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PROJECT REPORT
ON
DESIGN OF MINI COMPRESSORLESS
SOLAR POWERED REFRIGERATOR
Submitted to the:
DEPARTMENT OF ELECTRICAL ENGINEERING
COLLEGE OF TECHNOLOGY
GOVIND BALLABH PANT UNIVERSITY OF AGRICULTURE & TECHNOLOGY
PANTNAGAR - 263145, U.S.NAGAR, UTTARAKHAND, INDIA
Submitted By:
Ashok Kapoor Girish Gupta Ilina Choudhary Kanika Sharma
Id No. 42192 Id No. 42206 Id No. 42209 Id No. 42199
Under the guidance of:
Dr. Ravi Saxena Assistant Professor
Department of Electrical Engineering
FOR THE PARTIAL FULFILLMENT OF THE DEGREE
BACHELOR OF TECHNOLOGY
(ELECTRICAL ENGINEERING)
JUNE 2015
Page Number 2
ACKNOWLEDGEMENT
We wish to express our deep sense of gratitude to Dr. Ravi Saxena, Assistant
Professor, Department of Electrical Engineering, College of Technology, G.B. Pant
University of Agriculture & Technology, Pantnagar for his inspiring guidance,
meticulous counsel, constructive criticism and generous gift of time he has devoted,
which enabled us to carry out the project successfully.
We are thankful to Dean, College of Technology for providing us with the opportunity
and necessary funds and materials for the development of this project.
We would also like to thank the Department of Electrical Engineering, College of
Technology for providing us the opportunity to develop this project.
We are also thankful to Dr. A. K. Pratihar, Professor, Department of Mechanical
Engineering, College of Technology for his advice and help for this project.
We are highly indebted to our parents for their constant encouragement and support
during our studies.
We are honestly thankful to our friends for their help during the preparation of our
project.
Last but not the least, we are thankful to all those who helped us directly or indirectly
in this endeavour.
Ashok Kapoor
Id No. 42192
Girish Gupta
Id no. 42206
Ilina Choudhary
Id No. 42209
Kanika Sharma
Id no. 42199
Page Number 3
CERTIFICATE
This is to certify that the project entitled, ”DESIGN OF MINI
COMPRESSORLESS SOLAR POWERED REFRIGERATOR” which is being
submitted by Mr. Ashok Kapoor (Id No. 42192), Ms. Kanika Sharma (Id No.
42199), Mr. Girish Gupta (Id No. 42206), Ms. Ilina Choudhary (Id No. 42209) is a
record of students own work carried by them under my guidance and supervision in
partial fulfillment for the degree of BACHELOR OF TECHNOLOGY in
ELECTRICAL ENGINEERING from College of Technology, Govind Ballabh Pant
University of Agriculture & Technology, Pantnagar.
The matter presented in this project has not been submitted for the award of any other
degree, diploma or certificate
June 22, 2015 Dr. Ravi Saxena
College of Technology Project Guide
G.B.P.U.A. &T. Assistant Professor
Pantnagar Department of Electrical Engineering
Page Number 4
DECLARATION
We, the undersigned, declare that the project entitled ―DESIGN OF MINI
COMPRESSORLESS SOLAR POWERED REFRIGERATOR‖, being
submitted for the partial fulfillment of the degree of BACHELOR OF
TECHNOLOGY in ELECTRICAL ENGINEERING from College of
Technology, G.B. Pant University of Agriculture & Technology, Pantnagar is
the work carried out solely by us.
ASHOK KAPOOR KANIKA SHARMA
(Id No. 42192) (Id No. 42199)
GIRISH GUPTA ILINA CHOUDHARY
(Id No. 42206) (Id No. 42209)
Page Number 5
APPROVAL
The project work entitled ―DESIGN OF MINI COMPRESSORLESS SOLAR
POWERED REFRIGERATOR ― is hereby approved as creditable and good
work carried out and presented in a satisfactory manner to warrant its
acceptance to the pre requisite to the degree for which it has been submitted.
