DEVELOPMENT OF FORM STABLE PHASE

CHANGE MATERIAL FOR SOLAR WATER

HEATER

YU GEN QIAN

UNIVERSITI TUNKU ABDUL RAHMAN

DEVELOPMENT OF FORM STABLE PHASE CHANGE MATERIAL FOR

SOLAR WATER HEATER

YU GEN QIAN

A project report submitted in partial fulfillment of the

requirements for the award of the degree of

Bachelor of Engineering (Hons) Petrochemical Engineering

Faculty of Engineering and Green Technology

Universiti Tunku Abdul Rahman

May 2018

ii

DECLARATION

I hereby declare that this project report is based on my original work except for

citations and quotations which have been duly acknowledged. I also declare that it

has not been previously and concurrently submitted for any other degree or award at

UTAR or other institutions.

Signature : ___________________________

Name : Yu Gen Qian

ID No. : 13AGB05459

Date : 2 May 2018

iii

APPROVAL FOR SUBMISSION

I certify that this project report entitled “DEVELOPMENT OF FORM STABLE

PHASE CHANGE MATERIAL FOR SOLAR WATER HEATER” was

prepared by YU GEN QIAN has met the required standard for submission in partial

fulfilment of the requirements for the award of Bachelor of Engineering (Hons)

Petrochemical Engineering at Universiti Tunku Abdul Rahman.

Approved by,

Signature : _________________________

Supervisor : Associate Professor Dr. Yamuna a/p Munusamy

Date : _________________________

Signature : _________________________

Co-Supervisor : Dr. Lai Koon Chun

Date : _________________________

iv

The copyright of this report belongs to the author under the terms of the

copyright Act 1987 as qualified by Intellectual Property Policy of Universiti Tunku

Abdul Rahman. Due acknowledgement shall always be made of the use of any

material contained in, or derived from, this report.

© 2018, Yu Gen Qian. All right reserved.

v

Specially dedicated this thesis to my parents, David Yu Sing Ong and Teong Chooi

Hua who have always loved me unconditionally and whose good examples have

taught me to work hard for the things that I aspire to achieve. This work is also

dedicated to my brothers: Gen Cheng, Gen Jin, Gen Xin, my girlfriend Sharon Teh

and best friends who have always been a constant source of support and

encouragement during the challenges of my whole university life.

vi

ACKNOWLEDGEMENTS

Jesus said to him, "I am the way, the truth, and the life. No one comes to the

Father except through me”. John 14:6

For God so loved the world that he gave his one and only Son, that whoever

believes in him shall not perish but have eternal life. John 3:16

Thank you Almighty God for the blessings and graciously allowing me to complete

this research paper. I would like to express my outmost gratitude to my research

supervisor, Associate Professor Dr. Yamuna Munusamy for her guidance throughout

the development of the research. I would also like to thank the lecturers, staffs of

UTAR and postgraduate especially Ms. Kee Shin Yiing who had given me a lot of

assistance and advices during the course of the project. Nonetheless, I would like to

thank my parents for supporting me spiritually throughout writing this thesis and my

life in general.

Last but not least, I would also like to express my gratitude to my friends for

their support.

vii

DEVELOPMENT OF FORM STABLE PHASE CHANGE MATERIAL FOR

SOLAR WATER HEATER

ABSTRACT

Demand for solar water heater is increasing due to their low cost, easy fabrication

and maintenance. It can also reduce the emission of carbon dioxide in the atmosphere.

Phase change material (PCM) is the most popular and widely used thermal energy

storage material in solar water heater. PCM is able to absorb and release large

amount of latent heat energy during the phase transition process over a narrow

temperature range. In this work, form stable PCM was prepared by blending the

myristic acid with PMMA and then coating with nitrile butadiene rubber (NBR) and

polyarylic (PA). The purpose of adding PMMA into the myristic acid is to increase

the thermal stability of the PCM during phase change process. Leakage test results

showed that addition of 20 wt% PMMA to the myristic acid while reduce the weight

percentage of myristic acid together with coating layers could eliminate leakage.

Tensile test results showed that combination of PA and NBR coating material

provide sufficient strength and elasticity to contain the PCM during the phase change

process, while Fourier transform infrared spectroscopy (FTIR) analysis results

proves that a compact and uniform coating without cracks were formed on the

surface of PCM. Differential scanning calorimetry (DSC) results show that the latent

heat of melting and freezing of the form stable PCM80 is 107.56 J/g and 102.26 J/g

which is comparable with others results in literature.

Keywords: Phase change material; PMMA; myristic acid; coating

viii

TABLE OF CONTENTS

DECLARATION ii

APPROVAL FOR SUBMISSION iii

ACKNOWLEDGEMENTS vi

ABSTRACT vii

TABLE OF CONTENTS viii

LIST OF TABLES x

LIST OF FIGURES xi

LIST OF SYMBOLS / ABBREVIATIONS xiii

LIST OF APPENDICES xv

CHAPTER

1 INTRODUCTION 1

1.1 Background of Study 1

1.2 Problem Statement 5

1.3 Research Objectives 6

2 LITERATURE REVIEW 7

2.1 Classification of Phase Change Material (PCM) 7

2.1.1 Inorganic materials 8

2.1.2 Organic materials 9

2.1.3 Polymeric PCM 10

2.2 Differentiation of Various Types of PCMs 12

2.3 Criteria of Selecting PCMs 12

2.4 Solar Renewable Energy 15

2.5 Thermal Energy Storage 16

2.6 Form stable PCM 18

2.6.1 Encapsulation Method 19

2.6.2 Shape-stabilized Encapsulation Method 20

2.6.3 Microencapsulation Method 23

2.6.4 Crosslinked Polymer Coating Method 24

2.7 Coating 25

ix

2.7.1 Coating Application Methods 25

2.7.2 Coating of Phase Change Material 26

2.8 Stability of Non-paraffin Organic PCMs 28

2.9 Challenges to Produce Good Coating 29

2.10 Applications of PCMs 30

3 METHODOLOGY 33

3.1 Materials 33

3.1.1 Experiment Flow Chart 33

3.2 Preparation of PCM 34

3.2.1 Preparation of PCM Blending 34

3.2.2 Pelletizing of PCM 37

3.3 Coating of Polyacrylic and Nitrile Butadiene Rubber on PCM

through Dip Coating Method 38

3.4 Characterization 40

3.4.1 Fourier Transform Infrared Spectroscopy (FTIR-ATR) 40

3.4.2 Differential Scanning Calorimetry (DSC) 40

3.4.3 Leakage test 41

3.4.4 Tensile Test 42

4 RESULTS AND DISCUSSIONS 44

4.1 Characterization of Form Stable PCM 44

4.1.1 Tensile Test 44

4.1.2 Leakage Test 45

4.1.3 Differential Scanning Calorimetry (DSC) 48

4.1.4 Fourier Transform Infrared Spectroscopy (FTIR-ATR) 54

5 CONCLUSION AND RECOMMENDATIONS 60

5.1 Conclusion 60

5.2 Recommendation 61

REFERENCES 62

APPENDICES 78

x

LIST OF TABLES

TABLE TITLE PAGE

2.1 Comparison of Different Types of PCMs 12

2.2 PCM Selection Criteria 13

2.3 Thermal Properties of Fatty Acids, Eudragit

S/Fatty Acid Blends (30/70 wt%) as Form-stable

PCMs 20

2.4 Thermal Properties of Some Fatty Acids and

Form-stable Compositions 21

2.5 Thermal Properties of Fatty Acids and 30%

Eudragit E/70% Fatty Acid (w/w) Blends as Form-

stable PCM 22

3.1 Formulation of PCM samples 35

4.1 Tensile properties of polymer coating film 45

4.2 Leakage area of non-coated PCMs 47

4.3 Leakage area of coated PCMs 47

4.4 Latent Heat Absorbed and Released by PCM 48

4.5 Examples of Form Stable Solid-Liquid Organic

PCMs and Some of Their Thermal Properties 51

4.6 Absorption Frequency Obtained for PA 55

4.7 Absorption Frequency Obtained for Myristic Acid 56

4.8 Absorption Frequency Regions and Functional

Groups for coated PCMs. 59

xi

LIST OF FIGURES

FIGURE TITLE PAGE

1.1 Features of a Latent Heat Storage Material 2

1.2 Schematic Experimental Setup of Solar Water

Heater Integrated with PCMs 4

2.1 Classification of PCM 8

2.2 Melting Temperature and Phase Change Enthalpy

of Currently Applicable PCMs 13

2.3 Schematic Representation of a Phase Change

Process 14

2.4 The storage capacity of various composites 18

3.1 Overall Flow of Methodology 34

3.2 The process of stirring the PMMA and MA in

chloroform 35

3.3 Setup of the mixing process 36

3.4 The drying process of the mixture solution 36

3.5 The formation of phase change material blending

composition 36

3.6 FTIR presser 38

3.7 The die 38

3.8 The NBR coating solution (left) and PA coating

solution (right) 39

3.9 The PCM sample preparation on a Teflon sheet. 39

3.10 The set up for leakage test 41

xii

3.11 Specimen for Tensile Test 42

3.12 Teflon mold 42

4.1 Leakage of coated PCM after 30 thermal cyclic

process 46

4.2 Leakage of PCM without coating after 30 thermal

cyclic process 46

4.3 DSC graph combination for different weight

percentage of PMMA in PCM of heat absorption

peaks 49

4.4 DSC graph combination for different weight

percentage of PMMA in PCM of heat release

peaks 49

4.5 FTIR spectrum of pure myristic acid 54

4.6 Combination of FTIR spectrum of PCMs without

coating 57

4.7 Combination of FTIR spectrum of PCMs with

coating 58

xiii

LIST OF SYMBOLS / ABBREVIATIONS

∆H enthalpy

Al aluminium

Al2O3 aluminium oxide

CA capric acid

Cr chromium

Cr2O chromium oxide

Cu copper

DSC Differential Scanning Calorimetry

EG expanded graphite

EP expanded perlite

EVA ethylene-vinyl acetate

FTIR Fourier Transform Infrared Spectroscopy

HDPE high density poly(ethylene)

LDPE low density poly(ethylene)

IR infrared

LA lauric acid

LCOE levelized cost of electricity

LHTES latent heat thermal energy storage

MA myristic acid

MPCM microencapsulated PCMs

NaNO3 sodium nitrate

NBR nitrile butadiene rubber

Ni nickel

PA polyacrylic

PA palmitic acid

PAOs polyalphaolefins

PCM phase change material

xiv

PE poly (ethylene)

PEG polyethylene glycol

PEN poly (ethylene-2, 6-naphthalate)

PEX crosslinked high density polyethylene

PMMA polymethyl methacrylate

PP polypropylene

PS polystyrene

PVC polyvinyl chloride

RGO reduced graphene oxide

SA stearic acid

SBS styrene butadiene styrene copolymer

SS304L stainless steel

Steel C20 carbon steel

TCS thermo-chemical heat storage

TES thermal energy storage

Tom melting temperature

λ wavelength

xv

LIST OF APPENDICES

APPENDIX TITLE PAGE

A Fourier Transform Infrared Spectroscopy 78

B Differential Scanning Calorimetry 82

C Conference Proceeding 88

D Novel Research and Innovation Competition

2017 (NRIC) 90

1

CHAPTER 1

INTRODUCTION

1.1 Background of Study

Technology for storage of heat energy has emerged as a highly rated feature in rising

of global energy demand as well as energy saving circumstances. The shrinkage of

fossil fuel production and boost of renewable energy usage in recent years shift the

balance from conventional fossil fuels to environmental friendly renewable energy.

There are several methods to store heat energy, the most common methods are;

chemical energy, sensible heat energy and latent heat energy storage

(Extension.purdue.edu, 2017; Diaz, 2016). Among all these three ways of heat

storage alternatives, the most preferable method to store heat energy is latent heat

storage (Murali, Mayilsamy and Ali, 2015), because of their variety, capacity and

performance in thermal usages.

Phase change material (PCM) is a material that can store and release energy.

Application of PCM is the most general and prospective technique being used to

store latent heat energy. This is because of its storing and releasing capability of very

large amount of energy for each unit mass at nearly a constant temperature (Nayak et

al., 2011). Absorption of a huge amount of heat from the surroundings will melt the

PCM. Then, the freezing of PCM will discharges a great amount of energy, which is

latent heat at a rather constant temperature. The oscillation of temperature enables

PCM to recharge, showing that PCM is an ideal material for temperature monitoring

applications (Asyraf et al., 2016). PCMs have been developed for use across a broad

range of temperatures. They typically store 5 to 14 times more heat per unit volume

2

than materials such as water (Khan et al., 2017). Building applications integrated

with PCMs as a system to store latent heat energy are gaining much attention and

demand. The technological and market readiness of such systems are largely affected

by the heat transfer processes, and current cost of implementations of the system

(Kapsalis and Karamanis, 2016; Eames et al., 2014). Figure 1.1 shows the favourable

features of a latent heat storage material.

Figure 1.1: Features of a latent heat storage material (Khan et al., 2017).

Solar based water heaters are getting acknowledgment because of its sensible

value, ease of fabrication and maintenance. Application of sun based water radiator

reduces hazardous greenhouse emission associated with power generation (Energy

Saving Trust, 2015). Hot water is needed for showering, drinking, domestic and

business use (Marken, 2005). For the duration of 20 years of using only one sunlight

based water heater, 50 tons of carbon dioxide discharged can be eliminated (Shukla

et al., 2009). The hot water demand can be satisfied by taking into consideration the

temperature in the atmosphere and a rightfully designed sun oriented water heater.

Even though the system can operate at any weather, the performance of the system is

highly reliable on availability of solar energy at that respective place and the

temperature of water coming into the framework (Khan et al., 2015). The sunlight

based hot water frameworks in the year 2007 was around 154 GW. China is the

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world pioneer in their utilization with 70 GW introduced starting from 2006 and a

long haul objective of 210 GW by 2020 (Moore, 2015).

In order to fulfil the requirement of energy storage at night, significant

amount of solar energy should be stored during daytime. The reason is because solar

radiation supply is inconsistent in daytime and at night. Solar radiation integrated

energy storage system are in high demand, because it improves the system utility and

operability by adjusting temporal mismatches between the storage load and the

variation of solar energy intensity (Kumar, 2014). Sun based radiation cannot be

easily stored, so as a matter of first importance an energy transformation must be

achieved and, dependent upon this process, a storage device is required. For this

reason, heat storage using PCM is of huge significance due to its high storage density

and its isothermal nature of the storage (Sharma and Chen, 2009).

Storage and collector units are two main parts of functional solar energy

system. The collector’s function is to collect the radiation that hits on it and change a

fraction of it to other forms of energy. The solar energy that received by the collector

is not constant. Only an average of 250-300 W/m2 of solar energy is received by the

best locations on Earth, if averaged over the entire day-night cycles and over the

whole summer-winter a year (Alternative Energy Tutorials, 2014). In order to

increase the thermal storage efficiency, a storage unit is required to store the energy.

Storing thermal energy in the form of latent heat of fusion has more perks compared

to sensible heat. This is due to its isothermal nature of storage process at melting

temperature and high storage density (Shahare et al., 2017).

