Within the framework of the International Energy Agency’s research collaboration, new technology developments for energy storage systems are being advanced at the international level. The IEA Solar Heating and Cooling Technology Collaboration Programme’s Task 67 project focused on innovative materials for compact thermal energy storage systems (CTES).1 Specialists in materials science, component design and system integration collaborated on this project to enhance compact thermal storage technologies and expedite their entry into the market. The project centred on the investigation and optimisation of phase change materials (PCMs) and thermochemical materials (TCMs), which form the foundation of these technologies. More than 80 experts from 16 countries participated in the work across five subtasks. AEE INTEC provided the overall leadership for the project. With the active involvement of numerous Austrian experts, significant progress was achieved across all work packages, laying the groundwork for the further development and future implementation of compact thermal storage systems.
Material characteristics and database
Led by the AIT Austrian Institute of Technology, several standardised measurement methods for CTES materials were developed and validated. In addition, the material and knowledge database was significantly expanded and systematically maintained.
Advancing compact storage system materials
This work focused on strategies to tailor the properties of CTES materials to improve their thermal storage characteristics and efficiency. Innovative work in the fields of material and component development was carried out at the Institute of Applied Synthetic Chemistry at TU Wien, leading to the discovery and characterisation of new compact storage system materials from the oxalate and Tutton salt families.
Determining the state of charge of compact heat storage systems
The objective was to develop techniques that can reliably and cost-effectively determine the state of charge of a CTES. The Austrian partners FHOÖ and AEE INTEC developed and tested various methods for determining the state of charge of a sorption storage system within the SorSens2 project. For all types of energy storage systems, the current state of charge (SoC) is a key parameter for efficient operation and management. Unlike sensible heat accumulators, the state of charge in a thermochemical heat storage system cannot be assessed by measuring the discharge temperature. The moisture content of the material and its distribution throughout the entire storage system serve as a more reliable indicator of the state of charge. Within the project, 26 measurement methods for accurately determining the state of charge in PCM or TCM systems were gathered and classified, and four prototypes demonstrating direct interaction between the material and the control system were presented and reviewed.
1 nachhaltigwirtschaften.at/en/iea/technologyprogrammes/shc/iea-shc-task-67.php
The project was conducted as a joint, collaborative task under the two Technology Collaboration Programmes (TCPs) for Solar Heating and Cooling and Energy Storage (see interview).
2 SorSens – Development of a virtual sensor for state-of-charge evaluation of TCM energy storage
