A

Project Report

On

“SOLAR STILL”

Submitted in partial fulfillment for the award of the degree of

Bachelor of Technology

In

Mechanical Engineering

from

RAJASTHAN TECHNICAL UNIVERSITY, KOTA

Session 2012-13

Guided By: - Submitted By: -

Mr. Kapil Jain Aman Agrawal

Lecturer,Mech.Deptt. Bharat Ajwani

Vit (East), Jaipur Ashok Kumar Meena

Amit Upadhyay

Kirodee Lal Meena

Manoj kumar Nagar

B.Tech. IV Yr. VIII Sem

Mechanical Engg.

Submitted to-

DEPARTMENT OF MECHANICAL ENGINEERING

VIVEKANANDA INSTITUTE OF TECHNOLOGY (EAST) VIT Campus, NRI Road, Jagatpura, Jaipur-303012

Deptt. Of Mechanical Engineering (Vit-east, Jaipur) Magnetic Refrigeration Page ii

ACKNOWLEDGEMENT

We take this momentous opportunity to express our heartfelt gratitude, ineptness

& regards to vulnerable and highly esteemed guide, Mr. Rahul Goyal, Head of

Department of Mechanical Engineering, Vit (East) for providing us an opportunity

to present our project on “SOLAR STILL”.

We with full pleasure converge our heartiest thanks to Our project guide

Mr. kapil jain,Lecturer,Department of mechanical engineering, Vivekananda

institute of technology(East) and to Project coordinator Mr. Bhanu Pratap Singh,

Lecturer, Department of Mechanical Engineering for their invaluable advice and

wholehearted cooperation without which this project would not have seen the

light of day.

We attribute hearties thanks to all the faculty of the department of ME

and friends for their valuable advice and encouragement.

Aman Agrawal Amit upadhyay Ashok Kumar Meena Bharat Ajwani Kirodee lal Meena Manoj kumar Nagar

Deptt. Of Mechanical Engineering (Vit-east, Jaipur) Magnetic Refrigeration Page iii

CERTIFICATE

This is to certify that Aman Agrawal, Amit upadhyay, Bharat ajwani, Ashok

Kumar meena, kirodee lal Meena,Manoj Nagar; Students of IVth Year, B.Tech.

VIIIth Semester Mechanical Engineering of Vit (East), Jaipur during the academic

session 2012-13 is working for his project under my guidance entitled “Solar Still”

in the partial fulfillment for award the degree of Bachelor of Technology in

Mechanical Engineering from Rajasthan Technical University, Kota.

Their Work is Found…………….

Project Guide Project Coordinator

Mr. Kapil Jain Mr. Bhanu Pratap Singh Lecturer, Lecturer, Deptt. Of Mechanical Engg. Deptt. Of Mechanical Engg. Vit (East), Jaipur Vit (East), Jaipur

Deptt. Of Mechanical Engineering (Vit-east, Jaipur) Magnetic Refrigeration Page iv

CONTENTS

Title Page No

ABSTRACT………………………………………………….. 1

CHAPTER 1 INTRODUCTION………………………………….………... 2

CHAPTER 2 WATER PURIFICATION…………………………………... 3-4

2.1 WATER PURIFICATION………………………… 3

2.2 OPTIONS FOR WATER PURIFICATION…….. 4

2.3 BENEFITS OF DISTILLATION………………… 4

2.4 NEEDS OF WATER PURIFICATION…………… 4

CHAPTER 3 SOLAR WATER DISTILLATION………………………….. 5 -6

CHAPTER 4 BASIC CONCEPT OF SOLAR WATER DISTILLATION…. 7-8

4.1 SUPPLY FILL PORT……………………..……….. 7

4.2 OVERFLOW PORT…………………………..……. 8

4.3 DISTILLED OUTPUT COLLECTION PORT..…… 8

CHAPTER 5 WORKING OF SOLAR STILL………………………………. 9-10

CHAPTER 6 DESIGN OF SOLAR STILL…………………………………. 11-16

6.1 DESIGN OBJECTIVES …………………………. 11

6.2 DESIGN CONSIDERATIONS………….………… 11

6.3 SOME PROBLEMS WITH SOLAR STILLS ……… 12

6.4 CONCEPTS FOR MAKING A GOOD SOLAR STILL 12

6.5 DESIGN TYPES AND THEIR PERFORMANCE…… 13

CHAPTER 7 CAPABILITIES……………………………………………….. 17

Deptt. Of Mechanical Engineering (Vit-east, Jaipur) Magnetic Refrigeration Page v

CHAPTER 8 USER EXPERIENCES……………………………………..…. 18-19

CHAPTER 9 COST ANALYSIS & MATERIALS……………………………… 20-23

CHAPTER 10 BERKAD’S APPLICATIONS……………………………………. 24-27

CHAPTER 11 WATER PURIFIERS…………………………………………..…. 28-32

CHAPTER 12 SOLAR PANELS…………………………………………..…. 33-34

CHAPTER 13 WOULD A SOLAR STILL SUIT OUR NEEDS?……….……… 35

CONCLUSIONS ……………………………………….……………… 36

REFERENCES ………………...………………................................ 37

Deptt. Of Mechanical Engineering (Vit-east, Jaipur) Magnetic Refrigeration Page vi

FIGURE LIST

Figure Page No

Fig.1.1 Basic concept of Solar Water Distillation 08

Fig.1.2 Working of Solar Still 09 Fig.1.3 Layout of Solar Still Plant 10 Fig.1.4 Components of Solar Still 16 Fig. 1.5 Passive Solar Still Design 22 Fig. 1.6 Design Drawing of Solar Still, Dimensions in cm. 23 Fig. 1.7 Berkads practical Application 25

1

Literature Review

ABSTRACT

The purpose of this project is to design a water distillation system that can purify water

from nearly any source, a system that is relatively cheap, portable, and depends only on

renewable solar energy.

The motivation for this project is the limited availability of clean water resources

and the abundance of impure water available for potential conversion into potable

water, In addition, there are many coastal locations where seawater is abundant but

potable water is not available. Our project goal is to efficiently produce clean drinkable

water from solar energy conversion.

Distillation is one of many processes that can be used for water purification. This

requires an energy input as heat, electricity and solar radiation can be the source of

energy. When Solar energy is used for this purpose, it is known as Solar water

Distillation. Solar Distillation is an attractive process to produce portable water using

free of cost solar energy. This energy is used directly for evaporating water inside a

device usually termed a „Solar Still‟. Solar stills are used in cases where rain, piped, or

well water is impractical, such as in remote homes or during power outages. Different

versions of a still are used to desalinate seawater, in desert survival kits and for home

water Purification. For people concerned about the quality of their municipally-supplied

drinking water and unhappy with other methods of additional purification available to

them, solar distillation of tap water or brackish groundwater can be a pleasant, energy-

efficient option. Solar Distillation is an attractive alternative because of its simple

technology, non-requirement of highly skilled labour for maintenance work and low

energy consumption.

The use of solar thermal energy in seawater desalination applications has so far

been restricted to small-scale systems in rural areas. The reason for this has mainly

been explained by the relatively low productivity rate compared to the high capital cost.

However, the coming shortage in fossil fuel supply and the growing need for fresh water

in order to support increasing water and irrigation needs, have motivated further

development of water desalination and purification by renewable energies.

