(Invited) The Pathway to Widespread Commercialization of Redox Flow Batteries

Abstract

Large-scale electric-energy-storage (EES) systems have the potential to transform the electric grid. The deployment of recent EES systems have predominately been Li-ion batteries (LiBs), which are being used primarily for Ancillary Services (e.g., frequency regulation) and other grid applications (e.g., load following) that require relatively short discharge durations (i.e., ≤ 4-h at rated power). At these relatively low energy/power ratios, LiBs can be lower cost than the historical EES baseline, which is pumped-storage hydropower (PSH). However, since the cost of most conventional batteries scales linearly with energy capacity, the energy-storage cost ($/kWh) is not necessarily lower for uses that require longer discharge times. For these long-duration energy-storage (LDES) applications (i.e., ≥ 5-h at rated power), EES systems with independent power and energy components, e.g., PSH, redox flow batteries (RFBs), reversible fuel cells, and electrofuels, have an inherent cost advantage, since one can readily increase the energy/power ratio by selectively adding more energy capacity, without the added cost of excessive power components. LDES applications have the potential to be a substantially larger market than short-duration EES; however, the requirements for LDES systems are also inherently more challenging. The primary commercialization challenge is capital cost (i.e., $/kWh installed). In addition to fully decoupled power and energy, RFBs have other unique attributes that make this battery architecture ideally suited for grid-scale LDES, namely: long cycle life even with deep cycles, inherently superior safety, and easy recyclability. Largo Clean Energy (LCE) is a vertically-integrated developer of all-V RFBs (VRFBs), and LCE’s MW-scale product is arguably the most advanced RFB system available on the market today. This talk will primarily focus on: 1) what LCE has already done to substantially reduce the cost of VRFBs, 2) how VRFBs can potentially enable the commercialization of other types of RFB systems, and 3) future opportunities to further reduce the capital cost of a variety of RFB systems. Acknowledgements Many thanks to my flow-battery collaborators at Largo Clean Energy and at Raytheon Technologies Research Center (formerly known as UTRC), as well as many other outstanding colleagues on multiple UTRC-led ARPA-E projects and JCESR collaborations on flow batteries.