In this paper, we present a study of the effect of electrode intrusion into the flow channel in an all-vanadium redox flow battery. Permeability, pressure drop and electrochemical performance have been measured in a cell with active area 100 cm2and 414 cm2 fitted with a carbon felt electrode of thickness of 3, 6 or 9 mm compressed to 1.5, 2.5 or 4 mm, respectively, during assembly. Results show that the pressure drop is significantly higher than what can be expected in the thick electrode case while its electrochemical performance is lower. Detailed flow analysis using computational fluid dynamics simulations in two different flow fields shows that both these results can be attributed to electrode intrusion into the flow channel leading to increased resistance to electrolyte flow through the electrode. A correlation is proposed to evaluate electrode intrusion depth as a function of compression. © 2017 Elsevier B.V.

Sreenivas Jayanti

Department Of Chemical Engineering

Shyam G.Ravi Kumar

carbon

Channel flow

Computational fluid dynamics

Drops

Electric batteries

Electrodes

Electrolytes

FLOW BATTERIES

Flow fields

Mercury (metal)

Pressure drop

Vanadium

ALL VANADIUM REDOX FLOW BATTERY

Computational fluid dynamics simulations

Electrochemical performance

ELECTROLYTE CIRCULATIONS

ELECTROLYTE FLOWS

Power densities

THICK ELECTRODES

VANADIUM REDOX FLOW BATTERIES

Electrochemical electrodes

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Journal of Power Sources

For high current density operation of redox flow batteries, proper circulation of the electrolytes over the active area of the cell is important. In the present paper, we study experimentally the effect of channel dimensions of a serpentine flow field for vanadium redox flow battery applications. The study encompasses three aspects: effect on the extent of felt intrusion into the flow channels, effect on the pressure drop over a cell for a given electrolyte circulation rate, and effect on the electrochemical performance characterized by a number of parameters. Eight variants of channel and/or rib dimensions in serpentine flow fields have been studied in cells of 400 cm 2 and 900 cm 2 active area. A lumped parameter model, validated with water and electrolyte circulation data, has been developed to predict the pressure loss and flow apportionment in the cell. The results show that sensitivity to channel dimensions is more keenly felt in the larger cell with noticeable improvements in pressure drop, peak power density and discharge energy density. Increasing channel width and decreasing rib width is recommended as the ideal strategy to improve the overall performance of the cell. © 2019 Elsevier Ltd

Journal of Energy Storage

Effect of channel dimensions of serpentine flow fields on the performance of a vanadium redox flow battery

Studies in small cells of vanadium redox flow battery have shown electrode compression to have significant effect on the cell performance. However, the results are conflicting and the data have been obtained for very high electrolyte circulation rates. In the present study, experimental investigations have been conducted in vanadium redox flow battery cells of active area of 426 cm2 and 936 cm2 over a wide range of operating conditions typical of large cells and for electrode compressions of 20, 35, 50 and 70%. The influence of operating current density, electrolyte circulation rate and state of charge has been specifically studied for both cell sizes. Cell pressure drop studies have also been conducted. Results show that the beneficial effects of electrode compression are mostly nullified by the loss of permeability at current densities in the range of 30–60 mA cm−2. At higher current densities, intermediate compressions of 35 and 50% are found to be the most optimal. Low state of charge tolerance is found to be better for the larger cell than the smaller cell, presumably due to better convective transport of electrolyte through the electrode arising from higher pressure drop. © 2019 Elsevier B.V.

Effect of electrode compression and operating parameters on the performance of large vanadium redox flow battery cells

A comparative study of the electrochemical energy conversion performance of a single-cell all-vanadium redox flow battery (VRFB) fitted with three flow fields has been carried out experimentally. The charge-discharge, polarization curve, Coulombic, voltage and round-trip efficiencies of a 100 cm2 active area VRFB fitted with serpentine, interdigitated and conventional flow fields have been obtained under nearly identical experimental conditions. The effect of electrolyte circulation rate has also been investigated for each flow field. Stable performance has been obtained for each flow field for at least 40 charge/discharge cycles. Ex-situ measurements of pressure drop have been carried out using water over a range of Reynolds numbers. Together, the results show that the cell fitted with the serpentine flow field gives the highest energy efficiency, primarily due to high voltaic efficiency and also the lowest pressure drop. The electrolyte flow rate is seen to have considerable effect on the performance; a high round-trip energy efficiency of about 80% has been obtained at the highest flow rate with the serpentine flow field. The data offer interesting insights into the effect of electrolyte circulation on the performance of VRFB. © 2016 Elsevier B.V. All rights reserved.

