Joule and Brayton process-based Carnot batteries for flexible power, heat and cooling generation.

In the predecessor project CH-Flex, Brayton batteries with high operational flexibility were developed to couple the "electricity" and "thermal energy" (heating and cooling) sectors in order to achieve high annual utilisation rates in the combined generation of electricity and heating/cooling and thus increase the economic prospects of this Carnot battery technology. In the end, seven lead concepts were selected from a broad-based concept study, which have the potential to supply heat and cooling at the same point in the process scheme with a time delay. These lead concepts were mapped in more detail in quasi-stationary system simulations and analysed in more detail.

Previous studies and developments on Brayton process-based Carnot batteries have so far been limited to (quasi-)stationary considerations in order to determine the overall energy performance and describe the sizes and technologies of the components. The central challenge is now to map the dynamic properties of selected configurations and their thermal components. This allows operational requirements for start times and load changes to be further developed in a targeted manner and harmonised with the requirements of the target markets.

With the successful completion of the planned work on a Brayton battery adapted to operational requirements for large-scale applications on the electricity-heat sector boundary, significant steps will be taken towards new technology options for the energy transition.


For pre-selected concepts, existing generic dynamic models are adapted or extended for the thermal components, such as heat accumulators and heat exchangers, so that they describe the transient behaviour of the specific components under changing conditions, such as start-up, shut-down and change of operating states. At the end of this first step, the thermal components are characterised dynamically with the help of the transient models created. Suitable methods from control engineering are used for this. The transient behaviour of the non-thermal components, such as turbomachinery, is mapped in a simplified manner using suitable assumptions.

Dynamic models of the overall systems are created from the component models, with the help of which previously defined parameter variations are carried out with regard to dynamic properties. The results are then compared with the requirements of the target markets and the best concepts are defined as lead concepts for further development in future projects and plans.

The requirements for the dynamics of the non-thermal components, which contain these guiding concepts and whose transient behaviour has not been adequately represented here by dynamic models, are compiled.

Joule-Flex at a glance



1.1.2024 - 31.12.2025


German Aerospace Center (DLR)

Federal Ministry for Economic Affairs and Climate Action (BMWK)

Project partners

Institute of Combustion Technology (DLR-VT)