1. Dr. Sudha Arora
Head & Professor
Electrical Engineering Department
2. Dr. Ajay Srivastava
Professor
Electrical Engineering Department
3. Dr. Ravi Saxena
Assistant Professor
Electrical Engineering Department
4. Dr. Abhishek Yadav
Associate Professor
Electrical Engineering Department
5. Mr. H.S. Rawat
Assistant Professor
Electrical Engineering Department
6. Mr. Shobhit Gupta
Assistant Professor
Electrical Engineering Department
7. Mr. Sunil Singh
Assistant Professor
Electrical Engineering Department
8. Dr. Rajeev Singh
Assistant Professor
Electrical Engineering Department
Page Number 6
TABLE OF CONTENTS
TITLE PAGE
NO.
CHAPTER 1: INTRODUCTION 10
CHAPTER 2: BASIC THEORY OF SOLAR PANELS AND
PELTIER UNITS
12
2.1 Solar Cells 12
2.2 Solar Panels 17
2.3 Peltier Unit 19
2.4 Solar Charge Controller 21
CHAPTER 3: MATERIALS USED 23
3.1 Peltier Unit 23
3.2 Cooling Fan 23
3.3 Heat Sink 24
3.4 Insulation Material 24
3.5 Battery 25
3.6 On-Off Switch 26
3.7 Solar Charge Controller 27
CHAPTER 4: CONSTRUCTION AND DESIGN 28
4.1 Design Of The Fridge 28
4.2 Steps In Construction Of Project 29
4.3 Circuit Diagram Of Fridge 29
CHAPTER 5: WORKING OF THE PROJECT 31
5.1 Fridge 31
5.2 Battery Charging 31
CHAPTER 6: OBSERVATIONS 32
6.1 Graphical Representation 34
Page Number 7
6.2 Battery Charging 34
6.3 Electrical Measurements 34
CHAPTER 7: COST ANALYSIS 36
CHAPTER 8: RESULTS 37
CHAPTER 9: CONCLUSION AND FUTURE SCOPE 38
Page Number 8
SL.
NO.
NAME OF THE FIGURES PAGE
NO.
1 Solar PV Cell 12
2 Working of Solar PV Cell 13
3 I-V Curve of PV Cell and Associated Electrical
Diagram
13
4 Simplified Equivalent Circuit Model for a Photovoltaic
Cell
14
5 Illuminated I-V Sweep Curve 15
6 Maximum Power for an I-V Sweep 16
7 Working of Solar Panel 17
8 Structure of Solar Panel 18
9 Structure of a Peltier Unit 19
10 Peltier unit 20
11 Peltier unit in fridge 23
12 Cooling Fan 23
13 Heat Sink 24
14 Themocol 25
15 Aluminium Foil 25
16 Battery 26
17 On/Off Switch 26
18 Charge Controller 27
19 Working Model of the Fridge 28
20 Circuit Diagram 30
21 Working Fridge with temperature monitoring 32
22 Graph between Temperature V/s Time 34
List of Figures
Page Number 9
List of Tables Sl.no. Name of the Table Page No. 1 Readings Table 33
2 Cost Table 36
Page Number 10
CHAPTER 1
INTRODUCTION
Electricity generation is the leading cause of industrial air pollution in the
country. Most of our electricity comes from coal, nuclear, and other non-
renewable power plants. Producing energy from these resources takes a severe
toll on our environment, polluting our air, land.
Renewable energy sources can be used to produce electricity with fewer
environmental impacts. It is possible to make electricity from renewable energy
sources without producing CO2.
Renewable energy is energy derived from natural resources that replenish
themselves over a period of time without depleting the Earth's resources. These
resources also have the benefit of being abundant, available in some capacity
nearly everywhere, and they cause little, if any, environmental damage. Energy
from the sun, wind, and thermal energy stored in the Earth's crust are examples.
For comparison, fossil fuels such as oil, coal, and natural gas are not renewable,
since their quantity is finite once we have extracted them they will cease to be
available for use as an economically-viable energy source. While they are
produced through natural processes, these processes are too slow to replenish
these fuels as quickly as humans use them, so these sources will run out sooner
or later.
