In future, a large proportion of energy in the energy system will come from fluctuating renewable sources. Energy storage systems will play a central role in facilitating the energy transition, as they can balance fluctuations between energy generation and consumption. High-performance electricity and heat storage systems ensure that energy from renewable sources such as wind, solar or geothermal energy is reliably available at all times. They make it possible to bridge gaps between supply and demand across hours, days and even seasonal timescales, significantly enhancing system stability, security and supply quality. Research and innovation strive to accelerate the development of these key technologies toward market readiness. In 2024, Austria’s total energy demand reached 287 terawatt hours (TWh), with nearly half of this consumed by the heating sector. To date, only about one third of the required heating energy is generated from renewable sources.1 As a result, heat storage is gaining increasing importance alongside electricity storage systems.
Thermal energy storage systems for a wide range of applications
Heat storage technologies can be classified according to the type of storage process and storage media (e.g., sensible heat accumulator, latent heat accumulator, thermochemical storage), as well as by size and application (ranging from short-term to seasonal energy storage systems). Compact heat storage systems such as buffer tanks or latent heat accumulators are used in both houses and apartment blocks, often coupled with heat pumps or solar installations. Large-scale heat storage systems are essential in the decarbonisation of district heating networks. In industry, heat accumulators offer the opportunity to utilise waste heat or temporarily store surplus electricity as heat, enabling the carbon-neutral delivery of process heat. Sector coupling also plays a key role in long-term energy storage systems. This involves linking different forms of energy supply, such as the electricity sector with the gas and heating sectors, through the conversion and storage of energy. Sector coupling technologies (power-to-heat, power-to-gas) enable the integration of renewable energy sources and increase flexibility within the energy system.
Research needs and demonstration
Research and development in the field of heat storage technologies aim to reduce investment costs, extend system lifespan, improve efficiency, achieve more compact designs and ensure a high level of system security. Key topics in current national and international research projects include the selection of suitable storage technologies, the development of new materials and components, the integration of storage systems into the energy system and methods for monitoring and operational optimisation. Demonstration plants are crucial to advancing development and facilitating market entry. In addition, appropriate legal frameworks and new business models must be developed.
In this issue, we present several pioneering Austrian projects on heat storage technologies and report on the involvement of Austrian experts in the International Energy Agency’s technology programmes on energy storage systems.
The demand for heat storage capacity in Europe is expected to grow significantly in the coming years. Projections estimate that Europe’s district heating demand will reach approximately 1,780 TWh by 2050 (EuroHeat and Power, 2018). Assuming that around 5 to 15 per cent of the annual heat demand needs to be stored temporarily, the necessary storage capacity amounts to approximately 90 to 270 TWh. This would require a total of 22,500 to 67,500 large-scale heat storage systems, each with a water-equivalent volume of 100,000 m³.2
1 positionen.wienenergie.at/grafiken/energieverbrauch-oesterreich
2 Source: Nachhaltige Technologien 1/2024, AEE INTEC, p. 6
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