Improve the Efficiency of Solar Flat Plate Collector

IMPROVING THE EFFICIENCY OF TRADITIONAL FLAT PLATE

COLLECTOR BY USING CONVEX LENSES

A Project Report submitted in the partial fulfillment of the requirements for the award of

the degree of

BACHELOR OF TECHNOLOGY

IN

MECHANICAL (MANUFACTURING & MANAGEMENT)

ENGINEERING

By

L.TEJASWI (1210908128)

N.SRI SOURY (1210908138)

R.YASHWANTH KUMAR (1210908152)

V.V.N.SIDDARTHA (1210908162)

Under the esteemed guidance of

SRI SSV RAMANA RAO

Associate professor

DEPARTMENT OF INDUSTRIAL PRODUCTION ENGINEERING

GITAM INSTITUTE OF TECHNOLOGY

GITAM UNIVERSITY

VISAKHAPATNAM -530045



GITAM UNIVERSITY

VISAKHAPATNAM-530045

CERTIFICATE This is to certify that this project work entitled “IMPROVING THE EFFICIENCY OF A TRADITIONAL FLAT PLATE COLLECTOR BY USING CONVEX LENSES” is the bonafide work submitted by L.TEJASWI, N.SRI SOURY, R.YASHWANTH KUMAR, and V.V.N.SIDDARTHA under my guidance in partial fulfillment of requirements for the award of Bachelor’s Degree in “MECHANICAL (MANUFACTURING & MANAGEMENT)

ENGINEERING”, GITAM institute of technology, Visakhapatnam during the academic year

2011-2012. Project Guide Head of the Department Sri S.S.V Ramana Rao Dr. B Surender Babu Associate Professor Professor Department of Industrial Production Engg Department of Industrial Production Engg Gitam Institute of Technology Gitam Institute of Technology Visakhapatnam Visakhapatnam

EVALUATION SHEET

Title of the project : IMPROVING THE EFFICIENCY OF A FLAT

PLATE COLLECTOR BY USING CONVEX

LENSES.

Year of submission : 2012

Name of the degree : B.TECH

Date of examination : 1ST

MAY, 2012

Student’s Names : 1. L.TEJASWI (1210908128)

2. N.SRI SOURY (1210908138)

3. R. YASWANTH KUMAR (1210908152)

4. V.V.N SIDDARTHA (1210908162)

Name of the guide : SRI SSV RAMANA RAO (Associate Professor)

Result : Approved/Rejected

Internal Examiner External Examiner

(Name of the Internal Examiner) (Name of the External Examiner)



GITAM UNIVERSITY

VISAKHAPATNAM-530045

DECLARATION

We, hereby declare that we have developed a project entitled “IMPROVING THE EFFICIENCY OF A TRADITIONAL FLAT PLATE COLLECTOR BY USING

CONVEX LENS ” under the esteemed guidance of SRI SSV RAMANA RAO and

submitted to the Department of Industrial Production Engineering, GITAM INSTITUTE

OF TECHNOLOGY, for the partial fulfillment of the requirement for the award of

B.TECH Degree.

L.TEJASWI (1210908128)

N.SRI SOURY (1210908138)



ACKNOWLEDGEMENTS

All the members of the team who carried out the project entitled “IMPROVING THE EFFICIENCY OF A TRADITIONAL FLAT PLATE COLLECTOR BY USING CONVEX LENSES” earnestly express their deep gratitude to Dr. B.Surender Babu,

Head of the Department, Industrial Production Engineering and Sri SSV Ramana Rao,

Associate Professor, Department of Industrial Production Engineering for their unstinting

support and inspiring guidance in the completion of this project.

We are also thankful to the technical staff of Metrology lab; Heat transfer lab and CAD Lab

for helping us carry out our experimentation.

We express our thanks to all the teaching and non-teaching staff members of the

department for their direct or indirect support to carry out this project work.

L.TEJASWI (1210908128)

N.SRI SOURY (1210908138)



ABSTRACT

The principle objective of this paper is to demonstrate an innovative method which

maximizes the efficiency of a traditional solar flat plate collector with the help of convex

lenses and the principle of convergence; with the aid of the focal points formed. A focal

point accumulates a concentrated amount of the sun’s heat or any light source into a single

spot, if utilized can enhance the performance of a device, consuming it. In order to achieve

optimum output, the main challenge was to find alternatives to incorporate multiple

numbers of convex lenses of various diameters so that maximum number of focal points

could be achieved.