So this project is intended at the development of a solar based compressor free
mini fridge. This fridge will be suitable for cooling purposes meant for small
objects and will have a relatively small chilling time as compared to the normal
refrigeration systems. Also for the backup, this fridge will be attached to a
dynamo based charging system which will maintain the smooth operation of
fridge in case of non-availability of solar power.
In most of the rural areas of our country, the electric supply is either
sporadically available or not available at all. The most severe effect of this
problem is on the Primary Health Care Centres. Due to no electricity, most of
the PHC’s do not maintain adequate supply of medicines and equipment which
need to be kept in a cold environment. So in case of any emergency, the patient
is to be referred either to the town or city hospital which results in loss of
precious time and may prove fatal for the patient.
Page Number 11
Large areas of many developing countries have no grid electricity. This is a
serious challenge that threatens the working of PHC Centre. The main
alternatives to electrically powered refrigerators available for many years—
kerosene and gas-driven refrigerators are plagued by problems with gas supply
interruptions, low efficiency, poor temperature control, and frequent
maintenance needs. There are currently no kerosene- or gas-driven refrigerators
that qualify under the minimum standards established by the World Health
Organization (WHO) Performance, Quality, and Safety (PQS) system.
Page Number 12
CHAPTER 2
BASIC THEORY OF SOLAR PANELS AND
PELTIER BASED FRIDGE
2.1 Solar Cells
2.1.1 Silicon Solar PV Cells
When we bring p-type and n-type material together, diffusion occurs on the
surface between them. Electrons start to diffuse from n-type to p-type.
Similarly, holes diffuse from p-type region to n-type region. This diffusion
creates an electron-hole free region in a very short distance at the interface
region. This thin layer is called depletion region.
There is an electric field from the n-side to the p-side of the depletion region.
Since the electrons are negative charges this electric field applies a force to an
electron entering the depletion region. Any electron generated by sun light in
the vicinity of the depletion region may pass to the n-side of the junction very
easily. If we connect a wire or any load between the ends of n-type and p-type
region with metal contacts, this electron will flow to the p-type through this
external load. So we need an external energy to create this current: something
should energize the electrons in the p-type region to enter depletion region.
Solar radiation is an excellent energy source to do this job.
Fig 1 Solar PV Cell
Page Number 13
2.1.2 Solar Cell Characteristics
a) Theory of I-V Characterization
PV cells can be modelled as a current source in parallel with a diode. When
there is no light present to generate any current, the PV cell behaves like a
diode. As the intensity of incident light increases, current is generated by the
PV cell, as illustrated in Figure 3.
In an ideal cell, the total current I is equal to the current Iℓ generated by the
photoelectric effect minus the diode current ID, according to the equation:
Fig 3 I-V Curve of PV Cell and Associated Electrical
Diagram
Fig 2 Working of Solar PV Cell
Page Number 14
where I0 is the saturation current of the diode, q is the elementary charge 1.6 x
10-19
Coulombs, k is a constant of value 1.38 x 10-23
J/K, T is the cell
temperature in Kelvin, and V is the measured cell voltage that is either produced
(power quadrant) or applied (voltage bias). A more accurate model will include
two diode terms; however, we will concentrate on a single diode model in this
document.
Expanding the equation gives the simplified circuit model shown below and the
following associated equation, where n is the diode ideality factor (typically
between 1 and 2), and RS and RSH represents the series and shunt resistances that
are described in further detail later in this document:
The I-V curve of an illuminated PV cell has the shape shown in Figure 3 as the
voltage across the measuring load is swept from zero to VOC, and many
performance parameters for the cell can be determined from this data, as
described in the sections below.
Fig. 4 Simplified Equivalent Circuit Model for a
Photovoltaic Cell
V Io
Page Number 15
Fig. 5 Illuminated I-V Sweep Curve
b) Short Circuit Current (ISC)
The short circuit current ISC corresponds to the short circuit condition when the
impedance is low and is calculated when the voltage equals 0.
I (at V=0) = ISC
ISC occurs at the beginning of the forward-bias sweep and is the maximum
current value in the power quadrant. For an ideal cell, this maximum current
value is the total current produced in the solar cell by photon excitation.
