Ijraset Journal For Research in Applied Science and Engineering Technology

Abstract

There is almost no water left on earth that is safe to drink without purification after 20-25 years from today. This is a seemingly bold statement, but it is unfortunately true. Only 1% of Earth\'s water is in afresh, liquid state, and nearly al of this is poluted by both diseases andtoxic chemicals. For this reason, purification ofwater supplies is extremely important. Keeping these things in mind, we have devised a model which wil convert the dirty/saline water into pure/potable water using the renewable source of energy (i.e. solar energy). The basic modes of the heat transfer involved are radiation, convection and conduction. The results are obtained by evaporation of the dirty/saline water and fetching it out as pure/drinkable water. The designed model produces 1.5 litres of pure waterfrom 14 litres of dirty water during six hours. The eficiency of plant is 64.37%. The TDS(Total Dissolved Solids) in the pure water is 81ppm.

Introduction

I. INTRODUCTION

Water is the basic necessity for human along with food and air. There is almost no water left on Earth that is safe to drink without purification. Only 1% of Earth's water is in a fresh, liquid state, and nearly all of this  is polluted by both diseases and  toxic  chemicals.  For  this  reason,  purification  of water  supplies  is  extremely important.

Moreover, typical purification systems are easily damaged or compromised by disasters, natural  or  otherwise.  This  results  in  a  very  challenging  situation  for individuals  trying to prepare  for  such  situations,  and  keep  themselves  and their families   safe  from  the  myriad diseases  and toxic chemicals present in untreated water.

Everyone wants to find  out the  solution  of above problem with the  available sources  of energy in order to achieve pure water. Fortunately there is a solution to these problems. It is a technology that is not only capable of removing a very wide variety  of  contaminants  in just one   step, but is simple, cost-effective, and environmentally friendly. That is use of solar energy.

A. About Solar Energy

The sun radiates the energy uniformly in all direction in the form of electromagnetic waves. When absorbed by body, it  increases  its  temperature.  It is a clean, inexhaustible, abundantly and universally available renewable energy[1].

Solar energy has the greatest potential of all the sources of renewable energy and if only a small amount of this form of energy could be used, it will be one of the most important supplies of energy, especially when other sources in the country have depleted.

This solution is solar water distillation.  It is not a new process, but it has not received the attention that it deserves. Perhaps this is because it is such a low-tech and flexible solution to water problems. Nearly anyone is capable of building a still and providing themselves with completely pure water from very questionable sources.  3.8x1024 joules of solar radiation is absorbed by earth and atmosphere per year. Solar power where  sun  hits  atmosphere  is  1017 watts  and the total demand is 1013 watts. Therefore, the sun gives us 1000 times more power than we need. If we can use 5% of this energy, it will be 50 times what the world will require. The energy radiated by the sun on a bright sunny day is 4 to 7 KWh per m2 [2].

II. INTRODUCTION TO SOLAR STILL

Solar distillation is a tried and true technology. The first known use of stills dates back to 1551 when it was used by Arab alchemists. Other scientists and naturalists used stills over the coming centuries including Della Porta (1589), Lavoisier(1862), and Mauchot (1869)[3].

The  first "conventional" solar  still  plant  was  built  in 1872 by  the  Swedish  engineer Charles  Wilson  in the  mining community of Las Salinas in what is now northern Chile (Region II). This still was   a  large basin-type still used for  supplying fresh water using brackish feed water to a  nitrate mining community. 

The plant used wooden bays which had blackened bottoms using logwood dye and alum. The total area of the distillation plant was 4,700  square meters. On a typical summerday this plant produced 4.9 kg of distilled water per square meter of still  surface, or  more than 23,000  litres  per  day.  Solar water Distillation system also called “Solar  Still” .  Solar  Still  can  effectively  purify seawater  &  even  raw sewage. Solar Stills can effectively removing Salts/minerals  {Na, Ca, As, Fe, Mn} ,Bacteria  {  E.coli, Cholera, Botulinus}, Parasites ,Heavy Metals & TDS[2].

Basic principal of working of solar still is “Solar energy heats water, evaporates it  (salts and microbes left behind), and condenses as clouds to return to earth as rainwater” .

A. Solar Still Operation

Water to be cleaned is  poured  into  the  still  to  partially  fill  the  basin.  The glass  cover  allows  the  solar  radiation  to pass into  the  still, which  is  mostly absorbed by the blackened base. This  interior  surface uses  a  blackened  material to improve absorption  of  the  sunrays.  The  water  begins  to  heat  up  and  the moisture content of the air trapped between the water surface and the glass cover increases. The heated water vapor  evaporates from the basin and condenses  on the inside of the glass cover. In this process, the salts and microbes that were in the original water  are left  behind. Condensed water trickles down the inclined glass cover to an interior collection trough and out to a storage bottle.

Feed  water  should  be  added  each  day  that  roughly  exceeds  the  distillate production to provide proper flushing of the basin water and to clean out  excess salts left behind during the evaporation process. If the still produced 3 litres of water, 9 litres of make-up water should be added, of which 6 litres leaves the still as excess to flush the basin.

