Supra-Regional District Heating Networks: Harnessing Industrial Waste Heat for a Low-Carbon Heat Future

The heat sector is the most energy-intensive sector globally, accounting for nearly 48 % of the world¿s total final energy consumption in 2021. Additionally, it was responsible for 38 % of total CO2-emissions. Within this sector, 53 % was attributed to industrial heating processes, 44 % to hot water and space heating, while the remaining share was assigned to agriculture. This highlights the urgent need for a technological transformation in the heat sector to significantly reduce CO2-emissions. Various technologies, such as heat pumps, geothermal energy, solar thermal energy, biomass, and the utilization of waste heat from industrial processes, offer promising approaches. This work aims to explore the integration of existing district heating systems, which currently operate as isolated networks across different regions, into larger, interconnected heating supply systems, forming supra-regional district heating networks similar to the high-voltage transmission grid in the electricity sector. It provides a comprehensive investigation into the modelling, assessment, and evaluation of such networks. This thesis presents a new model that enables precise and efficient modelling of heat load flow. In addition, it introduces key performance indicators with defined thresholds to evaluate the technical and economic aspects of such systems within a comprehensive techno-economic analysis. The security of heat supply is also assessed using a dedicated analytical approach. The methodologies and models developed are used to investigate the feasibility of a supra-regional district heating network in Styria, Austria. The findings indicate that such networks are technically viable and beneficial, primarily due to the high linear heat density and the resulting low transmission losses. The integration of multiple district heating providers into a single supra-regional network necessitates a new pricing approach to ensure fair cost distribution between suppliers and consumers. To address this, the thesis proposes a novel pricing model based on a merit-order system using Levelized Costs of Heat. The outcome of this work indicates that both renewable and sustainable heat producers, as well as end consumers, could benefit from supra-regional district heating networks, provided the assumptions of the novel pricing model are considered. Additionally, by utilizing and consolidating industrial waste heat in regions with energy-intensive industries, a significant amount of CO2-emissions could be saved. In summary, this work provides a positive response to the question of whether supra-regional district heating networks utilizing industrial waste heat could be technically and economically viable. However, the establishment of new markets and large-scale infrastructure raises many new research questions that should be explored in future studies.