Assessing the Energy Impact of Integrated Solar Energy Generation in Low-Temperature District Heating and Cooling Systems

District heating and cooling systems are increasingly recognised for their potential in leveraging renewable sources and mitigating greenhouse gas emissions. This study presents an analysis aimed at evaluating the energy-saving potential of integrating solar energy into 5th generation district heating and cooling (5GDHC) systems. These systems, accommodating both thermal and electrical demands, can facilitate the integration of photovoltaic (PV) systems, solar thermal collectors (STC), and photovoltaic thermal (PV-T) hybrid systems. A dynamic simulation framework is implemented in MATLAB, incorporating a zero-dimensional model for the district pipes network, energy balance models for solar technologies and heat pump systems. The space heating and cooling requirements of end-users are evaluated using a reduced-order model based on resistive and capacitive thermal networks. The solar thermal collectors and PV-T systems are used to elevate the evaporator temperatures of electric heat pumps, thereby improving system efficiency. Leveraging the bi-directional thermal exchange in 5GDHC systems, thermal energy can be used to raise network temperatures when the latter are below certain set-points. An energy analysis is conducted to identify the best possible integration of solar energy generation in 5GDHC systems. A proof-of-concept analysis is presented for a 5GDHC system with three user classes – residential and office (consumers), and a datacentre (prosumer) – demonstrating the optimal integration of solar energy from energy and environmental impact perspectives. The results showed that configurations integrating STC / PV-T systems in residential and office buildings can lead to primary energy savings ranging from 24.6% to 52.1%, while integrating PV systems in a data centre achieved remarkable primary energy savings of 36.6%.