KT Cloud Liquid Cooling Lab Reproduces 140 kW Racks Without GPUs

KT Cloud showed reporters a Seoul test lab on Oct. 30 that reproduces 140 kW of liquid-cooled rack heat without GPU servers, Yonhap News Agency reported.

The lab sits in the AI Innovation Center at KT Cloud's Mokdong 2 data center. The company calls the unit a load bank. Yonhap and Digital Daily reported that KT Cloud built it in-house and that it imitates more than heat: it reproduces the coolant flow, pressure and temperature behavior of a real GPU server, so the cooling plant can be tested before expensive servers arrive. A KT Cloud official told Digital Daily that commissioning a liquid system before servers are delivered is critical, because the servers cost so much.

Rack heat and the cooling load

KT Cloud told reporters that racks of conventional servers drew about 2 kW to 2.2 kW (Yonhap and Digital Daily give slightly different figures), while racks holding dense AI servers now draw 30 kW to 150 kW. It said the figure could reach 600 kW per rack in future. At those densities air cooling alone struggles, Yonhap wrote, so KT Cloud uses direct-to-chip (D2C) cooling: a cold plate sits on the GPU and coolant flows through it.

KT Cloud said D2C can cut the power spent on cooling by 20% to 30% against air cooling. That is the company's own claim, and no site, period or PUE (power usage effectiveness) basis was given. At the lab, KT Cloud validates the technology on NVIDIA B200 GPU servers and is studying design conditions for NVIDIA's next-generation Rubin GPUs, according to Yonhap. It already sells D2C liquid cooling to a global hyperscaler customer at its Gasan AI data center.

The heat has a structural cost too. Digital Daily reported that new KT Cloud halls are being designed to carry 1.5 to 2 times the floor load of Mokdong IDC 2, because liquid systems add weight. Converting old halls is limited: Mokdong IDC 2 holds 22 MW of secured power, and remodeling does not change that, the AIDC business development lead said. KT Cloud is considering converting about one floor for mid-density AI customers. KT Cloud broke ground on its 50 MW Ansan AI data center in October, as Voltgrid reported on Oct. 22, and Digital Daily puts supply from Ansan in 2028 to 2029.

152 MW nearly full, 1 GW targeted

Digital Daily reported that KT Cloud operates about 152 MW of data center capacity, most of it already filled. It targets 1 GW of new AI data center supply by 2031, excluding conversions of existing halls. About 200 MW is under construction, starting with Bucheon in 2027, and that volume counts toward the 1 GW. Capacity for KT Group's own AI business is included, but its size and location are not fixed.

In Gunsan, KT Cloud is working with SGC Energy on a 60 MW first phase targeted for the first quarter of 2028, expandable to 300 MW. The company said it will apply Vertiv's modular power and cooling infrastructure there, and it is researching power infrastructure and DC power with LS Electric. ETNews also saw ORv3 racks with 48 V DC power distribution and an RoCEv2 AI network in the lab. KT Cloud will move proven designs to Gunsan, Cheongna and Ansan, ETNews wrote. Telecom rival LG Uplus signed a liquid cooling MOU with Ecolab Korea in late October.

What is not confirmed yet

None of the three reports gives the coolant supply temperature, the heat capacity of the cooling units, the share of heat taken by liquid, or a PUE for any KT Cloud site. The 600 kW per rack figure is a forecast, not a design in service. Digital Daily noted that the final location and size of KT Group's internal capacity are open, and that the draft rules under Korea's AI data center special law may exclude colocation operators from state support, which KT Cloud called a problem.