The project aim is to develop thermal energy storage using phase change materials for process heat systems. Phase change materials (PCM) store large amounts of energy in the liquid-solid phase change process. This offers many advantages when a low temperature difference between charging and discharging the storage is given over several hours. In contrast to water storage, PCM storage can be operated with low pressure for T > 100 °C. Because there is only a limited selection of PCMs for temperatures between 100 and 220°C, new types of PCM for this temperature range are being developed in this project. To charge and discharge PCM with high efficiency, a new heat transfer concept is being developed.
In order to define the storage system requirements, solar-driven and conventional systems were analyzed to determine their suitability for PCMs. System simulations were used to develop an optimized operating concept for PCM storage in selected process heat systems. New types of PCMs in the form of sugar alcohols, long-chain paraffin and alcohols, amide as well as polymers are investigated or synthesized. In order to make suitable storage materials, these materials are modified to improve their thermal properties. In comparison to other PCMs, they demonstrate higher storage densities. At the same time, a plate heat exchanger concept is under development for charging and discharging the PCM in the storage tank. Finally, a storage system for demonstration purposes will be developed based on the findings and subsequently characterized at a storage test stand.
Simulations on the storage concept will accompany this work. Models for the heat exchanger and the storage will be developed and subsequently validated with measurement data. Simulations are used to optimize the position of the plates and the hydraulic connections with respect to the PCM’s thermal performance.
Fraunhofer ISE focuses its research on the development of the PCMs and the heat exchanger. Their work involves material and component characterization, simulation model development as well as simulation analyses on both the component and systems level.