Information for Researchers, No. 46 | June 17, 2022

Priority Programme “Carnot Batteries: Inverse Design from Markets to Molecules” (SPP 2403)

In March 2022, the Senate of the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) established the Priority Programme “Carnot Batteries: Inverse Design from Markets to Molecules” (SPP 2403). The programme is designed to run for six years. The present call invites proposals for the first three-year funding period.

The affordable, site-independent and resource-saving storage of electrical energy in the societally relevant order of magnitude of gigawatt hours (GWh) is the central unsolved problem in the transition to fluctuating renewable energy sources. One possible solution could be represented by the Carnot battery-technology, whereby electrical energy is converted into heat by means of high-temperature heat pumps, heat being stored in cheap materials as internal energy and then converted back into electrical energy when required, e.g. by means of steam turbines. The underlying thermodynamic principle has been known for a long time, however, there are still no general methods for designing or analysing Carnot batteries based on their fundamentals and objectives. Carnot batteries are complex, coupled, time-varying systems with a large number of components and degrees of freedom. Published efficiencies and costs are poorly verified or apply only to specific systems; the integration into future energy markets is unexplored.

The intrinsically new approach proposed by the SPP is a comprehensive inverse top-down design methodology, starting from the target variables (market) all the way down to the individual components (machines, storages and fluids, i.e. molecules) and their coupling, aiming at their optimal design and operation. This approach sets a completely new course with respect to today’s design methodology, which – based on known components and circuits – seeks to determine target operation parameters, e.g. efficiencies, and implements the optimal case identified in a very limited parameter space.

The working hypothesis of the Priority Programme is: “Through a paradigm shift towards an inverse design methodology, it is possible for the first time to test the feasibility of storage efficiencies above 70% and market-compliant storage costs using thermodynamic principles and to assess their compatibility with energy markets”. This hypothesis is to be assessed by an interdisciplinary team representing the fields of energy system analysis, thermodynamics, heat transfer, fluid energy machines, numerical optimisation and physical chemistry in close cooperation between universities and research centres (DLR).

This is to be done in the inversely arranged Subject Areas:

  • A – Carnot batteries in energy markets,
  • B – Design of Carnot batteries and
  • C – Components for Carnot batteries.

The work of the SPP will be systematised and validated in a shared Carnot battery laboratory.

Project proposals are expected in these areas, which show a close connection with at least one of the projects of the other research areas in order to establish an inverse and transferable top-down design methodology with quality and assessment criteria defined by the energy system analysis.

Subject Area A investigates and specifies quality criteria with inverse energy system modelling methods as well as their combination and robustness with respect to future demand under varying market conditions. Such criteria may include, among others, overall efficiencies, storage periods, costs or robustness under partial load or fluctuations.

In Subject Area B, the thermodynamic and thermo-economic inverse design of Carnot battery concepts will be pursued, which can fulfil the combinations of quality criteria selected in Area A, and in doing so, also uncover the need for new research in Area C with respect to the most relevant properties of the components. In Area B, either entire Carnot batteries or coupled sub-processes (heat pump with storage, heat engine with storage) are investigated theoretically or experimentally as a function of components and fluids taken as variables. In addition to considering actual working fluids, approaches adopting optimal fluids or fluids defined abstractly by model parameters are desirable.

In Subject Area C, fluids, storages, heat exchangers and fluid energy machines are investigated according to the specifications of the criteria and required properties derived in Area B. Component models as well as new methods of analysis and design are developed, which, in addition to good predictive power, also allow their implementation in optimisation procedures employed in Area B.

The temperature range of the reservoirs shall be below 500° C and working fluids, reservoirs, heat exchangers and machines shall be investigated generally as variables (and not as prescribed input) of the system analysis, configuration and optimisation.

Both theoretical and experimental studies should address fundamentals with sufficient depth and, at the same time, ensure the possibility of generalisation; the expected results of the projects should have the potential for enabling upscaling to industrial applications. Furthermore, the models developed during the first phase should provide the basis for a time-dependent analysis and control of the Carnot battery in the second funding period at the latest.

Possible topics are defined by the following keywords, where a focus on the Carnot battery (CB) and the inverse design methodology is compulsory:

  • Inverse energy system optimisation with the required CB parameter combinations as model outputs
  • Size dependence, partial-load behaviour and fluctuations
  • Fluid-tailored storage concepts
  • Flexible fluid energy machines and their behaviour as a function of fluid, load range and pressure ratio
  • Thermoeconomic analyses and scalability
  • Thermal storage concepts, materials and configurations
  • Modelling, optimisation and experimental validation
  • Carnot battery concepts configurations and modes of operation
  • Fluid properties of pure substances and zeotropic mixtures with low GWP (thermodynamic and transport properties)
  • Heat exchanger concepts and properties under variable load conditions

The following topics are not subject of research in the SPP:

  • Processes using ideal gases and pure water
  • Thermo-chemical energy storage or adsorption/absorption storage
  • Synthesis of new fluids or storage materials
  • Classical energy system optimisation with extensive parameter variation
  • Use of additional energy sources (e.g. waste heat)

Interested applicants are invited to submit a short outline in German or English of no more than two pages to by 10 August 2022 providing information on a) own expertise, b) a preliminary project idea and c) the required or desired competencies of possible partners from the other subject areas. The applicants will be invited to attend a coordination meeting in Duisburg on 21 September 2022, during which they will be able to exchange ideas, also supported by a poster session, and get to know scientists from the other research areas, with the possibility of discussing potential collaborations.

Full proposals must be written in English and submitted to the DFG by 17 January 2023. Please note that proposals can only be submitted via elan, the DFG’s electronic proposal processing system. To enter a new project within the existing Priority Programme, go to Proposal Submission – New Project/Draft Proposal – Priority Programmes and select “SPP 2403” from the current list of calls.

In preparing your proposal, please review the programme guidelines (form 50.05, section B) and follow the proposal preparation instructions (form 54.01). These forms can either be downloaded from our website or accessed through the elan portal.

Applicants must be registered in elan prior to submitting a proposal to the DFG. If you have not yet registered, please make sure you do so by 10 January 2023, in order to be able to submit a proposal under this call. Registration requests received after this date cannot be considered. You will normally receive confirmation of your registration by the next working day. Note that you will be asked to select the appropriate Priority Programme call during the proposal submission process.

The reviewing process will include a colloquium with presentations and discussions between applicants and reviewers, scheduled to take place in March/April 2023.

Further Information

More information on the Priority Programme is available under:

The elan system can be accessed at:

DFG forms 50.05 and 54.01 can be downloaded at:

For scientific enquiries please contact the Priority Programme coordinator:

  • Professor Dr. Burak Atakan
    Universität Duisburg-Essen
    Institut für Verbrennung und Gasdynamik
    Lehrstuhl für Thermodynamik
    Lotharstraße 1
    47057 Duisburg
    phone +49 203 379-3355

Questions on the DFG proposal process can be directed to:

Programme contact:

Administrative contact: