  The paper describes the experimental investigations of the performance of a
multi-stage water desalination still connected to a solar parabolic trough
(solar energy concentrator) with focal pipe and simple heat exchanger
(serpentine). The receiver length is 2 m and has a diameter of 6 mm. A diluted
solution of water-antifreeze is selected as working fluid. This solution is
flowing as cycle through the focal pipe and serpentine. The solution in the
heat exchanger is heated during the sunlight by means of solar energy
concentrator (solar parabolic trough). The parabolic trough is tracking the sun
using simple mechanism to collect the highest amount of solar radiation by
optimum angle. The receiver is covered with transparent borosilicate glass to
avoid the heat transfer by convection to the surrounding (i.e. the greenhouse
effect is utilized) and the space between the glass and tube is evacuated.
Aluminum serpentine of the heat exchanger is installed in the bottom of the
still. It is attached extremely with thermally insulated pipelines through the
trough. The fluid is forced flow using small pump which is powered by PV
system. The multi-stage solar still water desalination system was designed to
recover latent heat from evaporation and condensation processes in 2 stages.
The results of tests demonstrate that the system produces about 3.6 kg of fresh
water for only 5 hours from 10:00 to 15:30.the The system components were
fabricated and the overall system was assembled in International Center for
Science & High Technology & Environmental Science, Mahan, Iran.
