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Available from: Daiwon Choi, Jul 01, 2015
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    ABSTRACT: Sea water intrusion causes fresh water shortage on small islands, and desalination systems are needed to desalt the salinated water (brackish water) and produce fresh water. Unfortunately conventional desalination technologies can only work properly with stable external power inputs, which are usually not accessible in these rural areas. In this study we propose an integrated self-desalination stack that consists of alternate anion and cation ion exchange membranes and couples the technologies of reverse electrodialysis and electrodialysis. The salinity gradient energy between sea water and brackish water is harvested to demineralize another portion of brackish water directly in the same stack. The overall process is spontaneous and energy self-sufficient with minimum peripheral devices, and it is promising to provide fresh water supply especially for these rural residents on small islands.
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    ABSTRACT: Two and three dimensional modeling of a single cell of vanadium redox flow battery has been done thoroughly according to electrochemical and fluid mechanic equations in this study. The modeling has been done in stationary state and its results have been presented in three chemical, electrical and mechanical sub models. The parametric analysis on some of important factors in cell operation demon-strated that increase in electrode and membrane conductivity and electrode porosity contributes to electric potential increase in cells. Also operational temperature increase leads to decrease in cells' voltage. Better fluid distribution on the electrode surface area results in better cell operation, therefore the electrolyte flow distribution form in cell has been studied by designing different flow frames. Modified Navier-Stokes equations have been used in these calculations for porous media. The most coverage on electrode surface and low pressure loss had been the best case criteria. Key words: Vanadium redox battery / stationary model / computational fluid dynamic / porous media / electrolyte distribution
    01/2015; 16(201). DOI:10.1051/meca/2014071
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    ABSTRACT: The viscosity of the electrolyte in vanadium redox flow batteries (VRFBs) varies during charge and discharge as the concentrations of acid and vanadium ions in the electrolyte continuously change with the state of charge (SOC). In previous VRFB models, however, the electrolyte has been treated as a constant-viscosity solution. In this work, a mass-transport and electrochemical model taking account of the effect of SOC-dependent electrolyte viscosity is developed. The comparison between the present model and the model with the constant-viscosity simplification indicates that the consideration of the SOC-dependent electrolyte viscosity enables (i) a more realistic simulation of the distributions of overpotential and current density in the electrodes, and (ii) more accurate estimations of pumping work and the system efficiency of VRFBs.
    Applied Energy 10/2014; 130:139–147. DOI:10.1016/j.apenergy.2014.05.034 · 5.26 Impact Factor