Energy collectors can be categorized into two types on operation mode and

condition basis which are active and passive system (Ogueke et al., 2009). A

significant difference between an active system and a passive system is that a passive

system has no pump while an active system has an electric pump. The function of

this pump is to regulate the heat transfer fluid. According to Sharma and Chen,

(2009), PCM can be efficiently used in a passive solar water heating system. This is

because PCM does not require any additional energy. Figure 1.2 shows the schematic

diagram for the setup of the solar water heater integrated with phase change material.

4

Figure 1.2: Schematic Experimental Setup of Solar Water Heater Integrated with

PCMs ((1) solar flat plate collector (varying heat source); (2) constant temperature

bath; (3) electric heater; (4) stirrer; (5) pump; (6 and 7) flow control valves; (8) flow

meter; (9) TES tank; (10) PCM capsules; (11) temperature indicator) (Zhou et al.,

2012).

An extensive range of inorganic, organic and mixtures of PCMs are available.

In this project, the main aim is to find out the best coating and blending composition

of myristic acid and PMMA to produce form stable PCM. Myristic acids have no

supercooling effects with reproducible freezing and melting behaviour, exhibit

suitable solid-liquid phase change temperature, good thermal properties, high latent

heat storage capacity and good thermal reliability (Sari and Kaygusuz, 2001; Fauzi et

al., 2014). However, throughout the phase change heat transfer process, the fatty acid

tends to melt and corrode the wall of the solar water heater heat storage tank (S.

Wahile et al., 2015; Sharma et al., 2004). Thus, myristic acid based PCMs must be

well confined to avoid them from leaking during the phase change process when

melting. This measure must be taken into deliberation in order to use them

practically.

5

1.2 Problem Statement

Application of PCMs in thermal energy storage improves thermal inertia, increases

thermal comfort, reduce internal temperature variations, and decreases heating and

cooling conditions (Pons et al., 2014). Nonetheless, they must be properly enclosed

to stop them from leaking in order to be usable in reality. In previous research, the

form-stable composite PCM was prepared by mixing PMMA and myristic acid in

different weight ratios. PMMA’s role was a supporting material while myristic acid

was used as PCM. Nevertheless, during the phase change process, volume change

induced leakage of a tiny amount of liquid PCMs from supporting material. Leakage

can be detected by measuring the weight of the PCM before and after the thermal

cyclic test or by using litmus paper. The acid that leaks out during the phase change

process is unwanted in PCM integrated thermal energy storage system because acid

has corrosive potential to corrode the internal area of the equipment (Whiffen and

Riffat, 2012; Cui and Riffat, 2011).

Encapsulation of PCM is a method to enhance the heat transfer surface area,

increase thermal conductivity, improve in operating temperature, diminish the risk of

phase segregation, and most importantly controls the PCM volume change to avoid

leakage during phase transition (Khan et al., 2017). According to several studies,

there are some common methods used to prevent leakage of PCM. Kumar et al.

(2015) stated that fusion of nanofillers with size less than 100 nm in PMMA will

enhance the mechanical, physical and thermal properties of the coating, but the short

coming of this method is the nanoscale dispersion of fillers and choice of

compatilizer to increase the interfacial adhesion between nanofiller and polymer

matrix. G. Serale et al., (2014) selected microencapsulated PCM filled with n-

eicosane paraffin wax, with phase transition temperature around 35 - 39 °C. The

disadvantage of this method is the like hood of subcooling issue to happen in

microencapsulated PCM due to greater heat transfer rate and greater contact surface.

Subcooling can be reduced by altering the encapsulation size, apply nucleating

agents or metal additives, improving the composition and shell structure, and by

varying the fill volume in the encapsulation (Khan et al., 2017). On the other hand,

Li et al., (2014) stated that form-stable PCM composites are produced by entrapment

6

of PCM into porous particles with absence of shielding coat on the surface. The short

coming is leakage of PCM will occur when the temperature is greater than the

melting temperature of PCM, thus the heat storage capacity will decrease.

In order to overcome these shortcomings, a form-stable composite PCM with

polymethyl methacrylate (PMMA) blending was developed in this work. Different

weight percentage of myristic acid and PMMA were tested to get a PCM with good

stability and latent heat storage. The ratio of myristic acid to PMMA are 20:80, 40:60,

60:40, 80:20, and 100:0. Based on reviewing some journals on usage of coating

together with blending method may yield better results in leakage prevention. It has

been decided to use nitrile butadiene rubber (NBR) and polyacrylic (PA) coating

layers to increase the physical and mechanical properties of coating to contain the

PCMs better.

1.3 Research Objectives

To overcome the problems encountered in producing form stable PCM, several

objectives are established. First of all, the objective is to produce form stable PCM

blended with PMMA and coated with NBR and PA. The next objective is to

characterize form stable PCM. Furthermore, the effect of PMMA blending and

coating on the performance of PCMs are evaluated by leakage test, thermal cyclic

and latent heat, with the aim to produce long lasting form stable PCMs. The

summaries of objectives of this study are:

1) To produce form stable PCM blended with PMMA and coated with NBR/PA.

2) To characterize the PCM blended with PMMA and coated with NBR/PA.

3) To evaluate the performance of the PCMs by leakage test, thermal cyclic and

latent heat.

7

CHAPTER 2

LITERATURE REVIEW

2.1 Classification of Phase Change Material (PCM)

In the light of phase change state, PCMs can be divided into three main categories

which are liquid-gas PCMs, solid-liquid PCMs and solid-solid PCMs. Among these

three categories, solid-liquid PCMs are the most suitable to be applied onto thermal

energy storage due to their light weight, has stable amount of latent heat, minimal

volume change compared to gas phase change materials and no considerations of

pressure involved (Cui and Riffat, 2011). The various form of solid-liquid PCMs are

inorganic PCMs, organic PCMs and eutectics (Zhou, Zhao and Tian, 2012). Several

reviews have been conducted with full classification of the most recent PCMs with

their thermos-physical properties provided in Figure 2.1 (Vadhera et al., 2018; Iten,

and Liu, 2014; Kapsalis and Karamanis, 2016).

8

Figure 2.1: Classification of PCM (Vadhera et al., 2018; Iten, and Liu, 2014;

Kapsalis and Karamanis, 2016).

2.1.1 Inorganic materials

Few examples of commercially used inorganic PCMs are alloys, eutectics, salt

hydrides, hydroxides and salts. Due to high solidification and melting range of

metallic PCMs, they are not being used widely for building application (Farid et al.,

2004).

The most famous inorganic PCMs are salt hydrates. They are applied

preferably because of their high latent heat storage, high thermal conductivity, and

tendency to lower the specific heats and compared to paraffin PCMs, salt hydrates

are more effective in volumetric density and thermal conductivity (Farid et al., 2004).

At first, the salt hydrate undergo dehydration process followed by the solid to liquid

phase change process which is analogous to freezing or melting process. Incongruent

or semi-congruent fusion often occurs with high rate of hydration. However, the

level of hydration increases if their fusion heat get higher. Salt hydrates also

demonstrate low crystallization rate, sub cooling effect, corrosive nature due to

leakage, incongruent melting and phase segregation during transition (Mehling and

Cabeza, 2008; PCM Price challenge, 2009; Hasan et al., 2016). To overcome the

shortcomings of phase segregation, the utilization of Bentonite clay and Glauber’s

9

salt, have been suggested by Wei Chiu et al., (2010). None the less, the rate of heat

exchange and crystallization will be reduced by using this combination. To achieve

the purpose to reduce the sub cooling effect, nucleating agent like Borax has been

proposed, but this involves some thickening agent to anticipate settling of the high

density Borax. Most of the other salt hydrates encounter the same problems.

Moreover, the volume change with the transition by an order of 10% is another

drawback of salt hydrates (Farid et al., 2004).

Some of the benefits of inorganic phase change materials are that they have

high and sharp phase change enthalpy, their latent heat of fusion is high, excellent in

terms of conductivity, minimal volume change during phase transition, inflammable,

low cost, compatible with plastic container and low environmental impact (Memon,

2014; Soares et al., 2013).

2.1.2 Organic materials

Paraffin wax is a type of organic material which has lower thermal conductivity than

hydrates of salt and their specific heats are high in both liquid and solid phase. This

is due to the fact that paraffin wax is made of saturated hydrocarbons. Paraffin PCMs

have no super cooling because of the fast rate of crystallization compared to salt

hydrates (Fortuniak et al., 2012).

Besides, there are plenty of non-paraffinic organic PCM classes, for instances,

esters, glycol, alcohols and unsaturated fats. Some of these PCMs have good latent

heat storage properties in building applications. Fatty acids have no super cooling

effects and the melting and freezing point of fatty acids are suitable for a solar based

applications. The general chemical form of fatty acids is CH3(CH2)2n-COOH. The

most suitable and noteworthy fatty acids for solar based applications are capric acid

(CA), lauric acid (LA), myristic acid (MA), palmitic acid (PA) and stearic acid (SA).

The main weakness of these materials is their low heat conductivity (Zhang et al.,

2014).

10

The employment of MA, PA and SA in domestic water heating system were

investigated by Hasan and Sayigh (2004). Those acids with purity of 95% have

transition temperatures in the range of 50-54⁰C, 58-62⁰C, and 65-69⁰C respectively.

When heated from 25⁰C to 80⁰C, those fatty acids show a volumetric expansion

more than 10%. The stated fatty acids release up to 10% heat of fusion after 450

thermal cycles which is approximately a year (Rathod and Banerjee, 2013). Farid et

al., (2004) have investigated the CA, LA, PA, and SA fatty acids binary mixtures and

thermal properties. These fatty acids have melting temperature of 30-65⁰C, and latent

heat of transition of 153-182 kJ/kg, which are crucial factor in designing the latent

heat thermal energy storage system. Evaluation of CA and LA mixture for low

temperature energy retention was done to determine the melting point of the mixture

of 14 ⁰C and latent heat of transition of 113-133 kJ/kg (Farid et al., 2004).

Fatty acids have some superior properties over other PCMs such as melting

congruency, good chemical stability, non-toxicity and suitable melting temperature

range for solar passive heating instruments (Teke et al., 2016). They also have high

latent heat and specific heat around 1.9-2.1 J/g⁰C and volume changes during phase

change process is low around 0.1-0.2ml/g (Rozanna et al., 2005). Besides, they do

not have any supercooling effects during phase transfer process. Fatty acids are

chemically stable, heat and colour stable, show low corrosion activity and nontoxic

due to the presence of carbonyl group (Feldman et al., 1995).

2.1.3 Polymeric PCM

Polymeric PCMs remain solid during the phase change process, hence it do not

involve any liquid or gas release. The issues of needing a sealed container are

irrelevant. Polyurethane and polybutadiene are used widely as polymeric PCM due to

their high thermal energy storage efficiency (Jamekhorshid et al., 2014).

According to Yanshan et al (2014), the usage of polyethylene glycol (PEG)

based cross-linked copolymer mixed with formaldehyde and melamine had shown

very good performance at various temperature ranges, good thermal stability, no

11

leakage, and fire proof. These features are vital to promote their practical application

as a PCM for thermal storage applications.

The study on Low Density Polyethylene (LDPE), glycerine and paraffin wax

as alternative material to be used as PCM has done by Robaidi (2013). In this blend,

small molecular weight species were dispersed in high molecular weight materials to

generate latent heat storage materials. Addition of paraffin wax; PEG and ethylene

glycol to LDPE reduces the melting temperature and increases melt flow index of the

material. The addition of glycerin to the polymer resin increases the enthalpy and

also acts as a crosslinking agent.

Pielichowska and Pielichowski (2014) examined polyethylene glycol (PEG),

an imperative semi-crystalline polymer which comprises of repeating unit of

dimethyl ether chains with hydroxyl-ended gatherings, OHCH2(CH2OCH2)nCH2OH

as PCM. It has the double feature of water dissolvability and organic solvency. The

substantial heat of fusion (117-170 kJ/kg) is corresponding to the molecular weight

and is ascribed to a high level of crystallinity. The melting point shifts from 4-70 ⁰C.

With all these features, it is appropriate to be applied in sun oriented thermal energy

storage (TES) frameworks with wide temperature range. PEG is used alone or in

blends with various compositions.

Polymeric PCMs act as suitable functional materials for latent heat thermal

energy storage due to their excellent features such as suitable melting and

crystallizing temperature range, congruent melting and solidifying behavior,

relatively high phase change enthalpy of fusion and solidification during its melting

or freezing temperature range and environmental friendly (Alkan et al., 2012;

Pielichowski and Flejtuch, 2003). Mochane and Luyt (2015) have studied on PCMs

based on polyolefins (Ethylene-vinyl acetate (EVA) and Polypropylene (PP))

blended with wax and mixed with expanded graphite (EG). The main aim of this

project is to enhance both the thermal conductivity and flame resistance of the shape-

stabilized PCMs. Sari and Karaipekli, (2007) investigated the correlation between

thermal conductivities of the PCMs with 2%, 4%, 7%, and 10% EG in paraffin wax

and increase of thermal conductivity of paraffin (0.22 W/m K) to 81.2%, 136.3%,

209.1%, and 272.7%.

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2.2 Differentiation of Various Types of PCMs

The advantages and disadvantages of various PCMs are listed in Table 2.1.

Table 2.1: Comparison of Different Types of PCMs (Cui and Riffat, 2011;

Kenfack and Bauer, 2014).

Classification Advantages Disadvantages

Organic PCMs 1. High heat of fusion

2. Chemically stable

3. Recyclable

4. Great compatibility with other

materials

5. No supercooling

6. Availability in a large temperature

range

1. Relatively large

volume change

2. Flammability

3. Low thermal

conductivity

Inorganic PCMs 1. High thermal conductivity

2. High heat of fusion

3. Low change in volume

4. Availability in low cost

1. Corrosion

2. Supercooling

Eutectics 1. High volumetric thermal storage

density

2. Sharp melting temperature

Lack of currently

available data of

thermos-physical

properties

2.3 Criteria of Selecting PCMs

Fatty acids, paraffin, eutectic mixtures and salt hydrates are the commonly used

PCMs as latent heat storage material for building and solar applications as a result of

their melting temperature (Madessa, 2014; Rozanna et al., 2015). Figure 2.2 indicates

the melting temperature and enthalpy of currently applicable PCMs (Diekmann,

2006).

13

Figure 2.2: Melting Temperature and Phase Change Enthalpy of Currently

Applicable PCMs (Diekmann, 2006).

Features such as kinetic, thermodynamics, chemical and economic properties

need to be taken into account in order to select the appropriate material in latent heat

storage system which is stated in Table 2.2. Figure 2.3 shows the schematic

representation of a phase change process.

Table 2.2: PCM Selection Criteria (Sharma and Kar, 2015; Sharma et al., 2009;

Cabeza et al., 2011).

