Effect of wind velocity on active and passive solar still

The effect of wind velocity on the daily productivity of few active and passive solar stills is studied by computer modeling. Mathematical calculations have been carried out on extreme summer and winter days in New Delhi in order to correlate productivity with velocity for different masses of basin water for the passive stills and various thicknesses or mass flow rates of the flowing brine for the active stills. It is observed that for the active and multi-effect passive stills, productivity increases with the increase of velocity up to a typical velocity beyond which increase in productivity becomes insignificant. However, in all the investigated single effect passive stills, there is a critical depth of basin water beyond which productivity increases as velocity increases until typical velocity. For basin water masses less than the critical mass, productivity is found to decrease with increasing velocity until typical velocity. After typical velocity, the change in productivity is not important in a similar way to that obtained for the active and multi-effect passive stills. The critical depth of basin water for the observed single effect passive stills is found to be 4.5 cm. Moreover, the typical velocity is independent on the still shape and the operation mode (active or passive) but it shows some seasonal dependence. For the investigated stills, typical velocity is found to be 1.5 and 4.5 m/s on extreme winter and summer days, respectively.