PERFORMANCE INVESTIGATION OF A SOLAR THERMOELECTRIC-ADSORPTION COOLING SYSTEM USING

ACTIVATED CARBON-METHANOL

Ngui Jia Lin

Master of Engineering 2011

Pusai kitiil111At Maiclumat AKyUPmiK UMVERSITI MALAYSIA SARAVY. AK

PERFORMANCE INVESTIGATION OF A SOLAR THERMOELECTRIC-ADSORPTION COOLING SYSTEM USING

ACTIVATED CARBON-METHANOL P. KHIDMAT MAKLUMAT AKADEMIK

111111111 jl 111 III 1I II III 1000246330

NGUI MA LIN

A thesis submitted in fulfillment of the requirement for the Degree of

Master of Engineering (Energy)

Faculty of Engineering UNIVERSITI MALAYSIA SARAWAK

2011

Dedicated to my beloved family and friends

ACKNOWLEDGEMENT

The challenging task of completing the project has finally come to its end. The

completion of this project brings such a tremendous joy and is achieved with a sense of

satisfaction. Nevertheless, this achievement certainly cannot be made without the help and

support of many individuals.

First of all, I would like to express my sincere gratitude to my main supervisor,

Associate Professor Dr. Mohammad Omar Bin Abdullah for his undivided attention and

guidance which he has sought to give throughout the course of completing the project. His

advice and support have given me ideas and notion to proceed with the tasks of the project

with success. Apart from that, I would like to thank my co supervisor, Professor Khairuddin

Abdul Hamid as well for his help and guidance throughout the project.

My heartfelt thanks to Mr Leo, Mr Tie and Mr Tang; as well as lab technicians, Mr

Masri and Mr Ruzaini for their ongoing help all this time. These wonderful individuals

showed their kindness and willingness to assist me during my times of trouble without

hesitations. I am extremely grateful for all the advice and assistance that they have

contributed.

Finally, I would like to further express my thanks to my beloved family for their

never-ending support as well as other individuals who has involved directly or indirectly

towards the success of this project.

i

ABSTRACT

(Apart from the conventional compression cycle refrigeration, two other known

cooling technologies throughout the last decade are thermoelectric and adsorption. Solar

adsorption utilizes activated carbon-methanol as its working pair in producing cooling

through desorption/adsorption processes. Solar thermoelectric however utilizes the conversion

of solar energy to electricity by means of photovoltaic cells to power up the cooler. Both

systems have witnessed an increasing interest due to its quietness, long-lasting, inexpensive to

maintain and environmentally benign. In this study, a combined system of both techniques

was introduced, where cooling could be produced continuously and suitable for places away

from the conventional grid )The

adsorption system utilized few key elements such as

adsorbers, a condenser, a reservoir, an evaporator and a cooler. The thermoelectric system

was powered by two 80W solar photovoltaic panels and is regulated using a charge controller

and a battery as a backup system. The principle aim of this study was to gather relevant data

through experiments and act as basis for future studies. Results from the experiments were

later used to calculate the coefficient of performance (COP). The relevancy of the results was

then further proved and determined with a series of statistical studies. Results obtained

showed that such system is feasible. The COP values of the overall system were 0.014 -

0.183 (adsorption), 0.126 - 0.173 (thermoelectric) and 0.003 - 0.005 (hybrid), respectively.

11

ABSTRAK

Selain daripada penyejukan kitaran mampatan konvensional, dua jenis teknologi

pendinginan terkenal yang lain sepanjang dekad lalu adalah teknologi termoelektrik dan

penjerapan. Solar jerapan menggunakan pasangan kerja karbon teraktif-metanol

menghasilkan pendinginan melalui nyah jerapan/muat jerapan. Suria termoelektrik

bagaimanapun menggunakan penukaran tenaga suria untuk bekalan elektrik dengan cara sel-

sel fotovolta untuk memulakan penggunaan pendingin. Kedua-dua sistem ini telah mendapat

mint yang meningkat kerana senyap, tahan lama, murah untuk dijaga dan ramah

lingkungan. Dalam kajian ini, sistem bergabungan kedua-dua teknik diperkenalkan, di mana

pendinginan boleh dihasilkan secara berterusan dan sesuai untuk tempat yang jauh daripada

kekisi konvensional. Sistem penjerapan menggunakan beberapa elemen-elemen penting

seperti penyerap, pemeluwap, takungan, penyejat dan pendingin. Sistem termoelektrik adalah

dihasilkan oleh dua panel-panel suriafotovolta dan diatur menggunakan satu pengawal dan

satu deretan bateri seperti satu sistem bantuan. Tujuan kajian ini adalah untuk mengumpul

data-data eksperimen dan sebagai asas untuk kajian-kajian masa hadapan. Keputusan dari

eksperimen-eksperimen itu kemudiannya telah digunakan bagi mengira pekali prestasi

