Post on 07-Apr-2019
transcript
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