ISC = IMAX = Iℓ for forward-bias power quadrant
c) Open Circuit Voltage (VOC)
The open circuit voltage (VOC) occurs when there is no current passing through
the cell.
V (at I=0) = VOC
VOC is also the maximum voltage difference across the cell for a forward-bias
sweep in the power quadrant.
VOC= VMAX for forward-bias power quadrant
d) Maximum Power (PMAX), Current at PMAX (IMP), Voltage at PMAX (VMP)
The power produced by the cell in Watts can be easily calculated along the I-V
sweep by the equation P=IV. At the ISC and VOC points, the power will be zero
and the maximum value for power will occur between the two. The voltage and
current at this maximum power point are denoted as VMP and IMP respectively.
Page Number 16
Fig. 6 Maximum Power for an I-V Sweep
e) Efficiency (η)
Efficiency is the ratio of the electrical power output Pout, compared to the solar
power input, Pin, into the PV cell. Pout can be taken to be PMAX since the solar
cell can be operated up to its maximum power output to get the maximum
efficiency.
Pin is taken as the product of the irradiance of the incident light, measured in
W/m2 or in suns (1000 W/m
2), with the surface area of the solar cell [m
2]. The
maximum efficiency (ηMAX) found from a light test is not only an indication of
the performance of the device under test, but, like all of the I-V parameters, can
also be affected by ambient conditions such as temperature and the intensity and
spectrum of the incident light. For this reason, it is recommended to test and
compare PV cells using similar lighting and temperature conditions.
Page Number 17
2.2 SOLAR PANELS
The diagram above illustrates the operation of a basic photovoltaic cell, also
called a solar cell. Solar cells are made of the same kinds of semiconductor
materials, such as silicon, used in the microelectronics industry. For solar cells,
a thin semiconductor wafer is specially treated to form an electric field, positive
on one side and negative on the other. When light energy strikes the solar cell,
electrons are knocked loose from the atoms in the semiconductor material. If
electrical conductors are attached to the positive and negative sides, forming an
electrical circuit, the electrons can be captured in the form of an electric current
that is, electricity. This electricity can then be used to power a load, such as a
light or a tool.
A number of solar cells electrically connected to each other and mounted in a
support structure or frame is called a photovoltaic module. Modules are
designed to supply electricity at a certain voltage, such as a common 12 volts
system. The current produced is directly dependent on how much light strikes
the module.
Fig. 7 Working of Solar Panel
Page Number 18
Multiple modules can be wired together to form an array. In general, the larger
the area of a module or array, the more electricity that will be produced.
Photovoltaic modules and arrays produce direct-current (dc) electricity. They
can be connected in both series and parallel electrical arrangements to produce
any required voltage and current combination.
Today's most common PV devices use a single junction, or interface, to create
an electric field within a semiconductor such as a PV cell. In a single-junction
PV cell, only photons whose energy is equal to or greater than the band gap of
the cell material can free an electron for an electric circuit. In other words, the
photovoltaic response of single-junction cells is limited to the portion of
the sun's spectrum whose energy is above the band gap of the absorbing
material, and lower-energy photons are not used.
One way to get around this limitation is to use two (or more) different cells,
with more than one band gap and more than one junction, to generate a voltage.
These are referred to as "multi junction" cells (also called "cascade" or
"tandem" cells). Multi junction devices can achieve higher total conversion
efficiency because they can convert more of the energy spectrum of light to
electricity.
A multi junction device is a stack of individual single-junction cells in
descending order of band gap (Eg). The top cell captures the high-energy
photons and passes the rest of the photons on to be absorbed by lower-band-gap
cells.
Fig. 8 Structure of Solar Panel
Page Number 19
Much of today's research in multi junction cells focuses on gallium arsenide as
one (or all) of the component cells. Such cells have reached efficiencies of
around 35% under concentrated sunlight. Other materials studied for multi
junction devices have been amorphous silicon and copper indium diselenide.