2

CHAPTER-1

INTRODUCTION

Water is a basic necessity of man along with food and air. Fresh water resources

usually available are rivers, lakes and underground water reservoirs. About 71% of the

planet is covered in water, yet of all of that 96.5% of the planet's water is found in

oceans, 1.7% in groundwater, 1.7% in glaciers and the ice caps and 0.001% in the air

as vapor and clouds, Only 2.5% of the Earth's water is freshwater and 98.8% of that

water is in ice and groundwater. Less than 1% of all freshwater is in rivers, lakes and

the atmosphere.

Distillation is one of many processes available for water purification, and sunlight

is one of several forms of heat energy that can be used to power that process. To dispel

a common belief, it is not necessary to boil water to distill it. Simply elevating its

temperature, short of boiling, will adequately increase the evaporation rate. In fact,

although vigorous boiling hastens the distillation process it also can force unwanted

residue into the distillate, defeating purification.

Solar Distillation is by far the most reliable, least costly method of 99.9% true

purification of most types of contaminated water especially in developing nations where

fuel is scarce or too expensive. Solar distillation is used to produce drinking water or to

produce pure water for lead acid batteries, laboratories, hospitals and in producing

commercial products such as rose water. Conventional boiling distillation consumes

three kilowatts of energy for every gallon of water, while solar distillation uses only the

free pure power of the sun. Expensive filtration and deionizing systems are even more

expensive to purchase and use and will not totally purify the water by removing all

contaminants. No additional heat or electrical energy is required in our still and even

after the sun sets, distillation continues at a slower pace into the night. Recently, we‟ve

been experimenting with a unique optional solar energy booster using our top quality

“Sola Reflex reflector” to increase the water vaporization by increasing the temperature

on the internal fluid heat absorber. This will add efficiency and increases the amount of

daily pure water production.

3

CHAPTER-2

WATER PURIFICATION

3.1 Water Purification:-

It is the process of removing undesirable chemicals, biological contaminants,

suspended solids and gases from contaminated water. The goal is to produce water fit

for a specific purpose. Most water is purified for human consumption (drinking water),

but water purification may also be designed for a variety of other purposes, including

meeting the requirements of medical, pharmacological, chemical and industrial

applications. In general the methods used include physical processes such

as filtration, sedimentation, and distillation, biological processes such as slow sand

filters or biologically active carbon, chemical processes such

as flocculation and chlorination and the use of electromagnetic radiation such

as ultraviolet light.

3.2 Options for water purification:-

There are four possible ways of purifying water for drinking purpose:-

1. Distillation

2. Filtration

3. Chemical Treatment

4. Irradiative Treatment

Considering the areas where the technology is intended to be used we can rule

out few of the above mentioned methods based on the unavailability of materials or

costs. Chemical treatment is not a stand alone procedure and so is irradiative treatment.

Both can act only remove some specific impurities and hence can only be implemented

in coordination with other technologies.

This analysis leaves us with two methods – Distillation and Filtration. By weighting the

Positive and negatives of both the methods we decided to go by the first one. The most

Important considerations were that of complexity, higher maintenance and subsequent

costs coupled with need of other sophisticated supporting equipments.

4

3.3 Benefits of Distillation:-

Finally we decided to go by distillation method owing to the following benefits:-

1. It produces water of high quality.

2. Maintenance is almost negligible.

3. Any type of water can be purified into potable water by means of this process

4. The system will not involve any moving parts and will not require electricity to

Operate.

5. Wastage of water will be minimum.

3.4 Needs and Specifications of water purification:-

Our project centers on converting the roughly 99.6% of water that is, in its natural

form, undrinkable, into clean and usable water. After researching and investigation, we

outlined our needs to be the following:-

1. Efficiently produce at 2 gallons of potable water per day minimum

2. Able to purify water from virtually any source, included the ocean

3. Relatively inexpensive to remain accessible to a wide range of audiences

4. Easy to use interface

5. Intuitive setup and operation

6. Provide clean useful drinking water without the need for an external energy

source

7. Reasonably compact and portable

Our aim is to accomplish this goal by utilizing and converting the incoming

radioactive power of the sun's rays to heat and distill dirty and undrinkable water,

converting it into clean drinkable water. A solar parabolic trough is utilized to effectively

concentrate and increase the solid angle of incoming beam radiation, increasing the

efficiency of the system and enabling higher water temperatures to be achieved.

5

CHAPTER-3

SOLAR WATER DISTILLATION

Solar energy is a very large, inexhaustible source of energy. The power from the sun

intercepted by the earth is approximately 1.8×1011MW., which is many thousands times

larger than the present all commercial energy consumption rate on the earth. Thus in

principle, solar energy could supply all the present and future energy needs of the world

on a continuous basis. This makes it one of the most promising of all the unconventional

energy sources. In addition to its size, solar energy has two other factors in its favor.

Firstly, unlike fossil fuels and nuclear power, it is an environmentally clean source of

energy. Secondly, it is free and available in adequate quantity.

Solar water distillation is a solar technology with a very long history and

installations were built over 2000 years ago, although to produce salt rather than

drinking water. Documented use of solar stills began in the sixteenth century. An early

large-scale solar still was built in 1872 to supply a mining community in Chile with

drinking water. Mass production occurred for the first time during the Second World War

when 200,000 inflatable plastic stills were made to be kept in life-crafts for the US Navy.

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

water, is 2260 kilo joules 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 2260 kJ. 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 2260 kJ/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.

Human beings need 1 or 2 litres of water a day to live. The minimum requirement

for normal life in developing countries (which includes cooking, cleaning and washing

clothes) is 20 litres per day .Yet some functions can be performed with salty water and a

typical requirement for distilled water is 5 litres per person per day. Therefore 2m2 of

solar still are needed for each person served. Solar stills should normally only be

considered for removal of dissolved salts from water. For output of 1m3/day or more,

vapour compression or flash evaporation will normally be least cost.

6

Solar distillation systems can be small or large. They are designed either to serve

the needs of a single family, producing from ½ to 3 gallons of drinking water a day on

the average, or to produce much greater amounts for an entire neighbourhood or

village. In some parts of the world the scarcity of fresh water is partially overcome by

covering shallow salt water basins with glass in greenhouse-like structures. These solar

energy distilling plants are relatively inexpensive, low-technology systems, especially

useful where the need for small plants exists. Solar distillation of potable water from

saline (salty) water has been practiced for many years in tropical and sub-tropical

regions where fresh water is scare. However, where fresh water is plentiful and energy

rates are moderate, the most cost-effective method has been to pump and purify.

Solar distillation is a relatively simple treatment of brackish (i.e. contain dissolved

salts) water supplies. In this process, water is evaporated; using the energy of the sun

then the vapour condenses as pure water. This process removes salts and other

impurities. Solar distillation is used to produce drinking water or to produce pure water

for lead acid batteries, laboratories, hospitals and in producing commercial products

such as rose water. It is recommended that drinking water has 100 to 1000 mg/l of salt

to maintain electrolyte levels and for taste. Some saline water may need to be added to

the distilled water for acceptable drinking water.

Generally, solar stills are used in areas where piped or well water is impractical.

Such areas include remote locations or during power outages .Distillation are therefore

normally considered only where there is no local source of fresh water that can be

easily pumped or lifted. One of the main setbacks for solar desalination plant is the low

thermal efficiency and productivity. In areas that frequently loss power, Solar stills can

provide an alternate source of clean water. A large use of solar stills is in developing

countries where the technology to effectively distill large quantities of water has not yet

arrived.

