The US Department of Energy’s National Renewable Energy Laboratory (NREL) is taking liquid cooling to the next level, carrying out a retrofit that uses warm water for its Skynet high performance computing (HPC) cluster.

The retrofit of its air-cooled racks will be carried out as part of a relocation of the Skynet cluster into its new Energy Systems Integration Facility (ESIF) in Golden, Colorado, which it has been designed to achieve a Power Usage Effectiveness (PUE) of 1.06.

NREL said this low PUE makes the Colorado facility the most energy efficient data centers in the world.

The 182,500 sq ft facility has been designed to carry out research into distributed energy systems and the integration of renewable energy into the electricity grid.

It is used for large scale modelling and simulation of material properties and processes that the laboratory said would be too dangerous to carry out using direct experimentation.

Its liquid cooled retrofit will see the lab place liquid cooling vendor Asetek’s RackCDU direct-to-chip hot water cooled system, which uses warm water at 75F to operate servers, on to existing air-cooled servers and racks.

“Because of RackCDU’s design, these performance improvements will be achieved without the need for a customized server design,” Asetek said.

Waste heat recovered from the system will be used as a primary source of heat for the rest of the facility – buildings, offices and laboratories.

NREL’s director of its Computational Science Center Steve Hammond said the system will help reduce the facility’s water use and allow it to increase server density within the cluster.

“Starting with warmer water on the inlet side can create an opportunity for enhanced waste-heat recovery and reduced water consumption, and in many locations can be accomplished without the need for active chilling or evaporative cooling, which could lead to dramatically reduced cooling costs,” Hammond said.

Asetek claims its RackCDU can bring about cooling energy savings of up to 80% and density increases of 2.5 times that of modern air-cooled data centers.

“RackCDU removes heat from CPUs, GPUs, memory modules and other hot spots within servers and takes it out of the data center using liquid where it can be cooled for free using outside air, or recycled to generate building heat and hot-water,” Asetek said.