The first phase of the hybrid storage facility at the EVN site in Theiß was officially opened in May 2025. With this, the energy provider is taking the next step in transforming the conventional power plant into a future-ready energy hub. The new storage system is a key technology for the energy transition. Surplus green electricity can be stored here temporarily and used at a later time. This makes the energy supply more secure and independent.
For several years now, the EVN power plant in Theiß, located in the Krems district, has been gradually transforming into a sustainable energy hub. The gas-fired power plant is now used solely for grid support. Since autumn 2023, a new biomass facility has been in operation, supplying Krems with natural heat and green electricity. And since 2024, 5,700 solar panels have been generating solar power. The next step towards a full transition to renewable energy is the deployment of an innovative hybrid energy storage system.
Interaction of energy systems
Several years ago, a 5 MW power-to-heat system was installed at this EVN site, using surplus electricity to generate heat. The heat produced can be temporarily stored in the Theiß district heat accumulator if it is not needed immediately. This giga-scale thermal storage system is the largest district heat accumulator in Austria, a specially insulated former oil tank with a capacity of 50,000 m³ of hot water. The existing power-to-heat system, which is connected to the giga-scale thermal storage system, has now been expanded with a battery storage unit featuring a power output of 5 MW and a capacity of 6 MWh. The hybrid system integrates storage systems supplied by diverse energy carriers and, together with the biomass cogeneration plant and the newly installed photovoltaic system, establishes a seamless interface between the different energy systems. The combination of battery and thermal storage systems greatly enhances flexibility. When there is surplus energy in the power grid, the electric heating system is activated; when demand exceeds generation, energy can be drawn from the battery storage unit. The hybrid storage system balances the fluctuating output from renewable energy sources, ensuring security and stability in the grid. At the same time, green electricity can be converted intelligently into heat energy with an efficiency close to 100%. The battery storage system installed in the spring consists of a total of five containers and is just the beginning. In the next phase, EVN plans to significantly expand the system by installing a battery storage system with a power output of up to 70 MW and a capacity of at least 140 MWh.
AI-based control systems
To develop a comprehensive understanding of hybrid storage systems from technical, scientific and regulatory perspectives, the planning and implementation of the hybrid storage system were scientifically supported by the SEKHOS1 research project (Theiß sector-coupling hybrid storage system). One of the objectives was to develop business models for marketing the flexibility that can be ex- changed between different energy carriers. As part of the research project, artificial intelligence was employed to optimise the control of heat and electricity flows at the Theiß power plant. Machine learning is used to generate forecasts for heat demand and solar power generation. For solar power forecasts, EVN draws on weather data as well as generation data from its other photovoltaic systems. The integration and processing of extensive data form the foundation for evaluating and optimising the operation of the hybrid storage system. The measurement systems will remain in place beyond the conclusion of the research project, continuously providing data for further analysis and use.
„Research and development are indispensable for driving innovation in the energy sector. New solutions developed in the lab are first tested and refined on a small scale. They are only rolled out on a large scale and integrated into the energy system once they’ve passed thorough testing. By progressing through multiple stages, this innovation process delivers continuous improvements, while safeguarding the reliability and security of our energy supply. The Green Energy Lab research initiative plays a crucial role by allowing us to test new solutions in real-world operating conditions.“
Andrea Edelmann
Head of innovation, sustainability and environmental protection, EVN Group
greenenergylab.at/projects/sekohs-theiss-demo
1 Project partners: TU Wien/ Energy Economics Group (EEG) (project management), AIT Austrian Institute of Technology GmbH, EVN AG, EVN Wärmekraftwerke GmbH
The SEKHOS THEISS project is part of the Green Energy Lab innovation network. greenenergylab.at
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