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International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 5, May (2014), pp. 125-140 © IAEME 125 FABRICATION AND ANALYSIS OF PORTABLE DESALINATION SYSTEM Ananthan D Thampi 1 , Ajith C Menon 2 , Cedric Benedict 3 , Amal Sreenivas 4 1,3,4 Eighth Semester B.Tech Students, 2 Assistant Professor, Department of Mechanical Engineering, Marian Engineering College, Menamkulam, Kazhakuttom, Thiruvananthapuram Pin No: 695582 ABSTRACT Water is nature’s gift and it plays a key role in the development of an economy and in turn for the welfare of the nation. Scarcity of drinking water is one of the major problems faced all over the world. Today, majority of the health issues are due to the scarcity of clean drinking water. In recent decades, insufficient rainfall resulted in an increase in the water salinity. The water pollution is increasing drastically due to a factors like population growth, industrialization, urbanization, etc. Desalination is the oldest technology used by people for water purification. Various new technologies were invented for desalination from time to time and it has been accepted by people without knowing future environmental consequences. Major desalination techniques like distillation, reverse osmosis and electrolysis used electricity as input energy. Now input is provided with the help of solar energy so there will be no pollution and it’s free of cost. As the water inside the solar still evaporates, it leaves all contaminants and microbes in the basin. The purified water vapour condenses on the inner side of the glass, runs through the lower side of the still and then gets collected in a closed container. Many solar distillation systems were developed over the years using the above principle for water purification in many parts of the world. This is similar to rainwater formation. So we decided to do a work based on solar still. We have fabricated a double slope solar still along with a water heater which is controlled by a thermostat and a setup to measure power by using wattmeter. Vacuum pressure gauge and Thermometer is used to measure pressure and temperature inside the collecting tank respectively, a vacuum pump is also used to reduce pressure inside the still. Keywords: Solar Still, Desalination, Distillation. INTERNATIONAL JOURNAL OF ADVANCED RESEARCH IN ENGINEERING AND TECHNOLOGY (IJARET) ISSN 0976 - 6480 (Print) ISSN 0976 - 6499 (Online) Volume 5, Issue 5, May (2014), pp. 125-140 © IAEME: www.iaeme.com/ijaret.asp Journal Impact Factor (2014): 7.8273 (Calculated by GISI) www.jifactor.com IJARET © I A E M E
Transcript
Page 1: 20120140505015

International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –

6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 5, May (2014), pp. 125-140 © IAEME

125

FABRICATION AND ANALYSIS OF PORTABLE DESALINATION SYSTEM

Ananthan D Thampi1, Ajith C Menon

2, Cedric Benedict

3, Amal Sreenivas

4

1,3,4

Eighth Semester B.Tech Students, 2Assistant Professor,

Department of Mechanical Engineering, Marian Engineering College,

Menamkulam, Kazhakuttom, Thiruvananthapuram Pin No: 695582

ABSTRACT

Water is nature’s gift and it plays a key role in the development of an economy and in turn

for the welfare of the nation. Scarcity of drinking water is one of the major problems faced all over

the world. Today, majority of the health issues are due to the scarcity of clean drinking water. In

recent decades, insufficient rainfall resulted in an increase in the water salinity. The water pollution

is increasing drastically due to a factors like population growth, industrialization, urbanization, etc.

Desalination is the oldest technology used by people for water purification. Various new

technologies were invented for desalination from time to time and it has been accepted by people

without knowing future environmental consequences. Major desalination techniques like distillation,

reverse osmosis and electrolysis used electricity as input energy. Now input is provided with the help

of solar energy so there will be no pollution and it’s free of cost. As the water inside the solar still

evaporates, it leaves all contaminants and microbes in the basin. The purified water vapour

condenses on the inner side of the glass, runs through the lower side of the still and then gets

collected in a closed container. Many solar distillation systems were developed over the years using

the above principle for water purification in many parts of the world. This is similar to rainwater

formation. So we decided to do a work based on solar still. We have fabricated a double slope solar

still along with a water heater which is controlled by a thermostat and a setup to measure power by

using wattmeter. Vacuum pressure gauge and Thermometer is used to measure pressure and

temperature inside the collecting tank respectively, a vacuum pump is also used to reduce pressure

inside the still.