B. Types of Solar Still

1. Basin Type: It consist of shallow, bracken basin of saline/impure watercovered with a sloping transparent  roof solar  radiation that passes through the transparent  roof heats the   water in blackened basin. Thus evaporating water     which gets condensed on the cooler under side of the glass and gets collected as  distillate attached to the glass[4].
2. Wick Type Solar Still: It consists of a wick instead of a basin. The saline/impure water is passed  through  the  wick  or  absorbed  by  the  wick  at  a  slow  rate  by capillary  action.  A waterproof liner is placed between the insulation and the wick. Solar energy is absorbed by the water in the wick which gets evaporated and later condensed on the underside of the glass and  finally  collected  in  the  condensate channel  fixed  on the  lower  side  of the  bottom surface[4].

III. DESIGN OF SOLAR DISTILLATION PLANT

A. Construction of Solar Still

The base of the solar still is made of G.I. box of dimension (4’ x 2’ x 10 cm). This box is embedded into another box  of wood shown in figure  1. Here length L=  65 cm, Breath B= 125cm, Height H= 30 cm. and at opposite side = 13 cm, Angle Θ = 150.

This also  contains  same box  of thermocol  inside  it between the  G.I box  and wooden box. The thermocol is having  15 cm thickness. The channel is fixed such that the water slipping on the surface of the glass will fall in this channel under the effect of gravity. A frame of fibre stick is fixed with the wooden box so that glass can rest on it. This completes the construction of the model. The holes for the inlet of water, outlet of brackish water and outlet of pure water is made as  per the  convenience.  We  have  made the  outlet  of brackish water  at right bottom of the model (seeing from front of the model), outlet of the pure water at the end of the channel and inlet at the right wall above the outlet.

B. Details of Different Parts of the System

1) Still Basin

It is the part of the system in which the water to be distilled  is kept.  It  is  therefore  essential  that  it  must  absorb  solar  energy.  Hence  it  is necessary  that  the  material have  high  absorbtivity  or  very  less  reflectivity  and very  less transmitivity. These are the criteria’s for selecting the basin materials.

Kinds  of the basin  materials that  can be used  are  as  follows: 

1.  Leather sheet,  2.  Ge silicon, 3. Mild steel plate, 4. RPF (reinforced platic) 5. G.I. (galvanised iron).

We have used blackened galvanised iron sheet(K= thermal conductivity= 300W/m0C) (3mm thick).( SIZE:: 4’ X 2’ X 10 cm BOX OF G.I.).

2) Side Walls

It generally  provides  rigidness  to  the  still.   But  technically  it provides thermal resistance to the heat transfer that takes place from the system to the surrounding. So it must be made from the material that is having low value of thermal conductivity and should be rigid enough to sustain its own weight and the weight of the top cover (refer fig.no.2).

Different kinds of materials that can be used are: 1) wood , 2) concrete, 3) thermocol, 4) RPF (reinforced plastic).

For  better  insulation we  have  used  composite  wall  of thermocol  (inside) and  wood (outside).  (Size:: wood(k= thermal conductivity=0.6W/m0C):--  8  mm thick, thermocol(k= thermal conductivity=0.02W/m0C):--- 15 mm thick).

Conclusion

From the graph 1, we can conclude that the increase in temperature and hence the evaporation is maximum in the period of 11:15am to 1:30 pm. The maximum temperature achieved is 530c which is at 1:30 pm. then the temperature decreases. The aim of our experiment was to get pure water from the brackish water available. The brackish water we have supplied was 14 litres and at the end of the experiment we got 1.5 litres. The experiment was carried out in winter season. The TDS level of purified water obtained is 81 PPM. So the water obtained is theoretically, the experiment should fetch out 2.33 litres. So the efficiency of the system is 6%.

References

[1] M.A.S. Malik, G.N Tiwari, A. Kumar and M.S. Sodha. “Solar Distillation”, Pergamon Press, Oxford, UK, 1982. [2] A. Kumar, A. Kumar, G.D. Sootha and P. Chaturvadi,” Performance of a multi-stage distillation system using a flat-plate collector”, Extended Abstract, ISES Solar World Congress, Kobe, Japan, 1989. [3] Akash BA, Mohsen MS, Osta O and Elayan Y ,” Experimental evaluation of a single-basin solar still using different absorbing materials”,renewable energy- 14, 1998,307-310. [4] B.B.sahoo, N.Sahoo, P.Mahanta, L.Borbora, P.kalita, ” Performance assesment of solar still using blackened surface and thermocole insulation” , October 2007. [5] Garg H.P and J.Prakash, “solar energy”, Tata McGraw Hill Publishing Co. 2008. [6] Rai G.D. “ Non- conventional energy sources” , Khanna Pub. 4thEd, 2000. [7] Tiwari G.N “solar energy”, Narosa Publishing House, 2002. [8] R.k.Rajput “ Heat and mass Transfer” S.Chand publication. [9] David incropera “ Heat and Mass Transfer” Wan Willey Publication

Copyright

Copyright © 2023 Dnyanesh Nakhate, Rohit Bijwe, Rudransh Belkhode, Manish Chandurkar, Ujiwal Khaper, Prof. Pravin Gupta. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.