2.3 Peltier Unit
2.3.1 Peltier History
Early 19th century scientists, Thomas Seebeck and Jean Peltier, first discovered
the phenomena that are the basis for today’s thermoelectric industry. Seebeck
found that if you placed a temperature gradient across the junctions of two
dissimilar conductors, electrical current would flow. Peltier, on the other hand,
learned that passing current through two dissimilar electrical conductors, caused
heat to 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 devices became feasible. With
modern techniques,
We can now produce thermoelectric ―modules‖ that deliver 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 continue to be developed each day.
2.3.2 Peltier Structure
A typical thermoelectric module consists of an array of Bismuth Telluride
semiconductor pellets that have been ―doped‖ so that one type of charge
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 ceramic substrates provide the platform for the
pellets and the small conductive tabs that connect them.
Fig. 9 Structure of a Peltier Unit
Page Number 20
2.3.3 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 heat 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. 10 A Peltier Unit
2.3.4 Mounting Methods
When a direct current is passed through a Peltier Module, the low temperature
side absorbs heat and the high temperature side emits heat, so that a temperature
difference exists across the surfaces. However, since the heat emitted is more
reactive to the amount of electricity input into the module than the heat
absorbed, if a direct current is continuously passed through the module the
emitted heat will exceed the absorbed heat and both sides of the unit will
become hot. For that reason, it is necessary to connect the module to a radiator
such as aluminium fins to efficiently disperse the emitted heat.
2.3.5 Advantages of Peltier Unit
No moving parts and environment friendly
Small and lightweight
Maintenance-free
Acoustically silent and electrically ―quiet‖
Heating and cooling with the same module (including temperature
cycling)
Wide operating temperature range
Highly precise temperature control (to within 0.1 °C)
Page Number 21
2.4 Solar Charge Controller
A charge controller, charge regulator or battery regulator limits the rate at
which electric current is added to or drawn from electric batteries. It prevents
overcharging and may protect against overvoltage, which can reduce battery
performance or lifespan, and may pose a safety risk. It may also prevent
completely draining ("deep discharging") a battery, or perform controlled
discharges, depending on the battery technology, to protect battery life. The
terms "charge controller" or "charge regulator" may refer to either a stand-alone
device, or to control circuitry integrated within a battery pack, battery-powered
device, or battery recharge.
Simple charge controllers stop charging a battery when they exceed a set high
voltage level, and re-enable charging when battery voltage drops back below
that level. Pulse width modulation (PWM) and maximum power point tracker
(MPPT) technologies are more electronically sophisticated, adjusting charging
rates depending on the battery's level, to allow charging closer to its maximum
capacity.
A charge controller with MPPT capability frees the system designer from
closely matching available PV voltage to battery voltage. Considerable
efficiency gains can be achieved, particularly when the PV array is located at
some distance from the battery. By way of example, a 150 volt PV array
connected to an MPPT charge controller can be used to charge a 24 or 48 volt
battery. Higher array voltage means lower array current, so the savings in
wiring costs can more than pay for the controller.
Charge controllers may also monitor battery temperature to prevent overheating.
Some charge controller systems also display data, transmit data to remote
displays, and data logging to track electric flow over time.
Solar charge Controllers are basically of two types:
2.4.1 Stand-alone charge controllers Charge controllers are sold to consumers as separate devices, often in
conjunction with solar or wind power generators, for uses such as RV, boat, and
off-the-grid home battery storage systems. In solar applications,
charge controllers may also be called solar regulators. Some
charge controllers / solar regulators have additional features, such as a low
voltage disconnect (LDV), a separate circuit which powers down the load when
the batteries become overly discharged (some battery chemistries are such that
over-discharge can ruin the battery).
Page Number 22
A series charge controller or series regulator disables further current flow
into batteries when they are full. A shunt charge controller or shunt regulator
diverts excess electricity to an auxiliary or "shunt" load, such as an electric
water heater, when batteries are full.
2.4.2 Integrated charge controller circuitry Circuitry that functions as a charge regulator controller may consist of several
electrical components, or may be encapsulated in a single microchip an
integrated circuit (IC) usually called a charge controller IC or charge control IC.
