Innovative Thermal-Hydraulic Model for Waste Heat Recovery in District Heating Networks

A recent study by Eurac Research in cooperation with Politecnico di Torino, University of Naples, and Cogeme Energia, published in the scientific journal Energy, investigates a thermal substation designed for low-temperature waste heat recovery in district heating networks, where the served user has both heating and cooling demands.

The proposed bidirectional substation, equipped with heat pumps and thermal storage units, enables the recovery of excess waste heat in the district heating network and compensates local heating needs when waste heat availability is insufficient. A flexible and detailed TRNSYS-based model is developed to simulate various hydraulic configurations of the substation, tailored for both low- and high-temperature district heating networks, ensuring adaptability to different temperature requirements in diverse applications.

The model is applied to a demonstration site in Ospitaletto, Italy, where waste heat is recovered from a steel mill and used to replace gas boilers for space heating and hot water in the factory's canteen and showers. The model's accuracy is validated through a comparison with monitored data, ensuring reliable performance predictions. Performance estimation error is under 5%, demonstrating the model's high reliability.

The simulation results show that the system can achieve up to 75% reduction in non-renewable primary energy consumption and carbon emissions, while also allowing the recovery of about 90% of unused waste heat for supply to other connected users. The study presents the development and validation of a detailed thermal-hydraulic model of a bidirectional substation for integrating low-temperature industrial waste heat into district heating (DH) networks.

The substation, equipped with heat pumps and thermal storage, can recover and reuse local waste heat to meet on-site demand, while its bidirectional connection to the district heating network allows both the injection of surplus heat into the network and the extraction of heat when local waste heat is not available.

"Eurac Research led the simulation work, developed the dynamic model, and validated it with real monitoring data. The team also carried out a scenario analysis to assess seasonal performance and the impact on the wider network. Compared to previous literature, this work offers a more flexible and detailed model, capable of simulating various hydraulic configurations and control strategies. Results show up to a 75% reduction in non-renewable primary energy use and CO₂ emissions, and the recovery of about 90% of unused waste heat, which can be made available to other users connected to the district heating network" explains Daniele Anania, first author of the study.

This work is part of the LIFE4HeatRecovery project, coordinated by Eurac Research. Here the link to the original article