Properties Criteria

Thermodynamics 1. High thermal conductivity

2. High latent heat of fusion per unit volume

3. High specific heat and high density

4. Desired range of melting temperature

5. Small volume changes during phase transformation and small

vapour pressure at operating temperatures to reduce

containment problems

6. Congruent melting

14

Kinetic 1. High nucleation rate to avoid super cooling

2. High rate of crystal growth to meet demands of heat recovery

from the storage system

Chemical 1. Chemical stability

2. No corrosiveness

3. No degradation after numerous number of freezing/melting

cycle

4. No toxic, no flammable and no explosive material

5. Completely reversible freezing/melting cycle

Economic 1. Large scale availabilities

2. Cost effective

Figure 2.3: Schematic Representation of a Phase Change Process (Mochane, 2011).

15

2.4 Solar Renewable Energy

Renewable energy is originated from the nature, example, sunlight, wind, geothermal

heat, and rain, which they are naturally replenish. The technologies that are invented

to harvest the renewable energy are hydroelectric generation, solar power, wind

power, biomass and biofuels for transportation.

In recent years, the terms ―renewable energy‖ and ―alternative energy‖

become more significant because the global energy demand surge indicates faster

rate of depletion of conventional energy resources. Renewable energy can be defined

as energy generated from natural processes that are endlessly replenished. This

energy impossible to use up and is continuously renewed. On the other hand,

alternative energy is defined as alternative energy source compared to fossil fuels. It

usually used to categorize energies that are unconventional and have minimal

environmental effect. As comparison, alternative energy may not have significant

environmental impact, whereas renewable energy may or may not harm the

environment (Ciolkosz, 2017).

The sun is the major source of renewable energy nowadays. Researchers are

finding ways to make use of solar radiation by transforming it into valuable heat or

electrical energy. The common types of solar energy systems are photovoltaics, and

thermal systems (Kabir, 2018). Photovoltaic produces energy by conversion of solar

radiation using silicon panels, which produces electricity when light energy is

absorbed. Thermal systems is used to keep heat from the sun to be used for various

functions, by application of active systems, such as solar hot water heaters with

pump, and passive systems, for example auto temperature regulating building that

retain and utilizes solar energy. Glass house is suitable for passive system, where it

can gather solar heat on bright days during winter and use it to warm up the house at

night (Gupta and Tiwari, 2016).

The core benefits of solar energy are it is renewable, clean energy, and

independent operation or integration with conventional energy sources. The key

drawbacks are it is more costly than conventional energy, and the inconsistency of

availability of solar radiation daily and in seasons (Mohtasham, 2015).

16

2.5 Thermal Energy Storage

Thermal energy storage (TES) is a process where a medium stores heat energy when

the heat is available, and discharges it when the heat is scarce. This application is

useful in solar facilities. Heat can be kept in constituents in the form of sensible,

latent and thermo-chemical where alteration of temperature, phase or chemical

composition occurs. Sensible heat storage has been extensively studied but it has

drawbacks in its application. According to Alva et al., (2018), the main disadvantage

of sensible TES materials is the stability of temperature when releasing energy.

When the thermal discharge is ongoing, the outlet temperature of the heat transfer

fluid decrease with time. This is also due to sensible TES requires a large volume of

100 L per day to 1000 L per day of storage tank needed. As for latent heat storage,

the drawback is poor thermal conductivity. The thermal conductivity of salt PCMs

are between 0.5 W/m.K and 1 W/m.K, whereas organic PCMs are between 0.1

W/m.K and 0.3 W/m.K. The utilization of phase change materials (PCMs) allow

storage of latent heat, in which the phase switch from solid to liquid to collect latent

heat. This enables a compact, effective and low cost operating system. For thermo-

chemical heat storage (TCS) method, it is at the infant period of research although it

caught the attention of the society for its long term energy storage application (Zhang

et al., 2016).

TES system is able to decrease the levelized cost of electricity (LCOE) of

renewable energy systems, where the storage medium temperature is the parameter

that influences the most. Sensible TES is practically used at large scale (Badenhorst,

2018). Inorganic PCMs latent heat storage is normally applied in high temperature

applications. PCM and TCS storage media require encapsulation of suitable materials,

possible containment constituents are studied.

The sensible TES used hot water buffer storage tank of large volume, which

functions to save energy in water heater by utilizing on solar energy and in co-

generation energy supply systems. Hauer, (2013) revealed that water tank storage is

an economical selection, due to the increase of effectiveness by ideal water

stratification inside the tank and decent thermal insulation, such as an evacuated

super-insulation with a thermal loss of λ = 0.01 W/mK at 90°C and 0.1 mbar

17

improved system integration. This technology is suitable to apply in countries with

different seasons to provide heat domestically. The district system and heating

installations are connected to the living area to avoid temperature drop at heat

exchangers and escalates the temperature distribution. The heat exchanger has hot

stream of 60°C with a cold stream of 30°C. The seasonal storage has a broad

operating temperature spectrum between 10-90°C (Pawar, 2015).

Next, the underground TES is a long term seasonal storage because of its

great thermal inertia. It exists in several forms, such as borehole, aquifer, cavern and

pit. The application of underground TES is subject to the geological circumstances. It

is an active energy storage system. Underground TES is able to provide 13-15% of

the overall space heating demand in Sweden, but the possible damages to the

environment are leakage of thermal energy carriers, biological and chemical harm on

the water source, ecological impact and contamination (Lim, 2013).

Subsequently, the Phase Change Material (PCM) based TES has high energy

storage capacities and target oriented discharging temperatures (Sarbu and

Sebarchievici, 2018). PCMs are suitable for short-term and long term energy storage.

PCMs can capture extra energy at the peak of sun irradiation, and kept for use during

absence of solar irradiation. Application of PCM in the building wall can store heat

during morning and discharges heat to the room at night, which improves the thermal

comfort for a low temperature region (Guo and Pang, 2016). The trend of PCM cost

is expected to decline PCM development matures, nevertheless PCMs that are not

used up throughout the operation will not affect the heat capacity even it faced

extended charging-discharging cycle (Wani and Loharkar, 2017).

Thermo-chemical storage (TCS) has high energy density and huge storage

capacity. It applies the concept of reversible reactions that require discharge and

charging of energy for TES. The example of TCS is adsorption for heat storage and

moisture control. For instance, adsorption of water vapour to micro-porous

crystalline alumino-silicates silica-gel or zeolites, and lithium-chloride open sorption

methods to decrease water temperature and utilizes zeolites to adjust humidity

(Hauer, 2013). The different TES technologies: sensible heat; latent heat; and

thermo-chemical shown in Figure 2.4.

18

Figure 2.4: The storage capacity of various composites (Sarbu and Sebarchievici,

2018).

2.6 Form stable PCM

A form-stable PCM is a composite structure comprises of solid-liquid PCMs which

act as latent heat thermal storage material and encapsulated with a supporting

material (Silakhori et al, 2015). During the event of increase in surrounding

temperature where the PCM undergoes transformation from solid state to liquid state,

the inorganic or polymer coating will act as supporting material to inhibit leakage or

changes in shape, Besides that, a good form-stable PCM must have a lesser amount

of leakage whereby, the mass before and after the thermal cycle process of the form-

stable PCM must not have great differences. The efficiency of the thermal storage

highly depends on the total mass leakage percentage, as the latent heat of the form-

stable PCM can be verified from the total mass leakage percentage. Therefore, the

total leakage is considered to be the most significant feature to decide the type of the

coating and appropriate coating technique (Huang et al., 2013).

19

2.6.1 Encapsulation Method

Fatty acids such as stearic acid (SA), palmitic acid (PA), myristic acid (MA), and

lauric acid (LA) are promising PCMs for latent heat thermal energy storage (LHTES)

applications but the major drawback of utilizing fatty acid is their leakage which

causes corrosion in LHTES applications (Kosny, 2015; Sari and Kaygusuz, 2003;

Murali et al., 2015). The use of fatty acids as form-stable PCM will increase their

feasibilities in practical LHTES applications due to reduced corrosion in the energy

storage system.

Alkan and Sari, (2008) had prepared new kinds of form-stable PCMs of fatty

acid/polymethyl methacrylate (PMMA) for LHTES systems by encapsulation of the

fatty acids (SA, PA, MA, and LA) in PMMA. It was concluded that the form-stable

fatty acid/PMMA can be considered as candidate PCMs for LHTES applications

such as under floor space heating of buildings and solar energy storage using

wallboard and plasterboard impregnated with form-stable PCM due to having good

thermal properties which is shown in Table 2.3. The compatibility of fatty acids with

the Eudragit S (a brand name for PMMA) is proved by microscopic investigation and

infrared Fourier Transform Infrared Spectroscopy (FTIR). The thermal properties

measured by Differential Scanning Calorimetry (DSC) method of the form stable

PCMs are as shown in Table 2.3. The maximum mass percentage of all fatty acids in

the form-stable PCMs is 70%, and no leakage of fatty acid is observed at the

temperature range of 50—70⁰C from 0 to 1000 heating cycles (Alkan , 2008; Kant,

Shukla and Sharma, 2016; Sari et al., 2006). Eudragit is the brand name for a diverse

range of polymethacrylate-based copolymers, which includes anionic, cationic, and

neutral copolymers based on methacrylic acid and methacrylic/acrylic esters or their

derivatives (Thakral et al., 2012).

20

Table 2.3: Thermal Properties of Fatty Acids, Eudragit S/Fatty Acid Blends

(30/70 wt%) as Form-stable PCMs (Alkan, 2008).

Phase Change

Material

Melting

point (oC)

Heat of fusion

(J/g)

Freezing

point (oC)

Heat of freezing

(J/g)

Myristic acid

(MA)

51.80 198.14 51.4 181.83

Palmitic acid

(PA)

60.42 233.24 59.88 237.11

Stearic acid

(SA)

66.82 258.98 66.36 262.32

Eudragit

S/MA

51.82 132.47 50.47 133.01

Eudragit S/PA 59.60 170.64 59.26 170.92

Eudragit S/SA 66.70 184.22 65.43 184.88

2.6.2 Shape-stabilized Encapsulation Method

In order to prepare novel shape-stabilized PCMs, Sari and Kaygusuz (2003) have

investigated the compositions of such fatty acids as LA, MA, PA and SA as PCM

and poly(vinyl chloride) (PVC) as supporting material. Table 2.4 shows that the

maximum composition ratio of all fatty acids in the shape stabilized PCMs was 50 wt%

in which no leakage of fatty acid was observed over their melting temperatures for

several heating cycles. The miscibility of fatty acids with the PVC and the interaction

between the blend components which are responsible for the miscibility has been

proved by microscopic investigation and Infrared (IR) spectroscopy. The melting

temperature and the latent heat of fusion of the shape stabilized PCMs are measured

by DSC analysis method. The melting temperatures and latent heats of the shape-

stabilized PVC/LA, PVC/MA, PVC/PA and PVC/SA (50/50 wt%) PCMs

are determined as 38.8⁰C, 49.2⁰C, 54.4⁰C and 64.7⁰C, and 97.8 J/g, 103.2 J/g, 120.3

J/g and 129.3 J/g, respectively. The results indicate that the PVC/fatty acids blends as

shape-stabilized PCMs have great potential for passive solar thermal energy

21

applications in terms of their reasonable thermal properties and advantages of easy

preparation with desirable dimensions and direct application in LHTES applications

(Sari and Kaygusuz, 2003).

Table 2.4: Thermal Properties of Some Fatty Acids and Form-stable

Compositions (Sari and Kaygusuz, 2003).

Phase Change Material Melting point (oC) Heat of fusion (J/g)

Lauric acid (LA) 42.6 183.2

Myristic acid (MA) 52.8 198.4

Palmitic acid (PA) 62.4 224.8

Stearic acid (SA) 69.8 238.6

PVC: LA (50 wt.%: 50 wt.%) 38.8 91.6

PVC: MA (50 wt.%: 50 wt.%) 49.2 99.2

PVC: PA (50 wt.%: 50 wt.%) 54.4 112.4

PVC: SA (50 wt.%: 50 wt.%) 64.7 119.3

Kaygusuz et al., (2008) prepared and investigated novel shape PCMs by

introducing fatty acids; SA, PA and MA in an acrylic resin (Eudragit E) as

supporting material. The blends of Eudragit E with fatty acids were prepared by the

solution casting method. Eudragit E and one of the fatty acids in chloroform were

dissolved in separate beakers, and fatty acid solution was added to Eudragit E

solution dropwise. Then, the blend was casted at room temperature for 15 days. The

blends were prepared at 40, 50, 60, 70, and 80% w/w fatty acid compositions to

obtain the maximum encapsulation ratio without leakage of the fatty acid from the

blends when the blend was heated above the melting points of MA, PA, and SA. The

maximum percentage of all fatty acids in the shape-stabilized PCMs was found to be

70 wt.% in which no fatty acid leakage was observed as the blends were heated

above the melting points of the fatty acids. The melting and freezing temperatures

and latent heats of the shape-stabilized PCMs were measured by the DSC method

and the results were presented in Table 2.5 (Kaygusuz et al., 2008).

22

Table 2.5: Thermal Properties of Fatty Acids and 30% Eudragit E/70%

Fatty Acid (w/w) Blends as Form-stable PCM (Kaygusuz et al., 2008).

Phase Change

Material

Melting point

(oC)

Heat of fusion

(J/g)

Freezing point

(oC)

Heat of freezing

(J/g)

Myristic acid

(MA)

51.80 178.13 51.74 181.63

Palmitic acid

(PA)

60.42 233.24 59.88 237.11

Stearic acid

(SA)

66.82 258.98 66.36 263.32

30% Eudragit

E/ 70% MA

51.44 135.62 51.11 134.02

30% Eudragit

E/ 70% PA

58.74 172.43 58.22 172.86

30% Eudragit

E/ 70% SA

65.41 185.64 65.08 185.83

PCMs require special LHTES devices in different shapes or elements

such as shell and tube PCM heat exchanger or a lot of containers to encapsulate

them since they change from solid to liquid during the energy storage period

(Kuboth et al., 2017). Although the use of such materials solved the problem of

PCM leakage during solid-liquid phase change, it increases the heat resistance

and the cost of the LHTES system. However, these problems can be overcome

using form stable PCM which can be prepared by encapsulation of PCM into a

polymeric structure (Agarwal and Sarviya, 2016). Thus, the main advantages of

using shape stabilized encapsulated PCMs are no leakage of melted PCM during

phase transition process, no additional storage container for encapsulation, and

thus reducing the cost of LHTES system, eliminating the thermal resistance

caused by capsule shell, reducing the reactivity of PCM with the outside

environment, controlling the volume change of the PCMs during the solid-liquid

phase change and ease of preparing it in desired dimension (Khudhair and Farid,

2004; Farid et al., 2004).

23

Xing et al, (2006) had analyzed the thermal and hydrophilic-lipophilic

properties of form-stable high density polyethylene (HDPE)/paraffin PCM

encapsulated in silica gel. The authors proposed this PCM for use in the building

field because of its good thermal properties and better hydrophilicity and fire-

proofing properties.

On the other hand, PMMA is a group of commercially available acrylic resin

and is fully polymerized methyl methacrylate. It has high impact strength and

chemical resistance in addition to optical clarity. These properties make it a

potential encapsulation material for PCMs (Ramrakhiani, Parashar and Datt, 2005).

