Method for determining the state of charge of a vanadium redox flow battery

Patent metadata

Field	Value
Publication number	US-2016372777-A1
Application number	US-201415101092-A
Country	US
Kind code	A1
Filing date	Dec 2, 2014
Priority date	Dec 2, 2013
Publication date	Dec 22, 2016
Grant date	—

Abstract

The invention relates to a method for determining V IV or V V concentration in mixtures of V IV and V V solutions, the method comprising the steps of determining the absorbance of the solution at at least one wavelength; and calculating the concentration of the V IV and V V solution based on the absorbance. In one embodiment the V IV , V V and/or total vanadium concentration in a solution is calculated based on the fact that the absorbance at a specific wavelength can be predicted by taking into account the formation of vanadium complexes.

First claim

1 . A method for determining V IV or V V concentration in a mixture of V IV and V V solution, the method comprising the steps of:
determining the absorbance of the solution at least one wavelength; and calculating the concentration of the V IV and/or V V solution based on the absorbance.

2 . The method of claim 1 , wherein the overall vanadium concentration in the solution is known and where a non-proportional relationship exists between the vanadium species concentration and absorbance due to the presence of complexes between V IV and V V , wherein the step of calculating the concentration of the V IV and/or V V solution based on the absorbance comprises the steps of:
comparing the absorbance against a look-up graph of absorbance versus fraction of V V for at least one wavelength and for the same overall vanadium concentration; and estimating the fraction of V IV and/or V V in the solution from the comparison.

3 . The method of claim 2 further comprising:
determining the absorbance of the solution at least one alternative wavelength;
comparing the absorbance against a look-up graph of absorbance versus fraction of V V for the at least one alternative wavelength and for the same overall vanadium concentration; and
estimating the fraction of V IV and/or V V in the solution from the comparison performed at the at least one wavelength and the comparison performed at the at least one alternative wavelength.

4 . The method of claim 2 further comprising estimating the fraction of V IV and/or V V in the solution from the comparison performed at the at least one wavelength and based on one or more of: positive state of charge, SoC, negative SoC, cell voltage or the change in absorbance when charging or discharging of the electrolyte.

5 . The method of claim 2 , wherein the look-up graph of absorbance versus fraction of V V for a given wavelength is constructed by the steps of:
determining for the given wavelength the absorbance of a V IV solution of a known concentration; and determining for the given wavelength the absorbance of a calibration sample of V IV /V V solution of a known mixture ratio and a known concentration.

6 . The method of claim 5 , wherein two calibration samples of V IV -V V mixtures of known concentration and mixture ratio are used for the construction of the look-up graph.

7 . The method of claim 5 , wherein a solution whose V IV /V V mixture ratio can be changed in a controlled manner is used for calibration, and wherein the calibration comprises changing the mixture ratio and comparing the change in mixture ratio to the absorbance of the solution.

8 . (canceled)

9 . The method of claim 1 , wherein the overall vanadium concentration is known and where a non-proportional relationship exists between vanadium species concentration and absorbance due to the presence of complexes between V IV and V V , wherein the step of calculating the concentration of the V IV and/or V V solution based on the absorbance comprises the steps of:
determining the ratio of excess absorbance for a pair of specific wavelengths; and estimating the concentration of V IV and/or V V by solving simultaneous equations based on the determined ratio of excess absorbance for the pair of specific wavelengths.

10 . The method of claim 1 , wherein the overall vanadium concentration is not known and, wherein the concentration of vanadium or the concentration of the V IV and/or V V solution is calculated by:
determining the ratio of excess absorbance for two pairs of specific wavelengths; and estimating the concentration of vanadium, V IV and/or V V by solving simultaneous equations based on the determined ratio of excess absorbance for the two pairs of specific wavelengths.

11 . The method of claim 9 , wherein the equation for the simultaneous equations comprises

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Assignees

• Univ Limerick

Inventors

• Buckley Denis Noel
• Gao Xin
• Lynch Robert Patrick
• Leahy Martin J
• Bourke Andrea
• Flynn Grace

Classifications

• G01N2021/1748

  Comparative step being essential in the method · CPC title

• G01N21/31

  Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry {(G01N21/72 takes precedence)} · CPC title

• G01R31/367

  Software therefor, e.g. for battery testing using modelling or look-up tables · CPC title

• H01M8/04477

  of the electrolyte · CPC title

• H01M8/0444

  Concentration; Density (H01M8/04492 takes precedence) · CPC title