Keywords: Solar Still, Desalination, Distillation.

INTERNATIONAL JOURNAL OF ADVANCED RESEARCH

IN ENGINEERING AND TECHNOLOGY (IJARET)

ISSN 0976 - 6480 (Print) ISSN 0976 - 6499 (Online) Volume 5, Issue 5, May (2014), pp. 125-140 © IAEME: www.iaeme.com/ijaret.asp Journal Impact Factor (2014): 7.8273 (Calculated by GISI) www.jifactor.com

IJARET

© I A E M E

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126

1. INTRODUCTION

The shortage of drinking water is expected to be the biggest problem of the world in this

century due to unsustainable consumption rates and population growth. Pollution of fresh water

resources (rivers, lakes and underground water) by industrial wastes has increased the problem. The

total amount of global water reserves is about 1.4 billion cubic kilometers. Oceans constitute about

97.5% of the total amount, and the remaining 2.5% fresh water is present in the atmosphere, surface

water, polar ice and ground water. This means that only about 0.014% is directly available to human

beings and other organisms. Therefore, the development of new clean water sources is imperative.

Desalination of sea and/or brackish water is an important alternative, since the only inexhaustible

source of water is the ocean. Solar desalination is suitable for remote, arid and semi- arid areas,

where drinking water shortage is a major problem and solar radiation is high. These places mostly

suffer also from energy shortage. The limitations of solar energy utilization for desalination are the

high initial cost for renewable energy devices and intermittent nature of the solar radiation. Due to

these limitations the present capacity of solar desalination systems worldwide is only about 0.01% of

the existing large-scale conventional desalination plants. Therefore, efforts must be made to develope

technologies, which will collect and use renewable energy more efficiently and cost effectively to

provide clean drinking water. Besides, developing new technologies to store this energy for using it

whenever it is not available is also required. Solar stills are commonly used in arid coastal zones to

provide low-cost fresh water from the sea. Total daily output of the solar still decreases with

increasing water depth, but overnight output increases with an increase in water depth, which

contributes considerably towards the total daily output. However, various scientists have made

attempts to maximize the daily yield per square metre/day in a single basin solar still in a passive

mode. From the previous work, it has been observed that the daily yield per square metre /day in the

basin solar still mainly depends on the evaporative area and condensing surfaces.

The energy required to evaporate water, called the latent heat of vaporisation of water, is

2260 kilojoules per kilogram (kJ/kg).This means that to produce 1 litre (i.e. 1kg as the density of

water is 1kg/litre) of pure water by distilling brackish water requires a heat input of 2260kJ. This

does not allow for the efficiency of the system sued which will be less than 100%, or for any

recovery of latent heat that is rejected when the water vapour is condensed. It should be noted that,

although 2260kJ/kg is required to evaporate water, to pump a kg of water through 20m head requires

only 0.2kJ/kg. Distillation is therefore normally considered only where there is no local source of

fresh water that can be easily pumped or lifted. The objective of the present work is to fabricate a

working model of solar still with few modifications and do experimental analysis on the solar still.

2. BASIC PRINCIPLE OF SOLAR STILL

The basic principle behind solar distillation is simple and replicates the natural process of

water purification. A solar still is an air tight basin that contains saline or contaminated water (i.e.

feed water).It is enclosed by a transparent top cover, usually of glass or plastic, which allows

incident solar radiation to pass through. The inner surface of the basin is usually blackened to

increase the efficiency of the system by absorbing more of the incident solar radiation. The feed

water heats up, then starts to evaporate and subsequently condenses on the inside of the top cover,

which is at a lower temperature as it is in contact with the ambient air. The condensed water (i.e. the

distillate) trickles down the cover and is collected in an interior trough and then stored in a separate

basin. This system is also known as passive solar still, as it operates solely on sun’s radiation

From a radiative point of view the following happens inside the distiller unit: the part of the

solar radiation that is not reflected nor absorbed by the cover is transmitted inside the solar still,

where it is further reflected and absorbed by the water mass. The amount of solar radiation that is

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absorbed is a function of the absorptivity and depth of the water. The remaining energy eventually

reaches the blackened basin liner, where it is mostly absorbed and converted into thermal energy.

