A Novel Method for Designing Fifth-Generation District Heating and Cooling Systems

Abstract

District heating and cooling systems have been undergoing continuous development and have now reached the fifth-generation. In this innovative technology, connected buildings share local excess energy that otherwise would be wasted, which consequently reduces primary energy demands and carbon emissions. To date, the issue of implementing fifth-generation district systems on existing buildings has received scant attention, and our research addresses this challenging gap by proposing a novel method for designing these systems. We first explain the possible thermal interactions between connected buildings, and then present an analytical solution for the network energy balance, pipe design, and the prediction of fluid temperature under a fixed temperature difference control strategy. The analytical solution was validated against numerical simulations performed on 11 existing buildings located in Lund, Sweden using Modelica models. A diversity index metric between heating and cooling demands was also included in these models to assess the efficiency of the district system in the building cluster. The results from the analytical and numerical solutions were in complete agreement since Modelica is an equation-based modelling language. The developed models pave the way towards future investigations of different temperature control strategies and new business models that arise from the shift to the fifth-generation.

Methodology for Fifth Generation District Heating and Cooling Network Simulation

“…The evaporator of the heat pump is connected to the condenser of the chiller. This architecture is consistent with former modeling of 5GDHC networks [15], [16]. Following the imbalance between hot and cold demand, the substation can withdraw (dark red arrows) / rejects (dark blue arrows) heat from / in the network.…”

How to develop fifth-generation district heating and cooling in Sweden? Application review and best practices proposed by middle agents

“…The middle agents recommend the use of Modelica language for modeling 5GDHC systems since it offers features, including, but not limited to (i) multi-domain modeling covering thermal, fluid, control, and economic domains, (ii) hierarchical modeling from small components up to the assembly of large district systems, (iii) ability to model bidirectional mass flows, (iv) ability to reuse and/or edit existing component models (object-orientation), (v) acausal modeling where no strict definition of input/output relationships is required, (vi) easy adoption of design changes since the system architecture is retained. Such recommended use of Modelica as a physics-based modeling and dynamic simulation approach for 5GDHC systems confirms the latest findings in the literature (Abugabbara et al, 2020Abugabbara, 2021;Mans et al, 2022).…”

Integration of Renewable Energy Sources into Low-Temperature District Heating Systems: A Review

“…As seen in Figure 3, DHSs have developed over time globally in terms of heat sources, equipment, and building heating systems [42]. The third generation restricts the incorporation of low-heat RES (solar and geothermal energy), which can minimise CO 2 emissions.…”