Integration of Absorption Heat Pump, Methanol Steam Reforming, and Fuel Cell Systems:

Feasibility Study and Analysis

Undergraduate Final Project Thesis

Submitted in partial fulfillment of the requirements to obtain a Bachelor of

Science Degree in Physics at Institut Teknologi Bandung

by

Willy Yanto Wijaya 10203052

Physics Study Program

Faculty of Mathematics and Natural Sciences Institut Teknologi Bandung

2008

Approval

Integration of Absorption Heat Pump, Methanol Steam Reforming, and Fuel Cell Systems:

Feasibility Study and Analysis

by

Willy Yanto Wijaya 10203052

Physics Study Program

Faculty of Mathematics and Natural Sciences

Institut Teknologi Bandung

This Undergraduate Final Project Thesis had been presented on February 6th, 2008

Supervisors: Dr. Abdul Waris Prof. Ken Okazaki Assoc. Prof. Kazuyoshi Fushinobu

Examiners: Dr. Novitrian Dr. Nurhasan Dr. Rizal Kurniadi

Approved by

Supervisor,

Dr. Abdul Waris NIP: 132084050

This Final Project Thesis is dedicated

for Beloved Mom, Dad, Brothers and Sisters 妈妈，爸爸，弟弟，妹妹 のために。

As is common in Japanese homes, I was lying on a futon that was spread out directly on the floor covered with tatami mats. My mother, who had probably not slept for several nights, was sitting at the head of the futon and looked down at me. Slowly and so softly that it seemed weird even to me, I tried to speak. “Mother, do I have to die?”

“I don’t believe that you will die. I pray that you won’t die.”

“The doctor said, ‘The child will probably die.’ He said he couldn’t do anything else for me. I heard it. I think I have to die.”

My mother was silent for a while. Then she said, “Should you die, I will give birth to you again. Don’t be concerned about it.”

“But if I die now, that child would be a different one than me.”

“No, it would be the same,” my mother said. “Once I give birth to the new you, I will tell the new you everything you have seen and heard up to now, all that you’ve read and all that you’ve done. And since the new you will also speak the language you are now speaking, the two children will be completely alike.”

Kenzaburo Oe Nobel Prize Laureate in Literature 1994

ABSTRACT

Theoretically, Methanol Steam Reforming (MSR) process to produce

hydrogen only requires endothermic heat with temperature lower than 100°C.

Meanwhile, waste heat in the temperature level of 100-150°C is disposed in huge

amount by various industrial sectors every year. If this abundant waste heat can be

recovered and stored into hydrogen energy through the MSR, a potential gain and

high-efficient energy system could be achieved. However, empirically, temperature

level ≥ 200°C is required for the MSR process to have high conversion from the

methanol to hydrogen. Therefore, Absorption Heat Pump (AHP) system is then

utilized to enhance the temperature level of the waste heat. Nevertheless, AHP

system certainly requires additional input energy. This research was to investigate

the feasibility of integrating the AHP system into MSR process to produce hydrogen.

Further consideration on hydrogen to electricity conversion using Fuel Cell (FC)

would also be provided. The feasibility study was conducted through the efficiency

calculations, either for energy or exergy terms, for several theoretical as well as

actual-approximation cases.

Keywords: Exergy, Absorption Heat Pump, Methanol Steam Reforming, Fuel Cell, Hydrogen

Production, Efficiency

v

ABSTRAK

Secara teoritis, proses Methanol Steam Reforming (MSR) untuk

menghasilkan hidrogen hanya membutuhkan kalor endotermik dengan suhu di

bawah 100°C. Sementara itu, kalor sisa dalam kisaran suhu 100-150°C terbuang sia-

sia dalam jumlah yang sangat besar oleh berbagai sektor industri setiap tahunnya.

Seandainya sejumlah besar kalor sisa ini dapat dimanfaatkan kembali melalui proses

MSR agar tersimpan dalam bentuk energi hidrogen, akan diperoleh potensi

peningkatan kualitas energi dan juga bukan tidak mungkin suatu sistem energi

berefisiensi tinggi akan dapat dicapai. Akan tetapi, secara empirik, level suhu ≥

200°C dibutuhkan oleh proses MSR agar terjadi tingkat konversi yang tinggi dari

metanol menjadi hidrogen. Oleh sebab itulah, sistem Absorption Heat Pump (AHP)

kemudian digunakan untuk meningkatkan level suhu dari kalor sisa tersebut. Akan

tetapi, sistem AHP tentu saja membutuhkan input energi tambahan. Penelitian ini

bertujuan untuk mengkaji kelayakan pengintegrasian sistem AHP ke dalam proses

MSR untuk produksi hidrogen. Pertimbangan lebih lanjut terhadap konversi hidrogen

ke listrik menggunakan sel bahan bakar (fuel cell) juga akan dilakukan. Studi

kelayakan ini dilakukan melalui perhitungan efisiensi, baik untuk kasus energi

maupun exergy, untuk beberapa kasus teoritis maupun pendekatan aktual.

Kata Kunci: Exergy, Absorption Heat Pump, Methanol Steam Reforming, Sel Bahan Bakar,

Produksi Hidrogen, Efisiensi

vi

PREFACE

These last two centuries, starting from the industrial revolution era to the

information technology era, have witnessed the bloom of human civilization. Every

little pieces of technology has almost been absorbed into our daily life to add the

comfort of living. Perhaps, this is the golden era of human civilization which couldn’t

even be imagined by the wildest mind of people living several hundred years ago.

However, if we contemplate deeply, we can see that all these sophisticated advances

in our civilization today are supported by unimaginable, massive consumption of

energy, especially the fossil-fuel energy. Consequently, the rapid depletion of this

fossil fuel is unavoidable. Besides, various environmental problems also emerge,

such as the waste materials management as well as the global warming. All these

problems are imminent, slowly but eventually will give serious impact.

To pick up an example, let’s say, the depletion of fossil fuel. Can we imagine

if we have no more sufficient energy sources? There are several power plants that

use fossil fuel (such as: natural gas, coal) to generate electricity. Depletion of this

fossil fuel means the scarcity of electricity. The scarcity of electricity means less

convenience for us in using electronic devices, such as: television; refrigerator;

computer: web, e-mail, and other e-activities; since frequent electricity “black-out”

might happen. This is not to mention the industries that consume huge amount of

electricity in their production processes, for example: food, clothes, medicine, paper,

machinery industries, etc. Besides the scarcity of electricity, depletion of this fossil

fuel itself also means a “threat” to the transportation systems and other sectors of life.

Scarcity of natural gas; petroleum and its derivative products: gasoline, kerosene,

plastic materials, will halt most transportation systems; hamper the cooking activities

in kitchens; and disrupt all our convenient life-style. In the end, it is not impossible

vii

that this crisis could provoke social riot and disorder. Then, must we end up and step

backward again to the life-style of those several-hundred years before?

Of course, this is an extreme case; however, fortunately human beings are

creatures that always try to maintain their comfort level. Therefore, new technologies

and alternative energy are constantly being developed. To remedy the above-

mentioned nightmare, scientists and engineers have developed the utilization of long-

term or renewable energy: nuclear, wind, photovoltaic, biomass, geothermal, etc, to

generate the electricity. Nevertheless, how about the substitute for gasoline which is

used in transportation sectors? Currently, the strongest candidate is hydrogen.

Why hydrogen? There are several reasons to mention. Besides its portability,

cleanliness and being environmental-friendly, there are many ways for its production

processes. In addition, hydrogen-related technologies are also developing rapidly

nowadays, for example: the fuel cell, hydrogen gas turbine, and hydrogen

combustion engine. Recently, fuel cell has achieved remarkable energy efficiency, up

to 60%.

Talking about the production processes for hydrogen, indeed, nowadays,

most hydrogen is still being produced from natural gas (since it is the most

economical). However, certainly this fossil fuel (natural gas), in the long-term

scenario, will be replaced by electrolysis of water using the renewable energy

sources. This splitting of water molecules to produce hydrogen is expected to be one

of the answers to the scarcity of gasoline in the future.

Certainly, there are still many problems related to this hydrogen energy

expansion. Infrastructure, technical aspects, overall net-efficiency improvement and

sustainability are some important issues to be further considered and tackled.

Nevertheless, sooner or later, this hydrogen economy scheme will be indispensably

realized one day.

viii

It is very sad that our country, Indonesia, still doesn’t have such long vision.

We are still brought into lullaby by the comfort of oil and gas deposit, yet slowly we

are stepping and getting closer to the deep abyss of fossil-fuel crisis.

