In recent years, the deployment of renewable energy sources, development of smart grid technology and advances in electrified transportation have resulted in a surge in markets for large-scale stationary energy storage. Several factors contribute to the demand for large-scale energy storage, including capital costs of managing peak demands, integration of renewable energy sources and investments needed for grid reliability. Although hydroelectric is one of the most common types of energy storage, flow batteries offer a much more desirable alternative, due to scalability and location flexibility. A number of studies and demonstration projects have been carried out in the field of flow batteries, in particular with the vanadium ^[1,4], and iron/chromium^[2-4] chemistries and these and other systems are in the first stages of commercial deployment. In this presentation we will discuss the scale-up an all iron flow battery, focusing on two issues in particular, flow distribution and hydrogen generation/recombination.

Flow distribution is a scaling concern in all flow battery systems both on a cell to cell level within a stack and within an individual cell. This investigation utilizes the all iron chemistry to investigate the effects of flow distribution within a single cell on cell performance and the pressure drop associated pumping costs of achieving a more even flow distribution within a cell. These effects are considered in the context of transitioning from a 50cm² lab scale cell to a 1100cm² commercial scale prototype. An optimization can be achieved between flow uniformity and pumping losses.

Hydrogen evolution is a parasitic reaction in many chemistries that can have a significant effect on lifetime. We have developed a simple in-tank system that captures and re-oxidizes hydrogen to maintain electrolyte stability and demonstrated this concept on a laboratory scale.^[5] This investigation looks into scaling considerations and their effect on the hydrogen recombination system. Specifically, the relationship between head space, gas recirculation and the effectiveness of the reactor are considered.

[1] G. Codina, J. Perez, M. Lopez-Atalaya, J. Vasquez, and A. Aldaz, J. Power Sources, 48, 293 (1994).

[2] S. Takahashi and T. Hiramatsu, J. Power Sources, 17, 55 (1986).

[3] M. Futamata, S. Higuchi, O. Nakamura, I. Ogino, Y. Takada, and S. Okazaki, J. Power Sources, 24, 137 (1988).

[4] M. Skyllas-Kazacos, M. H. Chakrabarti, S. A. Hajimolana, F. S. Mjalli and M. Saleem, J. Electrochem.Soc., 158, 8 (2011).

[5] S, Selverston, R. F. Savinell and J. S. Wainright, J. Power Sources., 324, 674, (2016).