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Menachem Elimelech - One of the best experts on this subject based on the ideXlab platform.
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membrane distillation assisted by heat pump for improved Desalination energy efficiency
2020Co-Authors: Evyatar Shaulsky, Zhangxin Wang, Akshay Deshmukh, Vasiliki Karanikola, Menachem ElimelechAbstract:Abstract Thermal Desalination technologies are required for minimal and zero liquid discharge (MLD/ZLD). However, conventional and emerging Thermal Desalination technologies, such as mechanical vapor compression (MVC) and membrane distillation (MD), are usually highly expensive to implement or/and energy intensive to operate. In this study, we develop a novel Desalination technology by using a vapor-compression pump to assist membrane distillation (MD). Comparing the energy efficiencies of the novel heat-pump assisted MD (HPMD), MVC, and conventional MD under similar operating conditions, demonstrates that HPMD is an energy-efficient Thermal Desalination technology. Furthermore, through process modeling, we provide guidelines for HPMD system design and show that the HPMD can theoretically obtain low energy consumption (~10 kWh of electrical energy per cubic meter of produced fresh water or gain output ratio, GOR, of ~60) and high water vapor flux (i.e., >60 L m−2 h−1). We conclude by highlighting promising applications of HPMD for MLD/ZLD, enabled by its high energy efficiency, low capital cost, and modularity.
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economic performance of membrane distillation configurations in optimal solar Thermal Desalination systems
2019Co-Authors: Akshay Deshmukh, Vasiliki Karanikola, Menachem Elimelech, Sarah E Moore, Robert G Arnold, Eduardo A SaezAbstract:Abstract In this study we provide a comprehensive evaluation of the economic performance and viability of solar membrane distillation (MD). To achieve this goal, process models based on mass and energy balances were used to find the minimum cost of water in MD systems. Three MD configurations: direct contact, sweeping gas, and vacuum MD, were compared in terms of economic cost and energy requirements in optimized, solar-driven Desalination systems constrained to produce 10 m3 d−1 of distillate from 3.5% or 15% salinity water. Simulation results were used to calculate the water production cost as a function of 13 decision variables, including equipment size and operational variables. Non-linear optimization was performed using the particle swarm algorithm to minimize water production costs and identify optimal values for all decision variables. Results indicate that vacuum MD outperforms alternative MD configurations both economically and energetically, desalting water at a cost of less than $15 per cubic meter of product water (both initial salt levels). The highest fraction of total cost for all configurations at each salinity level was attributed to the solar Thermal collectors—approximately 25% of the total present value cost. Storing energy in any form was economically unfavorable; the optimization scheme selected the smallest battery and hot water tank size allowed. Direct contact MD consumed significantly more energy (primarily Thermal) than other MD forms, leading to higher system economic costs as well.
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pathways and challenges for efficient solar Thermal Desalination
2019Co-Authors: Zhangxin Wang, Menachem Elimelech, Thomas Horseman, Anthony P Straub, Ngai Yin Yip, Shihong LinAbstract:Solar-Thermal Desalination (STD) is a potentially low-cost, sustainable approach for providing high-quality fresh water in the absence of water and energy infrastructures. Despite recent efforts to advance STD by improving heat-absorbing materials and system designs, the best strategies for maximizing STD performance remain uncertain. To address this problem, we identify three major steps in distillation-based STD: (i) light-to-heat energy conversion, (ii) Thermal vapor generation, and (iii) conversion of vapor to water via condensation. Using specific water productivity as a quantitative metric for energy efficiency, we show that efficient recovery of the latent heat of condensation is critical for STD performance enhancement, because solar vapor generation has already been pushed toward its performance limit. We also demonstrate that STD cannot compete with photovoltaic reverse osmosis Desalination in energy efficiency. We conclude by emphasizing the importance of factors other than energy efficiency, including cost, ease of maintenance, and applicability to hypersaline waters.
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understanding the impact of membrane properties and transport phenomena on the energetic performance of membrane distillation Desalination
2017Co-Authors: Akshay Deshmukh, Menachem ElimelechAbstract:Abstract Direct contact membrane distillation (DCMD) is a Thermal Desalination process that is capable of treating high salinity waters using low-grade heat. As a water treatment process, DCMD has several advantages, including the utilization of waste heat (below 100 ℃ ), perfect rejection of nonvolatile solutes, low areal footprint, and high scalability. However, the energy efficiency of DCMD is relatively low compared to other work-based and Thermal Desalination processes. In this study, we aim to quantify how membrane properties and process conditions affect the exergy or second-law efficiency ( η II ) of a DCMD Desalination system with external heat recovery. In particular, we analyze how the membrane permeability coefficient ( B ) and Thermal conduction coefficient ( K ) impact MD performance. We show that increasing the B value of a membrane by reducing its thickness, initially leads to an increase in η II before conductive heat loss through the membrane causes η II to fall. For a typical MD membrane with a porosity of 0.90 , material Thermal conductivity of 0.20 W m − 1 K − 1 , and a nominal pore diameter of 0.6 μ m , we find that the optimal permeability coefficient is 1.59 × 10 − 6 kg m − 2 s − 1 Pa − 1 ( 572 kg m − 2 h − 1 bar − 1 ). This value corresponds to an optimal membrane thickness of around 95 μ m . Our analysis stresses the importance of effective heat recovery in DCMD. We show that an external heat exchanger with a minimum approach temperature of 5 ℃ reduces energy consumption by 72 % . Finally, we demonstrate that increasing the ratio B / K , rather than just the B value, is key to increasing the exergy efficiency of DCMD Desalination. For example, increasing membrane porosity from 0.70 to 0.90 , which yields a 160 % increase in B / K , leads to a 42 % increase in η II from 5.3 % to 7.6 % . The advantages of reducing the bulk pressure ( P ) in the membrane pores are also explored. For a typical membrane, halving P from 1.0 bar to 0.5 bar , results in a 21 % increase in η II from 7.0 % to 9.2 % . We conclude by identifying that the maximum exergy efficiency achievable as membrane porosity tends to unity is 10 % for a bulk membrane pressure of 1.0 bar and 12 % for a bulk membrane pressure of 0.5 bar , given perfect heat recovery.
