FINAL PROJECT REPORT

1

A

PROJECT REPORT ON

"SOLAR POWER BASED THERMOELECTRIC COOLING"

SUBMITTED TO THE SP PUNE UNIVERSITY, PUNE

FOR THE PARTIAL FULFILLMENT OF THE DEGREE

OF BACHELOR OF ENGINEERING

IN ELECTRICAL ENGINEERING

BY

AnkitNaik (Roll No. B80212506)

Devendra Kalkar (Roll No. B80212516)

Kunal Kulkarni (Roll No. B80212535)

GandharUkidve (Roll No. B80212574)

UNDER THE GUIDANCE OF

PROF V.V KULKARNI

DEPARTMENT OF ELECTRICAL ENGINEERING

AISSMS COLLEGE OF ENGINEERING PUNE, 411001

SAVITRIBAI PHULE PUNE UNIVERSITY

YEAR 2014-15

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CERTIFICATE

This is to certify that the project entitled

SOLAR POWER BASED THERMOELECTRIC COOLING

Submitted by

AnkitNaik B80212506

Devendra Kalkar B80212516

Kunal Kulkarni B80212535

GandharUkidve B80212574

Is a bonafide work carried out by them under the supervision and guidance of Prof.V.V

Kulkarni and is approved by the partial fulfilment of the requirements of University of

Pune for the award of Bachelor of Engineering (Electrical)

Date :

Dr. (Mrs.) A.A Godbole Prof.V.V.Kulkarni

Head of Department Project Guide

External Examiner

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ABSTRACT

The need for renewable energy sources is on the rise because of the acute energy crisis in

the world today. India plans to produce 100 gigawatts of solar power by the year 2022,

whereas we have only realized 2.7 gigawatts of our potential as of March 2014. Solar

energy is a vital untapped resource in a tropical country like ours. The main hindrance for

the penetration and reach of solar PV systems is their low efficiency and high capital cost.

Our project essentially focuses on developing a solar photovoltaic cell based

thermoelectric cooler which can function as the air conditioning system in automobiles. In

doing so, we can restrict the fuel intake which is needed in the compressor in conventional

automobile air conditioning systems.

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ACKNOWLEDGEMENT

We would like to express our profound gratitude to our project guide Prof.(Mr) V. V.

Kulkarni for his meticulous planning, valuable guidance, constant encouragement, and the

invaluable time he spent with us discussing each aspect of our project.

We would like to thank our project co-ordinator Prof. M. H. Dhend for co-ordinating the

project work.

We also express sincere respect to Dr. (Mrs.) A. A. Godbole (H.O.D. Electrical

Engineering A.I.S.S.M.S. C.O.E. Pune) and all staff members who have directly or

indirectly contributed in bringing this project to success.

At the last but never the least we would like to thank all the members of the Department of

Electrical Engineering, AISSMS COE, for the constant support and encouragement.

AnkitNaik

Devendra Kalkar

Kunal Kulkarni

GandharUkidve

(B. E Electrical)

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TABLE OF CONTENTS

ABSTRACT ...................................................................................................................................3

ACKNOWLEDGEMENT ............................................................................................................4

TABLE OF CONTENTS .............................................................................................................5

LIST OF FIGURES ......................................................................................................................7

LIST OF TABLES ........................................................................................................................9

1. INTRODUCTION ................................................................................................................1

1.1 GENERAL SCENARIO OF ENVIRONMENTAL CONDITIONS………………….1

1.2 GLOBAL WARMING……………………………………………………………….1

1.3 OZONE DEPLETION………………………………………………………………..2

1.4 CLIMATE CHANGE…………………………………………………………………4

1.5 AIR CONDITIONING IMPACT ON FOSSIL FUELS………………………………8

1.6 PROJECT IDENTIFICATION……………………………………………………….9

2. DESCRIPTION…………………………………………………………………………..11

2.1 SOLAR ENERGY IN INDIA .......................................................................................11

2.2 PHOTOVOLTAIC CELL .............................................................................................12

2.3 FLEXIBLE PV CELL ...................................................................................................14

2.4 SUMMARY OF CURRENT PV TECHNOLOGY.......................................................15

2.5 PELTIER DEVICE........................................................................................................22

2.6 REGULATOR CIRCUIT..............................................................................................30

2.7 LM 723 IC FEATURE………………………………………………………………..31

3. MATHEMATICAL MODELLING……………………………………………………37

3.1 SOLAR PANEL MODELLING…………………………………………………......37

3.2 ANNUAL SOLAR OUTPUT OF PANEL…………………………………………..37

3.3 PELTIER MODULE HEAT SINK CALCULATIONS …………………………….37

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4. TESTING AND EVALUATION………………………………………………………43

4.1 INDIVIDUAL CELL TESTING……………………………………………………...47

4.2 PELTIER MODULE TESTING………………………………………………………50

5. PROJECT EXPENDITURE…………………………………………………………….62

6. RESULTS AND CONCLUSION………………………………………………………..64

7. FUTURE SCOPE AND DEVELOPMENT…………………………………………….66

REFERENCES………………………………………………………………………...67

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LIST OF FIGURES:

FIGURE NUMBER FIGURE DESCRIPTION

1 Global Warming and Greenhouse effect

2 Ozone Depletion

3 Schematic Diagram of photovoltaic based

TEC

4 Solar Insolation in India

5 Solar cell working

6 Flexible solar cell

7 Ideal I-V plot

8 I-V plot for different irradiation levels

9 Effect of shading

10 Effect of temperature

11 Pole mounting of array

12 Ground mounting

13 Peltier effect

14 Thermoelectric module for cooling

15 Peltier module

16 Peltier module (alternate view)

17 Cut Section view of peltier module TEC1-

12706

18 Identification of peltier module

19 Regulator circuit

20 LM723 internal circuit

21 LM 723 IC pin diagram

22 Thermal resistance circuit

23 Circuit diagram

24 I-V plot

25 P-V plot

26 Solar panel (a)

27 Solar panel (b)

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28 Thermoelectric module setup

29 Thermoelectric circuit

30 Thermoelectric module alternate view

31 Temperature dependence curve (a)

32 Temperature dependence curve (b)

33 Temperature dependence curve (c)

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LIST OF TABLES

TABLE NUMBER TABLE DESCRIPTION

1 V-I OBSERVATIONS

2 CELL BLOCK A AND B TESTING

3 CELL BLOCK C AND D TESTING

4 CELL BLOCK E AND F TESTING

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CHAPTER 1

INTRODUCTION

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1. INTRODUCTION

1.1 GENERAL SCENARIO OF ENVIRONMENTAL CONDITIONS

In today’s time, there are emerging several environmental issues due to excessive

stress on fossil fuels and other commercialized pollution causing sources. One of the

major contributor to the pollution is the Fuel Combustion pollutants namely CO2,

SO2 etc. Adding to this list, air-conditioning materials like CFC’s have also

contributed a lot to the pollution. Increased usage has lead to the following impact on

the environment:-

1.2 GLOBAL WARMING

Global warming refers to an unequivocal and continuing rise in the average

temperature of Earth's climate system. Since 1971, 90% of the warming has occurred

in the oceans. Despite the oceans' dominant role in energy storage, the term "global

warming" is also used to refer to increases in average temperature of the air and sea at

Earth's surface. Since the early 20th century, the global air and sea surface

temperature has increased about 0.8 °C (1.4 °F), with about two-thirds of the increase

occurring since 1980. Each of the last three decades has been successively warmer at

the Earth's surface than any preceding decade since 1850.

Scientific understanding of the cause of global warming has been reported by

scientists that Global warming is being caused by increasing concentrations of

greenhouse gases produced by human activities.The largest driver of global warming

is carbon dioxide (CO2) emissions from fossil fuel combustion, cement production,

and land use changes such as deforestation.

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FIGURE 1: GLOBAL WARMING AND GREENHOUSE EFFECT

1.3 OZONE DEPLETION

The ozone layer is a belt of naturally occurring ozone gas that sits 9.3 to 18.6 miles

(15 to 30 kilometers) above Earth and serves as a shield from the harmful ultraviolet B

radiation emitted by the sun.

