Abstract
The European Union highlights the crucial role of district heating and cooling, prompting innovations for prosumer-driven energy communities. The significance of thermal prosumers lies in their ability to contribute to the district heating network by utilizing locally sourced energy from renewables or industrial processes, thereby reducing fossil fuel usage, and enhancing district heating sustainability. In this framework, the document outlines an innovative approach aimed at establishing a pre-commercial setup for retrofitting traditional substations in bidirectional substation for district heating networks. These devices allow prosumers to actively consume thermal energy for their internal needs and share any surplus to the network. Based on an existing network in northern Italy, an optimized layout is proposed in a “supply-to-return” configuration: it includes a heat exchanger at the interface between the end-user and the network, supplying space heating and domestic hot water through thermal storage, which can also be charged by the distributed generation system (i.e., solar panels). An additional heat exchanger is intended to feed the network with surplus energy locally produced. To assess the performance and advantages of the proposed setup, an extensive experimental campaign was conducted, modifying, and integrating a pre-existing substation prototype in real-time with data-driven thermal loads and production profiles using the hardware-in-the-loop technique. The results show that while the deployment of evacuated tube solar collectors may not have significantly impact in term of local selfconsumption in comparison to flat collectors due to energy demand disparities, it does offer a notable advantage in terms of energy fed into the network. This advantage is nearly 25 times greater than that of flat panels, particularly noticeable during winter days. This results in a significant advantage at the local level as well, enabling the achievement of 100% self-consumption when the DHN serves as thermal storage, especially during mid-season days. These findings underscore the effectiveness of evacuated tube collectors in maximizing energy utilization and reinforcing the role of bidirectional substations in promoting renewable energy integration within urban heating systems.