Final Systems Presentation Sahaj

Solar Thermal water Distillation/Desalination Process

1Environment and Sustainability

India is a vast country with an area of 328.78 Mha with a coastline of 5690 km.

India supports a population of more than1 billion, and to support such a big population agriculture plays a very essential role .


In irrigation and other water supplies ground water plays a very important role, nearly 48% of the irrigation is provided by ground water and 52% by surface water.

In recent years the ground water levels have dropped 5-15 m in many areas of India as a result of over exploitation of fresh water.

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Degree of saline water presence in various parts of India

•This is a Map generated by Central Ground Water Board underMinistry of Water Resource Government of India.

•It show’s the various regions in India effected by saline ground water.

•From this map it is evident that saline content in ground water is the highest in Gujarat and Rajasthan.


Case Study Area

Gujarat:Northern Gujarat and the coastal areas

•The population of the Gujarat State was 50.67 million as per the 2001 census data

•The coastal population is 9.4 million

•Population of Kutch district is 1.5 million


•Having a diverse geological and climatic condition, most part of Gujarat comes under scarcity prone area. The uneven distribution of rainfall from 2000 to 200mm annually and the complex geographical formation across the state make storage water and reallocation of recharged ground water difficult.

•Gujarat also has a very long coast line and Gujarat has long coastline of 1125 kms Km and two huge gulfs- The Gulf of Cambay and The Gulf of Kutch, besides these the entire Little Rann of Kutch and Greater Rann of Kutch are inundated with saline sea water for most part of the year which deteriorates the ground water quality in the adjoining areas.

Gujarat: A Water Scarce State

*From Policy to Practice Users as Managers of Rural Drinking Water Supply System Water and Sanitation Management Organization(WASMO) 6Environment and Sustainability

Gujarat has about 5.96% of India’s geographic area and about 5 % of the population, but it has only 2.63% of the countries fresh water content. The coastal zone population has increased from 7.5 million to 9.4 million, i.e. an increase of 24.74%. This has adversely hit the availability of fresh surface water and has increased the saline water content


Surveys were undertaken in coastal belt of Saurashtra to determine the cause and effect relationship of salinity through pumping of groundwater in the coastal regions The study revealed that the limited outflows to the sea and the use and reuse of the limited groundwater available in the coastal aquifer and extensive use of chemical fertilisers has lead to mineralisation leading to increase in salinity of groundwater. Moreover, the salt-water intrusion has reached 25 km inland.

•The Industrial growth in this state has also been very rapid due to which excess use of ground water besides agriculture has resulted in the subsequent depletion of the quality and amount of fresh water that was available.


Water and Sanitation Management Organization had conducted a survey of 7675 villages and a certain data was extracted form it

•35% of the 7675 villages are affected by salinity

•55% of the villages are affected by Fluoride

•2% of the villages affected by both Salinity and Fluoride

• i.e. 88% of villages that have either Salinity or a Fluoride problem.

For salinity, the main affected areas are the coastal areas and some inland areas in northern Gujarat.

For Fluoride the severely affected zones are in northern Gujarat and in southernSaurashtra.

An overview of the current situation in Northern Gujarat


Salinity levels in various areas

*Groundwater and well-water quality in Alluvial aquifer of Central GujaratSunderrajan Krishnan, Sanjiv Kumar, Doeke Kampma and Suresh Nagar International Water Management Institute(IWMI)


•The total area of the district is 8,846 sq km.

• As per 2001 census, the population of Junagadh district is 24, 48,173

•Agriculture is the backbone of the district economy. Even Fish processing industry is a major sector in Junagadh.

•Average Rainfall recorded in this place is 787 mm.

Study Area Junagadh District

*Ingress of saline water in Coastal aquifers of Junagadh, Gujarat by T. Raychoudhury & S. KrishnanInternational Water Management Institute-Tata, Anand-388120, Gujarat, India 11Environment and Sustainability

Talukas Salinity Ingress Distance

Una 9.6

Kodiral 9.5

Veraval 7.5

Mangrol 8.25

Salinity Ingress Distance in Different Talukas of Junagadh area

.

