Design, Fabrication and Performance Evaluation of Solar Water Still

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Design, Fabrication and Performance Evaluation of Solar Water Still

Design, Fabrication and Performance Evaluation of Solar Water Still

Arunabh Saikia

Nirman Jyoti Bhuyan

Tushar Pratim Sarma

B.E. Student

B.E. Student

B.E. Student

Mechanical Engineering Department

Mechanical Engineering Department

Mechanical Engineering Department

Jorhat Engineering College, Jorhat, India

Jorhat Engineering College, Jorhat, India

Jorhat Engineering College, Jorhat, India

Md. Piyar Uddin

Dhrupad Sarma

Dr. Parimal Bakul Barua

B.E. Student

Guest Faculty

Professor and H.O.D.

Mechanical Engineering Department

Mechanical Engineering Department

Mechanical Engineering Department

Jorhat Engineering College, Jorhat, India

Jorhat Engineering College, Jorhat, India

Jorhat Engineering College, Jorhat, India

Abstract- The paper presents the outcome of a project undertaken to design and fabricate a Solar Water Still, specifically for Jorhat (26.74°N, 94.22°E), Assam considering the quality of water of the region. The turbidity (25 NTU) and the iron content (5.06 mg/lit) are in excess in the water of Jorhat. The Solar Water Still has been designed with suitable insulations and a tilt mechanism. The average intensity of solar radiation in Jorhat is 4.47 kWh/m2/day. The collector used is a black painted Aluminium sheet of 1m2 area. Two glazing surfaces (normal window glass) separated by a distance of 10mm is used. The vessel where the evaporation of the water stored takes place is an angular copper vessel. Copper is used because of its high heat conducting ability. The output obtained is 210 mL on an average on a sunny day. The water was collected for a period of 3 months and physical and chemical tests were conducted in the Public Health Engineering laboratory. The results obtained from the test justified the water output to be of a better quality as it contained low contents of iron (0.55 mg/lit), fluoride (0.160 mg/lit), turbidity (6 NTU) and zero arsenic.

Keywords: Solar Water Still, Turbidity, NTU (Nephelometric Turbidity Unit), Glazing, Collector.

  1. INTRODUCTION

    Water is the basic necessity of life on planet Earth. All the living forms are directly or indirectly dependent on water. About 2.5% of the Earth's water is fresh water and 98.8% of that water is in ice and groundwater. India is a country where availability of pure water has always been a problem. In the North-Eastern region, specially in Assam people suffer from various harmful diseases due to this problem. Ability to purify the water is the major concern of the Government at the moment. Doing it with chemical methods and other industrial processes have proved to

  2. LITERATURE REVIEW

    In order to find out important factors about solar water still and its parts, a series of studies have been made. Sarma, D. et al. (2014) concluded experimentally that for double glazed flat plate collector the optimum spacing (Air gap) should be 10 mm for minimum heat loss. Lates, R. et al. (2008) experimentally shows that 83.91% efficiency is achievable with 2mm bottom and side insulation width, 0.1 mm absorber plate thickness. Panchal, N. et al. (2011) proved experimentally that the productivity of a solar water still increases by 35% when coupled with a flat plate collector. Ali, I. et al. (2012) concluded in his paper that the use of granular activated carbon at the bottom of the solar base increases the evaporation rate. Sethi, A.K. et al. (2013) concluded from his experiments that the distillate output obtained decreases with increase of water depth of the basin. Syed, F. et al. (2013) concluded experimentally that the performance of a solar water still can be increased efficiently by coupling the solar water still with evacuated tubes. In a 3 day experiment the volumetric flow rate of the ordinary still coupled with evacuated tubes increased from 48.7% to 49.5% and finally to 50.2%. Mehta, A. et al. (2011) developed a solar water still that produces 1.5 liters of pure water from 14 liters of dirty water, efficiency of the still being 64.37%. The TDS (total dissolved solids) in the pure water is 81 ppm. Senthilrajan, A. (2012) proved experimentally that by coupling a solar water still with a biomass water heater, its productivity increases during dull sunlight and at night hours by 47.2% compared to day time. Younis, O. et al, (2013) calculated mathematically the performance evaluation of a solar

    2 2

    be more expensive and less efficient. The use of solar energy is the perfect alternative solution to the problem. The advantage of this form of energy is that it is cheap, easily available, non- hazardous and most importantly non-polluting and non- diminishing in nature. Developing a Solar Water Still is a simple way of distilling water, using the heat from the sun to drive evaporation from humid soil and ambient air to cool a condenser film. The current study concentrates on developing a

    water still of area 0.24 m coupled with a Fresnel lens (1.3m ).