7

CHAPTER-4

BASIC CONCEPT OF SOLAR WATER DISTILLATION

The basic principles of solar water distillation are simple yet effective, as distillation

replicates the way nature makes rain. The sun's energy heats water to the point of

evaporation. As the water evaporates, water vapor rises, condensing on the glass

surface for collection. This process removes impurities such as salts and heavy metals

as well as eliminates microbiological organisms. The end result is water cleaner than

the purest rainwater. The SolAqua still is a passive solar distiller that only needs

sunshine to operate. There are no moving parts to wear out.

The distilled water from a SolAqua still does not acquire the "flat" taste of

commercially distilled water since the water is not boiled (which lowers pH). Solar stills

use natural evaporation and condensation, which is the rainwater process. This allows

for natural pH buffering that produces excellent taste as compared to steam distillation.

Solar stills can easily provide enough water for family drinking and cooking needs.

Solar distillers can be used to effectively remove many impurities ranging from

salts to microorganisms and are even used to make drinking water from seawater.

SolAqua stills have been well received by many users, both rural and urban, from

around the globe. SolAqua solar distillers can be successfully used anywhere the sun

shines.

The SolAqua solar stills are simple and have no moving parts. They are made of

quality materials designed to stand-up to the harsh conditions produced by water and

sunlight. Operation is simple: water should be added (either manually or automatically)

once a day through the still's supply fill port. Excess water will drain out of the overflow

port and this will keep salts from building up in the basin. Purified drinking water is

collected from the output collection port.

4.1 Supply Fill Port:

Water should be added to the still via this port. Water can be added either manually or

automatically. Normally, water is added once a day (in the summer it's normally best to

fill in the late evening and in the winter, in the early morning). Care should be taken to

add the water at a slow enough flow rate to prevent splashing onto the interior of the still

glazing or overflowing into the collection trough.

8

4.2 Overflow Port:

Once the still basin has filled, excess water will flow out of this port. SolAqua

recommends three times daily distilled water production to be allowed to overflow from

the still on a daily basis to prevent salt build-up in the basin. If your still produced 2

gallons of product water then you should add 6 gallons of fresh feed water through the

fill port. If flushed like this on a daily basis, the overflow water can be used for other

uses as appropriate for your feed water (for example, landscape watering).

4.3 Distilled Output Collection Port:

Purified drinking water is collected from this port, typically with a glass collection

container. Stills that are mounted on the roof can have the distillate output piped directly

to an interior collection container. For a newly installed still, allow the collection trough to

be self-cleaned by producing water for a couple of days before using the distillate output

Fig.1.1 Basic concept of Solar Water Distillation

9

CHAPTER-5

WORKING OF SOLAR STILL

Fig.1.2 Working of Solar Still

Solar stills are called stills because they distill, or purify water. A solar still

operates on the same principle as rainwater: evaporation and condensation. The water

from the oceans evaporates, only to cool, condense, and return to earth as rain. When

the water evaporates, it removes only pure water and leaves all contaminants behind.

Solar stills mimic this natural process.

A solar still has a top cover made of glass, with an interior surface made of a

waterproof membrane. This interior surface uses a blackened material to improve

absorption of the sun's rays. Water to be cleaned is poured into the still to partially fill

the basin. The glass cover allows the solar radiation (short-wave) to pass into the still,

10

which is mostly absorbed by the blackened base. The water begins to heat up and the

moisture content of the air trapped between the water surface and the glass cover

increases. The base also radiates energy in the infra-red region (long-wave) which is

reflected back into the still by the glass cover, trapping the solar energy inside the still

(the "greenhouse" effect). 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. There are no

moving parts in Solar still and only the sun‟s energy is required for operation.

The still is filled each morning or evening, and the total water production for the

day is collected at that time. The still will continue to produce distillate after sundown

until the water temperature cools down. 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.

Fig.1.3 Layout of Solar Still Plant

The most important elements of the design are the sealing of the base with black

11

CHAPTER-6

DESIGN OF SOLAR STILL

6.1 Design objectives for an efficient solar still:-

For high efficiency the solar still should maintain:-

a high feed (undistilled) water temperature

a large temperature difference between feed water and condensing surface

Low vapour leakage.

A high feed water temperature can be achieved if:-

A high proportion of incoming radiation is absorbed by the feed water as heat.

Hence low absorption glazing and a good radiation absorbing surface are

required

heat losses from the floor and walls are kept low

The water is shallow so there is not so much to heat.

A large temperature difference can be achieved if:-

the condensing surface absorbs little or none of the incoming radiation

Condensing water dissipates heat which must be removed rapidly from the

condensing surface by, for example, a second flow of water or air, or by

condensing at night.

6.2 Design Considerations:-

Different designs of solar still have emerged. The single effect solar still is a

Relatively simple device to construct and operate. However, the low productivity of the

Solar still triggered the initiatives to look for ways to improve its productivity and

Efficiency. These may be classified into passive and active methods. Passive methods

include the use of dye or charcoal to increase the solar absorbtivity of water, applying

good insulation, lowering the water depth in the basin to lower its thermal capacity,

ensuring vapor tightness, using black gravel and rubber, using floating perforated black

plate, and using reflective side walls. Active methods include the use of solar

collector or waste heat to heat the basin water, the use of internal] and external

condensers or applying vacuum inside the solar still to enhance the

evaporation/condensation processes, and cooling the glass cover to increase the

12

temperature difference between the glass and the water in the basin and hence

increases the rate of evaporation.

Single-basin stills have been much studied and their behavior is well understood.

The efficiency of solar stills which are well-constructed and maintained is about 50%

although typical efficiencies can be 25%. Daily output as a function of solar irradiation is

greatest in the early evening when the feed water is still hot but when outside

temperatures are falling. At very high air temperatures such as over 45ºC, the plate can

become too warm and condensation on it can become problematic, leading to loss of

efficiency.

6.3 Some problems with solar stills which would reduce their

efficiency include:-

Poor fitting and joints, which increase colder air flow from outside into the still

Cracking, breakage or scratches on glass, which reduce solar transmission or let

in air

Growth of algae and deposition of dust, bird droppings, etc. To avoid this the

stills need to be cleaned regularly every few days

Damage over time to the blackened absorbing surface.

Accumulation of salt on the bottom, which needs to be removed periodically

The saline water in the still is too deep, or dries out. The depth needs to be

maintained at around 20mm

6.4 Concepts for making a Good Solar still:-

The cover can be either glass or plastic. Glass is preferable to plastic because most

plastic degrades in the long term due to ultra violet light from sunlight and because it is

more difficult for water to condense onto it. Tempered low-iron glass is the best material

to use because it is highly transparent and not easily damaged (Scharl & Harrs, 1993).

However, if this is too expensive or unavailable, normal window glass can be used. This

has to be 4mm think or more to reduce breakages. Plastic (such as polyethylene) can

be used for short-term use.

Stills with a single sloping cover with the back made from an insulating material

do not suffer from a very low angle cover plate at the back reflecting sunlight and thus

reducing efficiency.

It is important for greater efficiency that the water condenses on the plate as a

film rather than as droplets, which tend to drop back into the saline water. For this

reason the plate is set at an angle of 10 to 20º. The condensate film is then likely to run

down the plate and into the run off channel.