Main causes of increase in salinity may be due to inherent salinity, tidal effect, irrigation by saltwater and by seawater intrusion due to extensive pumping.

Around 90 wells were considered for monitoring and water sampling. Water sample having TDS within 1750ppm to 2000 ppm is considered as saline water depending on Indian standards (2000 ppm) as of today. With this specification salinity ingress distance and profile has been found out and the result is given below

*Ingress of saline water in Coastal aquifers of Junagadh, Gujarat by T. Ray Choudhury & S. KrishnanInternational Water Management Institute-Tata, Anand-388120, Gujarat, India

Junagadh, a coastal area


From the observation of the data collected it is noticed that the salinity ingress incoastal Junagadh area are extended from past three decades in different rate. In 2008 pre-monsoon period this ingress distance is found in a range of 7.5 km to 9.6 km on an average

Comparison of intervened and non intervened sites show that Government interventions are also not bringing much change in salinity ingress scenario in macro scale but there are few changes in the micro scale

Conclusions

“Ingress of saline water in Coastal aquifers of Junagadh, Gujarat by T. Ray Choudhury & S. Krishnan” 13Environment and Sustainability

•Kutch is the Largest District in India with a total area of 45652 sq km. But it is very sparsely populated

•As per 2001 census, total population was estimated as 15,83,225

•Out of this, the Rann of Kutch or salt desert occupies nearly nearly 2/3rd of the area.

Study Area Kutch District

*Salinity Mapping In Coastal Area Using GIS and Remote SensingThesis submitted to the International Institute for Geo-information Science and Earth Observation

•Average Rainfall recorded in this place is 587mm


Problem of salinity ingress is also being faced along Saurashtra and Kachchhcoast for coastline Due to various agricultural practices sea water ingress even up to 8 to 9 Km in ground has occurred effecting approximately 10.8 lack people

The factors responsible

•Irregular and low precipitation•Highly porous geological formations•Low natural charge•Poor land management•Excessive withdrawal of water for irrigation



Conclusion

•The soil in this area contains high amount of saline content in the soil itself and there has also been a lot of cases of sea water ingress from the past many years. The people in this area are used to drinking salty water but this eventually damages there overall health.

•Due to the high amount of saline there are not many farming activities in this area, there are some cattle and sheep who graze off some grass growing in random places

•But due the high saline presence there are also numerous salt pans in this area from which salt crystals are obtained after letting the water evaporate under the sun


District Level

Taluka Level

Panchayat Level

Domestic Level

Water supply at different levels

Construction of desalination plants

Construction of deep tube wells

Village wells/supply by government water tankers

Water pipeline or collection of water from wells


Due to excessive pumping of ground water in the costal regions the natural hydraulic gradient and aquifer have become saline. Increase in salinity beyond a certain tolerance limit leads to high saline of groundwater, thus making it unusable.

Water Ingress



Effects of high level of Salinity in the water consumed

*Groundwater contamination and rural water treatment in Gujarat Safe drinking water for the last person?Rajnarayan Indu* and Sunderrajan Krishnan for International Water Management Institute

Consumption of Saline

water

Due to high consumption of salt

skeletal flourosis also occurs which results in

weak bones thus people have a difficult time

standing up and walking.

Continuous consumption of saline water results in

kidney stones, blood pressure and several skin

diseases.

The daily consumption of saline water results in undesirable taste, gastro

intestinal irritations, corrosion or incrustation

Dental Flourosis is also a common occurring

among people with high saline consumption..


Social Problems for not adopting community based water purification methods

•Not all households would be willing to shell out equally for a commonly owned treatment system, especially since the most common techniques of treatment such as Reverse Osmosis (RO) is quite costly, as compared to the saving levels of rural poor.

•Variation in the source and quality of water around the year, makes it compulsory for multiple treatments of water

•Varity of other social problems i) taking into account that many farmers drink water from bore-wells in the fields, ii) single common source of drinking water for several villages.iii) catering to old, disabled and remotely located inhabitants

*Groundwater contamination and rural water treatment in Gujarat Safe drinking water for the last person?Rajnarayan Indu* and Sunderrajan Krishnan for International Water Management Institute


Region Biased problems due to lack of fresh water

•.

