantitative view of the of energy

effectively utilized desalinating process. In the other hand, exergy

efficiency introduces a qualitative view of highest possible useful

energy that can be produced from the SS under the operating

condition relative to the ambient temperature as a reference (Arif,

2008). The Exergy efficiency of the SS is given by the ratio of the

exergy output of evaporation to the exergy input from solar energy

(Petela, 2003).

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The important performance parameter for solar still is the water productivity, which is calculated over a day, months or year.

After sunshine hours, no radiation exists. Accordingly no solar energy inters the system while desalination continues due to thermal storage.

In this case to calculate the instantaneous energy efficiency you must calculate instantaneous water productivity and thermal energy storage.

calculate the energy required to desalinate the instantaneous productivity this is the energy output while the thermal storage energy represents energy input to the system

Divide the output energy by the input energy to get the instantaneous energy efficiency

You can notice that it decreases gradually after sunset tell vanishes nearly at mid night or before or after.

Respected Professor, Gamal B. Abdelaziz

Thanks for your Valuable suggestions to my query...

Regards - Kousik

Can you calculate the instantaneous Energy input (storage that decreases) and output (energy required for desalinate instantaneous yield)

Then instantaneous efficiency= Useful (energy required for desalinate instantaneous yield) / Energy input (storage that decreases)

Thanks

Welcome Subbarama Kousik Suraparaju

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