Biometamaterials application for solar steam generation device

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 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 i 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 1.2 Solar Steam Generation 1.2.1 Mechanism of SSG 1.2.2 Absorber Material .3 1.2.3 Purpose of this master thesis .5 CHAPTER 2: EXPERIMENTAL METHOD 2.1 Carbonized pomelo peel synthesis and characteristics 2.1.1 Fabrication procedure 2.1.2 Carbonized pomelo peel characteristics .8 2.2 SSG System construction and evaluation 2.2.1 Construction of the SSG system .9 2.2.2 SSG system evaluation 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 ii 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 Figure 2.1: Fresh pomelo (a) and (b), and Fresh pomelo peel (c) Figure 2.2: Pomelo peel and carbonized pomelo peel 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 hour of annealing time 20 Figure 3.8: Absorption properties of carbonized pomelo peel with and 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 hour; (b): Evaporation Rate within 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 iii Figure 3.17: Vapor steam creation capacity under different power intensity 31 Figure 3.18: Vapor steam creation capacity after 30 days 32 Figure 3.19: Cation concentration (top), and Anion concentration (bottom) of Sea water and Purified water compared to the Standard of drinking water 33 Figure 3.20: Wastewater Purification Application 34 iv LIST OF TABLES Page Table 2.1: Some equipment used in this master thesis .11 Table 4.1: The comparison of evaporation rate for each material and its disadvantages 35 v LIST OF ABBREVIATIONS CPP NPs PTC SSG Carbonized Pomelo Peel Nanoparticles Photo-thermal conversion Solar Steam Generation vi 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 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 ecofriendly, 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 hour is equal to the total amount of energy that humans use within 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 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 the sample, the sample with the larger the coefficient will have the stronger the process of heat exchange with the environment For the sharing of the thermal vibration of molecules, only the neighbor-molecules exchange process is preferred Therefore, when the thickness of the sample is larger than 10 mm, the saturation temperature of the sample when placed under artificial sunlight does not increase anymore due to the constant in the total energy sharing Thereby, 10 mm is also chosen as the optimal condition for the thickness of the material 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 Figure 3.13 lists several factors that affect the temperature of the material The presence of wind promotes the heat exchange of materials with their surroundings, leading to a decrease in temperature However, when the wind disappeared, the material temperature increased incontinently and still reached a high temperature Besides, solar intensity and cloud affect the total photon energy that reaches the material in a unit of time As the light flux decreases, the total heat energy converted from light energy also decreases, hence the temperature of the sample 26 also decreases Because of the above factors, wind, solar intensity, clouds should be considered to improve the performance of Solar Steam Generation system in the reality 3.2 Solar steam generation system ability 3.2.1 Vapor steam creation capacity 3.2.1.1 Vapor steam creation capacity under an artificial sun Figure 3.14: Vapor steam creation ability under an artificial sun Figure 3.14 describes the vapor steam creation ability of different samples with the same thickness of 4mm under an artificial sun with P=1 kW.m-2 (1 sun illumination) The blue line exhibits the vapor evaporation in the dark condition while the black line shows that indicator in an artificial sun condition The amount of evaporated water will be calculated based on the change in mass of the system (as the steam evaporates away, the total mass of the system decreases) Within one hour, the amount of water evaporated in the dark is 0.05 kg.m-2, while that amount in sun illumination is around 0.4 kg.m-2 Thus, the sunlight promotes evaporation process 27 about 10 times compared to original condition Water molecules receive energy from incident light and raise the temperature After that, the water molecules continue receiving more photon energy to convert the phase from liquid to vapor With the attendance of carbonized pomelo peel, more photons are absorbed, leading to the higher in total energy input Thus, the evaporation index in these cases has a significant growth Within hour, the amount of evaporated water of the 3000Cwithin hours of annealing sample is 1.47 kg.m-2 That number of samples with condition 4000C-3h and 5000C-3h are almost the same and reach around 1.8 kg.m-2 This phenomenon is explained