    The overall efficiency of the system was 57%, which is 62% more than the efficiency of simple solar water stills. Singh, P. et al. (2012) concluded that the distillation per unit evaporation area can be increased by decreasing the thermal inertia of the water mass. It was found that the unit produces about 20 liters of distilled water per m2, per standard day, under the same conditions of sunshine that would give a production of 2.5 to 3

    2

    solar water still which can be made locally here in Assam.

    liters/m

    day in a conventional, single basin solar still.

  3. EXPERIMENTAL SETUP

    The average intensity of solar radiation over Jorhat region is

    4.47 kWh/m2/day [3]; with an average atmospheric temperature around 25º C. The latitude and longitude angle for Jorhat is 26.74°N and 94.22°E respectively. Considering the above data about the location a solar water still has been designed and fabricated to evaluate the viability of the system as replacement of conventional water filtration system. The design is based on Eliodomestico solar water still. As stated before, modifications are incorporated to increase the output. Figure-1 shows a schematic diagram of the prototype.

    Figure 1: Schematic diagram of the prototype.

    The detailed description of the major components of the system is given below:

    The vaporizer: It is basically an angular copper vessel, which is connected firmly to the collector plate by nuts and bolts. The heat from the collector plate heats up the vessel along with the small amount of water kept inside it. When temperature rises, raw water starts evaporating. The water vapor thus produced get condensed in the condenser and collected. The copper vessel is made of 5mm thick copper plates which are joined by silver brazing. The vessel is then attached with the black coated aluminium collector plate with the help of nut and bolts. There are two pipes at the bottom of the copper vessel, one of which works as inlet while the other is used for flushing purpose (drain pipe). The outlet pipe is at the side of the vessel placed in such way that when the arrangement is inclined, the outlet is at the topmost position. The shape f the vaporizer is so chosen that when the whole system is tilted at 41° (41° being the optimum tilt angle for Jorhat), the base of the vessel remains parallel to the horizontal surface. This actually gives a better spread of the raw water over the base, increasing the heat transfer.

    Collecting vessel: The outlet is connected to a collecting vessel. The material of the vessel is chosen as stainless steel, which is safe for drinking water. A small vent pipe with a bent head is attached at the top surface. Steam from the vaporizer, while coming through the copper outlet pipe of 12.7 mm (0.5 inch) diameter, get condensed; and get collected in the collecting vessel. The uncondensed steam and air inside the collecting vessel leaves through the vent pipe. The bent shape of the vent pipe prevents rain water and dust from entering the vessel.

    Collector plate: A black painted aluminium plate of 2 mm thickness and 1 m2 surface area is used for absorbing the incident solar radiation which acts as the collector plate.

    Glazing surface: To minimize top heat loss two 5mm thick window glasses separated by a distance of 10mm are used as glazing [15].

    Insulations: Insulations are provided at the sides and bottom of the vaporizer to prevent heat loss. The walls of the vaporizer are covered using glass wool up to 200mm followed by 200mm of thermocol, to reduce cost and to give better airtight packing. Though thermocol has lower thermal conductivity (0.03 W/m.K) than glass wool (0.04 W/m.K)[17], thermocol cannot be used near the vaporizer, which will, otherwise melt due to the high temperature of the vaporizer walls. Figure-2 shows internal arrangement of the designed solar still.

    Figure 2: Internal arrangement of the solar still.

    Outer casing: The vaporizer along with the insulations around it, is kept inside a box made of 6mm thick plywood. The plywood box is further covered with a thin polythene to prevent rain from getting inside the box.

