A hybrid cooling system cut direct water use at an operating national-laboratory data center.

Warm liquid carries heat away from computing equipment more directly than room air. When outdoor conditions allow, the thermosyphon rejects that heat without the cooling tower’s normal evaporation. The facility retained its tower for peak conditions, making this a hybrid system rather than a water-free one.

DOE reported 1.16 million gallons avoided in the first year and 2.10 million over two years. The figures describe one operating federal HPC facility, not a universal result for larger commercial campuses.

The approach depends on warm-water equipment, outside conditions that support passive heat rejection, and controls that can switch between modes. A different climate, density, reliability requirement, or water source changes the balance.

A useful proposal should therefore publish the full cooling sequence, expected hours in each mode, site water withdrawals and consumption, and actual metered performance after operation begins.