13

Brick, sand concrete or waterproofed concrete can be used for the basin of a

long-life still if it is to be manufactured on-site, but for factory-manufactured stills,

prefabricated Ferro-concrete can be used. Moulding of stills from fibreglass was tried in

Botswana but in this case was more expensive than a brick still and more difficult to

insulate sufficiently, but has the advantage of the stills being transportable.

By placing a fan in the still it is possible to increase evaporation rates. However,

the increase is not large and there is also the extra cost and complication of including

and powering a fan in what is essentially quite a simple piece of equipment. Fan

assisted solar desalination would only really be useful if a particular level of output is

needed but the area occupied by the stills is restricted, as fan assistance can enable the

area occupied by a still to be reduced for a given output.

6.5 Design types and their performance:-

Single-basin stills have been much studied and their behavior is well

understood. Efficiencies of 25% are typical. Daily output as a function of solar

irradiation is greatest in the early evening when the feed water is still hot but

when outside temperatures are falling.

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 vapour provides energy to vaporize the feed water

above. Efficiency is therefore greater than for a single-basin still typically being

35% or more but the cost and complexity are correspondingly higher.

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.

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.

Hybrid designs - There are a number of ways in which solar stills can usefully

be combined with another function of technology. Three examples are given:

a) Rainwater collection:-By adding an external gutter, the still cover can be used for

rainwater collection to supplement the solar still output.

b) Greenhouse-solar still:-The roof of a greenhouse can be used as the cover of a

still.

14

c) Supplementary heating: - Waste heat from an engine or the condenser of a

refrigerator can be used as an additional energy input.

After going through the various existing designs of solar stills there are a few facts that

come to picture:

1. The efficiency of single stage still is around 25%.

2. The efficiency of multistage stills is higher than 35%.

3. Mostly people use three staged stills because for more stages the cost outweighs the

utility.

4. Most of the losses can be attributed to heat transfer losses.

5. Thermal losses are mostly in form of conduction and convection and very little by

radiation – owing to low temperatures. So we can assume radiative losses to be

negligible.

Also the cost of a solar still which produces reasonable amount of purified water is high.

The cost of water produced by the still is high. This fact attributes to almost negligible

penetration of solar stills in Indian villages. While persuing and pondering about the

ways to reduce costs the first factor that comes to mind is why not increase the

efficiency. But as we all know this is much easier said than done. After giving it a

considerable thought we came up with a design that can greatly improve the efficiency

of a solar water distillation system by minimizing thermal losses.

The equations governing the heat transfer rates are:-

a. Conduction

Q = - k A dT / dx

b. Convection

Q = h A ( Tsurface- Tambient )

Both the losses are greatly dependant on the area and temperature difference between

the medium i.e., water and ambient. Hence if we can reduce temperature of the whole

system we can reduce the heat loss and hence improve the efficiency.

But reducing operating temperature will come at the cost of lower rated of evaporation

and consequently lower rated of condensation leading to slower distillation. So now the

problem boils down to increasing the rated of evaporation at lower temperature.

15

(Mass loss rate) / (Unit area) = (Vapor Pressure - Ambient Partial Pressure) * sqrt (

(Molecular Weight)/(2*pi*R*T))

The Vapor Pressure of a liquid at a given temperature is a characteristic property of that

liquid. Vapor pressure of a liquid is intimately connected to boiling point.

Vapor Pressures are influenced by Temperature logarithmically and this relationship is

defined with the Clausius Clapyron Equation:

Log P2 / P1 = Delta H vaporization [ 1 / T1 - 1/T2] / 2.303 ( R)

where:

R = universal gas law constant = 8.31 J/mol-K = 8.31 X 10-3 Kj / mol-K

P1 and P2 = vapor pressure at T1 and T2

T1 and T2 = Kelvin Temperature at the initial state and final state

At 373K the pressure is 1 atm.

We all know that boiling takes place when the ambient temperature equals that of the

vapor pressure of the liquid. This means that we can increase the rate of evaporation by

reducing the pressure of the vessel. This will ensure higher rates of evaporation even at

low temperatures.

Constructing a solar water distiller using available utensils like plastic for casing,

aluminum for absorption of heat, glass and the thermocol for insulation. Got the

temperature of water up to 60 degrees and 100 ml of distilled water in 4 hours.

Surface area: .12 mt square (1 sq feet)

16

Fig.1.4 Components of Solar Still

Output: After 4 hours under the sun an output of 150 ml of pure distilled water

17

CHAPTER-7

CAPABILITIES

A solar still operates using the basic principles of evaporation and condensation. The

contaminated feed water goes into the still and the sun's rays penetrate a glass surface

causing the water to heat up through the greenhouse effect and subsequently

evaporate. When the water evaporates inside the still, it leaves all contaminants and

microbes behind in the basin. The evaporated and now purified water condenses on the

underside of the glass and runs into a collection trough and than into an enclosed

container. In this process the salts and microbes that were in the original feed water are

left behind. Additional water fed into the still flushes out concentrated waste from the

basin to avoid excessive salt build-up from the evaporated salts.

A solar still effectively eliminates all waterborne pathogens, salts, and heavy

metals. Solar still technologies bring immediate benefits to users by alleviating health

problems associated with water-borne diseases. For solar stills users, there is a also a

sense of satisfaction in having their own trusted and easy to use water treatment plant

on-site.

Solar still production is a function of solar energy (insolation) and ambient

temperature. Typical production efficiencies for single basin solar stills on the Border

are about 60 percent in the summer and 50 percent during the colder winter. Single

basin stills generally produce about 0.8 liters per sun hour per square meter.

Given the smaller product water output for a solar still, the technology calls for a

different approach to providing purified water in that it only purifies the limited amounts

of water that will be ingested by humans. Water used to flush the toilet, take a bath,

wash clothes, etc. does not need to meet the same high level of purity as water that is

ingested, and thus does not need to be distilled.

Solar stills have proven to be highly effective in cleaning up water supplies and in

providing safe drinking water. The effectiveness of distillation for producing safe drinking

water is well established and long recognized. Distillation is the only stand alone point-

of-use (POU) technology with NSF (National Sanitation Foundation) certification for

arsenic removal, under Standard 62. Solar distillation removes all salts and heavy

metals, as well as biological contaminants.

18

CHAPTER-8

USER EXPERIENCES

Surveys were conducted on user satisfaction with project participants receiving cost-

shared solar distillers . Users were nearly unanimous that owning a solar still was good

for them. Some owners prized the idea of using alternative, clean energy to achieve

their purposes, while at the same time leaving only a small “footprint” on the planet. All

were very enthused about the economic benefits of using a solar distiller. They found

that paying a relatively low price for a still was a favorable alternative to having to buy

water on a regular basis with no end in sight to this routine. Others valued the

independence and fascination they experienced from being involved in the production of

their own purified water. Most colonias residents often do not trust their local water

supply in those cases when there is one available (e.g., Columbus). While many have

noted a concern over local water supply color or odor, the overwhelming characteristic

that gains their attention is poor taste. There is a good deal of concern with taste, and

most of those interviewed noted that one of the reasons for wanting a water purification

system was to improve the taste of their local water supply. Since many of the local

water supplies are high in salts and minerals (e.g., iron or sulphur), they often have a

marginal or poor taste. The solar stills were considered useful by colonia residents to

improve drinking water taste.