Lenses of different diameters should be taken into consideration as they have a direct

relation to the intensity of the focal point formed as lenses of shorter radius can only form

a focal point of less intensity and vice versa. In addition to the size of the lens, we found

out that the arrangement of the convex lens also plays a significant role to the experiment

as it has a direct impact on the number of focal points that can be formed at a single

instance of time. The other parameters

which are to be considered are the angle of inclination with which the glass plate is to be

placed, the climatic conditions on the particular day, insulation problems, cost analysis,

latitudes &longitudes of that particular place and the percentage utilization of area. Results

of this study showed that, if properly insulated, convex lenses can double the temperatures

obtained without the usage of lens in the same time frame.

CONTENTS

CHAPTER No. CHAPTER PAGE No.

1 INTRODUCTION 1

1.1) Renewable energy resources 2

1.2) Solar energy 2

1.3) Solar water heating 2

1.4) Working of flat plate collector 5

1.5) Principle of FPC 5

1.6) System sizing 6

1.7) Convex lenses 7

2 LITERATURE REVIEW 10

2.1) Introduction 11

2.2) Case study in Gitam University 12

2.3) Savings sheet of FPC, cost and maintenance 12

3 EXPERIMENTATION 16

3.1) Project details 17

3.2) Experiment no 1 17

3.3)Experiment no 2 19

3.4) Experiment no 3 23

3.5) Experiment no 4

26

3.6) Percentage utilization of area 38

3.7) Key parameters

42

3.8) Cost analysis 44

4 RESULTS AND DISCUSSION 45

5 SUMMARY 47

6 REFERRENCES 48

LIST OF FIGURES

FIGURE NO. FIGURE PAGE NO.

Figure no. 1 Anatomy of FPC 4

Figure no. 2 Cross sectional view of FPC 4

Figure no. 3 FPC 4

Figure no. 4-7 FPC installed at various places 7

Figure no. 8-9 Anatomy of convex lens 8

Figure no. 9.1 Types of convex lenses 9

Figure no. 10 3-D representation of the setup 28

Figure no. 11 Arrangement of lens 30

Figure no. 12 Complete setup 32

Figure no. 13 System diagram 37

Figure no. 14 Maximum utilization of area 38

Figure no. 15-16 Optimal arrangement of setup 39

Figure no. 19 Commercial solar thermal system 41

LIST OF TABLES

TABLE NO. TABLE PAGE NO.

1 Water consumption rate by persons per day 6

2 Temperature reading of lens A 27

3 Temperature reading of lens B 29

4 Temperature reading of lens c 31

5 Shadow temperature vs focal temperature 34

vs surface temperature

6 Temperature obtained with lens and without lens 36

7 Insolation intensity levels over a period of 1 yr 43

at different regions

LIST OF GRAPHS

GRAPH NO. GRAPH PAGE NO.

1 Lens A vs Lens B vs Lens C 33

2 Shadow temp vs Focal point vs Surface 35

3 Without lens vs with lens 37

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CHAPTER- 1

INTRODUCTION

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1.1) RENEWABLE ENERGY RESOURCES

Renewable energy is energy which comes from natural resources such as sunlight, wind,

rain, tides, and geothermal heat, which are renewable (naturally replenished). About 16%

of global final energy consumption comes from renewable, with 10% coming from

traditional biomass, which is mainly used for heating, and 3.4% from hydroelectricity.

New renewables (small hydro, modern biomass, wind, solar, geothermal, and biofuels)

accounted for another 3% and are growing very rapidly.

1.2) SOLAR ENERGY

Solar energy technologies include solar heating, solar photovoltaic, solar thermal

electricity and solar architecture, which can make considerable contributions to solving

some of the most urgent problems the world now faces. The International Energy Agency

projected that solar power could provide "a third of the global final energy demand after

2060, while CO2 emissions would be reduced to very low levels."

The amount of solar energy reaching the surface of the planet is so vast that in one year it

is about twice as much as will ever be obtained from all of the Earth's non-renewable

resources of coal, oil, natural gas, and mined uranium combined. One exa joule (EJ) is

equal to 1018 joules.

1.3) SOLAR WATER HEATING

Hot water heated by the sun is used in many ways. While perhaps best known in a

residential setting to provide domestic hot water, solar hot water also has industrial

applications, e.g. to generate electricity. Designs suitable for hot climates can be much

simpler and cheaper, and can be considered an appropriate technology for these places.

