REFRIGERATOR WORKING ON PELTIER

EFFECT WITHOUT COMPRESSOR

CAPSTONE PROJECT REPORT

Submitted in partial fulfillment of the requirement for award of the degree of

BACHELOR OF TECHNOLOGY

IN

MECHANICAL ENGINEERING

BY

Manas Adhikari 11102061

Imon Kalyan Goswami 11102141

Abhi Acharjee 11102060

Tamajit Datta 11106005

Under the guidance of

Mr. Puneet Sharma (Asst. Professor)

DEPARTMENT OF MECHANICAL ENGINEERING

LOVELY PROFESSIONAL UNIVERSITY

PHAGWARA, PUNJAB (INDIA) -144402

CERTIFICATE

I hereby certify that the work which is being presented in the capstone project / Dissertation

entitled “REFRIGERATOR WORKING ON PELTIER EFFECT WITHOUT

COMPRESSOR” in partial fulfillment for the award of degree of Bachelor of Technology

and submitted in Department of Mechanical Engineering, Lovely Professional University,

Punjab is an authentic record of my own work carried out during period of capstone under the

supervision of Mr. Puneet Sharma, Assistant Professor, Department of Mechanical

Engineering, Lovely Professional University, Punjab.

The matter presented in this project has not been submitted by means where for the award of

any other degree or to any other institute

This is to certify that the above statement made by the candidate is correct to best of my

knowledge.

Date: 28/04/2015 (Puneet Sharma)

Supervisor

ACKNOWLEDGEMENT

We would like to take this opportunity to thank all of the individuals who provided us with

words of knowledge, encouragement, and support through the process of my project. Without

your assistance this accomplishment would not have been possible.

Special thanks to our project mentor Puneet Sharma who provided great inspiration,

enthusiasm, and guidance during the course of the capstone project. His expertise,

knowledge, and most importantly his patience was invaluable throughout the development of

the project.

Finally, we would like to thank our families and friends for their continual love and support

during this experience.

“Thank You”

ABSTRACT

With the advent of household refrigeration system in 1910, the modification to the core

technology has been very less. The system has a compression machine designed for

continuous automatic operation and for conservation of the charges of refrigerant and oil, and

is usually motor driven and air-cooled. The compressor used is a power consuming

component. It consumes around 90% of the total rated consumption in a refrigerator.

This project emphasizes on the working of a refrigeration system which does not have a

compressor. The refrigerator has no rotary power consuming component, so the system has

greater life longevity. The working is based on Peltier cooling comprising of a Peltier

module. This is an energy efficient system consuming minimum power. Further, it also acts

as heater unit providing a localized heating. It is air-cooled system having no flow of

refrigerant. This further reduces the environmental concerns surrounding the use of

refrigerant, which has been part of great debate now-a-days. The system is solar powered.

This has been introduced as a step to have renewable source of energy.

With the shift to a sustainable environment in recent era, this project poses as an approach to

achieve it. This has the ability to be a next-gen refrigeration system for domestic use in

coming times.

