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CAER Seminars

All-Vanadium Flow Batteries for Large-Scale Energy Storage

Speaker:
D. Noel Buckley
University of Limerick, Ireland

Date:
May 28, 2015 at 10:00am
Ben Bandy Conference Center
UK Center for Applied Energy Research

Abstract:

The use of non-dispatchable sources of renewable energy such as solar, wind and ocean is increasing but is restricted unless there is a means of storing the energy. All-Vanadium flow batteries (VFBs) are an attractive technology for such applications. They have a major advantage over other flow batteries in that cross-contamination due to transport through the separating membrane is effectively eliminated. Typical cells have carbon felt electrodes separated by a proton exchange membrane and the electrolytes are circulated through the electrodes from reservoirs. Both electrolytes are highly acidic, typically 3 mol dm-3 H2SO4.

The active species in the catholyte are VO2+ and VO2 + (i.e. VIV and VV) while the active species in the anolyte are V3+ and V2+. All four species are highly colored, having strong absorbance spectra in the visible region. Thus, ultraviolet-visible (UV-Vis) spectroscopy offers a precise method of independently measuring the state of charge (SoC) of both the positive and the negative half-cells of VFBs. Independent monitoring of the SoC of both electrolytes is important for effective operation of VFB technology.

Spectrophotometric methods are straightforward when the absorbance of mixtures is a linear combination of that of the constituents. Such linearity has been demonstrated for the anolyte. In the catholyte, however, the absorbance behaves linearly only for very dilute solutions; at the concentrations used in a VFB the behaviour is highly non-linear. Thus, it had been suggested in the literature that UV-Vis spectroscopic monitoring of the positive electrolyte is not feasible. However, we have shown that the spectroscopic behavior can be analyzed with considerable precision once the underlying solution chemistry is understood. In this talk, I will discuss the underlying spectroscopy and address practical issues of determining SoC from spectroscopic measurements.

About the Speaker:

D. Noel Buckley is Professor of Physics at the University of Limerick, Ireland. He is a Past- President and a Fellow of ECS. He has served as an Associate Editor of both The Journal of the Electrochemical Society and Electrochemical and Solid State Letters. He is a member of the Editorial Advisory Board of ECS Transactions and has served as Chair of the European Section, and as Chair, Secretary and Treasurer of the Electronics and Photonics Division.

Dr. Buckley was a Member of Technical Staff at Bell Laboratories, Murray Hill, NJ (1979– 1996) where he initially worked on the development of rechargeable lithium batteries and subsequently played a key role in the epitaxial crystal growth and characterization of compound semiconductor films for high performance optoelectronic devices.