2.6.3 Microencapsulation Method

Giro-Paloma et al (2016) have researched about the different types of PCM, the

different shell materials used, the methods of encapsulation, the most used

techniques for their characterization, and the main applications

of microencapsulated PCM (MP CM). Both natural and synthetic polymers can be

used as shell material depending on the requirements and considerations of the

PCM applications. The authors also stated that the combination of core/shell is

one of the most important parameters in microencapsulation. The morphology of

the microcapsules in MPCM can be very diverse (irregular shape, simple, multi-

wall, multi-core, or matrix particle), and there are four types of MPCM

(mononuclear, poly nuclear, matrix encapsulation, and multi-film).

The most common microencapsulate shell materials for PCM

reinforcement are melamine and urea formaldehydes, polyurethane, HDPE,

styrene butadiene styrene copolymer and PMMA. PMMA is a transparent

thermoplastic which is easily available. It has modest

properties, simple processing, good impact strength, relatively high chemical

resistance and cheap. Thus, PMMA is a promising polymer as shell material

containing PCM for TES applications (Wang et al., 2011). The authors also

created a sequence of PMMA microcapsules containing capric acid/lauric

24

acid, capric acid/myristic acid, capric acid/stearic acid and lauric

acid/myristic acid eutectics work as the heat-absorbing materials using the

technique of self-polymerization (Wang and Meng, 2010).

2.6.4 Crosslinked Polymer Coating Method

Mochane (2011) had investigated the morphology and properties of polypropylene

(PP) containing crosslinked polystyrene (PS) encapsulated paraffin wax. The

research shows that the thermal properties such as melting points (Tm), onset

temperatures of melting (Tom), and melting enthalpies (∆H) were strongly affected

by the use of crosslinking agents (Mochane, 2011).

Oliveira and Costa, (2010) focused on optimization of process conditions,

characterization and mechanical properties of silane crosslinked HDPE. The

crosslinking process resulted in the formation of PEX (crosslinked high density

polyethylene) from HDPE. In addition, the crosslinking can extend the use of PE by

raising its operating limit to high temperatures such as 2000C and improving its

mechanical properties, due to formation of three dimension chain network structure.

It was stated that this structure ensures higher tensile strength and improves hardness

and chemical resistance, as well as dimensional and thermal stability of the polymer

(Oliveira and Costa, 2010).

Zhang et al., (2006) developed form-stable PCMs for building applications.

Paraffin with the melting point of 200C and 60

0C was chosen as PCM. As for

supporting material, HDPE/ styrene butadiene styrene copolymer (SBS)/graphite

composite were used. In the latter, each component played a different role: powder-

like HDPE endowed PCM rigidity; SBS absorbed the paraffin strongly while it was

in liquid condition and graphite acted as a thermal conductive component. The

paraffin and the supporting material were mixed evenly and coextruded at about

140⁰C in a two-screw extruder. The shape of the product-plate, rod, pellet, etc.

varied according to the different application manner. In order to prevent the possible

leakage of paraffin, the surface of composite material was grafted and crosslinked.

25

Despite of paraffin’s condition (liquid or solid), the polymer network stands still to

support the shape (Zhang et al., 2006).

2.7 Coating

The purpose of coating is to cover the surface of a product or substance. The most

general method of coating using polymers is known as conformal coating. Conformal

coating enhance in operational integrity of a product, safeguard the product from heat,

moisture, corrosion, contamination and lengthen the product life (Flitney, 2009).

Leakage prevention of fatty acid and corrosion prevention of the internal system of

the solar water heater are the key reasons to coat PCM (Kong et al., 2016). Silicon

coating, acrylic coating, epoxy coating, parylene coating and polyurethane coating

are the five main categories of conformal coating. Selection of coating method is

fully dependent on the operational requirements and product applications. Acrylic

coating is chosen because of its chemical resistant property, cost effective, high

melting point and vast availability (Inc., 2017).

2.7.1 Coating Application Methods

There are six coating methods for acrylic coating in general, which are automated

spraying, manual spraying, selective coating, brushing, vapour deposition and

dipping.

In automated spraying, a modified spray system that moves the object on a

conveyor under a responding spray head used to apply coating. Coating application is

normally trailed by an oven that quickens the curing so it can be done rapidly

(Koleske, 2012).

Secondly, for manual spray coating, coating can be applied by an aerosol can

or hand held spray gun. It is largely utilized for low volume production when costly

26

hardware is not accessible. This technique can be tedious on the grounds that regions

not requiring coating should be masked. It is likewise operator dependent, so

variations are common (Aziz and Ismail, 2015).

Subsequently, in selective coating method, an automated procedure that

utilizes programmable mechanical spray nozzles is used to apply the coating to each

particular part of the object. Usually this process is chosen for large production

(Barriga et al., 2014).

Whereas in brushing, it is a basic application method utilized fundamentally

in repair. The conformal covering is applied with a brush to particular zones on the

object. It is cost effective, but labour intensive and highly variable technique, and it

is most appropriate for little production runs (Wang et al., 2003).

2.7.2 Coating of Phase Change Material

A recent study of coating of melamine formaldehyde PCM microcapsules with silver

layer was done by Cao et al (2015). This coated material is dispersed into

polyalphaolefins (PAOs) to produce a high thermal conductivity fluid. Xu et al (2014)

had carried out a study on coating PCM microcapsules with silver in an ammonia

aqueous solution. The thermal conductivity of PCM microcapsules was increased

from 0.152 to only 0.251W/m.K. Furthermore, the latent heat reduced from 42.6 to

32 J/g. It is obvious that there is a need to enhance the thermal conductivity of PCM

microcapsules further without reducing its latent heat. Besides, it has been reported

that silver coating cannot be achieved successfully without activation and

sensitization (Gao and Zhan, 2009).

Coating of PCM microcapsules with a metal using dopamine surface

activation followed by electrolyte plating was studied by Al-Shannaq et al (2016).

This method is done to overcome the low thermal conductivity of the microcapsules

shell. It was stated that the silver coating was used to enhance the thermal

conductivity of the PCM microcapsules. The apparent thermal conductivity was

27

decreased with decreasing the size of the microcapsules. The measured apparent

thermal conductivity of the PCM microcapsules increased significantly by metal

coating from 0.189 to 2.41 W/m K.

A novel composite for heat sink application was done by Stappers et al

(2005), where rapid heat dissipation application were prepared by integration of

PCM in electrodeposited of copper metals. In this research, copper coating with 35

vol% of integrated PCM have heat absorption capacity of 10.9 J/g. For other PCMs

such as hydrated salts, microencapsulation might be used to prevent contact between

the PCM and the metal in composite coatings, because this would lead to corrosion

of the metal coating. This coating method of microencapsulated PCM is always

feasible due to the difficulties of producing pure PCM particles or due to chemical

incompatibilities between the PCM particles and the metal coating.

According to Kee et al., (2017), solution blending nanocomposites displayed

improved overall properties than in situ polymerized nanocomposites because of the

better dispersion of reduced graphene oxide (RGO) in solution blending.

RGO/polymethyl methacrylate (PMMA) nanocomposites with 0.5 wt% loading

increased the Young’s modulus from 330.47 MPa to 463.02 MPa and tensile strength

from 35.89 MPa to 36.64 MPa, but decreased the elongation at break from 15.10% to

10.02%. This is due to the good dispersion of RGO in the nanocomposites.

A novel composite PCM particle with a coating film, through paraffin

integrated with expanded perlite (EP) by vacuum adsorption to prevent leakage

problem. It is stated that the best proportion of paraffin in PCM were determined to

be 47.5 wt% because this proportion does not have any leakages when the PCM

melts (Kong et al., 2016). Moreover, the phase change temperature and latent heat of

coated PCM were measured to be 21.6 ⁰C and 56.3 J/g. The latent heat released by

the pure paraffin wax is 171.4 J/g (Sun et al., 2017). The latent heat released by the

coated composite PCM is very low compared to the latent heat of pure paraffin wax.

Kee et al., (2017) have studied the use of two coatings, which are polyacrylic

coating and conformal coating to overcome the leakage problem of composite PCM

comprising of polymethyl methacrylsate (PMMA) and myristic acid (MA) in

28

different weight percentage. There are no leakages occurred to the composite PCMs

with coatings compared to those without coating under the same ratio of PMMA/MA.

The two coatings improved the thermal stability, thermal reliability of composite

PCM after 1000 times thermal cycles, as well as the latent heat only decreased 0.16%

and 1.02% for the PCMs coated with conformal coating and polyacrylic coating

correspondingly.

2.8 Stability of Non-paraffin Organic PCMs

The most common and abundant non-paraffin organic PCMs are fatty acids. They are

being commercially used because of their proper phase change temperature and high

range of heat of fusion. They are easily available because they can be derived from

various sources of vegetable and animal oils. Thus, the supply is continuous unlike

the shortage of other fuel sources (Chuah et al., 2015). The thermal stability and

thermal cycle tests of various types of fatty acids had been investigated by many

researchers.

Thermal reliability test on a mixture of industrial grade MA, LA, PA and SA

were carried out by Sari, (2003). The melting points of those fatty acids are 53⁰C,

61.31⁰C, 54.7⁰C, and 42.46⁰C respectively. The fatty acids were subjected to 1200

melt/freeze cycles to determine the latent heat thermal energy storage (LHTES)

characteristics. It was reported that the examined fatty acids had shown convincingly

good thermal stability in terms of melting temperature and latent heat. The melting

temperature of the mixture was nearly the same in the range of 40.78-42⁰C and the

latent heat also had shown nearly the same trend in the range of 174.47-175.34 J/g

from 0 number of thermal cycle to 1200 times.

Furthermore, study of thermal stabilities of industrial grade MA, PA and SA

with 95% purity were conducted by Sari and Kaygusuz (2003). Differential Scanning

Calorimetry (DSC) was used to evaluate the phase transition temperature and latent

heat storage capacity of those PCMs by running continuous thermal cycles of 40, 410,

700 and 910 times. The findings showed that appropriate fatty acid PCMs which can

29

be used for long term basis in solar based systems are MA and PA because of their

low melting and freezing temperature which are 52.5⁰C and 61.2⁰C respectively and

high latent heat of fusion around 182-200 J/g (Sari, 2003; Sari and Kaygusuz, 2001;

Sari and Kaygusuz, 2002). Furthermore, the corrosion resistant of some containment

materials such as stainless steel (SS304L), carbon steel (Steel C20), aluminium (Al)

and copper (Cu) towards fatty acids over a long period of time in contact was also

tested. In this study, it was revealed that stainless steel (SS304L) with chromium

oxide (Cr2O) surface layer and aluminium (Al) metals with aluminium oxide (Al2O3)

surface layers have good resistance towards fatty acids.

2.9 Challenges to Produce Good Coating

The advantages of a good coating are adequate surface area for heat transfer, capsule

walls protect against destructive environmental reactions, and ease of handling. The

challenges to fabricate a rigid coating are high chemical corrosion when in contact

with metal shell, and expand in volume when transition of phase from solid to liquid

occur (Nomura et al., 2015).

Zhang et al., (2014) suggested to use chromium periodic-barrel electroplate

and nickel barrel-plating to encapsulate chromium-nickel (Cr-Ni) bi-layer on Cu-

based PCM. The outcome displayed that the capsule is able to withstand thermal

cycles without leakage, and demonstrated stability between the core and Cr-Ni shell.

The disadvantage is the shell has large thickness and storage density (50 J/g) was as

low as 20 wt% of its pure form.

Mathur et al., (2013) stated that leaving a void in the shell to permit volume

expansion of PCM. The sodium nitrate (NaNO3) PCM pill produced with voids by

integrating a sacrificial polymer at the middle layer between the PCM capsules and

the shell.

30

Thus, in order to get rid of the leakage problem, an elastic coating with

sufficient tensile strength and adequate thickness that the latent heat will not be much

affected will be studied in this work.

2.10 Applications of PCMs

An effective usage of PCMs does not only concentrate on high energy storage.

However, it is very crucial in charging and discharging the energy storage with a

thermal power which is pertinent for desired application. The low thermal

conductivity of the materials used as PCMs is one of the main disadvantages of latent

thermal energy storage. This disadvantage restricts the power which can be extracted

from thermal energy storage. The ability of PCM to absorb and release energy during

the essential time makes it to be useful in many fields. Currently, the researches

about those materials keep increasing due to their benefits in energy systems (Giro-

Paloma et al., 2016).

Over the years PCMs has been used in many industries such as packaging,

food, buildings, textiles, medical therapies and many more. Ever since 1980, PCM

have been deliberated in TES. Climatization is considered as one of those

applications for PCM (Oro et al., 2012). According to Gil et al., (2014) PCMs has

large potential usage in solar cooling. Oro et al (2013) carried out research on the

effect of PCM introduction in freezer states that it enhances the quality of ice cream.

Those types of materials can be included in the container drinks to store energy.

Besides, the energy was released when the systems require energy. The research

conducted by Oro et al., (2013) focuses on thermal performance of PCMs and the

compatibility of PCM with metallic materials used to store food stuffs.

The effect of temperature storage conditions using PCM has been studied for

a number of food products such as vegetables (Cruz et al., 2009), frozen dough

(Phimolsiripol et al., 2008), ice cream, and meat (Duun et al., 2008; Yanniotis et al.,

2008). It has been stated that it is important to maintain stable temperatures in the

storage and transportation of frozen foods. This is to maintain the quality and

31

lifetime of the product. In general, frozen foods must be kept below 18⁰C. This

temperature should be maintained right in freezers and it can be achieved with the

aid of PCM integrated refrigerator systems. Nevertheless, during storage and

transportation, frozen foods may undergo temperature fluctuations due to heat loads

imposed on the system. In order to overcome this issue, Gin and Farid, (2010) had

studied the effect of PCM panels placed against the internal walls of a freezer. They

stated that the comparisons of the freezer air temperature and product temperature in

a freezer containing PCM panels showed lower temperature fluctuations than in a

freezer without PCM.

PCMs had also been used in automobiles. Diesel is used as a source of energy

due to the extremely costly operation of refrigerated trucks. The price of diesel-

generated energy is 6 times higher compared to conservative electricity price

(Materials PCM, 2016). PCM is already used today in a latent heat battery offered by

BMW as optional equipment in its 5 series. When the motor runs at the operational

temperature, the storage material will be connected to the radiator and keeps

excessive heat. To achieve interior driving comfort, the heat which is available at the

next cold start will heat up the motor rapidly. The latent heat battery has an

exceptional insulation where it could preserve the energy at 200⁰C for 2 days.

Moreover, PCM can also be utilized in tail pipes like exhaust of vehicles as an

addition to this application. Excessive hydrocarbon emission during vehicle start-up

will be reduced by keeping the catalytic converter at its design temperature

(Pielichowski and Flejtuch, 2003).

During the course of the day, the atmosphere in a room is found comfortable

by its occupants if it differs a little compared to the environment outside the room.

Due to this factor, the thick walls in homes are very comfortable in all types of

weathers. It is suggested to implement materials made up of PCM as wall which is

able to mimic the purpose of thick walls from traditional building materials. This will

ensure the realization of comfort with less massive constructions (Zalba et al., 2003).

