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P.S. Lee

P.S. Lee

Poh Seng (PS) Lee is a Professor and Head of Mechanical Engineering at the National University of Singapore (NUS), Program Director of the Sustainable Tropical Data Centre Testbed (STDCT), and founder of CoolestDC, an expert in sustainable AI data center cooling.

Aug 18, 2026

5:24
busy So before we go deeper into the technologies, can you explain what has changed in the shift from more CPU heavy data centers to GPU heavy data centers? And what does that mean for conventional cooling technologies that have been prevalent for decades? Are they becoming obsolete? And why is liquid cooling so critical for next generation data centers, especially in hot environments such as in Singapore or even Texas, where a lot of the data centers are being built today?
5:54
So I think the shift from CPU to the GPU is more than the increase in power consumption.
6:04
Obviously, the GPU as a chip architecture actually does consume more energy than CPU.
6:13
But I think GPU-based AI systems actually also concentrate, right? the much more computation electrical power and heat within a smaller volume.
6:24
So it's not just the absolute power, but it's also more intense over a smaller footprint of volume.
6:31
So that's because they combine accelerators, high bandwidth and memories, switches, power electronics in a tightly covered architecture.
6:40
So that actually changes the thermal problem or challenge from just addressing or looking at the average rack load to the issues like local hotspots.

12 MINS LATER

18:42
Which parameters do you have to take into account when designing a new cooling system? And what are some of these trade-offs that I'm trying to summarize here?

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