Whenever the NPCF needs additional chilled water, the University of Illinois chiller plant can deliver 5,400 tons of chilled water. The delivery pipes within the NPCF facility start at 24 inches in diameter and carry water all the way down to 2 inch pipe at Blue Waters.
The addition of a 7 million gallon thermal storage tank allowed the University chiller plant to more efficiently serve NPCF as well as the rest of campus. Thermal energy storage can reduce costs by allowing companies to run air conditioning systems at night, when power rates are cheaper. During daytime hours, when demand on the grid is higher and electricity is mor expensive, these customers can tap the energy storage system, which serves as a “battery” that substitutes for the air conditioner. Thermal storage systems typically use ice or liquid coolant that can be chilled and then used in heat exchange systems.
While Blue Waters and the NCPF were designed to be 100 percent water-cooled, air handlers still need to be installed in the facility. Additional supercomputers will be housed at the NPCF that may require air cooling, which will also support staff working on the supercomputers.
IBM's Michael Ellsworth Jr. did a thorough analysis of what Blue Waters would have required if it was cooled with air instead of water, and estimated that 228 Computer Room Air Handler (CRAH) units would have been needed. In slide 43 of Ellsworth's presentation, a complete Power7 rack is depicted with a water conditioning unit, 8 water lines and 4 power cords.