Evolution of heating substation: from steam systems to thermal prosumers

Heating substations are a key component of district heating (DH) systems, enabling the efficient transfer, regulation, and optimization of thermal energy flows between centralized energy sources and building-level consumption systems. This article provides a comprehensive overview of the evolution of heating substations, tracing their development from early high-temperature steam networks to today’s advanced, low-temperature, and digitally controlled systems. A particular focus is placed on bidirectional heating substations — the latest stage of this evolution — which integrate local renewable and residual heat sources (heat pumps, solar thermal collectors, industrial waste heat) alongside traditional DH infrastructure. Such substations not only allow flexible heat consumption from the DH network but also provide the capability to inject surplus thermal energy back into the grid. This supports the transition towards thermal prosumer models, where consumers become active participants in local energy balancing, helping to improve system-wide flexibility, increase the share of renewables, and contribute to significant CO₂ emission reductions. The article reviews technical solutions and control strategies for implementing bidirectional substations and assesses their role in transforming DH networks into more intelligent, decentralized, and low-carbon energy infrastructures. These developments are in line with the strategic goals of the revised EU Energy Efficiency Directive (EU/2023/1791), which emphasizes the modernization of heat supply systems as a key pathway to achieving climate neutrality. The results underline the potential of bidirectional heating substations technologies to serve as critical enablers for sector coupling and for the future integration of heating into holistic smart energy systems.