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The global solar thermal market is dominated by China, Europe, Japan and India. In order

to heat water using solar energy, a collector, often fastened to a roof or a wall facing the

sun, heats working fluid that is either pumped (active system) or driven by natural

convection (passive system) through it. The collector could be made of a simple glass-

topped insulated box with a flat solar absorber made of sheet metal, attached to copper

pipes and dark-colored, or a set of metal tubes surrounded by an evacuated (near vacuum)

glass cylinder. In industrial cases a parabolic mirror can concentrate sunlight on the tube.

Heat is stored in a hot water storage tank. The volume of this tank needs to be larger with

solar heating systems in order to allow for bad weather, and because the optimum final

temperature for the solar collector is lower than a typical immersion or combustion

heater. The heat transfer fluid (HTF) for the absorber may be the hot water from the tank,

but more commonly (at least in active systems) is a separate loop of fluid containing anti-

freeze and a corrosion inhibitor which delivers heat to the tank through a heat

exchanger (commonly a coil of copper tubing within the tank). Another lower-

maintenance concept is the 'drain-back': no anti-freeze is required; instead, all the piping

is sloped to cause water to drain back to the tank. The tank is not pressurized and is open

to atmospheric pressure. As soon as the pump shuts off, flow reverses and the pipes are

empty before freezing could occur.

FLAT PLATE SOLAR COLLECTORS

A typical flat-plate collector is a metal box with a glass or plastic cover (called glazing)

on top and a dark-colored absorber plate on the bottom. The sides and bottom of the

collector are usually insulated to minimize heat loss. The heat is transferred to liquid

passing through pipes attached to the absorber plate. Absorber plates are commonly

painted with "selective coatings," which absorb and retain heat better than ordinary black

paint. Absorber plates are usually made of metal—typically copper or aluminum—

because the metal is a good heat conductor. Copper is more expensive, but is a better

conductor and less prone to corrosion than aluminum.

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Figure 1

Figure 2

Figure 3

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1.4) WORKING OF A FLAT PLATE COLLECTOR

The radiant energy is harnessed through the copper absorbers in the Flat Plate Collectors

which are capped by 4 mm thick, toughened, transparent glass which allows maximum

transmission and low emission. All of the water movements in the copper tubes of flat

plate collectors result from naturally occurring convection currents, the same currents

operational in gas/electrical geysers/boilers.

Cold water is heavier and naturally migrates to the bottom of the unit, i.e. the copper

tubes. As the water heats-up, it becomes lighter and naturally migrates upwards to the

heavily insulated hot water storage Tank. These movements are continuous in response to

water temperature differentials within the system.

1.5) PRINCIPLE OF FLAT PLATE COLLECTOR

The Solar water heater works on a principle called “Thermo syphon”[natural circulation]

Due to density difference between the cold & hot water, the lighter hot water flows up

into the Solar tank while the heavier cold water enters it.

Solar radiation incident on the collector panels heats the copper absorber present inside it.

This heat transferred to the water flowing inside the absorber & becomes less dense than

the Cold water present in the solar water tank. Hot water starts rising and settles at the top

of the solar tank. Simultaneously cold water from the solar tank descends into the

collector’s Absorber tubes, gets heated up and the cycle repeats till all the water in the

solar tank is heated up. Since the solar tank is insulated, the hot water inside retains heat

till next day.

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Life of the system and maintenance issues:

Generally, the system’s life is estimated to be 20 years. Very minimal maintenance is

required. Except cleaning of glass periodically, changing of rubber parts once in 5 years

& flushing of the collectors and tank, there is no other maintenance needed.

1.6) SYSTEM SIZING

For domestic models, the capacity is calculated @ 25 liters per person, per day.

Hence, a family of 4 members needs a 100 LPD [liters per day]. The capacity will

increase proportionately as the number of people increases.

Table-1 : Water consumption rate by persons per day

4 members 5-6

members

7-8

members

9-10

members

11-12

members

13-14

members

15-

20members

100 LPD 125 LPD 200 LPD 250 LPD 300 LPD 375 LPD 500 LPD

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Figures showing installed Flat Plate Collectors

Figure no.4, Figure no.5.

Figure no.6, Figure no.7

1.7) CONVEX LENSES

A lens is an optical device with perfect or approximate axial

symmetry which transmits and refracts light, converges or diverges the beam. A lens which

can focus a beam into a single point is said to be a convex lens.

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The Anatomy of a Lens

If a piece of glass or other transparent material takes on the appropriate shape, it is

possible that parallel incident rays would either converge to a point or appear to be

diverging from a point. A piece of glass that has such a shape is referred to as a lens.