Ozone is a highly reactive molecule that contains three oxygen atoms. It is constantly

being formed and broken down in the high atmosphere, 6.2 to 31 miles (10 to 50

kilometers) above Earth, in the region called the stratosphere.

Today, there is widespread concern that the ozone layer is deteriorating due to the

release of pollution containing the chemicals chlorine and bromine. Such deterioration

allows large amounts of ultraviolet B rays to reach Earth, which can cause skin cancer

and cataracts in humans and harm animals as well.

Extra ultraviolet B radiation reaching Earth also inhibits the reproductive cycle of

phytoplankton, single-celled organisms such as algae that make up the bottom rung of

the food chain. Biologists fear that reductions in phytoplankton populations will in

turn lower the populations of other animals. Researchers also have documented

changes in the reproductive rates of young fish, shrimp, and crabs as well as frogs and

salamanders exposed to excess ultraviolet B.

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Chlorofluorocarbons (CFCs), chemicals found mainly in spray aerosols heavily used

by industrialized nations for much of the past 50 years, are the primary culprits in

ozone layer breakdown. When CFCs reach the upper atmosphere, they are exposed to

ultraviolet rays, which causes them to break down into substances that include

chlorine. The chlorine reacts with the oxygen atoms in ozone and rips apart the ozone

molecule.

One atom of chlorine can destroy more than a hundred thousand ozone molecules,

according to the the U.S. Environmental Protection Agency.

The ozone layer above the Antarctic has been particularly impacted by pollution since

the mid-1980s. This region’s low temperatures speed up the conversion of CFCs to

chlorine. In the southern spring and summer, when the sun shines for long periods of

the day, chlorine reacts with ultraviolet rays, destroying ozone on a massive scale, up

to 65 percent. This is what some people erroneously refer to as the "ozone hole." In

other regions, the ozone layer has deteriorated by about 20 percent.

About 90 percent of CFCs currently in the atmosphere were emitted by industrialized

countries in the Northern Hemisphere, including the United States and Europe. These

countries banned CFCs by 1996, and the amount of chlorine in the atmosphere is

falling now. But scientists estimate it will take another 50 years for chlorine levels to

return to their natural levels.

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FIGURE 2: OZONE DEPLETION

1.4 CLIMATE CHANGE

Climate change is a change in the statistical distribution of weather patterns when that

change lasts for an extended period of time (i.e., decades to millions of years).

Climate change may refer to a change in average weather conditions, or in the time

variation of weather around longer-term average conditions (i.e., more or

fewer extreme weather events). Climate change is caused by factors such

as biotic processes, variations in solar radiation received by Earth, plate tectonics,

and volcanic eruptions. Certain human activities have also been identified as

significant causes of recent climate change, often referred to as "global warming".

Scientists actively work to understand past and future climate by

using observations and theoretical models. A climate record — extending deep into

the Earth's past — has been assembled, and continues to be built up, based on

geological evidence from borehole temperature profiles, cores removed from deep

accumulations of ice, floral and faunal records, glacial and periglacial processes,

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stable-isotope and other analyses of sediment layers, and records of past sea levels.

More recent data are provided by the instrumental record. General circulation models,

based on the physical sciences, are often used in theoretical approaches to match past

climate data, make future projections, and link causes and effects in climate change.

Physical Evidence

Glaciers

Glaciers are considered among the most sensitive indicators of climate change. Their

size is determined by a mass balance between snow input and melt output. As

temperatures warm, glaciers retreat unless snow precipitation increases to make up for

the additional melt; the converse is also true.

Glaciers grow and shrink due both to natural variability and external forcings.

Variability in temperature, precipitation, and englacial and subglacial hydrology can

strongly determine the evolution of a glacier in a particular season. Therefore, one

must average over a decadal or longer time-scale and/or over many individual glaciers

to smooth out the local short-term variability and obtain a glacier history that is

related to climate.

A world glacier inventory has been compiled since the 1970s, initially based mainly

on aerial photographs and maps but now relying more on satellites. This compilation

tracks more than 100,000 glaciers covering a total area of approximately 240,000 km2,

and preliminary estimates indicate that the remaining ice cover is around

445,000 km2. The World Glacier Monitoring Service collects data annually on glacier

retreat and glacier mass balance. From this data, glaciers worldwide have been found

to be shrinking significantly, with strong glacier retreats in the 1940s, stable or

growing conditions during the 1920s and 1970s, and again retreating from the mid-

1980s to present.[64]

The most significant climate processes since the middle to

late Pliocene (approximately 3 million years ago) are the glacial

and interglacial cycles. The present interglacial period (the Holocene) has lasted about

11,700 years. Shaped by orbital variations, responses such as the rise and fall

of continental ice sheets and significant sea-level changes helped create the climate.

Other changes, including Heinrich events, Dansgaard–Oeschger events and

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the Younger Dryas, however, illustrate how glacial variations may also influence

climate without the orbital forcing.

Glaciers leave behind moraines that contain a wealth of material—including organic

matter, quartz, and potassium that may be dated—recording the periods in which a

glacier advanced and retreated. Similarly, by tephrochronological techniques, the lack

of glacier cover can be identified by the presence of soil or volcanic tephra horizons

whose date of deposit may also be ascertained.

Vegetation

A change in the type, distribution and coverage of vegetation may occur given a

change in the climate. Some changes in climate may result in increased precipitation

and warmth, resulting in improved plant growth and the subsequent sequestration of

airborne CO2. A gradual increase in warmth in a region will lead to earlier flowering

and fruiting times, driving a change in the timing of life cycles of dependent

organisms. Conversely, cold will cause plant bio-cycles to lag. Larger, faster or more

radical changes, however, may result in vegetation stress, rapid plant loss and

desertification in certain circumstances. An example of this occurred during

the Carboniferous Rainforest Collapse (CRC), an extinction event 300 million years

ago. At this time vast rainforests covered the equatorial region of Europe and

America. Climate change devastated these tropical rainforests, abruptly fragmenting

the habitat into isolated 'islands' and causing the extinction of many plant and animal

species.

Satellite data available in recent decades indicates that global terrestrial net primary

production increased by 6% from 1982 to 1999, with the largest portion of that

increase in tropical ecosystems, then decreased by 1% from 2000 to 2009.

Cloud cover and precipitation

Past precipitation can be estimated in the modern era with the global network of

precipitation gauges. Surface coverage over oceans and remote areas is relatively

sparse, but, reducing reliance on interpolation, satellite clouds and precipitation data

has been available since the 1970s. Quantification of climatological variation of

precipitation in prior centuries and epochs is less complete but approximated using

proxies such as marine sediments, ice cores, cave stalagmites, and tree rings.

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Climatological temperatures substantially affect cloud cover and precipitation. For

instance, during the Last Glacial Maximum of 18,000 years ago, thermal-

driven evaporation from the oceans onto continental landmasses was low, causing

large areas of extreme desert, including polar deserts (cold but with low rates of cloud

cover and precipitation). In contrast, the world's climate was cloudier and wetter than

today near the start of the warmAtlantic Period of 8000 years ago.

Estimated global land precipitation increased by approximately 2% over the course of

the 20th century, though the calculated trend varies if different time endpoints are

chosen, complicated by ENSO and other oscillations, including greater global land

cloud cover precipitation in the 1950s and 1970s than the later 1980s and 1990s

despite the positive trend over the century overall. Similar slight overall increase in

global river runoff and in average soil moisture has been perceived.

Animals

Remains of beetles are common in freshwater and land sediments. Different species of

beetles tend to be found under different climatic conditions. Given the extensive

lineage of beetles whose genetic makeup has not altered significantly over the

millennia, knowledge of the present climatic range of the different species, and the

age of the sediments in which remains are found, past climatic conditions may be

inferred.

Similarly, the historical abundance of various fish species has been found to have a

substantial relationship with observed climatic conditions. Changes in the primary

productivity of autotrophs in the oceans can affect marine food webs.

Sea level change

Global sea level change for much of the last century has generally been estimated

using tide gauge measurements collated over long periods of time to give a long-term

average. More recently, altimeter measurements — in combination with accurately

determinedsatellite orbits — have provided an improved measurement of global sea

level change. To measure sea levels prior to instrumental measurements, scientists

have dated coral reefs that grow near the surface of the ocean, coastal

sediments, marine terraces,ooids in limestones, and nearshore archaeological remains.

