The heat store is specially designed for the use of high-temperature waste heat T > 1,000°C. It can be retrieved from the heat accumulator at a later time as needed for production processes or used for downstream processes, such as waste heat utilization by conventional steam power processes or Organic Rankine Cycle (ORC) technology for electricity generation. This increases the efficiency and cost-effectiveness of existing and new processes in manufacturing companies. Several individual modules with different storage materials can be combined in the heat storage system. This makes it possible to route the waste heat flows occurring at different temperature levels to the appropriate module and store them at temperatures that are adapted in each case and as high as possible.
The high-temperature module with its ceramic accumulator made of honeycomb bodies or molded bricks stores high-temperature heat between 400 and 1,400 °C. In the medium-temperature module, a phase change material (PCM) enables heat to be stored at a level up to around 400 °C with a simultaneous low temperature change. In the lower temperature range, a stone/concrete accumulator is used to store heat at temperatures between 200 and 600 °C.
Optimization through intelligent control
An intelligent control system for the thermal processes developed in the project in combination with the modular storage unit absorbs the frequently fluctuating temperatures and outputs of thermal process plants by adjusting itself fully automatically to the processes. It incorporates the specific characteristics and advantages (charging/discharging characteristics, temperature stability, costs, etc.) and includes an interconnection concept for coupling the individual modules and integrating the storage unit into existing and new processes. The control system of the modular heat storage unit is particularly suitable for the short-term storage of waste heat from operating fluctuations and disturbances of 30 seconds to 15 minutes. The intelligent process control developed for these high requirements can also be transferred to long-term storage for longer periods of up to 48 hours. A calculation tool for the exact design of the modular heat storage system and optimization procedures for dimensioning and operation complement the development.
The project partners in the ModulHeatStore project were OWI Science for Fuels gGmbH, the Dresden branch of the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, Hülsenbusch Apparatebau GmbH & Co. KG and the Gesellschaft für industrielle Wärme, Energie- und Prozeßtechnik mbH.