A system-integrated and cost-efficient decarbonization of district heating systems, especially in urban areas, can be accomplished by integrating renewable local heat sources in combination with large-scale heat storages thereby increasing system flexibility and heat generation capacity in the cold seasons. The objective of the project “ScaleUp” is to develop solutions for currently existing bottlenecks in the implementation and construction of large-scale underground tank thermal energy storages, thereby increasing scalability. More precisely, the aim is to demonstrate their applicability for the near future by the investment funding pilot project (called ScaleUp – demo Vienna 22) in an urban heating network, in Vienna’s 22nd district. In addition to the seasonal storage of renewable surplus (e.g. of deep geothermal energy or solar thermal energy), the storage can store the thermal energy from different waste heat sources for short- and medium-term periods. Further key objectives of the project are the development of energy management aspects and digitization topics related to sector coupling (P2H, participation in the electricity market) as well as optimization measures to increase the flexibility of the district heating system and the development of corresponding business models.