Some of this energy might be lost due to poor insulation of the sides and bottom. At this stage, the

water heats up, resulting in an increase of the temperature difference between the cover and the water

itself. Heat transfer takes then place as radiation, convection and evaporation from the water surface

to the inner part of the cover. The evaporated water condenses and releases latent heat. This last one

is then lost through convection and radiation together with the remaining convective and radiative

heat.

Little research has been done regarding the water quality of the water produced by solar-

stills based on polluted or muddy water. However it is proven that nitrates, chlorides, iron, heavy

metals and dissolved solids are completely removed by the solar still. The process also proved to be

effective in the destruction of microbiological organisms present in the feed water. The distillate is

thus high purity water, which also lacks essential dissolved minerals. Drinking de-mineralised water

can have serious health consequences, and it is thus of crucial importance that the essential minerals

are added to the water before consumption. The advised quantities of minerals where minimum or no

adverse health effects are observed to be measured in the field. Once the working of the system has

proven to be effective, it is important that the water users are well informed about the solar still in

order to ensure its correct functioning and its sustainability. It is essential to emphasize that the solar

still will only produce the expected output when it is fully airtight. This means that the water inlet

should never be opened. The same holds for the drinking water tank which should also never be

opened.

3. LITERATURE REVIEW

Anirudh Biswas, Ruby in their paper discussed about clean water remains one of the most

challenging international issues of today and solar distillation offers important and effective

solutions. Low cost solar stills offers immediate and effective solutions in reliably providing safe

distill water year after year. Single-basin solar stills are easy to build, inexpensive and extremely

effective in distilling water with a high total dissolved salt content and in killing bacteria such as

cholera. Average water production of a single solar still is about 0.5 liters per square meter per sun

hour. Solar stills can bring immediate benefits to their users by alleviating chronic problems caused

by water-borne diseases. Solar stills offer the only realistic and cost-effective means to provide safe

distill water for use. [1]

M.KoilrajGnanadson, P.Senthilkumar, G.Sivaraman in their paper discussed about a single

basin solar still made up of copper sheet was fabricated and tested for both the conditions with and

without vacuum.The distilled water production rate of a single basin solar still can be varied with the

design of the solar still, absorbing materials, depth of water, salt concentration and location. The

efficiency is higher for a solar still made up of copper and it can be increased further by painting

black inside the still. The modified innovative still working under low pressure has enhanced

performance in compared with the still working at atmospheric pressure and more flexible with

climatic conditions. Average requirement of water per person in a house is assumed to be around

1.5litres/day. Therefore it gives the total water consumption to be around 7.5 liters/day. Their design

is expected to be cost effective and provide an efficient way to convert the brackish water into

potable water.[2]

K.Sampathkumar, T.V.Arjunan, P.Pitchandi, P.Senthilkumar in their paper discussed about

the use of solar energy in desalination process is one of the best applications of renewable energy.

The solar stills are friendly to nature and eco-system. Various types and developments in active solar

distillation systems, theoretical analysis and future scope for research were reviewed in detail.[3]

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A. E. Kabeel, based on the results obtained from their experimental work, the conclusions

from their results are the temperature of the four glass cover surface is not equally specially till

afternoon, the average distillate productivity of the proposed still during the 24 hours time is about

4l/m2, the proposed solar still efficiency is 0.38 at solar noon. In order to complete the whole picture

of their study, a future work was proposed by them like studying the system theoretical

performance,studying the system at different glass tilt angles, studying the system at different water

depth in the still basin.[4]

Kaabi Abdennacer, Trad Rachid in their paper they discussed about the use of solar energy

for water desalination becomes necessary due to lack of water. In this case, they propose in their

study a model of a solar still with a collector having two slopes (double exposure).The system

collects a maximum of solar radiation. In order to render the system well performed, they optimised

in their study some thermo physical parameters which have a direct effect on its performance. The

obtained results concluded that a wind velocity going up to 10 m/s, affects directly the production of

distilled water and beyond this value (10 m/s),this production becomes insignificant, the angle of the

inclination of the collector (β) seems to be justified, where an optimum angle of 10° will give a better

production of distilled water, an increase of the temperature difference (δt) between the collector and

the basin water will bring the production of distilled water at its maximum, the ideal depth of the

basin water is at its minimum value, where in their case a water depth of 0.02 m will give a better

production of distilled water, an absorber made of aluminium covered by a black and thick layer in

order to give a better absorption of the solar radiation, leads to a better production of distilled water,

an insulator made of polystyrene and reinforced by a metallic or a wooden support will limit heat

losses.[5]

Hazim Mohameed Qiblawey, Fawzi Banat in their paper they have presented an overview of

solar thermal desalination technologies, focusing on those technologies appropriate for use in remote

villages. Solar energy coupled to desalination offers a promising prospect for covering the

fundamental needs of power and water in remote regions, where connection to the public electric

grid is either not cost effective or not feasible and where the water scarcity is severe. Solar

desalination processes can be devised in two main types: direct and indirect collection systems. The

“direct method” use solar energy to produce distillate directly in the solar collector, whereas in

indirect collection systems, two sub-systems are employed (one for solar energy collection and the

other one for desalination).The direct solar energy method uses a variety of simple stills which are

appropriate for very small water demands; indirect methods use thermal or electrical energy and can

be classified as: distillation methods using solar collectors or membrane methods using solar

collectors and/or photovoltaics for power generation. Solar thermal desalination plants utilizing

indirect collection of solar energy can be classified into the following categories:

Atmospheric humidification/dehumidification, Multi-Stage Flash (MSF), Multi-Effect

Distillation (MED), Vapor Compression (VC) and Membrane Distillation (MD).[6]

Prof.Nilamkumar S Patel, Prof.Reepen R Shah, Mr.Nisarg M Patel, Prof.J.K.Shah,

Mr.Sharvil B Bhatt from their paper it was concluded that after reviewing all type of solar stills. By

considering it is found that stepwise basin solar still gives much better as compared to all solar still

discussed above because of its large absorbing area or basin area. The efficiency of stepwise solar

still is higher than concave and conventional solar still. So, ascending order of efficiency of solar still

is [conventional solar still <concave solar still <pyramid solar still].[7]

Bilal A Akash, Mousa S. Mohsen, Waleed Nayfeh for the cases considered in their paper, an

optimum cover tilt angle of 350 was determined for maximum water production in the solar still

during the month of may. The salinity of water affects distillate production even at low

concentration. It decreases with increasing salinity. However, when the concentration is high, a

smaller decrease in productivity with increasing salinity is noticed in their experiments. Water depth

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129

affects the amount of distillation. It decreases with increasing water depth in a somewhat linear

relationship.[8]

4. DESCRIPTION OF APPARATUS

For high efficiency the solar still should maintain a high feed water temperature, a large

temperature difference between feed water and condensing surface, low vapour leakage.

In this work, We have selected a double slope solar still instead of a single slope solar still, so

that the apparatus will be exposed to solar radiation for more time. The brackish water that is

provided into solar still basin can be heated, so we have provided a heating chamber inside which an

ordinary heater is placed and they can be controlled with help of a thermostat. When pressure inside

is reduced boiling point of water decreases, so we have also provided a vacuum pump to reduce

pressure. We have also provided measuring instruments to measure temperature, pressure, power.

4.1 Design of Solar Still

Fig 1: CAD drawing of proposed still, front view Fig 2: CAD drawing of proposed still, side view

Fig 3: 3D drawing of the proposed Fig 4: 3D drawing of the proposed

collecting tank with a heater double sloped Solar still

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Fig 5: 3D drawing of both the collecting tank with heater and double slope solar still

5. MANUFACTURING AND ASSEMBLY

5.1 Material Selection

• Basin Liner: This is a major part of the solar still. It absorbs the incident solar radiation that is

transmitted through the glass cover. The basin liner should be resistant to hot saline water or

brackish water, has high absorbance to solar radiation and resistance to accidental puncturing

and in case of damage, it should be easily repaired. Black paint can be used to increase the

absorptivity of solar still.

• Mild steel: It is least expensive of all steels and most common steel used. It is weldable, very

hard, durable and also it is malleable and ductile. It contains 0.29% carbon. Due to its poor

corrosion resistance. It must be painted or otherwise protected and sealed in order to prevent

rust from damaging it. The thermal conductivity of mild steel is 43 w/mk. The cost of mild

steel is 53Rs/kg. Mild steel is used in our work.