The predominant dating methods used are uranium series and radiocarbon,

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with cosmogenic radionuclides being sometimes used to date terraces that have

experienced relative sea level fall. In the earlyPliocene, global temperatures were 1–

2˚C warmer than the present temperature, yet sea level was 15–25 meters higher than

today.

1.5 AIR CONDITIONING IMPACT ON FOSSIL FUELS

The power necessary to operate a vehicle air-conditioning compressor is significant

and it can be greater than the engine power required to move a mid-sized vehicle at a

constant speed of 56 km/h (35 mph). A 400-W load on a conventional engine can

decrease the fuel economy by about 0.4 km/L . The United States could save over $6

billion annually if all the light-duty vehicles in the country achieved a modest 0.4-

km/L (1-mpg) increase in fuel economy.

The size of the air-conditioning system is related to the peak thermal load in the

vehicle. The peak thermal load is generally related to the maximum temperature the

cabin will reach while soaking in the sun.

An automobile is used, on average, about 249 hours annually or about 41 minutes per

day, 365 days a year. Estimates of air-conditioning use range from 107 to 121 hours

per year or 43% to 49% of vehicle usage. Actual use varies considerably depending on

such factors as climate, time of day, time of year, type of vehicle (including vehicle

colour), outdoor/indoor parking, occupant clothing, recent occupant activity levels,

length of trip, vehicle speed, and personal preference. Fuel use in the U.S. in 1998 was

about 473 billion litres (125 billion gallons) for on-road use including gasoline-fuelled

commercial trucks. In 1998 there were about 203.6 million cars and light duty trucks

on the road including sport utility vehicles and minivans. This resulted in an average

fuel use of 2316 litres (612 gallons) of gasoline per vehicle, or about 8.3 km/l (19.6

mpg) for an average of 19,300 km/yr (12,000 miles/year) at an average speed of 77.5

km/h (48.2 mph).

The air conditioning system is the single largest auxiliary load on a vehicle by nearly

an order of magnitude. Current air conditioning systems reduce the fuel economy of

conventional vehicles, thus incremental improvements can have a significant near-

term benefit because of the large number of new cars sold each year. For high fuel

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economy vehicles, current air conditioning systems have a completely unacceptable

impact on fuel economy.

1.6 IDENTIFICATION OF PROJECT

With excessive usage of fossil fuels for basically all purposes, even a slightest

reduction in it would result in a large sum of annual savings and benefits to the

environment. Thus, to reduce stress on fossil fuels, emphasis must be given to

renewable energy resources. Solar energy is the most vulnerable and efficient

renewable energy source. Though technology is yet being developed to harness these

sources, the available methods are also quite efficient.

With this in mind, a solar photovoltaic based air-conditioning system needs to be

developed. A basic schematic of the idea is presented below.

FIGURE 3: SCHEMATIC DIAGRAM OF PHOTOVOLTAIC BASED TEC

The primal motive of this project is aimed at improving fuel economy of a vehicle by

shifting part or complete thermal load on to the thermoelectric devices rather than the

conventional compressor based systems. But practical considerations and limitations

do not allow the entire load to be shifted onto the thermoelectric modules, thus this

system is going to be more or less a supplementary system to the main compressor

based system.

The possible outcome of this project can improve fuel efficiency which can end up in

drastic amount of saving in local (proprietary) or national economies.

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CHAPTER 2

DESCRIPTION

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2.DESCRIPTION

2.1 SOLAR ENERGY IN INDIA:

India is densely populated and has high solar insolation, an ideal combination for

using solar power in India.. In the solar energy sector, some large projects have been

proposed, and a 35,000 km2 (14,000 sq mi) area of the Thar Desert has been set aside

for solar power projects, sufficient to generate 700 to 2,100 GW. Also India's Ministry

of New and Renewable Energy has released the JNNSM Phase 2 Draft Policy,[1] by

which the Government aims to install 10 GW of Solar Power and of this 10 GW

target, 4 GW would fall under the central scheme and the remaining 6 GW under

various State specific schemes.

In July 2009, India unveiled a US$19 billion plan to produce 20 GW of solar power

by 2020.[2] Under the plan, the use of solar-powered equipment and applications

would be made compulsory in all government buildings, as well as hospitals and

hotels. On 18 November 2009, it was reported that India was ready to launch its

National Solar Mission under the National Action Plan on Climate Change, with plans

to generate 1,000 MW of power by 2013. From August 2011 to July 2012, India went

from 2.5 MW of grid connected photovoltaics to over 1,000 MW.

According to a 2011 report by BRIDGE TO INDIA and GTM Research, India is

facing a perfect storm of factors that will drive solar photovoltaic (PV) adoption at a

"furious pace over the next five years and beyond". The falling prices of PV panels,

mostly from China but also from the U.S., have coincided with the growing cost of

grid power in India. Government support and ample solar resources have also helped

to increase solar adoption, but perhaps the biggest factor has been need. India, "as a

growing economy with a surging middle class, is now facing a severe electricity

deficit that often runs between 10% and 13% of daily need". India is planning to

install the World's largest Solar Power Plant with 4,000 MW Capacity near Sambhar

Lake in Rajasthan.

On 16 May 2011, India’s first 5 MW of installed capacity solar power project was

registered under the Clean Development Mechanism. The project is in Sivagangai

Village, Sivaganga district, Tamil Nadu

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FIGURE 4: SOLAR INSOLATION IN INDIA

2.2 PHOTOVOLTAIC CELL

A solar cell, or photovoltaic cell (PV), is a device that converts light into electric

current using the photoelectric effect. The first solar cell was constructed by Charles

Fritts in the 1880s. In 1931 a German engineer, Dr Bruno Lange, developed a photo

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cell using silver selenide in place of copper oxide. Following the work of Russell Ohl

in the 1940s, researchers Gerald Pearson, Calvin Fuller and Daryl Chapin created the

silicon solar cell in 1954. These early solar cells cost 286 USD/watt and reached

efficiencies of 4.5–6%. By 2012 available efficiencies exceed 20% and the maximum

efficiency of research photovoltaics is over 40%.

Photovoltaics (PV) is a method of generating electrical power by converting solar

radiation into direct current electricity using semiconductors that exhibit the

photovoltaic effect. Photovoltaic power generation employs solar panels composed of

a number of solar cells containing a photovoltaic material. Solar photovoltaics power

generation has long been seen as a clean sustainable energy technology which draws

upon the planet’s most plentiful and widely distributed renewable energy source – the

sun. It is well proven, as photovoltaic systems have now been used for fifty years in

specialised applications, and grid-connected systems have been in use for over twenty

years.

In 2013, its fast-growing capacity increased by 36% to a running total of 136 GW,

worldwide. This is sufficient to generate 160 TWh/year or about 0.85% of the

electricity demand on the planet. China and Japan are now the fastest growing

markets, while Germany remains the world's largest producer, contributing almost 6%

to its national electricity demands.

Solar photovoltaics is now, after hydro and wind power, the third most important

renewable energy source in terms of globally installed capacity. More than 100

countries use solar PV. Installations may be ground-mounted (and sometimes

integrated with farming and grazing) or built into the roof or walls of a building

(either building-integrated photovoltaics or simply rooftop).Let us consider what

happens in the vicinity of a p–n junction when it is exposed to sunlight. As photons

are absorbed, hole-electron pairs may be formed. If these mobile charge carriers reach

the vicinity of the junction, the electric field in the depletion region will push the holes

into the p-side and push the electrons into the n-side, as shown in Figure. The P-side

accumulates holes and the n-side accumulates electrons, which creates a voltage that

can be used to deliver current to a load.

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FIGURE 5 : SOLAR CELL WORKING

2.3 FLEXIBLE SOLAR PANELS

Flexible solar panels are the new technology in solar energy harnessing. In this type of

panels, the photovoltaic material is printed on a roll of conductive plastic using fast

newspaper printing technology. Printing enables one to achieve high materials

utilization of the photoactive materials. As a result, the simple, highest-yeild

techniques in plain air is capital –efficient and eliminates the need for costly vacuum

deposition techniques such as conventionally used to fabricate thin film solar cells.