PCMs are also used in greenhouses. In order for plants cultivate in a greenhouse to

flourish, it is essential to keep the temperatures in the greenhouse in small range.

Many of the greenhouses need air-conditioning or heating because of large

temperature swings in daytime and night time temperatures. The dependence on air-

32

conditioning or heating is reduced or removed when the PCM is fixed in floor of

such greenhouses (Bentz and Turpin, 2007).

33

CHAPTER 3

METHODOLOGY

3.1 Materials

Polymethyl methacrylate, PMMA (120, 000 molecular weight) was purchased from

Sigma Aldrich, Subang Jaya, Malaysia. Myristic acid (purity ≥ 98%), and chloroform

(stabilized with 0.6-1.0% ethanol) were purchased from R&M Chemicals, Semenyih,

Malaysia. Nitrile butadiene rubber (NBR) coating (Total solid content of 44.70%)

was purchased from Synthomer, Kluang, Malaysia. Polyacrylic (PA) coating (Total

solid content of 36.35%) was provided by Dr. Chee Swee Yong from Faculty of

Science, UTAR.

3.1.1 Experiment Flow Chart

The experimental flow chart for this research work is shown in Figure 3.1.

34

Figure 3.1: Overall Flow of Methodology.

3.2 Preparation of PCM

3.2.1 Preparation of PCM Blending

The phase change material (PCM) was prepared by solution blending method.

PMMA was dissolved in a fixed amount of chloroform with a ratio of 100ml of

chloroform to 1g of PMMA powder in a beaker. The solution was stirred using the

aid of hot plate magnetic stirrer (Model: Stuart SB 162-3) at room temperature about

25⁰C until all the PMMA powder are completely dissolved. Myristic acid was

dissolved in a fixed amount of chloroform with a ratio of 5ml of chloroform to 1g of

myristic acid powder in a beaker. The solution was stirred using the aid of hot plate

magnetic stirrer (Model: Stuart SB 162-3) at room temperature about 25⁰C until all

the myristic acid powder are completely dissolved, shown in Figure 3.2. Then, the

PMMA solution is poured into a separating funnel fixed on a retort stand. The

Preparation of PCM Blending with

PMMA

Pelletizing of PCM

Coating of Polyacrylic and Nitrile Butadiene Rubber on PCM through Dip Coating Method

Characterization and Performance

Fourier Transform Infrared

Spectroscopy

(FTIR-ATR)

Differential Scanning

Calorimetry (DSC)

Tensile Test Leakage Test

35

myristic acid solution is poured into a Teflon folded container and placed on the hot

plate magnetic stirrer. The hot plate magnetic stirrer speed is set at 4, and at the same

time the PMMA solution in the separating funnel is dripped dropwise to ensure even

mixing, shown in Figure 3.3. After all the PMMA in the funnel is consumed, the

mixture was continuously stirred for 30 minutes to ensure well mixing. The surface

of the container inside the fumehood was completely covered using aluminum foil

sheets to prevent contamination, shown in Figure 3.4. Formulations of PCMs are

shown in Table 3.1.

Table 3.1 Formulation of PCM samples.

Sample Percentage (%) Coating

Myristic acid PMMA

PCM20 20 80 NBR layered with PA

PCM40 40 60

PCM60 60 40

PCM80 80 20

PCM100 100 0

Figure 3.2: The process of stirring the PMMA and MA in chloroform.

36

Figure 3.3: Setup of the mixing process.

Figure 3.4: The drying process of the mixture solution.

Figure 3.5: The formation of phase change material blending composition.

37

The controlled variables of this process are the stirring speed, volume of

chloroform, temperature of the solution, and stirring time. All these factors must be

taken into consideration and fixed in a minimum amount while preparing the solution

to prevent under or over mixing. In this study, the volume of chloroform has fixed to

be 100ml for 1g of PMMA, stirring speed of 4, process temperature at 25⁰C, 30

minutes of stirring time and the surface of beaker was closed with aluminium foil.

The volume of chloroform has fixed to be 5ml for 1g of myristic acid, stirring speed

of 4, process temperature at 25⁰C, 30 minutes of stirring time and the surface of

beaker was closed with aluminium foil.

The duration of drying is 24 hours, until it completely dried to form powder

as shown in Figure 3.5. The dried sample is scrap out of the Teflon container and

crush into smaller size using spatula to form the powder. The PMMA solution was

blended with different weight percentage of myristic acid solution (20%, 40%, 60%

and 80%) and dissolved completely in the chloroform solution.

3.2.2 Pelletizing of PCM

The PCM was originally in powder form. In order to cast it into a disc shape, the

Fourier Transform Infrared Spectroscopy (FTIR) presser was used. At first, the dry

powder of PCM was measured using a weighing machine, with the model number

Sartorius AX224. The weight range was from 0.2750 to 0.2800 g for each sample.

Then, parts of the presser were cleaned with absolute ethanol to remove impurities to

reduce contamination of PCM. After that, the dry powder sample was poured into the

die and pressed to 4000 kPa. When the pressure dropped to 3800 kPa, the die was

removed from the presser. The pellet was removed from the die, weighed and

recorded. The FTIR presser and die are shown in Figure 3.6 and 3.7.

38

Figure 3.6: FTIR presser.

Figure 3.7: The die.

3.3 Coating of Polyacrylic and Nitrile Butadiene Rubber on PCM through Dip

Coating Method

The PCMs were coated using dip coating method. Nitrile butadiene rubber (NBR)

coating solution has total solid content of 44.70%, and the total solid content of

polyacrylic (PA) coating solution is 36.35%, shown in Figure 3.8. A small pellet of

myristic acid was dipped into NBR coating solution at fixed immersion time of 5

seconds with the aid of forceps. The coated samples were placed on Teflon sheet and

dried in fumehood at room temperature with the blower switched on for 3 days. Then,

39

the dried sample was flipped to the other side and dipped into NBR coating solution

at fixed immersion time of 5 seconds with the aid of forceps, and placed on Teflon

sheet to dry in fumehood at room temperature with the blower switched on for

another 3 days. After the NBR layer was dried, the sample was dipped into PA

coating solution at fixed immersion time of 5 seconds with the aid of forceps. The

coated samples were placed on Teflon sheet and dried in fumehood at room

temperature with the blower switched on for 3 days. After the first layer of PA

coating was dried, the sample was flipped to the other side and dipped into PA

coating solution at fixed immersion time of 5 seconds with the aid of forceps, and

placed on Teflon sheet to dry in fumehood at room temperature with the blower

switched on for 3 days. These steps were done to ensure the front and back of the

pellet was well coated. The mass and the thickness of the pellet was recorded after

each of the step was done. Figure 3.9 shows the sample preparation of dip coated

PCM on Teflon sheet.

Figure 3.8: The NBR coating solution (left) and PA coating solution (right).

Figure 3.9: The PCM sample preparation on a Teflon sheet.

40

A grid was drawn in a Teflon sheet to place the form-stable PCM. This is

because the coating of NBR layer on PCM will stick on the other materials such as

glassware. In order to produce a smooth surface of polymer layer which can be taken

out easily without any damages, the polymer coated material should be placed on a

Teflon sheet. The grids on the Teflon sheet labelled with the details and weights of

coated material and sample numbers. Pure myristic acid pellets were also prepared as

reference samples.

3.4 Characterization

3.4.1 Fourier Transform Infrared Spectroscopy (FTIR-ATR)

Infrared spectra were used to study the interaction between PMMA and myristic

acids. The infrared spectra of PCMs with coating and without coating were recorded

using PerkinElmer Spectrum Two FTIR Spectrometer. Attenuated Total Reflectance

(ATR) was used for this analysis because it can analyze the composite PCMs with

coating in their natural states without grinding and destroying the coating. Analysis

was conducted in the wavelength range of 4000 to 400 cm-1

with 32 scans.

3.4.2 Differential Scanning Calorimetry (DSC)

Thermal properties of composite PCMs were measured by using Mettler Toledo

TOPEM differential scanning calorimetry (DSC). The analysis of latent heat were

carried out at the temperature of 25-120 ⁰C and 5 ⁰C/min heating rate under a

constant stream of nitrogen gas at the flow rate of 10mL/min. DSC was used to

analyze the melting point and freezing point. A PCM pellet was dissolved in 150 mL

chloroform by stirring with hot plate magnetic stirrer (Model: Stuart SB 162-3) with

41

speed of 4 for 1 hour, then the dried sample was placed in a 40µL crucible. The

weight of the sample was recorded. Then, the crucible was encapsulated with lid.

3.4.3 Leakage test

Few strips of blue litmus paper were stick on a paper. A grid was drawn as shown in

Figure 3.10 below.

Figure 3.10: The set up for leakage test.

The form stable PCM samples with different blending compositions of

PMMA (0%, 20%, 40%, 60%, and 80%) with rubber and PA coatings were placed

on the blue litmus paper. The leakage of PCM can be observed through the colour

change of litmus paper from blue to pink. The leakage test method was modified

from the selection of proper mass percentage of different form stable PCMs by

Huang et al., (2013).

42

Subsequently, samples with different weight percentage of PMMA (0%, 20%,

40%, 60%, and 80%) composition with coating and without coating are tested for 30

thermal cycles, which is 1 hour for 1 thermal cycle at temperature of 65⁰C using

drying oven (Model: Memmert UN 110). After the testing, the leakage area of PCMs

were measured and recorded by using GIMP 2 and Image J software. The dimension

of the test area is 4.6 cm × 6.6 cm.

3.4.4 Tensile Test

The PA, NBR and combination of NBR layered with PA were casted into films of

3.5g – 3.8g using Teflon mold in Figure 3.12. The samples were cut into dumbbell

shape using a dumbbell cutter, shown in Figure 3.11. After that, the samples were

measured the thickness using a digital Vernier calliper (Model: Mitutoyo CD-12‖C).

The thickness were measured at the neck and both ends of the samples, then the

average thickness were calculated from the readings recorded.

Figure 3.11: Specimen for Tensile Test.

Figure 3.12: Teflon mold.

43

Subsequently, the sample was placed on the holder, and tightens before the

tensile test started. Next, the average thickness, width of the neck, and gage length

for the sample were inserted into the software. Once finished, the tensile test was

started until the sample broke. The data such as Young’s modulus, Ultimate Tensile

Strength and Elongation at break were recorded. The settings of the tensile test are:

force is 500N, gage length is 30mm, and width is 26 mm. The model of tensile

machine is Tinius Olsen H10KS-0748 with a load cell of 500N, at a crosshead speed

of 500 mm/min.

44

CHAPTER 4

RESULTS AND DISCUSSIONS

4.1 Characterization of Form Stable PCM

4.1.1 Tensile Test

The phase change material produced in this research was coated with NBR layered

with PA coating. This formulation was chosen as coating material based on its tensile

properties.

NBR coating, PA coating and NBR layered with PA coating are casted into

thin sheet of film with weight average of 3.5-3.8 g, then cut into test samples using a

dumbbell cutter. The tensile test results are summarized in Table 4.1. From the

results, the PA samples display the highest tensile strength, followed by NBR layered

with PA coating (NBR-PA), and NBR coating. NBR shows the highest percentage of

elongation at break, followed by NBR-PA and PA.

The NBR layered with PA coating was selected as coating for the PCM. This

is because it has elasticity to withstand the volume change of PCM inside the core,

and at the same time PA can provide good tensile strength to hold the structure of the

PCM from deforming. These attributes are crucial to prevent the leakage of PCM

when exposed to heat.

45

Table 4.1 Tensile properties of polymer coating film.

Polymer

coating

Young’s modulus

(MPa)

Tensile Strength

(MPa)

Elongation at

break (%)

NBR 9.22x10-2

± 3.94x10-3

2.32 ± 2.88x10-1

1250.22 ± 10.01

PA 130.84 ± 9.88 12.19 ± 1.34 167.86 ± 11.76

NBR-PA 76.10 ± 5.43 8.21 ± 3.14x10-1

193.92 ± 2.88

4.1.2 Leakage Test

Leakage of dip coated PCM after the thermal cycle process can be seen in Figure 4.1.

Leakage of PCM without coating after the thermal cycle process can be seen in

Figure 4.2. The change of colour in litmus paper from blue to red confirms that there

is acid leakage from PCM. This is because of the volume expansion of PCM during

phase change process. The PMMA in the PCM blending acts as a stabilizer to control

the leakage problem. As the weight percentage of the PMMA increases, and at the

same time the weight percentage of myristic acid decreases, the leakage area of the

PCM is decrease for both coated and non-coated samples. The other problem is

during the dipping process, the presence of bubble in the coating solution will cause

bubble to trap on the surface of coating. In addition, the uneven surface of the Teflon

during drying process will also produce coating with uneven thickness. These factors

will be the weak points for leakage to occur. The leaked percentage influences the

latent heat of form stable PCM which determines the thermal storage effect. Thus,

the total leakage percentage is considered as a crucial factor (Huang et al., 2013).

46

Time

(h)

PCM20 PCM40 PCM60 PCM80 PCM100

0

30

Figure 4.1: Leakage of coated PCM after 30 thermal cyclic process.

Time

(h)

PCM20 PCM40 PCM60 PCM80 PCM100

0

30

Figure 4.2: Leakage of PCM without coating after 30 thermal cyclic process.

47

Table 4.2 Leakage area of non-coated PCMs.

PCM 20 40 60 80 100

Duration (hour) Area (cm2)

5 1.952 3.650 6.651 25.680 28.006

10 2.200 4.066 7.614 26.141 28.403

15 2.307 4.066 7.709 26.141 28.403

20 3.070 4.066 7.881 26.141 28.403

25 3.070 4.066 8.772 26.141 28.403

30 3.070 4.066 9.099 26.141 28.403

Leakage area

percentage (%)

10.112 13.393 29.970 86.103 93.554

Table 4.3 Leakage area of coated PCMs.

PCM 20 40 60 80 100

Duration (hour) Area (cm2)

5 0 0 0 0 0

10 0 0 0 0 2.284

15 0 0 0 0 8.141

20 0 0 0 0 9.298

25 0 0 0 0 10.104

30 0 0 0 0 12.351

Leakage area

percentage (%)

0 0 0 0 40.682

As the percentage of PMMA increases and percentage of MA decreases, the

leakage area will also possess a decreasing trend. The presence of PMMA as

stabilizer is crucial to increase the thermal stability of the PCM to prevent leakage to

occur as shown in PCM20, PCM40, PCM60 and PCM80 in Table 4.3.