Effect of flow field on the performance of an all-vanadium redox flow battery

Electrolyte distribution using parallel flow field for redox flow battery (RFB) applications shows severe non-uniformity, while the conventional design of using the carbon felt itself as the flow distributor gives too high pressure drop. An optimized flow field design for uniform flow distribution at a minimal parasitic power loss is therefore needed for RFB systems. Since the materials and geometrical dimensions in RFBs are very different from those used in fuel cells, the hydrodynamics of the flow fields in RFBs is likely to be very different. In the present paper, we report on a fundamental study of the hydrodynamics of a serpentine flow field relevant to RFB applications. The permeability of the porous medium has been measured under different compression ratios and this is found to be in the range of 5-8 × 10-11 m2. The pressure drop in two serpentine flow fields of different geometric characteristics has been measured over a range of Reynolds numbers. Further analysis using computational fluid dynamics simulations brings out the importance of the compression of the porous medium as an additional parameter in determining the flow distribution and pressure drop in these flow fields. © 2013 Elsevier B.V. All rights reserved.

Ex-situ experimental studies on serpentine flow field design for redox flow battery systems

Electrolyte flow distribution is an important factor that contributes to the performance of the overall efficiency of a redox flow battery system. In the present paper, a comparative study of the hydrodynamics of the serpentine and interdigitated flow fields has been performed. Ex situ experiments were conducted using the two flow fields in conditions typical of flow battery applications. Limited in situ testing has also been conducted. These bring out the surprising result that the pressure drop in the interdigitated flow field is less than that in the serpentine for the same flow rate. Computational fluid dynamics studies show strong under-the-rib convection in the reaction zone exists in both flow fields but with a shorter residence time in case of the interdigitated. It is posited that this may explain the superior electrochemical performance of cells with interdigitated flow fields. © 2014 Springer Science+Business Media Dordrecht.

Journal of Applied Electrochemistry

Hydrodynamic analysis of flow fields for redox flow battery applications Batteries

The paper describes a flow field design which is based on the improvement of the local cross-flow conditions in a split serpentine flow field. The layout of the flow field is such that the cross-flow is higher in the oxygen-depleted portion of the adjacent serpentine channel in a split serpentine flow field with more than one serpentine channels. The present arrangement offers the quadruple advantage of uniform reactant distribution over the entire cell active area; low overall pressure drop, thereby reducing the parasitic power losses; effective liquid water evacuation in the U-bends; and more oxygen replenishment in the oxygen-deficient portions of the serpentine channel. Computational fluid dynamics (CFD) and experimental analysis carried out on the proposed design with three serpentine channels confirm the benefits. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.

International Journal of Hydrogen Energy

An improved serpentine flow field with enhanced cross-flow for fuel cell applications

Serpentine flow-fields have long been used in polymer electrolyte membrane (PEM) fuel cells for effective transportation of reactants from the flow-field to the reaction sites. It has been observed in the literature that localized flooding near the U-bend region of serpentine flow-fields occurs at high current densities. This has been attributed to the boundary layer separation and recirculation of flow in the U-bend. In the present study, it is established, using computational fluid dynamics (CFD) simulations, that this is due to lower channel-to-channel cross-flow in the electrodes between consecutive serpentine channels rather than to the flow-field in the gas distribution channels. © 2008 Elsevier B.V. All rights reserved.

Effect of channel-to-channel cross-flow on local flooding in serpentine flow-fields

Effect of electrode intrusion on pressure drop and electrochemical performance of an all-vanadium redox flow battery

Journal	Data powered by TypesetJournal of Power Sources
Publisher	Data powered by TypesetElsevier B.V.
ISSN	03787753
Open Access	No