Biometamaterials application for solar steam generation device

11 Figure 3.1: Porous Structure and Tube Structure of Fresh Pomelo Peel left and Carbonized Pomelo Peel .... 21 Figure 3.9: Absorption properties of carbonized pomelo peel and fresh pome

VIETNAM NATIONAL UNIVERSITY, HANOI

VIETNAM JAPAN UNIVERSITY

VU TIEN DUNG

BIOMETAMATERIALS APPICATION FOR SOLAR STEAM GENERATION

DEVICES

MASTER'S THESIS

VIETNAM NATIONAL UNIVERSITY, HANOI

VIETNAM JAPAN UNIVERSITY

VU TIEN DUNG

BIOMETAMATERIALS APPICATION FOR SOLAR STEAM GENERATION

DEVICES

MAJOR: NANOTECHNOLOGY CODE: 8440140.11QTD

RESEARCH SUPERVISOR:

Dr PHAM TIEN THANH

Dr BUI NGUYEN QUOC TRINH

Hanoi, 2020

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ACKNOWLEDGMENTS

Firstly, I would like to extend my sincere thanks to Dr Pham Tien Thanh, and Dr Bui Nguyen Quoc Trinh, my supervisors, working for Vietnam Japan University, for their enthusiasm, encouragement, and patient guidance during the preparation of

my master thesis

Moreover, I would also like to express my great appreciation to Prof Dr Kotaro Kajikawa, working for the Tokyo Institute of Technology, who gives me a lot of valuable suggestions and teaches me with the necessary knowledge about the science

I take this chance to acknowledge the support provided by Assoc Prof Dr Do Danh Bich, Dr Nguyen Duc Cuong, Dr Nguyen Viet Hoai, and Mr Nguyen Minh Tuan The advice given by them has been a great help in my research

Finally, I especially wish to thank my mom, my dad, my brother, and friends, who are always by my side, have supported and encouraged me throughout my life My life will be incomplete without them Thanks

Vu Tien Dung Hanoi, 2020

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TABLE OF CONTENTS

Page

ACKNOWLEDGMENTS i

TABLE OF CONTENTS ii

LIST OF FIGURES iii

LIST OF TABLES v

LIST OF ABBREVIATIONS vi

CHAPTER 1: INTRODUCTION 1

1.1 Clean water and Salination Issue + Desalination method 1

1.2 Solar Steam Generation 2

1.2.1 Mechanism of SSG 2

1.2.2 Absorber Material 3

1.2.3 Purpose of this master thesis 5

CHAPTER 2: EXPERIMENTAL METHOD 7

2.1 Carbonized pomelo peel synthesis and characteristics 7

2.1.1 Fabrication procedure 7

2.1.2 Carbonized pomelo peel characteristics 8

2.2 SSG System construction and evaluation 9

2.2.1 Construction of the SSG system 9

2.2.2 SSG system evaluation 9

CHAPTER 3: RESULTS AND DISCUSSION 15

3.1 Carbonized pomelo peel 15

3.1.1 Physical characteristics of carbonized pomelo peel 15

3.1.2 Absorption properties 20

3.1.3 Solar heating behavior of materials under the sunlight 24

3.2 Solar steam generation system ability 27

3.2.1 Vapor steam creation capacity 27

3.2.2 Desalination and purification capacity of the SSG system 33

CHAPTER 4: CONCLUSION 35

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LIST OF FIGURES

Page Figure 1.1: Drought in Vietnam (left), warning of saline intrusion in Ben Tre

province, and Vinh Long province on the television news 2

Figure 2.1: Fresh pomelo (a) and (b), and Fresh pomelo peel (c) 7

Figure 2.2: Pomelo peel and carbonized pomelo peel 8

Figure 2.3: Light absorber and converter and water supply 9

Figure 2.4: System to calculate the evaporation rate in the laboratory 10

Figure 2.5: Mechanism of the system in the real condition 11

Figure 3.1: Porous Structure and Tube Structure of Fresh Pomelo Peel (left) and Carbonized Pomelo Peel 15

Figure 3.2: Changes in structural dimensions before and after carbonization process (a), (b), (c): Fresh Pomelo Peel; (d), (e), (f): Carbonized Pomelo Peel 16