48

4.1.3 Differential Scanning Calorimetry (DSC)

4.1.3.1 Latent Heat

The result obtained from DSC is to evaluate the latent heat absorbed and released by

myristic acid (PCM) with different PMMA loading. The endothermic peak indicates

the heat absorbed by the PCM while the exothermic peak indicates the heat released

by the PCMs. The peaks were obtained at the melting and freezing temperature of

myristic acid which is around 50-55⁰C. The latent heat of melting of pure myristic

acid with more than 98% purity is 221.04 J/g. Meanwhile, the latent heat of melting

of PCMs coated with NBR and PA with 0 wt%, 20 wt%, 40 wt%, 60wt%, and 80wt%

PMMA loading are 135.79 J/g, 107.56 J/g, 82.95 J/g, 53.21 J/g, and 25.79 J/g. The

latent heat of freezing of pure myristic acid is 224.14 J/g, whereas the latent heat of

freezing of PCMs coated with NBR and PA with 0 wt%, 20 wt%, 40 wt%, 60wt%,

and 80wt% PMMA loading are 134.77 J/g, 102.26 J/g, 82.85 J/g, 54.17 J/g, and

25.51 J/g. The latent heat shows a decreasing trend as the weight percentage of the

PMMA in PCMs increase and the weight percentage of MA decrease, and the lowest

latent heat is obtained from PCM20 with 80wt% PMMA. This is due to the content

of phase change material, which is myristic acid has decreased. The latent heat

released and absorbed by the PCMs during thermal phase change process is tabulated

in Table 4.4.

Table 4.4 Latent Heat Absorbed and Released by PCM.

Samples Weight Percentage of

PMMA in PCM (%)

Amount of Heat

Absorbed

(Endothermic), J/g

Amount of Heat

Released

(Exothermic), J/g

PCM20 80 25.79 25.51

PCM40 60 53.21 54.17

PCM60 40 82.95 82.85

PCM80 20 107.56 102.26

PCM100 0 135.79 134.77

Pure MA Pure MA 221.04 224.14

49

Figure 4.3 and 4.4 indicate the combination of heat absorption peaks and heat

release peaks by PCMs with different weight percentage of myristic acid (MA) and

polymethyl methacrylate (PMMA) blending.

Figure 4.3: DSC graph combination for different weight percentage of PMMA in

PCM of heat absorption peaks.

Figure 4.4: DSC graph combination for different weight percentage of PMMA in

PCM of heat release peaks.

-30

-25

-20

-15

-10

-5

0

25 32.5 40 47.5 55 62.5 70 77.5 85 92.5

mW

Tr (⁰C)

PCM20

PCM40

PCM60

PCM80

PCM100

PURE MA

0

10

20

30

40

50

60

100 87.5 75 62.5 50 37.5 25

mW

Tr (⁰C)

PCM20

PCM40

PCM60

PCM80

PCM100

PURE MA

50

The reduction of latent heat is due to replacement of MA which has high

latent heat with PMMA which has low latent heat. Moreover, the thickness of the

coating layer also influences the heat transfer rate of the PCM. The latent heat will

reduce if the thickness of the coating layer increases. The leakage is due to the phase

change during the melting process. Hence, with addition of PMMA, the melting will

happen but the PCM will remain solid.

The results of DSC from this work are comparable with other results done by

other researchers from their previous works. Table 4.5 summarized the form stable

solid-liquid organic PCMs and some of their thermal properties as comparison to the

current study.

51

Table 4.5 Examples of form stable solid-liquid organic PCMs and some of their thermal properties (Kee et al., 2018)

No. Material and method Pure PCM FSCPCM Findings References

Melting

point (⁰C)

Latent heat of

melting (J/g)

Optimum

PCM mass

percentage

Melting

point

(⁰C)

Latent heat of

melting (J/g)

1 PCM: myristic acid

Porous material:

polymethylmethacrylate

(PMMA)

Method: solution blending of

PMMA and MA, coated with

NBR-PA

50-55 221.04 80wt% 52-56 107.56 - Thermally reliable: After 30

thermal cycling test

- FTIR spectrum shows that the

PCM is well coated with PA

Current

study

2 PCM: stearic acid

Polymeric matrix:

polymethylmethacrylate

Method: dispersion

polymerization through UV

photoinitiated method

59.90 177.80 51.8 wt% 60.4 92.1

(Reduced by

48.20%)

- Thermally and chemically reliable:

After 500 thermal cycling tests,

the reduction of latent heat is

1.2% and no much changes of

shape and frequency value of all

FTIR peaks

- The core/shell structure of

microcapsules was formed well as

shown in scanning electron

microscope (SEM) image which

improve the thermal stability

Wang et al.,

2011

52

3 PCM: caprylic acid

Polymeric matrices:

ureaformaldehyde resin

Method: microencapsulation via

simple coacervation method

19.31 158.44 59 wt% 13.90 93.9

(Reduced by

40.74%)

- SEM images showed that

microcapsules have spherical

structure and well encapsulated

- No leakage test

Konuklu et

al., 2014

4 PCM: composite paraffin

Porous material: calcined

diatomite

Method: fusion adsorption

method

29.94 145.90 61% 33.04 89.5

(Reduced by

38.66%)

- Thermally reliable: After 200

thermal cycling tests, the

reduction in latent heat is less than

5%

- Composite paraffin was

impregnated and confined into the

pores of calcine diatomite because

diatomite has high porosity, high

permeability and large specific

surface area

Sun et al.,

2013

5 PCM: PEG

Porous material: activated

carbon

Method: direct blending and an

impregnating method.

N/A N/A 70% 45–65 81–86 - Thermal stability is assessed by

TGA and no decomposition was

found below 250 ⁰C

- It is thermally stable because

activated carbon has extensive

pore structures with high specific

surface area and absorption

capacity for PEG

Feng et al.,

2011

53

6 PCM: Polyethylene glycol

(PEG)

Porous material: diatomite

Method: vacuum impregnation

method

33.32 143.16 50 wt% 27.70 87.09

(Reduced by

39.17%)

- Thermally reliable: After 1000

thermal cycling test, the reduction

of latent heat of melting is 1.1%

- PEG was impregnated and

confined into the pores of

diatomite because diatomite has

high porosity and absorptive

Karaman et

al., 2011

7 PCM: PEG

Porous material: expanded

graphite

Method: direct blending and an

impregnating method

N/A N/A 90 wt% 60–65 150–160 - Expanded graphite with

macroporous structures can

effectively stabilize the melted

PEG through both the capillary

force of the pores and the

hydrogen bonding resulting from

the surface functional groups

Wang et al.,

2012

54

4.1.4 Fourier Transform Infrared Spectroscopy (FTIR-ATR)

FTIR analysis was conducted on samples with different weight percentages of

PMMA (80 wt%, 60 wt%, 40wt%, 20wt%, and 0 wt%) with and without NBR-PA

coating in order to determine the functional group present. Figure 4.5 shows the IR

spectrum of pure myristic acid as reference.

Figure 4.5: FTIR spectrum of pure myristic acid.

PA coating is the outer coating of the PCM. PA molecules have high

presence of C-O bonds. Therefore, majority of the vibration peaks are subjected to

the C-O bonds. The stretching of C-H, C=O, deformation of CH3 and CH2 single

bond stretching of C-O-C and single bond deformation of C-O-C occurs at a range of

3050-2990 cm-1

, 1730 cm-1

, 1450-1395 cm-1

, 1260-1040 cm-1

and 960-880 cm-1

respectively (Sites.google.com, 2015). Furthermore, the bending around 3437 cm-1

indicates OH group stretching due to physisorbed moisture according to Duan et al.,

(2008). Besides, Gayosso et al., (2015) also states that the stretching of C=O occurs

around 1730 cm-1

and 1250 cm-1

and the stretching occurs around 3000-2800 cm-1

indicates the vibration for CH3 and CH2. Abdelrazek et al., (2016), Rajendran and

Uma, (2000) and Pan et al., (2012) have reported that C=O stretching, CH2 bending,

CH2 stretching, C-O-C stretching, C-O stretching and C-C stretching for PA occur at

55

1726 cm-1

, 1473 cm-1

, 2942-2862 cm-1

, 1233-1042 cm-1

, 1160 cm-1

, and 1290 cm-1

respectively. On the other hand, the FTIR spectrum for myristic acid have C=O

stretching at 1701 cm-1

, asymmetrical stretching of -CH2 at 2916 cm-1

and 2848 cm-1

,

OH stretching peaks at 686 cm-1

, 721 cm-1

, and 939 cm-1

, C-H bending at 1286 cm-1

and C-C bending at 1261 cm-1

(Sharma et al., 2009; Trivedi et al., 2015). Table 4.6

and Table 4.7 shows the absorption frequencies obtained for PA and MA with

functional groups corresponding to the peaks respectively.

Table 4.6 Absorption Frequency Obtained for PA.

PA Functional Groups Corresponding peaks References

OH group stretching 3447 cm-1

(Duan et al., 2008)

The stretching of C-H 2999-2953cm-1

(Sites.google.com, 2015)

The stretching of C=O 1735 cm-1

(Gayosso et al., 2015)

Deformation of CH3 and

CH2

1463 cm-1

(Abdelrazek et al., 2016)

Single bond stretching of

C-O-C

1147 cm-1

(Rajendran and Uma,

2000)

C-C stretching vibration 989 cm-1

and 749 cm-1

(Ramesh et al., 2007;

Gunasekaran, 2016)

Single bond deformation

of C-O-C

960-880 cm-1

(Pan et al., 2012)

C-H deformation 483 cm-1

(Uthayakumar et al., 2013)

56

Table 4.7 Absorption Frequency Obtained for Myristic Acid.

Myristic Acid Functional

Groups

Corresponding peaks References

C=O stretching 1697 cm-1

(Sharma et al., 2009;

Trivedi et al., 2015) Asymmetrical stretching

of –CH2

2917 cm-1

OH stretching peaks 3300-2500 cm-1

, 939 and

720 cm-1

C-H bending 1286 cm-1

C-C bending 1261 cm-1

Figure 4.6 shows the IR spectrum of PCM100 (0 wt% PMMA), PCM80 (20

wt% PMMA), PCM60 (40 wt% PMMA), PCM40 (60 wt% PMMA), and PCM20

(80 wt% PMMA) without NBR-PA coating, and Figure 4.7 shows the IR spectrum of

PCM100 (0 wt% PMMA), PCM80 (20 wt% PMMA), PCM60 (40 wt% PMMA),

PCM40 (60 wt% PMMA), and PCM20 (80 wt% PMMA) with NBR-PA coating.

The spectrum of PCM pellets show peaks at 2962-2956 cm-1

, 1733-1728 cm-1

, 1464-

1452 cm-1

, 1152-1146 cm-1

, 949-942 cm-1

, 994-988 cm-1

, 759-749 cm-1

, and 489-483

cm-1

which are assigned to CH stretching, C=O stretching, CH3 stretching, single

bond stretching of C-O-C, single bond deformation of C-O-C, C-C stretching

vibration, and C-H deformation respectively. The FTIR spectrum shows that the

PCM is well coated with PA because only PA coating peak was detected after

coating. The frequency obtained for each spectrums of each samples are tabulated in

Table 4.8.

57

Figure 4.6: Combination of FTIR spectrum of PCMs without coating.

58

Figure 4.7: Combination of FTIR spectrum of PCMs with coating.

59

Table 4.8 Absorption Frequency Regions and Functional Groups for coated

PCMs.

Absorption

Frequency

Range (cm-1

)

Absorption Frequency (cm-1

)

Functional Groups PCM

20

PCM

40

PCM

60

PCM

80

PCM

100

2962-2956

2958 2961 2962 2961 2956 Stretching of C-H

1733-1728

1728 1729 1732 1733 1728 Stretching of C=O

1464-1452

1452 1464 1454 1455 1451 Deformation of CH3

and CH2

1152-1146

1146 1147 1151 1152 1146 Single bond stretching

of C-O-C

949-942

942 944 948 949 940 Single bond

deformation of C-O-C

994-988,

759-749

990,

756

988,

753

994,

759

991,

760

989,

757

C-C stretching

vibration

489-483

484 484 486 489 483 C-H deformation

60

CHAPTER 5

CONCLUSION AND RECOMMENDATIONS

5.1 Conclusion

The phase change material (PCM) used in this research is myristic acid since the

melting point (55⁰C) of this fatty acid is suitable and low to be used as latent heat

transfer material in solar water heaters. The major drawback of using myristic acid in

solar water heater is, the acid tend to corrode the wall of the solar water heater during

the phase change process. Therefore, the method of blending myristic acid with

PMMA and coat with nitrile butadiene rubber (NBR) and polyacrylic (PA) was

carried out. The tensile properties for the combination of NBR and PA coating is the

most suitable due to its sufficient elasticity contributed by the NBR, and good tensile

strength contributed by the PA to withstand volume expansion of PCM during phase

transition process. Only the amount of leakage could be reduced by just coating with

NBR and PA but the leakage still persist. In order to overcome this drawback, the

method of blending the PCM with different weight percentage of PMMA was

studied in this research.

The leakage results show that the leakage percentage decrease and eliminated

when the weight percentage of PMMA increase while the weight percentage of MA

decrease. Moreover, the latent heat of melting and freezing of form stable PCM80

with 20 wt% PMMA is 107.56 J/g and 102.26 J/g respectively. This concludes that

the form stable PCM80 has great thermal stability, which withstand 30 thermal

cycles without leakage. The FTIR of the coated PCMs show that the coating is

completely covered the PCMs.

61

5.2 Recommendation

In this study, form stable PCM without leakage is successfully produced, but the

latent heat of melting and freezing of the form stable PCM is quite low, which is

around 107.56 J/g and 102.26 J/g while pure myristic acid can absorb and release

heat up to 221.04 J/g and 224.14 J/g. This drawback can be corrected by choosing an

appropriate stabilizer as blending composite. The stabilizer should have good thermal

conductivity, good thermal stability, good latent heat and compatible with myristic

acid.

The next recommendation is to produce a thinner coat, which is more

compact and strong, as the thickness of the coat also influences the latent heat of

PCMs. This can be done by incorporating the filler such as reduced graphene oxide

to strengthen the properties of the coating.

62

REFERENCES

Abdelrazek, E., Hezma, A., El-khodary, A. and Elzayat, A. (2016). Spectroscopic

studies and thermal properties of PCL/PMMA biopolymer blend. Egyptian

Journal of Basic and Applied Sciences, 3(1), pp. 10-15.

Agarwal, A. and Sarviya, R. (2016). An experimental investigation of shell and tube

latent heat storage for solar dryer using paraffin wax as heat storage material.

Engineering Science and Technology, an International Journal, 19(1), pp. 619-

631.

Alkan, C., Günther, E., Hiebler, S. and Himpel, M. (2012). Complexing blends of

polyacrylic acid-polyethylene glycol and poly (ethylene-co-acrylic acid)-

polyethylene glycol as shape stabilized phase change materials. Energy

Conversion and Management, 64, pp. 364-370.

Alkan, C., Sari, A., Karaipekli, A. and Uzun, O. (2008). Preparation, characterization,

and thermal properties of microencapsulated phase change material for thermal

energy storage. Solar Energy Materials and Solar Cells, 93(1), pp. 143-147.

Alkan, C., Kolemen, U. and Uzun, O. (2006). Eudragit S (methyl

methacrylate methacrylic acid copolymer)/fatty acid blends as form-stable phase

change material for latent heat thermal energy storage. Journal of Applied

polymer Science, 101(3), pp. 1402-1406.

Al-Shannaq, R., Kurdi, J., Al-Muhtaseb, S. and Farid, M. (2016). Innovative method

of metal coating of microcapsules containing phase change materials. Solar

Energy, 129, pp. 54-64.

