District heating systems fully based on renewable energies require very large storages that allow seasonal storage of large amounts of renewable heat or waste heat respectively. Additionally these large storages are able to raise flexibility of the district heating networks.
Compared to currently installed heat storages the storage volume has to be increased tenfold and at the same time it is necessary to place the required huge volume subsurface. This is quite challenging in respect of materials and construction of these giga-scale storages.
The Austrian lead project giga_TES aims at developing giga-scale storage concepts for urban districts with integrating large shares of renewables focusing on Austrian implementations.
Photo Credit: Arcon-Sunmark
Three Austrian sites will be investigated in respect of the main challenges like construction, geology and geophysics, materials, district heating system and its operating characteristics, economic aspects, public acceptance etc.. The three sites will be used as demonstration systems throughout the project.
To reach 100% renewable energy supply in the long term large-scale thermal storages like pit storages or large tank storages are necessary for district heating systems. As the systems are going to be installed in urban areas the required surface should be minimized because of relatively high land costs in cities. Through installing the storages subsurface it is possible to use the surface for recreation or installation of solar collector fields and therefore minimizing of costs is reached. District heating systems require thermal energy storage volumes from 50 000 m³ to 1 M m3 corresponding to 1 bn. litres. Currently large thermal energy storages are run in Germany and mainly in Denmark, storage volumes installed lately reaching nearly 200 000 m³.
Because of the low number and the few years existing large-scale thermal storages have been in operation so far experiences with these storages for district heating systems are still limited. Improvements especially in respect to performance and durability are necessary. Cost efficiency and system integration require higher storage densities and therefore higher temperatures leading to even higher requirements in respect to the applied materials. Vapour tightness, serviceability and durability of innovative solutions for cover, walls and liners require novel materials and components as well as improved test methods. Additionally innovative construction methods are needed because of the targeted storage size and its subsurface construction. Therefore the project is structured according to the following R&D areas: Development of Components and Technologies, Materials Development and Testing, Computer Aided Storage Optimisation, System Integration and Storage Management