A comprehensive techno-economic analysis of solar energy integration in low-temperature district heating and cooling systems

This study investigates the integration of solar technologies and energy storage at the individual building level within fifth-generation district heating and cooling networks. Nine distinct building configurations are evaluated, incorporating photovoltaic (PV) systems, solar thermal collectors, photovoltaic-thermal (PV-T) systems, thermal energy storage (TES), and electric batteries. The techno-economic performance of these configurations is assessed for three user types: data centres (thermal prosumers) and residential and office buildings (thermal consumers). To capture dynamic interactions among thermodynamic components, an integrated thermal model is developed using an object-oriented methodology. Key findings for a case study in northern Italy show that combining PV systems with solar thermal collectors and energy storage results in primary energy savings of 57 % for residential buildings and 55 % for offices, compared to a reference scenario without solar technologies. Replacing PV systems with PV-T systems of equivalent area eliminates the need for solar thermal collectors, achieving over 50 % space savings. From a techno-economic perspective, the configuration for residential buildings that combines PV systems, solar thermal collectors, batteries, and TES achieves a payback-time (PBT) of 18 years without electricity exports, reduced to 14 years when excess electricity is exported. For offices, the PV-T system proves more cost-effective, achieving a PBT of 14.6 years, reduced to 11 years with electricity exports. The PBTs observed for the PV-only configuration are 5.9 years for offices and 5.8 years for the data centre. In the community-based approach, where investments are made collectively by users, PV-T systems achieve a low PBT of 6.4 years.