Thermosyphon Cooler Hybrid System for Water Savings in an Energy-Efficient HPC Data Center

Improving data center operational efficiency requires focusing on both energy and water usage. The U.S. Department of Energy National Renewable Energy Laboratory (NREL) took a holistic approach to designing the world’s most energy-efficient High-Performance Computing (HPC) Data Center. Completed in 2014, the 930-m2 (10,000-ft2) center is located inside the Energy Systems Integration Facility (ESIF), which is Platinum rated by the Leadership in Energy and Environmental Design certification program, on NREL’s Golden, Colorado, campus. The HPC Data Center has maintained a trailing 12-month average power usage effectiveness (PUE) of 1.06 or better since opening, and it features a chiller-less design, component-level warm-water liquid cooling, and waste heat capture and reuse. In 2016, Johnson Controls partnered with NREL and Sandia National Laboratories (Sandia) to deploy a thermosyphon cooler (TSC) as a test bed at NREL’s HPC Data Center and to quantify on-site water savings and energy usage. The thermosyphon cooler hybrid system (TCHS) integrates the control of a dry heat-rejection device with an open cooling tower. This paper provides the results from the first 24 months of the TCHS operation, showing how this system has cut the data center’s on-site water usage in about half without negatively impacting the center’s energy-efficient operation.