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Thermal Desalination membranes carbon nanotubes keep up the heat
2017Co-Authors: Chanhee Boo, Menachem ElimelechAbstract:Applying high-potential alternating current to a carbon-nanotube–polymer composite film provides a self-heating membrane that enhances Desalination performance of high-salinity brines by membrane distillation.
Naomi J Halas - One of the best experts on this subject based on the ideXlab platform.
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resonant energy transfer enhances solar Thermal Desalination
2020Co-Authors: Alessandro Alabastri, Pratiksha D Dongare, Oara Neumann, Peter Nordlander, Jordin Metz, Ifeoluwa Adebiyi, Naomi J HalasAbstract:Evaporation-based solar Thermal distillation is a promising approach for purifying high-salinity water, but the liquid-vapor phase transition inherent to this process makes it intrinsically energy intensive. Here we show that the exchange of heat between the distilled and input water can fulfill a resonance condition, resulting in dramatic increases in fresh water production. Large gains (500%) in distilled water are accomplished by coupling nanophotonics-enabled solar membrane distillation with dynamic Thermal recovery, achieved by controlling input flow rates as a function of incident light intensity. The resonance condition, achieved for the circulating heat flux between the distillate and feed, allows the system to behave in an entirely new way, as a Desalination oscillator. The resonant oscillator concept introduced here is universal and can be applied to other systems such as Thermal energy storage or solar-powered chemical reactors.
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solar Thermal Desalination as a nonlinear optical process
2019Co-Authors: Pratiksha D Dongare, Alessandro Alabastri, Oara Neumann, Peter Nordlander, Naomi J HalasAbstract:The ever-increasing global need for potable water requires practical, sustainable approaches for purifying abundant alternative sources such as seawater, high-salinity processed water, or underground reservoirs. Evaporation-based solutions are of particular interest for treating high salinity water, since conventional methods such as reverse osmosis have increasing energy requirements for higher concentrations of dissolved minerals. Demonstration of efficient water evaporation with heat localization in nanoparticle solutions under solar illumination has led to the recent rapid development of sustainable, solar-driven distillation methods. Given the amount of solar energy available per square meter at the Earth’s surface, however, it is important to utilize these incident photons as efficiently as possible to maximize clean water output. Here we show that merely focusing incident sunlight into small “hot spots” on a photoThermally active Desalination membrane dramatically increases––by more than 50%––the flux of distilled water. This large boost in efficiency results from the nearly exponential dependence of water vapor saturation pressure on temperature, and therefore on incident light intensity. Exploiting this inherent but previously unrecognized optical nonlinearity should enable the design of substantially higher-throughput solar Thermal Desalination methods. This property provides a mechanism capable of enhancing a far wider range of photoThermally driven processes with supralinear intensity dependence, such as light-driven chemical reactions and separation methods.
Vasiliki Karanikola - One of the best experts on this subject based on the ideXlab platform.
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membrane distillation assisted by heat pump for improved Desalination energy efficiency
2020Co-Authors: Evyatar Shaulsky, Zhangxin Wang, Akshay Deshmukh, Vasiliki Karanikola, Menachem ElimelechAbstract:Abstract Thermal Desalination technologies are required for minimal and zero liquid discharge (MLD/ZLD). However, conventional and emerging Thermal Desalination technologies, such as mechanical vapor compression (MVC) and membrane distillation (MD), are usually highly expensive to implement or/and energy intensive to operate. In this study, we develop a novel Desalination technology by using a vapor-compression pump to assist membrane distillation (MD). Comparing the energy efficiencies of the novel heat-pump assisted MD (HPMD), MVC, and conventional MD under similar operating conditions, demonstrates that HPMD is an energy-efficient Thermal Desalination technology. Furthermore, through process modeling, we provide guidelines for HPMD system design and show that the HPMD can theoretically obtain low energy consumption (~10 kWh of electrical energy per cubic meter of produced fresh water or gain output ratio, GOR, of ~60) and high water vapor flux (i.e., >60 L m−2 h−1). We conclude by highlighting promising applications of HPMD for MLD/ZLD, enabled by its high energy efficiency, low capital cost, and modularity.