    Float chamber: A rectangular float chamber is made enclosing a float valve. The function of the float valve is to maintain the level of water inside the vaporizer. It maintains the water level inside the vaporizer tank at 5 mm. Figure-3 shows a pictorial view of the float chamber.

    Figure 3: Float Chamber.

    Tilt frame: A wooden tilt frame is incorporated to the design, so that the solar still can be kept at a desired angle.

    As Jorhat is in northern hemisphere, the prototype is placed facing south. As optimum tilt angle for Jorhat is 41°(refer to design analysis), the arrangement is tilted to 49° to the horizontal earth surface to ensure a tilt angle of 41º. Figure-4 shows a pictorial view of the field setup of the prototype.

    Figure 4: Pictorial view of the field setup of the prototype.

  4. DESIGN CALCULATIONS

    Here the optimum tilt angle is calculated along with the thickness of insulation.

    The optimum tilt angle () for a place is given by, = latitude ± 15° [18],

    Where, 15° is added to the latitude of the place if the design is intended for winter months and subtracted from the latitude if it will be primarily used during summer months.

    For Jorhat latitude = 26°75´

    Therefore, optimum tilt angle for Jorhat jorhat=26°75´+15°=41°75´41° (considering winter months).

    Heat Losses and Insulation Required

    Heat loss from the system occurs from the bottom, side and through top of the vessel. To keep the heat loss through the bottom to 10 W/m2, if t be the thickness of glass wool (thermal conductivity= 0.04 W/m.K) insulation required combining with 6 mm(0.006 m) of plywood (thermal conductivity= 0.13 W/m.K) when collector temperature (Tc) is assumed as 100°C and atmospheric temperature (Ta) is 25°C,then according to the following equation we get

    Rate of heat loss=

    Figure 5: Detailed dimensional view of the vaporizer tank.

    Figure 6: Isometric wireframe view of the vaporizer tank.

    The network diagram for the calculations of heat loss from the vaporizer tank to the surroundings is shown in Figure-7.

    t = 298 mm

    300 mm of glass wool as shown in Fig. 2 is used as bottom insulation when measured from the middle point of the base. With respect to (1mx1m) collector the sides insulations required are also shown in Figure-2.

    The following assumptions are made while calculating the heat losses:

    1. Steady state conditions.

    2. No heat transfer from edges and corners of the vaporizer tank.

    3. Heat transfer area corresponds to the dimensions of the vaporizer tank.

    4. Thermal heat loss from the collector plate through insulation depth is neglected.

      Figure 7: Resistance network diagram.

      The area of the surfaces are-

      Top surface (300 mm ×200 mm) =0.06 m2 Bottom surface (300

      mm ×305 mm) = 0.0915 m2

      Left hand side surface (300 mm ×250 mm) = 0.075 m2 Right hand side surface (20 mm ×300 mm) = 0.006 m2

      25020 2

    5. Resistance offered by 6mm plywood is neglected.

      Front and back surface (20x

      ) = 0.027 m each

      2

      A detailed dimensional view and an isometric view of the vaporizer tank is shown in Figure-5 and Figure-6 respectively.

      As the bottom insulation is 300 mm of glass wool the

      corresponding insulations used are-

      For right hand and left hand side surfaces 200 mm of glass wool (thermal conductivity= 0.04 W/m. K) and 200 mm of thermocol (thermal conductivity= 0.03 W/m. K) on each side. For the front and back surfaces 175 mm of glass wool and 175 mm of thermocol on each side.

      The individual resistance of the network are- For the left hand side surface R1= R1'+R1''

      = 155.55 K/W

      For the right hand side surface R2= R2'+R2''

      =1944.44 K/W

      For the front and back surfaces R3= R4 = (R3'+R3'') or (R4'+R4'')

  5. RESULTS AND DISCUSSION

    After installation of the prototype, data collection is done for the months of February, March and April of the year 2015. Every day at around 1 PM the weather temperature is noted and collected distillated water is measured at 7 PM. At the same time the raw water is replenished in the raw water reservoir and remaining water in the vaporizer tank is drained out.

    Figure-8 shows an overall graphical representation of the temperature and collected water output. The actual experimental data collected during months February, March and April are shown in Annexure (Table 1, Table 2 and Table 3).

