Thinking Inside The Box: The Latest In Data Center Cooling Tech Is Full Immersion

Before the advent of generative artificial intelligence, data centers were kept from overheating by circulating chilled air through the facilities.

“Air cooling was the industry standard because air is abundant and the way it works is simple,” said Brian Haught, director of engineering at Airedale, a cooling solutions company. “Air is literally everywhere.”

But AI’s growing need for power and the server rack densities it requires has pushed data center cooling demands beyond what these conventional systems can handle.

“Air cooling was fine for server racks of 5 to 15 kilowatts,” Haught said. “The new generation of server racks that are being rolled out over the last two years are 100 kilowatts. At those densities, air is no longer able to carry the heat load because it's not a good enough conductor of heat.” 

Enter liquid cooling.

“Liquid is a better conductor. Plus, with liquid, you can be more precise,” Haught said. “You can route liquid directly to the hottest components you need to cool.”

With direct-to-chip liquid cooling, liquid is applied directly to the heat source using cold plates and piping.

“To be sure, this is more complicated from a design perspective,” Haught said. “You need infrastructure, which air doesn’t require.”

“But the benefits in efficiency are worth the trade-off,” he added.

An even more cutting-edge liquid cooling solution is known as full immersion. With this type of system, the whole server is immersed in liquid, which cools all components of the server equally, instead of just the chip itself, Haught said. 

“Think of it as a data center in a box, using dielectric fluid,” he said.

Dielectric fluid, unlike water, doesn’t conduct electricity. It is an insulator that prevents electrical discharges and dissipates heat. It has been used in electrical transformers for decades and is now finding a new, more widespread application.

There are two types of immersion cooling: Single-phase immersion cooling circulates a dielectric through a heat exchanger to remove the heat, and two-phase immersion cooling uses the heat of vaporization to carry the heat away from the server components and then is condensed using a heat exchanger.

“With immersion cooling, there aren’t any separate components, like piping, that eventually leak or cause issues in other ways,” he said. “It’s a sealed tank. The liquid gets into all the nooks and crannies and carries the heat away.”

Nonaustere Environments

Full immersion cooling technology has a plethora of benefits, Haught said. 

“It’s agnostic to the generation of the servers it is cooling, since no specially designed cold plates or plumbing need to be installed, a downside of direct-to-chip liquid cooling,” he said. 

“Another major benefit of data-center-in-a-box immersion is that it can be deployed in nonaustere locations,” Haught said.

Typically, data centers need to be completely clean environments on the inside. But with immersion cooling, the server is in a tank that is completely sealed.

“That means we can put it anywhere,” Haught said. “We’ve deployed it on a beach in Miami and on a truck driving from Texas to California, doing performance compute the whole time.

“Other practical use cases include putting server tanks at the bottom of cellphone towers or closer to the source of the data, rather than in far-flung locations, to avoid latency issues. This is where immersion cooling is taking off not just as a pure thermal play but for other future applications.” 

Thermal Concern

A key opportunity with direct-to-chip and immersion cooling is that they outperform air cooling in energy efficiency.

“The amount of energy a system needs to pull heat out drops significantly when you move from air cooling to direct-to-chip,” Haught said. “Then it drops further still when you go full immersion.”

Like with any new technology, immersion cooling requires education, training and the creation of new servicing processes. Airedale experts provide their clients with support in this capacity, Haught said.

“You’re taking the rack and setting it on its side, which is different,” Haught said.

As data center rack densities increase, the industry is participating in research initiatives to address the “thermal concern, the power consumption concern and the safety concern,” he said.

Airedale is participating in a U.S. Department of Energy program called Cooling Operations Optimized for Leaps in Energy, Reliability and Carbon Hyperefficiency for Information Processing Systems, or COOLERCHIPS.

The program’s aim is to “develop transformational, efficient, and reliable cooling technologies for data centers,” for national security, environmental and business-efficiency purposes.

“It’s about exploring how to handle intense thermal densities like those generated by megawatt racks,” Haught said. “The program evaluates different technologies and how to combine them in different ways.”

Building From The Ground Up

Despite the immense benefits of liquid cooling, the solution has other hurdles to adoption.

“Retrofitting those data centers for liquid cooling is incredibly expensive,” Haught said.

That means existing data centers, designed and built to support old thermal densities, are unlikely to get converted. Instead, the technology is much more likely to be deployed in new facilities because of the ease of designing and building from the ground up.

Where liquid and air cooling are likely to be seen deployed together are colocation centers, Haught said.

“That’s where we’ll see a hybrid approach,” he said. “It’s not binary.”

In one hybrid scenario, direct-to-chip cooling using cold plates is used to cool the chips themselves, focusing on addressing the hottest part of the server, while air cooling is deployed for the peripheral sources of heat like power supplies, data storage and RAM.

But the new AI server racks being rolled out are so dense and get so hot that they will require liquid cooling in some capacity, whether it is direct-to-chip or immersion cooling, Haught said.

“Our customers don’t want to get left behind,” he said. “If liquid cooling becomes the required industry standard, they want to start establishing procedures and maintenance intervals and training their staff so they’ll be ready when this scales. Airedale has products to address the full thermal chain from the chip all the way to final heat rejection, supporting all approaches to data center cooling.”

This article was produced in collaboration between Airedale and Studio B. Bisnow news staff was not involved in the production of this content.

Studio B is Bisnow’s in-house content and design studio. To learn more about how Studio B can help your team, reach out to studio@bisnow.com.