Smart Reuse of Waste Heat from Data Centres: Energy and Exergy Analysis for a District-Heating Network in Bulgaria

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 strategy for thermal management in urban areas. In this context, this 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 district-heating network in Varna (Bulgaria). The proposed system relies on data-centre waste-heat recovery via vapour-compression heat pumps and thermochemical energy storage, enabling seasonal decoupling between heat availability and demand. Despite the relatively small size of the data centre (500 kW) compared to the district-heating system (average thermal demand of 9.3 MW), recovered waste heat can supply up to 3.0% of the annual heat demand and over 20% of the instantaneous load. The integrated configuration consistently improves overall exergy efficiency, confirming its thermodynamic advantage. These findings show that data centres can act as reliable thermal assets for existing district-heating networks, with heat pumps and thermal energy storage emerging as key enablers for district-heating decarbonisation.