*Gender Roles and Multiple Uses of Water in North Gujarat by Bhawana Upadhyay for International Water Management Institute

Most households suffer severe shortages of fresh water, due the soil itself being saline

In some districts, women walk more than 10-12 km to fetch fresh water for domestic purpose.

Supply of domestic water by a government tanker to a number of villages is not regular and sometimes in a weekly biases.

Gujarat dose not have many perennial sources of water and it is predominantly a rain-fed agriculture.

Due to lack of fresh water, washing clothes is not a daily activity due to which skin problems and rashes develop mostly in women.

Due to different geographic factors door to door connection of pipe line is not possible in many of the villages.


•Reverse Osmosis (RO)

•Thermal Desalination•Mechanical Vapor Compression •Multi Effect Evaporation•Multi Stage Flash Distillation

•Solar Water Disinfection Technique (SWDT)

•Water Harvesting

•Waste Water Treatment

Methods adopted by other areas having similar problem

Current techniques adopted for water distillation

Chemical and Mechanical Process for Distillation of Saline Water


Current Practices in studied areas for water filtration

•Water supply from the Narmada Pipeline: supplied mostly to townships, and some villages, but it is still unreachable to the villages in the coasts.

•Reverse Osmosis: is being practiced only in small townships and it is not possible at the village level due to the high initial cost and running costs.

•Solar Distillation: this process is being carried out in few places but they are not been practiced regularly and effectively due its lack of efficiency. But research on this is still being carried out by Gujarat Energy Development Agency


•Portable or drinkable water should have saline content of less than 550 parts per million (ppm) of total dissolved solid (TDS)

•The average demand for fresh water per person per day should be around 50-100 liters, for different uses such as bathing, washing and drinking and other purposes. But in areas of limited fresh water this drops down to 5- 6 liters per day per member depending upon the water supply and area they stay in

•The saline content in underground water in places near to the coast is near to 2000-2500ppm of TDS, and for sea water its between 30,000 to 50,000 ppm of TDS.

The permissible amount of saline content for agricultural use and other purposes is between 1500-2000ppm of TDS.

*Salinity is represented by TDS concentration in parts per million (ppm)ppm is parts per million, it is the amount of solvent in the water

TDS is total dissolved solvent

Permissible amount of contents in water


Water distillation though boiling/condensation of vapors

•Boiling is used as a method of water purification.

•Boiling is commonly advocated as an emergency water treatment method, or as a method of portable water purification in rural settings without access to a potable drinking water

•Water purification, such as distillation, is especially important in regions where water resources or tap water is not suitable for ingesting without boiling or chemical treatment.

•By the process of distillation though boiling or condensation most of the impurities are distilled out and drinkable water can the acquired after the process

Solar water distillation

In solar distillation water is evaporated;

using the energy of the sun then the vapor condenses as pure water. This process removes salts and other impurities.

• Basin • Black Liner • Transparent Cover • System

• Condensate Channel • Sealant • Insulation • Supply and Delivery

Black Liner Insulation Basin

Transparent Cover

Sealant

Condensate Channel

Components of a Solar Still


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 correspondinglyhigher.

Types of Solar Stills

*Understanding Solar Stills by Horace McCracken &Joel GordesVirginia Institute of Technology 28Environment and Sustainability

Wick stills - In a wick still, the feed water flows slowly through a porous, radiation-absorbing pad (the wick). Two advantages are claimed over basin stills. First, the wick can be tilted so that the feed water presents a better angle to the sun (reducing reflection and presenting a large effective area). Second, less feed water is in the still at any time and so the water is heated more quickly and to a higher temperature. Simple wick stills are more efficient than basin stills and some designs are claimed to cost less than a basin still of the same output.

*Understanding Solar Stills by Horace McCracken &Joel GordesVirginia Institute of Technology

the need to frequently clean the cloth wick of built-up sediments

the need to replace the black wick material on a regular basis due to sun bleaching and physical deterioration by ultra-violet radiation


Emergency still - To provide emergency drinking water on land, a very simple still can be made. It makes use of the moisture in the earth. All that is required is a plastic cover, a bowl or bucket, and a pebble.

