Simulation of distribution system for low temperature district heating in future urban areas – Case study of a planned city district in Gävle

Abstract

In Europe, the prices of natural gas and electricity reached an all-time high in 2022. A way to mitigate high electricity costs is to expand district heating systems in urban areas, this will reduce electric load as well as increase the power generation possibilities in combined heat and power plants. District heating has been the dominant heat supply technology in urban areas in Sweden since the 1980s. However, as the energy efficiency in buildings increase, district heating distribution losses must be reduced to ensure a cost-efficient heat supply. This has led to the idea of the 4th generation district heating which is characterized by low distribution temperatures. In this study, low-temperature district heating distribution in a planned future city district is simulated using a Python-based tool. Two different low-temperature distribution systems are investigated: 1) 2-pipe low-temperature system, and 2) a cascading 3-pipe low-temperature system. The focus is on simulating the distribution losses, temperature drop, and mass flow in the pipe network. The scope of the analysis also includes an investigation of the effect of lower return temperatures on the central district heating network. The results indicate that the low-temperature distribution system with the 2-pipe system performs better than the cascading system when considering distribution losses and temperature drop. The mass flow depends on the temperature demand in the heating systems in the buildings and is considerably high for both low-temperature distribution systems investigated.