This thesis is just one little step to stimulate us to start rethinking how

substantial the energy issue in the near future; to tap our awareness and concern to

develop various prospective energy sources, especially hydrogen energy; and to

invite us to appreciate and study more about the energy and all its related

phenomena, physics, and technologies.

ix

ACKNOWLEDGEMENT

Like a falling star in the darkness, or bubbles on water surface,

like evaporating dews on leaves; That’s the way how all changes flow

It’s already been four and a half years my study in ITB (including one year in

Tokyo Tech). Many things have happened, happy or sad, all wrapped together to

become unforgettable lessons and experiences for me. During these years also, I

have received so many helps and kindness, so innumerable that I really feel indebted.

I would like to express deepest gratitude to Dr. Abdul Waris who had

become my final project supervisor. He also had guided me for several years as my

academic supervisor, during which his strong recommendations always gave me

encouragement to apply for the YSEP Program as well as any other scholarships. It’s

also an honor that he gave me opportunity to submit my research paper to the Asian

Physics Symposium (APS) as well as my involvement in Lab Fislan (Advanced

Physics Lab).

Also sincere gratitude to Prof. Ken Okazaki and Assoc. Prof. Kazuyoshi

Fushinobu who had become my research supervisors during my study in Japan. I

really learned a lot of things from their awesome knowledge in hydrogen energy

system.

I would also like to express sincere gratitude to Dr. Novitrian and Dr.

Nurhasan for becoming examiners of my final project thesis. Thanks for the

discussions and suggestions during the final project presentation. Also to Dr. Rizal

Kurniadi for becoming examiner of my first half-part final project thesis, as well as for

x

the interactions during which I became assistant of UPK and interactions in several

lectures.

Sincere thanks to the Dean of FMIPA ITB Dr. Akhmaloka and former

chairman of Physics Study Program Dr. Pepen Arifin, for the supports and

recommendation in my application for YSEP. Furthermore, I’d like to thank the

chairman of Physics Study Program Dr.rer.nat. Umar Fauzi for the academic helps;

Dr. Freddy Haryanto for the warm kindness and scholarship recommendation; Dr.

Daniel Kurnia for the guidance while I became the experiment assistant of LFD

(Elementary Physics Lab); Dr. Herman Bahar for lending me the Kanji book before

my departure to Japan; Dr. Zaki Su’ud and Dr. Wahyu Srigutomo for giving me

opportunity to be involved in the ICANSE and APS; (late) Dr. Hans J. Wospakrik for

the great lectures and inspiration; Dr. Ing. Mitra Djamal for my involvement in ICICI;

Dr. Toto Winata, Dr. Sukirno, Dr. Eng. Mikrajuddin Abdullah, Dr. Idam Arief, Dr.

Rena Widita, Dr. Khairurrijal, Dr. Suprijadi, Dr. Enjang J. Mustopa, Dr. Satria

Bijaksana, Dr. Wilson W. Wenas, and all other Physics Study Program lecturers for

the invaluable classes, care and interactions during my study in ITB.

I’d also like to extend my gratitude to all the administrative staffs of Physics

especially Pak Yeye, Pak Daryat, Pak Imbalo, Bu Ratna, and Bu Sri; to Pak Dede

Enan of UPK Fisika; as well as Bu Silvy of the library of Physics.

Sincere thanks for the help and interactions to all the members of the

laboratory of Nuclear Reactor Physics: Pak Ali Safii, Pak Epung Saepul, Bu Yanti,

Pak Alan Maulana, Pak Imam Taufiq, Pak Ade Gaffar, Insan Kamil, Deby M,

Aditya, Rida, Syeilendra P, and Dythia.

It’s also a pleasure to deliver my gratitude to Bu Ayi Rohiyati and Bu Indah

of ISO ITB for the application/procedure upon YSEP; to Pak Bambang Supriyanto,

M.Ed of ITB Language Center for the spiritful encouragement.

xi

Very special thanks to Agustina who helped me so much with the registration

in ITB while I was in Japan; managing the scholarship administration; conducting

negotiation for various procedures; without whom there wouldn’t be ease of mind in

my study process. I am really indebted. Thanks as well to Thomas Muliawan for

various helps and discussions; to Satria Zulkarnaen for the pdf sample of his final

project thesis; to Liherlinah and Pardi S.Tola for the team-work in several tasks in

electronic-material physics class; to Rifqy M for the discussions about methanol

reforming process; to M. Yusuf, Aunuddin, Rena Denya, A. Nur Izzatul, Anissa R,

Adam Romulo, Hani NS, Maureen L, Harri Sapto W, Amalia, Irsyad A Lubis,

Ferdi Perdana, Desti Alkano, Agus Rijal, Sandy Wibisono, Imamal M, Zamzam

BZ, Hindra Kurniawan, Badai Samudera, M. Sanny, Eka Setiya, Sopian, Heri

Permadi, H. Saut, Christian Kurniawan, K. Ni’am, Yanuar Syapaat, and to all

other Physics 2003 students that I couldn’t mention one by one; thanks for the

togetherness and interactions.

Besides concerning my academic study, I would also like to express sincere

gratitude to all my friends outside; especially to all my friends in PVVD (Pemuda

Vihara Vimala Dharma) and KMB Dhammanano ITB. I had a lot of precious moments

that I would never forget.

During my stay in Japan, I also met many people and got a lot of helps.

Sincere thanks to all members of EPL (Energy Phenomena Lab): Asst. Prof.

Tomohiro Nozaki and Asst. Prof. Shigeru Tada; Ms. Reiko Tajima and Ms. Nami

Kashiwabara for the kind heart and administrative helps; Tomoyuki Hatakeyama,

Kimiharu Yamazaki, Takuya Okada, Takashi Ichiya, Tomohisa Ogino, Ohnishi

Kuma, Takashi Nakamuta, Wataru Fukui, Yuuki Okano, Hironori Shiozaki,

Yasufumi Yamamoto, Kentaro Yamada, Junichiro Yamamoto, Makoto

Kawamorita, Takuya Karatsu, and Munehiro Chijiiwa for all the helps and

xii

kindness. Also thanks to my comrades in EPL: Manuel Philipp Wacker (Germany),

Delphine Prevost (France), and Saiful Hasmady (Malaysia) for lending me the very

useful book about thermodynamics.

It’s also an honour for me to express sincere gratitude to the coordinators of

the YSEP: Prof. Sachio Hirose and Assoc. Prof. Yuriko Sato for all the remarkable

Factory Study Tours and Topic on Japan classes; to Ms. Kudo of ISC (International

Student Center) and Ms. Sakurai for the enjoyable Japanese conversation classes;

Mr. Ueda and Ms. Watanabe for the YSEP administrative procedures; as well as

Ogawa and Oono family for becoming my host families in the YSEP home stay

program.

I also won’t forget to thank sincerely to all YSEP 2006-2007 friends;

especially to Karlisa Priandana that became my only YSEP partner from Indonesia;

to my room-mate Yan Chao (China); Wiwat Keyoonwong (Thailand) for all our

each-other burden sharing; York Hong (USA) for many helps in computer problems;

Lee Juyoung (Korea), Byun Ikjoo (Korea), Yoon Hyoungwon (Korea), Michael

Zamrowski (Germany), Elsa Uggla (Sweden), Johan Rohdin (Sweden), Linda

Guinchard (France), David Starkebaum (USA), Brianna Ford (USA), Teong

Hansen (Singapore), and Liew Wei Jin (Malaysia) for all the friendship and

togetherness.

Thanks also to all friends in Perhimpunan Pelajar Indonesia (PPI) Tokodai,

especially Pak Wawan Budianta (UGM), Farid Triawan, RK, Iman, Yati Suri,

Donny Sunanda, Ikhsan, Acid, Pak Asep Ridwan, Pak Herianto, Mas Awan,

Desiree, Chris Salim, and many others.

Last but not least, I’d like to thank Naoya Arima for discussions upon Kobe

Steel Company data; to my tutor Fumihiko Majima for all the discussions about this

research as well as innumerable helps: fetching me from the Narita Airport to the

xiii

dormitory, managing my various accounts and bills, accompanying me to the hospital,

explaining the research theme patiently, as well as giving me various support and

encouragement. I am deeply indebted.

I understand that I may miss mentioning some of people who, as a matter of

fact, are very important in the processes of my study as well as in my life. I really

apologize deeply for this.

I realized that my existence won’t be able to exist without the existence of all

of you, all the others. We’re all inter-dependent. As an Argentinean author Jorge Luis

Borges ever put it, “everything touches everything.” Yes, also I could say, “everyone

touches everyone.” Thanks for touching me, for the touches blessed in warmth, care,

and kindness.

Thanks for everything.

Wishing you all the best for future endeavours.

