Abstract
The present experimental study aims to improve the productivity of a stepped solar still. The stepped solar still using PCM as latent storage materials with stillinternal reflectors integrated with an evacuated tube collector (first case) and a stepped solar still using a graphite and PCM as hybrid storage materials with still internal reflectors integrated with an evacuated tube collector (second case) was designed, implemented and operated at Tanta University under the climatic conditions of Egypt to obtain the better configuration. This study illustrated to effects the graphite, PCM, still internal reflectors, and evacuated tube solar collector on the stepped solar still performance. The results show that the daily distillate productivity was varied between 11.24–11.29 and 13.6–13.62 L/m
2
day for the first case and the second case, respectively. The daily efficiency was varied between 42.55–42.62% and 51.7–51.82% for the first case and the second case, respectively. These results indicated that the second case is more effecient than the first case. The percentage improved in the daily productivity for the second case as compared to thefirst case varied between 20.64 and 21.05%. Also, the percentage improved in the daily efficiency for thesecond case compared to the first case varied between 21.48 and 21.64%. Due to increase the hot brackish water flow rate from 15 to 35 ml/h, the daily productivity increases from10.54 to 12.08 l/m
2
and from 12.88 to 14.42 l/m
2
for the first case and the second case, respectively.