Figure no.8

Types of lenses

There are a variety of types of lenses. Lenses differ from one another in terms of their

shape and the materials from which they are made. Our focus will be upon lenses that are

symmetrical across their horizontal axis - known as the principal axis. In this unit, we

will categorize lenses as converging lenses and diverging lenses. A converging lens is a

lens that converges rays of light that are traveling parallel to its principal axis.

Converging lenses can be identified by their shape; they are relatively thick across their

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middle and thin at their upper and lower edges. A diverging lens is a lens that diverges

rays of light that are traveling parallel to its principal axis.

Figure no.9

Figure no.9.1

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CHAPTER- 2

LITERATURE REVIEW

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2.1) INTRODUCTION

In the solar-energy industry great emphasis has been placed on the development of

"passive" solar energy systems, which involve the integration of several subsystems: Flat

Plate collectors, heat-storage containers, fluid transport and distribution systems, and

control systems. The major component unique to passive systems is the Flat plate

collector. This device absorbs the incoming solar radiation, converting it into heat at the

absorbing surface, and transfers this heat to a fluid (water) flowing through the Flat plate

collector. The warmed fluid carries the heat either directly to the hot water or to a storage

subsystem from which can be drawn for use at night and on cloudy days. Since 1900, a

large number of solar collector designs have been shown to be functional; these have

fallen into two general classes: Experiment Analysis of Flat Plate Collector and

Comparison of Performance with Tracking Collector

• Flat plate collectors: in which the absorbing surface is approximately as large as the

overall collector area that intercepts the sun's rays.

• Concentrating collectors: in which large areas of mirrors or lenses focus the Sunlight

onto a smaller absorber.

Since of energy crisis, there has been effort to develop new energy sources as a way to

solve energy problem and at of there, solar energy has received special attention. The

resource why solar energy has not been utilized as energy source for generating large

power is considered as follows. The energy generated depends too much on time and

seams to supply a stable power needed for a secondary energy source. It will require and

enormous cost of equipment to effectively take energy at of such a moving energy source

as the sun, and the energy cost obtained from the sun is comparatively high at present.

However, as a result of increase of prices of fossil and nuclear fuels, a feasibility of solar

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energy as a new energy source can be increased, when a very high energy conversion

efficiency and a reduction of cost of equipment is obtained, due above reasons, solar

energy is one of the best possible and easily available energy. For the betterment of

mankind, now a day for various applications with solar energy are in use still. Lot of

research work is going on to use the available solar energy to maximum extent. One such

area is tracking mechanism to obtain maximum energy. Just by keeping the collector

fixed; it is not possible to get maximum energy from sun. It is possible to obtain the

maximum energy only when it is rotated along the sun direction. In this context, tracking

plays an important role. Tracking is desirable for orienting a solar device towards the sun

there by collecting maximum solar energy and improving efficiency. This advantageous

to water heater collector applications and this mechanism has been found more

advantages than fixed flat plate collector.

2.2) CASE STUDY ON 2ND MARCH, 2012 AT GITAM UNIVERSITY

Gitam University located in Visakhapatnam is a major customer of flat plate collectors.

This university is encouraging the use of renewable energy resources in the form of FPC.

Nearly all the hostels present inside the campus are equipped with flat plate collectors.

On an average there are nearly up to 8 FPCs per hostel. During the winter season when it

is very cold the FPC is given electrical supply such that it acts as a water geyser. The

FPCs located in Gitam University is manufactured by Greentek India Pvt Ltd, largest

manufacturers of solar flat plate collectors in India.

2.3) SAVINGS SHEET OF A FLAT PLATE COLLECTOR

Type or model GTR 125 L

Maximum working pressure 245 kpa

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System capacity 125 LPD (litres per day)

System temperature 80 °c

Ambient temperature 30°c

Thermal output = mass ×specific heat× rise in temperature

= 125 × (80-30)

= 6250 kcal/day

Total energy saved per year (assuming 300 days of sunshine) =1875000 kcal/year

Specifications

Weight of the 125 L solar heater = 150 to 175 kgs

Area required or space = 2.5 sq m

Height from the floor level = 1.5 m

The thickness of the toughened, transparent glass = 4 mm

Absorber coating black

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Number of risers = 9 nos. each extra riser increases the efficiency of the collector by 9 to

12 %

Pitch of the riser tubes = 5-15 mm

Riser tube diameter=12.5 mm

Number of header tubes= 2 nos

Method of bonding riser to header brazing, soldering

Header tube diameter = 25 mm

Material used copper

Liquid flowing in the system water

Collector box and sealing aluminum is used for the collector box and for sealing a

silicon sealant is used for waterproof performance.