(COP). Kajian-kajian statistik dibuat untuk membuktikan kerberkaitan keputusan-keputusan

tersebut. Keputusan-keputusan yang diperolehi menunjukkan sistem yang sedemikian boleh

dilaksanakan. Pekali prestasi keseluruhan sistem adalah masing-masing 0.014 - 0.183

(penjerapan), 0.126 - 0.173 (termoelektrik) dan 0.003 - 0.005 (hibrid).

III

fusýt KhidmstýýVSIA SAR+, WAK &pwRSt`t7

TABLE OF CONTENTS

ACKNOWLEDGEMENT

ABSTRACT

ABSTRAK

TABLE OF CONTENTS

LIST OF TABLES

LIST OF FIGURES

NOMENCLATURE

CHAPTER 1: INTRODUCTION

1.1 General Introduction

1.2 Importance of Topic

1.3 Problem Statement

1.4 Research Objective

1.5 Research Scopes

CHAPTER 2: LITERATURE REVIEW

2.1 Theories

2.1.1 Laws of Thermodynamics

2.1.2 Adsorption

2.1.3 Thermoelectric

PAGE

ii

III

IV

ix

XI

XIV

I

3

3

4

4

5

5

6

7

iv

2.2 Designs 9

2.2.1 Solar Adsorption Cooling System 9

2.2.2 Solar Thermoelectric Cooling System 13

2.2.3 Hybrid Solar Thermoelectric-Adsorption

Cooling System 15

2.2.4 Difference between Solar Adsorption

and Thermoelectric Cooling System 16

2.3 Important Equations 17

2.3.1 Adsorption Refrigerant Quantity

2.3.2 Adsorption Adsorbent Quantity

2.3.3 Coefficient of Performance (COP)

2.3.4 Statistical Studies

2.3.4.1 Q-Q Plot

2.3.4.2 Paired Samples t-test

2.3.4.3 Error Bars

2.3.4.4 Curve Estimation

2.3.4.5 Review Summary

17

22

23

25

26

26

27

27

27

CHAPTER 3: METHODOLOGY

3.1 Project Methodology 29

3.2 Part Description of the Solar Adsorption Cooling System 30

3.2.1 Adsorber Bed 30

3.2.2 Heat Trap Collector 32

3.2.3 Condenser 33

V

3.2.4 Support Frame

3.2.5 Reservoir Tank

3.2.6 Support Frame (Reservoir Tank)

3.2.7 Built-in Evaporator

34

35

36

37

3.2.8 Cooler 38

3.2.9 Solar Adsorption Cooling System (Final Design) 39

3.3 Part Description of the Solar Thermoelectric

Cooling System 40

3.3.1 Solar Panel 41

3.3.2 Charge Controller 43

3.3.3 Battery 44

3.3.4 Thermoelectric Cooler 46

3.3.5 Solar Thermoelectric Cooling System

(Final Design) 47

3.4 Hybrid Solar Thermoelectric-Adsorption

Cooling System (Final Design) 48

3.5 Measuring Equipments 50

3.5.1 Thermocouple Reader 50

3.5.2 Hygrometer 51

3.5.3 Multi Meter 52

3.5.4 Clamp Meter 53

3.5.5 Manifold Gauge 53

3.6 Experimental Procedures 54

3.6.1 Solar Adsorption Cooling System

vi

(Leakage Test) 54

3.6.2 Solar Adsorption Cooling System

(Vacuum Test) 55

3.6.3 Solar Adsorption Cooling System (Testing) 55

3.6.4 Solar Thermoelectric Cooling System

(Assemblies) 56

3.6.5 Solar Thermoelectric Cooling System (Testing) 56

3.6.6 Hybrid Solar Thermoelectric-Adsorption

Cooling System (Testing)