Solar distillers were able to meet all of the drinking and cooking water needs of a

household. Not all of the households receiving solar stills through pilot projects had stills

optimally sized to meet all of their wintertime water production needs, but about 40

percent of the households were completely satisfied with their still water production.

All households had sufficient water during the high summertime production

period, and it was during the wintertime where some families had insufficient still water.

Generally, it appears that for most Border households about 0.5 m2 meter of

solar still is needed per person to meet potable water needs consistently throughout the

year. Those households with insufficient wintertime still water production typically had

0.35 m2 or less of still area per person. Survey results clearly indicate that only about a

third of colonias residents are willing or able to pay the full price of the solar still up front,

because most simply could not afford the higher up-front capital cost. However, interest

mounted greatly when the possibility of financing was mentioned. Thus, water districts

and others interested in providing potable water to Border colonias should consider

offering an option for still financing. To bolster interest, a clear, easy-to-follow

breakdown of cost payback should be provided. Prospective customers interest is

peaked when they realize that even at full price, a solar still can pay for itself in less

19

than two years as compared to purchasing bottled water. Some prospective customers

would be delighted to know that savings over a decade or more could be substantial

and amount to thousands of dollars.

Almost all of those surveyed were using their solar stills regularly, thus now

meeting most or all of their drinking water and cooking water supply needs via solar

distillation. Occasionally, still users had to supplement their still supply with store-bought

water, especially in the winter, when still production decreases to about half of

summertime production. Yet the need for purchasing bottled water from a store was

greatly mitigated in all cases. Solar still savings were approximately $150 - $200 a year

per household instead of purchasing bottled water.

Solar still technology has gradually improved over the past decade along the

Border. The greatest problem for the first generation stills designed by EPSEA in the

mid-1990‟s (an improvement on the original McCracken solar still) was that when they

dried out, the inner membrane silicone lining would outgas. This in turn deposited a fine

film on the underside of the glass, causing the water droplets to bead up and fall back

into the basin rather than trickle down the glass to the collection trough and thus still

water production drops dramatically (about 80% or more drop). The first still used a food

grade silicone and were made out of plywood and concrete siding. It was found that the

stills (3‟ x 8‟) were often producing far more water than the users needed, especially in

the summer. As time evolved, a second generation solar still was developed made out

of aluminum and smaller (3‟ x 6‟ and 3‟ x 3‟). The still was lighter, but expensive to build.

ECONOMICS :- Compared to purchasing comparable quantities of bottled water, the average return on investment on a solar still for a family is typically a couple of years. Factoring in the health costs of contaminated water, payback for a solar still can be immediate. Solar distillation is the cheapest way to clean water for a household and is quite economical as compared to reverse osmosis and electric distillation. A square meter for a single basin solar still costs about $400. Many families in the U.S. colonias often spend from $8 to $12 per week on bottled water. Likewise, in northern Mexico families often spend $3 - $5 per week on purified water. This represents an investment of anywhere from $150 to $600 per year for bottled water. Thus, simple payback on a solar still strictly compared to purchasing bottled water is typically within two to three years. The levelized energy cost of solar distilled water is about US$.03 per liter, assuming a ten year still lifetime. The first EPSEA stills have now been operating for a decade and are still going strong.

20

CHAPTER-9

COST ANALYSIS & MATERIALS

Materials:-

1. The side and bottom walls need to be insulated. This can be achieved by using

multilayered insulator. Glass wool will be sand-witched between two metallic plates.

This will ensure negligible heat loss to the surroundings.

2. The main frame is composed of steel owing to its corrosion resistance, low weight,

long life and easy cleanability.

3. The outside of the complete distiller is coated with carbon black to increase

absorption of radiation.

4. The cover on the top is made of tempered glass so that the birds can‟t see their

reflection and hence avoid nuisance.

Cost Analysis:-

Total cost of Aluminium box = Rs 2700

Cost of crushed hay and sawdust = Almost free

Cost of carbon black paint = Rs 200

Cost of tempered glass = Rs 800

Cost of Reflector = Rs. 500

Cost of insulation and sealing = Rs. 250

Cost of the hoisting mechanism and other auxiliaries = Rs 500

Cost of labor and machining = Rs 600

Cost of transportation = 800

Cost of other parts = 450

Cost of Report Writing: Rs. 700 (Typing, Editing, Color Printing, Hard Binding)

Net cost of the Project = Rs 7500

The per-liter cost of solar-distilled water can be calculated as follows:

(a) estimate the usable lifetime of the still;

(b) add up all the costs of construction, repair and maintenance (including labor)

over its lifetime; and

21

(c) divide that figure by the still's total expected lifetime output in liters.

Such a cost estimate is only approximate since there are large uncertainties in both the

lifetime and the yield estimates. Costs are usually considerably higher than current

water prices–which explains why solar backyard stills are not yet marketed widely in

India.

Assembling and manufacture:-

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 workshop using simple machines – lathe, drill, welding, milling etc.

The steps in the process of assembling are outlined as follows:

1. The outer box will be fabricated first. It will be made of double wall and will be filled

with glass wool to provide insulation.

2. The stages will be fabricated second the collector holes will be made at the time of

fabrication. Finally the stages will be assembled inside the outer covering.

3. The collector tubes are then made and attached to the lowermost stage.

4. The holes are provided for

a. Collecting distilled water

b. Transporting saline water

c. To attach the pump

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

atmosphere.

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, and 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. The cost of construction

components is listed below.

Box Structure/Insulation:

Extruded polystyrene foam has the best combination of light weight, rigidity, and

low cost. Foam boards of 2” thickness measuring 4‟x8‟ can be purchased for

22

approximately $20 from sources such as Univfoam and Foam-Control. Three boards

are required for the construction a solar still with base dimensions of 1x2.25 m, with a

20º inclined slope glazing. The maximum side height is 0.50 m, the minimum side height

is 0.14 m.

Glazing:

One solid piece of polycarbonate measuring 1x2.25m will be required for the

glazing. This can be purchased from sources such as Eplastics and USplastic for

around $70 for a 1/16” thick sheet measuring 4‟x8‟. The excess from this sheet will be

used to construct the catch for the distilled water.

Solar Radiation Absorber:

Another sheet of the same polycarbonate sheet used for the glazing can be

painted black and used as a solar heat absorber.

A picture of the passive solar still is shown below in Fig. 10, and dimensions are

shown in Fig. 11. The dimensions of the water refill port are arbitrary, or if tube filling is

chosen as the filling mode, it can be omitted. The actual catch for distill water is not

shown, but simply consists of a strip of polycarbonate fixed to the sloped glazing near

the bottom, to catch and direct the condensate out through the drip spout.

23

Figure 1.5 Passive Solar Still Design

Figure 1.6 Design Drawing of Solar Still, Dimensions in cm.

24

CHAPTER-10

BERKADS‟S APPLICATIONS

Berkads are a simple water supply option that is extensively used in Somalia

since the 1950‟s. A berkad is an artificial catchment that collects surface runoff that

results from intense rainfall episodes. They are usually lined with masonry and/or

concrete, and often include on one side a catch-pool that traps the coarse sediment.

Berkads are generally constructed in gently sloping areas, where low barriers are

sometimes present to direct runoff towards the catch-pool and then to the cistern.

