System Integration of a Computing Cluster, a Heat Recovery System and an Adsorption Chiller for Cold Production (OCP EMEA Summit 2025, Future Technologies Symposium)
Open Compute Project Foundation · Remi Bouzel
This Qarnot presentation describes coupling 65 C rack waste heat to a silica-gel/water adsorption chiller to produce 15 C chilled water.
On this page
Overview
The presentation was given by Remi Bouzel at the OCP EMEA Summit 2025 (Dublin), in the Future Technologies Symposium session on Data Center Sustainability. Qarnot is an HPC cloud provider that builds heat-reuse racks on OCP hardware, and it describes coupling its 65 C rack waste heat to a silica-gel/water adsorption chiller to produce 15 C chilled water.
The deck first compares the carbon footprint of a conventional 5 MW site with one reusing its heat, using PUE and ERE: PUE 1.6 / ERE 1.6 for the conventional data center and PUE 1.05 / ERE 0.10 for the heat-reuse data center. These figures are a scenario comparison, not measured site data. It then walks through the adsorption cycle and an experimental rig of about 8 kW.
The adsorption chiller is thermally driven; the heat source can be as low as 65 C, using a silica gel/water pair. The cycle temperatures shown are 65 C hot water drive, 25 C cooling water and 15 C chilled water. The experimental rig uses about 8 kW of compute electricity and 0.1 kW of pumps, with 65 C IT waste heat feeding the chiller.
The aim was to quantify cold production per computing load without harming PUE/ERE. Next steps include raising technology readiness and supporting adsorbents that regenerate below 65 C. This shows how low-grade heat can serve cooling demand when no heat customer exists. The work is at an experimental stage and the results belong to a single rig. ISO/IEC 30134-6 (ERF) is named as a related standard.
Key points
- Scenario for a 5 MW site: conventional DC PUE 1.6 / ERE 1.6 versus heat-reuse DC PUE 1.05 / ERE 0.10.
- The adsorption chiller is thermally driven; the heat source can be as low as 65 C, using a silica gel/water pair.
- Cycle temperatures: 65 C hot water drive, 25 C cooling water, 15 C chilled water.
- Experimental rig: about 8 kW of compute electricity, 0.1 kW of pumps, 65 C IT waste heat feeding the chiller.
- The aim was to quantify cold production per computing load without harming PUE/ERE.
- Next steps: raising technology readiness and adsorbents that regenerate below 65 C.
- Low-grade heat can serve cooling demand when no heat customer exists.
- Related standard: ISO/IEC 30134-6 (ERF).
Using it in design
- In heat-reuse modelling, allow an adsorption-chiller sink with a minimum drive temperature (around 65 C).
- Check whether the chosen liquid-cooling return temperature is high enough.
- Report ERE alongside PUE when heat is exported.
- For sites with no heat customer, consider cold production as a heat-use option.
- Set up a reporting structure compatible with ISO/IEC 30134-6 (ERF).
Monthly newsletter · free
Keep your reading list current
Once a month: new library sources, changes to Turkish regulations and upcoming data centre events.
SoSo CAD
Compare the cost of design decisions
Evaluate equipment costs, energy expenses and total cost of ownership (TCO) using your inputs and assumptions in SoSo CAD.
Request a demo
Who should read it
Mechanical designers and sustainability leads who weigh heat recovery and liquid cooling together with sustainability metrics.
Related standards
- ISO/IEC 30134-6 (ERF)
Publication details
- Authors
- Remi Bouzel
- Publisher
- Open Compute Project Foundation
- Year
- 2025
- Document number
- OCP EMEA Summit 2025, FTS Data Center Sustainability
- Event
- OCP EMEA Summit 2025, Dublin
- Document language
- English
- Source type
- Industry body
- Access
- Free to read
- Licence
- Copyright retained; citation only — the publisher’s terms apply to the original document
Citation
Remi Bouzel (2025). System Integration of a Computing Cluster, a Heat Recovery System and an Adsorption Chiller for Cold Production (OCP EMEA Summit 2025, Future Technologies Symposium). Open Compute Project Foundation. OCP EMEA Summit 2025, FTS Data Center Sustainability. OCP EMEA Summit 2025, Dublin. https://drive.google.com/file/d/1kIs1xzI5EgvnQ9Hllwk0Zv2c0O63XpTF/view
Events on this subject
Browse the events calendarAll content and rights belong to the respective authors and publishers. SoSo CAD provides only the citation, its own summary and a link to the source, and is not responsible for the sources' content.
Related sources
All sources on this topicSchneider Electric 2025
10 Data Center Sustainability Improvements Quantified by Environmental Impact
In the sustainability panel compute operational CO2e = IT MWh x PUE x grid EF, with a grid-EF catalog by country/region (default US 454 kg CO2e/MWh incl. upstream) and a renewable-PPA toggle.
- Total GHG falls from 84,100 to 11,300 t CO2e (-87%).
Huawei Digital Power 2023
White Paper on the Top 10 Trends of Data Center Facilities
Show WUE alongside PUE in the metrics panel, with region-specific targets as policy presets.
- At 16 kW per rack, power-room area roughly equals IT space (1:1).
NREL 2018
DCDM1: Lessons Learned from the World's Most Energy Efficient Data Center (NREL/PR-2C00-70433, March 12, 2018)
Fix two design temperatures early, the coolest supply you can produce on the hottest day and the return temperature needed for heat reuse, and select IT equipment against them.
- Ten 100-kW racks take much less space than the equivalent fifty 20-kW air-cooled racks.
Open Compute Project Foundation 2025
Reference Designs for Data Center Heat Reuse, Revision 1.0
Provide a heat-recovery-station block in the site layout with space sized from capacity (plate HX footprint, 10 m2 per MW for heat pumps, about 43 m3 per MW per 30 minutes of storage) and a demarcation boundary to the heat host.
- ORC heat-to-power converts less than 4% of the heat to electricity at these low temperatures.
Open Compute Project Foundation 2024
Data Center Facility Sustainability Metrics (OCP Data Center Facility white paper, October 2, 2024)
Build the metering plan so that PUE can be reported at the highest category possible, with IT load measured at PDU or equipment input rather than the UPS output where feasible.
- External reporting is annual (required) and quarterly on a trailing 12 months (recommended); internal tracking should be continuous or monthly.
Open Compute Project Foundation 2025
Heat Reuse Subproject Update (OCP EMEA Summit 2025)
Site and compliance rules should hold jurisdiction-specific targets (for example Germany: PUE 1.2 for new builds and 10-20% ERF).
- Related documents: Directive (EU) 2023/1791, German Energy Efficiency Act (EnEfG) and ISO/IEC 30134-6 (ERF).