Cost and maintenance of the system

The cost of 125 LPD system is very economical will cost Rs 20,000/- plus VAT @4%,which is equivalent to the cost of 4 electrical geysers.

The system’s life is estimated to be 20 years. Very minimal maintenance is required.Except cleaning of glass periodically, changing of rubber parts once in 5 years & flushingof the collectors and tank, there is no other maintenance needed.

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There are nearly 16-20 and many more flat plate collectors in Gitam University. The total

amount of energy saved per day = energy saved per day x no of flat plate collectors

= 6250 kcal/day x 20= 125000 kcal /day

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CHAPTER- 3

EXPERIMENTION

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Project details

Aim To add supplementary features to a traditional flat plate collector by the use of

convex lenses of different diameters. To arrange the convex lenses on the glass plate of

various diameters in such a way that maximum number of focal points are obtained thus

utilizing maximum amount of heat.

The most difficult task is to arrange or allocate the different lenses on the glass plate so as

to obtain the maximum number of focal points.


The following experiment was conducted with improper insulation.

A small experiment conducted in Gitam university, Industrial Engineering building on

2/02/2012 at 1 45 pm generated the following results

The total no of specimens used 3 convex lenses, a glass plate.

Specifications of the glass plate

Material type plane glass

Thickness of the glass plate 4 mm

Dimensions of the glass piece 26.5×38 sq.cm

Cost of the glass piece Rupees 50/-

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Specifications of the convex lens

Diameter of lens A= 5.5 cm, Lens B= 5.7 cm, Lens C=10 cm

Power of lens A= 10, Lens B=6, Lens C=5.5(approx.)

Focal length of lens A=10 cm, Lens B=16.6 cm, Lens C= 18 cm

Cost of the lens A=B= rupee 100/- per lens

Calculation or determining the angle of the glass plate with respect to the horizontal

floor

The height of the glass plate, H= 15.9 cm, H 1 = 5 cm

The length of the setup (glass piece inclined position), L= 33.2 cm

By using trigonometry ratios,

On application the angle is measured to be 25.6 °

At = 25.6 °

The minimum no of focal points that can be formed using 3 lenses of different diameters

are 13

The total number of focal points obtained by using lens A=7

The total number of focal points obtained by using lens B=3

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The total number of focal points obtained by using lens C=3

The temperature recorded at 145 pm of the focal points varies from 45°c to 55°c

depending upon the 3 lenses with an average temperature of 49 °c.

The room temperature recorded on 2/2/2012 is 29°c.



AIM To obtain as many number of focal points using 3 lenses of different diameters

performed at Autonagar on 9/3/2012.

The total no of specimens used 3 convex lenses, a glass plate.

Specifications of the glass plate

Material type plane glass

Thickness of the glass plate 4 mm

Dimensions of the glass piece 30.5×20 sq.cm

Cost of the glass piece Rupees 50/-

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Specifications of the convex lens

Diameter of lens A= 5.5 cm, Lens B= 5.7 cm, Lens C=10 cm

Power of lens A= 10, Lens B=6, Lens C=5.5(approx.)

Focal length of lens A=10 cm, Lens B=16.6 cm, Lens C= 18 cm

Cost of the lens A=B= rupee 100/- per lens

Readings taken at 1130 am

The room temperature =32°c

The height of the glass plate at one end provided with supports and placed inclined with

respect to the floor, H1 =18.3 cm

The height of the glass plate at the other end, H2=4.1 cm

The entire length of the glass plate place at an inclined position to the floor=37.7cm

By applying the trigonometry ratios,

We get = 25.89°

The minimum number of focal points obtained is 8

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The total number of focal points obtained by using lens A=3

The total number of focal points obtained by using lens B=3

The total number of focal points obtained by using lens C=2

Temperature obtained by using the lens A, t1= 55 °c

Temperature obtained by using the lens B, t2= 58°c

Temperature obtained by using the lens C, t3= 65°c

Readings taken at 1240 pm

T1= 40 °c (shadow)

T2=41°c

T3=50°c


T1=40°c

T2=41°c

T3=43°c


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T1=36°c (shadow)

T2=38°c (shadow)

T3=38°c (shadow)

After 10 minutes all the focal points disappeared so the glass plate, the entire setup was

shifted about 180° in the anti-clockwise direction from the original position.