During the intense rainfall episodes, berkads may fill up within several hours and last for

months throughout a dry period (Banks, 2008).They are the main water source for both

the human and livestock water needs. The studied berkads are on average 20 m long,

10 m wide and 3.5 m deep. Their volume thus is 700 m3.

Practical application

When implementing a solar still system on the berkads it is essential that the

design is as simple as possible but still effective. Keeping in mind the economic and

logistic aspects, affordable and local materials should be used whenever possible.

Nevertheless, to guarantee a good functioning of the system, some parts need to be

imported.

For Budunbuto, a single slope solar still is preferred above a double slope solar

still, as having only one slope equals to having only one internal gutter which can be

easily connected to the drink water storage tank. To increase the solar interception, the

solar still needs an equator facing top cover, with the length therefore lined on an east-

west axis (this might be problematic for already existing berkads, which might not be

orientated properly). The top cover should be set at an angle of 10º, which is considered

to be the most accepted angle for a single slope solar still at this latitude (Khalifa, 2010).

It should be made either out of a 3-4 mm thick glass or a ultra-violet resistant polyvinyl

chloride (PVC) sheet. As mentioned above, glass is the preferred material as it

increases the efficiency of the solar still. When choosing for a glass cover, it is important

that the structure of the still is build to carry the weight of the relatively heavy glass. The

sides of the still should be closed in order to make the still airtight. This could be done

by using the same material chosen for the top cover. At the inlet of the surface runoff

water, a one way door should be placed (Figure 6). This would allow the surface runoff

water to flow into the berkad during periods of rainfall, as the door would then open

under the weight of the water, but it would remain shut during dry periods.

25

The condensed water should be collected in a gutter fixed along the lower edge

of the cover. On the outer side of the cover a similar gutter should be placed for the

collection of the rainwater. Both gutters should be placed on a small angle to let the

water run towards the airtight pipes that connect it to the drinking water tank. Both

gutters should also be made of a material that is not affecting the properties of the water

and so should the airtight pipes be. Particular attention needs to be used when installing

the rain water collection gutter, as factors as the weight of the water in the gutter and

the wind effects should be considered. It is also advised to add a gutter screen (e.g. a

simple mesh with a fine pattern), as debris from the roof may collect in the gutter,

obstructing it.

The clean water storage tank should be placed in the immediate vicinity of the

berkad and should be properly closed, preventing any light from entering. It is advised

to place the drinking water tank in the ground (lower than the gutters), as in this way the

water would flow under gravity towards the tank.

A hand pump should be used for the extraction of the drinking water from the

tank, which should solely be used for human consumption. Another hand pump should

be used for the extraction of the water from the berkad, which should be used for animal

watering and other domestic use (washing, cooking, etc.).

Very important in the design of the system is that all the joints and fittings are

accurately isolated to prevent heat loss. For this reason, a one way valve could be

placed at connection point of the internal gutter and the pipe that goes to the drinking

water tank.

.

Discussion and recommendations

26

The results presented above indicate that the implementation of a solar still on (already

existing and new) berkads is a feasible measure for the improvement of the water

quantity and quality in the village Budunbuto. Above this, it is generally agreed that solar

stills are a good option in remote areas where the water demand does not exceed the

200 m3/day (Tiwari et al., 2003 and Fath, 1998). However, the approach used is very

theoretical and abstract, what inevitably may have lead to some inaccuracies:

- The evaporation loss has been calculated based mostly on remotely sensed data,

which is available only at a large scale for the studied location. This is a source of

inaccuracy within the results of the Penman open water evaporation equation. However,

it is important to notice that due to the availability of this data it is actually possible to

make estimates over an otherwise data scarce region.

- The actual water consumption rate, and thus the amount of berkads needed with a

solar still system, might differ from what has been estimated. This because the water

consumption rates and the number of inhabitants of Budunbuto are also an estimation

based on the little information that is available.

- The theoretical approach used to estimate the output from the solar still is very

abstract and might be inaccurate. On the other hand, this seems the most reasonable

approach to use when estimating solar still output theoretically, as it is possible to make

assumptions for the efficiency of the system and the remaining parameters are all

known.

- The solar still design as described above resulted to be the most suitable for

Budunbuto. However, as the approach used is very theoretical, it may not be the most

functional design in practice. Therefore it is recommended to test various simple solar

still designs during the pilot project. This could be done by constructing both single and

double slope solar stills, using plastic and glass top covers.

Although the above described inaccuracies are present, the information of this

report will provide a reliable guideline for the pilot project, during which the working of

the system will be tested. It is expected that the actual production rate of the solar still

will be within the range estimated and that the efficiency will most likely be around 15%.

However, to satisfy the water demand for animal watering and domestic use (about 35.5

m3/yr), more berkads are needed. These berkads obviously do not need a solar still

system, as the water does not need to be within the mineralogical and bacteriological

standard used for drinking water.

During the pilot phase of the project, it is advised to accurately measure both the

quantity and quality of the water produced by the still. The electrical conductivity, pH,

NO3- and the alkalinity of the water should directly be measured in the field. For the

analysis of the major cations and anions, it is advised to take 10 ml samples 13

27

filtered with a 0.45 μm membrane filter, which should then be sent to a water laboratory.

Also the bacteriological content of the water should be analysed, to make sure that the

bacteria and viruses are actually not present in the drinking water. These

measurements would certainly contribute to increase the knowledge regarding the

purification of contaminated water by using solar stills.

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 by the users to extract the water from the berkads as the hand

pumps should solely be used for that. The same holds for the drinking water tank which

should also never be opened. Another important point is that the maintenance of the

berkads is regularly carried out and that possible leaks are immediately detected and

repaired.Particular attention should be paid for the drinking water tank, which is

positioned in the ground, what makes it difficult to detect possible leaks.

The above described advisable design for the solar stills in Budunbuto is very

simple and (thus) not optimally efficient. It has been chosen to keep the design simple

because an increase in the efficiency and productivity of the still is usually coupled to an

increase in cost, which is an undesirable result. With this design, the solar stills

represent a low cost technology with low cost maintenance, which can be carried out by

unskilled manpower.

28

CHAPTER-11

Water Purifiers

History of drinking water filtration

During the 19th and 20th centuries, water filters for domestic water production

were generally divided into slow sand filters and rapid sand filters (also called

mechanical filters and American filters). While there were many small-scale water

filtration systems prior to 1800, Paisley, Scotland is generally acknowledged as the first

city to receive filtered water for an entire town. The Paisley filter began operation in

1804 and was an early type of slow sand filter. Throughout the 1800s, hundreds of slow

sand filters were constructed in the UK and on the European continent. An intermittent

slow sand filter was constructed and operated at Lawrence, Massachusetts in 1893 due

to continuing typhoid fever epidemics caused by sewage contamination of the water

supply.[1] The first continuously operating slow sand filter was designed by Allen Hazen

for the city of Albany, New York in 1897.[2] The most comprehensive history of water

filtration was published by Moses N. Baker in 1948 and reprinted in 1981.[1]

In the 1800s, mechanical filtration was an industrial process that depended on the

addition of aluminum sulfate prior to the filtration process. The filtration rate for

mechanical filtration was typically more than 60 times faster than slow sand filters, thus

requiring significantly less land area. The first modern mechanical filtration plant in the

U.S. was built at Little Falls, New Jersey for the East Jersey Water Company. George

W. Fuller designed and supervised the construction of the plant which went into

operation in 1902.[3] In 1924, John R. Baylis developed a fixed grid backwash assist

system which consisted of pipes with nozzles that injected jets of water into the filter

material during expansion.