63

Alternative Energy Tutorials. (2014). Solar radiation and the Sun as an Energy

Resource. [Online] Available at: http://www.alternative-

energytutorials.com/energy-articles/solar-radiation.html [Accessed 14th

December 2017].

Asyraf, W., Vasu, A., Hagos, F., Noor, M. and Mamat, R. (2016). Transient

modelling of heat loading of phase change material for energy storage. MATEC

Web of Conferences, 90, pp. 01078.

Aziz, F. and Ismail, A. (2015). Spray coating methods for polymer solar cells

fabrication: A review. Materials Science in Semiconductor Processing, 39, pp.

416-425.

Badenhorst, H. (2018). A review of the application of carbon materials in solar

thermal energy storage. [Online] Solar Energy. Available at:

https://doi.org/10.1016/j.solener.2018.01.062 [Accessed 17th March 2018].

Barriga, J., Ruiz-de-Gopegui, U., Goikoetxea, J., Coto, B. and Cachafeiro, H. (2014).

Selective Coatings for New Concepts of Parabolic Trough Collectors. Energy

Procedia, 49, pp. 30-39.

Bentz, D. and Turpin, R. (2007). Potential applications of phase change materials in

concrete technology. Cement and Concrete Composites, 29(7), pp. 527-532.

Ciolkosz, D. (2017). Solar Energy. [Online] extension.psu.edu. Available at:

http://extension.psu.edu/natural-resources/energy/solar-energy [Accessed 19th

August 2017].

Clark, D. (2001). Peroxides and peroxide-forming compounds. Chemical Health and

Safety, 8(5), pp. 12-22.

Cota, S., Vasconcelos, V., Senne Jr., M., Carvalho, L., Rezende, D. and Cörrea, R.

(2007).Changes in mechanical properties due to gamma irradiation of high-

64

density polyethylene (HDPE). Brazilian Journal of Chemical Engineering,

24(2).

Cruz. R., Vieira, M. and Silva, C. (2009). Effect of cold chain temperature abuses on

the quality of frozen watercress (Nasturtium officinale R. Br.). Journal of Food

Engineering, 94(l), pp. 90-97.

Cui, Y. and Riffat, S. (2011). Review on Phase Change Materials for Building

Applications. Applied Mechanics and Materials, 71-78, pp. 1958-1962.

Diaz, P. (2016). Analysis and Comparison of different types of Thermal Energy

Storage Systems: A Review. Journal of Advances in Mechanical Engineering

and Science, 2(1), pp. 33-46.

Diekmann, D. (2006). Latent Heat storage in Concrete. 1st ed. [ebook] Germany:

University of Kaiserslautern. Available at: http://www.eurosolar.de/ [Accessed

25th November 2017].

Duan, G., Zhang, C., Li, A., Yang, X., Lu, L. and Wang, X. (2008). Preparation and

Characterization of Mesoporous Zirconia Made by Using a Poly (methyl

methacrylate) Template. Nanoscale Research Letters, 3(3), pp. 118-122.

Eames, P., Loveday, D., Haines, V. and Romanos, P. (2014). The Future Role of

Thermal Energy Storage in the UK Energy System: An assessment of the

Technical Feasibility and Factors Influencing Adoption. [Online] Ukerc.ac.uk.

Available at: http://www.ukerc.ac.uk/asset/82664E2B-6533-

4019BF5140CEB7B9894D [Accessed 2nd August 2017].

Energy Saving Trust. (2015). Solar water heating. [Online] Available at:

http://www.energysavingtrust.org.uk/renewable-energy/heat/solar-water-heating

[Accessed 2nd August 2017].

Energy Storage: Preparation and Performance Analysis. Materials, 6(10), pp. 4758-

4775.

65

Extension.purdue.edu. (2017). AE-89. [Online] Available at:

https://www.extension.purdue.edu/extmedia/ae/ae-89.html [Accessed 10th

September 2017].

Farid. M., Khudhair, A., Razack, S. and Al-Hallaj, S. (2004). A review on phase

change energy storage: materials and applications. Energy Conversion and

Management, 45(9-10), pp. 1597-1615.

Fauzi, H., Metselaar, H., Mahlia, T. and Silakhori, M. (2014). Thermal Reliability of

Myristic Acid/Palmitic Acid/Sodium Laurate Eutectic Mixture: A Feasibility

Study of Accelerated Aging for Thermal Energy Storage Application. Energy

Procedia, 61, pp.49-54.

Feldman, D., Banu, D. and Hawes, D. (1995). Low chain esters of stearic acid as

phase change materials for thermal energy storage in buildings. Solar Energy

Materials and Solar Cells, 36(3), pp. 311-322.

Flitney, B. (2009). Confomal coating coats complex products. Sealing Technology,

2009(2), p. 3.

Fortuniak, W., Slomkowski, S., Chojnowski, J., Kurjata, J., Tracz, A. and Mizerska,

U. (2012). Synthesis of a paraffin phase change material microencapsulated in a

siloxane polymer. Colloid and Polymer Science, 291 (3), pp. 725-733.

Gayosso, C., Canseco, M., Estrada, R., Alquisira, J., Hinojosa, J. and Castaño, V.

(2015). Preparation and microstructure of cobalt (III) poly (acrylate) hybrid

materials. International Journal of Basic and Applied Sciences, 4 (3), pp. 255-

263.

Gil, A., Oro, E., Mira, L., Peiro, G., Ruiz, Å., Salmeron, J. and Cabeza, L. (2014).

Experimental analysis of hydroquinone used as phase change material (PCM) to

be applied in solar cooling refrigeration. International Journal of Refrigeration,

39, pp. 95-103.

66

Gin, B. and Farid, M. (2010). The use of PCM panels to improve storage condition

of frozen food. Journal of Food Engineering, 100(2), pp. 372-376.

Giro-Paloma, J., Martinez, M., Cabeza, L. and Fernandez, A. (2016). Types, methods,

techniques, and applications for microencapsulated phase change materials

(MPCM): A review. Renewable and Sustainable Energy Reviews, 53, pp. 1059-

1075.

Gupta, N. and Tiwari, G. (2016). Review of passive heating/cooling systems of

buildings. Energy Science & Engineering, 4(5), pp. 305-333.

Hasan, A. and Sayigh, A. (2004). Some fatty acids as phase-change thermal energy

storage materials. Renewable Energy, 4(1), pp. 69-76.

Hasan, A., Hejase, H., Abdelbaqi, S., Assi, A. and Hamdan, M. (2016). Comparative

Effectiveness of Different Phase Change Materials to Improve Cooling

Performance of Heat Sinks for Electronic Devices. Applied Sciences, 6(9),

p.226.

Hauer, A. (2013). Thermal Energy Storage. [Online] Available at:

https://www.irena.org/DocumentDownloads/Publications/IRENA-

ETSAP%20Tech%20Brief%20E17%20Thermal%20Energy%20Storage.pdf

[Accessed 5th August 2017].

Huang, J., Lu, S., Kong, X., Liu, S. and Li, Y. (2013). Form-Stable Phase Change

Materials Based on Eutectic Mixture of Tetradecanol and Fatty Acids for

Building Energy Storage: Preparation and Performance Analysis. Materials,

6(10), pp. 4758-4775.

Inc., T. (2017). Techni-Tool: Industrial Supplies, Electronic Production, MRO &

Tools. [Online] Techni-tool.com. Available at: http://www.techni-tool.com

[Accessed 16th January 2018].

67

Iten, M., and Liu, S. (2014). A work procedure of utilising PCMs as thermal storage

systems based on air-TES systems. Energy Conversion and Management, 77, pp.

608-627.

Jamekhorshid, A., Sadrameli, S. and Farid, M. (2014). A review of

microencapsulation methods of phase change materials (PCMs) as a thermal

energy storage (TES) medium. Renewable and Sustainable Energy Reviews, 31,

pp. 531-542.

Kabir, E., Kumar, P., Kumar, S., Adelodun, A. and Kim, K. (2017). Solar energy:

Potential and future prospects. Renewable and Sustainable Energy Reviews, 82,

pp. 894-900.

Kant, K., Shukla, A. and Sharma, A. (2016). Ternary mixture of fatty acids as phase

change materials for thermal energy storage applications. Energy Reports, 2, pp.

274-279.

Kapsalis, V. and Karamanis, D. (2016). Solar thermal energy storage and heat pumps

with phase change materials. Applied Thermal Engineering, 99, pp. 1212-1224.

Kee, S. Y., Munusamy, Y., Ong, K. S. and Lai, K. C. (2017). Effect of Preparation

Methods on the Tensile, Morphology and Solar Energy Conversion Efficiency of

RGO/PMMA Nanocomposites. Polymers, 9(6), pp. 230

Kee, S. Y., Munusamy, Y., Ong, K. S., Metselaar, H., Chee, S. Y. and Lai, K. C.

(2017). Thermal Performance Study of Composite Phase Change Material with

Polyacrylic and Conformal Coating. Materials, 10(8), pp. 873.

Kee, S. Y., Munusamy, Y. and Ong, K. S. (2018). Review of solar water heaters

incorporating solid-liquid organic phase change materials as thermal storage.

Applied Thermal Engineering, 131, pp. 455–471

Kenfack, F. and Bauer, M. (2014). Innovative Phase Change Material (PCM) for

Heat Storage for Industrial Applications. Energy Procedia, 46, pp. 310-316.

68

Khan, M., Al-Mamun, M., Sikdar, S., Halder, P. and Hasan, M. (2015). Design,

Fabrication, and Efficiency Study of a Novel Solar Thermal Water Heating

System: Towards Sustainable Development. [Online] Hindawi.com. Available at:

https://www.hindawi.com/journals/ijp/2016/9698328/ [Accessed 10th November

2018].

Khan, M., Saidur, R., Al-Sulaimana, F. (2017). A review for phase change materials

(PCMs) in solar absorption refrigeration systems. Renewable and Sustainable

Energy Reviews, 76, pp. 105-137.

Khudhair, A. and Farid, M. (2004). A review on energy conservation in building

applications with thermal storage by latent heat using phase change materials.

Energy Conversion and Management, 45(2), pp. 263-275.

Koleske, J. (2012). Paint and coating testing manual. 1st ed. West Conshohocken,

PA: ASTM International.

Kong, X., Zhong, Y., Rong, X., Min, C. and Qi, C. (2016). Building Energy Storage

Panel Based on Paraffin/Expanded Perlite: Preparation and

Thermal Performance Study. Materials, 9(2), p. 70.

Kuboth, S., König-Haagen, A. and Brüggemann, D. (2017). Numerical Analysis of

Shell-and-Tube Type Latent Thermal Energy Storage Performance with

Different Arrangements of Circular Fins. Energies, 10(3), p. 274.

Kumar, M., Arun, S., Upadhyaya, P. and Pugazhenthi, G. (2015). Properties of

PMMA/clay nanocomposites prepared using various compatibilizers.

International Journal of Mechanical and Materials Engineering, 10(7), pp. 1-9.

Kumar, V. (2014). Development of a paraffin wax based solar thermal energy

storage system for water and space heating applications. International Journal of

Emerging Trends in Engineering and Development, [Online] 5(4), pp. 16-25.

69

Available at: http://www.rspublication.com/ijeted/ijeted_index.htm [Accessed

12th December 2017].

Li, H., Chen, H., Li, X. and Sanjayan, J. (2014). Development of thermal energy

storage composites and prevention of PCM leakage. Applied Energy, 135, pp.

225-233.

Lim, J. (2013). Underground Thermal Energy Storage. [Online] Available at:

http://large.stanford.edu/courses/2013/ph240/lim1/ [Accessed 30th November

2017].

Madessa, H. (2014). A Review of the Performance of Buildings Integrated with

Phase Change Material: Opportunities for Application in Cold Climate. Energy

Procedia, 62, pp. 318-328.

Marken, C. (2005). Get Started with Solar Water Heating | Home Power Magazine.

[Online] Homepower.com. Available at:

https://www.homepower.com/articles/solar-water-heating/basics/get-started-

solarwater-heating [Accessed 9th January 2018].

Materials (PCM), T. (2016). Technology innovation for reefer trucks and last mile

distribution using Phase Change Materials (PCM). [Online]

Pcmpluss.blogspot.my. Available at:

http://pcmpluss.blogspot.my/2016/03/'technology-innovation-for-

reefertrucks.html [Accessed 18th October 2017].

Mathur, A., Kasetty, R., Oxley, J., Mendez, J. and Nithyanandam, K. (2013).

Using encapsulated phase change salts for concentrated solar power plant .

Energy Procedia, 49, 908–915.

Mehling, H. and Cabeza, L. (2008). SoIid-liquid phase change materials. lst ed.

[ebook] Springer, pp. 1-46. Available at:

http://www.springer.com/cda/content/document/cda_downloaddocument/978340

70

685562-cl.pdf?SGWlD=0-0-45-562404-p173821439 [Accessed 16th August

2017].

Memon, S. (2014). Phase change materials integrated in building walls: A state of

the art review. Renewable and Sustainable Energy Reviews, 31, pp.870-906.

Mochane, M. and Luyt, A. (2015). The effect of expanded graphite on the thermal

stability, latent heat, and flammability properties of EVA/wax phase

change blends. Polymer Engineering & Science, 55(6), pp. 1255-1262.

Mohtasham, J. (2015). Review Article-Renewable Energies. Energy Procedia, 74, pp.

1289-1297

Moore, J. (2015). Solar Energy. [Online] Hawaiiansustainability.org. Available

at: http://www.hawaiiansustainability.org/solarEnergy.php [Accessed 14th

January 2018].

Murali, G., Mayilsamy, K. and Ali, B. (2015). A Review of Latent Heat Thermal

Energy Storage Systems. Applied Mechanics and Materials, 787, pp. 37-42.

Nayak, A., Gowtham, M., Vinod, R. and Ramkumar, G. (2011). Analysis of PCM

Material in Thermal Energy Storage System. International Journal of

Environmental Science and Development, pp. 437-441.

Nomura, T., Zhu, Y., Sheng, N., Saito, G. and Akiyama, T. (2015).

Microencapsulation of Metal-based Phase Change Material for High-temperature

Thermal Energy Storage. Scientific Reports, 5, pp. 9117.

Nosrati, R. and Olad, A. (2015). The effect of TiO2/aluminosilicate nanocomposite

additives on the mechanical and thermal properties of polyacrylic coatings.

Applied Surface Science, 357, pp. 376-384.

Ogueke, N., Anyanwu, E. and Ekechukwu, O. (2009). A review of solar water

heating systems. [Online] aip.scitation.org. Available at:

71

http://aip.scitation.org/doi/full/10.1063/1.3 167285 [Accessed 15th September

2017].

Oro, E., Gil, A., Miro, L., Peiro, G., Alvarez, S. and Cabeza, L. (2012). Thermal

Energy Storage Implementation Using Phase Change Materials for Solar Cooling

and Refrigeration Applications. Energy Procedia, 30, pp. 947-956.

Pan, L., Pei, X., He, R., Wan, Q. and Wang, J. (2012). Multiwall carbon

nanotubes/polycaprolactone composites for bone tissue engineering application.

Colloids and Surfaces B: Biointerfaces, 93, pp. 226- 234.