The new position of the glass plate is kept at an angle =36.1°


T1=42°c

T2=50°c

T3=40°c


T1=40°c

T2=39°c

T3=38°c


T1=38°c (shadow)

T2=39°c (shadow)

T3=37°c (shadow)

At exactly 455 pm there were no focal points obtained.

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Weather was very much sunny today

The room temperature recorded today = 32°c

The highest temperature to be obtained today =65°c at 1140 am with =25.89°

The lowest temperature obtained today=36°c at 240 pm

The average temperature obtained today=43.4°c

The average ambient or room temperature today=32°c

Considering the above obtained temperatures, a clear sunny day, without any insulating

material and a tank capacity of 100 litres

The total amount of energy that can be saved = mass× rise in temperature

= (43.4-32) ×100

= 1140 kcal/ day

3.4) EXPERIMENT NO 3


AIM To obtain as many number of focal points using 3 lenses of different diameters

performed at Autonagar on 11/3/2012.

All the same tools and specimens were used in this experiment as in the case of

experiment 2

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At 9 00 am the climate was cloudy




Applying trigonometry ratios, we get =17.2/36.4

=25.29°

The glass plate was placed at an angel = 25.29° with respect to the horizontal.

READINGS TAKEN AT 1000 AM

The room temperature recorded today = 30 °c

T1= 48°c

T2=44°c

T3=40°c (shadow + blurred focal point)

READINGS TAKEN AT 1100 AM

T1=40 °c (shadow)

T2=52°c

T3=40°c

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READINGS TAKEN AT 1200 PM

T1=38°c (no focal point complete shadow)|

T2=60°c

T3=42°c


T1=40°c (shadow)

T2=44°c

T3=42°c


T1=34°c (shadow)

T2=38c° (shadow)

T3=36c° (shadow)

After a few minutes no focal points were obtained so the entire glass plate shifted to 180°

from the original position in anti-clockwise direction

The new inclination of the entire set up was now calculated to be 33.53° (height =16.9

cm & length =25.5cm)

At = 33.53°


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T1=60°c

T2=46°c

T3=44°c


The following experiment was conducted with proper insulation.

Aim to obtain as many numbers of focal points by using 3 different types of convex

lenses.

Materials and tools required

Insulation material bricks, glass, wood chips and silky foam.

Temperature recording devices thermocouple and digital reading set up box,

thermometers

Absorber plate aluminum or tin sheet

Glazing or tar sheet and dull black paint.

The room temperature recorded on the present day at 8 am T ambient = 32°c

Glass plate of the dimensions = 38.2cm x 26. 5cm

Area of the lens A= /4 x 5x5= 117.75 cm sq

Area of the lens B=/4x5.5x5.5=142.56 cm sq

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Table no 2: Temperature reading of lens A at 1130 am on 28/4/12

Time taken to achieve the temperaturewith respect to the room temperature

(minutes)

The observed temperature

(Degrees centigrade)10 60°c

20 75°c

33 80°c

40 85°c

50 90°c

70 95°c

100 100°c

120 110°c

For the next 10 minutes up to 1140 am the temperature remained constant at 110°c. At

exactly 12 00pm the temperature reading started to fall down to 108°c , then gradually

decreased to 55°c at 1 30 pm and finally no focal point or shadow was formed at 2 10

pm.

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3-D representation of experimental setup

Figure no.10

In the above figure the yellow color represents the use of insulating material silk wool.

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Table no 3: Temperature reading of lens B at 1130 am on 28/4/12


(minutes)


(Degrees centigrade)

10 40°c

20 45°c

33 48°c

40 55°c

50 55°c

70 60°c

100 65°c

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Figure no.11

Different diameters of lens arranged on the glass plate as show above.

The temperature of lens B varied between 60-70°c for a span of nearly 2 hours from

1130 am to 130 pm , then gradually decreased to 55 °c and maintained a constant

temperature of 48 °c . Finally at 330 pm no focal points or shadows were formed by lens

B.

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Table no 4: Temperature reading of lens C at 1130 am on 28/4/12


(minutes)


(Degrees centigrade)

10 60°c

20 70°c

33 75°c

40 80°c

50 85°c

70 90°c

100 105°c

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Figure no.12

The temperature reading of lens C decreased from 105 gradually after 12 30 pm to 60 °c

and from 1230 pm to 130pm temperature varied between 60-65°c. After changing the

position of the glass plate at 145 pm lens C recorded a very high temperature of 125 °c

and then gradually decreased to 56 °c at 345 pm. By 400 pm no focal points or shadows

were obtained and the surface temperature was obtained to be 43 °c.

