All about Peltier plate refrigerator for project with using renewable energy syatem, like windmill, hand wheel & solar panel

1. “Renewable Energy Based Refrigeration System”
INSTITUTE OF TECHNOLOGY GOPESHWAR
(KOTHIYALSEN, CHAMOLI)
A project report submitted
In Partial fulfillment of the requirements
For the degree of
BACHELOR OF TECHNOLOGY
By
S PARVEEN SINGH (151340104026)
PRASHANT RAN (151340104023)
PRAKASH SINGH (151340104022)
NITIN ARYA (151340104020)
RAHUL SINGH (151340104024)
Under the supervision of
Mr. AJAY KUMAR
Assistant professor
To the
DEPARTMENT OF MECHANICAL ENGINEERING
UTTRAKHAND TECHNICAL UNIVERSITY
MAY, 2019

2. i
CERTIFICATE
This is certified that S PARVEEN SINGH, PRASHANT RANA, PRAKASH SINGH, NITIN
KUMAR ARYA, RAHUL SINGH RAWAT has carried out the project work presented in
this project entitled “Renewable Energy Based Refrigeration System” a report submitted
in partial fulfillment of the requirement for degree of Bachelor Of Technology from Institute
Of Technology Gopeshwar under my supervision. The project report embodies results of
original work, and studies are carried out by the student himself and the contents of the
project report do not form the basis for the award of any other degree to the candidates or to
anybody else from this or any other University/Institution.
Signature
Mr. Ajay Kumar
(Assistant Professor)
Date:

3. ii
ABSTRACT
Solid-state cooling and power generation have long been sought after as a solution for
challenge thermal management and energy problems and, to address some of these issues,
thermoelectric module have been available for decades. The core component of a
thermoelectric module is a thermocouple. A thermocouple consist of two dissimilar
semiconductors (referred to a p-type and n-type to describe dissimilar electrical conduction
mechanisms in the two material) connected together by a metal plate.
Electric connection at the top complete an electric circuit. Thermoelectric cooling (TEC)
occurs when current is supplied, in which case the thermocouple cools on one side and heats
on the other by what is known as the Peltier effect. Thermoelectric generation (TEG) occurs
when the couple is put in a thermal gradient (i.e., the top is hotter than the bottom), in which
case, the device generates current, converting heat energy into electrical power by what is
known as the Seebeck effect.
Also a hand wheel is used which is connect to alternator. The hand wheel is used for charging
the battery by the man power with increase the effectiveness of the refrigeration system. It
maintains the refrigeration system in the working condition in cloudy together weather when
it is difficult to charge the battery.
The AC source can also be used by using the voltage regulating circuit. The voltage
regulating circuit reduces the 220v to the 120volt for the input of the thermoelectric module
and fan.
This Project Report provide a review of refrigeration and research and recent research into
the development and application of alternative technologies to reduce energy consumption
and greenhouse gas emissions. With the us of thermoelectric cooling emission CFC’s and
other green house gases is highly reduced due to the use of thermoelectric module. So in this
we are not using any compressor or pump that’s why the frictional power lost is highly
reduced. Refrigerator is more robust and compact in size.
As the Mechanical Engineer I am trying to overcomes these demerits by modifying the
existing solar refrigeration system be newly emerging thermoelectric couple or cooler which
works on peltier and see beck effect. Thermoelectric cooling can be considered as one of the
major applications of the thermoelectric module (TEM) or thermoelectric coolers (TEC). The
main objective of this project is to design a cooling system.

4. iii
ACKNOWLEDGEMENT
We express our gratitude to our supervisor Mr. Ajay Kumar, Assistant Professor
Department of Mechanical Engineering, under whose supervision and guidance, this work
has been carried out. Without his whole hearted involvement, advice and constant
encouragement throughout, it would have been impossible to carry out this project work with
confidence and complete the same well in time.
We would like to thank all faculty members and the lab staff of the department who have
been extremely kind and helpful to us during our project work and motivated us from time to
time to perform level best.
We find no words to thank all my friends who made delightful and pleasurable period that we
will cherish forever. We would love to dedicate this report to our parents, whose constant co-
operations, affection and well wishes have encouraged us throughout our endeavors. Finally,
we are thankful for the availability of the invaluable resource at the Institute of Technology
Gopeshwar, Chamoli that has made this everything possible. At last, but not the least we
thank each and every one who helped us directly or indirectly in carrying out this project.

5. iv
TABLE OF CONTENT
Contents Page no.
Certificate i
Abstract ii
Acknowledgement iii
Contents iv-vi
List of figure vii
Nomenclature viii
Chapter-1 Introduction 1-6
1.1 General 1
1.2 Peltier plate refrigeration 2
1.3 What is seebeck effect...? 3
1.4 Peltier effect 4
1.5 Renewable energy sources 5
1.5.1 Windmill 5
1.5.2 Solar energy 5
1.5.3 Hand wheel 6
1.6 Objective 6
Chapter-2 Literature survey 7-21
2.1 Method of refrigeration 7
2.2 Thermo-electric refrigeration 7
2.2.1 Peltier History 7
2.3 Harmful effect of refrigeration 8
2.3.1 Global warming 8
2.4 Importance of non-conventional energy resources 10
2.5 Conventional energy resources 10
2.5.1 Fossil fuel plant 10
2.5.2 Nuclear Power plant 11
2.5.3 Hydroelectric power plant 11
2.5.4 Biomass plant 11
2.6 Unconventional energy resources 11
2.6.1 Wind energy 11

6. v
2.6.1.1 Types of wind turbine 12
2.6.1.2 Effect due to variation of wind speed 12
2.6.1.3 Wind energy application 13
2.6.1.4 Merits 13
2.6.1.5 Limitations 13
2.6.1.6 Blade types 13
2.6.2 Solar panel 13
2.6.2.1 Design specifications 15
2.6.2.2 Structure of a solar cell 15
2.6.2.3 Working of solar panels 17
2.6.2.4 Solar panel types 17
2.6.2.5 Solar energy applications 19
2.6.2.6 Merits and limitations 19
2.6.2.7 Limitations of solar energy 19
2.6.3 Hand wheel power 19
2.6.3.1 Working principle of hand wheel 20
2.7 Research paper survey 20
Chapter-3 Basic theory of peltier device 22-32
3.1 Peltier effect 22
3.2 Peltier structure 23
3.3 Peltier theory 24
3.4 Basic principle 24
3.5 Method of heat transport 26
3.6 Semiconductor doping 29
3.7 Coefficient of performance 31
3.8 Why is TE cooler used for cooling...? 31
3.9 Which industries use TE cooling...? 32
3.10 What are some applications...? 32
3.11 Disadvantage 32
Chapter-4 Material Used 33-39
4.1 Peltier unit 33
4.2 Cooling fan 34
4.3 Heat sink 35
4.4 Cooling box 36

7. vi
4.5 Thermal paste 36
4.6 Battery 37
4.7 Hand wheel 37
4.8 Windmill 38
4.9 Solar panel 39
Chapter-5 Construction & Working 40-42
5.1 Dimension of the fridge 40
5.2 Steps in the construction of the fridge 40
5.3 Circuit diagram 41
5.4 Working 41
5.5 DC Dynamometer 41
5.6 DC Generator 42
5.7 Coefficient of performance 42
Chapter-6 Conclusion & Future Scope 43
References 44