Pawar, S. (2015). HIGH TEMPERATURE THERMAL ENERGY STORAGE

SYSTEM APPLICATIONS. INTERNATIONAL JOURNAL OF INNOVATIONS

IN ENGINEERING RESEARCH AND TECHNOLOGY [IJIERT], 2(6), pp. 1-7.

PCM Price challenge. (2009). 1st ed. [ebook] hubspot, pp. 1-7. Available at:

https://cdn2.hubspot.net/hub/55819/file-30934935-

pdf/.../pcm_price_challenge.pdf [Accessed 14th September 2017].

Phimolsiripol, Y., Siripatrawan, U., Tulyathan, V. and Cleland, D. (2008). Effects

of freezing and temperature fluctuations during frozen storage on frozen dough

and bread quality. Journal of Food Engineering, 84(1), pp. 48-56.

Pielichowska, K. and Pielichowski, K. (2014). Phase change materials for thermal

energy storage. Progress in Materials Science, 65, pp. 67-123.

Pielichowski, K. and Flejtuch, K. (2003). Differential Scanning Calorimetry Study of

Blends of Poly (ethylene glycol) with Selected Fatty Acids. Macromolecular

Materials and Engineering, 288(3), pp. 259-264.

Pons, O., Aguado, A., Fernåndez, A., Cabeza, L. and Chimenos, J. (2014). Review of

the use of phase change materials (PCMs) in buildings with reinforced concrete

structures. Materiales de Construccion, 64(315), pp. e031.

72

PureTemp. (2017). Frequently asked questions about phase change materials.

[Online] puretemp.com. Available at:

http://www.puretemp.com/stories/understanding-pcms. [Accessed 8th August

2017].

Rajendran, S. and Uma, T. (2000). Conductivity studies on PVC/PMMA polymer

blend electrolyte. Materials Letters, 44(3-4), pp. 242-247.

Rathod, M. and Banerjee, J. (2013). Thermal stability of phase change materials used

in latent heat energy storage systems: A review. Renewable and Sustainable

Energy Reviews, 18, pp. 246-258.

Robaidi, A. (2013). Development of Novel Polymer Phase Change Material for Heat

Storage Application. International Journal of Materials Science and Applications,

2(6), pp. 168.

Rozanna, D., Chuah, T., Salmiah, A., Choong, T. and Sa'ari, M. (2005). Fatty Acids

as Phase Change Materials (PCMs) for Thermal Energy Storage: A Review.

International Journal of Green Energy, I (4), pp. 495-513.

S. Wahile, G., Suple, Y. and Dongre, S. (2015). Latent Heat Storage by Using

Different Phase Change Materials for Solar Water Heating: A Review.

International Journal of Computer Applications, [Online] pp. 25-28. Available at:

http://research.ijcaonline.org/icquest2015/number6/icquest2810.pdf [Accessed

15th October 2017].

Sarbu, I. and Sebarchievici, C. (2018). A Comprehensive Review of Thermal Energy

Storage. Sustainability, 10(1), pp. 191.

Sari, A. and Karaipekli, A. (2007). Thermal conductivity and latent heat thermal

energy storage characteristics of paraffin/expanded graphite composite as phase

change material. Applied Thermal Engineering, 27(8–9), pp. 1271-1277.

73

Sari, A. and Kaygusuz, K. (2001). Thermal performance of myristic acid as a phase

change material for energy storage application. Renewable Energy, 24(2), pp.

303-317.

Sari, A. and Kaygusuz, K. (2002). Thermal performance of palmitic acid as a phase

change energy storage material. Energy Conversion and Management, 43(6), pp.

863-876.

Sari, A., Alkan, C., Karaipekli, A. and Uzun, O. (2009). Microencapsulated n-

octacosane as phase change material for thermal energy storage. Solar Energy,

83(10), pp. 1757-1763.

Sari. A. and Kaygusuz, K. (2003). Some fatty acids used for latent heat storage:

thermal stability and corrosion of metals with respect to thermal cycling.

Renewable Energy, 28(6), pp. 939-948.

Sari. A., Alkan, C. and Karaipekli, A. (2010). Preparation, characterization and

thermal properties of PMMA/n-heptadecane microcapsules as novel solid—

liquid microPCM for thermal energy storage. Applied Energy, 87(5), pp. 1529-

1534.

Serale, G., Baronetto, S., Goia, F. and Perino, M. (2014). Characterization and

Energy Performance of a Slurry PCM-based Solar Thermal Collector: A

Numerical Analysis. Energy Procedia, 48, pp. 223-232.

Shahare, P., Pawar, D. and Karmarkar, A. (2017). Review of Application of Phase

Changing Materials (PCMs) In Solar Water Heater and Proposed Work with

Scope & Limitation. International Journal of Innovative Research in Science,

Engineering and Technology, [Online] 6(1), pp. 561-568. Available at:

https://www.ijirset.com/upload/2017/icrtes/mech/26_Review_of_application_of_

Phase_changing_materials(PCMs)_in_Solar_Water_Heater_and_proposed_work

_with(GU).pdf. [Accessed 15th October 2017].

74

Sharma, A. and Chen, C. (2009). Solar Water Heating System with Phase Change

Materials. International Review of Chemical Engineering, [Online] 1(4), pp. 297-

305. Available at:

https://www.researchgate.net/publication/265111061_Solar_Water_Heating_Syst

em_with_Phase_Change Materials. [Accessed 15th October 2017].

Sharma, A. and Kar, S. (2015). Energy Sustainability Through Green Energy. 1st ed.

New Delhi: Springer, pp. 249-250.

Sharma, A., Chen, C. and Vu Lan, N. (2009). Solar-energy drying systems: A review.

Renewable and Sustainable Energy Reviews, 13(6-7), pp. 1185-1210.

Sharma, A., Tyagi, V., Chen, C. and Buddhi, D. (2009). Review on thermal energy

storage with phase change materials and applications. Renewable and

Sustainable Energy Reviews, 13(2), pp. 318-345.

Sharma, A., Kitano, H. and Sagara (2004). Phase Change Materials for Low

Temperature Solar Thermal Applications. [Online] 29, pp.31-64. Available at:

https://www.researchgate.net/publication/241091651_Phase_Change_Materials_

for_Low_Temperature_Solar_Thermal_Applications [Accessed 15th October

2017].

Shukla, A., Buddhi, D. and Sawhney, R. (2009). Solar water heaters with phase

change material thermal energy storage medium: A review. Renewable and

Sustainable Energy Reviews, 13(8), pp. 2119-2125.

Silakhori, M., Fauzi, H., Mahmoudian, M., Metselaar, H., Mahlia, T. and Khanlou,

H.(2015). Preparation and thermal properties of form-stable phase change

materials composed of palmitic acid/polypyrrole/graphene nanoplatelets. Energy

and Buildings, 99, pp. 189-195.

Sites.google.com. (2015). Polymethy1 Methacrylate (PMMA) - ISU MatE453/MSE

553 – Lab 3 – FTIR. [Online] Available at:

75

https://sites.googIe.com/site/isumate4531ab3group8/data/polymethylmethacrylat

e-pmma [Accessed 26th January 2018].

Soares N., Costa, J., Gaspar, A. and Santos, P. (2013). Review of passive PCM latent

heat thermal energy storage systems towards buildings' energy efficiency. Energy

and Buildings, 59, pp. 82-103.

Teke, R., Gangde, C. and Kalbande, S. (2016). Review on Phase Change Materials in

Different Solar Gadgets. International Journal of Engineering Trends and

Technology, 37(4), pp. 197-201.

Thakral, S., Thakral, N. and Majumdar, D. (2012). Eudragit: a technology evaluation.

PubMed - NCBI. [Online] Ncbi.nlm.nih.gov. Available at:

https://www.ncbi.nlm.nih.gov/pubmed/23102011 [Accessed 18th February 2018].

Uthayakumar, S., Chandhuru, J., Inbasekaran, S., Sivasubramanian, A. Biomedical

Optical spectroscopy techniques for Diagnosis of Human saliva sample. Asian

Journal of Biomedical and Pharmaceutical Sciences 03 (24), pp. 12-21.

Vadhera, J., Sura, A., Nandan, G. and Dwivedi, G. (2018). Study of Phase Change

materials and its domestic application. Materialstoday: Proceedings, 5(2), pp.

3411-3417.

Wang, L. and Meng, D. (2010). Fatty acid eutectic/polymethyl methacrylate

composite as form-stable phase change material for thermal energy storage.

Applied Energy, 87(8), pp. 2660-2665.

Wang, R., Qiu, F., Zhang, H. and Yang, Y. (2003). Interactions between brush-

coated clay sheets in a polymer matrix. [Online] AIP. Available at:

http://aip.scitation.org/doi/10.1063/1.1568339 [Accessed 30th November 2017].

Wang, Y., Xia, T., Feng, H., and Zhang, H. (2011). Stearic acid

/polymethylmethacrylate composite as form-stable phase change materials for

latent heat thermal energy storage. Renewab1e Energy, 36(6), pp. 1814-1820.

76

Wani, C. and Loharkar, P. (2017). A Review of Phase Change Materials as an

Alternative for Solar Thermal Energy Storage. Materialstoday: Proceedings,

4(9), pp. 10264-10267.

Wei Chiu, J., Martin, D. and Setterwall, P. (2010). A Review of Thermal Energy

Storage Systems with Salt Hydrate Phase Change Material for Comfort.

11th International Conference on Thermal Energy Storage, [Online] pp. 1-7.

Available at: https://intraweb.stockton.edu/eyos/energy_studies/content/docs/effs

tock09/Session_8_1%20Sustainable_Comfort_Cooling/61.pdf. [Accessed 30th

November 2017].

Whiffen, T. and Riffat, S. (2012). A review of PCM technology for thermal energy

storage in the built environment: Part I. International Journal of Low-Carbon

Technologies, 8(3), pp. 147-158.

Yanniotis, S., Dimakou, C., Soumbasi, E., Mandala, I., 2008. Effect of temperature

fluctuation in a freezer on the drip loss of meat. In: ICEF10-International

Congress of Engineering and Food — Poster Presentation. Chile.

Yanshan, L., Shujun, W., Hongyan, L., Fanbin, M., Huanqing, M. and Wangang, Z.

(2014). Preparation and characterization of melamine/formaldehyde/polyethylene

glycol crosslinking copolymers as solid—solid phase change materials.

Solar Energy Materials and Solar Cells, 127, pp. 92-97.

Zalba, B., Marin, J., Cabeza. L. and Mehling. H. (2003). Review on thermal energy

storage with phase change: materials, heat transfer analysis and applications.

Applied Thermal Engineering, 23(3), pp. 251-283.

Zhang, G. et al. (2014) Encapsulation of copper-based phase change materials for

high temperature thermal energy storage. Solar Energy Materials and Solar

Cells, 128, pp. 131–137.

77

Zhang, H., Baeyens, J., Cáceres, G., Degrève, J. and Lv, Y. (2016). Thermal energy

storage: Recent developments and practical aspects. Progress in Energy and

Combustion Science, 53, pp. 1-40.

Zhang, Y., Du, K., Medina, M. and He, J. (2014). An experimental method

for validating transient heat transfer mathematical models used for phase change

materials (PCMs) calculations. Phase Transitions, 87(6), pp. 541-558.

Zhou, B. and Pang, M. (2015). Experimental investigations on the performance of a

collector–storage wall system using phase change materials. Energy Conversion

and Management, 105, pp. 178-188.

Zhou, D., Zhao, C. and Tian, Y. (2012). Review on thermal energy storage with

phase change materials (PCMs) in building applications. Applied Energy, 92, pp.

593-605.

78

APPENDICES

APPENDIX A: Fourier Transform Infrared Spectroscopy

(a) PCM20 COATED

(b) PCM40 COATED

4000 4003500 3000 2500 2000 1500 1000 500

101

47

50

55

60

65

70

75

80

85

90

95

100

cm-1

%T

1727.30cm-11145.70cm-1

1236.89cm-1

1449.63cm-1

2956.09cm-1

1065.90cm-1

988.95cm-1

963.17cm-1

4000 4003500 3000 2500 2000 1500 1000 500

102

35

40

45

50

55

60

65

70

75

80

85

90

95

100

cm-1

%T

1727.11cm-11145.59cm-1

1236.84cm-1

1449.53cm-1

2955.94cm-1

1065.64cm-1

988.84cm-1

962.87cm-1

79

(c) PCM60 COATED

(d) PCM80 COATED

(e) PCM100 COATED

4000 4003500 3000 2500 2000 1500 1000 500

102

34

40

45

50

55

60

65

70

75

80

85

90

95

100

cm-1

%T

1727.08cm-1 1145.60cm-1

1236.80cm-1

1449.52cm-1

2956.00cm-1

1065.77cm-1

988.92cm-1

962.99cm-1

80

(f) PCM20 NON COATED

(g) PCM40 NON COATED

(h) PCM60 NON COATED

4000 4003500 3000 2500 2000 1500 1000 500

99.8

93.2

93.5

94.0

94.5

95.0

95.5

96.0

96.5

97.0

97.5

98.0

98.5

99.0

99.5

cm-1

%T

1696.80cm-1

2912.02cm-1 2847.77cm-1

1471.12cm-1 1145.94cm-1

1236.93cm-1

7 1 6 . 6 9 c m - 1

1190.26cm-1

1260.55cm-1

1433.07cm-1

916.43cm-1

750.88cm-1

81

(i) PCM80 NON COATED

(j) PCM100 NON COATED

4000 4003500 3000 2500 2000 1500 1000 500

100

88

89

90

91

92

93

94

95

96

97

98

99

cm-1

%T

1698.74cm -1 1146 .00cm -1

1723.01cm-12913.66cm-11190.42cm-12848.50cm-1

1237.20cm -1

1471.35cm-1

1261.00cm-1

1434.47cm-1

717.07cm-1

9 1 5 . 0 5 c m - 1

82

APPENDIX B: Differential Scanning Calorimetry

(a) PCM20 COATED

83

(b) PCM40 COATED

84

(c) PCM60 COATED

85

(d) PCM80 COATED

86

(e) PCM100 COATED

87

(f) Pure myristic acid

88

APPENDIX C: Conference Proceeding

Conference Proceeding Title: DEVELOPMENT OF FORM STABLE COMPOSITE

PHASE CHANGE MATERIAL WITH POLYMER COATING FOR THERMAL

ENERGY STORAGE

By: Shin Yiing Kee, Yamuna Munusamy, Kok Seng Ong, Swee Yong Chee, and Yu

Gen Qian

Citation: Proceeding – 3rd

Putrajaya International Built Environment, Technology

and Engineering Conference, (2017); ISBN: 978-967-2072-10-2

Published by the Proceeding – 3rd

Putrajaya International Built Environment,

Technology and Engineering Conference (PIBEC3)

89

90

APPENDIX D: Novel Research and Innovation Competition 2017 (NRIC)

(a) Poster of “FOSTPCM For Photovoltaic Cooling”

91

(b) Participants (From left: Yu Gen Qian, Nagarathanam, Ariff)

92

(c) Certificate of Bronze Medal of NRIC