ScaleUp
The first urban underground large-scale water heat storage system - A consortium led by Wien Energie is exploring the possibilities for constructing an underground heat storage system, which is expected to be constructed in Vienna’s 22nd district in the medium term.
The decarbonization of district heating is a key element for the success of the heat transition. To sustainably decarbonize piped heat systems in urban areas, both sustainable local heat sourcess uch as deep geothermal energy and heat storage systems are needed to increase system flexibility. Large-scale water-based heat storage systems can play a crucial role in this regard. The ScaleUp project has therefore set itself the goal of addressing technological challenges in this area and constructing a pilot plant in an urban setting for the first time.
With the development and construction of a large-scale underground heat storage system, the ScaleUp project is playing a pioneering role in Austria. This innovative type of storage allows for the storage of surplus renewable energy generated in the summer so that it can be effectively used in winter. This method can increase the flexibility of district heating networks and make a decisive contribution to a reliable energy supply. The implementation of such storage systems is considered a key technology for the system-integrated and cost-efficient decarbonization of district heating systems, and thus a significant step toward the long-term goal of a 100-percent renewable energy system.
Positive experiences with similar earth-based heat storage systems have already been gained in countries such as Denmark, which is considered a pioneer in the field of large-scale heat storage. Compared to Austria, Denmark benefits from more favorable geological conditions, more uninhabited open spaces near existing district heating networks, and low land prices, making the construction of such storage systems less challenging. The ScaleUp project aims to overcome these obstacles in Austria and create the first scalable large-scale underground heat storage system with usable surface area in an urban setting.
Objective of the ScaleUp project
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.
The ScaleUp project aims to contribute to the decarbonization of district heating systems. In addition, the pilot project aims to increase acceptance of such innovative structures by addressing specific environmental and social aspects relevant to the site. In the long term, the project aims to enable storage facilities with volumes of several 100,000 cubic meters. Furthermore, the research initiative supports Austria’s technological progress in the construction of large-scale underground heat water storage systems in urban areas.
Underground storage solutions for the energy transition
“ScaleUp” is a project aimed at developing a novel underground earthen reservoir storage design, which is to be implemented for the first time in practice as part of a pilot project. In the course of the research and subsequent project development, key issues have already been thoroughly addressed. These include, in particular, the legal framework, the integration into the local district heating network, and the structural and material requirements. In collaboration with experts from the construction industry, quality assurance measures for the construction phase were also developed, which can serve as a basis for future underground storage projects. In addition, a comprehensive monitoring plan was developed that takes into account both potential environmental impacts and the ongoing energy and process monitoring of the storage system. This not only ensures safe and sustainable operation but also makes the efficiency gains of the overall system transparent.
To test the developed technology, a demonstration project with a volume of approximately 40,000 m³ and a depth of about 30 meters is planned in Vienna’s 22nd district. The pilot storage facility is to be coupled with a large-scale heat pump to maximize efficiency, increase operational flexibility, and further expand the share of renewable energy in the district heating network.
As part of the project development, various insulation materials were also successfully tested to store excess heat at temperatures of up to 95 °C as efficiently as possible and with minimal loss. In addition, an innovative cover design was developed that provides a usable surface. In this form, the planned construction method represents a European first and sets new standards for urban heat storage.
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The following model solutions were being developed in the ScaleUp project:
Integration of an underground water tank as heat storage for a DH grid
Media reports on the project
ScaleUp: Vienna plans first underground mega heat storage facility – energy innovation austria
The integration of large heat storage facilities to temporarily store excess heat from renewable sources is considered a key technology of the decarbonisation of district heating. A consortium led by Wien Energie is currently researching the construction of a large underground heat storage facility, which is to be built in the medium term at the Donaustadt power plant site.
To the articleUnderground basins complement the heating infrastructure – VorBuilder Das Magazin des Klima- und Energiefonds
The heating and energy supply plays a key role, which should no longer rely on fossil fuels but on renewable energy sources in future. Wien Energie is therefore investing in the expansion of district heating, with far-reaching changes – literally: in future, energy will also be stored in underground reservoirs for the heating season.
To the articleScale-UP: Large heat storage in the district heating network of the City of Vienna
Presentation by Rusbeh Rezania from Wien Energie on the “Scale-Up” project on the occasion of the national information day on the EU Innovation Fund 2025, which took place on 23 January 2025 at the House of the European Union in Vienna.
To the articleScaleUp: The first urban underground large-scale water heat storage system – Website of Wien Energie
A big step towards the decarbonisation of district heating! The ScaleUp project is involved in the construction of the first large-scale underground heat storage system in an urban area and is thus helping to drive forward a renewable heating system.
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