8. vii
LIST OF FIGURE
FIGURE PAGE NO.
Figure 1.1- Thermocouple seebeck effect 4
Figure 1.2- Peltier effect 5
Figure 2.1- Windmill 12
Figure 2.2- Solar panel 14
Figure 2.3- Structure of solar panel 17
Figure 2.4- Mono crystalline 18
Figure 2.5- Poly crystalline 18
Figure 2.6- Amorphous 18
Figure 2.7- Hand wheel 20
Figure 3.1- Structure of a peltier unit 23
Figure 3.2- A peltier unit 24
Figure 3.3- Thermoelectric component 25
Figure 3.4- Thermoelectric component 26
Figure 3.5- Peltier plate 27
Figure 3.6- Peltier plate 27
Figure 3.7- Heat absorbtion and rejection 28
Figure 3.8- Heat absorbtion and rejection 28
Figure 3.9- N type semiconductor 29
Figure 3.10- P type semiconductor 30
Figure 3.11- Plot cop versus I/Imax 31
Figure 4.1- A peltier unit 33
Figure 4.2- Cooling fan 34
Figure 4.3- Heat sink 35
Figure 4.4- Cooling box 36
Figure 4.5- Thermal paste 36
Figure 4.6- Battery 37
Figure 4.7- Hand wheel 38
Figure 4.8- Windmill 38
Figure 4.9- Solar panel 39
Figure 5.1- Circuit diagram 41

9. viii
LIST OF SYMBOL AND ABBREVIATION
GENERAL TERMS:-
SYMBOL DESCRIPTION UNIT
Cp Specific heat of air J/kg K
M Mass of air inside Kg
Qc Heat load absorb by the cold side of TEC W
Qh Amount of Heat dissipated at the hot side of TEC W
R Thermal resistant K/W
T∞ Ambient temperature o
C
Ti Initial temperature of air o
C
Tf Final temperature of air o
C
ρa Density of air kg/m3
V voltage given to TEC volt
I Current applied to TEC amp.
Keywords:-
CFC Chloro-fluro carbon
TE Thermoelectric
TEC Thermoelectric cooler
TEM Thermoelectric Module
TEA Thermoelectric assembly

10. 1
CHAPTER-1
INTRODUCTION
1.1 General
Refrigeration is the achievement of temperature below that of the local environment. The
main purpose of refrigeration is thermal conditioning (e.g. for food preservation or air
conditioning), and the basic apparatus is a refrigerator, a thermal machine producing cold.
Other names for special types of refrigerators are freezers, chillers, cryo-coolers, as well as
the informal word fridge. Small refrigerators are usually comprise the cabinet to be cooled
(e.g. the fridge), but larger refrigerators are machinery rooms outside the cold storage
(applicable to air conditioners too). Refrigeration is not only important to food storage and
transport, including slaughtering yards, fermentation cellars of breweries, ice cream
industry, fruit and vegetable stores, etc. Refrigerated spaces are need for human comfort,
animal and vegetal growth optimization, electronics and precision machinery operations,
artificial skating rinks and snow parks, etc. Sometimes, refrigeration is not intended for
space cooling but for space dehumidification, instead of desiccants, refrigeration is also
applied to case the drilling of shafts in water - logged grounds, freezing it by pumping cold
brine through a double wall along the shaft.
For domestic and industrial purpose Vapour compression Cyclic is used for refrigeration in
which any type of refrigerant is flowing through the cycle. In VCR system, refrigerants are
used like NH2, C02, etc. These refrigerant produce many hazardous effects on environment
and human being. Also, many types of problems are stored in refrigerants, leakage of the
refrigerants through the pipeline. This increase the cost of the refrigeration system. Also it
increases the global warming and ozone depletion.
The VCRs system needs electric power for the operation as an input. This
power is normally generated at power plant like Nuclear power plant, fossil fuel power
plant, Hydroelectric power plant. Each system has advantage and disadvantages, but many
of them pose environmental concern. For example, Hydroelectric Power Plant, it require
large reservoir for the storage, the water. It require continuous flow of water. Dams may
where the large reservoirs are not cleared of trees before flooding, the methane gas
released by decaying can be comparable in greenhouse effect to the CO2 emissions of a
fossil - fuel plant of similar output.

11. 2
The aim of the project is to study peltier effect, seeback Effect based on the
renewable energy sources for the refrigeration. Renewable energy effectively utilizes
natural resources such as sunlight, wind, tides and geothermal heat, which are naturally
replenished. Renewable energy is available in abundance. Peltier effect produces cooling
as well as heating. This is a replacement for the VCRs system because it does not require
any kind of refrigerant for the refrigeration.
1.2 Peltier plate refrigeration:-
Conventional cooling system such as those used in refrigerators utilizes a compressor and a
working fluid to transfer heat. Thermal energy is absorbed and released as the working
Fluid undergoes expansion and compression and changes phase from liquid to vapour and
back, respectively. Semiconductor thermoelectric coolers (also known as Peltier coolers)
offers Several advantages over conventional system. They are entirely solid-state Devices,
with no moving parts; this makes them rugged, reliable, and quiet. They use no ozone
depleting chlorofluorocarbons, potentially offering a more environmentally responsible
alternative to conventional refrigeration. They can be extremely compact, much more so
than compressor-based systems. Precise temperature control can be achieved with Peltier
coolers. However their efficiency is low compared to conventional Refrigerators. Thus,
they are used in niche applications with their unique advantages outweigh their low
efficiency. Although some large-scale applications where small size is needed and the
cooling demands are not too great, such as for cooling electronics components. The
objective of this study is to Design and Develop a working thermoelectric refrigerator
interior cooling that utilizes the peltier effect to refrigerate and maintain a selected
temperature from 5°Cto 25°C. The design requirements are to cool this volume to
temperature with a time period of 6 hrs and provide retention of at least next half an hour.
The design requirement, option available and the final design of thermoelectric refrigerator
for application are presented. From last century till now refrigeration has been one of the
most important factors of our daily life. The current tendency of the world is to look at
renewable energy resources as a source of energy. This is done for the following two
reasons; firstly, the lower quality of life due to air pollution; and, secondly, due to the
pressure of the ever increasing world population puts on our natural energy resources.
From these two facts comes the realization that the natural energy resources available will
not last indefinitely. The basic idea is implementation of photovoltaic driven refrigerating

12. 3
system powered from direct current source or solar panel (when needed) with a battery
bank. In 1821, the first important discovery relating to thermoelectricity occurred by
German scientist Thomas Seebeck who found that an electric current would flow
continuously in a closed circuit made up of two dissimilar metals, provided that the
junctions of the metals were maintained at two different temperatures. Without actually
comprehending the scientific basis for the discovery, Seebeck, falsely assumed that
flowing heat produced the same effect as flowing electric current. Later, in 1834, while
investigating the Seebeck Effect, a French watchmaker and part-time physicist, Jean Peltier
found that there was an opposite phenomenon where by thermal energy could be absorbed
at one dissimilar metal junction and discharged at the other junction when an electric
current flows within the closed circuit. Afterwards, William Thomson described a
relationship between Seebeck and Peltier Effect without any practical application. After
studying some of the earlier thermoelectric work, Russian scientists in 1930s, inspired the
development of practical thermoelectric modules based on modern semiconductor
technology by replacing dissimilar metals with doped semiconductor material used in early
experiments. The Seebeck, Peltier and Thomson effects, together with several other
phenomena, form the basis of functional thermoelectric modules. Thermoelectric
Refrigeration aims at providing cooling effect by using thermoelectric effects rather than
the more prevalent conventional methods like those using the ‘vapour compression cycle’
or the ‘gas compression cycle’.
1.3 What is Seebeck effect…???
The Seebeck effect is a phenomenon in which a temperature difference between two
dissimilar electrical conductors or semiconductors produces a voltage difference between
the two substances.
When heat is applied to one of the two conductors or semiconductors,
heated electrons flow toward the cooler one. If the pair is connected through an electrical
circuit, direct current (DC) flows through that circuit.
The voltages produced by Seebeck effect are small, usually only a few micro
volts (millionths of a volt) per Kelvin of temperature difference at the junction. If the
temperature difference is large enough, some Seebeck-effect devices can produce a few
millivolts (thousandths of a volt). Numerous such devices can be connected in series to
increase the output voltage or in parallel to increase the maximum deliverable current.