    = 378.08 K/W

    For bottom surface R

    = 81.97 K/W

    Figure 8:An overall representation of water output during February, March and April with temperature.

    Where Ri' is resistance due to thermocol insulations and Ri'' is the resistance due to glass wool insulation. The resistance R5 is completely due to glass wool insulation.

    The resistances are in parallel. If Req be the equivalent resistance then

    =0.0244 W/K

    Therefore Req = 40.98 K/W or 40.98 °C/W The heat loss through the bottom and the sides Q = 1.83 W

    The dimensions of the designed parts are shown in Table 1.

    The maximum output obtained was 662 ml on 24th of April, temperature being 36º C. On rainy days no distillate was obtained. From the graph (Figure-8) it can be seen that distill water output from the still depends on the weather temperature of the day. High weather temperature leads to low heat loss and less amount of heat is required to evaporate the water.

    Table 2 shows a tally of the three water samples, raw water (deep tube well water), tap water (chemically treated water) and project output, tested at Public Health Engineering Laboratory, Jorhat (Assam).

    Parameter Name

    Desirable Limit

    Results

    Raw Water

    J.E.C

    Tap Water

    Project Output

    TDS

    5.0 10

    25

    17

    06

    NIL

    NTU

    Conductivity

    500

    2000

    146

    129

    60

    68

    mg/lit

    pH value

    500

    2000

    298

    263.4

    123.4

    µS/cm

    Iron as Fe

    6.5 8.5

    7.14

    7.36

    7.14

    6.92

    mg/lit

    Total Alkalinity CaCo3

    as

    0.2 1.0

    5.06

    3.34

    0.55

    0.22

    mg/lit

    Arsenic

    200 – 600

    148

    152

    42

    mg/lit

    Fluoride

    0.05

    0.039

    0.024

    0

    mg/lit

    TDS

    1.0 – 1.5

    0.70

    0.45

    0.160

    NIL

    mg/lit

    Conductivity

    5.0 10

    25

    17

    06

    NIL

    NTU

    Table 2: Tally of the tests conducted

    Parts

    Materials

    Dimensions

    Glazing surface

    Glass(2 pieces)

    1m x 1m

    Collector plate

    Aluminium

    1m x 1m

    Copper vessel

    copper

    1 ft. x 1 ft. (4 Pieces)

    Bottom insulations

    Glass wool

    Thickness-30 cm

    Side Insulation

    (a) Thermocol

    Thickness- 20 cm

    (b) Glass wool

    Thickness- 20 cm

    Plywood Box

    Plywood (6mm)

    L- 106cm, B-

    106cm, H- 42 cm

    Tilt stand

    wood

    ———

    Water reservoir stand

    Bamboo

    Height- 170cm

    Float valve arrangement

    Plastic

    ———

    Pipes

    G.I

    ½ inch diameter

    Ball Valve

    Brass

    ½ inch diameter

    Collecting Vessel

    Stainless steel

    ———-

    It is evident from the above table that the turbidity content is found to be nil as compared to the other samples. Also harmful minerals like Arsenic (prolonged exposure can lead to Cancer), and Fluoride (responsible for tooth decay, cavities etc.) are found to be nil whereas Iron (responsible for coloring of water

    10.03.15

    476

    34

    Sunny

    11.03.15

    530

    36

    Sunny

    12.03.15

    420

    33

    Sunny

    13.03.15

    408

    32

    Scattered Clouds

    14.03.15

    390

    31

    Partly cloudy

    15.03.15

    492

    34

    Sunny

    16.03.15

    510

    35

    Sunny

    17.03.15

    494

    34

    Sunny

    18.03.15

    524

    35

    Sunny

    19.03.15

    518

    35

    Sunny

    20.03.15

    544

    36

    Sunny

    21.03.15

    484

    35

    Sunny

    22.03.15

    448

    34

    Sunny

    23.03.15

    470

    35

    Sunny

    24.03.15

    470

    34

    Sunny

    25.03.15

    490

    35

    Sunny

    26.03.15

    432

    33

    Sunny

    27.03.15

    432

    33

    Sunny

    28.03.15

    496

    34

    Sunny

    29.03.15

    396

    31

    Partly cloudy

    30.03.15

    538

    35

    Sunny

    31.03.15

    504

    35

    Sunny

    and works as a medium for growth of bacteria) is found within the desirable limit.