by the higher absorbances of the 4000C and 5000C samples compared to the 3000C sample, resulting in a greater total energy input Figure 3.15: Vapor steam creation ability with different conditions of thickness under an artificial sun (a): Mass change within hour; (b): Evaporation Rate within hour; (c) Carbonized pomelo peel’s infrared photos when exposing to the sunlight Figure 3.15a describes the evaporation capacity of the SSG system when using carbonized materials with different thicknesses On the other hand, figure 3.15b gives information about the evaporation rate of the respective conditions When using a thicker carbonized pomelo peel as an absorber layer, the amount of evaporated water under the same exposing conditions will be greater Within hour, 28 the amount of evaporated water of SSG systems is 1.3 kg m-2, 1.6 kg m-2, 2.1 kg m-2, and 2.4 kg m-2 with the carbonized pomelo peel thickness of mm, mm, mm, and 10 mm respectively In figure 3.15b, the evaporation rate of all samples increases gradually during the first period, and the change is not significant after that As discussed before, thicker materials will have a higher saturation temperature Thus, the amount of evaporated water within a unit time is also greater To explain the change of evaporation rate with different carbonized pomelo peel thicknesses, energy exchange processes are considered At the beginning, heat absorbed through the thermal vibration of the molecules increases Besides, water is transported through the water channel to the surface and conducts heat exchange with absorbing material The energy mainly raises the temperature of the water and a small part is involved in the water phase transition, leading the increment of evaporation rate from After that, when the heat exchange process becomes stable, the energy absorbed by the photon is balanced with the total of heat loss and the energy transferred to water; the water evaporation rate will increase slowly and arrive at the saturation state Figure 3.15c shows the temperature of the absorption layer (carbonized pomelo peel) from the 15th to the 75th minute during the evaporation process In the beginning, the CPP temperature gradually increased from the room temperature After 15 minutes, the surface temperature of the material has a relatively constant temperature, which shows the stability of the SSG system when performing evaporation process 3.2.1.2 Vapor steam creation capacity under the real condition Figure 3.16 exhibits the vapor steam creation capacity under the real condition The power intensity is calculated by using the HOBO pyranometer (MCCD- VJU, Vietnam) For 160 minutes, with power intensity conditions of 0.7 to 0.85 kW m-2, the maximum amount of evaporation water that the system can generate reaches around kg m-2 for the 5000C-3h CPP sample Annealing conditions of 4000C for CPP exhibit a lower amount in the change of water’s mass, but still good (around kg m-2 per 160 minutes) For the 4000C, the annealing time of hours and hours gives nearly the same results The evaporation rate of the SSG system in actual 29 conditions is higher than that in laboratory conditions due to several factors Firstly, the evaporation rate depends on the humidity index of the environment In the real condition when the experiment is taken, the humidity index is small, so the evaporation of water is accelerated Secondly, the average temperature in the real condition and the temperature in the laboratory condition is 370C and 290C, respectively With higher temperature, the SSG system in the real condition requires less energy to change the state of water from liquid to vapor Moreover, the process of heat exchange with the environment of SSG system also occurs less frequently, because the difference in temperature is less For long enough, the water in the water supply system also exchanges heat with its surroundings and receiving the sunlight energy and raises the temperature, so the amount of evaporation of water increases with time If the evaporation process is only considered within the first 60 minutes, when the water supply water temperature has not increased much, the water evaporation rate in the real condition and the laboratory condition is similar This proves that the SSG system not only works well in the laboratory condition, but also shows a great performance in the real condition Figure 3.16: Vapor steam creation capacity under the real condition 30 The effect of power intensity of sunlight in the real condition should also be considered Figure 3.17 shows the evaporation of the SSG system when using 5000C-3h CPP as a PTC material under different conditions of solar energy intensity At the sunlight intensity of 0.7 to 0.85 sun (equivalent to 0.7 to 0.85 kW m-2), the evaporated water within 150 minutes is approximately 6.7 kg m-2 As the intensity of the sunlight decreases, the amount of the evaporated water during the same time also decreases At 0.4 sun and 0.2 sun, the evaporated