Storage system technologies capable of both storing and releasing electricity and heat hold great potential for the future renewable energy system. The TESSERACT1 project is developing engineering approaches to underground high-temperature storage (UHTS) based on Carnot battery technology.
A Carnot battery is an energy storage system that stores electricity in the form of thermal energy. During the charging process, surplus electricity generated is converted into heat and temporarily stored in a thermal storage system. During discharge, the stored heat is converted back into electricity and/or the waste heat is utilised. The core component of Carnot batteries is the storage system. Various technologies, such as steel containers with gravel packed beds, fluidised beds or PCM high-temperature storage systems, have already been demonstrated in recent years. These above-ground engineering approaches are, however, complex to construct, only scalable to a limited extent and difficult to integrate into natural and urban landscapes.
Subsurface high-temperature storage system
As part of the TESSERACT project, an interdisciplinary team led by AEE INTEC2 is developing engineering approaches to scalable underground high-temperature storage (UHTS) tailored to various geohydrological conditions and system integration requirements. For the first time, naturally grown soil is being used as the storage medium. This approach is intended to significantly accelerate construction, reduce costs and enable scalability. The subsurface engineering approaches are being designed and tested for temperature levels of up to 500 °C. This enables broad application in existing energy supply systems, such as in industry or the building sector. Another advantage of the planned UHTS is that the surface above the storage system can be used for multiple purposes, such as construction or development.
Research and demonstration
The research and demonstration phase, with construction of the storage system scheduled to begin in 2027/28, will mark the first time this innovative concept is comprehensively validated from a technical, economic and legal perspective. The project involves the development of innovative thermal insulation measures and methods for various structural components, specialised civil engineering construction techniques and novel ground heat exchanger solutions. In addition to the wide range of technical and physical criteria, the project also addresses economic and operational questions as well as legal and environmental aspects.
A concept with high potential
In the future, this new storage technology has the potential to enable a flexible and intelligent energy system wherever volatile renewable sources are used for electricity supply. The system is scalable in terms of storage volume and integration into existing grid infrastructures. It is especially well-suited for integration with district heating networks in urban areas, industrial and large-scale commercial sectors, as well as for energy communities. The concept therefore makes a significant contribution to the transition to 100% renewable energy sources.
1 Thermal Energy Storage as Sensible Energy Reservoir in ACtivated Terrain
2 Project partners: AEE INTEC (project management) Ste.p, PORR, Glapor, Windkraft Wolkersdorf (WW) and Biomasse Wolkersdorf (BMW), GeoSphere Austria