SOLAR REFRIGERATOR USING PELTIER MODULE

Page | 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 resources takes a serve 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.

Conventional cooling systems such as those used in refrigerators utilize 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 thermos electric refrigerator (also known as Peltier refrigerator)
offer several advantages over conventional systems.

The object of this study is to design and develop a working thermo-electric refrigerator
interior cooling volume of 5 litres that utilizes the Peltier effect to refrigerate and maintain
selected temperature from 160C to 270C. In most of rural areas of our country, the electric
supply is either available or not available at all time. The most severe effect of this problem is
on the Primary health care centres (PHC’s). Due to no electricity, most of the PHC’s do not
maintain adequate supply to medicines and equipment which need to be kept in a cold
environment. So, in case of any emergency, the patient is to refer either to the town or city
hospital which results in loss of precious time and money.

So, this project is intended at the development of a solar based compressor free mini fridge
(refrigerator). 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 battery will maintain the continuous
power in case of non-availability of solar power. They can be extremely compact, much more
so than compressor-based systems. However, their efficiency is low compared to
conventional refrigerators.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 2

1.1 COMPARISION BETWEEN COMPRESSOR BASED REFRIGERATION

APPLIENCE AND THERMOELECTRIC REFRIGERATION APPLIENCE:

Compressor Based Refrigeration Appliances:

A compressor-based system is typically comprised of four main parts: the compressor, the
condenser, the expansion valve and the evaporator. Additionally, certain models may also
come equipped with fans, which circulate the air and allow for even cooling. The
compressor’s job is to pressurize the gas, while the condenser radiates heat into the
environment. Once the refrigerant hits the expansion valve, its pressure is reduced, which
turns it into liquid form. Finally, the evaporator absorbs heat from the air, resulting in the
cold air that is used to properly cool the content of your refrigeration appliance.
Thermoelectric Refrigeration Appliances:
These units operate based off of two pieces of metal that are fused together, with each side
being made of different materials. These are typically referred to as ‘cooling nodes.
Essentially, one side of the joined metal gets hot, while another gets cold as an electric
current is sent through them. The hot side is basically a heat sink, allowing heat to pass
through and dissipate on its own.

These devices are based off of what is known as the Peltier effect, and while there don’t have
to be any moving parts involved, interior and exterior fans are typically used to help increase
air circulation, as well as ventilation. An internal fan will circulate cool air inside of the
refrigeration cabinet, while an external fan will help dissipate heat outside of the unit.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 3

SOLAR PANNEL

2.1 BASIC THEORY OF SOLAR PANELS:

2.1.1 SOLAR CELLS:

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.

SOLAR PV CELL
There is an electric field from the N-side to P-side of the depletion region. Since the electrons
are negative charges this electric field applies a force to an electron entering the depletion.
Any electron generate by sun light in the vicinity of the depletion may pass to the N-side of
the junction very easily. If we connect a wire or any load between the end of N-type and P-
type region with a metal contact, 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
electron in the P-type region to enter depletion region. Solar radiation is an excellent energy
source to do this job.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 4

WORKING OF SOLAR PV CELL

2.1.2 SOLAR CELL CHARACTERISTICS:

a) Theory of V-I Characteristics:

PV cell can be modelled as a current source in parallel with a diode. When there is a no light
present to generate any current, the PV cell behaves like a diode. As the intensity of incident
light increases, current is generating by PV cell, as illustrate in fig

V-I Curve of PV Cell and Associated Electrical Diagram

In an ideal cell, the total current I is equal to the current It generate by the photoelectric effect
minus the diode current ID, according to the equation:

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 5

Where I0 is a saturation current of the diode, q is the elementary charge 1.6×10-19 columns, k
is a constant of value 1.38×10-23 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 resistance that are described in further detail later in
this document:

V Io

Simplified Equivalent Circuit Model for a Photovoltaic Cell

The V-I curve of an illuminated PV cell has the shape shown in fig 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 section below.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 6

Illuminated V-I Sweep Curve

b) Short circuit current (Isc)

The short circuit current Isc corresponds to the short circuit condition when independence 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 = It for forward-bias power quadrant

c) Open circuit voltage (Voc)

The Open circuit voltage Voc occur 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

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 7

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 V-I sweep by the
equation P=VI. 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.