water is 4.15 and 2.48 kg m-2.h-1, respectively When the sunlight intensity decreases by 1.75 ~ times, the amount of evaporated water decreases by 1.6 times When the sunlight intensity decreases by 3.5 to times, the evaporated water decreases by 2.7 times Thus, the amount of evaporated water is not linearly proportional to the intensity of sunlight When the intensity of sunlight is low, the temperature of PTC material is not high, leading to the reduction of heat loss due to exchange with the environment, leading to better system performance than that SSG system at the time of high sunlight intensity This proves that the system also works well under the low power intensity and responds to actual sunlight conditions in Vietnam Figure 3.17: Vapor steam creation capacity under different power intensity 31 3.2.1.3 Photo-thermal conversion materials stability The stability of PTC material is assessed based on the performance of the SSG system using that material after 30 days and compared with their first result Figure 3.18 shows the evaporation capacity of the SSG system using CPP 400 0C-2h on day and day 30 in an artificial sun with sun illumination Both cases show the amount of evaporated water of about 1.56 to 1.71 kg m-2 within 80 minutes The amount of evaporated water on day 30 is about 10% smaller than that in the first day This implies that PTC material can work well after many times with stability up to several months After one month, the material has no change in shape and structure, the image is shown in the figure 3.18 Figure 3.18: Vapor steam creation capacity after 30 days 32 3.2.2 Desalination and purification capacity of the SSG system Figure 3.19: Cation concentration (top), and Anion concentration (bottom) of Sea water and Purified water compared to the Standard of drinking water The carbonized pomelo peel exhibits an impressive performance of water evaporation from seawater and contaminated water To evaluate the water desalination application of the SSG system, the concentration of ions in the solution was determined The original water source was sea water, taken from Quynh Phuong beach, Hoang Mai, Nghe An province The SSG system was utilized to 33 filter the original water source, then purified water was created The concentration of ions in the solution of Seawater and filtered water was analyzed by SW-846 Test Method 6010D by using Skalar ++ CP-OES Figure 3.19 shows the concentration of cations (top) and anions (bottom) in the seawater and the purified water The concentration of the ions in the seawater is much higher than the concentration of the same ion in the purified water, implies the particularly good desalination process of the SSG system Especially, the concentration of these ions is also much smaller than the maximum allowed for the standard of drinking water (black-dot line) Once again, this confirms the good application in desalination of the SSG system Not only demonstrating good desalination capacity, SSG system works extremely well in purifying the wastewater Crystal Violet and methyl orange solutions are used to simulate wastewater After participating in the evaporation and condensation of SSG system, the solution obtained under both conditions becomes clean water with colorless and transparent Pictures of the original solution and the purified water placed side by side, are shown in Figure 3.20 Figure 3.20: Wastewater Purification Application 34 CHAPTER 4: CONCLUSION The SSG system using carbonized pomelo peel as the photo-thermal conversion material is constructed and evaluated for the specific characteristics The carbonization process helps the pomelo peel retain its porous and tube structure, while increasing its absorption properties Carbonized pomelo peel’s absorbance is above 95% in the ultraviolet region and visible, more than 90% in the infrared The surface temperature of carbonized pomelo peel can reach 930C at sun illumination (P=1 kW.m-2) The SSG system utilizing carbonized pomelo peel as the photothermal conversion material has an efficient performance, with a water evaporation coefficient of up to 2.4 kg.m-2.h at sun illumination The purified water of the SSG system passes the drinking water standard provided by WHO and other prestigious organizations in the world The system also works well in wastewater treatment, shown by purifying the precursor color solutions into clear, colorless water Table 4.1: The comparison of evaporation rate for each material and its disadvantages Material Evaporation rate Power density Limitation (kg m-2.h-1) (sun) Cu NPs 2.3256 Low efficiency Black Ag 1.38 Expensive WO2.9 1.28 Cumbersome MoOx HNS 1.255 Complex Chinese ink 1.31 / Carbon fiber 1.47 / RGO+MWCNTs 1.31 No cheap Carbonized mushrooms 1.475 Energy Consumption 35 Carbonized seedpods 1.3 Energy Consumption Carbonized kelps 1.351 Energy Consumption APAC 1.2 Low Efficiency SnSe@NF 0.85 Low efficiency BiInSe3 @NF 0.83 Low efficiency TiN 2.77 High power density MG/PNIPAm 1.66