Will Liquid-Cooled Computers Make a Comeback?

Liquid cooling was once a staple of large-scale computing, but has largely been replaced by air cooling. We identified several efforts to bring liquid cooling to the server world in our first version of this post in 2012 and have seen continuous progress since. Here is the latest news.


One sign of a robust segment is its ability to fund an industry organization to advance its interests. The Demand Liquid Alliance (DLA) was formed in 2012, but by late 2014 had been the Liquid Cooling Work Group under the leadership of CoolIT Systems' Geoff Lyon. We'll see if this latest incarnation of an industry nexus is able to move the segment forward.

CoolIT Systems was an early supported of the DLA. It says its products use "...warm liquid rather than cold air to dissipate heat from computer and server components. By capturing component heat in a liquid path DCLC [Direct Contact Liquid Cooling] allows for higher component performance and reliability, higher densities, and decreased data center OPEX (decrease or eliminate use of chillers and CRAC’s)."

The California Energy Commission (CEC) has awarded to Asetek, discussed in the 2013 section, $3.6 million for the "Demonstration of low-cost data center liquid cooling with 12- month payback." The company will install, "...iRackCDU D2C™ (Direct-to-Chip) liquid-cooling in two large scale, super computing data centers in California. The project will include installation of RackCDU in approximately 90 racks of servers and the addition of RackCDU D2C liquid cooling to servers from multiple OEMs." We have requested of the CEC that they provide us with the project results when published in 2016.


Iceotope, discussed in the 2012 section, below, won a 2014 Sustainia 100 award.


The hottest individual chips like CPUs and GPUs can be cooled directly. Technology from the University of Wisconsin at Madison (USA) College of Engineering is said to be the first "…that takes advantage of the efficiency of boiling, while being compact, able to cool many devices in series, and available at a cost that is competitive with traditional air-cooling technologies. [It] uses an environmentally safe dielectric fluid that evaporates and then re-condenses as it flows through processing units." Professor Timothy Shedd generously spent a couple of hours with me at his lab updating me on this technology.

Danish company Asetek, also offering a direct-to-chip coolling system, won a 2013 DatacenterDynamics Awards for Future Thinking & Design Concepts for its RackCDU D2C™, "...a 'free cooling' solution that captures between 60% and 80% of server heat, reducing data center cooling cost by over 50% and allowing 2.5x-5x increases in data center server density."


UK manufacture Iceotope offers a "…computer server platform cooled using liquid…configured as a single supercomputer, as multiple server racks or scaled out to create an entire data centre…We combine industry standard servers, liquid cooling and our own IP into a scalable Tier 3 ready solution…it uses liquid rather than air to cool and thus negates the need for massive capital expenditure on air conditioning, chillers, humidity control systems." The company claims its "Iceotope Platform can cool 20 kW of ICT using just 80 watts of power."

Iceotope has also aligned itself with the Green ICT practice of using data center waste heat. Its solution "…delivers high grade heated exhaust water, which can be used to heat offices, roads, parking lots…" One of the principals in Iceotope is Peter Hopton, an experienced Green ICT pro with UK manufacturer VeryPC.

US company Green Revolution Cooling claims that "With our fluid-submersion technology, we can reduce cooling energy use by 90-95% while also reducing server power by 10-20%. Greenfield installation costs are significantly lower than comparable air-cooled systems and retrofit paybacks are as low as one year and typically below three years…a 1-3 year payback, depending on power density, based on energy savings alone. A single 10kW, 42U Rack at 8 cents/kWh will typically save over $5,000 per year in electricity costs…a Greenfield installation will save over $100,000 per 42U rack over 10 years, split between energy and infrastructure savings."

Green Revolution Cooling moved into waste heat recapture in 2011 with a test at Stockholm's Royal Institute of Technology (KTH). "[The installation] will reliably produce water up to 50°C (122°F) — hot enough to pump to surrounding buildings for building heat. Remarkably, this performance has been achieved with commodity servers and standard CPUs…As testing continues at KTH, researchers will strive to produce 70°C water, which could be used to produce hot tap water, a useful commodity all year long. And if 70°C is achieved, KTH will be able to recapture energy in addition to heat…we expect a full white paper by the end of the year." (Click the "reuse-heat" tag above to find applications ranging from a Swiss data center heating municipal swimming pool to Microsoft data center accelerating the biogas production it uses to generate electricity.)

There are still deployment hurdles for early adopters to overcome, but liquid cooling is yet another example of how Green ICT is pushing innovation.

Images courtesy of UW Madison Engineering, Icetope