13. 4
Large arrays of Seebeck-effect devices can provide useful, small-scale electrical power if a
large temperature difference is maintained across the junctions.
Fig. 1.1 Thermocouple seebeck effect
1.4 Peltier effect
The Peltier effect is a type of thermoelectric effect that is observed in an electric circuit. It
was named after Jean Charles Athanase Peltier, the physicist who discovered the effect in
1834. Peltier discovered that when current is made to flow through a circuit consisting of
two different types of conductors, a heating or cooling effect is observed at the junctions
between the two materials. This change in temperature at the junction is called the Peltier
effect.
When electric current is passed through a circuit consisting of two different
conductors, a cooling effect is observed in one junction whereas another junction
experiences a rise in temperature. This change in temperatures at the junctions is called the
Peltier effect. The effect is found to be even stronger when two different semiconductors
are used in place of conductors in the circuit.
For example, when copper wire and bismuth wire are connected in an electric circuit, heat
is generated at the point where current passes from copper to bismuth, and a drop in

14. 5
temperature occurs where the current passes from bismuth to copper. This effect is
reversible in nature. The heating or cooling effect observed at a junction can be reversed by
changing the direction of the current flow.
The phenomenon behind the Peltier effect is used in the function of thermoelectric heat
pumps and thermoelectric cooling devices. It is also used for cooling computers and other
electronic equipment when other methods are not feasible.
Fig. 1.2 Peltier effect
1.5 Renewable energy sources
1.5.1 Windmill
A windmill is a structure that converts the energy of wind into rotational energy by means
of vanes called sails or blades. Centuries ago, windmills usually were used to mill grain
(gristmills), pump water (wind pumps), or both. There are windmills that convert the
rotational energy directly into heat.
1.5.2 Solar Energy
Solar energy is the conversion of energy from sunlight into electricity, either directly using
photovoltaics (PV), indirectly using concentrated solar power, or a combination.
Concentrated solar power systems use lenses or mirrors and tracking systems to focus a
large area of sunlight into a small beam.

15. 6
1.5.3 Hand wheel :- a wheel worked by hand. A simple machine consisting of a circular
frame with spokes (or a solid disc) that can rotate on a shaft or axle (as in vehicles or other
machines)
1.6 Objective-:
1. To study and fabrication of refrigeration device based on he Peltier effect.
2. To study and fabricate the wind mill
3. To study a solar panel.
4. To study and fabricate a hand wheel

16. 7
CHAPTER-2
LITERATURE SURVEY
To perform this study, it was necessary to understand VCRs system to generate cooling
effect. And also study about difficult power generation plant like thermal, hydro and diesel
power plant.
2.1 Methods of refrigeration
1. Non-cyclic refrigeration.
2. Cyclic refrigeration.
a) Vapour-compression cycle.
b) Vapour-absorption cycle.
c) Gas cycle.
3. Thermoelectric refrigeration.
4. Magnetic refrigeration.
2.2 Thermo-electric Refrigeration
2.2.1 Peltier History :-
The phenomena that are the basis for found that if you placed a temperature gradient across
the junction of two Dissimilar conductors, electrical current would flow. Peltier , on the
other hand , learned that passing current through two dissimilar electrical conductors,
caused heatto be either emitted or absorbed at the junction of the materials . it was only
after mid-20th century advancements in semiconductor technology , however , that
practical applications for thermoelectric, however that practical application for
thermoelectric devices became feasible .with modern techniques , We can now produce
thermos electric efficient solid state heat pumping for both cooling and heating ; many of
these units can also be used to generate DC power at reduced efficiency new and often
elegant uses for thermo –electrics continues to be developed. Peltier initially trained as a
watchmaker and was up to his 30s working as a watch dealer. Peltier worked with
Abraham Louis Breguet in Paris. Later, he worked with various experiments on
electrodynamics and noticed that in an electronic element when current flows through, a
temperature difference or temperature difference is generated at a current flow. In 1836 he
published his work and in 1838 his findings were confirmed by Emil Lenz. Furthermore,
Peltier dealt with topics from the atmospheric electricity and meteorology. In 1840, he

17. 8
published a work on the causes and formation of hurricanes. Peltier's papers, which are
numerous, are devoted in great part to atmospheric electricity, waterspouts, cyanometry
and polarization of sky-light, the temperature of water in the spheroidal state, and the
boiling-point at great elevations. There are also a few devoted to curious points of natural
history. But his name will always be associated with the thermal effects at junctions in a
voltaic circuit, a discovery of importance quite comparable with those of Seebeck and
Cumming. Peltier discovered the calorific effect of electric current passing through the
junction of two different metals. This is now called the Peltier effect (or Peltier–Seebeck
effect). By switching the direction of current, either heating or cooling may be achieved.
Junctions always come in pairs, as the two different metals are joined at two points. Thus
heat will be moved from one junction to the other.
2.3 Harmful effect of Refrigeration
2.3.1 Global Warming
The earth and its atmosphere get heated as they continuously receive sun’s energy in the
form of high frequency radiation. A major part of this heated is returned as infrared
radiation. Thus a delicate balance exist between the energy received and that returned to
the outer space. The temperature of the earth depend on this. Many gasses such as CO2,
methane (CH4), Nitrous oxide (N2O), various hydrocarbons, CFCs, HCFCs, HFCs etc, are
released by mankind due to various agriculture and industrial activities. These gases, called
“Green-house gases (GHG)”, act as a screen, blocking out part of the infrared radiation of
the earth towards outer space. Water vapour is also powerful greenhouse gas but is not
thermal as it is condensable and cannot build up atmosphere. This is the reason that HFCs,
even though are safe from the ozone depletion point of view, are increasingly being
blamed for contributing to the global warming. In fact, man and animals emit significant
amount of GHGs due to their metabolic activity. Methane is potent greenhouse gas
produced by ruminant animals, such as dairy cows. Animal agriculture is responsible for
more greenhouse gas (18%) than all of transportation (13%) according to a 2006 report of
UN-FAO. On Al Gore’s website www.climatecrisis.org, he notes””Eat less meat. Their
grassy diet and multiple stomachs cause them to produce methane, which the exhale with
every breath. “By being vegetarian, we grow plants which not only produce food but also
act as carbon sink because they consume CO2.

18. 9
Green house gasses
a) O2, N2 and most diatomic molecules are unable to absorb earth’s infrared radiation,
therefore they are not greenhouse gases.
b) The principal greenhouse gases are carbon dioxide (CO2), Water vapor (H2O),
Methane (CH4), Nitrous oxide (N2 O), choloroflurocarbons CFCs and ozone (O3).
The atmosphere is divided into layer define by the distance above the surface of earth as
follow:-
a) 0-15 kilometers (Troposphere)
b) 15-50 kilometers ( Stratosphere)
c) 50-85 kilometers ( Mesosphere)
d) >85 kilometers (Thermosphere)
It has been established that the short wavelength band of UV radiation are harmful to the
life on earth in many ways. It has also been established that a layer of the stratosphere, 20-
40 km thick and rich in ozone, filters out a major portion of this harmful UV radiation from
reaching the earth’s surface. Chemically stable choloroflurocarbon (CFC) refrigerant
molecules remain for a very long time in the atmosphere and can therefore reach the ozone
layer. In the stratospheric area an energetic UV photon strikes the CFC molecules. The
energy of impact releases a cholorine atom, which is chemically very active and reacts
with the ozone molecules. Through this interaction, the ozone molecules is destroyed. This
is complicated chain reaction leading to the ‘ozone hole’. Health and environment effect of
ozone depletion can be multifarious. Because
Biological life on this planet evolved only after the ozone shield developed, enormous
potential for harm exist if the shield is damaged. DNA, the generic code present in all
living cells is damaged by UV radiation, UVC being the most damaging. A significant
reduction in ozone in the upper atmosphere could result in long-time increase in screen
cancer and cataracts, and the probably damage the human immune system. Environment
damage and the resulting economic losses could be because of decreased yield of major
agriculture crops, and reduced productivity of phytoplankton with possible implications for
the aquatic food chain, resulting in substantial losses at the larval stage of many fish (e.g.
anchovies, shrimps and crabs). The extent of damage that a refrigerant can cause to the
ozone layer is quantified by the Ozone Depletion Potential (ODP) which is the ratio of
impact by the substance on ozone to that caused by CFC11.