Maximum Power for an V-I Sweep

e) Efficiency

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/m2), with the surface area of the solar cell [m2]. 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 V-I 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.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 8

2.2 CONSTRUCTION AND WORKING OF SOLAR PANELS:

Working of solar panel

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.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 9

Structure of Solar Panel

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

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 10

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
cell.
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 ADVANTAGES AND DISADVANTAGES OF SOLAR POWER:

ADVANTAGES:

1. Solar power is pollution free and causes no greenhouse gases to be emitted after
installation.
2. Reduced dependence on foreign oil and fossil fuels.
3. Renewable clean power that is available every day of the year, even cloudy days
produce some power.
4. Return on investment unlike paying for utility bills.
5. Virtually no maintenance as solar panels last over 30 years.
6. Creates jobs by employing solar panel manufacturers, solar installers, etc. and in turn
helps the economy.
7. Excess power can be sold back to the power company if grid intertied.
8. Ability to live grid free if all power generated provides enough for the home /
building.
9. Can be installed virtually anywhere; in a field to on a building.
10. Use batteries to store extra power for use at night.
11. Solar can be used to heat water, power homes and building, even power cars.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 11

12. Efficiency is always improving so the same size solar that is available today will
become more efficient tomorrow.

DISADVANTAGES:

1. High initial costs for material and installation and long ROI.
2. Needs lots of space as efficiency is not 100% yet.
3. No solar power at night so there is a need for a large battery bank.
4. Some people think they are ugly (I am definitely not one of those!).
5. Devices that run on DC power directly are more expensive.
6. Depending on geographical location the size of the solar panels varies for the same
power generation.
7. Cloudy days do not produce much energy.
8. Lower production in the winter months.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 12

PELTIER MODULE

3.1 PELTIER HISTORY:

Early 19th century scientists, Thomas See beck and Jean Peltier, first discovered
the phenomena that are the basis for 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 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 thermoelectric continue to be
developed each day.

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 ceramic substrates provide
the platform for the pellets and the small conductive tabs that connect them.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 13

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.

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 supplied.
These refrigerators are not overly popular because they have a low coefficient of
performance.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 14

3.4 PELTIER EFFECT

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

two different conductors. His great experimental discovery was the heating or
cooling of the junctions in a circuit of metals according to the direction in which
an electric current is made to pass round 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.

Thermoelectric cooling uses the Peltier effect to create a heat flux between the
junctions of two different types of materials. A Peltier cooler, heater, refrigerator
is a solid-state device which transfer heat from one side of device to other, which
consumption of electrical energy, depending on the direction of current.

The Peltier devices are used either for heating or for cooling, although in practice
the main application is cooling. It can also use as temperature controller that
either heats or cool.
When electromotive current is made to flow through an electronic junction
between two conductors (A and B). 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. Some of the junctions lose heat due to the Peltier effect, while others
gain heat.

The Peltier effect can be considered as the back-action counterpart to the See
beck effect (analogous to the back-emf in magnetic induction): if a simple
thermoelectric circuit is closed then the See beck effect will drive a current,
which in turn (via the Peltier effect) will always transfer heat from the hot to the
cold junction.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 15

3.5 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 See beck Effect- is the reverse of the
Peltier Effect. By applying heat to two different conductors a current can be
generated. The See beck Coefficient is given by:

x
=

dT /dx

where e 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.

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

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 16

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.

Thermoelectric Component

3.6 METHOD OF HEAT TRANSPORT

⚫ Electrons can travel freely in the copper conductors but not so freely in
the semiconductor.
⚫ 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.
⚫ 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.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 17

⚫ 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.
⚫ 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.
⚫ To increase heat transport, several p type or n type thermoelectric (TE)
components can be hooked up in parallel.
⚫ However, the device required low voltage and therefore, a large current
which is too great to be commercially practical.

Peltier plate

⚫ The TE components can be put in series but the heat transport abilities are diminished
because the interconnecting’s between the semiconductor creates thermal shorting.

Peltier plate

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 18

⚫ 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.
⚫ One side is attached to a heat source and the other a heat sink that
convicts the heat away.
⚫ The side facing the heat source is considered the cold side and the side facing the heat
sink the hot side.

Heat absorption and rejection

⚫ A cooling component based on Peltier modules is often called an

active Peltier cooler, or simply a Peltier cooler.
⚫ 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.
⚫ The electrical insulator must also have a high thermal conductivity so
that the temperature gradient between the source and the conductor is small.
⚫ Ceramics like alumina are generally used for this purpose.
⚫ The most common devices use 254 alternating p and n type TE devices.
⚫ The devices can operate at 12-16 V at 4-5 amps. These values are much
more practical for real life operations.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 19

Heat absorption and rejection

⚫ Heat sinks almost always need to be fan cooled to have a sufficiently low thermal
resistance.
⚫ Using p and n-semiconductors in thermoelectric refrigerator Joining large number of n
and p semiconductor junctions creates cooling elements - Peltier modules of significant
capacity. The structure of a semiconductor Peltier module.
⚫ 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.

