Distinguish between the economic optimal and lowest distribution temperatures for heat-prosumer-based district heating systems with short-term thermal energy storage
Decreasing distribution temperature is the key driving force for energy-efficient and economic-competitive district heating (DH) systems, powering the transition from the 1st generation high-temperature steam-based DH systems to the 4th generation low-temperature water-based DH systems. However, for heat prosumers integrated with thermal energy storages (TESs), the decreasing distribution temperature may lower the peak load shaving capability of TESs and raise the peak-load-related heating costs, due to decreased charging temperature. This study, therefore, aimed to investigate the overall impacts of distribution temperature and to identify the economic optimal distribution temperature for heat-prosumer-based DH systems integrated with short-term TES. Firstly, an economic optimization problem was developed. Afterwards, distribution temperatures were optimized within the feasible regions of individual scenarios, including three benchmark scenarios representing the 2nd, 3rd, and 4th generation DH and an improved scenario featured high feasibility in distribution temperature. A campus DH system in Norway was used as the case study. Results revealed that the improved scenario's economic optimal distribution temperature was significantly distinct from the 4th generation DH scenario's lowest distribution temperature, both in terms of distribution range and annual average level. Finally, broad conclusions were reached by discussing the impacts of crucial factors on economic optimal distribution temperatures.