FIGURE 6: FLEXIBLE SOLAR PANEL

These chemistry-based cells are lightweight, flexible and more versatile than previous

generations of products. The result is a new breed of coatable, plastic, flexible

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photovoltaics that can be used in many applications where traditional photovoltaics

cannot compete. The photovoltaic functionality is integrated at low cost into existing

structures, printing rolls of the stuff anywhere, from windows to roofs, through

external and internal walls. Flexible solar cells, indeed, replace the

traditional installation approach with an integration strategy.In general, man is

eventually learning how to efficiently harness the immense amount of solar energy

that reaches the Earth every second by mimicking Nature and by operating at the

nanoscale. In other words, we are learning how to deliver cost efficient solar

electricity. The average price for a PV module, excluding installation and other

system costs, has dropped from almost $100 per watt in 1975 to about $4 per watt at

the end of 2007. In 2004, a prediction of an industry.s practitioner concluded that for

.thin-film PV alone, production costs are expected to reach $1 per watt in 2010, a cost

that makes solar PV competitive with coal-fired electricity. Adding relevance to this

book.s arguments, however, the first flexible thin-film solar modules profitably

generating electricity for 99 cents a watt (i.e., the price of coal-fired electricity) were

commercialized in late 2007.

2.4 SUMMARY OF CURRENT PV TECHNOLOGY

To insure compatibility with storage batteries or loads, it is necessary to know the

electrical characteristics of photovoltaic modules.As a reminder, "I" is the

abbreviation for in ohms.A photovoltaic module will produce its maximum current

when there is essentially no resistance in the circuit. This would be a short circuit

between its positive and negative terminals.This maximum current is called the short

circuit current, abbreviated I(sc). When the module is shorted, the voltage in the

circuit is zero.Conversely, the maximum voltage is produced when there is a break in

the circuit. This is called the open circuit voltage, abbreviated V(oc). Under this

condition the resistance is infinitely high and there is no current, since the circuit is

incomplete.These two extremes in load resistance, and the whole range of conditions

in between them, are depicted on a graph called a I-V (current-voltage) curve.

Current, expressed in amps, is on the vertical Y-axis. Voltage, in volts, is on the

horizontal X-axis

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FIGURE 7: IDEAL I-V PLOT

The short circuit current occurs on a point on the curve where the voltage is zero. The

open circuit voltage occurs where the current is zero.The power available from a

photovoltaic module at any point along the curve is expressed in watts. Watts are

calculated by multiplying the voltage times the current (watts = volts x amps, or W =

VA).At the short circuit current point, the power output is zero, since the voltage is

zero.At the open circuit voltage point, the power output is also zero, but this time it is

because the current is zero.There is a point on the "knee" of the curve where the

maximum power output is located. This point on our example curve is where the

voltage is 17 volts, and the current is 2.5 amps. Therefore the maximum power in

watts is 17 volts times 2.5 amps, equaling 42.5 watts.The power, expressed in watts, at

the maximum power point is described as peak, maximum, or ideal, among other

terms. Maximum power is generally abbreviated as "I (mp)." Various manufacturers

call it maximum output power, output, peak power, rated power, or other terms.

The current-voltage (I-V) curve is based on the module being under standard

conditions of sunlight and module temperature. It assumes there is no shading on the

module.

Standard sunlight conditions on a clear day are assumed to be 1000 watts of solar

energy per square meter (1000 W/m2or lkW/m2). This is sometimes called "one sun,"

or a "peak sun." Less than one sun will reduce the current output of the module by a

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proportional amount. For example, if only one-half sun (500 W/m2) is available, the

amount of output current is roughly cut in half.

FIGURE 8: I-V PLOT FOR DIFFERENT IRRADIATION LEVELS

Because photovoltaic cells are electrical semiconductors, partial shading of the

module will cause the shaded cells to heat up. They are now acting as inefficient

conductors instead of electrical generators. Partial shading may ruin shaded

cells.Partial module shading has a serious effect on module power output. For a

typical module, completely shading only one cell can reduce the module output by as

much as 80%. One or more damaged cells in a module can have the same effect as

shading.

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FIGURE 9: EFFECT OF SHADING

This is why modules should be completely unshaded during operation. A shadow

across a module can almost stop electricity production. Thin film modules are not as

affected by this problem, but they should still be unshaded.Module temperature affects

the output voltage inversely. Higher module temperatures will reduce the voltage by

0.04 to 0.1 volts for every one Celsius degree rise in temperature (0.04V/0C to

0.1V/0C). In Fahrenheit degrees, the voltage loss is from 0.022 to 0.056 volts per

degree of temperature rise. This is why modules should not be installed flush against a

surface. Air should be allowed to circulate behind the back of each module so it's

temperature does not rise and reducing its output. An air space of 4-6 inches is usually

required to provide proper ventilation.

19

FIGURE 10: EFFECT OF TEMPERATURE

Eventually, the required voltage is higher than the voltage at the module's maximum

power point. At this operating point, the current production is lower than the current at

the maximum power point. The module's power output is also lower.

To a lesser degree, when the operating voltage is lower than that of the maximum

power point (point #1), the output power is lower than the maximum. Since the ability

of the module to produce electricity is not being completely used whenever it is

operating at a point fairly far from the maximum power point, photovoltaic modules

should be carefully matched to the system load and storage.Using a module with a

maximum voltage which is too high should be avoided nearly as much as using one

with a maximum voltage which is too low.The output voltage of a module depends on

the number of cells connected in series. Typical modules use either 30, 32, 33, 36, or

44 cells wired in series.The modules with 30-32 cells are considered self regulating

modules. 36 cell modules are the most common in the photovoltaic industry. Their

slightly higher voltage rating, 16.7 volts, allows the modules to overcome the

reduction in output voltage when the modules are operating at high temperatures.

Modules with 33 - 36 cells also have enough surplus voltage to effectively charge

high antimony content deep cycle batteries. However, since these modules can

overcharge batteries, they usually require a charge controller.Finally, 44 cell modules

are available with a rated output voltage of 20.3 volts. These modules are typically

used only when a substantially higher voltage is required.As an example, if the

20

module is sometimes forced to operate at high temperatures, it can still supply enough

voltage to charge 1 2 volt batteries.Another application for 44 cell modules is a system

with an extremely long wire run between the modules and the batteries or load. If the

wire is not large enough, it will cause a significant voltage drop. Higher module

voltage can overcome this problem.It should be noted that this approach is similar to

putting a larger engine in a car with locked brakes to make it move faster. It is almost

always more cost effective to use an adequate wire size, rather than to overcome

voltage drop problems with more costly 44 cell modules. This section discusses

maximum power point trackers. These devices are used to bring the module to a point

as close as possible to the maximum power point. They are used mostly in direct DC

systems, particularly with DC motors for pumping.

2.4.1 MOUNTING OF AN ARRAY

Pole mounting

Typically, up to four modules can be connected together and mounted on a pole

(Figure 2-37). Typically, 2 1/2" nominal steel pipe (O.D. of 3") is used.Black iron or

steel pipe can be used, if painted. Galvanized pipe, rarely available in this size, can be

used if compatible fasteners are used. Larger arrays can be pole mounted, if hardware

sizes are appropriately increased.The same types of materials used for bracket

mounting should be used for pole mounting.

FIGURE 11: POLE MOUNTING OF AN ARRAY

21

Ground mounting

For arrays of eight or more modules, ground mounting is usually the most appropriate

technique. The greatest concern is often the uplifting force of wind on the array. This

is why most ground mounted arrays are on some kind of sturdy base, usually

concrete.Concrete bases are either piers, a slab with thicker edges, or footings at the

front and rear of the array. All three usually include a steel reinforcement bar.In some

remote sites it may be more desirable to use concrete block instead of poured

concrete. The best way to do this is to use two-web bond-beam block, reinforce it with

steel, and fill the space between the webs with concrete or mortar.Pressure-treated

wood of adequate size is sometimes used for ground mounting. This can work well in

fairly dry climates, but only if the beams are securely anchored to the ground, and

regular inspection and maintenance is provided.