Figure 3.3: Water Capacity Ability of Carbonized Pomelo Peel 17

Figure 3.4: XRD spectrum of Carbonized Pomelo Peel 18

Figure 3.5: Raman Spectrum of Carbonized Pomelo Peel 18

Figure 3.6: FTIR spectra of Fresh Pomelo Peel and Carbonized Pomelo Peel 19

Figure 3.7: Absorption properties of carbonized pomelo peel with 1 hour of annealing time 20

Figure 3.8: Absorption properties of carbonized pomelo peel with 2 and 3 hours of annealing time 21

Figure 3.9: Absorption properties of carbonized pomelo peel and fresh pomelo peel in the UV-Vis-IR region 22

Figure 3.10: Absorption spectrum of carbonized pomelo peel samples before being hydrated and after being hydrated 23

Figure 3.11: Temperature of Fresh Pomelo Peel and Carbonized Pomelo Peel Samples under an artificial sun 24

Figure 3.12: Infrared image of sample carbonized pomelo peel placed under artificial sunlight 25

Figure 3.13: Temperature of Fresh Pomelo Peel and Carbonized Pomelo Peel Samples under some real conditions (a): affected by wind; (b): affected by solar intensity; and (c): affected by cloud 26

Figure 3.14: Vapor steam creation ability under an artificial sun 27

Figure 3.15: Vapor steam creation ability with different conditions of thickness under an artificial sun (a): Mass change within 1 hour; (b): Evaporation Rate within 1 hour; (c) Carbonized pomelo peel’s infrared photos when exposing to the sunlight 28

Figure 3.16: Vapor steam creation capacity under the real condition 30

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Figure 3.17: Vapor steam creation capacity under different power intensity 31Figure 3.18: Vapor steam creation capacity after 30 days 32Figure 3.19: Cation concentration (top), and Anion concentration (bottom) of Sea water and Purified water compared to the Standard of drinking water 33Figure 3.20: Wastewater Purification Application 34

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LIST OF TABLES

Page Table 2.1: Some equipment used in this master thesis 11Table 4.1: The comparison of evaporation rate for each material and its disadvantages 35

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CHAPTER 1: INTRODUCTION

1.1 Clean water and Salination Issue + Desalination method

In the recent time, one of global problem is crisis of the clean water Water is everywhere, but clean water is lacking According to the World Economic Forum

2019, the clean water crisis is one of four global threats that have a great impact on the lives of human beings [21] Moreover, Water Center, University of Twente (2016) showed us that over 65% of the world's population, have to face to the shortage of clean water for at least one month a year as a result of climate change and drought [14] Vietnam is one of the country’s most vulnerable to climate change and is currently facing a serious shortage of freshwater and irrigation due to drought and especially surface intrusion over the years According to Vietnam Disaster Management Authority, in the Mekong Delta, nearly 160,000 households are using polluted water, saline intrusion affects 40% of the fruit land area [19] Figure 1.1 reveals drought and saline intrusion in several provinces in Vietnam The salinization (water with salinity of > 4‰) is alarming, and in some areas the saline instruction occurs 80-100 km from the coast Several predictions affirm that Vietnam's GDP will be reduced by 10% by 2030 because of drought and saline intrusion Therefore, constructing a system to product the clean water from the sea water is expected to be a valuable solution to face with the situation of clean water scarcity

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Figure 1.1: Drought in Vietnam (left), warning of saline intrusion in Ben Tre

province, and Vinh Long province on the television news

To find a solution with this situation, a lot of technologies for producing fresh water from the saline water have been developed and applied, such as distillation, ion exchange, membrane filtration, and so on [4], [7], [18] However, these methods have limitations, such as high cost, high consumption of materials and low performance because of the sea water’s corrosion and salt precipitation Nowadays, technology for producing the clean water from the saline water using solar energy is receiving much attention The potential of this technology is to create an eco-friendly, cheap, high-performance system

1.2 Solar Steam Generation

The solar energy is a kind of green energy which available in the nature Moreover,

it is an endless source of energy for human life However, we have not used the solar energy optimally According to California Institute of Technology, the amount

of sunlight energy that reaches the earth in 1 hour is equal to the total amount of energy that humans use within 1 year [22] In the world, Vietnam is one of the countries with a lot of sunshine hours in a year (around 2000 to 2600 hours/year, equivalent to 6-7 hours/day), which is a huge source of energy coming from the sun This is an extremely good condition, giving Vietnam many advantages when setting

up devices that use solar energy Solar Steam Generation (SSG) is a system that uses solar energy to turn water into steam That steam is passed through a condensation system to obtain the clean water SSG system has many advantages, such as no electricity in use, no CO2 emissions, simplicity, and competitive price With the sunshine hours of 6-7 h/d as in the South of Vietnam, a normal device can produce 15-30 L/h, equivalent to the minimum water demand of a household per day [25]

