Heat Reuse

Overview

Heat Reuse refers to the capture and productive use of waste heat generated by data center IT equipment, typically by raising coolant temperatures high enough (50-70°C) to feed district heating networks, industrial processes, or agricultural applications. As data centers transition to liquid cooling with direct-to-chip and immersion systems, the ability to deliver heat at usable temperatures becomes architecturally feasible in ways that were impossible with air cooling. European regulations and sustainability mandates are accelerating interest in heat reuse, particularly in Nordic countries where district heating infrastructure is well-established and the RISE-led HDINI project explicitly targets 60°C heat output from a 1 MW hybrid liquid-cooled rack for Swedish district heating integration.

The key technical challenge is operating IT cooling loops at temperatures high enough for downstream heat consumers (typically 60°C supply) while maintaining acceptable chip junction temperatures and cooling system reliability. This requires coolants with favorable thermal properties at elevated temperatures, heat exchangers optimized for the temperature gap between TCS and district heating returns, and system designs that minimize the number of heat exchange stages. Single-loop architectures (eliminating intermediate heat exchangers) are the preferred approach, enabled by bio-based fluids such as Bio PDO25 developed by Impleon and Frigel. Heat reuse is a key pillar of data center sustainability strategy, and the liquid cooling market's trajectory toward ~$55-60B by 2035 is partly driven by operators seeking to monetize waste heat.