In house Project onFABRICATION AND PERFORMANCE

ANALYSIS OF SINGLE SLOPE SOLAR STILL

Submitted by:Anuj PatelAnurag Sethi Brajesh MaheshwariSaurav Goswami

Faculty guides:Mr. Shubham SharmaMs. Medhavi Sinha

Table of Contents

•Introduction•Requirements for solar distillation•Materials required for basin type solar still•Factors influencing the performance of solar distillation•Principle of solar distillation•Working•Experimental setup and procedure•Experimental observation•Result and conclusion

INTRODUCTION

• Today, 884 million people, lack access to safe water supplies, approximately one in eight people has no access to safe drinking water and every day approximately 24,000 children die before the age of five, by water born diseases, WHO (2009).

• India’s huge and growing population is putting a severe strain on all our natural resources. In India alone, an estimated 152 million people (14 percent of the total population) lack access to an improved water source, and nearly 730 million (67 percent of the population) lack access to improved sanitation facilities, WHO & UNICEF Joint Monitoring Programme (2006).

• Most water sources are contaminated by sewage and agricultural runoff. At present India has 16% of world’s population but only for 4% of it the fresh water supply is available.

Requirements for solar distillation

As long as the distiller is kept clean and working properly, the high quality of treated water will be very consistent regardless of the incoming water quality. The various favorable conditions for solar distillation are:-

• Availability of salty/ brackish water if other sources are fully exploited,• Total 3 m3/ day or less water requirement,• Availability of solar energy,• Rainfall below 0.5m/year,• High water transportation costs,• Competing technologies that require expensive and / or unreliable supply of

conventional fuel.

Materials required for basin type solar still

• The materials used for solar still should have the following characteristics:• Materials should have a long life under exposed conditions or be inexpensive enough

to be replaced upon degradation,• Material should be sturdy enough to resist wind damage and slight earth movements,• It should be nontoxic and not to emit vapour or instill an unpleasant taste to the water

under elevated temperatures,• It should be of a normal size and low weight so that it can be conveniently handled,

packed, packaged and transported by local medium.• It should be able to resist corrosion from saline water and distilled water.

Factors influencing the performance of solar distillation

The effects of design and climatic parameters on solar still performance are given below.

• Effects of design parameters• Integration of collectors with the solar still basin.• High absorptivity of basin liner and collector plate• Reducing thermal losses to ambient using good insulating materials• High ambient temperature• Low water depth• Large temperature difference between evaporative and condensing surfaces.• Low vapour leakage.

Effects of climatic parameters

• The higher convective heat loss from the glass surface can be achieved with the higher wind velocity and hence higher will be temperature difference between evaporative and condensing surface.

• The output of solar still increases with the increase in the intensity of solar radiation.

Principle of solar distillation

The solar radiation in the form of short electromagnetic waves passes through a clear glazing surface such as glass. The part of solar radiation absorbed and reflected by the glass and remaining (short wave radiation) is transferred into the still, where it is mostly absorbed by the blackened absorber liner and water. After absorbing the part of radiation, blackened surface of the basin liner radiates energy in the infra- red region (long wavelength), which is reflected back into the still by top glass cover again and again i.e. trapping the solar energy inside the still and producing the greenhouse effect.

Figure - 1: Schematic diagram of the operation of a one-stage solar still

By trapping energy the basin water heats up and begins to evaporate. Convection current is set up between the hot basin water and the cooler glass surface shown in figure-1. The pure (or mostly pure) vapour rises towards a cooler area (i.e. glass) and all impurities are left behind in the basin. The vapour condenses onto the inner surface of glazing and accumulates into thin sheets of water. The distillate then runs down into a collection trough due to combination of gravity and the tilt of glazing surface. The salts, sediments and metals that do not boil or evaporate and remain in the basin of distiller are to be removed occasionally. The distilled water is generally potable; the quality of the distillate is very high because all the salts, inorganic and organic components and microbes are left behind.

Working

• A solar still is made up of a two water troughs and a piece of glass running across the top of the water containers. Dirty water is placed in one of the troughs, while the other remains empty. The glass is placed across the top at an angle, angling directly down into the empty trough. The bottom of the trough containing the dirty water is usually painted black to help absorb the energy from the sun.

A solar still works on two scientific principles: evaporation and condensation. First, the water that needs to be purified is placed in the trough with the black bottom. The solar still is then allowed to sit in the sun, which allows the still to absorb the sun's short-wave energy. As the energy is absorbed, it starts to heat the water. As the temperature of the water rises, the liquid H20 is converted into steam and evaporates towards the glass ceiling, leaving anything that is not pure H20 in the trough below.

• The second scientific principle on which a solar still acts is condensation. After the water begins to evaporate, it hits the glass ceiling. The water slowly condenses on the glass, causing pure water droplets. Since the glass is angled down toward the second trough, the water droplets roll down and into the clean water trough. Because none of the minerals, bacteria or other substances are able to evaporate with the pure H20, the water droplets that end up in the second trough are simply purified, and are now safe for drinking and cooking.

Experimental setup and procedure

The schematic of the single slope passive solar still is shown in figure-2. It shows the various components of energy balance and thermal energy loss in a conventional single slope solar still

Figure-2 Schematic diagram of the single slope passive solar still

Parameters Single slope

Area of basin 0.606m2

Height of basin0.17m, Left

0.40m, Right

Area of condensing cover 0.46m2

Thickness of condensing cover 0.004m

Angle of condensing cover 150

Thickness of insulation 0.005m

Dimensions of single slope solar still

Experimental Observations

The experiments were carried out in the campus of Amity University, Noida to study the effect of water depths (0.01 m and 0.02 m) on the performance of single slope passive solar stills. The experimental observations for water depth 0.01 m for a typical day have been given

Efficiency

Result and Conclusion

• Distilled output from the solar still is higher at 13:00.• Solar insulation is highest at13:00.• By use of sprinkler and increased condensation area, the distilled output is

increased upto 20%.• By use of 2.0 cm water depth, proper utilization of the solar isolation as well as

distilled output is increased. So permissible water depth is 2.0 cm and it should be maintained constant by constant head tank.

• By use of FRP as a basin material, heat loss is low, so proper utilization of temperature is achieved and distilled output is increased.

• Ambient temperature as well as wind speed has also remarkable effect on performance of solar still because condensation rate is increased.

• Up to 35% productivity is increased in double slope solar still.

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