Physics-based numerical modelling of a multiple-mode operational strategy for district heating systems: case study in a small neighbourhood

• Intraday multiple-mode strategy with end-user storage for 3G DH retrofits. • Integrated physics-based DH model captures network–substation interactions. • Multiple-mode strategy reduced annual heat loss by ∼ 12 % compared with 3G DH. • CHP electricity use reduced by 13% and exergy efficiency increased by 4.2%. • Timer valves cut bypass circulation ∼ 99.5 %; DHW met without auxiliaries. District Heating (DH) networks increasingly face the dual challenge of lowering distribution temperatures to cut heat losses and integrate low-grade sources, while still ensuring hygienic domestic hot water delivery. This problem is addressed in this study by proposing a structured, intraday Multiple-Mode DH (MMDH) strategy that schedules brief high- and medium-temperature windows for charging small end-user storage tanks for domestic hot water, followed by extended low-temperature operation for space heating. This goes beyond prior adaptive or weather-compensated controls by prescribing a time-scheduled regime coupled to decentralized storage and timer-valve logic. Hence, physics-based numerical models were developed for pipes, substations (including stratified tanks and valves), and heat exchangers in a SIMULINK® system model, drive it with stochastic, building-derived demand profiles, and compare MMDH against a Third-Generation (3G) baseline on an illustrative 22-dwelling network. Over a one-year simulation, total source energy decreased by 3.8 % (from 1,595 to 1,534 GJ yr −1 ), network heat losses declined by approximately 12 % (from 125 to 110 GJ yr −1 ), CHP electricity losses fell by approximately 13 % (from 11,858 to 10,313 GJ yr −1 ), and the mass circulated through thermostatic bypass valves dropped by approximately 99.5 % (from 219 to 1 Mg yr −1 ). Exergy-based assessment indicates an average exergy-efficiency improvement of ∼ 4.2 %, consistent with the lower supply-temperature operation. Crucially, domestic hot water demand was fully met without auxiliary electric heating.