Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor | Department of Applied Physics | en_US |
| dc.contributor.advisor | Tsang, Yuen Hong (AP) | en_US |
| dc.creator | Ivan, Md. Nahian Al Subri | - |
| dc.identifier.uri | https://theses.lib.polyu.edu.hk/handle/200/13226 | - |
| dc.language | English | en_US |
| dc.publisher | Hong Kong Polytechnic University | en_US |
| dc.rights | All rights reserved | en_US |
| dc.title | Biodegradable waste material derived solar evaporators for interfacial solar steam generation based desalination and wastewater purification application | en_US |
| dcterms.abstract | Due to the rapid depletion of fossil fuel and its adverse effect on environment, the world is leaning towards renewable energy sources. Among all renewable energy sources, solar energy is considered to be the most abundant and easily accessible source as other sources (i.e., wind, water, geothermal etc.) depend greatly on the geographical position of a country. For many years solar energy has been used by photovoltaic cell systems and concentrating solar power (CSP) system for electricity generation. Recently, due to the development of material science and technology solar energy is being used for photothermal energy conversion or for photocatalytic reactions. In the photothermal energy conversion process materials are used for absorbing solar energy and converting it to heat. Later, the produced heat can be used for generating electricity or steam. At present, the Interfacial solar steam generation (ISSG) technique has become very popular as it can solve the problems of water scarcity by purifying wastewater or by desalinating sea water using solar energy. The conventional methods of desalinating sea water (both thermal and membrane-based system) require high energy which creates energy demand and burning of fossil fuels to meet that demand causes harm to the environment. Moreover, these technologies require very high infrastructural cost as well as operating cost that make them unreachable for the 3rd world countries where freshwater crisis is very prominent. On the other hand, desalination or purification of water using ISSG technique is electricity independent in nature which gives it a competitive edge over other technologies to face the challenge of water scarcity at lower cost. | en_US |
| dcterms.abstract | The process of desalinating sea water or purifying wastewater by ISSG technique depends mainly on the performance of the evaporator. A solar evaporator generally has two main functions, i) absorbing sunlight and convert it to heat, ii) absorbing water and transfer it to the air water interface where heat is localized. Researchers have suggested many metallic, polymeric, semiconductor-based and carbon-based materials for their good light absorbing capability and photothermal conversion ability. However, the evaporation performance does not only depend on the performance of the photothermal materials. The shape of the evaporator, water transport mechanism, salt rejection capability also plays an important role for increasing the efficiency and performance of the solar evaporator. Hence a lot of factors are required to be considered during the fabrication of solar evaporators. Interestingly, some highly efficient solar evaporators make the ISSG technique unfeasible for commercialization or unreachable to the third world countries due to the complex fabrication process, fabrication cost of the evaporator and the cost of materials. The aim of this thesis is to explore different types of materials with photothermal conversion capability and explore different types of structures to design a cost-effective and highly efficient solar evaporator for freshwater generation. | en_US |
| dcterms.abstract | Solving the problem of water crisis and managing as well as disposing the ever-increasing waste materials (i.e., municipal solid waste (MSW), e-waste etc.) are becoming global concerns with the growth of civilization. A sustainable way of confronting these challenges has been proposed in this thesis by fabricating a 3D solar evaporator from waste egg trays (MSW) and waste dry toner particles (e-waste) using a facile fabrication process. Egg trays have unique 3D structure to hold the eggs. These trays are generally prepared by recycling wastepaper, and hence have low thermal conductivity. Moreover, due to the presence of cellulose, porous as well as fibrous surface morphology, these egg trays have good water absorbing capability which makes them an excellent substrate for fabricating solar evaporator. On the other hand, the waste dry black toner contains carbon black and magnetite which are well known for their excellent light absorbing capability and photothermal conversion ability. Hence a cost-effective 3D solar evaporator can be fabricated by coating the waste toner on the top of egg trays. The fabrication procedure requires low temperature heat treatment which reduces the fabrication cost as well. The fabricated solar evaporator exhibits an outstanding water evaporation rate and efficiency of 1.3 kg m-2 h-1 and 78.5% respectively, under one sun (1 sun = 1 kW m-2) illumination. Moreover, the 3D structure shows higher efficiency than 2D structure throughout the day as it has the capability of collecting solar irradiance at various light incidence angles and can harvest energy from the environment to evaporate water. The proposed evaporators show good performance in desalinating sea water and purifying dye contaminated water. Except these, excellent cycle stability, and the uses of low-cost waste materials make this solar evaporator feasible for large-scale water purification system. | en_US |
| dcterms.abstract | The accumulation of salt crystals on the solar surface of the evaporator is one of the main challenges associated with desalinating sea water using the interfacial solar steam generation technique. To solve this issue, sustainable evaporators of different salt mitigation mechanism is fabricated using the alkali treated Jute stick (JS), an agricultural waste for the first time and the performance of the evaporators are compared in this thesis. The lateral salt mitigation mechanism was experimentally verified by 4-day long experiment and the influence of different solar irradiation on accumulating salt on the solar absorbing surface during evaporating highly NaCl concentrated water was studied. JS features a center natural hole surrounded by several microchannels with pits on the microchannels' walls, which makes it exceptional for constructing solar evaporators with natural hole induced salt ion diffusion backflow mechanism by simply carbonizing the top surface. This mechanism worked well under 1 sun illumination for sea water desalination with evaporation rate and efficiency of 1.52 kg m-2 h-1 and 87.01%, respectively. No salt was observed on the top surface of the evaporator after an 8.5-hour long seawater evaporation experiment under 1 sun. The evaporator also demonstrated excellent performance in evaporating and purifying different dye (Methylene Blue, Congo Red and Eriochrome Black T) contaminated water. However, the salt starts to grow on the top surface of the evaporators during evaporating highly NaCl (20 wt%) concentrated water at higher solar irradiance. Therefore, a solar evaporator with direct salt blocking and salt ion diffusion backflow mechanism was fabricated by coating the top surface of alkali-treated JS with hydrophobic Multi-Walled Carbon Nanotubes (MWCNTs) to impart Janus characteristics to the evaporator. The proposed evaporator has a hydrophilic water absorbing surface at the bottom and a thin layer of hydrophobic solar absorbing surface at the top. The evaporation of water takes place at hydrophobic-hydrophilic interface. Under one sun, it evaporated sea water at a rate of 1.46 kg m-2 h-1 with 84.39% efficiency and demonstrated excellent performance in evaporating highly NaCl concentrated water under varying solar irradiance (from 1 sun to 3 sun) with efficiency above 70% without any growth of salt on the top solar absorbing surface. | en_US |
| dcterms.abstract | Finally, this thesis explores organometallic, and semiconductor based photothermal materials for interfacial solar steam generation application and present their potential in fabricating efficient solar evaporator by experimentation. | en_US |
| dcterms.extent | xxi, 179 pages : color illustrations | en_US |
| dcterms.isPartOf | PolyU Electronic Theses | en_US |
| dcterms.issued | 2023 | en_US |
| dcterms.educationalLevel | Ph.D. | en_US |
| dcterms.educationalLevel | All Doctorate | en_US |
| dcterms.LCSH | Solar energy | en_US |
| dcterms.LCSH | Evaporators | en_US |
| dcterms.LCSH | Fresh water | en_US |
| dcterms.LCSH | Saline water conversion | en_US |
| dcterms.LCSH | Sewage -- Purification | en_US |
| dcterms.LCSH | Hong Kong Polytechnic University -- Dissertations | en_US |
| dcterms.accessRights | open access | en_US |
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