• Glass Cover: In our work, glass of 4 mm thickness was used and its average transmissivity of

0.89, it was fixed at angle of 15o. Glass cover has been sealed with silicon rubber, which is

most successful because, it will make strongly contact between the glass and many other

materials. The sealant is important for efficient operation.

• Insulating material: It is used to reduce the heat losses from the bottom and the side walls of the

solar still in this work. The insulating material is a rock wool of 5 cm thickness and 0.048

w/m20

c thermal conductivity and thermocol can also be used.

5.2 Steps of Manufacturing and Assembling

Fabrication of the whole unit is pretty straight forward and involves metal cutting, welding,

glass cutting, sealing, painting and drilling. All these processes can be done at any local workshops

using simple machines – lathe, drill, welding, milling etc. The steps in the process of manufacturing

and assembling are outlined as follows:

• Solar still basin will be fabricated first. It will be made of double wall and will be filled with

glass wool or thermocol to provide insulation and supports to place glass.

• The collector tubes are then made and attached to the still basin.

• The holes are provided for:

a. collecting distilled water

b. transporting saline water

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c. to attach the pump

d. to clean the basin.

• The whole system is sealed using sealant to prevent the air from leaking in from the

atmosphere.

• Pipes and valves for each holes are provided.

• The whole system is then painted to prevent rusting.

• Glass required is cut and placed on the support and using silica gel it is fixed to the system.

• Vacuum pump and heating chamber are connected to solar still using flexible pipes.

The cost of construction for a passive solar still is considerably cheaper than a more complex

humidification/condensation flow through system. All that is required is a large insulated box with

solar absorbing material in the basin, a transparent glazing. Because the box is not under any loading,

most insulating foam boards such as expanded polystyrene, extruded polystyrene and

polyisocyanurate board can provide structural rigidity and no other materials will be needed.

6. EXPERIMENTAL SETUP

The solar still, the simplest desalination technology, consists of a shallow basin with a

transparent cover. Water in the basin, heated by the sun, produces vapour which condenses on the

cover, releasing its heat to the atmosphere and runs off the cover into a collecting trough. The

temperature difference between the water and the atmosphere needed to produce distillation at a

usable rate is about 5° to 10° C. The amount of water desalinated by the solar still depends on the

amount of solar insolation, area of the still, ambient air temperature, feed water temperature,

presence of insulation around the sides and bottom of the still, presence of leaks in the still, slope of

the cover with respect to the incidence angle of incoming sunlight and the depth of water in the still.

A primary advantage of solar stills is that they can be constructed from cheap, locally available

materials, such as wood, concrete, metal, thermocol, glass. The cover must be transparent to sunlight

but trap heat; therefore, glass or plastic is used. a sealant such as silicone prevents leaks. A dark

material such as butyl rubber is usually used to line the basin. Sand or Sawdust can provide

insulation. Maintenance of the still involves checking for and repairing leaks, periodic flushing to

remove salt deposits and cleaning of debris and dust from the cover.

The solar desalination system consist of a collecting tank where the saline water is initially

collected and stored. Provision for heating the water is provided in a heating chamber. This chamber

is connected with the desalination tank using a hose. The water flow is adjusted by a ball valve and a

float valve for controlling the water level inside the desalination chamber. Water enters the

desalination chamber through a hose. The desalination chamber is a double sloped solar still

arrangement. The slopes are equipped with glass. So as to trap the sunlight, to provide a condensing

surface and to obtain greenhouse effect. The condensing water drops down through the slope and it is

channeled to the outlet valve. The oulet valve is provided with a ball valve for obtaining the

condensed desalined water. The requirement of a ball valve is to seal the chamber from atmospheric

interference. The desalination chamber is provided with a nozzle for creating vacuum. The vacuum is

created using a vacuum pump �

�HP pump, which can reduce the pressure. Finally a pipe is given for

flushing out the salt deposits. Measuring instruments are used to measure temperature, pressure,

power.