1.2.1 Mechanism of SSG

A complete SSG system is divided into 3 main components: the light absorber and converter, (2) water supply system, and (3) the clean water collector [23] The principle of the system is the process of converting light energy into thermal energy

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Absorber material receives sunlight and converts that energy into heat energy The surface temperature of the material goes up extremely high The water supply transports the water from the bottom to the surface of the absorber material through

a water transport system (usually a capillary system) A sufficient amount of water when reaching the surface, will exchange heat with the absorber and converter system, to receive energy to transform the state from liquid to vapor Steam is involved in the condensation process by a refrigeration device Finally, clean water

is collected The above process is operated continuously Water is constantly being transferred up to a specified amount so that the absorber layer’s surface temperature

is always at maximum The performance of the system depends on the thermal energy conversion efficiency of the absorber layer In order to achieve the highest photo-thermal conversion efficiency, light absorber materials must have strong absorption in the sunlight range (from 300 nm to 3000 nm) Many categories

photo-of materials have been used for developing light absorbers, such as metal nanoparticles [2], [3], metal oxides [17], polymers [11], [20], semiconductors [6], [26], bio-inspired materials [5], [10], [24], etc The photo-thermal materials have been designed with the porous and capillary structures or bio-inspired structures

1.2.2 Absorber Material

Photo-thermal conversion (PTC) process has classified into 3 main types The first type is PTC based on the plasmonic localized heating of metals There are two main kind of materials that operate on this mechanism, metals nanoparticles and metal oxides Several metals with nanostructures such as gold, silver, and copper have been utilized for absorber layer [1], [8] They exhibit extremely strong absorption due to the resonant effect of free electrons on the surface excited by the electromagnetic of the incident light Yang et al showed SSG system with copper nanoparticles, which is a scalable and eco-friendly system [13] The copper nanoparticles exhibited strong absorption (around 97,7%) in the region of 200 nm to

1300 nm The SSG based on Cu NPs had high efficiency up to 73% at 2 sun (equivalent with P= 2 kW.m-2 ) illumination Naomi et al developed the SSG using SiO2/Au nano-shells particles [15] This material strongly absorbs the light range

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from 500 nm to 1200 nm, leading to the system’s conversion efficiency reached up

to 80% at 1 sun However, the SSG system using these materials has limitations, such as: complicated fabrication procedure, expensive, and so on Constructing this system on an industrial scale is an uneconomical option For the metal oxides, several groups published some initial results in the construction of the SSG system

By using WO2.9 , SSG system manufactured by Wang et al can absorb more than 90% of sunlight [16] PTC efficiency of the system reached over 85%, higher than that of nanoparticles Deng et al constructed the absorber layer by generation Fe3O4nanoparticles on the surface of graphene [17] The temperature of the water contained this material rose to 10000C when exposing to sunlight The photo-thermal materials based on metal oxides had higher light absorbability and greater conversion efficiency than metal nanoparticles Those materials get same limitations of metal nanoparticles

The second type of PTC is non-radiative relaxation of semiconductor Semiconductor materials absorb light to transfer electrons from the valence band to the conduction band At the conduction band, electrons perform non-radiative relaxation before returning to the valence band These relaxation causes the temperature of the material to heat up, making the evaporation process faster Hu et

al developed an SSG system using a membrane with CuFeSe2 nanoparticles decorated wood [12] CuFeSe2 had a narrow bandgap (0.45 eV) so it can absorb all photons with energy greater than 0.45 eV (equivalent to wavelength shorter than

2755 nm) This SSG system achieved a solar thermal efficiency of 86.2% under 5 sun illumination The evaporated water amount obtained with another semiconductor materials was from 0.85 to 1.3 kg.m-2.h SSG system using the semiconductor as a photo-thermal material will be difficult to fabricate with high price and be complicate to deal with large-scale system

The third type of PTC is thermal vibration of molecules Several materials have extremely high absorption, and all absorbed photon energy will be converted to thermal energy in the form of vibrations of the molecules of the material through the photo-thermal conversion Especially, carbon-based materials with zero band

