case studies

Integrating Ice Storage into Vienna’s District Cooling Network

In July 2025, Wien Energie commissioned its eighth major district cooling centre, located beneath the new campus of the Medical University of Vienna. This project marks a technical milestone with the installation of Vienna’s first large-scale underground ice storage system, introduced to enhance efficiency and load balancing across the city’s growing cooling network.

Objectives

  • Expand the district cooling network to serve key public institutions.

  • Integrate thermal storage to manage cooling demand more efficiently.

  • Improve climate resilience in response to Austria’s rising number of tropical nights.

  • Bridge isolated areas of the existing cooling grid to support long-term network integration.

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Technical Summary

This project lays the groundwork for further integration of thermal storage across the district cooling network. It also reflects broader European efforts to reduce urban heat stress while improving the energy performance of essential infrastructure.

The new cooling centre supports the energy demands of the Medical University, which will accommodate approximately 750 employees and 2,000 students by 2027. The site includes laboratories with continuous cooling needs, placing year-round demands on the system.

To address peak demand and reduce system strain, Wien Energie incorporated a large ice storage unit into the cooling infrastructure. The system enables the production of chilled water during off-peak periods—particularly at night—by forming a substantial ice reserve underground. This stored thermal energy is then discharged during high-demand periods, such as hot summer afternoons, allowing chillers to run at steady loads rather than cycling excessively.

The ice storage installation supports:

  • Greater load balancing

  • Improved energy efficiency

  • Reduced carbon emissions compared to conventional systems

Strategic Significance

The project plays a key role in the continued expansion of Vienna’s district cooling network, with the new plant forming a vital connection point between the city’s inner ring and the existing infrastructure in Spittelau and AKH Hospital. This forms part of Wien Energie’s longer-term strategy to move from isolated cooling nodes to a fully integrated urban grid.

According to Wien Energie CEO Michael Strebl, the investment reflects the city’s urgent need to manage extreme heat events. Strebl highlighted the sharp rise in tropical nights—defined as nights where temperatures remain above 20°C—rising from an average of 1.6 annually between 1960 and 1991 to around 50 in 2024.

By 2030, Wien Energie plans to invest €90 million in the further development of the district cooling network, with the Medical University campus facility setting a precedent for future installations.

Outcomes

  • Commissioned the first ice storage system within Vienna’s district cooling infrastructure.

  • Improved system resilience and energy management for high-demand periods.

  • Strengthened network connectivity between previously isolated cooling hubs.

  • Supported Austria’s carbon reduction efforts by lowering reliance on conventional air conditioning technologies

Project Partners

  • Wien Energie – Project lead and infrastructure provider
  • Federal Real Estate Company (BIG) – Real estate and development partner
  • Medical University of Vienna (MedUni) – End user and primary customer

Future Plans

This project lays the groundwork for further integration of thermal storage across the district cooling network. It also reflects broader European efforts to reduce urban heat stress while improving the energy performance of essential infrastructure.

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