CONTENTS

S.NO TITLE PAGENO

Certificate i

Acknowledgement ii

Abstract iii

List of Figures vi

1 CHAPTER 1: INTRODUCTION 1-3

1.1 Refrigeration 1

1.1.1 Non-cyclic Refrigeration 1

1.1.2 Cyclic Refrigeration 1

1.1.3 Thermoelectric Refrigeration 1

1.1.4 Magnetic Refrigeration 1

1.2 Background 2

1.3 Different Components 2

1.3.1 Major Components 2

1.3.2 Minor Components 3

2 CHAPTER 2: LITERATURE REVIEW 4-5

2.1 Introduction 4

2.2 Thermoelectric Modules 5

2.3 Development in Thermoelectric Refrigeration Systems 5

3 CHAPTER 3: PROBLEM FORMULATION 6

3.1 Scope 6

3.2 Objective 6

4 CHAPTER 4: DESCRIPTION OF THE COMPONENTS 7-20

4.1 Peltier Module 7-9

4.2 Cooling Fan 9-10

4.3 Heat Sink 10-12

4.4 Solar Cell Panel 12-14

4.5 Icebox 15-16

4.6 Battery 17

4.7 Wires 18

4.8 Two-way Switch 18-19

4.9 AC/DC Adapter 19-20

4.10 Aluminium Sheet 20

5 CHAPTER 5: DEVELOPMENT AND CONSTRUCTION 21-28

5.1 Design and Analysis 26-28

5.1.1 Design 26-27

5.1.2 Calculations/Analysis 27-28

6 CHAPTER 6: DISCUSSIONS 28-29

6.1 Advantages of Thermoelectric Refrigeration System 28

6.2 Comparison of Thermoelectric Refrigeration with other methods of

Refrigeration

28-29

7 CHAPTER 7: CONCLUSION AND FUTURE SCOPE 30

7.1 Conclusion 30

7.2 Future Scope 30

REFERENCES 30-31

LIST OF FIGURES

FIGURE

NO

TITLE PAGE

NO

1 Peltier Circuit

2 Peltier Module Structure

3 Cooling Fan

4 Heat Sink

5 Solar Panel

6 Icebox

7 Battery

8 Wires

9 Two-way Switch Circuit

10 AC/DC Adapter

11 Cut Icebox

12 Peltier Module and Heat Sink

13 Heat Sink

14 Connection between Peltier module and Fan

15 Connection of Two-way Switch

16 Battery connected to Solar Panel

17 Aluminium Sheet

18 Complete Setup

19 Model of Different Components

20 Complete Refrigerator Model

CHAPTER 1

INTRODUCTION

1.1 Refrigeration

Refrigeration is a process in which work is done to remove heat from one location to another.

Refrigeration has many applications, including household refrigerators,

industrial freezers, cryogenics, and air conditioning. Refrigeration has had a large impact on

industry, lifestyle, agriculture and settlement patterns. The idea of preserving food dates back

to the ancient Roman and Chinese empires. However, refrigeration technology has rapidly

evolved in the last century. The methods of refrigeration can be classified as non-cyclic,

cyclic, thermoelectric and magnetic processes.

1.1.1 Non-cyclic refrigeration: In non-cyclic refrigeration, cooling is accomplished by

melting ice or by subliming dry ice (frozen carbon dioxide). These methods are used for

small-scale refrigeration such as in laboratories and workshops, or in portable coolers.

1.1.2 Cyclic refrigeration: Cyclic refrigeration can be classified as:

1. Vapor cycle refrigeration, and

2. Gas cycle refrigeration

Vapor cycle refrigeration can further be classified as:

1. Vapor-compression refrigeration

2. Vapor-absorption refrigeration

1.1.3 Thermoelectric refrigeration: Thermoelectric cooling uses the Peltier effect to create

a heat flux between the junctions of two different types of materials. This effect is commonly

used in camping and portable coolers and for cooling electronic components and small

instruments.

1.1.4 Magnetic refrigeration: Magnetic refrigeration, or adiabatic demagnetization, is a

cooling technology based on the magneto-caloric effect, an intrinsic property of magnetic

solids. The refrigerant is often a paramagnetic salt, such as cerium magnesium nitrate. The

active magnetic dipoles in this case are those of the electron shells of the paramagnetic atoms.

Because few materials exhibit the needed properties at room temperature, applications have

so far been limited to cryogenics and research.

1.2 Background

In our project we are going to use thermoelectric refrigeration as a technique for

refrigeration. It uses the Peltier effect in order to produce refrigeration. The Peltier effect is

named after a French scientist who discovered it in 1834. In 1834 Jean Peltier noted that

when an electrical current is applied across the junction of two dissimilar metals, heat is

removed from one junction and transferred to the other. Thermoelectric modules are

constructed from a series of tiny metal cubes of dissimilar exotic metals which are physically

bonded together and connected electrically. When electrical current passes through the cube

junctions, heat is transferred from one metal to the other. Solid-state thermoelectric modules

are capable of transferring large quantities of heat when connected to a heat absorbing device

on one side and a heat dissipating device on the other.

The Peltier effect: The Peltier effect is a temperature difference created by applying a

voltage between two electrodes connected to a sample of semiconductor material. A Peltier

cooler, heater, or thermoelectric heat pump is a solid-state active heat pump which transfers

heat from one side of the device to the other, with consumption of electrical energy,

depending on the direction of the current. Such an instrument is also called a Peltier device,

Peltier heat pump, solid state refrigerator, or thermoelectric cooler (TEC). It can be used

either for heating or for cooling, although in practice the main application is cooling. It can

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

The primary advantages of a Peltier cooler compared to a vapor-compression refrigerator are

its lack of moving parts or circulating liquid, very long life and invulnerability to potential

leaks, and its small size and flexible shape.