19. 10
2.4 Importance of Non-Conventional Energy Resources
1. Renewable energy resources such as wind, solar, water are able to provide us with
limitless energy.
2. Renewable energy resources are the best alternatives to conventional fuels.
3. All the energy sources have one thing in common , that there are harnessed from
nature .This means that they are constantly replenished unlike the fossil fuel that is
likely to run out in years to come .These advantages of non conventional sources
more popular as compared to conventional sources.
4. Sources like Solar, tidal, wind, Water are all clean renewable energy resources,
these all produces energy without any pollution.
5. Solar energy is the main future energy resource .Throughout the history Sun has
been used for heat and light and its unlimited potential can provide electricity
enough for whole planet, Different methods have been used to harness energy from
Sun like solar panel, Solar heater, Solar cooker etc.
6. There are lots of windy areas across the globe, and in many parts of the World
people are trying to harness Wind energy as much as possible, though efficiency of
this energy Source still remains a big problem, largely because of inconsistency of
wind blowing.
7. Geothermal power is another excellent form of renewable energy system.
Geothermal energy uses the heat from deep inside the earth to produce electricity.
Various methods have been developed to do this, and the most common method is
harnessing the steam that naturally comes out of fissures on the ground.
2.5 Conventional energy sources
2.5.1 Fossil fuel plant
Most electricity today is generated by burning fossil fuels and producing steam which is
then used to drive a steam turbine that , in turn , drives an electrical generator .The World '
s supply of fossil fuels is large , but finite. Its emissions may be produced Sulfur dioxide,
No2 and other gases are often released, as well as particulate matter. Sulfur and nitrogen
oxides contribute to Smog and acid rain.

20. 11
2.5.2 Nuclear power plant
Radioactive fuels are needed for this plant .There have been serious accidents with a small
number of nuclear power stations. Storing and monitoring the radioactive waste material
.Nuclear |powered ships and submarines pose a danger to marine life and the environment.
Many Governments fear that unstable countries that develop nuclear power may also
develop nuclear weapons and even use them.
2.5.3 Hydroelectric power plant
It require large reservoir for storage the water. It required continuous flow of Water. Dams
may block the passage of river, where large reservoirs are not cleared of trees before
flooding, the methane gas released by decaying wood can be comparable in greenhouse
effect to the CO2 emissions of a fossil-fuel plant of similar output.
2.5.4 Biomass plant
Organic matter to decay, producing biogas, which is then burned. Burning biomass
produces many of the same emissions as burning fossil fuels. It uses a large amount of
land, and fertilizers and pesticides may be necessary for cost-effective growth. The above
mentioned power plant requires any kind of fuel which are conventional and non
renewable in the nature. Also the quantity of these fuel are finite in nature also these are
produces a large quantity of the pollutant gases which affect the environment.
So the aim of study is to use such type of the energy which is non-convention as mentioned
below. These are non-polluting in the nature and we use it again and again.
2.6 Unconventional energy sources
2.6.1 Wind energy:
The energy from the wind is called wind energy. The kinetic energy of the wind converted
into mechanical energy that can be utilized to perform useful work or generate electricity.
Most machines for converting Wind energy into mechanical energy consist basically a
number of sails, vanes or blades radiating from a hub or central axis. The axis may be
horizontal or vertica. When the wind blows against the vanes or sails they rotate about the
axis and the rotational motion can be made to perform useful work. Wind energy
conversion devices are known as wind turbines they convert the energy of the wind stream
into energy of rotation; the component which rotates is called the rotor. Because wind

21. 12
turbines produces rotational motion, wind energy radily converted into electrical energy by
connecting the turbine to an electric generator, A step up transmission is usually required
to match the relatively slow speed of wind rotor to the higher speed of an electric
generator.
Fig. 2.1 Windmill
2.6.1.1 Types of wind turbine
1. Horizontal axis wind turbine.
2. Vertical axis wind turbine.
2.6.1.2 Effect due to variation of wind speed
Variability is a major problem associated with wind power. If the wind is too weak, Very
little power is generated. But, if it's too strong, the large forces exerted may cause
structural damages, so many turbines shut down in high Winds. The variations in Wind
speed are often modeled statistically using a Weibullcurve. In essence, for a given annual
average Wind Speed, The Weibull curve provides an estimate of how many hours per year
the wind will be within a range of values,
In addition to day-to-day variability, Winds are rarely steady. Instead, they are almost
always gusting. This turbulence leads to two problem:
a) The electrical power output of the generator will constantly vary , requiring proper
conditioning and

22. 13
b) The continually changing forces on the blades results in fatigue loading that is the
main factor in how long a blade can be run before needing replacement.
2.6.1.3 Wind energy application:
1. Pumping application
2. Direct heat application
3. Electric generation application
2.6.1.4 Merits:
Following are the some merits of a solar energy
1. No attention is needed during energy production.
2. No fuel is required.
3. Minimum maintenance cost.
4. No pollution.
5. No production of harmful chemical.
2.6.1.5 Limitations
1. Deepened on the wind
2. The menu has to preplanned
3. Cannot produce energy during rainy days .
2.6.1.6 Blade types
1. NACA-63
2. NACA-44
3. Ply wood profile
4. Air breezer profile
5. New blade profile
2.6.2 Solar panel:
A solar panel is comprised of smaller photovoltaic cells. The word photovoltaic comes
from a combination of the ancient Greek “phos” meaning light, and “Volta“, named for
alessandro volta, an Italian physicist known for his pioneering Work in electricity. In
silicon, an element on the Periodic Table, is lie typical Semiconductor material in a

23. 14
photovoltaic cell. A Semiconductor has properties of an electric conductor (such as a
metal) at high temperatures, while it takes on the lower conductivity properties of an
insulator at temperatures. Silicon is the element most commonly used as a semiconductor
and is typically employed in electronic circuitry.
A typical silicon atom has 14 electrons (negatively charged particles) arranged in three
different shells. The outer shell is half full with four electrons. However, as atoms try to fill
their electron shells to find stability, a typical silicon atom will usually share electrons with
four other silicon atom, thereby filling the electron field and creating a crystalline silicon
molecules.
Yet, as the creation of electricity is dependent upon the movement (electrical current) of
electrons, the stability of silicon molecules is not conducive to this silicon. The release of
electrons by the application of energy is more easily done if the molecules are instable,
meaning the electron shells are not completely filled. That is why impure, or "doped"
silicon is used in the production of photovoltaic cells. This impure silicon is created
through the addition of both boron and phosphorus to the silicon molecules. This forms
unstable electron shells, which require far less energy to dislodge an electron- thereby
creating an effective electrical current. Two slices of the doped silicon are placed together
to create " sandwich,” with the boron - doped and phosphorous - doped silicon constituting
either side. This is done because the joining of these two types of silicon essentially creates
an imbalance in their charge. In a photovoltaic cell, this imbalance results in an electric
field, like a battery or a magnet, and it has a positive and negative terminal. The field
forces electrons freed by photons ( sunlight ) to move only in one direction while searching
for places to bind, The movement of electrons through this space creates a current which,
when connected to an external load, creates electricity.
Fig. 2.2 Solar Panel

