Vienna thermal water will be used twice in future



After being used internally, the thermal water of Therme Wien now heats a district in Vienna with climate-neutral district heating. The concept for local waste heat utilisation developed in the ThermaFLEX lead project goes into operation.

As part of the ThermaFLEX project, AEE INTEC is working with 27 project partners on the question of how district heating networks can be made more flexible and efficient, and how they can operate without fossil fuels. Within the project, it has been possible to implement versatile demonstration projects and to accompany them scientifically. One of these demonstration projects includes the systemic integration of a heat pump at the Therme Wien site and the utilisation of waste heat for Vienna district heating in the Oberlaa district. On 9 May 2022, those responsible for the project invited guests to a presentation of the concept.

From now on, the warm water in the pools of Therme Wien will not only provide relaxation: Wien Energie has built a heat pump system there and uses the waste heat of the thermal wastewater to generate district heating. The thermal spring, which has been used by Therme Wien since the mid-1950s, has thus been given another function with this project.

The utilisation of waste heat from different sources represents an important building block for the decarbonisation of heating networks. The object of this implementation is the exergetically sensible integration of a heat pump concept based on waste heat from the Therme Wien in Vienna-Oberlaa. After the internal use of the thermal water by Therme Wien, the residual heat still in the water (at a temperature level of around 30°C) serves as a heat source for the waste heat utilisation concept.

Two identical water-cooled compact heat pumps were designed to feed about 2.2 MW of power at a temperature of up to 85°C into the local district heating network in Oberlaa all year round. With an additional Power2Heat system, the temperature can be further increased (if necessary or if the outside temperature is below -5°C). The system was installed in the Therme’s underground car park and connected to the city’s electricity grid. In the future, the large heat pump system will provide green heat for about 1,900 households in Oberlaa and save about 2,600 tonnes of CO2 annually.

(c) Wien Energie/Harald Ströbel

“This kind of waste heat utilisation offers enormous multiplication potential for the entire district heating sector. The use of the waste heat that is still available is a prime example of cascading energy generation and a circular economy” emphasises ThermaFLEX project manager Joachim Kelz.

The ThermaFLEX project and the project partners involved, first and foremost Wien Energie, AEE INTEC and AIT, have contributed significantly to the concept development and implementation. The system will continue to be scientifically monitored within the framework of the project in order to find operating optima on the one hand and on the other hand to use the operating experience generated in this way for further technology multiplications. The investment of around 3 million euros in the system is supported with funds from the Ministry of Climate Protection’s environmental promotion programme.

Key data:

  • Power: around 2 megawatts
  • Annual heat production: 11 gigawatt hours of heat
  • Environmentally friendly district heating for around 1,900 households in Oberlaa
  • CO2 savings: 2,600 tonnes per year
  • Investment sum: € 3 million
  • The project is supported with funds from the environmental promotion programme of the Ministry for Climate Protection.

Click here for the Wien Energie press release.

(c) Wien Energie/Max Kropitz

In the picture from left to right: Edmund Friedl (Managing Director Therme Wien), Joachim Kelz (Project Manager Research Project at AEE INTEC), Theresia Vogl (Managing Director Climate and Energy Fund), Theodor Zillner (Head of Department Energy and Environmental Technologies BMK), Peter Hanke (City Councillor), Michael Strebl (Chairman of Wien Energie Management).