Techno-economic and environmental performance of two state-of-the-art solar-assisted district energy system topologies

• Published in: Energy (Oxford) 2023-08, Vol.276, p.127638, Article 127638
• Main Authors: Brunt, Nicholas, Duquette, Jean, O'Brien, William
• Format: Article
• Language: English
• Subjects: District cooling; District heating; Low-temperature district energy; Techno-economic
• ISSN: 0360-5442
• DOI: 10.1016/j.energy.2023.127638

This study introduces a novel, ambient-temperature district energy system topology that enables bi-directional mass flow to booster heat pumps and includes distributed solar-thermal generation. The ambient system topology is described and a detailed model is developed in MATLAB-Simulink. An equivalent model is developed for a conventional, supply-return district system utilizing hot (75 °C) and chilled (15 °C) water, allowing for the direct comparison with the proposed system—with and without solar-thermal integration—in technical, environmental, and economic analyses. Annual simulations are conducted for the case study: an existing network in Ottawa, Canada with 12 commercial buildings. The ambient system achieves a system coefficient of performance of 1.40 without solar assistance and 1.43 with solar assistance. The conventional system achieves coefficients of performance of 1.26 and 1.28, respectively. The solar fractions of the ambient and conventional systems are 5.5 and 4.0% for heating and 9.3 and 10.0% for cooling, respectively. The ambient system without solar decreased annual carbon emissions by 32.16% relative to the conventional system, a significant improvement. While the ambient system's levelized cost of energy is higher both without solar (8.1 vs. 6.0¢/kWh) and with solar (11.0 vs. 9.2¢/kWh), the ambient system is less expensive if carbon pricing is considered. •Ambient-temperature, bi-directional district energy system topology is proposed.•Ambient system includes heat pumps and optional solar-thermal assistance.•Techno-economic performance is compared with conventional network via modelling study.•Ambient system achieves superior technical and environmental performance.