FIGURE 12: GROUND MOUNTING

22

2.5 PELTIER DEVICE

2.5.1 PELTIER EFFECT:

The Peltier effect is the presence of heating or cooling at an electrified junction of two

different conductors and is named for French physicist Jean Charles AthanasePeltier,

who discovered it in 1834. When a current is made to flow through a junction between

two conductors A and B, heat may be generated (or removed) at the junction. The

Peltier heat generated at the junction per unit time is equal to,

Q = (∏A - ∏B)I

Where ∏ is the peltier coefficient of the conductor

And I is the electric current

The Peltier coefficients represent how much heat is carried per unit charge. Since

charge current must be continuous across a junction, the associated heat flow will

develop a discontinuity if ∏Aand ∏B are different. The Peltier effect can be

considered as the back-action counterpart to the Seebeck effect (analogous to the

back-emf in magnetic induction): if a simple thermoelectric circuit is closed then the

Seebeck effect will drive a current, which in turn (via the Peltier effect) will always

transfer heat from the hot to the cold junction. The close relationship between Peltier

and Seebeck effects can be seen in the direct connection between their coefficients: ∏

= TS

A typical Peltier heat pump device involves multiple junctions in series, through

which a current is driven. Some of the junctions lose heat due to the Peltier effect,

while others gain heat. Thermoelectric heat pumps exploit this phenomenon, as do

thermoelectric cooling devices found in refrigerators.

23

FIGURE 13 : PELTIER EFFECT

Thermoelectric materials can be used as refrigerators, called "thermoelectric coolers",

or "Peltier coolers" after the Peltier effect that controls their operation. As a

refrigeration technology, Peltier cooling is far less common than vapor-compression

refrigeration. The main advantages of a Peltier cooler (compared to a vapor-

compression refrigerator) are its lack of moving parts or circulating fluid, and its small

size and flexible shape (form factor). Another advantage is that Peltier coolers do not

require refrigerant fluids, such aschlorofluorocarbons (CFCs) and related chemicals,

which can have harmful environmental effects.

The main disadvantage of Peltier coolers is that they cannot simultaneously have low

cost and high power efficiency. Advances in thermoelectric materials may allow the

creation of Peltier coolers that are both cheap and efficient. It is estimated that

materials with ZT >3 (about 20–30% Carnot efficiency) are required to replace

traditional coolers in most applications. Today, Peltier coolers are only used in niche

applications.

The Peltier effect can be used to create a refrigerator which is compact and has no

circulating fluid or moving parts; such refrigerators are useful in applications where

their advantages outweigh the disadvantage of their very low efficiency.

2.5.2 THERMOELECTRIC COOLING:

Thermoelectric cooling uses the Peltier effect to create a heat flux between the

junction of two different types of materials. A Peltier cooler, heater, or thermoelectric

24

heat pump is a solid-state active heat pump which transfers heat from one side of the

device to the other, with consumption of electrical energy, depending on the direction

of the current. Such an instrument is also called a Peltier device, Peltier heat pump,

solid state refrigerator, or thermoelectric cooler (TEC). They can be used either for

heating or for cooling (refrigeration), although in practice the main application is

cooling. It can also be used as a temperature controller that either heats or cools.

This technology is far less commonly applied to refrigeration than vapor-compression

refrigeration is. The main advantages of a Peltier cooler (compared to a vapor-

compression refrigerator) are its lack of moving parts or circulating liquid, near-

infinite life and invulnerability to potential leaks, and its small size and flexible shape

(form factor). Its main disadvantage is high cost and poor power efficiency. Many

researchers and companies are trying to develop Peltier coolers that are both cheap

and efficient.

A Peltier cooler can also be used as a thermoelectric generator. When operated as a

cooler, a voltage is applied across the device, and as a result, a difference in

temperature will build upbetween the two sides.[3] When operated as a generator, one

side of the device is heated to a temperature greater than the other side, and as a result,

a difference in voltage will build up between the two sides (the Seebeck effect).

However, a well-designed Peltier cooler will be a mediocre thermoelectric generator

and vice-versa, due to different design and packaging requirements.

FIGURE 14: THERMOELECTRIC MODULE FOR COOLING

Thermoelectric coolers operate by the Peltier effect (which also goes by the more

general name thermoelectric effect). The device has two sides, and when DC current

flows through the device, it brings heat from one side to the other, so that one side

gets cooler while the other gets hotter. The "hot" side is attached to a heat sink so that

25

it remains at ambient temperature, while the cool side goes below room temperature.

In some applications, multiple coolers can be cascaded together for lower temperature.

2.5.3 CONSTRUCTION OF PELTIER DEVICE

Two unique semi-conductors, one n-type and one p-type, are used because they need

to have different electron densities. The semi-conductors are placed thermally in

parallel to each other and electrically in series and then joined with a thermally

conducting plate on each side. When a voltage is applied to the free ends of the two

semiconductors there is a flow of DC current across the junction of the semi-

conductors causing a temperature difference. The side with the cooling plate absorbs

heat which is then moved to the other side end of the device where the heat sink is.

TECs are typically connected side by side and sandwiched between two ceramic

plates. The cooling ability of the total unit is then proportional to the number of TECs

in it.

Some benefits of using a TEC are:

Temperature control to within fractions of a degree can be maintained

Flexible shape (form factor); in particular, they can have a very small size

Can be used in environments that are smaller or more severe than conventional

refrigeration

Has a long life, with mean time between failures (MTBF) exceeding 100,000 hours

Is controllable via changing the input voltage/current

Some disadvantages of using a TEC are:

Only a limited amount of heat flux is able to be dissipated

Relegated to applications with low heat flux

Not as efficient, in terms of coefficient of performance, as vapor-compression systems

26

FIGURE 15 : PELTIER MODULE

FIGURE 16: PELTIER MODULE (ALTERNATE VIEW)

27

A single-stage TEC will typically produce a maximum temperature difference of 70°C

(126°F) between its hot and cold sides. The more heat moved using a TEC, the less

efficient it becomes, because the TEC needs to dissipate both the heat being moved, as

well as the heat it generates itself from its own power consumption. The amount of

heat that can be absorbed is proportional to the current and time.

FIGURE 17: CUT SECTION VIEW OF A PELTIER MODULE TEC1-12706

W=PIt

where P is the Peltier Coefficient, I is the current, and t is the time. The Peltier

Coefficient is dependent on temperature and the materials the TEC is made of.

Thermoelectric junctions are about 4 times less efficient in refrigeration applications

than conventional means (they offer around 10-15% efficiency of the ideal Carnot

cyclerefrigerator, compared with 40–60% achieved by conventional compression

cycle systems (reverse Rankine systems using compression/expansion). Due to this

lower efficiency, thermoelectric cooling is generally only used in environments where

the solid state nature (no moving parts, low maintenance, compact size, and

orientation insensitivity) outweighs pure efficiency.

Peltier (thermoelectric) cooler performance is a function of ambient temperature, hot

and cold side heat exchanger (heat sink) performance, thermal load, Peltier module

(thermopile) geometry, and Peltier electrical parameters.

Requirements for Thermoelectric materials

-gap semiconductors because of room temperature operation

28

Common thermoelectric materials used as semi-conductors include bismuth telluride,

lead telluride, silicon germanium, and bismuth-antimony alloys. Of this bismuth

telluride is the most commonly used. New high-performance materials for

thermoelectric cooling are being actively researched.

2.5.4 IDENTIFICATION OF PELTIER MODULE

FIGURE 18: IDENTIFICATION OF PELTIER MODULE

Peltier elements all conform to a universal identification specification

The vast majority of TECs have an ID printed on their heated side.

These universal IDs clearly indicate the size, number of stages, number of couples,

and current rating in amps, as seen in the adjacent diagram.

29

2.4.5 ASSEMBLY OF PELTIER MODULE

Step 1:- The TEC – 12706 is sandwiched between two heat sinks as shown below

using an adhesive.

Step 2: Place the fans as shown below.

Step 3: Attach Screws and bolts. Tighten one by one on all four sides till the contact

pressure is optimum.

Step 4: Make electrical connections.

