[AI Era Electric Power is National Power]⑫ Servers Submerged in Water Tanks... Immersion Cooling Data Centers Save 37% Electricity

93% Less Cooling Power Than Air Cooling
Perfect Protection Against Dust and Humidity... Longer Server Lifespan
Global Companies Focus on Immersion Cooling Technology

In order to respond to the "electricity-consuming hippo" that is artificial intelligence (AI) data centers, it is important not only to expand power supply and establish transmission and distribution networks but also to reduce electricity consumption itself. Forty percent of the power used by AI data centers, which will account for a significant portion of future electric energy, is consumed for cooling. This means that proper thermal management alone can reduce electricity consumption.

A recently spotlighted method for cooling data center heat is immersion cooling technology. Unlike the air cooling and water cooling methods used so far, immersion cooling involves storing servers in tanks filled with special fluids. Overseas, experiments are even underway to build data centers submerged in cold seawater.

How far has immersion cooling technology advanced? On the 19th of last month, related technology research was in full swing at SK Telecom’s Incheon building in Namdong-gu, Incheon. Inside, after passing through a security gate, there was a large pipe and a ceiling crane. The blue tank-shaped container is a tank-style server rack that uses immersion cooling technology to submerge servers.

Choi Woo-shin, Manager of the SKT AT Infrastructure Engineering Team, is explaining the submerged cooling system in an interview with Asia Economy. 2025.02.19 Photo by Yoon Dong-joo

Immersion cooling is a technology that cools servers by submerging them in a non-conductive special cooling fluid (fluid) that does not conduct electricity. Until now, air cooling, which circulates cold air inside data centers, has been widely used. Air cooling uses components such as special air conditioners and compressors that consume a lot of power. Water cooling improved on this by directly contacting pipes carrying refrigerant to the servers to lower their temperature. Immersion cooling, which submerges servers entirely in cold fluid, offers higher cooling efficiency.

Inside the tank, about 20 servers were densely installed. These are experimental servers not yet deployed for actual service, used to verify that they operate well even when submerged in fluid. The fluid does not conduct electricity but has high thermal conductivity, allowing it to efficiently lower the servers’ temperature.

Although the fluid appears still on the surface, it is continuously and slowly circulating to regulate temperature. Opening the right side of the tank revealed several thick pumps. The fluid heated by contact with the servers moves through the pumps to a heat exchanger, where it is indirectly cooled by cold water. The cooled fluid is then supplied back to the tank containing the servers.

Choi Wooshin, Manager of the SKT AT Infrastructure Engineering Team, is explaining the process of fluid cooling. 2025.02.19 Photo by Yoon Dongju

Choi Woo-shin, manager of the AT Infrastructure Engineering Team at SK Telecom, explained, "The fluid is almost colorless and odorless, but to test the fluid in which servers are submerged, we inserted 70 to 80 heating rods to boil and burn the fluid," adding, "Oxidation occurred in the fluid, turning its color brown."

Manager Choi said, "The temperature converges to that of the water. For example, even if the fluid rises above 40 degrees Celsius when the water is at 10 degrees, it is designed so that when it meets the water, the temperature drops to 15 to 20 degrees."

SK Telecom’s experiments confirmed that compared to conventional air cooling, cooling power consumption was reduced by 93%, server power consumption by over 10%, resulting in a total power saving of 37%.

While conventional racks that hold servers like bookshelves can accommodate only one or two servers each, immersion cooling technology increases the number of servers that can be housed in the same space to 7 or 8. By densely packing more servers into a smaller space, costs related to space occupancy and power consumption can be saved.

Additionally, air cooling requires extra equipment and electricity to control dust and humidity, but servers submerged in fluid are free from dust and humidity. This is expected to extend the servers’ expected lifespan.

As the advantage of immersion cooling technology in significantly reducing data center electricity usage became known, global companies are actively conducting research and collaborations to apply this technology. NVIDIA is seeking cooperation with immersion cooling companies following concerns about heat generation from its Blackwell graphics processing units (GPUs).

KT Cloud also underwent technology verification for immersion cooling last year. KT Cloud explained that through immersion cooling technology, it achieved a 58% reduction in utility power consumption in server rooms compared to conventional air cooling, a 15% reduction in server fan power, over 70% reduction in server room area, noise reduction from fans, and extended server lifespan through improved heat exchange efficiency. KT Cloud plans to introduce direct chip cooling (D2C) and computational fluid dynamics (CFD) programs in the future.

Domestic refining companies such as SK Enmove, GS Caltex, S-Oil, and HD Hyundai Oilbank have also entered the development of fluids for immersion cooling. SK Enmove named theirs "Zic e-FLO," and GS Caltex named theirs "Kixx Immersion Fluid S." SK Telecom signed a memorandum of understanding (MOU) with Giga Computing and SK Enmove to develop next-generation cooling technologies.

However, since immersion cooling technology is still in its early stages, limitations remain. Maintaining and managing servers with existing methods is difficult. To inspect a server, it must be suspended by a crane for 15 minutes to be removed, and then one must wait for all the fluid to drain. This is more cumbersome and time-consuming than conventional methods. Other challenges to be addressed include safety management, seismic regulations, and fluid handling and disposal.