| 项目编号: | 1653631
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| 项目名称: | CAREER: Synthetic Mangrove Trees for Passive Desalination and Water Harvesting |
| 作者: | Jonathan Boreyko
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| 承担单位: | Virginia Polytechnic Institute and State University
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| 批准年: | 2017
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| 开始日期: | 2017-03-15
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| 结束日期: | 2022-02-28
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| 资助金额: | 522145
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| 资助来源: | US-NSF
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| 项目类别: | Standard Grant
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| 国家: | US
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| 语种: | 英语
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| 特色学科分类: | Engineering - Chemical, Bioengineering, Environmental, and Transport Systems
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| 英文关键词: | water
; nano-pore
; ocean water
; mangrove tree
; micro-channel
; fresh water
; xylem
; water harvestingat
; water meniscus
; passive desalination
; leaf
; water reservoir
; large-scale desalination
; synthetic mangrove
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| 英文摘要: | Synthetic Mangrove Trees for Passive Desalination and Water Harvesting
At least one-third of the world population does not have enough access to fresh water, and this is predicted to increase to two-thirds by 2025. Reverse osmosis plants, which pump ocean water through filters, are useful for large-scale desalination but require a large power consumption of about 2 kilowatt-hours for every cubic meter of purified water. Inspired by mangrove trees, this project seeks to develop an alternative means of harvesting fresh water that is powered by transpiration and does not require any active energy input. Synthetic mangrove leaves will be fabricated using 3D printing and connected to an array of micro-channels that mimic the xylem conduits of trees. As water evaporates from the nano-pores of the synthetic leaves, the water still inside of the leaves will exhibit a negative (suction) pressure due to the concave curvature of the water meniscus within each nano-pore. This suction pressure will generate a pressure differential across the synthetic xylem to allow for continuous pumping of water from a reservoir or moist soil. The ultimate goal is to achieve a suction pressure strong enough to pull ocean water through a salt-excluding filter without requiring a mechanical pump, analogous to how mangrove trees are able to grow in ocean water. To reach out to a broad audience, a completed artificial mangrove tree will be used to design a new exhibit at the Virginia Museum of Natural History.
The objective of this project is to develop a synthetic mangrove tree capable of passively desalinating ocean water by generating transpiration-induced hydraulic loads exceeding 3 MPa. It is already known that water transpiring from a nanoporous medium can induce a highly negative water pressure due to the concave curvature of the menisci. However, current synthetic trees exhibit a very low hydraulic conductance and do not feature stomata on the transpiring leaves to help stabilize the water, which has constrained the hydraulic load to under 1 MPa and required impractical ambient humidities of over 85% to avoid dryout or boiling instabilities. Here, the stability and throughput of water flowing through synthetic trees will be dramatically improved by 3D printing an array of substomatal chambers and stomatal apertures at the interface of the synthetic leaves and by connecting the leaves to a dense array of micro-channels (xylem). The hypothesis is that the substomatal chambers serve to locally increase the humidity to avoid cavitation even in highly subsaturated ambient environments, while the increased conductance of the micro-channel array should prevent leaf dryout. The mass flux and by extension the hydraulic load will be measured by connecting the xylem to a water reservoir placed on a mass balance, heating the underside of the leaf, and exposing the top of the leaf to a controlled subsaturated ambient. The onset and dynamics of cavitation/dryout events will be captured using a top-down microscope focused on the xylem micro-channels. The metastability of the water will be analyzed using the Kelvin equation, Laplace equation, and classical nucleation theory. The flow of water through the tree will be modeled using Poiseuille's law (xylem), Darcy's law (nano-pores), and Fick's law (stomata). These theoretical insights will be correlated with the experimental measurements to optimize the design configuration of the final synthetic tree. The synergistic blend of controlled nanofabrication, experimental characterization, and theoretical analysis should uniquely reveal how the configuration of the xylem, nano-pores, substomatal chambers, and stomata serve to cooperatively govern the transpiration rate of water through trees. |
| 资源类型: | 项目
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| 标识符: | http://119.78.100.158/handle/2HF3EXSE/90411
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| Appears in Collections: | 全球变化的国际研究计划
科学计划与规划
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| Recommended Citation: | |
Jonathan Boreyko. CAREER: Synthetic Mangrove Trees for Passive Desalination and Water Harvesting. 2017-01-01.
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