30

2.6 REGULATOR CIRCUIT

FIGURE 19 :REGULATOR CIRCUIT

31

Presented here is a circuit for 30V 10A variable bench power supply that offers

variable voltage and current adjustment. Power supply is based around a LM723

voltage regulator chip and has current limiting. The 2N3055 transistors are a well

proven high current transistor. More 2N3055 transistors can be connected together for

more output current. The transistors will need to be mounted on a good size

heatsink.The output pin will be connected Darlington connected emitter follower with

the transistor Q1. And use the Q1 drive to six transistor Q2-Q7 together parallel. To

expand the current is increased up. From the original currents maximum output of IC

at 1A. When to connect these transistor TIP35 Q1-Q7 to complete 7 pcs. Makes can

supplying up to 30A. By parallel with the transistor Q2, from the Q3 onwards there.

Each transistor can be expanded current is 5A.

The resistor 0.15 ohm at emitter pin of the each transistor has two act as are:

1. Check the current flowing through the transistor Because there are the voltage drop

across them as a ratio of the current flowing through a each transistor.

2. The current through the transistor to equally.

Output voltage of the power circuit is equal to the voltage output of IC1 (15V) minus

the voltage drop across the leg base (B) – E emitter (E) of the transistor driver (Q1)

and the transistor through (. Q2) and the voltage drop across R5 E pin of Q2.

However, since the voltage drop across R5 for this. Changed by the current flowing

through it. Thus making voltage output of this circuit is slightly changed switch from

14V. Under no load is 13V. In fully loaded conditions (regulation).

At this level, it will be maintained pressure succinctly is better than on the electric car.

The output voltage can be changed from 11V to 16V. And the transmitter is normally

used in the car with 12V battery is designed to be compatible with existing 13-14V

voltage.

2.7 LM 723 IC FEATURES

General Description

The LM723/LM723C is a voltage regulator designed primarily for series regulator

applications. By itself, it will supply output currents up to 150 mA; but external

transistors can be added to provide any desired load current. The circuit features

32

extremely low standby current drain, and provision is made for either linear or

foldback current limiting. The LM723/LM723C is also useful in a wide range of other

applications such as a shunt regulator, a current regulator or a temperature controller.

The LM723C is identical to the LM723 except that the LM723C has its performance

guaranteed over a 0°C to a70°C temperature range, instead of -55°C to +125°C.

Features

150 mA output current without external pass transistor

Output currents in excess of 10A possible by adding external transistors

Input voltage 40V max

Output voltage adjustable from 2V to 37V

Can be used as either a linear or a switching regulator

INTERNAL BLOCK DIAGRAM

FIGURE 20: LM 723 INTERNAL CIRCUIT

The internal working can be explained by dividing it into two blocks, the reference

voltage generator and the error amplifier. In the reference voltage generator, a zener

diode is being compelled to operate at fixed point (so that zener output voltage is a

33

fixed voltage) by a constant current Source which comes along with an amplifier to

generate a constant voltage of 7.15V at the Vref pin of the IC.

As for the error amplifier section,it consists of an error amplifier, a series pass

transistor Q1 and a current limiting transistor. The error amplifier can be used to

compare the output voltage applied at Inverting input terminal through a feedback to

the reference voltage Vref applied at the Non-Inverting inputterminal. .The

conduction of the transistor Q1 is controlled by the error signal. It is this transistor that

controls the output voltage

PIN DIAGRAM:

FIGURE 21: LM 723 IC PIN DIAGRAM

Pin Discription:

34

V+ and V-

These are the supply voltage terminals of the IC. V+ is the positive terminal and V- is

the negative terminal. The voltage difference between these terminals should be

between 9.5V to 40V.

Non Inverting Input

This is the non inverting input of the error amplifier whose output is connected to the

series pass transistor. We usually give reference voltage or a portion of it to the non

inverting input.

Inverting Input

This is the inverting input of the error amplifier whose output is connected to the

series pass transistor. We usually give output voltage or a portion of it to the inverting

input. This makes the output voltage constant.

Vref

It is the reference voltage output of the IC. It is the output of voltage reference

amplifier. Its output voltage is about 7.15V.

Vout

It is the output terminal of the IC. Usually output voltage ranges from 2 to 37V. This

pin can provide up to 150mA current.

Current Limit

It is the base input of the current limiter transistor. This pin is used for current limiting

or current fold back applications.

Current Sense

This is the emitter of current limiting transistor. This terminal is used with current

limiting and current fold-back applications.

35

Vc

This is the collector input of the series pass transistor. It is usually directly connected

to the positive supply voltage if an external transistor is not used.

Freq. Comp

Frequency Compensation : This pin is used to connect a capacitor which bypasses

high frequency noises. It is the output of error amplifier. The capacitor is connected

between this pin and inverting input of the error amplifier. The prescribed value of

this capacitor varies for different types of regulators. Please refer the datasheet for

that.

36

CHAPTER 3

MATHEMATICAL MODEL

37

3. MATHEMATICAL MODELLING

3.1 SOLAR PANEL MODELLING

Peltier device being used in system.

.

Stepping down of voltage is required for the peltier modules with the help of a DC-

DC chopper.

3.2 ANNUAL SOLAR OUTPUT OF PANEL

The global formula to estimate the electricity generated in output of a photovoltaic

system is :

E = A * r *H * PR

E = Energy (kWh) A = Total solar panel Area (m²) r = solar panel yield (%) H = Annual

average solar radiation on tilted panels (shadings not included) PR = Performance

ratio, coefficient for losses (range between 0.5 and 0.9, default value = 0.75)

R is the yield of the solar panel given by the ratio : electrical power (in kWp) of one

solar panel divided by the area of one panel Example : the solar panel yield of a PV

module of 250 W with an area of 1.48 m² is 16.8% PR : PR (Performance Ratio) is a

very important value to evaluate the quality of a photovoltaic installation because it

gives the performance of the installation independently of the orientation, inclination

of the panel. It includes all losses.

Selecting default value as 0.75

3.3 PELTIER MODULE HEAT SINK CALCULATIONS

With the increase in heat dissipation from electronics devices and the reduction in

overall form factors, thermal management becomes a more a more important element

of electronic product design.

38

Heat sinks are devices that enhance heat dissipation from a hot surface, usually the

case of a heat generating component, to a cooler ambient, usually air. For the

following discussions, air is assumed to be the cooling fluid. In most situations, heat

transfer across the interface between the solid surface and the coolant air is the least

efficient within the system, and the solid-air interface represents the greatest barrier

for heat dissipation. A heat sink lowers this barrier mainly by increasing the surface

area that is in direct contact with the coolant. This allows more heat to be dissipated

and/or lowers the device operating temperature. The primary purpose of a heat sink is

to maintain the device temperature below the maximum allowable temperature

specified by the device manufacturers.

Before discussing the heat sink selection process, it is necessary to define common

terms and establish the concept of a thermal circuit. Notations and definitions of the

terms are as follows:

Q: total power or rate of heat dissipation in W, represent the rate of heat dissipated by

the electronic component during operation. For the purpose of selecting a heat sink,

the maximum operating power dissipation issued.Tj: maximum junction temperature

of the device in °C. Allowable Tjvalues range from 115°C in typical microelectronics

applications to as high as 180°C for some electronic control devices. In special and

military applications, 65°C to 80°Care not uncommon.Tc: case temperature of the

device in °C. Since the case temperature of a device depends on the location of

measurement, it usually represent the maximum local temperature of the case.

Ts: sink temperature in °C. Again, this represents the maximum temperature of a heat

sink at the location closest to the device.

Ta: ambient air temperature in °C.

Using temperatures and the rate of heat dissipation, a quantitative measure of heat

transfer efficiency across two locations of a thermal component can be expressed in

terms of thermal resistance R, defined as

R = ∆T/Q

Were T is the temperature difference between the two locations. The unit of thermal

resistance is in °C/W, indicating the temperature rise per unit rate of heat dissipation.

This thermal resistance is analogous to the electrical resistance Re, given by Ohm’s

law:

Re =∆V/I

39

With V being the voltage difference and I the current.