24. 15
2.6.2.1 Design Specifications
• Function and Performance
a) Must be have angle adjusting capabilities ranging from 0° to 90°,
b) A manual must be provided to set up the systems for all of its need
c) The mounting system must be placed on a flat surface
d) Mounting system must be safely secured to the ground
• Safety
a) The mounting system should not tip over
b) The solar panels must be securely fastened to the mounting system
• Operating Characteristics
a) Must be able to have a Solar panel mounted on top.
• Operating Environment
a) The material used to build the mounting system needs to withstand a temperature of
-50 to 150°F
b) Must withstand a category 2 hurricane ( 96 - 110 mph )
c) It must withstand snow , ice and rain
d) Material must be corrosion resistant
• Manufacturability
a) Must be easy and cost effective fabricated
b) Must be manufactured locally
c) Must be packaged in a compact box
d) Total weigh of package should be less than 100 Ibs,
• Assembly
a) Manual must be included and have easy to understand directions
b) Easily put together by a non - engineer person .
• Durability
a) The mounting System needs to support 80 1bs
b) Should function for 20 yrs .in the environment of use
• Cost
a) Total sale cost must be less.
2.6.2.2 Structure of a Solar Cell
A typical solar cell is a multi - layered unit consisting of a

25. 16
a) Cover- a clear glass or plastic layer that provides outer protection from the
elements. Transparent Adhesive - holds the glass to the rest of the solar cell.
b) Anti- reflective Coating - this substance is designed to prevent the light that
strikes the |cell from bouncing off so that the maximum energy is absorbed into the
cell
c) Front Contact - transmits the electric current
d) N-Type Semiconductor Layer - This is a thin layer of silicon which has been
mixed process if called doping) with phosphorous to make it a better conductor.
e) P-Type Semiconductor Layer - This is a thin layer of silicon which has been
mixed or doped with boron to make it a better conductor.
f) Back Contact - transmits the electric current.
g) N-Layer - is often formed from silicon and a small amount of Phosphorus
.Phosphorus gives the layer an excess of electrons and therefore has a negative
character. The n - layer is not a charged layer- it has an equal number of protons
and electrons - but some of the electrons are not held tightly to the atoms and are
free to move.
h) P-Layer - is formed from silicon and Boron and gives the layer a positive
character because it has a tendency to attract electrons .The player is not a charged
layer and it has an equal number of protons and electrons.
i) P-N Junction- when the two layers are placed together, the free electrons from the
n-layer are attracted to the player .At the moment of contact between the two
wafers, free electrons from the n - layer flow into the player for a split second, then
form a barrier to prevent more electrons from moving from one layer to the other
.This contact point and barrier is called the p – n junction.
j) Solar or photovoltaic (PV) cells – it is made up of materials that turn sunlight into
electricity .Photovoltaic (PV) technologies including Solar thermal hot Water are
renewable energy technologies and are clean energy alternatives compared to non
renewable energy technologies that burn fossil fuels, PV cells are composed of
layers of semiconductors such as silicon. Energy is created when photons of light
from the sun strike a solar cell and are absorbed within the semiconductor material.
This excites the semiconductor's electrons, causing the electrons to flow, and
creating a usable electric current. The current flows in one direction and thus the
electricity generated is termed direct current (DC).

26. 17
One PV cell produces only one or two Watts which isn't much power for most uses .In
order to Increase power, photovoltaic or solar cells are bundled together into what is
termed a module and packaged into a frame which is more commonly known as a solar
panel .Solar panels can then be grouped into larger solar arrays.
Fig. 2.3 Structure of solar panel
2.6.2.3 Working of Solar Panels
Once the layers have been joined, there is a negative charge in the player and a positive
charge in the n - layer section of the junction. This imbalance in the charge of the two
layers at the p - n junction produces an electric field between the player and the n - layer. If
the PV cell is placed in the sun, radiant energy strikes the electrons in the p - n junction and
energizes them, knocking them free of their atoms. These electrons are attracted to the
positive charge in the n - layer and are repelled by the negative charge in the player. A wire
can be attached from the player to the n - layer to form a circuit. As the free electrons are
pushed into the n - layer by the radiant energy, they repel each other. The Wire provides a
path for the electrons to flow away from each other . This flow of electrons is an electric
current that we can observe. The electron flow provides the current, and the cell's electric
field causes a voltage. With both current and voltage, we have power, which is the product
of the two.
2.6.2.4 Solar panel types
There are three common technologies used in solar panels, all of which are based on the
common element silicon, which makes up a large proportion of the earth.

27. 18
• Mono-crystalline:- Mono-crystalline cells are made from a thin slicon or wafer cut
from a Single large crystal of silicon. The cells are then doped and the fine current
collecting wires printed on or in the surface of the cell. Generally mono-crystalline
cells have the highest efficiency, but this comes at a price, This type of cell takes
more energy to make than any other and so has a greater energy payback period,
though this is usually still within five years. A number of manufacturers make
mono-crystalline panels, including BF Solar and Sharp.
Fig. 2.4 Fig. 2.5 Fig. 2.6
Mono crystalline Poly crystalline Amourphous
• Polycerystalline:- Polycrystalline cells are made from thin wafers of silicon cut
from a large cast billet. The billet is not a large single crystal, but many crystals
clumped together, hence the name. Polycrystalline cells are usually slightly less
efficient than mono-crystalline cells, but because they are square, can be fitted into
the rectangular frame of a solar panel with high space efficiency, although
polycrystalline panels are still slightly larger than mono-crystalline panels of the
same rating. Polycrystalline cells must also have current collecting grids printed
onto them . Kyocera panels use this cell technology, as do many other panels.
• Amorphous:- Amorphous/thin film panels involve deposition of very thin films of
silicon or other materials directly onto a substrate such as glass or stainless steel,
This technique produces a cell with a lower efficiency that the cut Water varieties ,
but has the advantage of eliminating the need for inter - cell connections. Uni-Solar

28. 19
makes triple-junction, nine-layer thin-film amorphous panels with a much higher
efficiency than the older types, The layers of silicon are deposited directly onto a
stainless steel substrate and are then coated in a flexible plastic protective layer,
There are now a number of manufacturers of thin-film panels, including Uni-Solar,
Kaneka and Schott Solar.
2.6.2.5 Solar Energy Applications:
Solar energy applications are as follows:
a) Heating and cooling of residential building
b) Solar Water heating
c) Solar drying of agricultural and animal products.
d) Salt production by evaporation of seawater.
e) Solar cookers
f) Solar engines for water pumping.
g) Solar electric power generation
2.6.2.6 Merits and limitations:
Following are the some merits of a solar energy
a) No attention is needed during energy production
b) No fuel is required
c) Minimum maintenance cost
d) No pollution.
e) No production of harmful chemical
2.6.2.7 Limitations of a Solar energy
a) Deepened on the sunshine,
b) The menu has to pre-planned.
c) Cannot produce energy on night or during cloudy days.
d) It takes comparatively more time.
2.6.3 Hand wheel power
The hand wheel is attached to the alternator. An alternator is an electrical generator that
converts mechanical energy to electrical energy in the form of alternating current. For

