Performance limiting effects in power generation from salinity gradients by pressure retarded osmosis.
Performance limiting effects in power generation from salinity gradients by pressure retarded osmosis.
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DOI：
10.1021/es203197e
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发表时间：
2011-11
影响因子：
11.4
通讯作者：
Ngai Yin Yip;M. Elimelech
中科院分区：
文献类型：
--
作者：
Ngai Yin Yip;M. Elimelech
压力延迟渗透有潜力利用淡水流入海洋时混合的自由能量进行清洁和可再生发电。在此，我们系统地研究了缓压渗透中的性能限制现象——外部浓度极化、内部浓度极化和反抽盐通量，并对高性能缓压渗透发电系统的设计标准提出了见解。对聚酰胺薄膜复合膜进行了化学改性，使其具有一系列的膜传输性能，并对其水和盐的渗透性进行了表征，以确定潜在的渗透性-选择性权衡关系。我们表明，功率密度受到膜活性层的渗透性和选择性之间的权衡的限制。这种行为归因于膜透水性的有利作用和反向盐通量耦合内部浓度极化的不利影响的相反影响。我们的分析揭示了活性层和支撑层性质对功率密度的复杂影响，并表明通过根据结构参数调整水和盐渗透率来最大化膜的性能。采用一个分析参数，量化每个性能限制现象的相对影响，以确定限制生产率的主导效应。在高功率密度下，外聚光极化是限制性能的主要因素。膜进料通道中流体动力流动条件的增强减少了外部浓度极化，从而提高了功率密度。然而，由于随之而来的液压损失，这样做也会产生额外的运营成本。本研究表明，通过对膜性能和水动力条件的精心选择，可以有条不紊地将限制压力延迟渗透发电过程生产力的有害影响降至最低，以实现高性能。
Pressure retarded osmosis has the potential to utilize the free energy of mixing when fresh river water flows into the sea for clean and renewable power generation. Here, we present a systematic investigation of the performance limiting phenomena in pressure retarded osmosis--external concentration polarization, internal concentration polarization, and reverse draw salt flux--and offer insights on the design criteria of a high performance pressure retarded osmosis power generation system. Thin-film composite polyamide membranes were chemically modified to produce a range of membrane transport properties, and the water and salt permeabilities were characterized to determine the underlying permeability-selectivity trade-off relationship. We show that power density is constrained by the trade-off between permeability and selectivity of the membrane active layer. This behavior is attributed to the opposing influence of the beneficial effect of membrane water permeability and the detrimental impact of reverse salt flux coupled with internal concentration polarization. Our analysis reveals the intricate influence of active and support layer properties on power density and demonstrates that membrane performance is maximized by tailoring the water and salt permeabilities to the structural parameters. An analytical parameter that quantifies the relative influence of each performance limiting phenomena is employed to identify the dominant effect restricting productivity. External concentration polarization is shown to be the main factor limiting performance at high power densities. Enhancement of the hydrodynamic flow conditions in the membrane feed channel reduces external concentration polarization and thus, yields improved power density. However, doing so will also incur additional operating costs due to the accompanying hydraulic pressure loss. This study demonstrates that by thoughtful selection of the membrane properties and hydrodynamic conditions, the detrimental effects that limit productivity in a pressure retarded osmosis power generation process can be methodically minimized to achieve high performance.