Volume 51

Retrofit design and numerical modeling of bidirectional substations for the empowerment of thermal prosumers in district heating networks Federico Gianaroli, Mattia Ricci, Paolo Sdringola, Mauro Pipiciello, Diego Menegon, Francesco Melino

Abstract

The global energy landscape is undergoing a crucial transition towards renewable energy solutions, underlining the importance of decentralizing energy systems. This complex and long-term process has facilitated the emergence of energy communities, enabling a wide range of actors, including citizens, to actively participate in the energy transition. A key element of this transition is the role of prosumers, individuals who consume and produce energy from renewable sources. Thermal prosumers can be integrated into district heating networks through bidirectional thermal substations, allowing excess thermal energy – produced locally from renewable sources, such as solar thermal systems, or recovered from industrial processes – to be injected into the network.
In this framework, the study introduces a novel approach to adapt traditional district heating substations to bidirectional heat exchange devices, enabling prosumers to actively use thermal energy for their needs and contribute surplus energy to the network. Using an existing network in northern Italy as a case study, an optimized layout in a “supply-to-return” configuration is proposed. To evaluate the performance and potential of the proposed bidirectional device, a detailed numerical model of the substation was implemented in Dymola software for multi-domain simulation. The model was designed to analyze the system’s summer operation, with customized systems and control logics developed from standard library models to accurately reproduce the substation‘s behavior under specific conditions. The results showed that the bidirectional substation allows for the utilization of previously unused thermal potential, due to the mismatch between demand and production, and makes it available to the network, particularly on days with high solar irradiance. This innovative approach finally extends the concept of energy sharing to thermal energy flows, at the community level, opening up new opportunities for a more integrated and sustainable management of energy resources.

Keywords district heating network, bidirectional substation, energy community, numerical modelling, renewable energy source