29. 20
reasons of cost and simplicity, most alternators use a rotating magnetic field with a
stationary armature but occasionally, a rotating armature is used with a stationary magnetic
field; or a linear alternator is used. In principle, any A Electrical can be called an
alternator, but usually the term refers to Small rotating machines driven by automotive and
other internal combustion engines. An alternator that uses a permanent magnet for its
magnetic field is called a magneto.
Fig. 2.7 Hand wheel
2.6.3.1 Working Principle of Hand wheel
A conductor moving relative to a magnetic field develops an electromotive force (EMF) in
it, (Faraday's Law). This emf reverses its polarity when it moves under magnetic poles of
opposite typically, a rotating magnet, called the rotor turns within a stationary set of
conductors u in coils on an iron core, called the stator. The field cuts across the conductors,
generating an induced EMF (electromotive force), as the mechanical input causes the rotor
to turn. The magnetic field induces an AC Voltage in the stator windings. Since the current
in the stator wind generator vary in step with the position of the rotor, an alternator is a
synchronous generator. Synchronous Speed - One cycle of alternating current is produced
each time a pair of field poles passes over a point on the stationary winding. The relation
between speed and frequency is “N= 120f /P” where f the frequency in Hz is (cycles per
second). P is the no of poles (2, 4, 6 . . .) and N is the rotational speed in revolutions per
minute (RPM)
2.7 Research paper survey
1. NON - CONVENTIONAL ENERGY RESOURCES by KS sidhude scribes in
brief the non - conventional energy sources and their usage.

30. 21
2. Thermoelectric: The Seebeck Effect and Peltier Effect by Samuel Weaver
describe seeback effect and peltier effect with working of thermo electric
module.
3. A review on developments of thermoelectric refrigeration and air conditioning
systems: a novel potential green refrigeration and air conditioning technology
by Manoj Kumar Rawat and Himadri Chattopadhyay describes brief
introduction of thermoelectricity, principal of thermoelectric cooling and
thermoelectric materials and the cost - effectiveness of thermoelectric module
technology has been also discussed in this paper.

31. 22
CHAPTER-3
BASIC THEORY OF PELTIER DEVICE
3.1 Peltier effect
Peltier effect is the presence of heating or cooling at an electrified junction of two
different conductors (1834). His great experimental discovery was the heating or cooling
of the junctions in a heterogeneous circuit of metals according to the direction in which
an electric current is made to pass round the circuit. This reversible effect is proportional
directly to the strength of the current, not to its square, as is the irreversible generation of
heat due to resistance in all parts of the circuit. It is found that, if a current pass from an
external source through a circuit of two metals, it cools one junction and heats the other.
It cools the junction if it be in the same direction as the thermoelectric current which
would be caused by directly heating that junction. In other words, the passage of a current
from an external source produces in the junctions of the circuit a distribution of
temperature which leads to the weakening of the current by the superposition of a
thermo-electric current running in the opposite direction .
When electromotive current is made to flow through an electronic junction between
two conductors (A and B), heat is removed at the junction. To make a typical pump,
multiple junctions are created between two plates. One side heats and the other side
cools. A dissipation device is attached to the hot side to maintain cooling effect on the
cold side.Typically, the use of the Peltier effect as a 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 pumps exploit this
phenomenon, as do thermoelectric cooling Peltier modules found in refrigerators.
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 true importance of this "Peltier effect" in the explanation of thermoelectric currents
was first clearly pointed out by James Prescott Joule; and Sir William Thomson. further
extended the subject by showing, both theoretically and experimentally, that there is

32. 23
something closely analogous to the Peltier effect when the heterogeneity is due, not to
difference of quality of matter, but to difference of temperature in contiguous portions of
the same material. Shortly after Peltier's discovery was published, Lenz used the effect to
freeze small quantities of water by the cold developed in a bismuth-antimony junction
when a voltaic current was passed through the metals in the order named.
3.2 Peltier Structure
A typical thermoelectric module consists of an array of Bismuth Telluride semiconductor
pellets that have been carrier – either positive or negative- carries the majority of current.
The pairs of P/N pellets are configured so that they are connected electrically in series, but
thermally in parallel. Metalized ceramics substrates provide the platform for the pellets and
the small conductive tabs the connect them. Thermoelectric module are small, quiet and
heat pumps operated by a DC power source. They usually last about 200,000 hours in
heating mode and about 20 hours if left on cooling mode.
Fig.3.1- Structure of a Peltier Unit
When power is supplied, the surface where heat energy is rabsorbed become cold; the
opposite surface where heat energy is released becomes hot. If the polarity of current flow
through the module is reversed, the cold side will become the hot side and vice-versa.
Thermoelectric module can also be used as Thermoelectric modules can also be used as
thermocouples for temperature measurement or as generators to supply power to
spacecrafts and electrical equipment.

33. 24
3.3 Peltier Theory
When DC voltage is applied to the module, the positive and negative charge carriers in
the pellet array absorb heat energy from one substrate surface and release it to the
substrate at the opposite side. The surface where energy is absorbed becomes cold; the
opposite surface where heat energy is released becomes hot. Reversing the polarity will
result in Reversed Hot and Cold Sides.
Fig.3.2 A Peltier Unit
Thermoelectric devices can also be used as refrigerators on the base of the peltier effect.
To create a thermoelectric refrigerator, heat is absorbed from a refrigerated space and
then rejected to a warmer environment. The difference between these two quantities is the
net electrical work that need to be nosupplied. These refrigerators are not overly popular
because they have a low coefficient of performance.
3.4 Basic Principle
❖ Peltier Effect- when a voltage or DC current is applied to two dissimilar
conductors, a circuit can be created that allows for continuous heat transport
between the conductor’s junctions. The Seebeck Effect- is the reverse of the
Peltier Effect. By applying heat to two different conductors a current can be
generated. The Seebeck Coefficient is given by:

34. 25
where  is the electric field.
❖ The current is transported through charge carriers (opposite the hole flow or
with electron flow).
❖ Heat transfer occurs in the direction of charge carrier movement.
Fig.3.3 Thermoelectric Component
❖ Applying a current (e- carriers) transports heat from the warmer junction to the
cooler junction.
❖ A typical thermoelectric cooling component is shown on the next slide. Bismuth
telluride (a semiconductor),is sandwiched between two conductors, usually
copper. A semiconductor (called a pellet) is used because they can be optimized
for pumping heat and because the type of charge carriers within them can be
chosen. The semiconductor in this examples N type (doped with electrons)
therefore, the electrons move towards the positive end of the battery.
❖ The semiconductor is soldered to two conductive materials, like copper. When
the voltage is applied heat is transported in the direction of current flow.
❖ When a p type semiconductor (doped with holes) is used instead, the holes move
in a direction opposite the current flow. The heat is also transported in a direction
opposite the current flow and in the direction of the holes. Essentially, the charge
carriers dictate the direction of heat flow.

35. 26
Fig. 3.4- Thermoelectric component
3.5 Method of Heat Transport
1. Electrons can travel freely in the copper conductors but not so freely in the
semiconductor.
2. As the electrons leave the copper and enter the hot-side of the p-type, they must
fill a "hole" in order to move through the p-type. When the electrons fill a hole,
they drop down to a lower energy level and release heat in the process.
3. Then, as the electrons move from the p-type into the copper conductor on the cold
side, the electrons are bumped back to a higher energy level and absorb heat in the
process.
4. Next, the electrons move freely through the copper until they reach the cold side
of the n-type semiconductor. When the electrons move into the n-type, they must
bump up an energy level in order to move through the semiconductor. Heat is
absorbed when this occurs.
5. Finally, when the electrons leave the hot-side of the n-type, they can move freely
in the copper. They drop down to a lower energy level and release heat in the
process.
6. To increase heat transport, several p type or n type thermoelectric(TE)
components can be hooked up in parallel.
7. However, the device requires low voltage and therefore, a large current which is
too great to be commercially practical.

