Academic landscape on sharing renewable and waste heat in active district heating: A systematic literature review

The heating and cooling sector accounts for a significant share of energy consumption and greenhouse gas emissions, and district heating and cooling (DHC) systems are seen as promising decarbonization solutions, requiring their renovation and evolution toward more flexible and integrated configurations. Decarbonising DHC requires integrating renewable energy and waste heat, reducing fossil fuel dependence and increasing community engagement. Bidirectional flows and prosumers should be further explored to enhance system flexibility, as these concepts are well established in electricity but still underexplored in thermal systems. This work focuses on the emerging set of approaches aimed at decarbonising District Heating systems, collectively referred to as Active District Heating (ADH), through a systematic review of 171 scientific articles. The study provides a clear conceptual framework to analyse how the research community approaches ADH models, structuring the literature across methodological approaches, technologies, digitalization tools, and regulatory aspects. The results indicate that ADH is emerging as a flexible, digitalised, and potentially bidirectional network paradigm, largely established at the theoretical level, with 76% of studies based on modelling and simulation, while practical applications in real systems or pilot-scale demonstrations remain limited (11%). The literature is strongly concentrated in Europe (85%), with key enabling solutions including waste heat recovery (48%), heat pumps (39%), and solar thermal collectors (33%), while around 20% of studies analyse the end-user–network interface for thermal prosumers. Finally, regulatory uncertainty and the lack of clear third-party access mechanisms, together with geographical and policy disparities, are identified as the main barriers affecting ADH development.