3.7 COP Calculations Procedures

57

57

3.8 Statistical Studies Procedures 57

CHAPTER 4: RESULTS AND DISCUSSION

4.1 Solar Adsorption Cooling System 59

4.1.1 Clear and Sunny

4.1.2 Sunny with Clouds

4.1.3 Cloudy

62

65

67

4.2 Solar Thermoelectric Cooling System 69

4.2.1 Clear and Sunny

4.2.2 Sunny with Clouds

4.2.3 Cloudy

4.3 Hybrid Solar Thermoelectric-Adsorption

Cooling System

4.4 Statistical Studies

70

72

74

76

78

vii

4.4.1 Q-Q Plot

4.4.2 Paired samples T-Test

4.4.3 Error Bars

4.4.4 Curve Estimation

CHAPTER 5: CONCLUSION

5.1 Conclusion

5.2 Recommendations

REFERENCES

79

83

85

87

92

94

95

APPENDICES 102

Appendix A- Apparatus calculations 102

Appendix B- Adsorption cooling system (by date) 105

Appendix C -Thermoelectric cooling system (by date) 115

Appendix D -Hybrid solar thermoelectric-adsorption

cooling system (by date) 120

Appendix E- COP calculations 124

Appendix F- Curve estimation calculations 126

viii

LIST OF TABLES

TABLE PAGE

2.1 Solar adsorption and thermoelectric cooling system - differences 16

2.2 Properties of Merck methanol GR for analysis 21

2.3 Properties of coconut-based activated carbon (Bravo Green Sdn Bhd) 22

3.1 Adsorber bed design specifications 31

3.2 Heat trap collector design specifications 32

3.3 Condenser design specifications 34

3.4 Support frame design specifications 35

3.5 Reservoir tank design specifications 36

3.6 Support frame (reservoir tank) design specifications 36

3.7 Built-in evaporator design specifications 38

3.8 Solar panel specifications from BP Solar® 41

3.9 Steca® 20A charge controller specifications 43

3.10 Niko® classic battery specifications 45

3.11 Cool Boy thermoelectric cooler specifications 46

4.1 Results of the solar adsorption cooling system (By range and date) 61

4.2 Results of the solar thermoelectric cooling system (By range and date) 69

4.3 Results of the solar adsorption cooling system

(By range and date) - Hybrid 77

4.4 Results of the solar thermoelectric cooling system

(By range and date) - Hybrid 77

IX

4.5 COPnet after calculations

4.6 Estimated distribution parameters (Normal Plot)

4.7 Estimated distribution parameters (Lognormal Plot)

4.8 Paired samples statistics (COPads and COPpi)

4.9 Paired samples test (COPads and COPp1)

4.10 Model summary and parameter estimates (COPads)

4.11 Model summary and parameter estimates (COPpi)

4.12 Estimated COP values by test distributions

77

79

81

84

84

87

88

91

X

LIST OF FIGURES

FIGURE PAGE

2.1 Thermoelectric cooler 7

2.2 Principle of adsorption cooling system 9

2.3 Clayperon diagram of an adsorption cycle 10

2.4 Adsorption properties test unit 19

2.5 Estimated adsorption quantity of refrigerant in the activated carbon

versus saturated refrigerant temperature, at three different adsorption

temperatures of activated carbon. 20

3.1 Project methodology 29

3.2 3-d diagram and photo of an adsorber bed 31

3.3 3-d diagram and photo of a heat trap collector 33

3.4 3-d diagram and photo of a condenser 34

3.5 3-d diagram and photo of a support frame 35

3.6 3-d diagram and photo of a reservoir tank 36

3.7 3-d diagram and photo of a reservoir tank's support frame 37

3.8 3-d diagram and photo of a built-in evaporator 38

3.9 3-d diagram and photo of a cooler 39

3.10 3-d diagram and photo of the final design - adsorption 39

3.11 Schematic diagram of the solar adsorption cooling system 40

xi

3.12 3-d diagram and photo of the solar panel 42

3.13 3-d diagram and photo of the charge controller 43

3.14 3-d diagram and photo of the battery 45

3.15 3-d diagram and photo of the thermoelectric cooler 46

3.16 3-d diagram and photo of the final design - thermoelectric 47

3.17 Schematic diagram of the solar thermoelectric cooling system 48

3.18 Photo of the hybrid solar thermoelectric-adsorption cooling system 49

3.19 Schematic diagram of the hybrid solar thermoelectric-adsorption 49

cooling system

3.20 Photo of the thermocouple reader 50

3.21 Photo of the hygrometer 51

3.22 Photo of the multi meter 52

3.23 Photo of the clamp meter 53

3.24 Photo of the manifold gauge 53

4.1 Variations of temperature and humidity with time - 25 May 2009 62

4.2 Variations of temperature with time -25 May 2009 64