いろいろお世話になりました。

Bandung, February 2008.

Willy Yanto Wijaya

xiv

The author would like to thank the followings:

1. JASSO (Japan Student Services Organization)

2. BRI (Bank Rakyat Indonesia)

3. Yayasan Supersemar

4. IOM ITB

5. LPKM ITB

for the scholarship supports during his study in

Institut Teknologi Bandung (Indonesia) as well as in

Tokyo Institute of Technology (Japan)

xv

From this undergraduate thesis and its appendices, the following

papers have been presented or published

• Willy Yanto Wijaya, Integration of Absorption Heat Pump, Methanol Steam

Reforming, and Fuel Cell Systems: Feasibility Study and Analysis, YSEP

Sotsuron Thesis, Department of Mechanical and Control Engineering, Tokyo

Institute of Technology, Tokyo, 2007.

• Willy Yanto Wijaya, Ken Okazaki, Kazuyoshi Fushinobu, Abdul Waris,

Feasibility Study of Integrating Absorption Heat Pump into Methanol Steam

Reforming Process for Hydrogen Production, Proceeding of The 2nd Asian

Physics Symposium, p. D.09.1-9, Bandung, 2007.

xvi

TABLE OF CONTENTS ABSTRACT v ABSTRAK vi PREFACE vii ACKNOWLEDGEMENT x PUBLISHED AND PRESENTED PAPER xvi TABLE OF CONTENTS xvii LIST OF FIGURES xviii LIST OF TABLES xix CHAPTER 1. INTRODUCTION 1 CHAPTER 2. SYSTEMS DESCRIPTION 4 2.1. Absorption Heat Pump (AHP) 4

2.2. Methanol Steam Reforming (MSR) 7

2.3. Fuel Cell (FC) 9

2.4. Integrated System of AHP, MSR, and FC 10

2.5. Hydrogen Production System 11

CHAPTER 3. RESULTS AND DISCUSSION 12 3.1. Energy Efficiency Calculation 12

3.2. Exergy Efficiency Calculation 14

3.3. Alternative Actual-Approximation Cases 15

3.4. Hydrogen Production Efficiency 17

3.5. Exergy Rate Diagram 18

3.6. Additional Discussion 19

CHAPTER 4. CONCLUSION 22 REFERENCES 23 APPENDICES A. DERIVATION OF EXERGY RATE - TEMPERATURE EQUATION 26 B. PROOF OF ENTROPY-BALANCE DERIVED COP FORMULA 28 ABOUT THE AUTHOR 30

xvii

LIST OF FIGURES Figure 1. Waste heat from various industrial sectors disposed per year in Japan 2

Figure 2. Experimental results of methanol conversion with the changes of temperature 2

Figure 3. Absorption Heat Pump Diagram 4

Figure 4. Graph of Absorption Heat Pump Theoretical COP 5

Figure 5. Waste Heat Exergy Rate Enhancement by MSR 8

Figure 6. Integrated System of AHP, MSR, and FC Diagrams 10

Figure 7. Exergy Rate Diagram of the Integrated System 19

Figure 8. Power Plant Combustion System and Efficiency Analysis 20

Figure A1. The Graph of Exergy Rate as a Function of Temperature 27

xviii

LIST OF TABLES Table 1

Detailed Data of the Absorption Heat Pump System 6

Table 2

Enthalpy and Gibbs Energy of Combustion at 25°C, 1 atm 7

Table 3

Exergy Rate and Theoretical Temperature of Various Hydrocarbon 8

Steam Reforming Reactions

Table 4

AHP Heat Output Exergy Content and Exergy Destroyed 11

Table 5

Energy and Exergy Efficiency Calculation Results of the Integrated System of 20

AHP, MSR, and FC

Table 6

Hydrogen Production Energy and Exergy Efficiency Calculation Results 20

xix

CHAPTER 1 INTRODUCTION

Depleting fossil fuel and various environmental problems have pushed the

world to achieve more efficient and sustainable energy systems [1-6]. Attempts have

been made by increasing the power plants efficiency, finding alternative renewable

energy sources as well as introducing various energy-conversion technologies.

In any system comprising of energy conversion processes, the concept of

exergy, besides energy, is very important. It shows us how the potential useful work

can be extracted. Combustion processes are naturally quite irreversible and thus

much exergy is destroyed. Therefore, there should be a less-irreversible way to

convert the chemical energy of the fuel to the useful work (electricity). It was this idea

that gave birth to the concept of Fuel Cell (FC).

Another important point to realize a total high-efficient system is the principle

of material/energy recycling. Endothermic reactions that can make use of the low-

quality energy (i.e. the waste heat) and convert it to high-quality chemical energy will

go along with this recycling principle [7]. Methanol Steam Reforming (MSR) is then

one of them to answer, where this process theoretically only requires less than 100°C

temperature to proceed and currently, extremely abundant heat in the temperature of

100-150°C is being wasted. Even for the case of Japan only, more than 400 PJ* heat

in that temperature level is being wasted every year from various industrial sectors

[8], as shown in Fig.1.

However, in the actual processes, MSR requires temperature level about

200°C. If it is done in the lower temperature, the conversion from the methanol to

hydrogen will decrease significantly as shown in Fig.2. [8]. Since then, many efforts * 1 PJ = 1015 Joule

1

have been made to decrease this reforming process reaction temperature whether by

utilizing membrane/catalyst technology or investigating other MSR parameters’

influence [8-13].

0

100

200

300

400

500

100-

149

150-

199

200-

249

250-

299

300-

349

350-

399

400-

449

450-

499

500-

Temperature of waste heat ºC

Energy PJ

Food Fiber

Paper Chemical

Petroleum Ceramics

Ferrous Non-Ferrous

Mechanics Household appliance

Transportation Gas

Electricity Cleaning

Others

0

100

200

300

400

500

100-

149

150-

199

200-

249

250-

299

300-

349

350-

399

400-

449

450-

499

500-

Temperature of waste heat ºC

Energy PJ

Food Fiber

Paper Chemical

Petroleum Ceramics

Ferrous Non-Ferrous

Mechanics Household appliance

Transportation Gas

Electricity Cleaning

Others

Fig.1. Waste heat from various industrial sectors disposed per year in Japan

0

20

40

60

80

100

50 80 110 140 170 200 230 260Reaction Temperature ゜C

Met

hano

l Con

vers

ion

% S/C=4.0 GHSV=6400S/C=2.0 GHSV=4800 S/C=4.0 GHSV=12800S/C=1.0 GHSV=3200S/C=1.0 GHSV=6400S/C=1.0 GHSV=1300Equil.

Fig.2. Experimental results of methanol conversion with the changes of temperature.

S/C is the Steam to Carbon (methanol) mol ratio (mol/mol) and GHSV (Gas Hourly Space Velocity) = initial flow/volume of catalyst layer (1/h).

2

Another possibility is to increase the temperature level of the waste heat. For

this reason, Absorption Heat Pump (AHP) system is then utilized to increase the

waste heat temperature level. AHP is a highly efficient system in the term of exergy

and recycling principle since the main energy-source input is heat and only a little

amount of pump work is required. It has been widely used in the application of space

heating and big-scale industrial processes [14-17].

Therefore, integrating these AHP, MSR and FC systems will suggest a hint

that a total high-efficient energy system can be realized. However, how feasible this

integrated system will be, still need to be verified. This paper will investigate the

feasibility of this integrated system by means of energy/exergy efficiency calculation

and analysis for several theoretical as well as actual-approximation cases.

Besides, a special consideration will be given in particular for the hydrogen

production efficiency. The main reason is due to the development of various

technologies using hydrogen energy, in which one of them is fuel cell. Therefore,

knowing the hydrogen production efficiency will also give us more vivid

understanding of how MSR and AHP can play role in the exergy enhancement of the

low quality waste heat.

3

CHAPTER 2 SYSTEMS DESCRIPTION 2.1. Absorption Heat Pump (AHP)

Our investigation on the AHP system will be based on the heat pump system

constructed by Ebara Corporation [18,19]. Fig.3 shows the simplified diagram of the

actual system.

Evaporator Absorber

GeneratorCondenser

refrigerant

refrigerant

refrigerant

refrigerant

(gas)

(gas)

solution

(liquid)HEX

TE

TC

TG

TA

90°C

80°C85°C

output

32°C

36°C

37°C

80°C

solution

cooling water

warm water

warm water/waste heat

QAQE

QC QG

steam

pump

Evaporator Absorber

GeneratorCondenser

refrigerant

refrigerant

refrigerant

refrigerant

(gas)

(gas)

solution

(liquid)HEX

TE

TC

TG

TA

90°C

80°C85°C

output

32°C

36°C

37°C

80°C

solution

cooling water

warm water

QAQE

QC QG

steam

pump

warm water/waste heat

Fig.3. Absorption Heat Pump Diagram

Here, the heat input to the AHP system is QG (in Generator) and QE (in Evaporator).

