Developing an active heat recovery system to boost data centre waste heat utilization: a novel and cost-effective solution for building decarbonisation

Data centre (DC) waste heat recovery for district-heated buildings often relies on costly heat pumps. However, the rise of liquid-cooled distributed/edge DCs driven by increasing computational demand offers new potential for cost-effective onsite recovery. These systems produce higher-temperature waste heat, making heat exchanger-only solutions more feasible. Yet full recovery remains challenging due to high return water temperatures in building heating networks and the passive nature of such systems. To overcome these limitations, this paper proposes an active DC waste heat recovery system (AHE-DCWHR) that enhances heat exchanger-only solutions through an innovative heating demand reallocation strategy. This strategy utilizes a small heat pump (1) to precool the return water of one heating network before entering the heat exchanger, increasing the inlet temperature difference to enable near-complete waste heat recovery, and (2) to reuse the extracted precooling energy to heat another network, minimizing losses. AHE-DCWHR was validated in TRNSYS through 25-year life-cycle cost (LCC) and emission analyses for a liquid-cooled DC suppling 25 kW of waste heat to a district-heated building. During the 5-month winter, AHE-DCWHR consumed only 7.5 MWh of electricity for the heat pump (average COP = 4.75), enabling the heat exchanger to recover 98.4 % of the waste heat (∼90 MWh), a 16 % improvement over the heat exchanger-only system (75.1 MWh). Based on 25-year LCC and emission analyses, it saves €123,431 heating costs (vs. €106,501 for the heat exchanger-only system), cuts CO2 emissions by 167,087 kg (vs. 134,711 kg), and achieves a two-year payback. AHE-DCWHR cost-effectively outperforms heat exchanger-only and heat pump systems.