Monthly performance of passive and active solar stills for different Indian climatic conditions

The monthly performance of passive and active solar stills for different Indian climatic conditions was evaluated. Numerical computations were carried out for hourly variations of average insolation at the Chennai, Jodhpur, Kolkata, Mumbai and New Delhi stations. The analysis was based on the quasi-steady-state condition. Analytical expressions for water temperature, glass cover temperature and yield as a function of climatic parameters - namely solar intensity, ambient air temperature and design parameters (water depth, absorptivity of basin liner, wind velocity, bottom insulation and cover inclinations) - were also derived. On the basis of numerical computations, it was inferred that: (1) the annual yield significantly depends on water depth, inclination of condensing cover and collector as expected for both passive and active solar stills; and (2) the annual yield for a given water depth increases linearly with the collector area for an active solar still.