3.7 AN ENTIRE ASSEMBLY:

Assembly of Peltier plate

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 20

The Peltier module is a thermoelectric refrigerator that consists of coupled p- and n-type
semiconductors, which constitute p-n- and n-p-junctions. Each junction has heat contact with
one of two heatsinks. If an electric current of a certain polarity passes through the junction,
the temperature between the heatsinks in the Peltier module will drop One heatsink will work
as a refrigerator, and the other will generate and remove the heat. When the cold side of the
Peltier module is joined to the surface of the object being protected, this module acts as a heat
pump. This heat pump moves the heat from this object to the hot side of the module, which is
cooled by air or water. Like any heat pump, it can be described by thermodynamic formulas.
Therefore, Peltier modules can be called not only thermoelectric, but also thermodynamic
modules.

3.8 WHY IS TE REFRIGERATOR USED FOR COOLING?

⚫ 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 makes them useful for applications where size or weight is a
constraint.

⚫ Ability to alternate between heating and cooling.

⚫ Excellent cooling alternative to vapor compression refrigerator.

3.9 WHICH INDUSTRIES USE TE COOLING?

⚫ Electronic

⚫ Medical

⚫ Aerospace

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 21

⚫ telecommunications

3.10 WHAT ARE SOME APPLICATIONS?

⚫ Electronic enclosures

⚫ Laser diodes

⚫ Laboratory instruments

⚫ Temperature baths

⚫ Refrigerators

⚫ Telecommunication 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 ADVANTAGES AND DIS ADVANTAGES OF PRLTIER

MODULE
ADVANTAGES

1. No moving parts and environment friendly

2. Small and lightweight
3. Maintenance-free
4. Acoustically silent and electrically ―quiet
5. Heating and cooling with the same module (including temperature
cycling)

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 22

DISADVANTAGE

1. Able to Dissipate Limited amount of heat flux.

2. Less efficient the VCR system.

3. Relegated to the Low Heat flux applications.

4. More total heat to remove than without a TEC.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 23

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.

SOLAR CHARGE CONTROLLER

A solar charge controller manages the power going into the battery bank from the
solar array. Some charge controllers are available with additional capabilities like
lighting and load control, but managing the power is its primary job.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 24

4.1 Function of Solar Charge Controller:

The most essential charge controller basically controls the device voltage and opens the
circuit, when the battery voltage ascents to a certain level. More charge controllers utilized
a mechanical relay to open or short the circuit.

These operated by making a connection directly from the solar array to the battery bank.
During bulk charging, when there is a continuous connection from the array to the battery
bank, the array output voltage is ‘pulled down’ to the battery voltage. As the battery
charges, the voltage of the battery rises, so the voltage output of the solar panel rises as
well, using more of the solar power as it charges.
As a result, you need to make sure you match the nominal voltage of the solar array
with the voltage of the battery bank. Note that when refer to a 12V solar panel, that
means a panel that is designed to work with a 12V battery. The actual voltage of a
12V solar panel, when connected to a load, is close to 18Vmp (volts at maximum
power). This is because a higher voltage source is required to charge a battery. If the
battery and solar panel both started at the same voltage, the battery would not charge.

4.2 12V Solar panel with solar charge controller charging to a 12v batterry:

The solar charge controllers can also control the reverse power flow. The charge controllers
can distinguish when no power is originating from the solar panels and open the circuit

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 25

separating the solar panels from the battery devices and then reverse current will flow.

4.3 Features of Solar Charge Controller:

⚫ Protects the battery (12V) from over charging

⚫ Reduces system maintenance and increases battery lifetime

⚫ Auto charging indicator

⚫ 10A to 40A of charging current

⚫ Monitor the reverse current flow

4.4 APPLICATION:

In recent days, the process of generating of electricity from sunlight is having more
popularity than other alternative sources and they do not require high maintenance. The
following are some examples where solar energy is utilizing.
⚫ Solar street lighting system

⚫ Solar home system

⚫ Solar water pump system

⚫ Hybrid system

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 26

BATTERY

Collection of one or more electrochemical cells in which stored chemical energy is converted
into electrical energy.

