Current losses in a bipolar cell—an analysis of the Tafel regime

A model for predicting shunt/leakage currents in a bipolar electrolyzer stack with dual electrolyte inlets and significant amount of gases in the outlet ports and manifold is presented. Model includes electrolyte, manifold and membrane separator as resistance components in the electric circuit analog of the stack. Activation overvoltage associated with electrodes is taken as Tafel-like. Current balance and potential balance equations are applied to the stack and difference calculus is employed to reduce the problem to a set of linear difference equations with constant coefficients. The model is validated with published results and the effect of each resistance component and number of cells on leakage currents in the stack is presented.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Prediction of shunt currents in a bipolar electrolyzer stack by difference calculus

Jupudi,

Zappi,

Bourgeois

2007

“…Bonvin et al [12,13] solved the Laplace equation using the finite element method for a bipolar electrochemical reactor and reported experimental results of current distributions. Rangarajan et al [14] assumed Tafel kinetics and the complex system of equations was solved by means of different methods.…”

Section: Introductionmentioning

confidence: 99%

Simplified model to predict the effect of the leakage current on primary and secondary current distributions in electrochemical reactors with a bipolar electrode

Henquín

Bisang

2005

A simplified mathematical model to calculate the current distributions in bipolar electrochemical reactors is proposed. The current distributions are deduced from a combination of the voltage balance in the reactor with a voltage balance including the electrolyte inlet and outlet. Thus, equations to predict the effect of geometric and operational variables on the current distributions at the electrodes are reported. The parameters acting upon the current distributions were lumped into two dimensionless variables and their effects on the current distributions are discussed. The primary current distributions are obtained as a limiting case. Comparisons between calculated and experimental primary current distributions are reported. List of symbolsA transverse section of the electrolyte manifold (m 2 ) b i constant in the Tafel equation of the ith reaction (i= a or c) (V) C 1 constant given by Equation 7 (V) C 2 constant given by Equation 13 (V) d r mean relative deviation (%) e interelectrode distance (m)

“…Generally the electrolyte is fed to the individual bipolar cells via inlet and outlet manifolds; and leakage currents, also called parasitic, shunt or by-pass currents, flowing through the connecting manifolds and pipes diminish the current efficiency of the bipolar cell stack. Several authors [1][2][3][4][5][6][7][8][9][10][11][12] reported procedures for calculating leakage currents and current efficiency but little attention was paid to the effect of leakage currents on the potential and current distribution in terminal and bipolar electrodes. Thus, Divisek et al [13] computed the potential profile in electrolysers by numerical solution of the Laplace equation using the finite difference method.…”

mentioning

confidence: 99%

Effect of leakage currents on the primary current distribution in bipolar electrochemical reactors

Henquín

Bisang

2007

The primary current distribution in a bipolar electrochemical reactor with outside inlet and outlet electrolyte manifolds was investigated by numerical solution of the Laplace equation and by experimental measurement in simulated cells made from conductive paper and segmented electrodes. The geometric parameters determining the distribution were the interelectrode gap, electrode length, transverse section and length of the electrolyte manifold. The effect of the number of electrodes in the bipolar stack was also analysed. Values obtained numerically have been compared with those obtained experimentally and a good agreement is observed between them. These results are useful for estimating the performance of the bipolar stack. List of symbols aGeometric parameter of the manifold (m) A Transverse section of the electrolyte manifold (m 2 ) bGeometric parameter of the manifold (m) d r Mean relative deviation (%) eInterelectrode gap (m) G Length of the electrolyte manifold (m) jCurrent density (A m -2 ) j mean Mean current density (A m -2 )