    A bacterial test was done to check bacterial contamination in the output water. The test was done with the help of a Blue Bacta Vial. In the Blue Bacta Vial test, the water does not turn black in colourand hence it can be concluded that the project output is fit for drinking. The video of the Blue Bacta Vial test performed can be found on the following link: https://youtu.be/znYtVU7lVcc.

  6. CONCLUSION

The Solar Water Still System was installed and output water was collected for the months of February, March and April. The amount of water obtained was at an average of 400-410 ml per day. Maximum output obtained was 662 ml of distilled water on an average sunny day. Tests were conducted on the collected sample and comparisons were made between the raw water supplied for purification in the college campus, the college supply water (chemically treated) and the collected output. The results show, the project output contains low contents of iron (0.22 mg/lit) and zero fluoride, turbidity and arsenic; hence it can be concluded that the

project output is safe for drinking. Moreover the model require

DATE

QUANTITY COLLECTED

WEATHER TEMPERATURE ( 0C)

WEATHER CONDITION

20.02.15

367.5

25

Cloudy

21.02.15

328

27

Partly cloudy

22.02.15

336

27

Partly cloudy

23.02.15

0

24

Rainy

24.02.15

0

25

Rainy

25.02.15

284

26

Cloudy

26.02.15

300

26

Cloudy

27.02.15

332

27

Cloudy

28.02.15

0

Rainy

no maintenance cost and hence makes it economical for use. There is scope of further experimentation to study the system performance incorporating the following attachments:

    • Attachment of tracking system

    • Use of selective coatings

    • Use of a suction pump

    • Multistage distillation system

Appendix 1: Record showing water output during February15 Appendix 2: Record showing water output during Marcp5

DATE

QUANTITY COLLECTE

WEATHER TEMPERATURE (0C)

WEATHER CONDITION

01.04.15

0

23

Rainy

02.04.15

0

26

Rainy

03.04.15

0

24

Rainy

04.04.15

0

24

Rainy

05.04.15

0

25

Rainy

06.04.15

0

22

Rainy

07.04.15

0

24

Rainy

08.04.15

420

32

Partly cloudy

09.04.15

416

31

Scattered Clouds

10.04.15

492

34

Sunny

11.04.15

516

35

Sunny

12.04.15

490

32

Partly cloudy

13.04.15

470

32

Sunny

14.04.15

450

32

Sunny

15.04.15

470

34

Partly cloudy

16.04.15

484

35

Scattered Clouds

17.04.15

536

34

Sunny

18.04.15

590

36

Sunny

19.04.15

596

35

Partly cloudy

20.04.15

630

36

Sunny

21.04.15

610

35

Sunny

22.04.15

640

37

Sunny

23.04.15

652

35

Sunny

24.04.15

662

36

Sunny

25.04.15

620

36

Sunny

26.04.15

570

37

Sunny

27.04.15

596

35

Sunny

28.04.15

620

36

Sunny

29.04.15

630

34

Sunny

30.04.15

650

36

Sunny

Appendix 3: Record showing water output during April 2015

DATE

QUANTITY COLLECTED

WEATHER TEMPERATURE (0C)

WEATHER CONDITION

01.03.15

0

27

Rainy

02.03.15

418

31

Partly cloudy

03.03.15

454

32

Scattered Clouds

04.03.15

392

28

Cloudy

05.03.15

294

24

Partly Sunny

06.03.15

326

27

Partly Sunny

07.03.15

360

30

Scattered Clouds

08.03.15

428

32

Partly cloudy

09.03.15

492

34

Sunny

REFERENCES

[1] Daimanti, G.; Eliodomestico; Accessed on 21/08/2014;

Available at: http://www.gabrielediamanti.com/projects/eliodomestico— how-does- itwork/

[2] India Solar Resource Maps; Solar Energy Centre, Ministry of New and Renewable Energy, Govt. of India; Accessed on 12/09/2014;

Available at: http://mnre.gov.in/sec/DNI_Annual.jpg

[3] Atmospheric Science Data Centre; National Aeronautics and Space Administration (NASA), USA; Accessed on 12/07/2012; Available at: https://eosweb.larc.nasa.gov/cgibin/sse/grid.cgi.