Charge controller circuits are used for rechargeable electronic devices such as
cell phones, laptop computers, portable audio players, and uninterruptible power
supplies, as well as for larger battery systems found in electric vehicles and
orbiting space satellites.
Page Number 23
CHAPTER 3
MATERIALS 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:
3.1 Peltier Unit
The peltier unit used in this fridge is TIC 12073. This unit works on 5 volts DC
and takes maximum current of 4 amps at full load. The power rating of this unit
is 20 watts.
3.2 Cooling Fan
We are using two Cooling fans in our refrigerator which are respectively
mounted on one heat sink each. The main purpose of a cooling fan is to
Fig. 11 Peltier Unit in Fridge
Fig. 12 Cooling Fan
Page Number 24
dissipate heat from the heat sink by taking in fresh air. The fans used in this
fridge work on 12 volts DC and draws 0.18 amps. The power consumption of
each fan is 2.16 watts.
3.3 Heat Sink
A heat sink is a passive heat exchanger that cools a device by dissipating heat
into the surrounding medium. The heat sink is generally made up of aluminium.
The heat sink used in this fridge is of the dimension 7.5cm X 8cm X 4.5 cm (L
x B x H).
3.4 Insulation Material
Two materials have been used as insulator in constructing the body of
refrigerator. For preventing air leakage proper fixing has been done. The two
materials used are given as follows:
Fig. 13 Heat Sink
Page Number 25
3.4.1 Thermocol
As we know the ice vendors take advantage of thermocol for its economic value
and good insulation property as it does not allow the inner temperature of
cooling medium to go down. Hence it is also an economic source of insulation.
3.4.2 Aluminium foil
Aluminium foil is widely used for thermal insulation (barrier and reflectivity),
heat exchangers (heat conduction) and cable liners (barrier and electrical
conductivity). In this fridge aluminium foil plays two roles. First as it is on the
inner side of the fridge, it helps in keeping the fridge cool. Second it prevents
the inner side of the fridge to become wet
3.5 Battery
The battery used in this fridge has following specifications:
12 volt DC
7.5 ampere hour
Fig. 15 Aluminium foil
Fig. 14 Thermocol
Page Number 26
In this fridge one battery is used as a time for the working of the fridge. Also the
extra connections for the second battery in the fridge are also provided if more
cooling is required.
3.6 On-Off Switch
JSJSDOKW
An on/off toggle switch has been used in the fridge for having the control over
the power supply being given to the fridge. This switch is rated at 6 amps.
Fig. 16 Battery
Fig. 17 On/Off switch
Page Number 27
3.7 Solar Charge Controller
The batteries used in the fridge are rated at 12 volts DC, 7.5 Amphrs. To charge
these batteries from the solar panel, a charge controller rated 12 volts, 10 amps
is used as shown in the figure.
Fig. 18 Charge Controller
Page Number 28
CHAPTER 4
CONSTRUCTION AND DESIGN
4.1 Dimensions of the fridge
1. Outer Dimensions
Length: 30 cm
Breadth: 20 cm
Height: 21 cm (including the stands)
2. Inner Dimensions
Length: 25.5 cm
Breadth: 15.5 cm
Height: 8 cm
3. Volume of the fridge 3.162 Litres
Fig. 19 Working Model of the fridge
Page Number 29
4.2 Steps in the construction of the fridge
Firstly a box of thermocol is made of given dimensions and then the inner
walls of the box are covered with the aluminium sheet and the outer walls
by the chart paper.
The taping of the box from outer side is done so as to provide mechanical
support and blocking of air.
The two Peltier units are well placed in the two holes made in the box and
kept on the heat sink with hot side attached to the heat sink surface and
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 the thermocol box. So, the
hot side of peltier unit is unable to affect the temperature inside the box.
All the electrical connections are made putting a switch for on/off and a
LED as an indicator whether the fridge is working or not. Two batteries
each of 12 Volts DC, 7.5 Ah are connected in parallel with the peltier
units connected in series 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
user.