1.3 Different components

1.3.1 Major components

(i) Peltier unit

(ii) Fan

(iii) Heat radiator

(iv) Solar cell panel

(v) Ice box (12 Lt)

(vi) 12V battery

1.3.2 Minor components

(i) Wires

(ii) Two way switch

(iii) DC Adaptor

(iv) Aluminium sheet

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

The world is facing a critical problem of energy deficit which underlines the very existence

of survival. Global warming on the other hand is proving a major crisis to be dealt with. As

the world strives to solve the energy problem, there has been a growing interest in

strengthening education in renewable energy technologies and related fields which puts

importance on the study of interdisciplinary subjects.

An American society of refrigeration engineer has defined refrigeration as “the science of

providing and maintaining temperature below that surrounding atmosphere” [1].

Refrigeration is considered as the major contributor of technology for the humanity in many

ways. In this literature review, the focus is on designing such a system that has the

fundamentals to accomplish a given cooling task while minimizing electrical power input,

without the need of a compressor, which is completely based on thermoelectric cooling

technology with the use of solar energy. The research data available for this technology has

been reviewed here.

Xi Hongxia et al.[2007][2] studied that thermoelectric refrigeration emerges as the new green

technology due to their distinct advantages as noiseless and wearless due to no moving parts,

reliable, portable and compatible with solar PV cell generated DC power, making them

complete environment friendly.

Bansal et al.[2000][3] did a detailed comparative study on thermoelectric, vapor compression

and absorption refrigeration system to compare the development cost, energy consumption,

noise intensity production and COP for these three systems.

2.2 Thermoelectric modules

Thermoelectric semiconductor materials were first developed in the 1950’s. Since 1960’s

improvement in the quality control was made.

2.3 Developments in thermoelectric refrigeration systems

Dai et al. [2003][4] devised a thermoelectric refrigeration system powered by solar cells and

analyzed the process. They developed a prototype which maintained a temperature at 5-10 C,

and COP about 0.3 under suitable conditions.

Min et al.[2006][5] devised various prototypes of thermoelectric domestic refrigerator with

the combination of heat exchangers and evaluated the cooling performance with respect to

COP, heat pumping capacity, cooling down rate and temperature stability. They concluded

that liquid operated thermoelectric refrigerators possess a lower COP than a forced air

convection system.

Wahab et al.[2009][6] developed a thermoelectric refrigerator using a combination of

modules to reduce the temperature of the refrigerated space from 27 C to 5 C in about 44

minutes. The COP was calculated and found to be about 0.16.

CHAPTER 3

PROBLEM FORMULATION

3.1 Scope

To reduce the electricity consumption of refrigeration system by employing

thermoelectric technology (Peltier Effect).

To use solar energy as the alternative power source of the refrigerator.

3.2 Objective

The main objective of the project is to make an economical and portable refrigerating

system which will not use a compressor or any other moving devices. In addition to the main

objective, the power source used to drive the refrigerator is also taken into consideration.

Here the power source is based on a renewable source, solar energy.

CHAPTER 4

DESCRIPTION OF THE COMPONENTS

4.1 Peltier Module

Peltier Module is most essential part in our project. Peltier module consists of an array of

semiconductor pellets that have been doped so that one type charge carrier either positive or

negative carries the majority of current. Two semiconductors, one p-type & another n-type

having different electron densities are used (1). N-type material is doped so that it will have

an excess of electrons (more electrons than needed to complete a perfect molecular lattice

structure) & P-type material is doped so that it will have a deficiency of electrons (fewer

electrons than are necessary to complete a perfect lattice structure). The extra electrons in the

N material and the holes resulting from the deficiency of electrons in the P material are the

carriers which move the heat energy through the thermoelectric material. Most thermoelectric

cooling modules are fabricated with an equal number of N-type and P-type elements where

one N and P element pair form a thermoelectric couple. Semiconductors placed thermally in

parallel to each other & electrically in series to each other metalized ceramic sheets are used

as a cover. Semiconductors are connected by side by side & are sandwiched between two

ceramic plates (2).There are also two free ends exists which are connected to applied voltage.

This unit works on Peltier theory which is already described earlier. When DC voltage is

applied to the module, semiconductors absorb heat energy from one ceramic sheet surface &

release it to another surface where the heat sink is. The surface where the heat energy is

absorbed becomes cold & the opposite surface where heat energy is released becomes hot.

This phenomenon can be reversed by a change in the polarity of applied DC voltage causing

the heat to be moved in opposite direction .Thus temperature difference occurs. Most

thermoelectric modules range in size from approximately 2.5-50 mm (0.1 to 2.0 inches)

square and 2.5-5mm (0.1 to 0.2 inches) in height (2).It is generally suitable for precise

temperature control applications. It is generally used as a cooing unit for portable coolers,

cooling electronic components & small equipments. Its heat emission side can be used for

keeping the food warm & other heating purposes. They are used for cooling the computer

components & also in satellites. It also can be used for power generation. Cooling capacity is

proportional to the magnitude of applied DC voltage & the thermal conditions on each side of

the module.