4.3 Variations of temperature and humidity with time - 20 April 2009 65

4.4 Variations of temperature with time - 20 April 2009 66

4.5 Variations of temperature and humidity with time - 27 April 2009 67

4.6 Variations of temperature with time - 27 April 2009 68

4.7 Variations of ampere with time -3 March 2009 70

4.8 Variations of voltage with time -3 March 2009 71

4.9 Variations of ampere with time - 20 April 2009 73

Xll

4.10 Variations of voltage with time - 20 April 2009 73

4.1 1 Variations of ampere with time - 27 April 2009 75

4.12 Variations of voltage with time - 27 April2009 75

4.13 Normal Q-Q Plot of COPads 79

4.14 Normal Q-Q plot of COPpi 80

4.15 Normal Q-Q plot of COPnet 80

4.16 Lognormal Q-Q Plot of COPads 82

4.17 Lognormal Q-Q plot of COPpi 82

4.18 Lognormal Q-Q plot of COPnet 83

4.19 Error bars of coefficient of performance (adsorption/thermoelectric) 85

at various days

4.20 Error bars of coefficient of performance (hybrid solar 86

thermoelectric-adsorption) at various days

4.21 Curve estimation of COPads versus time 89

4.22 Curve estimation of COPpi versus time 90

XIII

NOMENCLATURE

Acronyms

ASTM American Society for Testing and Materials

BET Brunauer-Emmett-Teller

Bi2Te3 bismuth telluride

CaCl2 calcium chloride

CFC chlorofluorocarbon

COP coefficient of performance

COPSR gross coefficient of performance

CTC Carbon Tetrachloride Capacity

D-A Dubinin-Astakhov

Exp exponent

ID internal diameter

L length

OD outer diameter

pH power of hydrogen

Sb2Te3 antimony telluride alloys

SEM Scanning Electron Microscope

SPSS Statistical Package for the Social Sciences

xiv

Variables

A adsorption potential

Cp specific heat capacity (J/(g°C))

E characteristic adsorption energy of a vapour

h height

I amperage (A)

J joule (J)

M mass (g or kg)

n degree of heterogeneity of the micropore system; for activated carbon usually

it is from 1.5 to 3

Qe heat supplied to the adsorber (J)

Qh heat removed through the hot side (J)

r radius

t time needed to reach its lowest cooling state (s)

T adsorption temperature (K)

ATe temperature change in the evaporator (°C)

ATg temperature change in the adsorber (°C)

ATioad temperature change in the load (°C)

TS saturated temperature of refrigerant (K)

V voltage (V)

Will work supplied into the thermoelectric cooler (J)

x adsorption quantity of refrigerant in the activated

carbon (kg/kg)

xv

x0, k, n coefficients

Subscripts

ad adsorption

b 1, b2, b3 parameter estimates

df degree of freedom

net

PI

rdg

Sig

Std

t

net

thermoelectric

reading

probability

standard

test statistic

xvi

CHAPTER I

INTRODUCTION

1.1 General Introduction

Adsorption and thermoelectric cooling systems are some of the cooling systems available

around the globe. Solar adsorption cooling system has witnessed an increasing interest in many

fields, because of its quiet operation, long-lasting, inexpensive to maintain, and environmentally

benign [1,2]. Solar thermoelectric cooling system shares the same advantages with simple setup,

less maintenance and easily available in most countries throughout the world. These two systems

share a common ground on the production of cooling through heat and photons from the sun.

Some previous studies were done by various researchers from early 1990's till now. For

example, Pons and Guilleminot [3] developed an icemaker based on the solar-powered

adsorption system with activated carbon-methanol as the working pair. The coefficient of

performance (COP) of 0.12was achieved with a production of 6 kilograms of ice per square

meter of solar collector/adsorber. Liu et al. [4] on the other hand, developed an adsorption chiller

with the working pair of silica gel-water, powered by a solar water heater. A cooling power of

3.56kW and a COP value of 0.26 were obtained with their prototype. On thermoelectric cooling

technology, Abdul-Wahab et al. [5] experimented on a solar thermoelectric refrigerator for

I

application in the remote parts of Oman. They can achieve a COP value of 0.16, with a

temperature reduction from 27 °C to 5 °C in approximately 44 minutes.

The introduction of this project in Universiti Malaysia Sarawak came about in year 2005.

