tl;dr: NVIDIA's Rubin AI infrastructure uses 100% liquid cooling with coolant running up to 45°C, enabling closed-loop systems that can operate without chillers or evaporative cooling in favorable climates—cutting water use from ~2.6M gallons/MW/year to near zero. The higher operating temperature allows outdoor dry coolers to reject heat efficiently year-round, eliminates fans entirely, and triples rack density (6U servers fit in 2U). Since cooling accounts for up to 40% of data center power, a 50MW facility could save over $4M annually.