[4] Lates, R.; Visa, I. and Lapusan, C. (2008); Mathematical optimization of solar thermal collectors efficiency function using MATLAB, 4th IASME/WJSEAS International Conference on Energy, Environment, Ecosystems and Sustainable Development (EEESD'08), Algarve, Portugal.June 11-13.

[5] Matuska, T.; Zmrhal, V. and Metzger, J. (2009); Detailed Modeling of Solar Flat-Plate Collectors with Design tool KOLEKTOR 2.2, Eleventh International IBPSA Conference, Glasgow, Scotland, July 27-30.

[6] Mehta, A.; Vyas, A; Bodar, N and Lathiya, D. (2011); Design of Solar distillation system, International Journal of Advanced Science and Technology, Vol. 29

[7] Panchal, H.N.; Patel, M.; Patel, B.; Goswami, R. and Doshi, M. (2011); A comparative analysis of single slope solar still coupled with flat plate collector and passive solar still; International Journal of Research and Reviews in Applied Science, Vol.7 (2), Bhandu, Mehsana, Gujarat, India, May .

[8] Ali, I.; Joseph, B.; Karthikeyan, R. and Yuvraj, R. (2012); Performance Investigation of Solar Still Integrated to Solar Pond, Bonfring International Journal of Power Systems and Integrated Circuits,Vol. 2.

[9] Franceschetti, P. and Gonella, F. (2012); New Solar Still with the Suction of Wet Air: A Solution in Isolated Areas, Journal of Fundamentals of Renewable Energy and Applications, Vol. 2.

[10] A. Senthilrajan (2012); Experimental study on single basin solar still augmented with biomass water heater, International Journal of Engineering Research and Technology, Vol. 1 (8).

[11] Singh, P.; Singh, P.; Singh, J.; Singh, R. I. and Kundu, K. (2012); Performance Evaluation of Low Inertia Multi-Stage Solar Still, International multiconference of Engineers and Computer scientists, Hong Kong, Vol. 2.

[12] Sethi, A. K. and Dwivedi, V. K. (2013); Design, Fabrication, and Performance Evaluation of Double Slope Active Solar Still under Forced Circulation Mode, International Journal of Thermal & Environmental Engineering, Vol. 6 (1), pp 2734.

[13] Younas, O.; Banat, F.; Islam, D. (2013); Performance Assessment of a MultiStage Solar Still Coupled with Fresnel Lens for Water Desalination, Thermal Energy and Power engineering (TEPE), Vol. 2(4), pp. 164-170.

[14] Firozuddin, S. and Ahmad, A.N. (2014); Single Basin Solar Still Performance with Evacuated Tubes Solar Collector, IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE),e-ISSN: 2278-1684,pp. 64-70.

[15] Sarma, D.; Barua, P.B. and Hatibaruah, D. (2014); Optimization of Glazing Cover Parameters of a Solar Flat Plate Collector (FPC), International Journal of Engineering Trends and Technology (IJETT), Vol. 14(2), pp. 74-80.

[16] Sarma, D.; Gogoi, R; Nath, B; Konwar, S. and Meitei, C.L.(2014); Design, Fabrication and the Experimental Performance Evaluation of Flat Plate Solar Water Heater specially for Jorhat,Assam(26.75°N,94.22°E), International Journal of Engineering Trends and Technology(IJETT), Vol. 12 (7), pp.341-352.

[17] Thermal Conductivity of Metals; The Engineering Tool Box; Accessed on 12/09/2014; Available at: http://www.engineeringtoolbox.com/thermal-conductivitymetals- d_858.html

[18] Sukhatme, S.P. and Nayak, J.K., (2013); Liquid Flat-Plate Collectors, Solar energy- Principles of thermal collection and storage, Third edition (Fifteenth reprint), McGraw Hill education (India private limited ), New Delhi (India) , pp144-146.

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