*Understanding Solar Stills by Horace McCracken &Joel GordesVirginia Institute of Technology 30Environment and Sustainability

Solar Stills in the market

Solar Stills Developed by Gujarat Energy Development Agency

Solar Still using Parabolic Mirror to concentrate the sunlight into the water trough

Solar Still Developed by Maharashtra Energy Development Agency


Solar distillator with two slat glazing surfaces

Solar distilator with curved surface

Aquadome: this is a type of water distillator used mostly for personal use.

Watercone a product developed for the Dry African Nations 32Environment and Sustainability

MATERIALS FOR SOLAR STILLS

• Transparent Covering: Should have high transmittance for solar radiation, opaque to thermal radiation, resistance to abrasion, long life, low cost, lightweight, easy to handle and apply, and universal availability.

• Black Linear: Should absorb more solar radiation, should be durable, should be water tight, easily cleanable, low cost, and should be able to withstand temperature around 100 Deg C.

• Sealant : Should remain resilient at very low temperatures, low cost, durable and easily applicable..

• Basin Tray: Should have long life, high resistance to corrosion and low cost.

• Condensate Channel: Should not again contaminate the distilled water


BASIC REQUIREMENTS OF A GOOD SOLAR STILL

• Be easily assembled in the field

• Be constructed with locally available materials

• Be light weight for ease of handling and transportation

• Have an effective life of 10 to 20 Yrs.

• No requirement of any external power sources

• Can also serve as a rainfall catchment surface

• Materials used should not contaminate the distillate

• Meet standard civil and structural engineering standards

• Should be low in cost.


Parameters of Solar Still’s output

1. Climatic ParametersI. Solar Radiation II. Ambient TemperatureIII. Wind SpeedIV. Outside HumidityV. Sky Conditions

2. Design ParametersI. Single slope or double slopeII. Glazing materialIII. Water depth in BasinIV. Bottom insulationV. Orientation of stillVI. Inclination of glazingVII. Spacing between water and glazingVIII. Type of solar still


Conclusion•Even though the current efficiency of a multi stage solar still is 35% and a single stage is around 30%, a solar still will be the ideal equipment for production of drinking water in areas where saline content is high. A solar still can also be helpful to distill out most of the general known contaminants.

•The major problem in the current design is the rate of production

•There is sometimes algae growth in the stills due to constant presence of water, and cleaning is also a problem.

•The use of solar desalination system in highly saline areas would help in extracting the salt crystals dissolved in the water.

•An average farmer might also use a portable distillation device to carry it to his fields and distill the irrigation water itself to produce drinking water in place where there is shortage of fresh water

•A community based water distillation/desalination device could be made which could supply drinking water to the families if its efficiency could be improved.


Solar Water Distillatory for community level

By Sahaj Ghose


Abstract

There are many methods and processes of solar distillation and many solar distillation devices are available in the market, but these devices are very bulky, expensive or not very efficient.

According to the research made there is a need of a solar distillatory which can be made affordable and which would provide drinking water at domestic level or at a community level. Portability of the device is also important.

Secondary Research

The basic working of a solar still is based on evaporation and condensation thus a little bit of research as on these.

Evaporation : Evaporation is a type of phase transition; it is the process by which molecules of water in a liquid state spontaneously become gaseous due to heating.

Condensation: is the change in the phase of matter from the gaseous phase into liquid droplets. Or in our case from water vapor to liquid form of water.


• the increase in temperature increases the rate of evaporation.Temperature

• : Increase in the surface over which the liquid is spread increases the rate of evaporation.

Surface area

• the increase in the amount of humidity in the air reduces the rate of evaporation.

Presence of humidity

Factors affecting the evaporation of water


•I had decided to design a efficient solar water distillator at a community level, that is for a family of 5.

As each families requires around 20 liters (for drinking and cooking) had decided to construct a disstilator which would provide for it.

•A number of 5 families was chosen as this would increase the mutual understanding among the families as to how much of water would be taken by each of the families.

•This would also help the individuals families keep a check on the maintenance of there own evaporation trays .

•Having a small number would also reduce the time women had to wait in line to collect water.