On the other hand, the heat output from the AHP system is QA (in Absorber) and QC

(in Condenser). However, only QA is the desired output which will be transmitted as

the heated steam input to the MSR process. The heat input to this AHP system itself

is the waste heat contained in the warm water in temperature of 90°C. The

temperature of both Generator and Evaporator (TG and TE) is about 80°C, and 37°C

4

for Condenser (TC). For the case of Absorber, the temperature (TA) will be adjusted to

three cases: 120°C, 160°C and 200°C by increasing the number of heat-up step.

Besides the waste heat input, another energy input source to the AHP is the

electricity to drive the pumps. This amount of electricity is relatively small since the

pump only work on the liquid/refrigerant solution.

Then, from the thermodynamics point of view, we have Heat Balance

equation:

CAGE QQQQ +=+ , (1)

and Entropy Balance equation:

D

EG

A

A

C

C

TQQ

TQ

TQ +

=+ , (2)

where TE = TG = TD. Combining Eqs. (1) and (2), we can get Coefficient of

Performance (COP) of the AHP as follow (see Appendix B):

))((D

CD

CA

A

EG

A

TTT

TTT

QQQCOP −

−=

+= . (3)

Substituting the values of TD and TC to Eq. (3) with TA as the changing variable, the

values of COP will be gained as shown in the Fig.4.

0.2

0.3

0.4

0.5

0.6

0.7

0.8

363 373 383 393 403 413 423 433 443 453 463 473 483 493 503 513 523 533

Temperature of Absorber (K)

AH

P Th

eore

tical

CO

P

Fig.4. Graph of Absorption Heat Pump Theoretical COP

5

COP is an important parameter in refrigeration/heat pump systems that can

be viewed “equivalent” to efficiency. It shows the ratio between the desired output (in

this case QA) and the required input (QG+QE). In Fig.4, for the desired TA 120°C

(393K), 160°C (433K) and 200°C (473K), the AHP will have the theoretical COP of

0.57, 0.42, and 0.35 respectively. However, for the case of actual system, the AHP

will only reach COP of 0.45, 0.3, and 0.225. Consequently, if the desired generated

steam energy in Absorber (QA) is 130.97 kJ, the heat input energy required (QG+QE)

will be 229.77 kJ, 311.83 kJ and 374.2 kJ respectively for the theoretical COP value.

For the actual COP, it will be 291.04 kJ, 436.56 kJ and 582.08 kJ. For convenience,

these AHP system data were summarized in Table 1.

Table 1: Detailed Data of the Absorption Heat Pump System

Number of Heat Up Step 1 2 3

Source of Thermal Energy

Warm H2O (entrance) (°C) 90 90 90

Warm H2O (exit) (°C) 85 85 85

(Solution in Generator) (°C) 80 80 80

(Refrigerant in Evaporator) (°C) 80 80 80

Source of Cooling

Cooling H2O (entrance) (°C) 32 32 32

Cooling H2O (exit) (°C) 36 36 36

(Refrigerant in Condenser) (°C) 37 37 37

Generated Steam Temperature in Absorber (exit) (°C) 120 160 200

Theoretical COP 0.57 0.42 0.35

Actual COP 0.45 0.3 0.225

Generated Steam Energy (in Absorber) (exit) (kJ) 130.97 130.97 130.97

Warm Water Energy Required (Theoretical) (kJ) 229.77 311.83 374.20

Warm Water Energy Required (Actual) (kJ) 291.04 436.56 582.08

6

2.2. Methanol Steam Reforming (MSR)

MSR is an endothermic reaction with chemical reaction formula:

)(2)(2)(2)(3 3 ggll HCOOHOHCH +→+

ΔH°MSR = 130.97 kJ/mol CH3OH

ΔG°MSR = 9.18 kJ/mol CH3OH. (4)

These enthalpy and Gibbs-energy changes can be calculated from the enthalpy of

formation difference (ΔHf°) between the product and reactant sides of the reaction.

The initial state of the reactants and final state of the products are considered in

Standard Reference State (25°C, 1 atm) with the ambient temperature and pressure

in that state as well (denoted by superscript ° ). This ΔH°MSR, in fact, can also be

calculated from the difference of enthalpy of combustion (ΔHC°) between 1 mole of

methanol and 3 moles of hydrogen. The same case could be applied to ΔG°MSR as

well, shown by Table 2.

Table 2: Enthalpy and Gibbs Energy of Combustion at 25°C, 1 atm

ΔHC° ΔGC°

Methanol -726.52 kJ/mol -702.36 kJ/mol

Hydrogen -285.83 kJ/mol -237.18 kJ/mol

From reaction (4), ΔH°MSR and ΔG°MSR themselves imply the theoretical

amount of energy and Gibbs-energy (exergy) of the heat required to enable the

endothermic MSR reaction.

Therefore, this endothermic heat required has the value of exergy rate (ε),

which is defined as:

HG

ΔΔ

=ε , (5)

about 0.07 (7%). Based on the Exergy Rate (ε) – Temperature Equation:

7

0

00 )/ln(1TT

TTT−

−=ε , (6)

with T0 as the ambient temperature (25°C), the temperature level of the heat input

required for MSR is found to be about 344 K (71°C) for the theoretical/ideal condition

(see Appendix A). It is the lowest compared to steam reforming temperature of other

hydrocarbons as shown in Table 3. By this MSR process also, the exergy rate of the

waste heat can be greatly enhanced as shown by Fig.5.

Table 3: Exergy Rate and Theoretical Temperature of Various Hydrocarbon Steam Reforming

Reactions

Reaction Exergy rate of the heat (%) Temperature (°C)

CH3OH + H2O → CO2 + 3H2 (methanol) 7.0 71

CH3OCH3 + 3H2O → 2CO2 + 6H2 (DME) 14.0 127

C2H5OH + 3H2O → 2CO2 + 6H2 (ethanol) 30.4 319

C2H6 + 4H2O → 2CO2 + 7H2 (ethane) 43.8 587

CH4 + 2H2O → CO2 + 4H2 (methane) 51.6 833

Exergy rate (%)

Thermal energy

Temperature (K)

9.18130.97

702.36726.52

711.54857.49

Exergy rate (%)

Thermal energy

Temperature (K)

9.18130.97

702.36726.52

711.54857.49

Fig.5. Waste Heat Exergy Rate Enhancement by MSR

8

2.3. Fuel Cell (FC)

Basic reactions that occur in FC can be viewed

Anode: H2 → 2H+ + 2e-, (7)

Cathode: ½O2 + 2H+ + 2e- → H2O, (8)

where the overall reaction can be written as:

H2 + ½O2 → H2O(l) (HHV)

ΔH°FC = -285.83 kJ/mol

ΔG°FC = -237.18 kJ/mol. (9)

The reactions in FC as well as MSR will be viewed in High Heating Value (HHV)

since the initial state of reactants and final state of products are in equilibrium with

ambient state, where this is closely related to the concept of exergy.

Therefore, based on HHV, the maximum theoretical efficiency of FC is

%83/ =ΔΔ= °°FCFCFC HGη . (10)

Nevertheless, this value certainly can’t be reached in actual system regarding the

irreversibility, potential and other losses. Hence, in particular for the FC case, the

reasonable %50=FCη will be used in this calculation.