FIGURE 22: THERMAL RESISTANCE CIRCUIT

The thermal resistance between the junction and the case of a device is defined as

Rjc = (Tjc)/Q = (Tj- Tc)/Q

This resistance is specified by the device manufacturer. Although the Rjcvalue of a

give device depends on how and where the cooling mechanism is employed over the

package, it is usually given as a constant value. It is also accepted that Rjc is beyond

the user’s ability to alter or control. Similarly, case-to-sink and sink-to-ambient

resistance are defined as

Rcs = (∆Tcs)/Q = (Tc- Ts)/Q

Rsa = (∆Tsa)/Q = (Ts- Ta)/Q

respectively. Here, Rcsrepresents the thermal resistance across the interface between

the case and the heat sink and is often called the interface resistance. This value can be

improved substantially depending on the quality of mating surface finish and/or the

choice of interface material. Rsais heat sink thermal resistance.

To begin the heat sink selection, the first step is to determine the heat sink thermal

resistance required to satisfy the thermal criteria of the component. By rearranging the

previous equation, the heat sink resistance can be easily obtained as

Rsa = ((Ts – Ta)/Q) – Rjc- Rcs

In this expression, Tj, Q and Rjcare provided by the device manufacturer, and Ta and

Rcsare the user defined parameters.

The ambient air temperature Ta for cooling electronic equipment depends on the

operating environment in which the component is expected to be used. Typically, it

40

ranges from 35 to 45°C, if the external air is used, and from 50 to 60°C, if the

component is enclosed or is placed in a wake of another heat generating equipment.

The interface resistance Rcsdepends on the surface finish, flatness, applied mounting

pressure, contact area and, of course, the type interface material and its thickness.

Precise value of this resistance,even for a give type of material and thickness, is

difficult to obtain, since it may vary widely with the mounting pressure and other case

dependent parameters. However, more reliable data can be obtained directly from

material manufacturers or from heat sink manufacturers.With all the parameters on the

right side of the Rsaexpression identified, it becomes the required maximum thermal

resistance of a heat sink for the application. In other words, the thermal resistance

value ofa chosen heat sink for the application has to be equal to or less than Rsavalue

for the junction temperature to be maintained at or below the specified Tj.

When selecting a heat sink, it is necessary to classify the air flow as natural, low flow

mixed, or high flow forced convection. Natural convection occurs when there is no

externally induced flow and heat transfer relies solely on the free buoyant flow of air

surrounding the heat sink. Forced convection occurs when the flow of air is induced

by mechanical means, usually a fan or blower. There is no clear distinction on the

flow velocity that separates the mixed and forced flow regimes. It is generally

accepted in applications that the effect of buoyant force on the overall heat transfer

diminishes to negligible level (under 5%) when the induced air flow velocity excess 1

2 m/s(200 to 400 lfm).

The next step is to determine the required volume of a heat sink. The volume of a heat

sink for a given low condition can be obtained by dividing the volumetric thermal

resistance by the required thermal resistance. Table 3.1.2 is to be used only as a guide

for estimation purposes in the beginning of the selection process. The actual resistance

values may vary outside the above range depending on many additional parameters,

such as actual dimensions of the heat sink, type of the heat sink, flow configuration,

orientation, surface finish, altitude, etc. The smaller values shown above correspond to

heat sink volume of approximately 100 to 200 cm3 (5 to 10 in3)and the larger ones to

roughly 1000 cm3(60in3). The average performance of a typical heat sink is linearly

proportional to the width of a heat sink in the direction perpendicular to the flow, and

approximately proportional to the square root of the fin length in the direction parallel

to the flow. For example, an increase in the width of a heat sink by a factor of two

41

would increase the heat dissipation capability by a factor of two, whereas and increase

the heat dissipation capability by a factor of 1.4. Therefore , if the choice is available,

it is beneficial to increase the width of a heat sink rather than the length of the heat

sink. Also, the effect of radiation heat transfer is very important in natural convection,

as it can be responsible of up to 25% of the total heat dissipation. Unless the

component is facing a hotter surface nearby, it is imperative to have the heat sink

surfaces painted or anodized to enhance radiation.

42

CHAPTER 4

TESTING AND EVALUATION

43

4. TESTING AND EVALUATION

In the month of November and December we performed the testing of the solar panel.

The solar panel which we used was flexible in nature.

Active area of one cell = 0.0118 m2

Active area of entire panel = 0.9204 m

Ambient temperature for flat surface = 34.1◦C

Ambient temperature for curved surface = 32.1◦C

Solar intensity = 1350 W/m2

Readings taken on 4th December 2014

FIGURE 23: CIRCUIT DIAGRAM

Working :

of the panels at different timings of the day and angles against the sun.

Load is varied for different readings of Current , and voltage is measured and hence

Power is calculated.

the solar

insolation are maximum, the reading was taken.

44

TABLE 1: V-I OBSERVATIONS

VOLTAGE (V) CURRENT (A)

42.5 1.7

40.6 2

37.4 2.5

33 3

29 3.5

26.4 4

22.23 4.5

0.3 4.9

46.8 (OPEN CIRCUIT READING) 0

45

FIGURE 24: I-V PLOT

FIGURE 25: P-V PLOT

0

1.72

2.53

3.54

4.54.9

0

1

2

3

4

5

6

0 10 20 30 40 50

Cu

rren

t (A

)

Voltage (V)

I-V PLOT

0

72.1581.2

93.599101.5

105.6100.035

1.47

0

20

40

60

80

100

120

0 10 20 30 40 50

Po

wer

(W

atts

)

Voltage (V)

P-V PLOT

46

FIGURE 26: SOLAR PANEL (A)

FIGURE 27: SOLAR PANEL (B)

47

4.1 INDIVIDUAL CELL TESTING

We measured the incident solar intensity on each cell of the flexible solar panel. The

estimation of the intensity was carried out in the following methods:

Measurement of incident illumination on flat cell surface

Measurement of incident illumination on curved cell surface

TABLE 2: CELL BLOCK A AND B TESTING

48

CELL NO. FLAT

W/m2

CURVED

W/m2

CELL NO. FLAT

W/m2

CURVED

W/m2

C1 1345 1072 D1 1346 1069

C2 1343 1062 D2 1326 1046

C3 1331 1073 D3 1326 1057

C4 1321 1098 D4 1325 1085

C5 1318 1144 D5 1315 1132

C6 1321 1167 D6 1318 1163

C7 1326 1183 D7 1313 1167

C8 1320 1197 D8 1322 1178

C9 1327 1213 D9 1335 1194

C10 1322 1230 D10 1342 1223

C11 1308 1228 D11 1320 1230

C12 1319 1235 D12 1325 1237

C13 1316 1240 D13 1322 1240

TABLE 3: CELL BLOCK C AND D TESTING

49

TABLE 4: CELL BLOCK E AND F TESTING

From our test results we have concluded the following:

1. The maximum efficiency obtained during our testing is 8.25%.

2. Power output of the solar panel is largely dependent incident illumination and

temperature.

3. Incident illumination is greater for a flat surface rather than a curved one.

50

4.2 PELTIER MODULE TESTING

MODULE SPECIFICATION: TEC12715231W15.4V15A

To know the cooling effect, testing of these devices were done at different voltages

and current level to find out the maximum efficiency point at different temperature

levels. The device is placed between the heat with one side cold while other side hot.

The heat sink increases the surface area and to make cooling effective fans are placed.

FIGURE 28: THERMOELECTRIC MODULE SETUP

51

FIGURE 29: THERMOELECTRIC CIRCUIT

FIGURE 30: THERMOELECTRIC MODEL ALTERNATE VIEW

52

OBSERVATIONS:

PERFORMANCE ON 2ND February 2015

Input to the fan=12V

Ambient temperature=25.9

Voltage to the cooler=3.7V

Current to the cooler=5A

Power input to the cooler=18.5W

Volume of the box=65*37*30 cm³=66500cm³

Temperature inside the box(⁰C) Time(min)

25.9 0

24.7 5

24.3 10

24.2 15

24.1 20

CONCLUSION:When an input of 18.5W is given to the thermocooler it gave a

temperature difference of 1.8⁰ in 20minutes.