Social Considerations for Design


Concepts For a Solar Water Distillator

Reflecting Surface

Condensation Tank

Basins

There are two basins present which are attached to a condensation tank in the center. There are two reflecting mirrors which help to concentrate the sunlight to the to basins.


Basins for water evaporationStorage Tank

Reflecting Surface

The Solar water distillatory here uses three basins for the evaporation of water. There are three individual water storage tanks that supply water to the three solar stills. There is a single reflecting surface which concentrates the solar rays to the Basin.


Storage Trough

Transparent Surface

Corrugated surface to increase the surface areas of water

Collection Trough

In this design there is a single transparent surface but it is curved. There is one storage trough where all the saline water is given as input and a collecting trough where the saline water is collected. The corrugated surface helps in evaporation of water. 44Environment and Sustainability

Evaporation Plate

Transparent cover

Collection tank

This is a tree design for a solar distillatory where the evaporation plates are at a higher position, over here again the curved glazing surface is used.


Evaporating Basins

Preheating Tank

Condensation TankMoving away from the curved glazing surface I had come back to the flat surfaced evaporating trays and increased the number of trays that would be used at one go. This design also contains a pre heating tank and a condensation tank.


The Final ConceptEvaporation Tray

Preheating Tank

Condensation TankIn my final concept I have put in 5 trays from where condensation would occur, a preheating tank and a condensation tank. The trays in this design can be taken out to be cleaned 47Environment and Sustainability

Rendered image of the concept

The salty water is first stored in the preheating tank or storage tank where its temperature increases due to its exposure to the sun. this pre heating process makes the evaporation from the trays faster

The pre heated water is then transferred to the through the pipes to the to the tray

The flow of water to the tank is stopped by the valves present. The water is heated here until it evaporates and the vapors are trapped by the glass panel covering the tray.

The Condensation tank is at a lower temperature than the evaporating trays, due to this difference in temperature the water vapors flow into this chamber get condensed. An outlet from the bottom enables the water to be extracted

Working of the Solar Water Distillatory

1

2

3

4

The salty water is first stored in the preheating tank or storage tank where its temperature increases due to its exposure to the sun. this pre heating process makes the evaporation from the trays faster

The pre heated water is then transferred to the through the pipes to the to the tray

The flow of water to the tank is stopped by the valves present. The water is heated here until it evaporates and the vapors are trapped by the glass panel covering the tray.

The Condensation tank is at a lower temperature than the evaporating trays, due to this difference in temperature the water vapors flow into this chamber get condensed. An outlet from the bottom enables the water to be extracted

Wo

rkin

g o

f th

e So

lar

Wat

er D

isti

llato

ry

The

Sto

rage

an

d p

reh

eat

ing

tan

k : is where the saline water is initially fed. Along with the storage of the water the tank also acts as a preheating chamber where the stored water gets heated before it is sent to the basin.

The

Bas

in : after the water has been sent down from the over head pre heating tank the water enters the basin where the actual operation of evaporation occurs. the basin contains several trays of 20 liter capacity each and a glazing surface which traps the vapors.

The

Co

nd

en

sati

on

Tan

k : after the evaporation has taken place in the basin the vapor then gets transferred to the condensation tank, which is at a slightly lower temperature than the basin.

The Main Parts of the Solar Distillator


The evaporation tray present in the basin contains a valve which prevents the water from over flowing and also maintains a constant flow of water into the tray.

The valve works on the principle of buoyancy. When the water fills up the tray the hollow plastic starts to float and the rubber stopper present at the top stops the flow of water.

The Preheating Tank

•The Pre Heating Tank will have a capacity of 100 liters.

•The pre heating tank can be made form Aluminum (6061) as it has good thermal conductive property and has a good specific heat capacity , due to which the heat can easily be transferred from the surface of the metal to the water stored inside and due to low value of specific heat capacity it can get heated easily.

•To increase the rate of absorption the tank can be coated or covered with a black material.

Specific Heat CapacityThe specific heat capacity of a solid or liquid is defined as the heat required to raise unit mass of substance by one degree of temperature.

Thermal Conductivity:It is the property of a material that indicates its ability to conduct heat.