9

2.4. Integrated System of AHP, MSR, and FC

AHP

FC

CH3OH + H2O CO2 + 3H2

Wpump

QA

QG + QE

ΔHC° = 726.52 kJ/molΔGC° = 702.36 kJ/mol

3 mol H2 : ΔHC° = 857.49 kJ3 mol H2 : ΔGC° = 711.54 kJ

electricity Energy = 428.74 kJExergy = 428.74 kJ

ΔH = 130.97 kJ/mol CH3OHΔG = 9.18 kJ/mol CH3OH

+ Qloss

COPactual =0.57 0.42 0.35

120ºC 160ºC 200ºC0.45 0.3 0.225

COPtheoretical =

229.77 kJ 374.20 kJ291.04 kJ

311.83 kJ436.56 kJ 582.08 kJ

(6 kJ)

If ηfc = 50%

AHPAHP

FCFC

CH3OH + H2O CO2 + 3H2

Wpump

QA

QG + QE

ΔHC° = 726.52 kJ/molΔGC° = 702.36 kJ/mol

3 mol H2 : ΔHC° = 857.49 kJ3 mol H2 : ΔGC° = 711.54 kJ

electricity Energy = 428.74 kJExergy = 428.74 kJEnergy = 428.74 kJExergy = 428.74 kJ

ΔH = 130.97 kJ/mol CH3OHΔG = 9.18 kJ/mol CH3OH

+ Qloss

COPactual =0.57 0.42 0.35

120ºC 160ºC 200ºC0.45 0.3 0.225

COPtheoretical =COPactual =

0.57 0.42 0.35

120ºC 160ºC 200ºC0.45 0.3 0.225

COPtheoretical =COPactual =

0.57 0.42 0.35

120ºC 160ºC 200ºC0.45 0.3 0.225

COPtheoretical =

229.77 kJ 374.20 kJ291.04 kJ

311.83 kJ436.56 kJ 582.08 kJ

229.77 kJ 374.20 kJ291.04 kJ

311.83 kJ436.56 kJ 582.08 kJ

229.77 kJ 374.20 kJ291.04 kJ

311.83 kJ436.56 kJ 582.08 kJ

(6 kJ)

If ηfc = 50%

Fig.6. Integrated System of AHP, MSR, and FC Diagrams

Fig.6 shows the integrated system of the AHP, MSR and FC. Here we see

there’s a change in enthalpy of combustion from one mole of methanol to three

moles of hydrogen. Based on the Law of Energy Conservation, heat input in the

amount of 130.97 kJ must be supplied to the MSR process. This heat input, which

comes from the Absorber of AHP, has the temperature level of 71°C (344K). This

temperature level is enough for the theoretical case, however, in actual system, it

won’t work. The conversion of the methanol to hydrogen will be very low or even

won’t proceed. Therefore, by any means, in order to get a highly-efficient total energy

system, the methanol conversion must reach 100% conversion. Empirically, this can

be achieved by supplying heat input (QA) with temperature level TA ≥ 200°C.

10

However, assume that the attempts to decrease this temperature level of

MSR could succeed, to say 100% conversion of methanol can be reached in TA =

120°C, 160°C or 200°C. Then, to pick up a case, heat input with energy amount of

130.97 kJ with temperature level 200°C will have the Gibbs-energy (exergy) of 27.92

kJ. However, only 9.18 kJ of exergy increase will be accepted by the MSR. Then we

can view this system that 18.74 kJ of exergy is destroyed. Table 4 also shows the

cases for 120°C and 160°C. This implies that if efforts to decrease the 100% MSR

conversion-temperature level could give fruit, less exergy of QA would be destroyed.

Table 4: AHP Heat Output Exergy Content and Exergy Destroyed

Temperature QA (ΔH°MSR) ε Exergy contained Exergy destroyed

120°C 130.97 kJ 0.1319 17.27 kJ 8.09 kJ

160°C 130.97 kJ 0.1752 22.94 kJ 13.76 kJ

200°C 130.97 kJ 0.2132 27.92 kJ 18.74 kJ

Meanwhile, the energy contained in three moles of hydrogen is transferred to

the FC. Since the efficiency of the FC with respect to energy is 50%, thus 428.74 kJ

of electricity energy will be produced. The exergy of this produced electricity is also

428.74 kJ since electricity has the exergy rate of 100%.

The work required to drive the liquid pumps (Wpump) in AHP is considered

about 6 kW for the actual system.

2.5. Hydrogen Production System

For the case of hydrogen production, Figure 6 can be viewed in restriction up

to the output of MSR. In other words, the Fuel Cell is excluded from the integrated

system. The calculation for this special case of hydrogen production efficiency will be

presented in section 3.4.

11

CHAPTER 3 RESULTS AND DISCUSSION

Referring to Fig.6 and AHP data in Table 1, the integrated system total

efficiency was calculated for both energy and exergy efficiencies. This energy and

exergy efficiencies calculation will be further divided into several cases, i.e.

theoretical and actual approximation cases as well as thermodynamic-based and

practical-based cases.

3.1. Energy Efficiency Calculation

a. Theoretical/Ideal Thermodynamic-based Total Energy Efficiency

Theoretical/Ideal case here means the values of energy used in the

calculation were the theoretical ones where the COP of AHP used were the

theoretical COP and energy content of methanol was the theoretical value as well.

“Thermodynamic-based” means that the waste heat input energy to the AHP was

included in calculation. Thus, the Theoretical/Ideal Thermodynamic-based Total

Energy Efficiency could be written as:

energyinputheatAHPtotalenergyOHCHproducedenergyyelectricit

totalen +=

3

1,η

)/97.130(52.72674.428

AHPCOPkJkJkJ

+= . (11)

For the theoretical COPAHP values of 0.57 (120°C), 0.42 (160°C), 0.35 (200°C); the

total energy efficiency will be 44.83%, 41.29%, 38.95% respectively. If work required

for liquid pumps (Wpump) would be included in the denominator of Eq. (11), the total

energy efficiency will become 44.55%, 41.05% and 38.73%. We can see that only

less than 1% decrease of efficiency occurred. This is why in many cases of AHP

efficiency calculation, the work required to drive the pumps could be neglected.

12

b. Theoretical/Ideal Practical-based Total Energy Efficiency.

Since the waste heat input (QG+QE) to the AHP was usually discarded unless

it is used in this system, we could practically exclude it in the calculation. This will be

named the “Practical-based” and thus the Theoretical/Ideal Practical-based Total

Energy Efficiency will be:

pumptotalen WenergyOHCH

producedenergyyelectricit+

=3

2,η %52.58

652.72674.428

=+

=kJkJ

kJ . (12)

c. Actual-Approximation Thermodynamic-based Total Energy Efficiency

In actual system, however, irreversibility and energy losses will unavoidably

occur. Significant losses in AHP such as heat losses in Heat Exchanger as well as

heat losses in the MSR reactor should be taken into consideration. Therefore, the

COP values of actual AHP system will be used for this case calculation. Wpump

required in AHP must be included as well. Besides, assumption of 20% inefficiency

with respect to methanol energy in the MSR process will be used. This means that

145.30 kJ of heat loss occurred in the MSR reactor and hence the number of moles

of methanol supplied must be increased to compensate this heat loss. In other words,

871.82 kJ of methanol input energy needs to be supplied to the MSR process. This

equals the energy of 1.2 moles of methanol.

Therefore, this actual-approximation thermodynamic-based total energy

efficiency could be written as:

pumptotalen WenergyinputheatAHPtotalenergyOHCH

producedenergyyelectricit++

=3

3,η

kJCOPkJkJ

kJ

actualAHP 6)/97.130(82.87174.428

, ++= . (13)

For the actual COPAHP values of 0.45 (120°C), 0.3 (160°C), 0.225 (200°C); the total

energy efficiency will be 36.68%, 32.61% and 29.36% respectively.

13

d. Actual-Approximation Practical-based Total Energy Efficiency

Meanwhile, for the practical case, the actual-approximation practical-based

total energy efficiency will be:

pumptotalen WenergyOHCH

producedenergyyelectricit+

=3

4,η %84.48

682.87174.428

=+

=kJkJ

kJ . (14)

3.2. Exergy Efficiency Calculation

The exergy efficiency, similarly, will be calculated in previously-defined cases

as in energy efficiency calculation.

a. Theoretical/Ideal Thermodynamic-based Total Exergy Efficiency

In this case, the total exergy efficiency could be written as:

exergyinputheatAHPtotalexergyOHCHproducedexergyyelectricit

totalex +=

3

1,η

)/97.130(36.70274.428

80@ AHPC COPkJkJkJ

°+=

ε, (15)

where the exergy rate of the 80°C heat input is 0.0822. For the theoretical COPAHP

values of 0.57 (120°C), 0.42 (160°C), 0.35 (200°C); the total exergy efficiency will be

59.44%, 58.89%, 58.48% respectively. If the exergy of the Wpump would be included in

the denominator of Eq. (15), the total exergy efficiency will become 58.95%, 58.41%

and 58.00%. Still, relatively small efficiency decrease (less than 1%) occurred, even

in the exergy calculation case.

b. Theoretical/Ideal Practical-based Total Exergy Efficiency

Here, the exergy of the AHP waste heat input was excluded and the total

exergy efficiency for this theoretical practical-based will become

pumptotalex WexergyOHCH

producedexergyyelectricit+

=3

2,η %52.60

636.70274.428

=+

=kJkJ

kJ . (16)