36. 27
Fig. 3.5 Peltier plate
8. The TE components can be put in series but the heat transport abilities are
diminished because the interconnectings between the semiconductor creates
thermal shorting.
Fig. 3.6 Peltier plate
9. The most efficient configuration is where a p and n TE component is put
electrically in series but thermally in parallel . The device to the right is called a
couple.
10. One side is attached to a heat source and the other a heat sink that convects the
heat away.
11. The side facing the heat source is considered the cold side and the side facing the
heat sink the hot side

37. 28
.
Fig. 3.7 Heat absorbtion and rejection
12. A cooling component based on Peltier modules is often called an active Peltier
cooler, or simply a Peltier cooler.
13. Between the heat generating device and the conductor must be an electrical
insulator to prevent an electrical short circuit between the module and the heat
source.
14. The electrical insulator must also have a high thermal conductivity so that the
temperature gradient between the source and the conductor is small.
15. Ceramics like alumina are generally used for this purpose.
16. The most common devices use 254 alternating p and n type TE devices.
17. The devices can operate at 12-16 V at 4-5 amps. These values are much more
practical for real life operations.
Fig. 3.8 Heat absorbtion and rejection
18. Heat sinks almost always need to be fan or liquid cooled to have a
sufficiently low thermal resistance.
19. Using p- and n-semiconductors in thermoelectric refrigerators
Joining large numbers of n- and p-semiconductor junctions creates cooling

38. 29
elements—Peltier modules of significant capacity. The structure of a
semiconductor Peltier module.
20. In a typical module, temperature can differ tens of degrees. If the hot side
is cooled adequately, the other side will reach negative Celsius
temperatures. To increase the temperature difference, it is possible to
cascade properly cooled Peltier modules. This method provides a simple,
reliable, and inexpensive way of obtaining a temperature difference that
will cool electronic components efficiently
3.6 SEMICONDUCTOR DOPING
N Type
N doped semiconductors have an abundant number of extra electrons to use as charge
carriers. Normally, a group IV material (like Si) with 4 covalent bonds (4 valence
electrons) is bonded with 4 other Si. To produce an N type semiconductor, Si material is
doped with a Group V metal (P or As) having 5 valence electrons, so that an additional
electron on the Group V metal is free to move and are the charge carriers
Fig.3.9 N type Semiconductor
Semiconductor materials like silicon and germanium have four electrons in their outer
shell (valence shell). All the four electrons are used by the semiconductor atom in
forming bonds with its neighbouring atoms, leaving a low number of electrons available
for conduction. Pentavalent elements are those elements which have five electrons in
their outer shell. When pentavalent impurities like Phosphorus or Arsenic are added into
semiconductor, four electrons form bonds with the surrounding silicon atoms leaving one
electron free. The resulting material has a large number of free electrons. Since electrons
are negative charge carriers, the resultant material is called N-type (or negative type)

39. 30
semiconductor. The pentavalent impurity that is added is called 'Dopant' and the process
of addition is called 'doping'.
N-Type semiconductor is manufactured by doping 'intrinsic' or pure semiconductor
material. The amount of impurity added is very small compared to the amount of
semiconductor. Characteristics and nature of the resultant semiconductor can be
controlled by controlling the quantity of 'dopant'.
P Type
For P type semiconductors, the dopants are Group III (In, B) which have 3 valence
electrons, these materials need an extra electron for bonding which creates “holes”. P
doped semiconductors are positive charge carriers. There’s an appearance that a hole is
moving when there is a current applied because an electron moves to fill a hole, creating
a new hole where the electron was originally. Holes and electrons move in opposite
directions.
Fig.3.10 P type Semiconductor
Semiconductors are most often made from silicon. Silicon is an element with four
electrons in its outer shell. To make a p-type semiconductor extra materials
like boron or aluminium are added to the silicon. These materials have only three
electrons in their outer shell. When the extra material replaces some of the silicon it
leaves a 'hole' where the fourth electron would have been if the semiconductor was pure
silicon.
P-type semiconductors are made by doping the pure semiconductor material. The amount
of impurity added is very small compared to the amount of semiconductor. The exact

40. 31
character of the semiconductor change be changed by changing the amount of 'dopant'
that is added.
3.7 Coefficient of Performance
A typical AC unit has a COP of approximately 3. TE coolers usually have COP’s
below 1; 0.4 to 0.7 is a typical range.
Below are COP values plotted versus the ratio of input current to the module’s
Imax specification. Each line corresponds with a constant DT/DTmax (the ratio of
the required temperature difference to the module's max temperature difference
specification).
Fig.3.11 Plot Cop versus I/Imax
3.8 Why is TE Cooler Used for cooling ?
❖ No moving parts make them very reliable ; approximately 10^5 hrs operation at
100 degrees Celsius , longer for lower temp ( Goldsmid , 1986).
❖ Ideal when precise temperature control is required .
❖ Ability to lower temperature below ambient .
❖ Heat transport controlled by current input .
❖ Able to operate in any orientation .
❖ Compact size make them useful for applications where size oe weight is a
constraint .

41. 32
❖ Ability to alternate between heating and cooling .
❖ Excellent cooling alternative to vapour compression coolers for system that are
sensitive to Mechanical vibraton.
3.9 Which Industries Use TE Cooling?
❖ Electronic
❖ Medical
❖ Aerospace
❖ Telecommunications
3.10 What are Some Applications?
❖ Electronic enclosures
❖ Laser diodes
❖ Laboratory instruments
❖ Temperature baths
❖ Refrigerators
❖ Telecommunications equipment
❖ Temperature control in missiles and space systems
❖ Heat transport ranges vary from a few milliwatts to several thousand watts,
however, since the efficiency of TE devices are low, smaller heat transfer
applications are more practical.
3.11 DISADVANTAGE
❖ Able to Dissipate Limited amount of heat flux.
❖ Less efficient the VCR system.
❖ Relegated to the Low Heat flux applications.
❖ More total heat to remove than without a TEC

42. 33
CHAPTER-4
MATERIAL USED
In This project, various equipments and materials are used for the proper functioning and
performance of the fridge. These equipments and materials are as follows:
• Fabrication
1. Petier chip.
2. Cooling Fan
3. Heat sink.
4. Cooling box
5. Thermal paste
6. Battery
7. Hand wheel
8. Windmill
9. Solar panel
10. Circuit diagram
4.1 Peltier Unit
Fig.4.1 A Peltier Unit

43. 34
The peltier unit in this fridge is TEC1-12706. This work on 12 volts DC and takes
maximum current of 6amps at full load. The power rating of this unit is 92 watts.
Peltier elements are used in scientific devices. They are a common component in thermal
cyclers, used for the synthesis of DNA by polymerase chain reaction (PCR), a common
molecular biological technique which requires the rapid heating and cooling of the
reaction mixture for denaturation primer annealing and enzymatic synthesis cycles.
With feedback circuitry, Peltier elements can be used to implement highly stable
temperature controllers that keep desired temperature within ±0.01 °C. Such stability may
be used in precise laser applications to avoid laser wavelength drifting as environment
temperature changes.
4.2 Cooling Fan
Fig.4.2 Cooling Fan
We are using three cooling fans in our refrigerator which are respectively mounted on
one heat sink each. The main purpose of a cooling fan is to dissipate heat from the heat
sink by taking fresh air. The fans used in this fridge work on 12 volts DC and draws
0.18amp. The power consumption of each fan is 2.16 watts.
The amount of heat produced by these peltier plate as a side-effect of normal
operation has also increased. These components need to be kept within a specified