Types of filters:-

Water treatment plant filters

Types of water filters media filters, screen filters, disk filters, slow sand filter beds, rapid

sand filters and cloth filters.

Point-of-use filters for home use include granular-activated carbon filters (GAC) used

for carbon filtering, metallic alloy filters, microporous ceramic filters, carbon block resin

(CBR), microfiltration and ultrafiltration membranes. Some filters use more than one

filtration method. An example of this is a multi-barrier system. Jug filters can be used for

29

small quantities of drinking water. Some kettles have built-in filters, primarily to reduce

limescale buildup.

Point-of-use microfiltration devices can be directly installed at water outlets (faucets,

showers) in order to protect users against Legionella spp., Pseudomonas spp.,

Nontuberculous mycobacteria, Escherichia coli and other potentially harmful water

pathogens by providing a barrier to them and/or minimizing patient exposure.

Certification of Water Filters:-

Three organizations are accredited by the American National Standards Institute, and

each one of them certify products using ANSI/NSF standards. Each ANSI/NSF standard

requires verification of contaminant reduction performance claims, an evaluation of the

unit, including its materials and structural integrity, and a review of the product labels

and sales literature. Each certifies that home water treatment units meet or exceed

ANSI/NSF and Environmental Protection Agency drinking water standards. ANSI/NSF

standards are issued in two different sets, one for health concerns (such as removal of

specific contaminants (Standard 53, Health Effects) and one for aesthetic concerns

(Aesthetic Effects, such as improving taste or appearance of water). Certification from

these organizations will specify one or both of these specific standards.

NSF International: The NSF Water treatment Device Certification Program requires

extensive product testing and unannounced audits of production facilities. The goal of

this program is to provide assurance to consumers that the water treatment devices

they are purchasing meet the design, material,and performance requirements of

national standards.

Underwriters Laboratories: Underwriters Laboratories, Inc., is an independent,

accredited testing and certification organization that certifies home water treatment units

which meet or exceed EPA and ANSI/NSF drinking water standards of contaminant

reduction, aesthetic concerns, structural integrity, and materials safety.

Water Quality Association:The Water Quality Association is a trade organization that

tests water treatment equipment, and awards its Gold Seal to systems that meet or

exceed ANSI/NSF standards for contaminant reduction performance, structural integrity,

and materials safety.

Filters that use reverse osmosis, those labeled as “absolute one micron filters,”

or those labeled as certified by an American National Standards Institute (ANSI)-

accredited organization to ANSI/NSF Standard 53 for “Cyst Removal” provide the

30

greatest assurance of removing Cryptosporidium. As with all filters, follow the

manufacturer‟s instructions for filter use and replacement.[6]

Portable water filters

Main article: Portable water purification

Water filters are used by hikers, by aid organizations during humanitarian

emergencies, and by the military. These filters are usually small, portable and light (1-2

pounds/0.5-1.0 kg or less), and usually filter water by working a mechanical hand pump,

although some use a siphon drip system to force water through while others are built

into water bottles. Dirty water is pumped via a screen-filtered flexible silicon tube

through a specialized filter, ending up in a container. These filters work to remove

bacteria, protozoa and microbial cysts that can cause disease. Filters may have fine

meshes that must be replaced or cleaned, and ceramic water filters must have their

outside abraded when they have become clogged with impurities.

These water filters should not be confused with devices or tablets that are water

purifiers, some of which remove or kill viruses such as hepatitis A and rotavirus.

Water polishing

The term water polishing can refer to any process that removes small (usually

microscopic) particulate material, or removes very low concentrations of dissolved

material from water. The process and its meaning vary from setting to setting: a

manufacturer of aquarium filters may claim that its filters perform water polishing by

capturing "micro particles" within nylon or polyester pads just as a chemical engineer

can use the term to refer to the removal of magnetic resins from a solution by passing

the solution over a bed of magnetic particulate.[7] In this sense, water polishing is simply

another term for whole house water filtration systems. Good materials to create a filter is

sand, gravel, activated carbon and window screens.

“The next world war-if ever-will not be over land, but on WATER. Globally more than

one billion people lack access to safe drinking water, nearly all of them in the

developing countries, including India”. Nearly one-third of the population worldwide live

in areas which are waterstressed. This figure is expected to increase further by a fold by

2025. Approximately 80% of diseases in India are caused by water borne micro

organisms. This is true in rural as well as urban India. However, awareness of health

risks linked to unsafe water is still very low among the rural population. The few who

treat water resort to boiling or use domestic candle filters. With more & more number

people are becoming conscious about contaminated drinking water; the demand for

water purifiers is rapidly rising especially in India. In the past few years, Indian water

31

purifier industry has seen an exponential growth of 22% CAGR (Compounded Annual

Growth Rate).

There are three types of Water Purifiers in the market:

1. Ultra Violet Based

2. Reverse Osmosis Based

3. Chemical Based

The UV segment constitutes more than 55% of the industry and has its key focus

area for water Purifier manufacturers because of higher margins it offer. The Indian

water purifier market has tremendous potential with a market size of approximately INR

1400 Cr ore. It is more evident from the fact that global majors such as Philips and

Hindustan Unilever have stepped in the area. In the years to come, we can expect to

see others entering the battle.

FEATURES OF A GOOD PURIFIER

It should retain natural quality of water

User friendly features.

Absolutely safe for drinking purpose as per WHO standards.

Long Life.

In-built storage tank

Avoids all contamination with last point purification.

Low Maintenance.

.

ABOUT THE PRODUCT

WATER PURIFIER – PUREIT

Pure-it is the world‟ s most advanced in-home water purifier. Pure-it, a breakthrough

offering of Hindustan Unilever (HUL), provides complete protection from all water-borne

diseases, unmatched convenience and affordability. Pure-it‟ s unique Germ kill Battery

technology kills all harmful viruses and bacteria and removes parasites and pesticide

impurities, giving you water that is “as safe as boiled water". It assures your family

100% protection from all water –borne diseases like jaundice, diarrhoea, typhoid and

cholera. Pure-it not only renders micro-biological safe water, but also makes the water

clear, odorless and good-tasting. Pure-it does not leave any residual chlorine in the

output water. The output water from Pure-it meets stringent criteria for microbiologically

safe drinking water from one of the toughest regulatory agencies in the USA, EPA

(Environmental Protection Agency). The performance of Pure-it has also been tested

32

by leading scientific and medical institutions in India and abroad. This patented

technological breakthrough has been developed by HUL. Pure-it runs with a unique,

Germ kill Battery Ki that typically lasts for 1500 liters of water. Consumer will get 4 liters

of water that is as safe as boiled water for just one rupee. Pure-it in-home purification

system uses a 4 stage purification process to deliver “as safe as boiled water” without

the use of electricity and pressurized tap water.

Pure-it purifies the input drinking water in four stages, namely;

1. MICRO-FIBER MESH- Removes visible dirt.

2. COMPACT CARBON TRAP- Removes remaining dirt, harmful parasites &

pesticide Impurities.

