Data centers · Feature
Computers started on liquid, moved to air, and are now going back to liquid.[1,2]
XOtavo · Facts as of the dates shown, checked Oct 25, 2026. Numbers in brackets link to the sources list.
Photo: Oak Ridge National Laboratory, CC BY 2.0, via Wikimedia CommonsIBM’s big computers of the 1960s to early 1990s were cooled partly with water.[1,3] In the mid-1990s, lower-power CMOS chips let IBM’s servers switch to air.[1] Now the newest AI racks are designed to be cooled entirely by liquid, with warm-water designs, sealed closed loops, and in some places waste heat sent to homes nearby.[2,4,5]
“By 2023, hyperscale and colocation account for 84% of the 66-billion-liter total, while internal data centers fell to just 12%, driven by water efficiency improvements.”[6]Lawrence Berkeley National Laboratory, on U.S. data centers’ direct (on-site) water use, which it says is “primarily associated with cooling infrastructure.” As of Dec 2024.
Timeline
IBM’s System/360 Model 91 used a hybrid air-to-water design: a coolant distribution unit with pumps and a heat exchanger moved 40–79 kW of its heat into building water.[1]
Front panel of an IBM System/360 Model 91, as displayed at the Living Computer Museum, Seattle. Photo: MBlairMartin, CC BY-SA 4.0, via Wikimedia Commons
IBM’s Thermal Conduction Module, used in its 3081 and later ES/9000 systems, carried chip heat through metal into water-cooled plates.[1]
Diagram drawn by us from the source cited.
The Cray-2 supercomputer’s circuit boards were immersed in Fluorinert, a liquid that does not conduct electricity.[7]
A Cray-2 supercomputer at the Museum für Verkehr und Technik, Berlin, 2022. Photo: Fridolin freudenfett, CC BY-SA 4.0, via Wikimedia CommonsIn IBM’s water-cooled ES/9000 processors, about 80% of the heat went to a closed-loop water system, supplied at 21.7°C (about 71°F). As of July 1992.[3]
Diagram drawn by us from the source cited.
Lower-power CMOS chips let IBM’s servers go fully air-cooled.[1]
Under the raised floor of a data center, 2008. Photo: Adamantios, CC BY-SA 3.0, via Wikimedia Commons
Meta’s Luleå, Sweden data center went live in June 2013 using “chilly Nordic air” to cool its servers and 100% renewable local hydroelectric power.[8]
In early tests, Meta said it averaged a PUE “in the region of 1.07” (as of Jun 12, 2013).[8]
Meta’s data center in Luleå, Sweden, photographed in 2016. Meta says it is cooled with outside air and runs on local hydroelectric power.[8] Photo: Christopher Down, CC BY 4.0, via Wikimedia Commons
NREL’s data center in Golden, Colorado uses warm-water liquid cooling, and its captured heat warms the building’s offices and other spaces.[9]
NREL reports an annualized PUE of 1.036, compared with an average of around 1.8 that it cites for data centers (undated page, checked Oct 25, 2026).[10]
Unveiling the warm-water, liquid-cooled Peregrine supercomputer at NREL’s data center in Golden, Colorado, 2013. Photo: U.S. Department of Energy, Public domain, via Wikimedia Commons
Whole servers can sit in a liquid that does not conduct electricity.[11]
Microsoft reported in April 2021 that two-phase immersion cut an individual server’s power use by 5% to 15% in tests in Quincy, Washington.[11]
An immersion-cooling tank, 2017. Servers sit in a liquid that does not conduct electricity.[11] Photo: Rolf Brink, CC BY-SA 4.0, via Wikimedia CommonsORNL’s Frontier supercomputer is cooled with warm water, targeted at about 90°F (32°C), so it needs no refrigeration and is cooled by evaporative towers instead (as of Sep 10, 2024).[12]
Frontier at Oak Ridge National Laboratory, 2022. It is cooled with warm water and no chillers.[12] Photo: Oak Ridge National Laboratory, CC BY 2.0, via Wikimedia Commons
Meta says its Odense, Denmark data center delivers about 165,000 MWh of surplus heat a year to Fjernvarme Fyn’s district heating network, enough for about 9,000 households (as of Feb 2025).[5]
Diagram drawn by us from the source cited.
Nvidia says its Vera Rubin rack is 100% liquid-cooled, with cable-free, hose-free and fanless trays, and accepts coolant as warm as 45°C (113°F). Nvidia’s own figures, as of Mar 16, 2026.[2]
Diagram drawn by us from the source cited.
Some companies are now testing computers in orbit. Google says satellites in a dawn–dusk orbit would get near-constant sunlight for power.[13]
Starcloud says its satellites shed heat by radiating it into space, with no water.[14]
Google lists challenges including thermal management, on-orbit reliability, radiation and launch costs.[13]
Starcloud-1 carried an Nvidia H100 GPU into orbit in November 2025.[15]
On Oct 1, 2026, Google said a Project Suncatcher prototype with its TPU chips, built with Planet, had reached orbit on the Transporter-18 rideshare mission.[16]
SpaceX applied to the FCC on Jan 30, 2026 for a “SpaceX Orbital Data Center system” of up to one million satellites. The FCC accepted the application for filing on Feb 4, 2026, which is not an approval.[17]
All are early tests or plans as of Oct 25, 2026.[16,15,17]
Diagram drawn by us from the sources cited.Good to know
In cold-plate systems, coolant flows in a closed loop through metal plates mounted on the chips, rather than over the electronics.[18,4]
Industry-standard quick disconnects are designed to be “drip free” and hot-pluggable, sealing both sides when unplugged.[19]
Leak sensors in compute and switch trays report to the building management system, which can trip a rack’s power breaker and close its coolant shutoff valve.[20]
Nvidia specifies PG25, about 75% water and 25% propylene glycol, for its cold-plate loops.[18]
Industry guidelines start from deionized or reverse-osmosis water and call for ongoing checks of conductivity.[21]
Immersion systems use dielectric liquids, so whole servers can sit right in them.[11]
Leaks can still happen. Operators treat them as a risk to design for and manage, not one that has gone away.
Interactive explainer
Pick a method to see how it works, in plain steps, and why it matters. Facts as of the dates shown; checked Oct 25, 2026.
Diagram drawn by us from the sources cited.
Diagram drawn by us from the sources cited.
Diagram drawn by us from the sources cited.
Microsoft says its designs since August 2024 evaporate zero water for cooling, avoiding more than 125 million liters a year per data center, with a “nominal increase” in energy use (as of Dec 9, 2024).[4]
Diagram drawn by us from the sources cited.
NREL reports an annualized PUE of 1.036 for its data center, versus around 1.8 on average (checked Oct 25, 2026).[10]
Diagram drawn by us from the sources cited.
Microsoft reported in April 2021 that two-phase immersion cut an individual server’s power use by 5% to 15% in Quincy, Washington tests.[11]
Diagram drawn by us from the sources cited.
Meta says Odense delivers about 165,000 MWh of surplus heat a year to Fjernvarme Fyn, enough for about 9,000 households (as of Feb 2025).[5]
Diagram drawn by us from the sources cited.
Nvidia says coolant that warm lets many data centers use ambient air and closed-loop dry coolers, reducing the need for compressors, and that the power saved could run up to 10% more racks.[2]
Nvidia also says servicing time is up to 18x lower and tray assembly drops from more than 1.5 hours to about 5 minutes. Nvidia’s own figures, as of Jan–Mar 2026; it says the rack ships in the second half of 2026.[24,2]
Numbers in brackets in the text link to these sources. Photos are illustrations; their credits are listed separately.
Diagrams drawn by us from the sources cited.
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