Fig 1: Peltier Circuit

Benefits of using peltier module as a cooler units are given below:

No moving parts & easy maintenance

No refrigerants/chlorofluorocarbons

Flexible shape

Heating & cooling with same module

Wide operating temperature range

Environmentally friendly

Acoustically silent

Can be used in environments which are severe for conventional refrigeration

Long life

Although it has several advantages, some disadvantages of using module also exist.

Dissipation of limited amount of heat flux

Low coefficient of performance

Low Efficiency compared to conventional refrigerators(1)

Fig 2: Peltier Module Structure

4.2 Cooling Fan

Fan is a machine used to create flow with in a fluid, typically gas such as air. Fan consists of

a rotating arrangement of vanes or blades which act on the fluid. Blades are attached on the

periphery of a hub called as impeller & the rotating assembly is known as runner or rotor. All

the moving parts are enclosed in a case. This directs the air flow as well as act as a safeguard

for the other components from the moving blades. Most fans are powered by electric motors,

but other sources of power may be used (such as hydraulic power).Fan is generally used for

cooling purposes besides it has also other application. Cooling fans become essential

component in nearly all electronic equipments (3).Fan’s purpose to ensure cool operating

temperature. It draws the cooler air from outside atmosphere & expels warm air from inside

to maintain suitable operating temperature. It applies right amount of cool air to the

components, protecting against heat that can harm electronics & effects the performance. Its

angled blades guide air outside of the device into the device where the heat emission occurs,

in a single direction. It also dejects the warm air from the inside of the device (4).

Today fans having various sizes, shapes, colors etc are installed in the electronic devices. The

size & shape of the apparatus decides the size of the cooling fan. The cooling capability of

fan depends upon its size, speed & power consumed. A fan that can spin at higher rotation

per minute will funnel more air into the device than a slower fan.

In this device a fan is incorporated under the lower side of the heat radiator. When heat

generates at the hot junction of peltier module, it extracts heat from the source & provide cool

air to maintain operating temperature.12V DC-0.18A fan is used in this device. It is sleeve

bearing type made by Chiefly Choice Company Ltd.Dimensions of this fan are

200mm*200mm*60mm (W*L*H).

Fig 3: Cooling Fan

4.3 Heat Sink

Radiators are heat exchangers used to transfer heat from one medium to another medium for

the purpose of cooling & heating. Radiator is a source of heat to its environment, although

this may be for either heating purposes, or cooling the components. The heating radiator was

invented by Franz San Galli, Russian businessman in 1855.In electronic devices we generally

use heat sink as a radiator. A heat sink is a passive heat exchanger that cools a device by

dissipating heat into surrounding medium. Heat is transferred to the air by conduction and

convection; a relatively small proportion of heat is transferred by radiation owing to the low

temperature of semiconductor devices compared to their surroundings (5).

A heat sink transfers thermal energy from a higher temperature device to a lower

temperature fluid medium. The fluid medium is frequently air, but can also be water,

refrigerants or oil. If the fluid medium is water, the heat sink is frequently called a cold plate.

In thermodynamics a heat sink is a heat reservoir that can absorb an arbitrary amount of heat

without significantly changing temperature. Practical heat sinks for electronic devices must

have a temperature higher than the surroundings to transfer heat by convection, radiation, and

conduction. The power supplies of electronics are not 100% efficient, so extra heat is

produced that may be detrimental to the function of the device. As such, a heat sink is

included in the design to disperse heat to improve efficient energy use.

From the Fourier’s Law of Heat Conduction & Newton’s Law of Cooling we can determine

how much heat transfer happens by conduction theoretically.

To design a heat sink there are some factors must be followed which are given below:

Thermal resistance

Material

Fin efficiency

Spreading resistance

Shape of the fins

Location of the fins

Fin arrangements

Conductivity of the material

Surface color

The popular heat sink materials are aluminium alloys. Aluminium alloys 6061 & 6063 are

commonly used. Copper also has excellent heat sink properties. Diamonds, composite such as

copper-tungsten alloy, AlSiC & Dymalloy etc are also used for heat sink materials. There are

also various types of fin arrangements in heat sinks such as pin fin, straight fin, flared fin etc.