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Fig 6: Solar still during Experimental analysis Fig 7: Water getting condensed in the Solar still

7. RESULT AND DISCUSSION

The experiments on the still was conducted from 10.00 AM to 6.00 PM. Experiments were

conducted with a basic solar still without any modifications, basic solar still with heater, basic solar

still with heater under reduced pressure. The experiments were conducted on the month of february

and march. Initially results were obtained without proper insulation and after that with proper

insulation. The readings of Atmospheric temperature (TA), Temperature of Water

inlet(TIN),Temperature of Water inside( TWI) are measured in terms of 0C and Productivity was

measured in terms of ml. The results are tabulated below:

Table 1: variation on a Basic Solar Still without insulation

Graph 1: Productivity Vs Time plot for basic solar still without insulation

0

10

20

30

40

50

60

10

:00

11

:00

12

:00

PM

1:0

0 A

M

2:0

0 P

M

3:0

0 P

M

4:0

0 P

M

5:0

0 P

M

6:0

0 P

M

pro

du

ctiv

ity i

n m

l

time of the day

productivity

SL TIME

TA

��� ���

TIN

���

TWI PRODUCTIVITY

(ml)

1 10am 32 32 34.1 0

2 11am 32 35 39.5 5

3 12pm 34 36 43.4 10

4 1pm 34 38 48.7 15

5 2pm 34 40 50.5 25

6 3pm 34 41 52.8 50

7 4pm 34 42 52.4 20

8 5pm 32 39 50.4 15

9 6pm 32 37 46.1 10

TOTAL 150ml

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Graph 2: Temperature Vs Time plot for basic solar still without insulation

Table 2: variation on a basic Solar Still with Heater without insulation

Graph 3: Productivity Vs Time plot for basic solar still with heater without insulation

0

10

20

30

40

50

60

tem

per

atu

re i

n

⁰⁰ ⁰⁰C

time of the day

Atmospheric

temperature

temperature of

inlet water

temperature of

water inside

0

10

20

30

40

50

60

pro

du

ctiv

ity

in

ml

time of the day

productivity

SL TIME TA

���

TIN

��� ���

TWI PRODUCTIVITY

(ml)

1 10am 32 32 47.7 20

2 11am 32 34 50.2 40

3 12pm 34 36 54.2 40

4 1pm 34 38 52 42

5 2pm 34 40 53.5 45

6 3pm 34 41 54.4 55

7 4pm 34 43 52.7 38

8 5pm 32 40 51.6 25

9 6pm 32 38 50.6 15

TOTAL 320ml

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134

Graph 4: Temperature Vs Time plot of basic solar still with heater without insulation

Table 3: variation of a basic Solar Still with Insulation

Graph 5: Productivity Vs Time for basic solar still with insulation

0

10

20

30

40

50

60

tem

pe

ratu

re in

⁰ C

time of the day

Atmospheric

temperature

Temperature of

water inlet

temperature of

water inside

0

50

100

150

200

250

pro

du

ctiv

ity

in

ml

time of the day

Productivity

SL TIME TA

��� ���

TIN

���

TWI PRODUCTIVITY

(ml)

1 10am 32 32 34.1 30

2 11am 32 35 39.5 50

3 12pm 34 36 43.4 80

4 1pm 34 38 48.7 120

5 2pm 34 40 50.5 150

6 3pm 34 41 52.8 200

7 4pm 34 42 52.4 170

8 5pm 32 39 50.4 90

9 6pm 32 37 46.1 60

TOTAL 950ml

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135

Graph 6: Temperature Vs Time plot for basic solar still with insulation

Table 4: variation on a basic Solar Still with Heater and Insulation

Graph 7 : Productivity Vs Time for basic solar still with heater and insulation

0

10

20

30

40

50

60

10

:00

AM

11

:00

AM

12

:00

PM

1:0

0 A

M

2:0

0 P

M

3:0

0 P

M

4:0

0 P

M

5:0

0 P

M

6:0

0 P

M

tem

per

atu

re i

n

⁰⁰ ⁰⁰C

time of the day

Atmospheric

temperature

Temperature of

water inlet

Temperature of

water inside

0

50

100

150

200

250

300

pro

du

ctiv

ity

in

ml

time of the day

Productivity

SL TIME

���

TA TIN

��� ���

TWI PRODUCTIVITY

(ml)