The Basin•The basin contains five trays having a capacity of 13.5 liters each. The whole production capacity of the solar still is 67 liters per day.

•The base area of the basin has an area of 33.63 square feet which can produce 67 liters of water per day.

•The material for the basin could be aluminum coated with silicon rubber or aluminum sheet of 1 mm width. Aluminum coated with silicon is suggested as the silicon coating would reduce the time of corrosion.

•The aluminum sheets could be coated with Teflon or colored black, for better absorption of heat.


•Even though the plastics are cheaper than either window glass or tempered glass, they are not preferred as they deteriorate under high temperatures and have poor wetability.

• Moreover, under temperature conditions typical of solar stills, the chemicals in plastics are likely to interact with the distilled water, possibly posing a health hazard

•The glass that is preferably used is tempered glass as it is stronger than window glass it has better transmittance and is not affected by high temperature.

•The preferred width of the glazing surface that is to be installed is 35 to 40 millimeter

Glazing Surface

Black polyethylene is preferred for tubing as it does not break up easily and is not affected by temperatures above 70 degrees centigrade.

PVC pipes might also be used but in the first few days of operation a small amount of gas is emitted which affects in the taste of the water.


Tubing

The Condensation Tank•After water has been evaporated and converted into vapor state, the vapor gets transferred into the condensation tank which is kept at a relatively lower temperature than the basin.

•The condensation tank is directly connected to the basin so there is not much energy loss in the transfer of the vapors.

•Due to the presence of the condensation tank, the water droplets are not formed on the glazing surface, due to which the efficiency of the still is not affected.

•Sometimes in the regular stills due to the condensation occurring on the glazing surface the water droplets sometimes fall back in the saline water itself, which is avoided in this case.


Insulation

The lower part of the trays are required to be insulated so as to minimize heat loss. The preferred insulation material used is sand as it is easily available and

helps in minimizing the heat loss. It also acts a heat sink which would return the heat to the tray.

Sealants

Sealants are also required to prevent the vapors from escaping and also to prevent any foreign contaminants from entering the distill water. Thus the sealants must be put in the connecting pipes, the point where the glazing surface is attached to the basin and the entry point of the vapor to the condensation chamber.

The suggested material for sealant is *Tar plastic.

*Tar plastic is waste plastics such as polyethylene and polystyrene which are converted into flakes and mixed with heated tar. 57Environment and Sustainability

Engineering Drawing

Engineering Drawing of the Tray

Engineering Drawing


The Solar Still should be installed in the East-West direction

Clean the Inner surface with chlorinated water

Allowing the condensation to take place for two days *

Collection of water from the condensation tank

Before First Use

* The production capacity of the still is 67 liters per day and the amount of water allowed per family is 20 liters thus after two day of condensation the water present in the condensation tank will be 134 liters, thus maintaining an excess of attest 30 liters 61Environment and Sustainability

Running of the Still

Filling the preheating tank

at dawn

Water gets filled into the trays

Evaporation starts in the still

Water starts heating up in the preheating tank

as well

Water condenses in the

condensation tank and is collected in

the evening


The solar still should be installed in a east-west direction so that it is able to receive the maximum sunlight and it should also be

placed on open ground. There could be a separate

storage tank where the water can be transferred from the

condensation tank, or water can be directly collected from the

condensation chamber

The filling of the preheating tank is a batch process. That is water should be filled in everyday at dawn. Or it should be refilled

after the still has cooled down as 5 to 7 percent of the distillation

occurs even after sundown.

The Glazing surface has got a tendency to get dirty easily, and get covered with dust. Thus

decreasing the efficiency of the solar still, so it is advisable that ate surface of the glazing

material be cleaned on a daily biases.

The trays should be taken out and cleaned once in every 2to 3 months. All the trays are

not needed to be taken out at the same time. Single tray can be taken out at a time for

cleaning off the residue left after the evaporation.

Maintenance of the Solar Still


Various other application of the solar powered solar water distillator

Besides being used in areas where there is sever shortage of water the solar distillatorcan also be used in places where there is a small industrial establishment and fresh water is not always available for example

•The offshore oil wells,

•Observation points in remote places,

•Remote construction sites


Documents

Final Systems Presentation Sahaj