The angle of inclination for the particular set up,



The height of the glass plate at the other end, H2=0 cm


By applying the trigonometry ratios,

We get = 31.21°

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Graph no.1 Temperature vs time graphs for different lenses.

After obtaining all the values of the three respective lenses A, B, C

A graph was plotted with the time (minutes) on the X-axis and the temperatures on the y-

axis. From the graph we can notice a gradual increase in the temperature of all the three

lenses and at certain time the temperatures remain constant and then gradually decrease

coming to a halt.

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Table no 5: Shadow temperature vs focal point temperaturevs surfacetemperature

for lens C (1130 am to 1 30 pm)

Time in minutes Shadow temp in °c Focal point temp in °c Surface temp

°c10 38°c 50°c 33

20 42°c 60°c 35

30 45°c 65°c 39

40 45°c 75°c 40

50 45°c 80°c 40

60 50°c 90°c 42

80 55°c 105°c 45

With the above details a graph is plotted with time in minutes on x-axis and temperaturesin °c on y-axis.

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Graph no.2 Temperature vs time at the shadow region, focal point and at surface.

From the above graph it is clearly observed that the focal point temperature is always

greater than the shadow temperature during all instances. The focal point temperature

maintain constant gap with the surface temperature as show in the graph. There is a huge

gap between the focal point temperature and the surface, shadow temperature. The x-axis

is time in minutes and the y-axis temperature in °c.

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Table no 6: Temperatures obtained with using lens and without using

lens (lens A) 1130 am

Time in minutes Temperature obtainedwithout lens

Temperature obtainedwith lens

10 33°c 45°c

20 35°c 55°c

30 38°c 65°c

40 55°c 105°c

50 50°c 90°c

60 45°c 80°c

70 41°c 65°c

80 39°c 60°c

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Graph no.3 Temperature vs time with lens and without lens.

From graph no 3 we can clearly observe that the temperatures recorded while using no

lens is almost half of the temperatures recorded while implementing the lenses.

System diagram Figure no.13

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3.6) PERCENTAGE UTILISATION OF AREA

The dimensions of the glass plate = 38.2cm x 26.5cm

The area of the glass piece= 1012.3 cm square

Area of the lens A= /4 x 5x5= 19.625 cm square

Area of the lens B=/4x5.5x5.5=23.76 cm square

Area of the lens C=/4x10x10=78.5 cm square

Total number of lenses that can be arranged on the glass plate=20

The number of focal points formed by lens A= 10

The number of focal points formed by lens B=8

The number of focal points formed by lens C= 2

Figure no.14

The Total area consumed by lens A= 10x19.625 =196.25 cm square

The total area consumed by lens B= 8x23.76=190.08 cm square

The total area consumed by lens C= 2x78.5=157 cm square

Percentage utilization of area= total area of the 3 lenses/total area of the glass plate

= (190.08+196.25+157)/1012.3= 53.67%

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The arrangement of the project setup

Figure no.15 The starting step is finding the axis for the lens

Figure no.16

Arrangement of the lenses in three different parts, part 1 accommodated by the larger lens

C of diameter 10 cm, the part 2 accommodated by medium lens B of diameter 5.5 cm and

the last part by lens A the smaller one

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Figure no.17 Figure depicting the different lenses and their focal points.

Figure no.18 measurement of temperature at focal points using thermocouples.

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COMMERCIAL SOLAR THERMAL SYSTEM

Figure no.19 Commercial solar heating system

The above diagram shows how the water travels in the solar heating system. Initially

domestic cold water flows through the control valves shown in the diagram by blue lines.

Cold water enters the flat plate collectors and the collectors of the dimensions 4feet * 10

feet hold the water till they are heated with the radiation of sun’s rays. The control valves

present in the system ensures that the hot water doesn’t reverse back to the cold storage

container. After this stage hot water flows through storage tanks and finally can be used

for the domestic purpose.

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3.7) KEY PARAMETERS

The seasonal changes The solar insolation intensity level

Insolation is a measure of solar radiation energy received on a givensurface area and recorded during a given time. It is also called as solarIrradiation.

During a clear day (sunny day) the earth can receive as much as 2000 Btu/ft2/dayor6.39 kwh/m2/day, 1 British thermal unit = 1055 joules.