44. 35
temperature range to prevent overheating, instability, malfunction and damage leading to a
shortened component lifespan.
While in earlier personal computers it was possible to cool most components using
natural convection (passive cooling), many modern components require more effective
active cooling. To cool these components, fans are used to move heated air away from
the components and draw cooler air over them. Fans attached to components are usually
used in combination with a heat sink to increase the area of heated surface in contact with
the air, thereby improving the efficiency of cooling.
4.3 Heat Sink
Fig.4.3 Heat sink
A Heat Sink is a passive heat exchanger that cools a device by dissipating heat into
surrounding medium. The heat sink is generally made up of aluminum The heat sink
used in this fridge is of the Dimension 8.5 x 3.2 x 7 (l X B X H).
A heat sink is designed to maximize its surface area in contact with the cooling medium
surrounding it, such as the air. Air velocity, choice of material, protrusion design and
surface treatment are factors that affect the performance of a heat sink. Heat sink
attachment methods and thermal interface materials also affect the die temperature of the
integrated circuit. Thermal adhesive or thermal grease improve the heat sink's
performance by filling air gaps between the heat sink and the heat spreader on the device.
A heat sink is usually made out of copper and/or aluminum. Copper is used because it
has many desirable properties for thermally efficient and durable heat exchangers. First
and foremost, copper is an excellent conductor of heat. This means that copper's high

45. 36
thermal conductivity allows heat to pass through it quickly. Aluminum is used in
applications where weight is a big concern.
4.4 Cooling box
Outer dimension
L=35.5cm
B=26cm
H=27cm
Plastic material is used
Inside dimension
L=30cm B=25.5cm H=22cm
Fig.4.4 Cooling box
4.5 Thermal Paste
Fig.4.5 Thermal Paste

46. 37
Thermal paste is a kind of thermally conductive (but usually electrically insulating)
compound which is commonly used as an interface between heat sinks and heat sources
(e.g., high-power semiconductor devices). The main role of thermal grease is to eliminate
air gaps or spaces (which act as thermal insulator) from the interface area so as to
maximize heat transfer. Thermal grease is an example of a thermal interface material.
Thermal grease consists of a polymerizable liquid matrix and large volume fractions of
electrically insulating, but thermally conductive filler. Typical matrix materials
are epoxies, silicones, urethanes, and acrylates, solvent-based systems, hot-melt
adhesives, and pressure-sensitive adhesive tapes are also available. Aluminum
oxide, boron nitride, zinc oxide, and increasingly aluminum nitride are used as fillers for
these types of adhesives. The filler loading can be as high as 70–80 wt %, and the fillers
raise the thermal conductivity of the base matrix from 0.17–0.3 watts per meter Kelvin or
W/(m·K), up to about 2 W/(m·K)
4.6 Battery
Fig. 4.6 Battery
Voltage Capacity-Up to 12 Volts
Current Capacity-Up to 7 amperes
4.7 Hand wheel
Radius=15cm

47. 38
Fig. 4.7 Hand wheel
4.8 Windmill
Fig. 4.8 Windmill
Max. blade length -23cm

48. 39
4.9 Solar panel
Fig. 4.9 Solar panel
Length - 30cm
Breadth - 26cm
Width - 2.5cm

49. 40
CHAPTER-5
CONSTRUCTION & WORKING
5.1 Dimension of the fridge
1. Outer Dimensions
• Length: 40cm
• Breadth: 23cm
• Height: 49cm
2. Inner Dimensions
• Length: 35.5cm
• Breadth: 18.6cm
• Height: 41.5cm
3. Volume of the fridge 27.4m
• Volume Outer: Length*Breath*Height
40*23*49=45080cm3=45.08m
• Volume inner: Length*Breath*Height
35.5*18.6*41.5=27402.45cm2=27.4m
5.2 Steps in the construction of the fridge
❖ The sealing of the box from outer side is done so as to provide mechanical
support and blocking of air .
❖ The four pettier units are well placed in the holes made in the box and kept on the
heat sink with hot slide attached to the heat sink surface ad cold side inside the
box.
❖ The heat sink is linked with a fan which is used to dissipate the heat of heat sink
into the outer atmosphere i.e. out of thermal box. so the hot side of peltier unit is
unable to effect the temperature inside the box
❖ A power supply of 12v dc is connected in parallel with the peltier units and the
two cooling fans.
❖ All the electrical connections are made strong by soldering them and all the wires
are arranged properly so as to avoid any inconvenience for the users.
❖ All renewable energy source connected to the battery in proper way.

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5.3 Circuit Diagram
Fig. 5.1 Circuit diagram
5.4 working
❖ The Fridge is provided power supply form a 12 volts battery.
❖ To start the fridge. the switch on the fridge is turned on.
❖ Now two Peltier thermoelectric devices which are insulated from the cooling side
and arranges in the fridges generates cooling effect on inner side and the heat is
dissipated on outer side.
❖ On the heat side of the peltier unit, a heat sink along with the fan works to
dissipates the heat from the peltier unit in the outer environment.
❖ The Peltier thermoelectric Device will be so arranged in a box with proper
insulation system and heat sink so that efficient cooling takes place at all the time.
❖ To turn off the fridge, switch can be turned off
❖ According to need of power or based on atmosphere, using hand wheel, windmill,
& solar panel
5.5 DC dynamometer
Specification:/
Voltage = 12 V and Current = 7 amp
Power = VI = 84 Watt
Speed = 60 rpm
P = 2πNT / 60

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84 = 2π × 60 × T /60
T = 84 / 2π = 13.36 Nm
Time period for charging the battery
t = Q / I
= 5 x 3600 / 6
= 50 min or 0.83 hours
5.6 DC Generator
Specifications
Voltage = 20 V and Current = 7amp
Speed = 60 rpm
P = VI
= 20 x 7 =140W
Now, required torque for rotating of generator about 60 rpm
P = 2 π NT / 60
T = P x 60/2πN
= 190 x 60/2π x 60
T = 22.28 Nm
Applying force by mean on the hand wheel
T = Fr
R = 15cm = 0.15m
F = T/r
= 22.8/0.15
F = 148N
5.7 Coefficient of performance
Coefficient of performance of Peltier Refrigerator is low about 0.4 to 0.75
range.

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CHAPTER-6
CONCLUSION & FUTURE SCOPE
Since Peltier chip is not efficient comparatively and due to its small size application, in is
not widely used. It found its application only in electronics cooling etc. but we have seen
that there is a use scope of research in this field about thermo electric materials, it’s
application, heat sink design etc. researcher are working on reducing irreversibilities in the
system, because Peltier chip has more potential which we can see from vast difference b/w
value of first law efficiency and second law efficiency.
So in future work, need to design the refrigeration system based on renewable energy
resource like solar energy using the peltier effect. A portable Heating & Cooling system
was fabricated using thermoelectric module & electric control unit & tested for the cooling
& heating purpose.
The coefficient of performance of this refrigerator is much smaller than that of a
convectional compressor-type refrigerator when the required cooling capacity is high,
whereas the coefficient of performance of the conventional unit falls of rapidly as the
cooling capacity is decreased and that of thermo-electric unit remains constant. Thus a
conventional a refrigerator is preferred when the require cooling capacity is high and a
thermoelectric refrigerator should be chosen when a low cooling capacity is needed. The
cold side of the thermoelectric module was utilized for refrigeration purposes whereas the
rejected heat from the hot side of the module was eliminated using heat sink and fans.
As the cooling units are small size, silent, contains no liquid or gases, have no moving
parts and have a long life. It is very simple to control the rate of cooling by adjustment of
current, the response to changes in the supply is very rapid, while reversal of the direction
of the current transforms a cooling unit into a heater with a coefficient of performance in
excess of unity i.e. a heat pump for oven. In this work, a portable compressor less
refrigerator unit was fabricated and tested for the cooling purpose.
This is completely eco-friendly project multipurpose and portable.

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References
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