4.3 Circuit Diagram of the Fridge
The circuit of the fridge is made quite simple and convenient so that in case of
any fault, it can be easily dissembled and can be repaired without any major
changes to the design. The two peltier units are used in series with each other
connected to the 12 volt DC supply. The cooling fans mounted on the heat sink
are connected in parallel with the power supply of 12 DC volts. A switch is
placed in the incoming positive dc supply and an LED along with a 1 Kilo-ohm
resistance is placed after the switch in parallel with the supply. The circuit
diagram of the circuitry of the fridge is as shown in the following figure.
Page Number 30
As shown in the above circuit diagram, this fridge electrical connection with the
other equipments is made in the manner described.
-
Fig. 20 Circuit Diagram
Page Number 31
CHAPTER 5
WORKING OF THE PROJECT
5.1 Fridge
The fridge is provided power supply form a 12 volt DC 7.5 amphrs
battery.
To start the fridge, the switch on the fridge is turned on.
When the switch is turned on, a led starts glowing indicating that the
fridge is now online.
Now two Peltier thermoelectric devices which are insulated from the
cooling side and arranges in the fridge generates cooling effect on inner
side and heat is dissipated on outer side.
On the heat side of the peltier unit, a heat sink along with the fan works to
dissipate 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 fried, switch can be turned off. Then the glowing led will
also stop glowing indicating no power for the fridge.
5.2 Battery charging
The batteries used in the fridge are charged from the solar panels using a charge
controller rated 12volts, 10 amps. The battery is connected to the charge
controllers which get supply from the solar panels and feeds it to the battery.
Page Number 32
CHAPTER 6
OBSERVATIONS
For evaluating the performance of our mini compressor-less solar fridge we
tested it using a Fluke multimeter - 287 and data is recorded. Afterwards graph
was prepared for the same by taking the data from the multimeter.
As shown in the above figure, it can be observed that the refrigerator is
operational as led is glowing. Also in the background the multimeter is showing
the temperature inside the refrigerator simultaneously in the real time.
The following observations were recorded using the Multimeter:
Fig. 21 Working Fridge with temperature monitoring
Page Number 33
As shown in the table, from the readings given following observations can be
made:
Starting temperature: 30.9 °C
Starting time: 26 minutes 2 seconds
Final stable temperature: 16.9 °C
Final time: 48 minutes 8 seconds
In the above, the temperature corresponds to the value taken inside the fridge
using the temperature sensor of the Multimeter. Also from the table it is clear
about the start logging instance and stop logging instance of the Multimeter.
Table 1 Readings Table
Page Number 34
6.1 Graphical representation
From the above data it can be seen that the temperature variation is from 31 °C
to 16.9 °C in 22 minutes giving us the temperature difference between
surrounding and the box inside equal to 15 °C.
6.2 Battery Charging
From this charge controller, a single battery of the above rating charges in
approximately 40 minutes. So the two batteries are charged in 1 hour 20
minutes.
6.3 Electrical Measurements
The fridge is kept operational for the time period of 20 minutes for the readings
and the observations. Regarding the electrical readings of the current, voltage
Fig. 22 Graph between Temperature V/s Time in Real time
Page Number 35
and power being drawn by the fridge, a Multimeter is used for measuring all the
quantities. From the readings, following observations were made:
Voltage Supply (V): 12 Volt DC
Voltage across peltier unit (V1): 6 Volts DC
Current drawn from the battery (I): 2.2 Amps
Power of one peltier unit (P1): V1 x I = 6 x 2.2 = 13.2 Watts
Total power of fridge: P1 x 2 = 13.2 x 2 = 26.4 watts
So from the above readings, it can be concluded that this fridge total power
input is 26.4 watts.
As one battery is of 84 watts, this fridge can works for continuous 3.2 hours
when the battery is fully charged.
Page Number 36
CHAPTER 7
COST ANALYSIS
The cost analysis for this project is done as follows. All the components along
with the miscellaneous cost are included in the total cost of this fridge.