2. GERM KILL PROCESSOR– uses 'programmed chlorine release technology‟

and its Stored Germ kill process targets and kills harmful virus and bacteria.

4. POLISHER – Removes residual chlorine and all disinfectant by-products, giving

clearodorless and great tasting water.

5. BATTERY LIFE INDICATOR -Ensures total safety because when the germ kill

power is exhausted, the indicator turns red, warning you to replace the battery.

33

CHAPTER-12

Solar Panel

4.1 Solar Panel

A solar panel (also solar module, photovoltaic module or photovoltaic panel) is a

packaged connected assembly of photovoltaic cells. The solar panel can be used as a

component of a larger photovoltaic system to generate and supply electricity in

commercial and residential applications. Each panel is rated by its DC output power

under standard test conditions, and typically ranges from 100 to 320 watts. The

efficiency of a panel determines the area of a panel given the same rated output - an

8% efficient 230 watt panel will have twice the area of a 16% efficient 230 watt panel.

Because a single solar panel can produce only a limited amount of power, most

installations contain multiple panels. A photovoltaic system typically includes an array of

solar panels, an inverter, and sometimes a battery and or solar tracker and

interconnection wiring.

FIG. Solar Panel

34

4.2 Theory and construction

Solar panels use light energy (photons) from the sun to generate electricity through the

photovoltaic effect. The majority of modules use wafer-based crystalline silicon cells or

thin-film cells based on cadmium telluride or silicon. The structural (load carrying)

member of a module can either be the top layer or the back layer. Cells must also be

protected from mechanical damage and moisture. Most solar panels are rigid, but semi-

flexible ones are available, based on thin-film cells.

Electrical connections are made in series to achieve a desired output voltage

and/or in parallel to provide a desired current capability. The conducting wires that take

the current off the panels may contain silver, copper or other non-magnetic conductive

transition metals. The cells must be connected electrically to one another and to the rest

of the system. Externally, popular terrestrial usage photovoltaic panels use MC3 (older)

or MC4 connectors to facilitate easy weatherproof connections to the rest of the system.

Bypass diodes may be incorporated or used externally, in case of partial panel

shading, to maximize the output of panel sections still illuminated. The p-n junctions of

mono-crystalline silicon cells may have adequate reverse voltage characteristics to

prevent damaging panel section reverse current. Reverse currents could lead to

overheating of shaded cells. Solar cells become less efficient at higher temperatures

and installers try to provide good ventilation behind solar panels.

4.3 Efficiencies

Depending on construction, photovoltaic panels can produce electricity from a

range of frequencies of light, but usually cannot cover the entire solar range

(specifically, ultraviolet, infrared and low or diffused light). Hence much of the incident

sunlight energy is wasted by solar panels, and they can give far higher efficiencies if

illuminated with monochromatic light. Therefore, another design concept is to split the

light into different wavelength ranges and direct the beams onto different cells tuned to

those ranges.[2] This has been projected to be capable of raising efficiency by 50%.

Currently the best achieved sunlight conversion rate (solar panel efficiency) is

around 21% in commercial products, typically lower than the efficiencies of their cells in

isolation. The energy density of a solar panel is the efficiency described in terms of peak

power output per unit of surface area, commonly expressed in units of watts per square

foot (W/ft2). The most efficient mass-produced solar panels have energy density values

of greater than 13 W/ft2 (140 W/m2).

35

CHAPTER-13

Would a solar still suit our needs?

Human beings need 1 or 2 litres of water a day to live. The minimum requirement for

normal life in developing countries (which includes cooking, cleaning and washing

clothes) is 20 litres per day (in the industrialised world 200 to 400 litres per day is

typical). Yet some functions can be performed with salty water and a typical requirement

for distilled water is 5 litres per person per day. Therefore 2m² of still are needed for

each person served.

Solar stills should normally only be considered for removal of dissolved salts from

water. If there is a choice between brackish ground water or polluted surface water, it

will usually be cheaper to use a slow sand filter or other treatment device. If there is no

fresh water then the main alternatives are desalination, transportation and rainwater

collection. Unlike other techniques of desalination, solar stills are more attractive, the

smaller the required output. The initial capital cost of stills is roughly proportional to

capacity, whereas other methods have significant economies of scale. For the individual

household, therefore, the solar still is most economic.

For outputs of 1m³/day or more, reverse osmosis or electrodialysis should be

considered as an alternative to solar stills. Much will depend on the availability and price

of electrical power. Solar distillation Practical Action 5 For outputs of 200m³/day or

more, vapour compression or flash evaporation will normally be least cost. The latter

technology can have part of its energy requirement met by solar water heaters.

In many parts of the world, fresh water is transported from another region or location by

boat, train, truck or pipeline. The cost of water transported by vehicles is typically of the

same order of magnitude as that produced by solar stills. A pipeline may be less

expensive for very large quantities.

Rainwater collection is an even simpler technique than solar distillation in areas

where rain is not scarce, but requires a greater area and usually a larger storage tank. If

ready-made collection surfaces exist.

Distillation Purification Capabilities:-

Solar stills have proven to be highly effective in cleaning up water supplies to

provide safe drinking water. The effectiveness of distillation for producing safe drinking

water is well established and recognized. Most commercial stills and water purification

systems require electrical or other fossil-fueled power sources. Solar distillation

technology produces the same safe quality drinking water as other distillation

technologies; only the energy source is different: the sun.

36

CHAPTER-14

CONCLUSION

Distillation is a method where water is removed from the contaminations rather than to

remove contaminants from the water.Solar energy is a promising source to achieve

this.This is due to various advantages involved in solar distillation. The Solar distillation

involves zero maintenance cost and no energy costs as it involves only solar enegy

which is free of cost.

It was found from the experimental analysis that increasing the ambient

temperature from 32°C to 47°C will increase the productivity by approx 12 to 23%,

which shows that the system performed more distillation at higher ambient

temperatures. When inverted type absorber plate was used thermal efficiency of single

slope solar still was increased by 7 %.

It was observed that when the water depth increases from 0.01m to 0.03m the

productivity decreased by 5%.These results show that the water mass (water depth)

has an intense effect on the distillate output of the solar still system.

Solar still productivity can also increase by use of reflector by 3%. The use of the mirror

reflector will increase the temperature of the solar still basin; such an increase in the

temperature is because of the improvement in solar radiation concentration.

The solar radiation increase from 0 MJ/m2 /h to 6 MJ/m2 /h has increased the

productivity of the still by 15 to 32%. However the increase of the solar radiation

parameter will increase the solar energy absorbed by the basin liner.

The main disadvantage of this solar still is the low productivity or high capital cost

per unit output of distillate.This could be improved by a number of actions, e.g. injecting

black dye in the seawater,using internal and external mirror,using wick,reducing heat

conduction through basin walls and top cover or reusing the latent heat emitted from the

condensing vapour on the glass cover.Capital cost can be reduced by using different

designs and new materials for construction of solar stills.

37

References

1) BOOK-Renewable Energy Sources By G.D.Rai

2) http://en.wikipedia.org/wiki/Solar_still

3) http://www.solaqua.com/solstilbas.html

4) http://practicalaction.org/solar-distillation-1

5) http://www.motherearthnews.com/Renewable-Energy/1974-09-01/How-To-Build-and-Use-A-Solar-Still.aspx

6) http://www.desertusa.com/mag98/dec/stories/water.html