In general, the more surface area a heat sink has, the better it works. However, this is not

always true. The concept of a pin fin heat sink is to try to pack as much surface area into a

given volume as possible. We used straight fin heat sink as a heat dissipator.

As power dissipation of components increases and component package size decreases,

thermal engineers must innovate to ensure components won't overheat. Devices that run

cooler last longer. A heat sink design must fulfill both its thermal as well as its mechanical

requirements. Concerning the latter, the component must remain in thermal contact with its

heat sink with reasonable shock and vibration. The heat sink could be the copper foil of a

circuit board, or else a separate heat sink mounted onto the component or circuit board.

Attachment methods include thermally conductive tape or epoxy, wire-form z clips, flat

spring clips, standoff spacers, and push pins with ends that expand after installing. They are

used in microprocessor cooling, cooling of other heat emission components such as light

emitting diode lamps & for soldering purposes.

In our device heat sink is placed between peltier module & 12V DC fan. It is straight fin type,

portable & it is adhered by ceramic paste adhesive.

Fig 4: Heat Sink

4.4 Solar Cell Panel

Solar panels are devices that convert light into electricity. They are called solar panels

because most of the time, the most powerful source of light available is the Sun, called Sol by

astronomers. Some scientists call them photovoltaic which means, basically, "light-

electricity”. A solar panel is a collection of solar cells. Lots of small solar cells spread over a

large area can work together to provide enough power to be useful. The more light that hits a

cell, the more electricity it produces. Solar panel refers either to a photovoltaic module,

a solar hot water panel, or to a set of solar photovoltaic modules electrically connected and

mounted on a supporting structure. A PV module is a packaged, connected assembly of solar

cells. Solar panels can be used as a component of a larger photovoltaic system to generate

and supply electricity in commercial and residential applications. Each module is rated by

its DC output power under standard test conditions, and typically ranges from 100 to 320

watts. The efficiency of a module determines the area of a module given the same rated

output. A single solar module can produce only a limited amount of power; most installations

contain multiple modules. A photovoltaic system typically includes a panel or an array of

solar modules, an inverter, and sometimes a battery and/or solar tracker and interconnection

wiring. If we can harness the solar power efficiently, then we may not need to rely on burning

fossil fuels for energy.

Solar modules use light energy (photons) from the sun to generate electricity through

the photovoltaic effect. The majority of modules use wafer-based crystalline silicon cells

or thin-film cells based on cadmium telluride or silicon. The structural (load carrying)

member of a module can either be the top layer or the back layer. Cells must also be

protected from mechanical damage and moisture. Most solar modules are rigid, but semi-

flexible ones are available, based on thin-film cells. These early solar modules were first used

in space in 1958.

Electrical connections are made in series to achieve a desired output voltage and/or in

parallel to provide a desired current capability. The conducting wires that take the current off

the modules may contain silver, copper or other non-magnetic conductive metals. The cells

must be connected electrically to one another and to the rest of the system. Externally,

popular terrestrial usage photovoltaic modules use MC3 or MC4 connectors to facilitate easy

weatherproof connections to the rest of the system. Bypass diodes may be incorporated or

used externally, in case of partial module shading, to maximize the output of module sections

still illuminated. Some recent solar module designs include concentrators in which light is

focused by lenses or mirrors onto an array of smaller cells. This enables the use of cells with

a high cost per unit area (such as gallium arsenide) in a cost-effective way.

Most modules are currently produced from solar cells made of

polycrystalline and monocrystalline silicon. In 2013, crystalline silicon accounted for more

than 90 percent of worldwide PV production. Most parts of a solar module can be recycled

including up to 97% of certain semiconductor materials or the glass as well as large amounts

of ferrous and non-ferrous metals. Some private companies and non-profit organizations are

currently engaged in take-back and recycling operations for end-of-life modules. Panels can

be mounted in a various way such as ground mounting, roof mounting, pole mounting,

ballasted footing mountings etc (6).

In this device 36 cell solar photovoltaic module is used which has maximum50.00 watt power

& 2.85A current at maximum power. Its dimensions are 576*666*34mm (L*W*H) &

tolerances will be 1.5 mm (7).

Fig 5: Solar Cell Panel

4.5 Ice Box

An icebox or cold closet is a compact non-mechanical refrigerator which was

common kitchen appliance before the development of safe powered refrigeration devices (8).

The Ice Box is a Food Tab structure used to store and preserve Food, reducing spoilage rate

by 50% (so edible items stored in an Ice Box will last twice as long before spoiling).

