In his own lab, Nikhef IT architect Tristan Suerink is working on liquid cooling for data servers. His experiments show that this reduces power consumption by up to a quarter.
Outside at Amsterdam Science Park, tropical temperatures prevail during these summer weeks, but inside the laboratory of Nikhef IT architect Tristan Suerink, it’s pleasantly cool. The heat generated by two large, specialized servers as they process a computationally intensive task is efficiently dissipated by the room’s ventilation system.
Suerink—wearing bright yellow headphones to block out the roar of the equipment—gestures toward two servers in a standing server rack. The top server uses conventional air cooling: alarmingly loud fans that blow the heat from the hot processors past large cooling fins and out the back of the cabinet—heat that’s clearly noticeable to the touch.
The lower server looks the same, except that a blue and a red hose protrude from the back. The blue hose supplies a coolant that begins to boil inside the cabinet on top of the hot processors, after which the hot vapor is channeled through the red hose to the cooling unit below, where it cools down and condenses, beginning a new cycle. The enclosure—which Suerink has named “NAT”—is noticeably cooler to the touch at the back. Moreover, the system is quiet and compact.
“Here,” says Suerink in the quieter workspace of the lab, “is the future of the high-performance computing carried out at institutes like Nikhef.” In recent years, he has been conducting experiments with innovative cooling systems for servers to find alternatives to conventional air cooling. For the intensive computing work done at Nikhef, air cooling is no longer sufficient. Moreover, air cooling consumes a lot of electricity.
Suerink has now compiled the results of his tests with various systems, and Nikhef is considering implementing liquid cooling in its data center on a broader scale. “The cooling capacity of server rooms will eventually become a limiting factor for computing,” he says.
As part of his work, Suerink regularly attends major international computer trade shows. Around 2019, at a convention in Denver, he saw for the first time how server manufacturers were experimenting with liquid cooling for larger processors. “I said right then at Nikhef that we needed to investigate this. At first, we tried some things ourselves with liquid CO₂, but after that we mainly started monitoring the market. The question became: What can help us adequately cool the increasingly intensive computing?”
In his lab, he says, he can conduct experiments with servers and cooling systems that you’d understandably prefer not to have in a data center. He heated his lab space to over 30 degrees to see how the cooling systems and servers would behave under those conditions, using liquids that are off-limits anyway when surrounded by electronics. Now the test system is running endurance tests on the materials and the control systems.
The results of all that measurement work—largely conducted in collaboration with SURF—are quite remarkable and clearly favor liquid cooling. With liquid cooling, a cooled server can achieve up to a quarter less power consumption while maintaining the same computing capacity. Conversely, a liquid-cooled server easily delivers six percent more computing power than an air-cooled machine.
For Suerink, the key component is right here on the table: a liquid cooling element from the company ZutaCore—a flat plastic box with the familiar blue and red hoses, mounted on a copper plate to ensure sufficient thermal contact with the hot processors. “It’s a beautiful and robust system,” says Suerink. “The fluid enters the unit via a small float, similar to the one in a toilet tank, without any active control—it’s purely based on physics.”
The coolant used is a non-conductive substance with the code name R1233ZD, which is considered in the industry to be an alternative to CFCs that deplete the ozone layer or are potent greenhouse gases. The substance evaporates and condenses at exactly the right moments and dissipates heat very effectively.
Not long ago, Suerink attended another computer trade show in the U.S., this time in Atlanta, where he visited cooling system vendors with his questionnaire. Could they also deliver these performance figures?
Suerink: “I received quite positive responses, which reinforced my belief that we’ve found the right system—something we can move forward with.” The plan now is to first conduct further testing of the liquid cooling systems, during which the heat will actually be transferred to Nikhef’s cooling system—which already heats residential buildings in the vicinity of the institute. He expects that, with a relatively minor modification, the liquid cooling system could then be integrated into parts of the data center.
That, he says, would, for example, align well with the MERGE project, which was recently approved by the Netherlands Organization for Scientific Research (NWO). That project is intended to boost the computing capacity at the Nikhef particle physics institute, so that it can handle the ever-growing data streams from experiments and the rise of AI and machine learning.
Suerink: “If we can achieve a 25 percent reduction in power consumption per computational step, that would be a tremendous contribution that we could also showcase to society.”