14

c. Actual-Approximation Thermodynamic-based Total Exergy Efficiency

With the same assumptions as in the energy efficiency calculation, the actual-

approximation thermodynamic-based total exergy efficiency could be written as:

pumptotalex WexergyinputheatAHPtotalexergyOHCH

producedexergyyelectricit++

=3

3,η

kJCOPkJkJ

kJ

actualAHP 6)/97.130(0822.078.84274.428

, ++= , (17)

where the exergy rate (ε) of methanol is 96.67%. For the actual COPAHP values of

0.45 (120°C), 0.3 (160°C), 0.225 (200°C), the total exergy efficiency for this case will

be 49.12%, 48.46% and 47.81% respectively.

d. Actual-Approximation Practical-based Total Exergy Efficiency

For the practical case, the actual-approximation total exergy efficiency will be:

pumptotalex WexergyOHCH

producedexergyyelectricit+

=3

4,η %51.50

678.84274.428

=+

=kJkJ

kJ . (18)

3.3. Alternative Actual-Approximation Cases

The previous actual-approximation cases, i.e. section 3.1.c, 3.1.d, 3.2.c, and

3.2.d determined that heat losses in MSR reactor could be compensated by

supplying more moles of methanol. However, since the moles of hydrogen produced

remain constant, there will be remaining unconverted methanol. From the view-point

of energy and exergy enhancement, the initial intention of increasing 18% of energy

and 1.3% of exergy by converting methanol to hydrogen seems to be no more

meaningful. Therefore, the remaining unconverted moles of methanol should be

pressed as low as possible and by engineering technique, the heat losses of the

MSR reactor could be compensated by supplying more heat input (QA) to the system.

15

Thus, the production of 3 moles of hydrogen will only require about 1 mole of

methanol (not 1.2 moles as before); which means less unconverted methanol will

occur. Moreover, the waste heat available is abundant and thus it should not be

regarded as limiting reactant in the MSR process.

Consequently, the efficiency of the case 3.1.c, 3.1.d, 3.2.c, and 3.2.d can be

improved as follow:

1. Energy Case

c. Alternative Actual-Approximation Thermodynamic-based Total Energy Efficiency

pump

alttotalen WenergyinputheatAHPtotalenergyOHCH

producedenergyyelectricit++

=3

,3,η

kJCOPkJkJ

kJ

actualAHP 6)/27.276(52.72674.428

, ++= . (19)

Here we could see that the amount of total heat input in AHP increases since

it substitutes the compensation that otherwise supplied by methanol (145.3 kJ). Thus,

for the actual COP of 0.45, 0.3, and 0.225; the total energy efficiency will become

31.84%, 25.93% and 21.87% respectively.

d. Alternative Actual-Approximation Practical-based Total Energy Efficiency

For the alternative actual-approximation thermodynamic-based case above,

the efficiencies seem to decrease compared to 3.1.c. This is certainly true since

bigger amount of waste heat energy is required to substitute the compensation

energy provided by methanol previously. However, since the waste heat is free and

abundant, for the practical-based case, it can be excluded in the calculation and the

efficiency will increase significantly as follow:

pump

alttotalen WenergyOHCH

producedenergyyelectricit+

=3

,4,η %52.58

652.72674.428

=+

=kJkJ

kJ . (20)

16

This is exactly the same as the Theoretical/Ideal Practical-based Total Energy

Efficiency (Section 3.1.b).

2. Exergy Case

c. Alternative Actual-approximation Thermodynamic-based Total Exergy Efficiency

pump

alttotalex WexergyinputheatAHPtotalexergyOHCH

producedexergyyelectricit++

=3

,3,η

kJCOPkJkJ

kJ

actualAHP 6)/27.276(0822.036.70274.428

, ++= . (21)

For the actual COP of 0.45, 0.3, and 0.225; the exergy efficiency will become 56.50%,

54.68% and 52.97% respectively. It is increased compared to 3.2.c.

d. Alternative Actual-approximation Practical-based Total Exergy Efficiency

pump

alttotalex WexergyOHCH

producedexergyyelectricit+

=3

,4,η %52.60

636.70274.428

=+

=kJkJ

kJ (22)

shows a significantly high increase in efficiency result which equals case 3.2.b.

3.4. Hydrogen Production Efficiency

1. Energy Case

In the same way and cases as previous total efficiency calculation, for the

case if the output is hydrogen, then we shall get following results:

a. Thermodynamic-based Efficiency

pumpHen WenergyinputheatAHPtotalenergyOHCH

producedenergyHydrogen++

=3

1, 2

η (23)

= 89.10%, 82.10%, 77.48% (theoretical)

= 73.36%, 65.23%, 58.73% (actual-approximation),

17

b. Practical-based Efficiency

pumpHen WenergyOHCH

producedenergyHydrogen+

=3

2, 2

η (24)

= 117% (theoretical)

= 97.68% (actual-approximation).

For hydrogen production, the actual-approximation cases above assume that there’s

heat loss in MSR that counts for 20% of methanol energy and compensated by

adding more methanol input.

2. Exergy Case

a. Thermodynamic-based Efficiency

pumpHex WexergyinputheatAHPtotalexergyOHCH

producedexergyHydrogen++

=3

1, 2

η (25)

= 97.84%, 96.94%, 96.26% (theoretical)

= 81.53%, 80.43%, 79.35% (actual-approximation),

b. Practical-based Efficiency

pumpHex WexergyOHCH

producedexergyHydrogen+

=3

2, 2

η (26)

= 100.44% (theoretical)

= 83.83% (actual-approximation).

3.5. Exergy Rate Diagram

These theoretical as well as actual-approximation calculations of energy and

exergy efficiencies can be visualized by the exergy rate diagrams as shown in Fig.7.

These exergy rate diagrams show the energy-conversion processes starting from the

18

AHP to FC. They also describe the enhancement as well as decrease of exergy rate

values of various kinds of energy quantities.

Exe

rgy

Rat

e (%

) Tem

perature (K)

66

0457.1147.84

582.08

00145.30

842.78871.82

130.9727.92

857.49711.54

428.74428.74

428.75Qwaste,FC

QA

QG+QE

CH3OH

Qwaste,MSR

electricity

QC+Qetc

3H2

Wpump

Actual-Approximation Exergy Rate Diagramprocess

Exe

rgy

Rat

e (%

) Tem

perature (K)

66

243.2330.75374.2

0

27.92130.97

428.75

428.74428.74

711.54857.49

702.36726.52

0

Wpump

QG+QE

QA

QC+Qetc

CH3OH

3H2

electricity

Qwaste,FC

Theoretical/Ideal Exergy Rate Diagramprocess

Exe

rgy

Rat

e (%

) Tem

perature (K)

66

0457.1147.84

582.08

00145.30

842.78871.82

130.9727.92

857.49711.54

428.74428.74

428.75Qwaste,FC

QA

QG+QE

CH3OH

Qwaste,MSR

electricity

QC+Qetc

3H2

Wpump

Actual-Approximation Exergy Rate Diagramprocess

Exe

rgy

Rat

e (%

) Tem

perature (K)

66

0457.1147.84

582.08

00145.30

842.78871.82

130.9727.92

857.49711.54

428.74428.74

428.75Qwaste,FC

QA

QG+QE

CH3OH

Qwaste,MSR

electricity

QC+Qetc

3H2

Wpump

Actual-Approximation Exergy Rate Diagramprocessprocess

Exe

rgy

Rat

e (%

) Tem

perature (K)

66

243.2330.75374.2

0

27.92130.97

428.75

428.74428.74

711.54857.49

702.36726.52

0

Wpump

QG+QE

QA

QC+Qetc

CH3OH

3H2

electricity

Qwaste,FC

Theoretical/Ideal Exergy Rate Diagramprocess

Exe

rgy

Rat

e (%

) Tem

perature (K)

66

243.2330.75374.2

0

27.92130.97

428.75

428.74428.74

711.54857.49

702.36726.52

0

Wpump

QG+QE

QA

QC+Qetc

CH3OH

3H2

electricity

Qwaste,FC

Theoretical/Ideal Exergy Rate Diagramprocessprocess

Fig.7. Exergy Rate Diagram of the Integrated System

3.6. Additional Discussion

All the energy and exergy efficiencies were summarized in Table 5 and Table

6. For comparison, currently one of the best power plant combustion system that

uses the Advanced Combined Cycle (ACC), has the energy efficiency of 54% based

on LHV (Low Heating Value) [20]. Therefore, the efficiency of this power plant, on

HHV (High Heating Value) based, is about 48.66% where its exergy efficiency is

52.97% as shown in Fig.8. The fuel, natural gas, is a fossil-fuel that will eventually be

depleted. Even though the fuel for the power plant is natural gas (methane), if

methanol is used instead, the power plant efficiency will be relatively similar [21,22].

