The document discusses various methods for desalination of water, including distillation, freezing, and reverse osmosis. It provides details on solar distillation, including that it is inexpensive but produces low volumes of water. It also notes that desalination by distillation produces water without chemical salts and is effective at removing various impurities. The document compares passive and active solar distillation, and discusses different designs of solar stills as well as methods for increasing their productivity and efficiency. It also provides an overview of desalination by freezing, including direct and indirect freezing processes.

1. By:
Mariam Ibrahim
Hadeer Mohammed

7. Local fresh water
demand
=
local fresh water
supply

12.  Is the process of turning saline water into
fresh one
 (thermodynamic processes): a work driven
process that undergoes the irreversible
mixing of salts into water

14.  .

16.  Chemical separation processes to remove
dissolved ions
 More intensive energy
 Fossil fuel costs high
 Solar energy as: abundant, renewable and
economic

19. Reverse osmosis
Freezing
Evaporation

24.  brine depth
 Vapor tightness of the enclosure
 Distillate leakage
 Methods of thermal insulation
 Cover slope
 Material
 Shape

26.  19th century
 Insulated basin
 Solar radiation
 Basins painted black to: increase solar
absorption and long wave length
radiation
 Flushing to prevent salt ppt

28.  solar distillation is inexpensive. The volume
of water produced is generally low.

29.  Desalination by distillation produces
water without chemical salts
 Desalination/evaporation/distillation is
very effective for:
 Bacteria
 Viruses
 Protozoa
 Helminths
 Turbidity
 Chemicals
 Salt and hardness
 Taste, odour,colour

30.  Simple
 Low-cost
 Fuel available
 Pots boil and poured

31.  Desalination/evaporation can be applied
on both the household level and the
community level (for villages, schools,
etc).

32.  more efficient
 expensive stills
(Aqua Solaris)
have been tried that can
increase volume to
40litres per m2 per day.

33.  High water temperature
 Cool surface for condensation
 Gravity for water extraction
 Its constructed by local cheap material
 Avoid vapour leaks using silicon application
 Never allow still to dry

34.  Require a lot of energy
 Strong bond between salt and water
 Living species found in seas
 Cost gap

35. Passive
Active

36. It uses only solar energy
falling into the unit

37.  Uses external thermal energy source to aid in
heating
 Heat addition done by:
-concentrating solar panel
-thermal energy sources
-convention boiler
- flat plate collector to stills

38. Solar stills
acc. To
geometry
Vertical solar
still
Inverted
absorber
solar still
Multiple
effect
horizontal
Conical solar
still
Cascaded in
shallow pools
of water with
cascade slope

40.  Follows: simple heat and mass balance
 Include: external source of heat, a solar
heater and vacuum pump to enhance
evaporation rate

42. Productivity
increasing
Add energy
units
Increase
energy input
Lower
condense
Surface
Heat recovery
Low ambient
temp.
Lower depth
Decrease
gaps
Mass surface
area

46.  The functional integration of solar still in
water collection, evaporation and
condensation
 This configuration leads to thermal
inefficiency

49.  The desalination waters by
freezing is a well-known process
and relies on the principle that
the structure of an individual ice
crystal does not accommodate
salts.
 Therefore, during the freezing of
a salt solution, salts are rejected
by the growing ice crystals. The
crystals can be separated from
the concentrated solution, which
is rejected as brine, and melted
to yield pure water.

51. 1) Direct freezing :
It refers to any process involves three discrete steps in
obtaining fresh water from a saline source:
ice formation by the heat removal of saline water,
separation of ice from the brine, and melting of the ice.

52. 2) Indirect freezing process:
 In indirect freezing process, saline water does not
come into contact with refrigerant directly.
 Ice is formed on a surface by mechanical
refrigeration or other methods.

54. 1) The energy requirements tend to be relatively
high.
2) Large metallic heat transfer surfaces are required
for both the freezing and melting steps.
3) The equipment is complex, expensive, and
difficult to operate and maintain.

56. Any questions ??