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economic performance of membrane distillation configurations in optimal solar Thermal Desalination systems
2019Co-Authors: Akshay Deshmukh, Vasiliki Karanikola, Menachem Elimelech, Sarah E Moore, Robert G Arnold, Eduardo A SaezAbstract:Abstract In this study we provide a comprehensive evaluation of the economic performance and viability of solar membrane distillation (MD). To achieve this goal, process models based on mass and energy balances were used to find the minimum cost of water in MD systems. Three MD configurations: direct contact, sweeping gas, and vacuum MD, were compared in terms of economic cost and energy requirements in optimized, solar-driven Desalination systems constrained to produce 10 m3 d−1 of distillate from 3.5% or 15% salinity water. Simulation results were used to calculate the water production cost as a function of 13 decision variables, including equipment size and operational variables. Non-linear optimization was performed using the particle swarm algorithm to minimize water production costs and identify optimal values for all decision variables. Results indicate that vacuum MD outperforms alternative MD configurations both economically and energetically, desalting water at a cost of less than $15 per cubic meter of product water (both initial salt levels). The highest fraction of total cost for all configurations at each salinity level was attributed to the solar Thermal collectors—approximately 25% of the total present value cost. Storing energy in any form was economically unfavorable; the optimization scheme selected the smallest battery and hot water tank size allowed. Direct contact MD consumed significantly more energy (primarily Thermal) than other MD forms, leading to higher system economic costs as well.
P. Dutta - One of the best experts on this subject based on the ideXlab platform.
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solar driven adsorption Desalination system
2014Co-Authors: S Mitra, Kandadai Srinivasa, S. S. Murthy, Pramod Kuma, P. DuttaAbstract:Desalination is one of the most traditional processes to generate potable water. With the rise in demand for potable water and paucity of fresh water resources, this process has gained special importance. Conventional Thermal Desalination processes involves evaporative methods such as multi-stage flash and solar distils, which are found to be energy intensive, whereas reverse osmosis based systems have high operating and maintenance costs. The present work describes the Adsorption Desalination (AD) system, which is an emerging process of Thermal Desalination cum refrigeration capable of utilizing low grade heat easily obtainable from even non-concentrating type solar collectors. The system employs a combination of flash evaporation and Thermal compression to generate cooling and desalinated water. The current study analyses the system dynamics of a 4-bed single stage silica-gel plus water based AD system. A lumped model is developed using conservation of energy and mass coupled with the kinetics of adsorption/desorption process. The constitutive equations for the system components viz. evaporator, adsorber and condenser, are solved and the performance of the system is evaluated for a single stage AD system at various condenser temperatures and cycle times to determine optimum operating conditions required for Desalination and cooling. (C) 2013 P. Dutta. Published by Elsevier Ltd.
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Solar driven Adsorption Desalination system
2013Co-Authors: S Mitra, K Srinivasan, S. S. Murthy, P. Kumar, P. DuttaAbstract:Desalination is one of the most traditional processes to generate potable water. With the rise in demand for potable water and paucity of fresh water resources, this process has gained special importance. Conventional Thermal Desalination processes involves evaporative methods such as multi-stage flash and solar distils, which are found to be energy intensive, whereas reverse osmosis based systems have high operating and maintenance costs. The present work describes the Adsorption Desalination (AD) system, which is an emerging process of Thermal Desalination cum refrigeration capable of utilizing low grade heat easily obtainable from even non-concentrating type solar collectors. The system employs a combination of flash evaporation and Thermal compression to generate cooling and desalinated water. The current study analyses the system dynamics of a 4-bed single stage silica-gel plus water based AD system. A lumped model is developed using conservation of energy and mass coupled with the kinetics of adsorption/desorption process. The constitutive equations for the system components viz. evaporator, adsorber and condenser, are solved and the performance of the system is evaluated for a single stage AD system at various condenser temperatures and cycle times to determine optimum operating conditions required for Desalination and cooling. © 2013 P. Dutta.
Fawzi Banat - One of the best experts on this subject based on the ideXlab platform.
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Solar Thermal Desalination technologies
2008Co-Authors: Hazim Mohameed Qiblawey, Fawzi BanatAbstract:The use of solar energy in Thermal Desalination processes is one of the most promising applications of the renewable energies. Solar Desalination can either be direct; use solar energy to produce distillate directly in the solar collector, or indirect; combining conventional Desalination techniques, such as multistage flash Desalination (MSF), vapor compression (VC), reverse osmosis (RO), membrane distillation (MD) and electrodialysis, with solar collectors for heat generation. Direct solar Desalination compared with the indirect technologies requires large land areas and has a relatively low productivity. It is however competitive to the indirect Desalination plants in small-scale production due to its relatively low cost and simplicity. This paper describes several Desalination technologies in commercial and pilot stages of development. The primary focus is on those technologies suitable for use in remote areas, especially those which could be integrated into solar Thermal energy systems. © 2008.