Waste heat from factories could be used to cool data centers thanks to a mineral-based system developed by researchers at New York University (NYU).

The NYU team has been experimenting with a mineral called zeolite, which they believe can act as a thermal battery in cooling systems, replacing the heat sink.

They have published a paper on their work, and believe it has the potential to significantly cut data center electricity costs.

How a zeolite thermal battery could work

Zeolites are crystalline materials with many microscopic pores, giving them a remarkable ability to soak up water vapor. When a dry zeolite encounters water vapor, it adsorbs it and releases heat. When the material is heated to sufficiently high temperatures, it releases the water again, resetting the cycle.

The system for data centers would work by drying out the zeolite at an industrial facility, such as a chemical plant or refinery, that produces low-to-medium-temperature waste heat, below 200°C (392°F). This “charges up” the zeolite thermal battery, which could then be transported to a data center.

Once on site, the process would run in reverse. Warm air or other coolants ejected from the server room would be adsorbed by the dried zeolite, which effectively acts as a heat sink. The researchers say that this adsorption process could replace compression chillers used in traditional data center cooling setups.

The mineral is already in use for applications such as water treatment and oil refining, and is inexpensive to buy. What’s more, it does not slowly lose its energy over time - the thermal energy remains locked in the zeolite until the water is reintroduced. That makes it suitable not only for long-duration storage but also for transport over long distances.

“While the electricity needs for data centers are still a small slice of the total US electricity market, it is rapidly growing,” said Dharik Mallapragada, assistant professor of chemical and biomolecular engineering and lead author of the paper. “This is an opportunity to ‘bend the curve’ and aim for a much more sustainable future, in a way that is beneficial to everyone involved.”

Thermal batteries and data centers: Big savings to be made?

Using detailed thermodynamic modeling, the NYU team, which included Mallapragada, Professor Pavel Kots, and postdoctoral researcher Gilvan Farias Neto, compared their proposed system with a conventional setup: a data center cooled by a compression chiller and an industrial facility rejecting waste heat through cooling towers.

The team estimated that, across a range of operating conditions, the proposed approach can reduce total electricity used by the data center for cooling and the industrial facility by more than 75 percent. For the data center alone, electricity consumption for cooling can be reduced by as much as 86 percent. In energy efficiency terms, this translates into a 12 percent improvement in PUE, or power usage effectiveness.

The combined system consumes 15-25 percent more water than a conventional cooling loop, as evaporation is central to the process, but the researchers say water is saved overall because waste heat is diverted into charging the zeolite ‘battery,’ rather than being dumped through cooling towers.

Even after accounting for the energy needed to haul tons of zeolite back and forth, the system still delivers net electricity savings in many scenarios, the NYU researchers said, sometimes exceeding 40 percent, though this assumes the use of modern electric trucks. Using rail transport could unlock further savings.

The proposed system is still at the modeling stage, and many engineering challenges remain. Zeolite beds must be designed for durability, rapid heat transfer, and repeated cycling, the team said. Coordinating operations between data centers and industrial partners will require new business models. The researchers have “begun speaking with several industry leaders about the possibility of scaling this solution up,” a statement from NYU said.