5.1 RATING:

12V, 12AH Battery.

5.2 CALCULATION OF BATTERY CHARGING CURRENT & BATTERY

CHARGING TIME:

Rating of our battery is given by 12V, 12AH battery

Charging time TC= AH /A

Where

TC - Time in hour

AH - Ampere hour rating of battery

A - Current in Ampere

For 12V, 12AH, dry cell battery:

Charging current:

Battery charging current should 10% of the AH rating of battery

12AH of 10%

12 × 10/100 = 1.2A

Here the 1.2A having some losses then we can take +1 or +2 A will be added

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 27

Then the current will be 2.2A

Then Tc will be given as

Tc = AH / A = 12/2.2 = 5.45 hours (theoretical)

In practical every battery having 40% of losses

Then

12AH of 40%

12× 40/100 = 4.8

Then adding 12 and 4.8

12 + 4.8 =16.8AH

Then Tc will give as

Tc = 16.8/2.2 = 7.63 hours

Therefore, a 12V 12AH battery would take 7.63hours to fully charge, in case of charging
current of 2.2A

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 28

5.3 TYPE OF BATTERY USED:

5.3.1 DRY CELL BATTERY:

There are several types of dry cells they are

1.ZINC-CARBON BATTERY:

Zinc and carbon are used in all regular or standard AA, C and D dry-cell batteries. The
electrodes are made of zinc and carbon, with a paste of acidic material (ammonium chloride
and zinc chloride) between them serving as the electrolyte.

2. ALKALINE BATTERY:

This chemistry is common in AA, C and D dry cell batteries. The cathode is composed of a
manganese dioxide mixture, while the anode is a zinc powder. It gets its name from the
potassium hydroxide electrolyte, which is an alkaline substance.

3. LITHIUM BATTERY:

These batteries are used in cameras for the flash bulb. They are made with lithium, lithium-
iodide and lead-iodide. They can supply surges of electricity for the flash.

4. LITHIUM-ION BATTERY:

Lithium chemistry is often used in high-performance devises, such as cell phones, digital
cameras and even electric cars. A variety of substances are used in lithium batteries, but a
common combination is a lithium cobalt oxide cathode and a carbon anode.

5. NICKLE-CADMIUM (Ni Cad) BATTERY:

The Ni Cad system requires 10 series cells to reach a potential of 12V DC.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 29

TEMPERATURE SENSOR

Temperature is an important parameter in many control systems. Here we are using

W1209 digital temperature sensor /controller/thermostat switch.

The W1209 is an incredibly low cost at highly functional temperature sensor. With
the W1209 digital temperature controller you can intelligently control power to most type of
electrical device based on the temperature sensed by the included high accuracy NTC
temperature sensor. Although this module has an embedded micro controller no programming
knowledge id required. The 3 mini switches allow for changing temperature and setting the
temperature by pressing SET button and the display will flash use + and - to set the target
temperature. The temperature will be saved after two seconds. The relay can switch up to a
maximum of 240V AC at 5A or 14V DC at 10A. The 3-digit segment displays the current
temperature in degrees centigrade and the current relay state is displayed by an LED

TEMPERATURE SENSOR

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 30

6.1 SPECIFICATIONS:

Temperature control range : -50 ~ 110 C

Input voltage : 12V DC

Static current : <= 35 mA

Current : <= 65mA

6.2 ADVANTAGES AND DISADVANTAGES OF W1209 TEMPERATURE

SENSOR

ADVANTAGES:

⚫ High accuracy

⚫ Wide operation range

⚫ Suitability for precious applications

⚫ Stable output for a long period of time

DISADVANTAGE:

⚫ Higher initial cost

⚫ Less rugged in high vibration environments

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 31

MATERIALS USED

In this project, various equipment’s and materials are used for the proper functioning
and performance of the fridge. These equipment’s and materials are as follows:

7.1 PRLTIER UNIT:

PELTIER UNIT

It is the main equipment in this project by giving 12V DC supply to it. The power
rating of the Peltier module is 72W.

7.2 HEAT SINK COOLING FAN:

HEAT SINK FAN

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 32

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 ddissipate 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.

7.3 BATTERY:

The battery used in this fridge has following specifications:

⚫ 12V DC
⚫ 12 Ampere hours

BATTERY

Collection of one or more electrochemical cells in which stored chemical energy is converted
into electrical energy. In this we are using dry cell.

