Integration impacts of low temperature sub-networks on existing district heating networks - a Swedish case study

Abstract

As the need to reduce CO2 emissions from the heating sector to meet climate targets grows solutions such as the electrification of heating and low temperature district heating are becoming prevalent. To achieve such emissions reductions within significantly decarbonised district heating networks, it is of increasing importance to evaluate the emissions from electricity production, including the hourly and seasonal variation inherent there. Using a new district in Stockholm, Sweden, as a case study this work examines the interactions between an existing high temperature network and a new, linked, low temperature network serving a temperature efficient district. Particular focus is placed on the effect of heat recovery opportunities created by the new low temperature district on the existing network and peak heat requirements from the existing network, the net CO2 emissions after heat recovery and electricity use, as well as the electrical intensity of heat supplied to low temperature district. After modeling the building heat demands with PlanHeat and simulating the low temperature network in the python environment utilising PandaPipes and the PuLP optimiser, it was found that the emissions reductions depend significantly both utilisation of heat recovery opportunities and the electrical intensity of heating. In addition, it was found that the lowest overall emissions came from the utilisation of waste heat within the existing DHN, while the highest came from the utilisation of an electrically driven sea-source heat pump.