Simulation of Unglazed Solar Thermal Systems Integrated into Facade & Combined with Ultra-Low Temperature District Heating

This paper presents a theoretical simulation of thermal and economical assessment of facade integrated Solar Thermal (ST) in combination with Ultra Low Temperature (ULT) District-Heating (DH). This paper is in line with existing R&D activities for the integration of unglazed systems in building envelopes, where facades provide an almost unexplored area for increasing solar-activated building envelopes. The combination of building-integrated solar systems with DH networks avoids the use of local storage and allows a novel combination of heat directionality, both from building to the heat grid and vice versa. A control algorithm for heat supply is presented, so that the performance of the overall system is the optimal. Energetic results from solar simulations and economic assessment derived from the balance of building energy demand and solar production are presented. Over a full-year period the proposed unglazed system produces as much as 50% additional heat when compared with an isolated ST system and profitable economic metrics are reached over a simulation time of 20 years. Finally, it is concluded the heat sink nature of a DH network, for as many as 25-35% of the buildings connected to the DH includes ST system.