Commonly iceboxes were made of wood, most probably for ease of construction, insulation,

and aesthetics: Many were handsome pieces of furniture. But this ice box is made of thermo

setting plastic & thermocol. Its wall is insulating. The following items can be placed in the

ice box: many food items, petals & ice (9). As food spoils faster in summer, it is

recommended players put their food in the Ice Box to slow down the spoiling rate of food and

help preserve food for Winter. It is portable & in the lower part the cold junction of the

peltier module is exposed. Inner surface of box is covered by aluminium sheets because it

helps in uniform transfer of heat. It is easy to carry, easy to dispatch & easy to assemble.

Fig 6: Ice Box

4.6 Battery

An electric battery is a device consisting of one or more electrochemical cells that convert

stored chemical energy into electrical energy. Each cell contains a positive terminal or

cathode and a negative terminal, or anode. Electrolytes allow ions to move between the

electrodes and terminals, which allows current to flow out of the battery to perform work.

Primary (single-use or disposable) batteries are used once and discarded; the electrode

materials are irreversibly changed during discharge. Common examples are the alkaline

battery used for flashlights and a multitude of portable devices. Secondary (rechargeable

batteries) can be discharged and recharged multiple times; the original composition of the

electrodes can be restored by reverse current. Examples include the batteries used in vehicles

and lithium ion batteries used for portable electronics.

Batteries come in many shapes and sizes, from miniature cells used to power aids and

wristwatches to battery banks the size of rooms that provide standby power for telephone and

computer data centers.

According to a 2005 estimate, the worldwide battery industry generates US$48 billion in

sales each year, with 6% annual growth.

Batteries have much lower specific energy (energy per unit mass) than common fuels such as

gasoline. This is somewhat mitigated by the fact that batteries deliver their energy as

electricity which can be converted efficiently to mechanical work, whereas using fuels in

engines entails a low efficiency of conversion to work(10).

In this device two 6V rechargeable batteries are used. This Battery is charged by solar cell

panel.

Fig 7: Battery

4.7 Wires

A wire is a single, usually cylindrical, flexible strand or rod of metal. Wires are used to bear

mechanical loads or electricity and telecommunications signals. Wire is commonly formed by

drawing the metal through a hole in a die or draw plate. Wire gauges come in various

standard sizes, as expressed in terms of a gauge number. The term wire is also used more

loosely to refer to a bundle of such strands, as in multi-stranded wire, which is more correctly

termed a wire rope in mechanics, or a cable in electricity. Wire comes in solid core, stranded,

or braided forms. Although usually circular in cross-section, wire can be made in square,

hexagonal, flattened rectangular or other cross-sections, either for decorative purposes, or for

technical purposes such as high-efficiency voice coils in loudspeakers. Edge-wound coil

springs, such as the Slinky toy, are made of special flattened wire. Wire is often reduced to

the desired diameter and properties by repeated drawing through progressively smaller dies,

or traditionally holes in draw plates. After a number of passes the wire may be annealed to

facilitate more drawing or, if it is a finished product, to maximize ductility and conductivity

(11).

Fig 8: Wires

4.8 Two Way Switch

In electrical engineering, a switch is an electrical component that can break an electrical

circuit, interrupting the current or diverting it from one conductor to another. The mechanism

of a switch may be operated directly by a human operator to control a circuit (for example, a

light switch or a keyboard button), may be operated by a moving object such as a door-

operated switch, or may be operated by some sensing element for pressure, temperature or

flow(12).

Two way switch is used in multi-way switching having interconnection of two or

more electrical switches to control an electrical load (often, but not always, lighting) from

more than one location. 2 way switching means having two or more switches in different

locations to control one electrical operation. They are wired so that operation of either switch

will control a light. This arrangement is often found in stairways, with one switch upstairs

and one switch downstairs or in long hallways with a switch at either end (13).

Fig 9: Two Way Switch Circuit

4.9 AC/DC Adapter

AC/DC adapter or AC/DC converter is a type of external power supply, often enclosed in a

case similar to an plug. It has Other names include plug-in adapter, adapter block, line power

adapter, power brick and power adapter. Adapters for battery-powered equipment may be

described as chargers or rechargers (see also battery charger).AC/DC adapters are used with

electrical devices that require power but do not contain internal components to derive the

required voltage and power from mains power. The internal circuitry of an external power

supply is very similar to the design that would be used for a built-in or internal supply.

Originally, most AC/DC adapters were linear power supplies, containing a transformer to

convert the mains electricity voltage to a lower voltage, a rectifier to convert it to pulsating

DC and a filter to smooth the pulsating waveform to DC. Size and weight of the device was

largely determined by the transformer, which in turn was determined by the power output

and mains frequency (14).