As Malaysia is situated around the equator, solar energy is a source of energy that is widely

available here for free. Researchers tend to look further into this energy as a substitution to

electricity generated from coal and other modes of traditional energy. Due to further interest in

adsorption and thermoelectric cooling systems, a research was proposed on this area. Most

referencing were done based on ideas generated by Li and Sumathy [6] and Abdul-Wahab et al.

[5].

With different specifications in terms of adsorber sizes and coconut based activated

carbon, this thesis aims to test both systems and get reliable results via experimental studies.

Statistical studies were incorporated into this thesis as well to further proof and estimate the COP

for both systems. Furthermore, a hybrid system was modified using both systems and tested

during the end of 2009. This was to determine whether continuous cooling could happen if both

systems were utilized at the same time. The study subsequently reported the performance of the

three systems, COPS and other transient parameters such as temperatures, pressures, voltages,

amperages and humidities over time. Here, one should note that, because of the overall high

humidity in Malaysia, clouds are inevitable sometimes, and this often has resulted in a random

amperage and voltage of the photovoltaic cells, as well as random heat being absorbed by the

adsorber bed.

2

1.2 Importance of Topic

The importance of the topic stems on how reliable the systems are in achieving cooling

and how far the systems go down below ambient temperature. With the implementation of

statistical studies, the range values of all the above mentioned systems can be calculated and

tabulated in graphs. This can be used for commercialization purposes that aim to help those

living in rural areas and those areas without electricity coverage.

1.3 Problem Statement

Although studies have been done before on adsorption systems, more research could be

done to further enhance the results obtained by experimenting using different sets of working

pairs and testing them in different locations and weather conditions. For example, in 1998, Li

and Sumathy [6] attempted on a study based on the solar adsorption system. They utilized

activated carbon-methanol as the working pair to start a solar-powered ice-maker. To generate

ice, the evaporator temperature must be <0 °C. The above system could generate a COP of about

0.1-0.12. However, a cooling system without ice-maker has not been studied yet in Malaysia and

in this study the aim of increasing the COP to more than 0.12 has been successful. Abdul-Wahab

et al. [5] designed a system of using 10 thermoelectric modules to power up a refrigerator and

has been successful as well. Bigger wattage module was utilized to power up a refrigerator and

managed to acquire almost similar results as discussed in chapter 4. This study proves to utilize a

combined system rather than a single system (as per designed by Abdul-Wahab et al. [5], where

3

cooling could be produced continuously in places far away from conventional grid. Most rural

folks may benefit from this system in years to come.

1.4 Research Objective

The main objective of the study is to build up a solar thermoelectric-adsorption cooling

system capable of producing cooling continuously. Experimental and statistical studies are

performed to determine the COP values of the individual adsorption and thermoelectric cooling

system as well as the hybrid system. The COP values may signify the actual performance of the

system which will determine the cooling power of the cooler.

1.5 Research Scopes

In order to achieve the objective, several scopes have been outlined:

1. To gain a better understanding of the basic adsorption, thermoelectric and hybrid

solar thermoelectric-adsorption cooling systems through background study and

system assembly.

2. To discuss on the experimental results based on different weather patterns and to

calculate the coefficient of performance (COP) values using these acquired results.

3. To further proof the reliability of the calculated COP values and to estimate the

range of the actual COP values through statistical studies using Q-Q plot, paired-

samples t-test and curve estimation. Systematic errors are proposed to determine

the differences between different days.

4

Pusat Khidmat Maklumat Akadrrniý UNIVERSITI MALAYSIA SARAWAK

CHAPTER 2

LITERATURE REVIEW

In this chapter, the theories of the overall systems, followed by the designs and finally on

how to derive the important equations were discussed. These equations were needed in

calculating the adsorbent quantity needed in the adsorption system, as well as the refrigerant

quantity being pumped into the system. The coefficients of performance (COP) equations were

derived from past studies to assist in the calculations needed to judge the performance of every

system. Statistical studies were then proposed to examine the cohesiveness of the experimental

data versus the expected data through implementation of mathematical models.

2.1 Theories

2.1.1 Laws of Thermodynamics

A basic system which incorporates heating or cooling elements must start with the law of

thermodynamics. According to the engineering term taken from Ejup and Tyler's Engineering

Companion Book [7], it was stated that the First Law of Thermodynamics is the law of the

conservation of energy. Energy cannot be created nor destroyed, but it can be transformed from

one form to another. During any process, the total energy of any system and its surroundings is

5