Osmotic Power Generation by Inner Selective Hollow Fiber Membranes: An investigation of thermodynamics, mass transfer, and module scale modelling

Abstract
A comprehensive analysis of fluid motion, mass transport, thermodynamics and power generation during pressure retarded osmotic (PRO) processes was conducted. This work aims to (1) elucidate the fundamental relationship among various membrane properties and operation parameters and (2) analyse their individual and combined impacts on PRO module performance. A state-of-the-art inner-selective thin-film composite (TFC) hollow fiber membrane was employed in the modelling. The analyses of mass transfer and Gibbs free energy of mixing indicate that the asymmetric nature of hollow fibers results in more significant external concentration polarization (ECP) in the lumen side of the inner-selective hollow fiber membranes. In addition, a trade-off relationship exists between the power density (PD) and the specific energy (SE). The PD vs. SE trade-off upper bound may provide a useful guidance whether the flowrates of the feed and draw solutions should be further optimized in order to (1) minimize the boundary thickness and (2) maximize the osmotic power generation. Two new terms, mass transfer efficiency and power harvesting efficiency for osmotic power generation, have been proposed. This work may provide useful insights to design and operate PRO modules with enhanced performance so that the PRO process becomes more promising in real applications in the near future.

Citation
Xiong JY, Cai DJ, Chong QY, Lee SH, Chung T-S (2016) Osmotic Power Generation by Inner Selective Hollow Fiber Membranes: An investigation of thermodynamics, mass transfer, and module scale modelling. Journal of Membrane Science. Available: http://dx.doi.org/10.1016/j.memsci.2016.12.056.

Acknowledgements
This work is granted by the Singapore National Research Foundation under its Environmental & Water Research Programme and administered by PUB, Singapore’s national water agency. It is funded under the projects entitled

Publisher
Elsevier BV

Journal
Journal of Membrane Science

DOI
10.1016/j.memsci.2016.12.056

Additional Links
http://www.sciencedirect.com/science/article/pii/S0376738816323444

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