We use 12V AC/DC Adapter in this system.

Fig 10: AC/DC Adapter

4.10 Aluminium Sheet

A sheet made of aluminium is used for heat conduction purposes. Aluminum is also a popular

metal used in sheet metal due to its flexibility, wide range of options, cost effectiveness, and

other properties. Aluminium’s thermal conductivity is 237 W/mK. Box is made of insulating

materials (15).So thermal conduction is not occurred that much if no thermal conductive

material is introduced inside. Aluminium has good thermal properties & its sheet provides

uniform heat conduction throughout its surfaces. So sheet is attached at inner surface by

screws.

Apart from this four clamps are incorporated beneath the ice box to hold device position &

balance its mass.

CHAPTER 5

DEVELOPMENT AND CONSTRUCTION

(i) Step 1: First of all we have cut the icebox in one end so that it fits the heat sink.

Fig 11: Cut Icebox (14Lts)

(ii) Step 2: Than we have taken the Peltier module and pasted the heat sink on it using

ceramic paste.

Fig 12: Peltier module and heat sink

(iii) Step 3: Then we have inserted this combination (peltier module and heat radiator) to

the icebox. The wire terminals of the peltier module are kept outside the box.

Fig 13: Heat sink

(iv) Step 4: The wire terminals of the peltier module are then connected to the wires of the

fan and the fan is kept outside the icebox.

Fig 14: Connection between peltier module and fan

(v) Step 5: then this whole thing is connected to the two-way switch.

Fig 15: Connection of Two-way switch

(vi) Step 6: The two-way switch is further connected to the battery (12V) which is

charged using the solar cell panel.

Fig 16: Battery connected to Solar cell panel

(vii) Step 7: The aluminium sheet is fitted inside the icebox covering the peltier module.

Fig 17: Aluminium sheet

(viii) Step 8: The total assembly is shown below.

Fig 18: Complete Setup

5.1 DESIGN AND ANALYSIS

5.1.1 DESIGN

Firstly the part-modeling of different components of this project has been done in Pro-E and

3-D rendering done in Autodesk 3DS. Following are the simulated models of the respective

components:

Fig: Model of individual components

Fig19: Complete refrigerator model

5.1.2 CALCULATIONS/ANALYSIS

The calculations have been carried out using the necessary formula and putting the values of

temperature as recorded by a thermocouple temperature sensor.

COOLING CAPACITY

Volume of water to be cooled = 0.35 liters = 0.35 Kg

Ambient temperature (Th) = 27 ºC

Cooled temperature (Tc) = 5 ºC

Time required for the refrigerator to cool 0.35 liters of water = 40 minutes

Now, the cooling capacity required by the refrigerator to cool 0.35 liters of water in 40

minutes from 27 ºC to 5 ºC is equal to the amount of heat rejected by the refrigerator.

If ‘Q’ is the amount of heat rejected then,

Q = (m*c*dT)

Q = m*c*(Th-Tc)

m = mass of water to be refrigerated (Kg)

c = specific heat of water (J/Kg/ºC)

dT = temperature difference (ºC)

Q = 0.35*4180*(27-5) Joules

Q = 32186 Joules

So the heat rejected per second = (32186/3600) J/s

= 8.940 J/s

= 8.940 W

TOTAL POWER REQUIREMENT

The total power required by the refrigerator is equal to the sum of power required by the fan

and the power required by the peltier module.

Power used by the fan = 0.48 W

Power required for the peltier module = 60.8 W

So total power required = (60.8+0.48) W

= 61.28 W

CALCULATION OF Coefficient of Performance (COP)

The COP of the refrigerator is calculated as the ratio of heat removed to the power input or

the ratio of refrigerating effect to the work done.

So, COP = (Heat Removed/ Power Input) = (Refrigerating Effect/ Work done)

= (8.940/61.28) = 0.145

COP = 0.145 or 14.5%

Thus, the COP of this refrigerator is 14.5%.

SOLAR CELL PANEL CONFIGURATION

Each solar cell generates 1.8 Watts (0.5 V* 1.8 A) of electricity.

Here, the calculation is for the minimum number of solar cells required to drive the

refrigerator.

So, number of solar cells needed = (61.28/1.8)

= 34.04

= 35 (approx) units

Thus, the minimum number of solar cells required as according to the power input is

approximately equal to 35 units.

