Submerged Servers Can Now Heat Your Office

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A four-rack installation of the Green Revolution liquid coolings solution, which submerges servers in a coolant similar to mineral oil.

Green Revolution Cooling says it has adapted its liquid immersion cooling system to recapture server heat, using it to heat water for climate control systems in nearby buildings.

The Austin, Texas company says one of its systems installed at the Royal Institute of Technology (KTH) in Stockholm will reliably produce water at a temperature of 50°C (about 122°F), hot enough to pump to surrounding buildings for building heat. The Stockholm system, installed in July, uses commodity servers and standard CPUs.

Servers Submerged in Dielectric Fluid

Green Revolution’s CarnotJet Submersion Cooling System resembles a rack tipped over on its back, filled with 250 gallons of dielectric fluid, with servers inserted vertically into slots in the enclosure. Fluid temperature is maintained by a pump with a heat exchanger using a standard water loop.

That water loop is usually run to an evaporative cooling tower to reject the heat to the atmosphere, but it is also possible to reuse the heat from the water, as shown in the tests in Stockholm.

Higher Density Equals More Heat

Temperatures in most data center hot aisles range from 80 to 115 degrees Fahrenheit (27 to 46 degrees Celsius), still fairly low temperatures for some heat recovery strategies. The KTH study uses high-density 20-kilowatt racks packed with 42 servers, which results in higher heat output. Since liquid cooling solutions can support higher density racks, these systems could have more potential in heat reclamation strategies than air-cooled systems.

KTH researchers will now try to produce 70°C water (about 158 degrees F), which could be used to produce hot tap water, a useful commodity all year long ( as opposes to heating systems used only in the winter).

Green Revolution says the testing at KTH continues with new server hardware, with the results to be included in a white paper by the end of the year.