19

Table 5: Energy and Exergy Efficiency Calculation Results of the Integrated System of AHP,

MSR, and FC

Total Energy Efficiency (Theoretical Thermodynamic-based) 44.55% 41.05% 38.73%

Total Energy Efficiency (Theoretical Practical-based) 58.52% 58.52% 58.52%

Total Energy Efficiency (Actual-approximation Thermodynamic-based) 36.68% 32.61% 29.36%

Total Energy Efficiency (Actual-approximation Practical-based) 48.84% 48.84% 48.84%

Total Energy Efficiency (Alt Actual-approx Thermodynamic-based) 31.84% 25.93% 21.87%

Total Energy Efficiency (Alt Actual-approx Practical-based) 58.52% 58.52% 58.52%

Total Exergy Efficiency (Theoretical Thermodynamic-based) 58.95% 58.41% 58.00%

Total Exergy Efficiency (Theoretical Practical-based) 60.52% 60.52% 60.52%

Total Exergy Efficiency (Actual-approximation Thermodynamic-based) 49.12% 48.46% 47.81%

Total Exergy Efficiency (Actual-approximation Practical-based) 50.51% 50.51% 50.51%

Total Exergy Efficiency (Alt Actual-approx Thermodynamic-based) 56.50% 54.68% 52.97%

Total Exergy Efficiency (Alt Actual-approx Practical-based) 60.52% 60.52% 60.52%

Table 6: Hydrogen Production Energy and Exergy Efficiency Calculation Results

Energy Efficiency (Theoretical Thermodynamic-based) 89.10% 82.10% 77.48%

Energy Efficiency (Theoretical Practical-based) 117% 117% 117%

Energy Efficiency (Actual-approximation Thermodynamic-based) 73.36% 65.23% 58.73%

Energy Efficiency (Actual-approximation Practical-based) 97.68% 97.68% 97.68%

Exergy Efficiency (Theoretical Thermodynamic-based) 97.84% 96.94% 96.26%

Exergy Efficiency (Theoretical Practical-based) 100.44% 100.44% 100.44%

Exergy Efficiency (Actual-approximation Thermodynamic-based) 81.53% 80.43% 79.35%

Exergy Efficiency (Actual-approximation Practical-based) 83.83% 83.83% 83.83%

CH4 Q Electricitycombustion boiler, gas+steam turbines, generator

LHV802.31 kJ/mol 433.24 kJ/mol CH4

54%

433.24 kJ/mol CH4890.33 kJ/molHHV= 48.66%

433.24 kJ/mol CH4817.85 kJ/mol (exergy) (exergy)

CH4 Q Electricitycombustion boiler, gas+steam turbines, generator

LHV802.31 kJ/mol 433.24 kJ/mol CH4

54%

433.24 kJ/mol CH4890.33 kJ/molHHV= 48.66%

433.24 kJ/mol CH4817.85 kJ/mol (exergy) (exergy)

Fig.8. Power Plant Combustion System and Efficiency Analysis

20

However, this integrated system of AHP, MSR and FC is not without problem.

The feedstock to produce methanol is an important issue. Currently, methanol is

mostly produced from fossil-fuel as well, since it is economically the most favorable.

Therefore, it is necessary for further research to find alternative/renewable resources

to produce methanol, as have been done by several research [23,24]. Biomass,

agricultural, industrial and other wastes have potency to produce huge amount of

methanol.

This integrated system still has many spaces for efficiency improvement.

Higher temperature of waste heat input in AHP system (80°C was used in this

calculation), more efficient and higher COP of the AHP, higher efficiency of MSR

reactor and certainly higher efficiency of FC will further yield significant increase in

the total integrated system efficiency.

In particular, hydrogen production cases show high efficiencies due to the

principle of waste heat energy recovery/recycling. Here, the low quality waste heat

which is difficult to reuse and usually discarded, has been enhanced by the AHP

system. This enhanced waste heat is then absorbed by the MSR process to be

stored into the high quality chemical energy, i.e. the hydrogen energy. This hydrogen

will be further utilized through various hydrogen-related technologies to support the

Hydrogen Economy scheme in the future.

21

CHAPTER 4 CONCLUSION

With the specified conditions and assumptions, for the MSR temperature of

200°C, the integrated system of AHP, MSR and FC has the energy efficiency of

38.73% and 58.52% for the theoretical thermodynamic-based and practical-based

cases; as well as 29.36% and 48.84% for the actual-approximation thermodynamic

and practical-based cases, respectively. In term of exergy, it will be 58%, 60.52%,

47.81%, and 50.51% for the respective cases.

Meanwhile, for the hydrogen production efficiency and MSR temperature of

200°C, the thermodynamic-based case will yield 77.48% and 58.73% for theoretical

and actual-approximation cases respectively. For practical-based case, it will be

117% (theoretical) and 97.68% (actual-approximation). In term of exergy, the

efficiency will be 96.26% and 79.35% for thermodynamic-based; 100.44% and

83.83% for practical-based respectively.

The efficiency of actual-approximation cases can be further improved to

approach the theoretical cases by supplying more heat input to compensate the heat

loss in the MSR. This is especially significant for the practical-based cases. Moreover,

spaces for efficiency improvement in parts of this integrated system are still available.

If this high efficiency integrated system that utilizes the concept of exergy

enhancement can be combined with the potential methanol production from

renewable resources (including wasted material), it is not impossible that this

integrated system could, one day, become a high-efficient and sustainable energy

system.

22

REFERENCES

[1] Okazaki K, Akai M. Countermeasures to global warming by integration of coal, hydrogen

and CO2 sequestration, and system evaluation. The 36th Clean Coal Seminar, 2004.

p.17-46.

[2] Okazaki K. Significance of hydrogen energy introduction and technology prospects.

PETROTECH 2002; 25(8): 627-632.

[3] Kozawa Y, Okazaki K. Total energy system based on fuel cells. Chemical Engineering

2001; 65(10): 530-533.

[4] Okazaki K. Clean and efficient coal technology integrated with hydrogen energy systems.

9th Asian Hydrogen Energy Conference 2007, plenary lecture, Tokyo, Japan. p. 17-30.

[5] Mathieu P. Toward the hydrogen era using near-zero CO2 emissions energy systems.

Energy 2004; 29: 1993-2002.

[6] Yoshida K. Prospects and challenges of hydrogen energy system. The 2nd COE-INEN

International Workshop on “Toward Hydrogen Economy” 2006, Tokyo, Japan.

[7] Okazaki K. Exergy enhancement and effective use of low-to-medium-temperature waste

heat with an example of biomass hydrogenation. Hydrogen Energy System Society of

Japan (HESS) 2004; 29(1): 18-25.

[8] Sumitomo H, Kado S, Nozaki T, Fushinobu K, Okazaki K. Exergy enhancement of low

temperature waste heat by methanol steam reforming for hydrogen production. 8th Asian

Hydrogen Energy Conference 2005, Beijing, China.

[9] Wild PJd, Verhaak MJFM. Catalytic production of hydrogen from methanol. Catalysis

Today 2000; 60: 3-10.

[10] Lin YM, Rei MH. Study on the hydrogen production from methanol steam reforming in

supported palladium membrane reactor. Catalysis Today 2001; 67: 77-84.

[11] Segal SR, Anderson KB, Carrado KA, Marshall CL. Low temperature steam reforming of

methanol over layered double hydroxide-derived catalysts. Applied Catalysis A: General

2002; 231: 215-226.

23

[12] Iwasa N, Nomura W, Mayanagi T, Fujita S, Arai M, Takezawa N. Hydrogen production by

steam reforming of methanol. Journal of Chemical Engineering of Japan 2004; 37(2): 286-

293.

[13] Basile A, Gallucci F, Paturzo L. A dense Pd/Ag membrane reactor for methanol steam

reforming: Experimental study. Catalysis Today 2005; 104: 244-250.

[14] Steimle F. Heat pumps for waste heat recovery and economical use of energy. ICCR

1998, Hangzhou, China. Soc des Ingenieurs de l’ Automobile. p. 209-215.

[15] Ma X, Chen J, Li S, Sha Q, Liang A, Li W, Zhang J, Zheng G, Feng Z. Application of

absorption heat transformer to recover waste heat from a synthetic rubber plant. Applied

Thermal Engineering 2003; 23: 797-806.

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pulp and paper industry for increased efficiency and reduction of greenhouse gas

emissions. PAPTAC 2004, Montreal, Canada, vol. B. p. 191-195.

[17] Padilla DCA, Rodriguez LG. Application of absorption heat pump to multi-effect

distillation: a case study of solar desalination. Desalination 2007; 212: 294-302.