CHAPTER 6:

RESULT AND DISCUSSIONS

The Coefficient of Performance of the refrigerator is found to be 0.145 or 14.5% by

consuming only 61.28 watts of electricity while changing the cabinet temperature from 27 ºC

to 5 ºC. This shows that the refrigerator consumes less energy to give a considerable cooling

effect.

Here, the discussion is solely concentrated on the advantages of thermoelectric refrigeration

system and comparison of thermoelectric refrigeration system with other methods of

refrigeration.

6.1 ADVANTAGES OF THERMOELECTRIC REFRIGERATION SYSTEM

COMPACT SIZE: The space required by the cooling system is very little.

LIGHTWEIGHT: The unit is very portable which can be carried with one hand and

is unaffected by motion or tilting.

LOW PRICE: 20% - 40% less expensive than compressor or absorption units.

LOW BATTERY: The battery used is of low voltage, 12V.

HEATING OPTION: This unit can also be used for heating operations.

SAFETY: No toxic refrigerant or open flames, propane.

RELIABILITY: Thermo-electrics provide a substantial degree of reliability of long

period.

EASY SERVICE: The parts can be easily replaced by a screwdriver.

LOW MAINTENANCE: This unit requires no maintenance at all due to absence of

moving parts.

6.2 COMPARISON OF THERMOELECTRIC REFRIGERATION WITH OTHER

METHODS OF REFRIGERATION

THERMOELECTRIC: The process of cooling is obtained by the use of Peltier

modules which uses the Peltier effect.

COMPRESSOR: Unlike closed cycles such as Vapor Compression Refrigeration

system, it does not need a compressor in order to produce cooling effect. It uses a

Peltier module attached with a heat sink.

ABSORPTION: Unlike Vapor Absorption Refrigeration system, it does not need to

vaporize a refrigerant to produce cooling effect as it uses no refrigerant.

COMPACTNESS: The thermoelectric modules the very compact because of the

small size of the cooling component.

WEIGHT: The unit weighs 1/3rd

to ½ of the weight of other refrigerating system.

PORTABILITY: These units are light enough to carry with one hand and are not

affected by tilting or motion whereas compressor models are quite heavy.

COST: It costs 20%-40% less than other equivalent compressing or absorption units.

INSTANT COOLING: The refrigerator achieves maximum cooling temperature in

about 30 seconds.

RELIABILITY: Thermoelectric units do not wear out due to prolonged use as there

are no refrigerant or moving devices as compared to Vapor Compression or

Absorption units because of a tendency of leakage.

MAINTENANCE: These units require low maintenance due to one moving part, fan,

and can be replaced with a screwdriver only whereas in both compressor and

absorption units, they require trained mechanics and special service equipments

needed for service.

CHAPTER 7

CONCLUSION AND FUTURE SCOPE

7.1 Conclusion

After the completion of the project it can be concluded that compressor less refrigeration is

possible and can be done using thermoelectric effect (Peltier effect). Using the peltier effect

not only refrigerators but heat pumps also can be made which will simultaneously heat and

cool substances. These compressor-less refrigerators are very cheap to manufacture, have less

number of moving parts, portable and can be used efficiently in hot weather.

7.2 Future scope

This project can be easily upgraded using more number of peltier unit, fan and by building its

body using terracotta clay or any other suitable substance which will further increase the

cooling inside the refrigerator. This will make the refrigeration effective and also increase its

COP. Since it is portable, lower priced, require low maintenance and the power source used

in this project is solar power, which is a renewable energy source we believe that its demand

is going to increase in future.

REFERENCES

Web References

1. http://en.wikipedia.org/wiki/Thermoelectric_cooling

2. https://www.ferrotec.com/technology/thermoelectric/

3. http://en.wikipedia.org/wiki/Mechanical_fan

4. http://www.nmbtc.com/ac-fans/accooling/

5. http://en.wikipedia.org/wiki/Heat_sink

6. http://en.wikipedia.org/wiki/Solar_panel

7. http://www.elecssol.com/solar-photovoltaic-36.html

8. http://en.wikipedia.org/wiki/Ice_box

9. http://dont-starve-game.wikia.com/wiki/Ice_Box

10. http://en.wikipedia.org/wiki/Battery_(electricity)

11. http://en.wikipedia.org/wiki/Wire

12. http://en.wikipedia.org/wiki/Switch

13. http://www.lightwiring.co.uk/two-way-switching-3-wire-system-new-harmonised-

cable-colours/

14. http://en.wikipedia.org/wiki/AC_adapter

15. http://en.wikipedia.org/wiki/Aluminium

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