PERFORMANCE ON 9TH FEBRUARY 2015

Voltage to the cooler=12V

Current to the cooler=17.6A

Power input=211W

Ambient temperature=26⁰C

53

Temperature inside the

box(⁰C)

Hot side

temperature(⁰C)

Time(min)

25.8 26 0

23.6 31.7 5

23.3 34.7 10

23.3 35 15

PERFORMANCE ON 16TH FEBRUARY 2015

Power input to the cooler=211W (12V*17.6A)

Ambient temperature=26.5⁰C

Voltage to the fan=11.8V

Current to the fan=0.27A

Box Temperature(⁰C) Time(Min)

26.5 0

25.8 1

24.9 2

24.5 3

24.2 4

24.1 5

24 6

23.9 7

23.9 8

23.9 9

23.9 10

23.8 11

23.8 12

23.8 15

54

TESTING OF PARTITIONED BOX

Volume of the box=24*37*30cm³=26640cm³

Power input to the cooler=211W(12*17.6)

Voltage to fan=11.8V

Current to the fan=0.27A

.

RESULTS AFTER PROPER ISOLATION (PERFORMED ON 17TH FEBRUARY

2015):

Ambient temperature=29⁰C

Fan Voltage=11.6V

Fan current=0.61A

Input voltage to the cooler=12.15V

Input current to the cooler=15.2A

Wattmeter reading of the cooler=160W

Volume of the box=65*37*30 cm³=66500cm³

Box Temperature(⁰C) Time(Min)

26.8 0

26.5 1

26.1 2

25.8 3

25.6 4

25.5 5

25.5 6

25.5 7

55

Temperature inside the

box(⁰C)

Hot side temperature (⁰C) Time(min)

27.5 29 0

26 36.4 1.5

24.6 44.1 2.5

24 50.2 3

23.5 51.1 3.25

22.9 52.0 4

22.5 52.4 4.25

22 52.8 5

21.6 53.1 5.3

21.2 53.7 6.1

20.8 54.1 7

20.6 54.9 7.5

20.2 55.2 8.4

20 56 9.1

19.9 56.6 9.29

19.8 57.1 10.02

19.7 57.9 10.23

19.6 58.1 10.44

19.5 58.5 10.4

19.3 59.1 11.5

19.2 59.2 12.19

19.1 59.2 13.27

19 59.3 14.23

18.9 59.3 15.01

18.8 59.3 15.44

18.7 59.3 17.08

18.6 59.3 17.49

18.5 59.3 18.47

18.4 59.3 20.18

18.3 59.3 21.22

18.2 59.3 25.00

56

Thermoelectric cooler testing with only one module (Module A) in operation (

PERFORMED ON 2ND MARCH 2015)

Voltage to cooler=12V

Current to cooler=8.4A

Input power to cooler=100.8W

Fan voltage=11V

Fan current=0.59A

Ambient temperature=24.8⁰C

Temperature inside the box(⁰C) Time(min)

24.8 0

24.2 1

23.7 2

23.2 3

22.7 4

22.3 5

21.9 6

21.6 7

21.3 8

21.1 9

21.0 10

20.9 11

20.7 12

20.6 13

20.5 14

20.5 15

20.4 16

20.4 17

Thermoelectric cooler testing with only one module (Module B) in operation.

Voltage to cooler=12V

57

Current to cooler=9.2A

Input power to cooler=110.4W

Fan voltage=11V

Fan current=0.59A

Ambient temperature=24.3⁰C

Temperature inside the box(⁰C) Time(min)

24.3 0

24.3 1

24 2

23.6 3

23.3 4

23.2 5

23 6

22.9 7

22.8 8

22.7 9

22.6 10

22.5 11

22.5 12

22.5 13

THERMOELECTRIC COOLER OPERATION WITH PARTITIONED BOX:

Volume of the partition in operation=25*37*30cm³=32190 cm³

Voltage to cooler=12V

Current to cooler=16.3A

Input power to cooler=195.6W

Fan voltage=11V

58

Fan current=0.58A

Ambient temperature=25.5⁰C

Temperature inside the box(⁰C) Time(min)

25.5 0

24.8 1

23.1 2

21.3 3

20.1 4

19.1 5

18.4 6

17.9 7

17.4 8

17.1 9

16.8 10

16.6 11

16.5 12

16.3 13

16.2 14

16.1 15

16.0 16

15.9 17

15.8 18

15.8 19

15.8 20

15.7 21

15.6 22

15.6 23

15.6 24

15.5 25

59

FIGURE 31: TEMPERATURE DEPENDANCE CURVE (A)

CONCLUSION: 9.3⁰C difference in temperature achieved in 25 minutes.

FIGURE 32: TEMPERATURE DEPENDANCE CURVE (B)

CONCLUSION: Achieved a temperature difference of 4.4⁰C in 16 minutes, with only

one module (Module A) in operation.

0

5

10

15

20

25

30Ti

me

(min

)

1.5 3 4 5

6.1

7.5

9.1

10

.02

10

.44

11

.5

13

.27

15

.01

17

.08

18

.47

21

.22

Temperature inside the box when both modules are in operation

Temperature inside the box(⁰C)

0

5

10

15

20

25

30

Tim

e(m

in) 0 1 2 3 4 5 6 7 8 9

10

11

12

13

14

15

16

Temperature inside the box when only one module is in operation

Temperature inside the box(⁰C)

60

FIGURE 33: TEMPERATURE DEPENDANCE CURVE (C)

CONCLUSION: A temperature difference of 10⁰C was obtained in 25 minutes, for an

input of 195.6W to the thermo electric cooler assembly

05

1015202530

Temperature inside the box when the total volume of the box is reduced to half

Temperature inside the box(⁰C)

61

CHAPTER 5

PROJECT EXPENDITURE

62

5.PROJECT EXPENDITURE

EQUIPMENT EXPENSE

255W FLEXIBLE PV PANEL Rs.1,00,000/-

TEC1-12715 Rs.12,000/-

REGULATOR CIRCUIT+

MISCELLANEOUS COSTS

Rs.1,060/-

Total Rs.1,13,060/-

63

CHAPTER 6

RESULTS AND CONCLUSION

64

6. RESULTS AND CONCLUSION

RESULTS:

Solar panel: We have obtained maximum voltage of 46.8V at open circuit test

4.9 amps for short circuit test. The maximum power is obtained at 26.4 volts with 4

amps. All these results are referred to the Photovoltaic panel of 255 watts under the

conditions of solar intensity being 1350 W/m2 for an ambient temperature of 34.1⁰ C.

Peltier device: After correct isolation of each individual module we have observed a

temperature drop of 9.3⁰in 25 minutes. Upon reducing the volume of the box by

approximately half, we have obtained a temperature drop of 10⁰ in 25 minutes.

CONCLUSION:

From the above results we can conclude that the reliability of the peltier

module available in India is less with unsatisfactory level of cooling.

Thus more research is required in the cooling module design with high quality

Peltier modules to be made available from U.S or Europe.

If such changes are made than the rate of satisfactory results will surely

increase with reliability.

The general system is simple to design yet performance of the entire system is

yet to be realized.

Due to certain abnormalities we were unable to successfully interface the

regulator circuit with the TEC and the solar panel.

In addition to this, a 255W solar panel is insufficient to power an air

conditioning system, especially in automobiles. Therefore, more research is

needed in the development of efficient photovoltaic material.

Furthermore, other factors like shading and effective mounting also hinder the

performance of the PV system.

65

CHAPTER 7

FUTURE SCOPE AND

DEVELOPMENT

66

7. FUTURE SCOPE AND DEVELOPMENT

The prototype can be made compact by selecting as single TEC of higher power (.i.e.

of 200W or more). It can be done by choosing a better cold side heat sink that has

twisted channels or pipes for circulating the air for a longer time. As an alternative for

normal axial fan used in this project, if a blower fans is selected, the cooling system

would provide better airflow. Well-known TEC brands (.i.e. Melcor, FerroTECetc)

must be chosen if there is only one high power TEC selected for the cooling system.

Bigger hot side heat sinks have to be selected accurately based its calculated. thermal

resistances for best cooling efficiency. With a single TEC, one hot side and a cold side

heat sink a smaller personal TEC cooler which gives comfort can be fabricated and

can be installed on roof for individual cooling by changing the airflow and some

mechanical or electronics section modification, the TEC air cooling for car can be

used for heating applications too.

Research is being carried out into the development of efficient photovoltaic material

such as thin film and multicrystalline cells. In addition to this, multiple junction solar

cells have been known to vastly improve the performance of the system. It ensures

that the majority of the solar spectrum is utilized.

67

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