Transformation Scenarios for High Temperature District Heating Networks with Different Levels of Retrofitted Building Stock: Potential and System Performance Analysis

Kurzfassung

The ‘Climate Change Act 2021’ (Bundes-Klimaschutzgesetz) by the federal government of Germany aims to attain climate neutrality by 2045. To achieve these goals, it is imperative to decarbonise the heating sector (space heating and domestic hot water) which represents about one third of the final energy demands in Germany. District heating systems employ a centralised thermal source to provide distributed heat to a number of consumers through a system of insulated pipes. There are 1454 district heating systems in Germany of which a majority use fossil fuels and operate at high temperatures. This master thesis analyses the possible pathways for transforming the existing high temperature district heating systems (HTDH) to low temperature district heating systems (LTDH). Compared to HTDH, LTDH possess lesser losses and also allow a higher integration of renewables in the system. The main objective of this study is to technically understand the pathways for system transformation when different levels of consumers in the system are retrofitted. With the help of measured data, an existing HTDN is modelled as a base case. Then, various transformation scenarios are investigated and the network performance for these scenarios is analysed. The results found here are presented as guidelines that can be applied at other systems that aim to reduce their operating temperature. Results show that when there are retrofitted consumers in the network, the transformation of an existing HTDN to LTDN is possible without having to retrofit the network. After transformation, the losses from the chosen network in this study can be reduced by 26% when operated as an LTDN. A special case of operation, pulsating mode can further reduce the losses in the network by 27%. The GHG emissions caused due to losses per unit consumer floor area can be reduced from 26 to 19.17 gCO2/m2/day by operating at a lower temperature. Further, by changing the supply source from combined heat and power plant (existing) to a heat pump, the total emissions can be reduced to 10.23 gCO2/m2/day.