Why Open Compute Project innovations heat the city swimming pool?

Author: David Garon, Co-founder, Impon (co-founder Franck unable to attend due to COVID) Collection: 2023 Global Summit - Cooling Environments

Summary

David Garon (Impon) presented a concrete case study from Midon, a suburb of Paris, where an IT boiler (a server-based heat generation system) was evaluated to replace gas boilers heating a municipal Olympic-size swimming pool. The project was triggered by the European energy price crisis: the private company managing 15 swimming pools around Paris could no longer afford the energy costs and transferred the pools to municipal control, forcing the municipality to find cost-effective heating alternatives. The existing heating infrastructure was three gas boilers, each 900 kW (two operating, one reserve), consuming 100,661 m³ of natural gas per year (equivalent to 1,447 MWh), with pool water temperature maintained at 28–31°C (inlet 28°C, outlet 31°C) and gas boiler operating at 32–70°C.

Garon introduced the concept of "Combined Compute" (heat reuse from IT servers) and presented three cooling approach options: (1) air cooling, which produces low-grade heat requiring heat pumps (adding cost and energy consumption) to reach useful temperatures; (2) direct on-chip cooling (cold plate), where well-performing servers can transfer approximately 80% of heat directly from the chip with the remaining 20% via air; (3) immersion cooling, where 100% of heat is already converted to the liquid coolant, which can be delivered directly to the pool heating system without a heat pump. For swimming pool heating specifically, immersion cooling is the ideal solution because the pool water temperature requirements (28–31°C) match the output temperatures achievable from immersion cooling without refrigerant lift.

A 100 kW IT boiler in the energy consumption model would cover 51% of annual pool heating demand, with a dry cooler handling the summer anti-peak (when pool demand drops but servers must continue running). The gas portion (49%) would be retained for peak demand, full pool water replenishment events, and summer maintenance. The analysis also projected national scale: France has 4,000 swimming pools consuming approximately 40 million m³ of natural gas annually (400 million EUR at 1 EUR/m³). If these pools adopted IT boilers using data centers, the CO2 reduction would be approximately 760,000 metric tons. The heat reuse benchmark framework (Software, Hardware, Heat Transfer, Power, Building, Experience) was introduced as a structured way to compare competing solutions.