| dc.description.abstract | Good water in sufficient quantities is one of
the most important resources of concern to humanity.
It supports life on earth and determines the pattern
of human development. Unfortunately, most of the
earth's vast reserves of water are either too brackish
or too saline to be of potable use by humans and livestock.
The grow Lrq imbalance between the supply and the demand
of fresh water point to the inevitable fact that man
has to turn to the treatment of the vast mineralized
water reserves to augment that portion of the reserves
that goes through the hydrological cycle and is
naturally fresh water. conventional water treatment
methods rely on a large array of expensive machinery
and complex technologies which few developing countries
can afford. They also require large capital energy
input. Most developing countries are, however,
blessed with abundant sunshine which can, in theory,
be harnessed as a substitute for the conventional
and increasingly costly fossil fuels.
In solar distillation, the natural hydrological
cycle is copied on a small scale. Brackish or saline
water is held in a pan enclosed by a transparent
cover. The sun's radiation which enters the
enclosure evaporates the water. The vapour rises
and condenses on the underside of the cover. The
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distillate is drained off for use as fresh water.
The device in which the distillation process takes
place is a Solar Still.
The objectives of the research is to study the
various parameters that influence the performance
of a Solar Still and to investigate how the input
variables interact with one another with a view to
optimising Still design and performance. The study
also investigates the economic feasibility of solar
distillation in compare on with alternative meals
of producing fresh water in developing countries.
Four model stills are constructed from locally available
materials. The effects of solar radiatJon,
wind velocity, water depth, cover slope and of the
temperatures of water, vapor, glass cover and
ambient air on still productivity are studied ~ The
economic analysis compares the cost of solar
distillation with the cost of slow - sand filtration
and the average - cost rural water supply over a
20 year period of productive life.
The results of the study indicate that due
to the thermodynamic deficiencies of the single -
effect solar still, solar distillation is an
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extortionately costly source of fresh water.
Consequently, its application is limited to the
situations where alternative processes are either
physically or technically impracticabJc. Perhaps,
the most significant result of the study is the
establishment of a relationship between the
orientation of the collector surface and the collector
slope that maximises solar radiati0P collection.
The relationship is:
tan 8 = Cos (as - aw )
where B is the cover slope,
as is the solar azimuth angJ.e, and
aw is the wall azimuth anqle.
A few areas are cited for further investigation. | en |