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gap can absorb sunlight as a black body They are cheap, stable and easy to fabricate Carbonization process, which can turn any material with a specific structure into carbon-based materials with the same structure, plays an important role in making carbon-based materials Lin et al synthesized SSG system by annealing to make the carbonized melamine foams, realizing highly efficient SSG with a water evaporation rate of 1.270 kg.m-2.h-1 and an energy conversion efficiency of 87.3% under 1 kW.m-2 solar illumination [9] Zhu et al developed the SSG devices based on the natural materials, such as mushroom, wood, so on [24] The mushroom was carbonized at high temperatures As a result, the surface of the mushroom turned into black and the absorbance of the carbonized mushroom increased to above 95% in the wavelength range of 30-3000 nm The SSG device performed a high photo-thermal conversion efficiency as above 85%, and an evaporation rate of 1.47 kg.m-2.h-1 The evaporated water quality met the standards

of WHO for the drinking (or clean) water Carbonization material provides a good performance for SSG system, simple fabrication process, environmentally friendly, promising to be a key material for setting up SSG system In particular, carbonization materials of biological origin (naturally occurring) -named bio-metamaterials- are currently receiving much attention Constructing the SSG system using bio-metamaterial materials is a potential, and feasible direction

1.2.3 Purpose of this master thesis

The pomelo is the most common fruit in Vietnam The pomelo is not only a kind of human food, other components of the pomelo also have many application in our life Pomelo's outer skin contains many essential oils, those essential oils are used as a remedy for hair loss, sinusitis, etc Pomelo peel is used as some traditional folk dishes and also have applications in medicinal healing In this master thesis, pomelo peel have been considered because of their porous structure With the porous structure of the pomelo peel, the carbonized pomelo peel (CPP) promises not only the good light-absorber material, but also the good ability to transport water onto the surface itself Carbonized pomelo peel promises to be a good bio-metamaterial for constructing the SSG system We hope that the SSG using the carbonized

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pomelo peel as PTC material will have high absorbance, high efficiency of thermal conversion, good ability in desalination and purification

photo-This master thesis aims at:

• Fabricating the photo-thermal conversion (PTC) material from natural sources by the carbonization method

• Studying on the PTC characteristics

• Evaluating the absorption of bio-metamaterial under the sunlight

• Developing a SSG system, using bio-metamaterial as a absorber layer (will mention in the chapter 2)

• SSG system evaluation:

• Assessing the evaporation capacity of the system

• Demonstration in producing clean water from saline water using the Solar Steam Generation system, which is based on solar energy, bio-inspired materials with light absorbability and one-dimensional capillary sheets with high efficiency

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CHAPTER 2: EXPERIMENTAL METHOD

2.1 Carbonized pomelo peel synthesis and characteristics

20 mm

Figure 2.1: Fresh pomelo (a) and (b), and Fresh pomelo peel (c)

• Pomelo peel slices were washed by the solution of domestic water and absolute ethanol 3 times with the stirrer at 200 rpm for 30 minutes at room temperature

• After that, they were dried at 4000C for 12 hours The moderate temperature helps the water evaporate while keeping the sample from bending after drying

• Dried-pomelo peel was taken part in a carbonization process at controllable temperature and time in the nitrogen atmosphere The carbonization process was performed as follows:

1 Put the pomelo peel sample into the annealing tube, the lock the valve

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2 Vacuum for 5 minutes Then blow nitrogen into the tube until the pressure is equal to atmospheric pressure Do this step at least 3 times to make the annealing tube clean

3 Blow nitrogen so that the pressure is maintained at 1.5 atmospheres

4 Increase the temperature with the speed of 500 per minute

5 When the system reaches the desired temperature, keep the system at that temperature for a specified time

6 Stop heating the system, wait until the system temperature returns to room temperature, then take the sample Figure 2.2 shows a sample of carbonized pomelo peel

7 Store the sample in a dry condition

Figure 2.2: Pomelo peel and carbonized pomelo peel

2.1.2 Carbonized pomelo peel characteristics

• To study the structure and composition of materials, the following methods were used:

1 SEM to observe the material morphology

2 XRD, FTIR, Raman to study on the structure and composition of materials

• To investigate other properties of the material:

1 Absorption properties of carbonized pomelo peel

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2 Solar heating behavior of carbonized pomelo peel

