Beyond energy density: flow battery design driven by safety and location

Abstract

As renewable energy penetration increases, energy storage is becoming urgently needed for several purposes, including frequency control, peak shifting, and relieving grid congestion. While battery research often focuses on cell level energy density, other aspects of large-scale battery energy storage systems, such as footprint, safety, and storage-duration are frequently overlooked. Here, we investigate forty-four MWh-scale battery energy storage systems via satellite imagery and show that the building footprint of lithium-ion battery systems is often comparable to much less energy-dense technologies such as aqueous flow batteries. We show that due to their intrinsic safety, aqueous chemistries can be built more vertically, enabling smaller footprints, and unlocking new use cases. Transmission constraints for example have a growing impact on energy prices and grid stability, and due to regulatory and practical challenges limiting the addition of more transmission capacity, storage deployed in strategic locations can play a critical role in mitigating grid congestion. Such grid-nodes are often found near energy consumers, where land cost and safety concerns are significant. Deployments in urban areas to locally mitigate congestion and installations in buildings or underground thus provide compelling value propositions for aqueous battery chemistries beyond direct competition with lithium-ion batteries near renewable generation sites.