7.4 SOLAR CHARGE CONTROLLER:

The batteries used in the fridge are rated at 12 volts DC, 12 Ah. To charge these
batteries from the solar panel, a charge controller rated 12 volts, 10 amps is used.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 33

SOLAR CHARGE CONTROLLER

7.5 THARMACOL BOX:

In this project the thermal box is used as a refrigerator. As we know the ice
vendors take advantage of thermacoal 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.

THARMACOL BOX

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 34

BASIC CIRCUIT OF A REFRIGERATOR

The circuit diagram of the circuitry of the refrigerator is as shown in the following
figure.

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 and 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.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 35

WORKING OF REFRIGERATOR

9.1 REFRIGERATOR:

1. The refrigerator is provided power supply from a 12V DC 12AH battery.

2. To start the refrigerator, the switch is turned on.
3. When the switch is turned on, then we conclude that the refrigerator is now online.
4. Now two Peltier thermoelectric devices which are insulated from the cooling side and
arranges in the refrigerator generates cooling effects on inner side and heat is dissipated
on outer side.
5. 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.
6. 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 time.
7. To turn off the refrigerator, switch can be turned off.

9.2 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.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 36

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 Unit (1) Rs. 1600

2. Peltier Unit (2) Rs. 700

3. Solar Panel (40 watts) Rs. 2200

4. Battery (12V,20AH) Rs. 1650

5. Temperature Sensor/Controller Rs. 300

6. Solar charge Controller Rs. 750

7. Thermacoal box Rs. 100

8. Wire Rs. 500

Total Rs. 7800

As shown in the above table, the total cost of the project is Rs. 7800. In this
total cost, solar panels accounts for the major portions while the overall
individual cost of the fridge is Rs. 5600.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 37

ADVANTAGES, DISADVANTAGES AND APPLICATIONS

ADVANTAGES:

1. An interchange of heating and cooling process can be exercised just by reversing the
polarity.

2. The weight of the refrigerator is lower than the conventional refrigerator.

3. This is much more flexible than conventional system.

4. Suitable for lower capacity.

5. Can operate in any position.

6. No moving parts.

7. No leakage problems.

8. Noiseless operation.

9. Compact in size.

10. Very long life.

11. More reliable.

12. Have no vibrations.

13. These are environment friendly.

DISADVANTAGES:

1. It is in efficient.

2. High initial cost.

3. Cloudy days do not produces much energy.

4. Lower solar production in the winter months.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 38

5. If the components of peltier devices are cooled too much, it can results in condensation,
which may cause a short circuit.

APPLICATIONS:

1. For preservation of insulin and other drugs.

2. For preservation of food stuffs.

3. For cold water.

4. For beverages.

5. Road side / highway side shops having no electric supply then this solar refrigerator is
used.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 39

RESULTS

The aim of the development of the refrigerator is to provide efficient and

effective cooling in the designated locations and places. As observed from the
data above, this refrigerator 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, Refrigerator will
remain operational for the time period of 3.2 hours after which the battery will
be discharged and the temperature inside the refrigerator 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 refrigerator 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.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 40

CONCLUSION

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
refrigerator and this has been successfully done. The applications of this
refrigerator are very wide and it can be used in various places for variety of
operations. Also, the main purpose for which this refrigerator is made is being
fulfilled as the space inside the refrigerator is sufficient enough to cool
appropriate amount of medicines and injections needed at the primary health
care centers in the villages where there is sporadic or no power supply.
Though this refrigerator is working satisfactorily to its full capacity, still many
changes and improvements can be done in this refrigerator 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 refrigerator. Same refrigerator can be used for
heating purpose if we also insulate the other side i.e. heating side of the
refrigerator within the box.
• To increase the volume of the refrigerator maintaining the same
temperature inside the refrigerator, number of Peltier units and heat sink
has to be increased.
• This refrigerator can also be equipped with a digital temperature sensor
so that the temperature inside the fridge can be monitored.
• In this project, this refrigerator is made up of Thermocouple.

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020

SOLAR REFRIGERATOR USING PELTIER MODULE
Page | 41

REFERENCES

• Wikipedia https://en.wikipedia.org/wiki/Main_Page
• www.peltie-info.com
• Astrain D and Vain J G (2005), “Computational Model for Refrigerators Based on
Peltier Effect Application”, Applied Thermal Engineering.
• Roy J Dossal (2002), Principles of Refrigeration, Vol.2

SIR C.R.REDDY COLLEGE OF ENGINEERING EEE DEPT 2019-2020