Interest in the development of redox-flow batteries (RFBs) for large-scale grid storage is growing, and considerable investments have been made into the research and development of RFBs over the past few decades. Unfortunately, practical implementation has been hampered by various cost and performance issues typical of an immature state of development. One critical factor for the competitiveness of this technology is the installed cost. In this work, we incorporate recent developments in all-vanadium RFB research and present an analysis of the associated cost factors. The major components of a RFB that affect installed cost are identified and used as variables to create a capital cost function. The function is then used to calculate the rate of change of the capital costs with respect to the major components. The capital costs are also calculated for a range of component values and plotted. Key findings include a high sensitivity of system capital cost to purity of vanadium and substantial fractions of the cost associated with perflurorosulfonic acid membranes currently used for proton transport.

Samples of porous glass of 38 Å average pore size are prepared with the use of the sol-gel technique. After stabilizing at 800°C, samples are impregnated with various binary mixtures and Raman spectroscopy is used to analyze the composition of the mixtures inside the pores. In order to study the effect of surface interaction on preferential adsorption, the experiments are repeated for samples of modified surfaces. It is shown that surface interactions are important and they determine the excess adsorption. The diffusion rate inside porous glass is also measured and it is shown to depend on surface interactions.

A computational model is developed to calculate thermodynamic phase equilibria in aqueous solutions of fluoride, phosphate, and hydroxide up to 100 °C. A variety of data are used, including isopiestic and electromotive force measurements, freezing point data, vapor pressure data at 100 °C, heat capacities, heats of dilution, and solubility measurements. Pitzer's ion-interaction treatment is used to model electrolyte solutions, and many unknown parameters are determined from existing data through nonlinear least-squares fitting. Phase equilibria are determined by minimization of the total Gibbs energy using a modification of the code SOLGASMIX. Results calculated using the model accurately predict phase equilibria from many quantitative experiments. Qualitative experiments are performed to evaluate calculated solubilities in regions of sparse or nonexistent data; the calculated results are reasonable and exhibit a general qualitative agreement with such data. Model predictions are useful in understanding problems that may arise in the treatment of waste streams containing fluoride and phosphate anions in highly caustic solutions.

Interest in the development of redox-flow batteries (RFBs) for large-scale grid storage is growing, and considerable investments have been made into the research and development of RFBs over the past few decades. Unfortunately, practical implementation has been hampered by various cost and performance issues typical of an immature state of development. One critical factor for the competitiveness of this technology is the installed cost. In this work, we incorporate recent developments in all-vanadium RFBs research and present an analysis of the associated cost factors. The major components of a RFB that affect installed cost are identified and used as variables to create a capital cost function. The function is then used to calculate the rate of change of the capital costs with respect to the major components. The capital costs are also calculated for a range of component values and plotted. Key findings include a high sensitivity of system capital cost to purity of vanadium and substantial fractions of the cost associated with perflurorosulfonic acid membranes currently used for proton transport. IntroductionRedox flow batteries (RFBs) are being developed for use in large-scale electrical grid storage. There are a number of potential benefits that could be provided by large-scale electrical grid storage RFBs. RFBs could be used to store energy during periods of low damand and supply power during periods of peak demand, forgoing the need for additional expensive investments in generating capacity to meet peak demand. Also electrical energy generated from renewable resources such as wind or solar could be stored in a RFB for use when supplies of renewable power are limited. RFBs could help stabilize transmission lines, act as an uninterruptable power supply for sensitive equipment, and improve service reliability for customers (1). But in spite of research and development over the past few decades, practical implementation is hampered by various cost and performance issues typical of an immature state of development of the technology.One critical factor for competitiveness of this technology is its installed (capital) cost. ARPA-e targets capital costs of $100/kWh installed, an aggressive target for lowering the capital costs. Analysis is needed to consider if it is even feasible to meet this kind of target with current technology and to evaluate the changes that are most likely to result in large reductions in capital cost. Thus, economic analyses can provide focus to research activities. For example, the trade-off in cost between factors primarily associated with energy density (redox couples, achievable concentrations of electrolyte solutions) and electrical power density (electrochemical converter performance) will provide insight into appropriate priorities for different deployment scenarios.In this work, we present an analysis of the cost factors associated with vanadium redox flow batteries (VRBs), which are widely viewed as a possible target technology. We previously analyzed VRB systems using chemical pr...

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