Sl. No. Name of the Material / Equipment Cost
1. Peltier Units (x2) Rs. 600
2. Batteries (x2) Rs. 1500
3. Solar Panel (100 watts) Rs. 6000
4. Cooling fans (x2) Rs. 100
5. Heat sink (x2) Rs. 200
6. Solar charge Controller Rs. 600
7. Insulation material Rs. 200
8. Box building material Rs. 100
9. Wiring material Rs. 100
10. Digital thermometer Rs. 100
Total Rs. 9500
Table 2 Cost Table
As shown in the above table, the total cost of the project is Rs. 9500. In this
total cost, solar panels accounts for the major portions while the overall
individual cost of the fridge is Rs. 3500.
In the mass production of the fridge, the overall cost of the fridge will be
reduced substantially making it cheap and economical for the user. Also with
the same solar panels, multiple units of the fridge can be attached making it
more cost effective in nature.
Page Number 37
CHAPTER 8
RESULTS
The aim of the development of the fridge is to provide efficient and effective
cooling in the designated locations and places. As observed from the data
above, this fridge is capable of maintaining an inner temperature of 16.5 oC after
20 minutes of continuous power supply and is maintaining it at a constant rate.
Also when the battery will be fully charged, Fridge will remain operational for
the time period of 3.2 hours after which the battery will be discharged and the
temperature inside the fridge will increase at a very slow rate due to the
insulation provided.
On the basis of the above data it can be said that the above fridge can be easily
used for the small chilling operations where cooling is required in a small time.
This system is provided with a solar panel charge controller which can be easily
used to charge the battery from the solar panels. In addition the battery charger
which runs on normal 220 volt ac supply is provided which can be used to
charge the batteries.
Page Number 38
CHAPTER 9
CONCLUSION AND FUTURE SCOPE
Solar power nowadays is playing a major role in meeting the energy
requirements of our country. It is being developed at a very fast rate and its
applications in many areas are being explored. The fridge is intended at
exploring the same and provides an efficient and economical solution to the
areas where there is no electricity and cooling is required.
This project main objective was to develop a mini compressor less solar fridge
and this has been successfully done. The applications of this fridge are very
wide and it can be used in various places for variety of operations. Also the
main purpose for which this fridge is made is being fulfilled as the space inside
the fridge is sufficient enough to cool appropriate amount of medicines and
injections needed at the primary health care centres in the villages where there
is sporadic or no power supply.
Though this fridge is working satisfactorily to its full capacity, still many
changes and improvements can be done in this fridge to make it more users
friendly and sophisticated in nature. This measures and changes, if implemented
can play an important role in the future models to be developed. Some of these
measures and changes are:
Number of peltier units can be increased to further decrease the
temperature inside the fridge. Same fridge can be used for heating
purpose if we also insulate the other side i.e. heating side of the fridge
within the box.
To increase the volume of the fridge maintaining the same temperature
inside the fridge, number of peltier units and heat sink has to be
increased.
PID controllers can be used for making it a temperature controlled fridge.
This fridge can also be equipped with a LCD display and digital
temperature sensor so that the temperature inside the fridge can be
monitored.
In this project, this fridge is made up of Thermocol and aluminium foils.
Wooden material can be used to make this fridge mores sturdy in
constructions. Wood will also act as an additional insulator for the
cooling compartment.
Page Number 39
REFERENCES
1. www.allaboutcircuits.com 2. www.hometoelectricals.com
3. www.peltie-info.com
4. Horway J B (1961), ―The Peltier Effect and Thermoelectric Transients‖,
University of Louisvill.
5. Jaspalsinh B (2012), ―A Design Method of Thermo Electric Cooler‖,
IJME, Vol. 5, No. 1, pp. 37-40.
6. Mayank Awasthi, K V Mali (2012), ―Design And Development Of
Thermoelectric Refrigerator‖, International Journal of Mechanical
Engineering and Robotics, Vol. 1, No. 3, October 2012.
Page Number 40
STUDENTS INVOLVED
Ashok Kapoor
Id No. - 42192
Phone No. - 7417479645
Email ID - [email protected]
Girish Gupta
Id No. - 42206
Phone No. - 9045412650
Email ID - [email protected]
Ilina Choudhary
Id No. - 42209
Phone No. - 7417922250
Email ID - [email protected]
Kanika Sharma
Id No. - 42199
Phone No. - 9045176090
Email ID - [email protected]
