High-density cooling specialist Green Revolution Cooling has published photos and video of several installations of its product, which submerges servers in a liquid similar to mineral oil. The Austin, Texas startup said its cooling enclosures can eliminate the need for CRAC units and chillers, allowing users to cool high-density servers at a fraction of the cost of traditional racks.

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, which can be connected to a standard commercial evaporative cooling tower. The company says its solutions will work with OEM servers with slight modifications (removing unneeded fans, applying a coating to hard drives).

Liquid cooling is used primarily in high-performance computing (HPC) and other applications requiring high density deployments that are difficult to manage with air cooling. Interest in liquid cooling has been on the rise as a growing number of applications and services are requiring high-density configurations.

Green Revolution's first unit was installed at the Texas Advanced Computing Center in Austin, home to the Ranger supercomputer. This video features a four rack (100 kW) installation at Midas Networks, an ISP in Austin:

Green Revolution says its enclosures represent a 50 percent savings in overall energy costs for the workloads at Midas Networks. The company says the payback on the initial investment in the liquid cooling system ranges from one to three years.

Mineral oil has been used in immersion cooling because it is not hazardous, transfers heat almost as well as water but doesn’t conduct an electric charge. Green Revolution is among a number of companies introducing liquid cooling solutions that immerse servers in fluid. An immersion system with a different design was introduced by UK firm Iceotope at the SC09 event, while Hardcore Computing introduced its Liquid Blade immersion cooling unit last year.

A photo gallery on the Green Revolution web site shows other early installations, in which the enclosures sit atop a containment system to serve as a backstop against leaks.

"The containment here is a 3 inch metal wall, made of angle iron, surrounding the tanks and pumping module and sealed to the concrete slab below," said Mark Tlapak of Green Revolution. "The area holds significantly more than one rack. In between the tanks we place expanded metal catwalk that sits 3 inches high to allow people to walk around the racks even if the containment area contains coolant. Each tank has two coolant level detection sensors that tie into the control software and send out instant alerts in the event of a change in coolant level."

Here's another look at the Midas Networks installation: