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dc.contributor.advisorGang Chen.en_US
dc.contributor.authorNi, George (George Wei)en_US
dc.contributor.otherMassachusetts Institute of Technology. Department of Mechanical Engineering.en_US
dc.date.accessioned2018-05-23T16:32:33Z
dc.date.available2018-05-23T16:32:33Z
dc.date.copyright2018en_US
dc.date.issued2018en_US
dc.identifier.urihttp://hdl.handle.net/1721.1/115737
dc.descriptionThesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.en_US
dc.descriptionCataloged from PDF version of thesis.en_US
dc.descriptionIncludes bibliographical references (pages 163-170).en_US
dc.description.abstractSustainable access to energy and access to water are two of the defining technological problems that society currently faces. Threats of climate change and depletion of fossil fuel reserves are forcing a shift towards more renewable sources of energy, such as solar energy and others. At the same time, water resources are becoming scarcer, caused by unsustainable extraction of ground water resources. Current projections show that by 2025, the population of people living in water-stressed areas is expected to increase to 3.9 billion. Exacerbating this problem is continuing urbanization, which stresses local water supplies further. The two problems of energy and water are inextricably tied together. Water processing, such as desalination and wastewater management, fundamentally requires energy inputs, while energy production often requires water for operational cooling. This thesis focuses on developing technologies for low-intensity utilization of solar energy for desalination and wastewater management. Traditional solar thermal technologies collect sunlight, and use motorized optical concentrators to concentrate the weak solar flux to create high temperature steam, often 400'C or higher. These optical concentrators are costly and require maintenance that are unattractive in many small-scale and low-intensity applications. These applications include distributed desalination, medical sterilization, wastewater management, and more. In this thesis, the research has focused on 1) evaporation mechanisms in nanofluids for solar applications, 2) a solar steam generation structure that operates without optical concentrators, and 3) a floating solar still that produces water without the need for periodic cleaning of excess salts, and has a material cost of $3 to supply individual daily drinking water needs, which can be paid back quickly for some regions like the Maldive. One of the first approaches to solar vapor generation was to use nanoparticles suspended in water, or nanofluids, to localize solar absorption to near the evaporation surface. This approach reduces the temperature drop between the heat generation site and the evaporation surface, increasing the evaporation rate. This thesis first explores the vapor generation mechanisms in nanofluid-based solar vapor generation, and develops a small-scale nanofluid-based solar receiver that could generate vapor at 70% efficiency. A theory was developed to show how nanoparticle suspension could affect the nanofluid transient performance. This thesis next demonstrates a small-scale floating solar steam generator, that does not require optical concentration. This was achieved by further extending the heat localization concept, using various widely available materials to reduce radiative, convective, and conductive losses. By reconfiguring the device, steam at 100°C or vapor at 70% efficiency could be produced. The basic steam generator was then improved and adapted to reject excess salts left behind from vapor formation. The salt rejecting structure was coupled with a condensation cover, to form a floating solar still that was demonstrated to operate in the ocean, simultaneously producing drinkable water and rejecting the excess salts. Salt rejection experiments were conducted to prove the long-term ability of the structure to operate in saline waters.en_US
dc.description.statementofresponsibilityby George Wei Ni.en_US
dc.format.extent170 pagesen_US
dc.language.isoengen_US
dc.publisherMassachusetts Institute of Technologyen_US
dc.rightsMIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission.en_US
dc.rights.urihttp://dspace.mit.edu/handle/1721.1/7582en_US
dc.subjectMechanical Engineering.en_US
dc.titleLow-cost, high performance solar vapor generationen_US
dc.typeThesisen_US
dc.description.degreePh. D.en_US
dc.contributor.departmentMassachusetts Institute of Technology. Department of Mechanical Engineering.en_US
dc.contributor.departmentMassachusetts Institute of Technology. Department of Mechanical Engineering
dc.identifier.oclc1036986748en_US


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