US organic flow battery startup XL Batteries partners with Prometheus Hyperscale to power data centres

May 15, 2025
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Flow battery developer XL Batteries has partnered with data centre developer Prometheus Hyperscale to deploy its batteries on-site at data centres.

The companies have made a multi-year agreement to use XL’s organic long-duration energy storage (LDES) flow battery technology.

Phase one of this partnership will see XL commission a 333kW demonstration-scale battery system at a Prometheus facility in 2027.

Next, Prometheus plans to purchase a 12.5MW/125MWh commercial-scale system in 2028 followed by another 12.5MW/125MWh system in 2029.

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Both companies say they are aligned for long-term deployments of XL’s technology at Prometheus data centres.

The companies also note that, according to a report from Goldman Sachs, global power demand from data centres is forecasted to increase by as much as 165% by 2030. 

They say on-site energy storage will be pivotal in helping data centre operators maintain operations, and that XL’s non-lithium technology will further ensure site safety.

In April, XL commissioned its first organic flow battery in a pilot project with global storage terminals provider Stolthaven Terminals, at Stolthaven’s Houston, Texas facility.

XL Batteries co-founder and CEO Dr. Thomas Sisto said the goal of that deployment was to generate operational data to compare the company’s systems against vanadium-based flow batteries.

As the co-founder and CEO recently explained in an interview with ESN Premium, XL Batteries employs a pH-neutral chemistry discovered during experiments with a red paint’s energy storage capabilities.

Sisto elaborated that the company’s technology functions similarly to a vanadium redox flow battery (VRFB); however, instead of dissolving vanadium in sulfuric acid, it utilises organic molecules and pH-neutral water.

The company asserts that the easy access to its materials will render the systems significantly more affordable than a VRFB or other flow battery types.

In the interview, Sisto claimed that near-term costs are expected to be less than US$200/kWh for long durations.

Trenton Thornock, founder and CEO at Prometheus Hyperscale said of XL:

“We need batteries that offer performance at or above lithium, without risk of overheating, to deploy at our data halls.”

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