Smart Reuse of Waste Heat from Data Centres: Energy and Exergy Analysis for a District-Heating Network in Bulgaria
Energies (MDPI AG) · Antonio Verzino, Lorenzo Talluri et al.
Within the EU THUNDER project, the authors run an hourly full-year energy and exergy analysis of a 500 kW air-cooled data centre in Varna, Bulgaria: its condenser heat is upgraded by vapour-compression heat pumps, buffered in thermochemical storage and fed into a real third-generation district heating network with an average demand of 9.3 MW.
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Overview
The rapid growth of data centres is driving higher electricity consumption and continuous generation of low-grade waste heat; integrating this heat into district-heating networks offers a smart thermal-management strategy in urban areas. The study presents an energy and exergy analysis of an integrated system comprising a data centre, vapour-compression heat pumps, thermochemical energy storage and a third-generation DH network. An integrated scenario was compared with a reference where data-centre cooling and DH generation run separately, under two data-centre air-temperature and free-cooling strategies.
Case A used data-centre inlet/outlet air of 20-35 °C with free cooling up to 15 °C outdoor; Case B used 25-40 °C with free cooling up to 20 °C outdoor, both with hot-aisle/cold-aisle layouts. Moving from Case A to Case B cut data-centre cooling electricity from 240.9 to 132.2 MWh (almost 45.0%) through more free cooling. Recoverable waste heat (condenser heat during active cooling only) in Case B is almost 45.0% of that in Case A (1043.1 vs 1985.1 MWh).
Despite its 500 kW size against an average DH demand of 9.3 MW, the data centre can supply 3.0% of annual DH demand and 22.4% of instantaneous load in favourable periods (Case A). Centralised DH heat pumps are cited as giving COP 3-5 for supply temperatures up to 70-80 °C. Thermochemical storage decouples waste-heat availability from DH demand, enabling seasonal shifting, and the integrated configuration consistently raises overall exergy efficiency.
The conclusion is that warmer data-centre setpoints and more free cooling sharply cut the heat that can be recovered, so data-centre and DH operators need to coordinate. Limits: a single small data centre and one DH network (Varna), so results are for this case.
Key points
- Case A used data-centre inlet/outlet air of 20-35 °C with free cooling up to 15 °C outdoor; Case B used 25-40 °C with free cooling up to 20 °C outdoor; both with hot-aisle/cold-aisle layouts.
- Moving from Case A to Case B cut data-centre cooling electricity from 240.9 to 132.2 MWh (almost 45.0%) through more free cooling.
- Recoverable waste heat (condenser heat during active cooling only) in Case B is almost 45.0% of that in Case A (1043.1 vs 1985.1 MWh).
- Despite its 500 kW size against an average DH demand of 9.3 MW, the data centre can supply 3.0% of annual DH demand and 22.4% of instantaneous load in favourable periods (Case A).
- Centralised DH heat pumps are cited as giving COP 3-5 for supply temperatures up to 70-80 °C.
- Thermochemical storage decouples waste-heat availability from DH demand, enabling seasonal shifting, and the integrated configuration consistently raises overall exergy efficiency.
Using it in design
- Set data-centre setpoints (air temperature, free-cooling threshold) together with waste-heat sales: warmer setpoints and more free cooling cut cooling electricity by about 45% but also cut recoverable heat to about 45%.
- Consider seasonal thermochemical or similar storage to decouple waste-heat availability from DH demand.
- In contract design, note that even a small data centre can contribute meaningfully to DH demand (3.0% annual, up to 22.4% instantaneous) but needs coordination between data-centre and DH operators.
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Who should read it
Operators and planners intending to connect data-centre waste heat to third-generation district heating networks.
Document contents
- 1. Introduction (1.1 The Heating Sector: Current Situation and Perspectives of Decarbonisation, 1.2 The District Heating Sector: Evolution and Future Trends, 1.3 Data Centres as Emerging Sources of Waste Heat for District Heating, 1.5 Thermal Energy Storage for Flexible District-Heating Systems)
- 2. Materials and Methods (2.1 Scenario S0: No Integration Between DC and DHN, 2.2 DC Integrated Cooling, Thermal Recovery, and Upgrade, TCS Characterisation and Functioning, 2.3 Exergy Analysis)
- 3. Results and Discussion (3.1 Energy Analysis Results, 3.2 Exergy Analysis Results, 3.3 Further Possible Strategies for Waste-Heat Use, 3.5 Relevance of This Proposal for Low-Temperature District-Heating Networks)
- 4. Conclusions
Related standards
- EU Energy Efficiency Directive (recast)
Read the document
dc-waste-heat-dh-bulgaria-exergy-2026.pdf
CC BY 4.0 — share with attribution
The document is provided unaltered because its licence permits redistribution.
Publication details
- Authors
- Antonio Verzino; Lorenzo Talluri; Andrea Rocchetti; Luca Socci
- Publisher
- Energies (MDPI AG)
- Year
- 2026
- Volume
- 19
- Issue
- 3
- Pages
- 800
- Document language
- English
- Source type
- Scientific
- Access
- Open licence — downloadable
- Licence
- CC BY 4.0 — share with attribution
- Licence evidence
- www.mdpi.com
Original licence note
PDF p.1 states the article is open access under the Creative Commons Attribution (CC BY 4.0) licence; MDPI publishes all articles under CC BY 4.0.
Citation
Antonio Verzino; Lorenzo Talluri; Andrea Rocchetti; Luca Socci (2026). Smart Reuse of Waste Heat from Data Centres: Energy and Exergy Analysis for a District-Heating Network in Bulgaria. Energies (MDPI AG). 19(3), 800. https://doi.org/10.3390/en19030800
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