The first urban underground large-scale water heat storage system

The decarbonization of district heating represents a central element for the success of the heat transition. To sustainably decarbonize piped heat systems in urban areas, sustainable local heat sources such as deep geothermal energy are integrated as well as heat storage is used to increase system flexibility. Bulk water heat storage systems play a crucial role in this. The ScaleUp project has therefore set itself the goal of solving technological issues in this area and setting up a pilot plant in an urban area for the first time.

With the development and construction of a large-scale underground heat storage facility, the ScaleUp project is playing a pioneering role in Austria. This innovative type of storage allows the storage of the surplus of renewable energy available in summer to use it effectively in winter. This method increases the flexibility of district heating networks and ensures a reliable energy supply. The implementation of such storage is considered a key technology for system-integrated and cost-effective decarbonization of district heating systems, and thus a significant step towards the long-term goal of a 100 percent renewable energy system

Positive experience with similar earth basin heat storage systems has already been gained in countries such as Denmark, which is considered a pioneer in the field of large-scale heat storage systems. Compared to Austria, Denmark benefits from favorable geological conditions and low land prices, which makes the construction of such storage facilities less challenging. The ScaleUp project aims to overcome these obstacles in Austria and create the first scalable large-scale underground thermal storage in an urban environme


The main goal of the ScaleUp project is to decarbonize district heating systems. In addition, ScaleUp will help increase the acceptance of such novel structures by addressing specific environmental and social aspects for the site. In the long term, the project aims to achieve a storage volume in the million cubic meter range. In addition, the research initiative supports Austria’s technological pioneering role in underground large-scale water heat storage in urban areas.

Approach and methodology

ScaleUp represents a research project for novel underground tank storage construction methods, which will then be implemented as part of a pilot storage facility. Before the actual implementation, questions regarding water law regulations, system integration into the local district heating network, as well as constructional and material aspects have to be clarified. These will be addressed as part of the detailed design process, which will include developing quality assurance measures that can be used for future storage projects. In order to test the developed technology, a pilot project of an underground tank bulk water heat storage with a volume of about 40,000 m³ will be constructed in the 22nd district of Vienna. This storage will be coupled with large-scale heat pumps to maximize the utilization rate of the energy storage, increase deployment flexibility, and increase the share of renewable energy in the district heating network.


Lisa Sophie Weginger
T: +43 (0)664 88480924

Project key facts

01.02.2023 - 31.01.2026

funding program
Flagship region Energy

Project type
Cooperation project experimental development

Project budget
1.749.931 €

Project management

Wien Energie GmbH

The following model solutions are being developed in the ScaleUp project:

Sample solution/s under development