Power Distribution in Immersion: Enabling High Power Delivery in Immersion Cooling

Author: Oriol, Solutions Engineer, Submer Technologies; Kevin Guerra, Technical Marketing Specialist, Murata Collection: 2023 Global Summit - Cooling Environments

Summary

This presentation covers the OCP Power Distribution in Immersion workstream, which addresses how to deliver high-density power to Open Rack Version 3 (ORv3) hardware inside immersion cooling tanks. The workstream organizes participants into four towers: rack/tank specifications, power shelves and PSUs, bus bar design, and IT hardware power distribution boards (PDBs). The central constraint is preventing AC power cabling from entering the immersion fluid—cables are kept above the fluid surface to eliminate capillary wicking that would drain the tank or create safety hazards. This drives a fundamental design difference from air-cooled ORv3: the power shelf's AC input connector moves from the rear to the top surface.

Empirical connector testing by both Amphenol and Molex found that submerging connectors in dielectric fluid allows approximately 2× the current throughput at the same 30°C temperature rise threshold used for air qualification. For bus bars, a 50 kW air-rated bus bar becomes a 100 kW bus bar in immersion. Power shelves show more modest gains of approximately 1.3–1.4× because the PSU's thermal profile depends on internal component layout, but that still meaningfully increases density. A reference 100 kW tank design is presented using the Submer SmartPodXL with ORv3 compliance: 99 compute nodes at 1 kW each fed by two 54 kW Murata power shelves (15× 3.6 kW PSUs each), with no loose power cables in the tank and no screws that could fall to the tank bottom.

The workstream is actively seeking safety input—specifically guidance on UL and European approval pathways for immersion power supplies, since existing approvals were established for air-cooled environments.