High-Performance Computing Data Center Warm-Water Liquid Cooling (ESIF)
National Laboratory of the Rockies (formerly NREL) · National Laboratory of the Rockies
A description of warm-water liquid cooling at the ESIF HPC data centre: high rack densities, warm supply water that cooling towers can produce year-round in a semi-arid climate, and return water warm enough to heat the building.
On this page
Overview
This page presents the warm-water liquid cooling used in the ESIF high-performance computing (HPC) data centre of the National Laboratory of the Rockies (formerly NREL). It stresses three features of the approach: high rack densities, warm supply water that cooling towers can produce year-round in a semi-arid climate, and return water warm enough to heat the building. The page was last updated on February 17, 2026.
The figures on the page are as follows: rack densities of 60 kW per rack or more are achievable with warm-water liquid cooling. Supply water can be up to 75 F and the design wet-bulb is 60 F. HPC systems heat the water to around 100 F for building heating; the building needs at least 95 F. This is a concrete example of waste-heat reuse.
As a limit, this is the showcase page of a single facility; it provides no detailed measurement data, cost or general design method. The results are specific to ESIF's semi-arid climate and HPC load profile, and the same conditions may not apply directly elsewhere. It remains valuable as a reference case showing that warm-water cooling can combine with chiller-free operation and heat recovery.
Key points
- Rack densities of 60 kW per rack or more are achievable with warm-water liquid cooling.
- Supply water up to 75 F; design wet-bulb is 60 F.
- HPC systems heat the water to around 100 F for building heating; the building needs at least 95 F.
- Cooling towers can produce the warm supply water year-round in a semi-arid climate.
- Page last updated February 17, 2026.
Using it in design
- Use as a reference case for warm-water DLC presets (supply about 24 C, return about 38 C).
- Check chiller-free operation against design wet-bulb plus tower approach.
- Model reuse of the return water for building heating as a waste-heat recovery option.
- Verify the supply temperature against the ASHRAE W classes.
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Who should read it
Cooling engineers designing liquid cooling and waste-heat recovery, and decision makers planning HPC facilities.
Related standards
- ASHRAE W-classes (Liquid Cooling Guidelines)
Publication details
- Authors
- National Laboratory of the Rockies
- Publisher
- National Laboratory of the Rockies (formerly NREL)
- Year
- 2026
- Document language
- English
- Source type
- Government / public
- Access
- Free to read
- Licence
- Copyright retained; citation only — the publisher’s terms apply to the original document
Original licence note
NREL/NLR (contractor-operated DOE laboratory) web page; not US-Gov public domain. Cited only.
Citation
National Laboratory of the Rockies (2026). High-Performance Computing Data Center Warm-Water Liquid Cooling (ESIF). National Laboratory of the Rockies (formerly NREL). https://www.nlr.gov/computational-science/warm-water-liquid-cooling
Events on this subject
- SC26 – International Conference for High Performance Computing, Networking, Storage and Analysis
- NVIDIA GTC
- ISC High Performance
All content and rights belong to the respective authors and publishers. SoSo CAD provides only the citation, its own summary and a link to the source, and is not responsible for the sources' content.
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