# Upper glass cover equation I t g ht w minus

Fig. 48. Schematic of the regenerative solar still [54].Figure optionsDownload full-size imageDownload as PowerPoint slide

The BIM 189 balance equations for the system components are as follows:

First effect basin liner (b):equation(344)mbCbdTbdt=I(t)sAb−qw−qloss

Water in the first effect (w):equation(345)mwCwdTwdt=I(t)sAw+qw−qr,w−g1−qc,w−g1−qe,w−g1

Lower glass (g1):equation(346)mgCgdTg1dt=I(t)sAg1+qr,w−g1+qc,w−g1+qe,w−g1−qc,g1−wf

Water in the second effect (wf):equation(347)mwfCwdTwfdt=I(t)sAwf+qc,g1−wf−m?wfCw∂Twf∂xdx−qc,wf−g2−qr,wf−g2−qe,wf−g2

Upper glass (g2):equation(348)mgCgdTg2dt=I(t)sAg2+qc,wf−g2+qr,wf−g2+qe,wf−g2−qr,g2−sky−qc,g2−a

Total condensation rate:equation(349)dmewdt=he,w−g1(Tw−Tg1)(hfg)Tw+he,wf−g2(Twf−Tg1)(hfg)Twf

It was found that the productivity of the regenerative still is about 20% higher than that for the conventional still. Making the stills perfectly insulated increases their productivity two and one half folds. There is more positive effect due to insulation on the regenerative still compared with the conventional still. The wind speed has a significant effect on the productivity; ribosomes can increase the productivity of the still by more than 50% if the wind speed increased from 0 to 10 m/s. Also the thickness of water on top of the first glass cover and the mass flow rate of water going into the second effect have marginal effect on the productivity of the regenerative still.