[18] Inoue N, Iizuka H, Ninomiya Y, Watanabe K, Aoki T. COP evaluation for advanced

ammonia-based absorption cycles. International Absorption Heat Pump Conference 1994,

New Orleans, USA. ASME, 1994. p. 1-6.

[19] Inoue N, Irie K, Fukusumi Y. Analysis on static characteristics of heat transformer (昇温型

吸収ヒートポンプの特性解析). Trans. of the JSRAE 2005; 22 (2): 173-184. (in Japanese)

[20] Tokyo Electric Power Company (TEPCO). Highly efficient and Environmentally-friendly

Yokohama Thermal Power Station. TEPCO Pamphlet 2006. p. 5-8.

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test starts for a power source at peak demand. Japanese High-Technology Monitor, April 5

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methanol gas turbine power plants. Houston, TX: Exxon Chemical Patents Inc, 1999. See

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[23] Nichols RJ. The methanol story: A sustainable fuel for the future. Journal of Scientific &

Industrial Research 2003; 62: 97-105.

[24] Ekbom T. High efficient motor fuel production from biomass via black liquor gasification.

ISAF XV 2005, San Diego, USA.

25

APPENDIX A Derivation of Exergy Rate - Temperature Equation

Exergy Rate (ε) is defined as

HG

ΔΔ

=ε . (A1)

From the thermodynamic relations, the formula can be derived as:

HG

ΔΔ

=εH

STHΔ

Δ−Δ=

o

oo

HHSST

−−

−=)(1

TCTTCT

p

opo

Δ−=

)/ln(1

o

oo

TTTTT

−−=

)/ln(1 , (A2)

where ΔG = Gibbs energy changes

ΔH = Enthalpy changes

ΔS = Entropy changes

T = Temperature of the heat/substance/system

To = Temperature of environment (25°C as standard reference state)

Cp = Specific heat at constant pressure

At the constant pressure, P = Po = constant,

ΔH = CpΔT, (A3)

and ΔS = Cp ln TTo

. (A4)

Substituting To = 298 K (25°C) to Eq. (A2) with temperature of the system (T) as the

changing variable, the graph of the exergy rate (ε) can be viewed as in Fig. A1.

26

the exergy rate of thermal energy

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 200 400 600 800 1000 1200 1400 1600 1800 2000temp. [K]

exer

gy r

ate

Fig. A1. The Graph of Exergy Rate as a Function of Temperature

27

APPENDIX B Proof of Entropy-Balance Derived COP Formula

From Fig. 3, Eq. (1), and Eq. (2) in Chapter 2 of this thesis, we got Eq. (3) as follow

))((D

CD

CA

A

EG

A

TTT

TTT

QQQCOP −

−=

+= . (Eq.3)

Heat Balance Equation: CAGE QQQQ +=+ (Eq.1)

Entropy Balance Equation: D

EG

A

A

C

C

TQQ

TQ

TQ +

=+ (Eq.2)

Since the temperature of the Generator (TG) and Evaporator (TE) are equal, we can

write TG = TE = TD. Substituting Eq. (1) into Eq. (2), then we get

D

CA

A

A

C

C

TQQ

TQ

TQ +

=+ , (B1)

⇔ CAAA

DC

C

D QQQTTQ

TT

+=+ , (B2)

⇔ CC

DA

A

D QTTQ

TT

⎟⎟⎠

⎞⎜⎜⎝

⎛−=⎟⎟

⎠

⎞⎜⎜⎝

⎛− 11 , (B3)

⇔ ( )( )DCA

ADC

A

C

TTTTTT

QQ

−−

= . (B4)

The Coefficient of Performance (COP) of the Absorption Heat Pump (AHP), which is

to be derived, could be expressed as follow:

A

CCA

A

EG

A

QQQQ

QQQ

QCOP+

=+

=+

=1

1. (B5)

Substituting Eq. (B4) into Eq. (B5), the COP could be written as

28

( ))()(

)()( ACD

DCA

ADCDCA

DCA

TTTTTT

TTTTTTTTT

COP−−

=−+−

−= , (B6)

which is, as a matter of fact, equal to Eq. (3).

Therefore, besides from the thermodynamic analysis of Heat Engine – Heat Pump

Combination, the COP of AHP could also be derived from the Heat Balance and

Entropy Balance Combination as shown above.

29

ABOUT THE AUTHOR

Willy Yanto Wijaya was born on April 1st, 1985 in

Tebingtinggi, a small town in the north-eastern part of North

Sumatera. He spent his kindergarten, elementary and junior high

school in F. Tandean, a school in that town. He had a happy childhood. During his

elementary school, his curiosity in science grew so wildly. He even already tried to

read some biology, astronomy or physics books of Junior or Senior High School level.

He usually got the 1st rank in class, sometimes the 2nd rank, this happened even until

his high school periods.

Despite his excellent achievements, in the Junior High, he started losing

interest in studying the school lessons. He was haunted by various philosophies and

own thoughts, such as about the mystery of life; what happens after death; what is

actually the meaning and purpose of life; is the universe limitless; am I the same as

others? does God really exist? and many other deep thoughts. This was a time of

heavy mental sufferings for him; a very critical time which, if he couldn’t bear

anymore, could destroy his rational mind.

Fortunately, he could struggle to maintain his mind. Even though his being

unable to answer all those questions, he began accepting his weakness and limited

knowledge. After graduated from Junior High School, he moved from Sumatera

Island to Java Island to continue his study in SMUN1 Serang, Banten Province. Here,

his interest in math and science began to grow again. Even though only until the

province-level, he ever participated in Mathematics and Physics Olympiad.

Nevertheless, he made many great achievements during this period such as the

winner of Grand Final “Indosat Galileo”, a scientific competition programme

broadcasted by SCTV (an Indonesian TV Station); Top Ten in English Speech

30

Competition held by FE Trisakti; 1st winner in National Youth Competition in

Buddhism held in Batam Island; as well as finalist or semifinalist in various

math/science competitions.

His blooming curiosity had motivated him to pursue his further study in

Physics in Institut Teknologi Bandung (ITB). Living in Bandung for the first time, he

had to try to adapt to the cold weather compared to the extremely hot weather of

Serang. Again, pushed by his curiosity, he spent his first year in ITB exploring many

corners of Bandung City by walking for hours. He spent three years studying in ITB

before leaving for Japan to do his final project research in EPL (Energy Phenomena

Lab), Tokyo Institute of Technology. Beforehand, indeed, he already had great

interest in the problems of energy, as shown by his involvement as the coordinator of

Energy Conversion Division of KriM Advanced Tech (2005-2006). He had also ever

become the assistant of experiments in LFD, Lab Fislan, Lab Elka, as well as in UPK.

Leaving for Japan for YSEP (Young Scientist Exchange Program) was like an

incredible dream for him. Here, he got so many unique experiences: skiing amidst

the beautiful white snow; picnicking under the falling buds of Sakura; climbing to the

peak of Mt. Fuji; being naked in the onsen (mineral water hot bath); watching the

hanabi (firework) festival during the mid-summer; visiting various temples, museums,

and Tokyo Disneyland; tasting some kinds of autumn fruits and delicious sushi; and

many other interesting experiences.

In this one year period, he also took several classes including Japanese

Language classes and tours to factories within the Tokyo area. He also succeeded in

publishing some of photos he took in the Japan Times, the biggest English-language

newspaper in Japan.

After returning to Indonesia, he took one more semester to complete his study

in ITB and got the cum laude predicate.

31

Besides the academic activities, he was also active in organizations, i.e. KMB

Dhammanano ITB and Pemuda Vihara Vimala Dharma (PVVD). He was the

coordinator of Penerbitan PVVD (2005-2006) and was selected as the chairman of

PVVD (2006-2007). He also loved the activity of writing. He was a regular contributor/

writer to BVD magz and he also wrote occasionally for Bhadra Bodhi magz of KMB

ITB.

He also involved in translation as well as editing of several books, such as a

book with title “Jangan Ada Dukkha diantara Kita”. Besides his hobby in writing and

reading books, he also loves collecting stamps, money, and various unique items.

He’s fond of stories and folktales, as well as math puzzles. He loved gardening too,

to grow plants and to look after them.

He also had outstanding ability in languages. This was indicated by his

excellence in English, Indonesian, and Hokkianese plus his moderate ability in

Japanese language and Mandarin, as well as his basic knowledge in Malay-Arab

writings and old Pali scripts.

Now he is thinking the next path to step in his life. He hopes to find the

meaning of life and to live a fruitful life.

Willy Yanto Wijaya

His e-mail: willy_yanto_wijaya@yahoo.com

YSEP page: http://www.ryu.titech.ac.jp/~ysep/student/ysepst2006.html

32