1 10am 32 32 52 55

2 11am 32 34 53 80

3 12pm 34 37 55 120

4 1pm 34 38 56 160

5 2pm 34 41 58 210

6 3pm 34 42 61 240

7 4pm 34 44 57 200

8 5pm 32 39 54 150

9 6pm 32 37 50 85

TOTAL 1300ml

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Graph 8: Temperature Vs Time plot of basic solar still with heater and insulation

Table 5: variation on a basic Solar Still with Vacuum pump, Heater and Insulation

Graph 9: Productivity Vs Time for basic solar still with vacuum pump, heater with insulation

0

20

40

60

80

tem

pe

ratu

re in

oC

time of the day

Atmospheric

temperature

Temperature of

water inlet

Temperature of

water inside

050

100150200250300

10

:00

AM

11

:00

AM

12

:00

PM

1:0

0 A

M

2:0

0 P

M

3:0

0 P

M

4:0

0 P

M

5:0

0 P

M

6:0

0 P

M

pro

du

ctiv

ity

in

ml

time of the day

Productivity

SL TIME

���

TA

���

TIN TWI

���

PRODUCTIVITY

(ml)

1 10am 32 32 53 55

2 11am 32 35 54 80

3 12pm 34 37 54 120

4 1pm 34 39 56 180

5 2pm 34 41 59 220

6 3pm 34 42 60 260

7 4pm 34 43 58 210

8 5pm 32 39 55 155

9 6pm 32 36 51 90

TOTAL 1370ml

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137

Graph 10: Temperature Vs Time plot for basic solar still with vacuum pump, heater with insulation

Graph 11: Productivity Vs Time plot at different setup

Graph 12: Temperature Vs Time plot of water temperatures with different setup

8. INFERENCE

From the readings we obtained in the basic still and basic solar still with heater, initially was

not up to the expected. So we gave additional insulation, thus the conduction losses where reduced.

The productivity was very low but after providing insulation the productivity was raised to about

900ml. The readings from basic solar still with heater and added insulation shows an increment in

010203040506070

tem

per

atu

re i

n

⁰⁰ ⁰⁰C

time of the day

Atmospheric

temperature

Temperature of

water inlet

Temperature of

wter inside

0

50

100

150

200

250

300

pro

du

ctiv

ity

in

ml

time of the day

basic with

insulation

with heater and

insulation

with vacuum

pump heater

and insulation

0

10

20

30

40

50

60

70

10

:00

AM

11

:00

AM

12

:00

PM

1:0

0 A

M

2:0

0 P

M

3:0

0 P

M

4:0

0 P

M

5:0

0 P

M

6:0

0 P

M

tem

per

atu

re i

n

⁰⁰ ⁰⁰C

time of the day

basic with

insulation

with heater

and

insulation

with vacuum

pump and

heater and

insulation

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138

productivity with respect to the basic and by incorporating vacuum pump there is only a very small

increment in productivity. These readings may have varied due to

• Conduction losses

• Insufficient solar radiation

• Any small leak in the system

• Place where experiment was conducted.

9. COST EFFECTIVE ANALYSIS

The cost of pure water produced depends on:

• The cost of making the still

• The cost of the land

• The life of the still

• Operating costs

• Cost of the feed water

• The discount rate adopted

• The amount of water produced.

It is important that stills are regularly inspected and maintained to retain their efficiency and

reduce deterioration. Damage, such as breakage of the collector plate, needs to be rectified. Rain

water collection is an even simpler technique than solar distillation and is preferable in areas with

400mm of rain annually, but requires a greater area and usually a larger storage tank. If ready-made

collection surfaces exist (such as house roofs) these may provide a less expensive source for

obtaining clean water.

COST OF MATERIAL = Rs. 500

COST OF LABOUR = Rs. 1500

COST OF GLASS = Rs. 1000

COST OF VACUUM PUMP = Rs. 2500

COST OF HEATER = Rs. 300

COST OF ACCESSORIES = Rs. 3200

TOTAL COST = Rs. 9000

FOR BASIC SOLAR STILL WE ARE GETTING 950 ml/day: Thus for 1 year the output is

347L. Let us assume 15 Rs/L as the cost of water. Then Rs.5,205 will be the actual cost to buy this

much amount of water which is received for just Rs. 3500 by using our solar still. So within 8

months we are getting our money back and the remaining is profit.