During a mildly cloudy day the earth receives as much as 1500 Btu/ft2/day or 4.72 kwh/m2 /day

In the case of a cloudy day earth receives 1000 1500 Btu/ft2/ or 3.06 kwh/m2/day.

Even the latitudes and longitudes of a particular place also place a major role in the solarinsolation levelsTopography and location of the place

Rajasthan, the largest state in India receives maximum solar radiation intensity inIndia

Rajasthan has around 208,110 Sq.km of desert land

Rajasthan has more than 325 sunny days in a year with solar radiation of about 6-7Kwh/sq-m/day

The direct normal insolation over Rajasthan varies from 1800 Kwh/m2 to2600Kwh/m2

So Rajasthan would be the best place or ideal place to set up any solar PVs. Next comes the states of Gujarat, Maharashtra, Tamil Nadu, Andhra Pradesh Karnatakaare a few states where it is economical to setup flat plate collectors.

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The solar insolation intensity levels for some of the major cities of India (globalinsolation kwh/m2/day) are shown below

Table no.7 Insolation intensity levels of some cities over a period of one year

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3.8) COST ANALYSIS

The cost of 125 LPD system is very economical will cost Rs 20,000/- plus VAT @4%,

which is equivalent to the cost of 4 electrical geysers.

The cost of lenses of diameter ranging from 5 cm to 20 cm will cost around 100 rupees.

Depending upon the size of the glass plate an additional amount of RS 5000 -10,000/- is

necessary for installing the lenses of various diameters. So there is an additional 25%

increment in the cost when compared with a traditional flat plate collector.

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CHAPTER- 4

RESULTS AND DISCUSSION

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4) RESULTS AND DISCUSSION

1. The angle of inclination required for the set up to perform efficiently must only

range between = (25°-35°)

2. The percentage utilization of area cannot be greater than 60 %.

3. The cost increases by 25% if this set up is implemented

4. The temperature obtained using lenses is twice as high as temperature obtained

without lenses.

5. The shadow temperature recorded is always more than the surface temperature by

5°-15°c based on the area of the shadow formed.

6. The highest temperature recorded during the span of the project was 125 °c and

the lowest was 43°c

7. Larger the diameter of the lens greater is the distance between the center of the

lens and the focal point formed

8. In order to reduce the gap between the glass plate and the glazing sheet lenses

with diameters ranging between 5-8 cm are recommended ( only if both the glass

plate and the glazing sheet are parallel to each other)

9. It is not mandatory that the glass plate and the glazing sheet need to be parallel

and inclined. If larger diameter lens are required ,as the distance between the plate

and sheet increases then the glass plate can be kept at an preferable angle while

the glazing sheet is absolutely( ground where =0°) coincident with the base or

horizontal axis.

10. As temperatures up to 125°c are obtained this principle can also be applied to

solar water cooker

11. Perfect insulation cannot be achieved (100 % insulation) unless vacuum comes

into picture.

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SUMMARY

The main objective of the entire project was to add supplementary features to a traditional

flat plate collector by the use of convex lenses of different diameters. After numerous

numbers of trials and errors the perfect setup was obtained by using n different lenses of

various diameters for optimal utilization of heat.

There will be an increase in the cost(25%) if lenses are implemented but the temperature

obtained using lenses is twice that of the temperature obtained without using any lens.

For general daily purposes it is recommended to opt for lenses having small diameters

ranging between (5-8) cm.

The angle of inclination is the most important parameter and after performing many

experiments, must always lie within the range of 25°-30° only for optimal utilization of

heat. It is also found out that the glass plate and the glazing sheet need not to be parallel.

From the graphs and various numerical data the use of lenses helped in increasing the

temperature of the entire system. The shadow formed by the lens itself is sufficient to

heat the fluid (mostly liquids with boiling points less than 100 °c only).

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REFERENCES

1. SOLAR ENERGY (principles of thermal collection and storage)by

S P SUKHATME 2ndedition

2. SOLAR ENERGYfundamentals and applications by H P GARG & J PRAKSH

5th revised edition.

3. SOLAR ENERGYfundamentals, modeling and applications by G N TIWARI

4. Support and guidance from our project guide Sri SSV RamanaRao,Associate

Professor, and Department of Industrial Production Engineering.

5. Commercial solar heating system from HTP products .

url source:http://www.htproducts.com/literature/SolarHTPFlatPlateBrochure.pdf

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