GROUP 9
- S. Prashanth Kumar
- R. Gautam Reddy
- S. Prithvi Raj
Global Stats & Facts
Availability of fresh water supply for agricultural,
industrial and domestic uses is reaching critical
demands.
1.1 billion people around the world have no access to
clean drinking water.
The World Health Organization reports that
contaminated water contributes to 80% of all sickness
and disease worldwide.
The total amount of water available on earth has been
estimated at 1.4 billion cubic kilometres, enough to cover the
planet with a layer of about 3-km deep.
Desalination
Desalination refers to any of several processes that
remove excess salt and other minerals from water for
○ Human Use
○ Irrigation
○ Animal use
Concentration Of Salt
Fresh Water Less than 0.5 ppt
Brackish Water 0.5-30 ppt
Saline Water 30-50 ppt
Brine Greater than 50 ppt
Desalination Techniques
Distillation
– Multi-stage flash distillation
– Multiple effect distillation
Membrane processes
– Reverse osmosis
Solar Humidification (Solar still)
Distillation
Multi-Stage-Flash Distillation:
The leading method
The traditional process used in these operations is
vacuum distillation-essentially the boiling of water at
less than atmospheric pressure and temperature.
Lesser energy requirement
Multi-Effect
Single Effect
Multiple-Effect
Distillation
Reverse Osmosis Reverse osmosis (RO) is a filtration method that removes
many types of large molecules and ions from solutions by
applying pressure to the solution when it is on one side of a
permeable membrane.
The result is that the solute is retained on the pressurized
side of the membrane and the pure solvent is allowed to
pass to the other side.
Overview:
Uses electricity rather than heat
Proven technology
For a typical community level solar powered RO
plant:
PARAMETER VALUE
Capacity (lit/day) 2000
Feed Salinity (ppm) 2000 – 2500
Product Recovery (% ) 70 - 80
Pressure (kPa) 1.1 x 103 – 1.2 x 103
Power Requirement (kW) 1.6 - 1.8
Product Salinity (ppm) 200 - 250
Solar Desalination
The process is based on the use of solar thermal energy to evaporate water, thus separating pure water from brine.
Direct Solar Desalination:
Indirect Solar Desalination
Direct Solar Desalination
Still Humidification-Dehumidification
HD
Single-effect Multi-effect
Direct Solar Desalination
Single-effect Stills
Water production < 6 liters/m2,day
Examples:
Basin stills
Wick stills
Greenhouse integrated stills
basin-type solar still
Basin still with radioactive cooling
Condenser
◦ Packed Bed
◦ Cooled during night
Evaporator
◦ Solar still
◦ Natural Convection
Production
◦ 5-6 litres/m2,day
SOLAR STILL OUTPUT DEPENDS ON MANY
PARAMETERS
Climatic Parameters
Solar Radiation : The still output increased from 1.76 liters/m2 day at 16.74 MJ/m2 day to 5.11 liters/m2 day at 27.08 MJ/m2 day.
Ambient Temperature: An increase in still output was observed with increase in ambient temperature. The increase in output is about 0.87 liters/m2 day for each 10°C rise in ambient temperature.
Operational parameters
Water Depth: Higher distillate output was
observed with lower water depth.
Preheating of Water
Coloring of Water: The effect of dye on water
output was also studied. The output got increased
by colouring the water.
Multiple-effect basin stills
have two or more compartments.
The condensing surface of the lower compartment is
the floor of the upper compartment.
The heat given off by the condensing vapor provides
energy to vaporize the feed water above.
Efficiency is therefore greater than for a single-basin
still typically being 35% or more but the cost and
complexity are correspondingly higher.
Direct Solar Desalination
Humidification - Dehumidification
Water production 1 - 20 litres/m2,day
HD with open-air cycle
HD with open-air cycle
Humidification
◦ Water heating by
solar collector
Dehumidification
◦ Ambient air
Production◦ 6 litres/m2,day
Solar Air Conditioning
Air conditioning is the control of the indoorenvironment by controlling the thermalcharacteristics mainly heating and coolingthe air supplied to the room.
Solar air conditioning refers to the use ofsolar energy to power a cooling appliance.
Days that have the greatest need forcooling are also the very same days thatoffer the maximum possible solar energygain.
There are several basic types of solar
cooling technologies
1. Absorption Cooling
2. Desiccant Cooling
3. Vapor Compression Cooling
4. Photovoltaic Solar Cooling
5. Evaporative Cooling
Absorption Cooling
The basic principle behind solar-thermaldriven cooling is the thermo chemicalprocess of absorption of a liquid or agaseous substance into a liquid or a solidmaterial.
Solar cooling uses the solar collectors toprovide thermal energy to drive thermallydriven coolers.
The usefulness of a given absorbent -refrigerant pair is determined by thetemperature dependence of vaporizationand absorption process.
LiBr – water solar cooling system
Desiccant Cooling
Desiccant cooling is a new and cleantechnology which can be used to cool theinside air of the buildings without using anyharmful refrigerants.
Desiccant cooling systems are basicallyopen cycle systems using water as arefrigerant in direct contact with air.
Desiccants like silica gel or zeolite drawmoisture from the air and they areregenerated by using solar thermal energy.
Desiccant cooling system
Desiccant Cycle
In a vapor compression cooling , the solar
thermal energy is used to operate a Rankine
cycle heat engine
The solar power also converted to electricity
can be used to run the air conditioning
systems.
Evaporative cooling is to spray water into dry
air where the temperature is reduced by
evaporation water into the air.
Zero energy building
Conclusions
Integrating desalination units with renewable energy sources
is important for addressing the issues related to adverse
impacts of climate change.
Also, for remote areas, where scarcity of power and water
co-exist, the one and only solution to produce safe drinking
water is to go in for renewable energy sources.
With improvement in PV efficiencies and the subsidies
available, cost of PV systems is expected to come down,
making the solar PV based desalination systems more cost-
effective.
Reference
http://en.wikipedia.org/wiki
http://www.solarserver.com
http://www.daviddarling.info/encyclopedia
http://www.solarcoolingtypes.com/
http://www.solair-project.eu/146.0.html
Renewable energy conversion transmission and storage – Bent Sorensen
THANK YOU
Top Related