FOR BASIC SOLAR STILL WITH HEATER WE ARE GETTING 1300 ml/day: Thus for 1

year the output is 475L.Let us assume 15Rs/L as the cost of water. Then Rs.7125 will be the actual

cost to buy this much amount of water which is received for just Rs.5600 by using our solar still with

heater. So within 10 months we are getting our money back and the remaining is profit.

FOR BASIC SOLAR STILL WITH HEATER AND VACUUM PUMP WE ARE GETTING

1370ml/day: Thus for 1 year the output is 500L. Let us assume 15Rs/L as the cost of water.Then

Rs.7500 will be the actual cost to buy this much amount of water which is received for justRs.8100

by using our solar still with heater and vacuum pump. So within 13 months we are getting our money

back and the remaining is profit.

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139

There is a need for more water to drink so we suggest basic solar still with water heater is

more cost effective to use. A family of four requires a minimum output of 8L.Actually by using the

formula

Q=����

�.�

Where,

Q = daily output of distilled water (litres/day)

E = overall efficiency

G = daily global solar irradiation (MJ/m²)

A = aperture area of the still ie, the plan areas for a simple basin still (m²)

From the equation, The output for this solar still should be 1.2L/day based on the reading it is

correct. So by using heater our output was increased by more than 35%. So for producing 7L water

as output per day based on equation area, A need to be increased to 3.6m2. So material required is 7

times thus cost of material and labour increases and will be about Rs.6000 and cost of glass increases

to Rs.2000.

By using heater our output will be approximately 9.5L Thus for 1 year the output is 3467L.

Let us assume 15Rs/L as the cost of water. Then Rs.52012.5 will be the actual cost to buy this much

amount of water which is received for just Rs.22000 by using our solar still with heater. So within 6

months we are getting our money back and the remaining is profit.

10. CONCLUSION AND FUTURE WORKS

• The main fabrication process in this desalination system are metal cutting, welding, glass

cutting, sealing, painting and drilling.

• 3 litre/day can easily be obtained with such a portable system.

• For basic still without insulation productivity was 150 ml and maximum temperature of water

inside was 52.80C and when insulated productivity became 950 ml and temperature remain

same.

• For still with heater without insulation productivity was 320 ml and maximum temperature of

water inside was 54.40C and when insulated productivity became 1300ml and temperature of

water inside became 610C.

• For still with heater and vacuum pump with insulation productivity was 1370 ml and maximum

temperature of water inside was 600C.

• From the experimental analysis it is clear that proper insulation raised the output considerably.

This is basically due to the fact that the heat losses were arrested.

• The use of heater for just 40 minutes that is 0.83kWhr a day, increased the productivity about

35% more than the basic.

• It was found from the experimental analysis that increasing the ambient temperature will

increase the productivity, which shows that the system performed more distillation at higher

ambient temperatures.

• It was observed that when the water depth increases, the productivity decreased. These results

show that the water mass (water depth) has an intense effect on the distillate output of the solar

still system.

• Vacuum pump increases the productivity by a very small amount only.

• The use of thicker glasses gave faster condensing rate thereby increasing the productivity.

• The desalination process is cost effective. The best method that we suggest is to preheat water

before providing it into basic solar still.

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[1] Anirudh Biswas, Ruby, Distillation of water by solar energy, vsrd-map, vol. 2 (5), 2012,

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[2] M.Koilraj Gnanadson, P.Senthilkumar, G.Sivaraman, Design and Performance Analysis of a

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[4] A.E. Kabeel, Performance of solar still with a wick concave evaporation surface, Twelfth

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[5] Kaabi Abdennacer, Trad Rachid, Department of climatic engineering, university of mentouri,

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[6] Hazim Mohameed Qiblawey, Fawzi Banat, Solar thermal desalination technologies,

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[7] Prof.Nilamkumar SPatel, Prof.Reepen R Shah, Mr.Nisarg M Patel, Prof.J.K.Shah, Mr.Sharvil

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[9] Ajeet Kumar Rai, Vivek Sachan and Bhawani Nandan, “Experimental Study of Evaporation

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