3 The stability of materials

2.2 SSG System construction and evaluation

2.2.1 Construction of the SSG system

Figure 2.3 describes the structure of light absorber and converter part and water supply part of the SSG system Carbonized pomelo peel is placed at the top of the beaker containing water The area of the sample is designed to be equal to the surface area of the beaker Separating the water supply and carbonized pomelo peel has a Polystyrene Foam sheet This sheet helps prevent the heat exchange between materials and the water supply Surrounding the foam sheet is a gauze pad, the gauze pad acts as a water transport channel, transport water from the water supply

to the carbonized pomelo peel Water is transported to the surface through the porous structure and tube structure of the material Finally, the baker is wrapped around with aluminum foil

Figure 2.3: Light absorber and converter and water supply

2.2.2 SSG system evaluation

• To study the SSG system evaluation, the following methods were used:

1 Evaluate the evaporation index of the system

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Figure 2.4 shows the experimental diagram for determining the evaporation rate of the SSG system The beaker (constructed in section 2.2.1) is placed on the electronic balance The mass of the system will be collected at different times, to determine the amount of evaporated water After that, the evaporation rate of the system is equal to the lost mass divided by the illuminated sample area

Figure 2.4: System to calculate the evaporation rate in the laboratory

2 Evaluate the desalination and purification ability

For the desalination and purification processes, all experiments are done in the real condition The baker containing the carbonized pomelo peel is placed into a sealed glass box designed as in Figure 2.5 The sun shines on the system, and makes the water evaporate That vapor will exist in a sealed glass box A cooling system, placed next to that glass case (dry ice), leading to the condensation of the steam inside the box Finally, the steam condenses into water and flows out through the hole at the bottom of the box For the desalination, sea water will be selected as a source of input water After taking enough amount of purified water, the ion concentration of both solutions is analyzed via SW-846 Test Method 6010D by using Skalar ++ CP-OES For the purification process, crystal violet and methyl orange solutions are pick as the wastewater The color and transparency of the purified solution will be assessed to evaluate the performance of the system

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Figure 2.5: Mechanism of the system in the real condition

2.3 Equipment

Table 2.1 shows some equipment used in measurement in the thesis

Table 2.1: Some equipment used in this master thesis

200 nm to 900 nm

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X-ray Diffraction (XRD Mini Flex

600, Rigaku, Japan) spectra of sample were obtained using a Bruker

AXN model

Fourier- transform infrared

(FTIR-4600, Jasco, Japan) spectra of samples were recorded on a Nicole

380 spectrometer

Raman Labram evolution (Horiba)

Annealing equipment for carbonization process

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SEM for observing the material

morphology

HOBO pyranometer for measuring

the sunlight intensity

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CHAPTER 3: RESULTS AND DISCUSSION

3.1 Carbonized pomelo peel

3.1.1 Physical characteristics of carbonized pomelo peel

3.1.1.1 SEM image

Figure 3.1: Porous Structure and Tube Structure of Fresh Pomelo Peel (left) and

Carbonized Pomelo Peel Figure 3.1 describes the morphology of fresh pomelo peel and the CPP The annealing condition of this CPP was: 4000C for 2 hours On a large scale, both materials exhibit porous and tube structures Tube structure is surrounded by porous structures and is a minority This proves that, after participating in the carbonization process, the structure of the material remains unchanged Moreover, the porous structure, and especially the tube structure, can perform well as a water channel Water in the water supply will be brought to the surface of the absorption layer through capillary force The water can then absorb heat easily and evaporate

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Figure 3.2: Changes in structural dimensions before and after carbonization process

(a), (b), (c): Fresh Pomelo Peel; (d), (e), (f): Carbonized Pomelo Peel

Figure 3.2 shows the dimensions of the tube structure and the porous structure of the material before and after the carbonization process Fresh Pomelo Peel has a porous structure with a hole diameter of about 300- 400 µm After carbonization, although the porous structure remains the same, the diameter of the holes is significantly reduced Most holes in the porous structure range in size from 75 to

150 µm Similarly, the diameter of the tube mouth in the tube structure is also reduced This is explained by the evaporation of water in the material structure during carbonization process At high temperatures, the material loses water, causing all structures to shrink from 2 to 4 times As the size of the internal structure of the material becomes smaller, it is beneficial to transport water The higher capillary force, the better water transport system, also the better water retention ability