Thermal Energy Storage - TES -

The Thermal Energy Storage group researches heat and cold storage based on phase change materials (PCMs) and sorption materials. Their research approach ranges from the development and optimisation of individual materials and components to the integration of thermal energy storages into complex energy systems. Storage materials and units for heating/cooling systems, for efficient household appliances, for industrial waste heat utilisation, and for automotive applications are being investigated.

The main work focuses are:

  • Development of highly performing, efficient, and cost-effective heat and cold storages
  • Construction of storage components, design, construction, and monitoring of demonstration setups and solutions for system integration
  • Measurement, modelling, and development of PCMs
  • Characterisation and modelling of sorption materials for open systems (at atmospheric pressure) to be used in heat storages and heat pumps as well as air dehumidification
  • Research on fundamental issues, e.g. the theoretical limits of storage capacity or the cycling stability of storage materials
  • Simulation of fixed beds and mass transfer surfaces for solid and liquid sorbents

Head of Group:
Dr. Stefan Hiebler
Walther-Meißner-Str. 6
85748 Garching
Tel.: +49 89 329442-35
Fax: +49 89 329442-12

Deputy Head of Group:
Dipl.-Phys. Christoph Rathgeber
Walther-Meißner-Str. 6
85748 Garching
Tel.: +49 89 329442-88
Fax: +49 89 329442-12

Services & Equipment


  • Calorimetric determination of the heat storage capacity of PCMs for temperatures ranging from 80 to 1,500 °C
  • Investigation of the thermal cycling stability of PCMs for temperatures ranging from 40 to 200 °C
  • Measurement of latent heat storage systems and heat exchangers for such
  • Investigation of crystal structures and determination of crystallisation rates
  • Determination of the water adsorption capacity of solid sorbents for temperatures ranging from 20 to 350 °C at -15 to 80 °C dew point temperature
  • Determination of temperature and dew point breakthrough curves for fixed beds of solid sorbents
  • Investigation of thermal and hydrothermal cycling stability of solid sorbents


  • Calorimetry: DSC, STA, Calvet and T-History calorimeters
    • Temperature range from -80 to 1,500 °C
    • Sample sizes from about 5 mg to 30 g
    • Measurements according to the guidelines of RAL-PCM Guetegemeinschaft PCM e. V.
  • Cycling apparatus for solid-liquid PCM
    • Temperature range from -40 to 200 °C
    • Sample size of about 60 ml
    • 2 to 3 thermal cycles per day
  • Testing rigs for characterisation of heat exchangers and latent heat storages
    • Temperature range from -10 to 95 °C
    • Volume flow up to 3 m3/h
    • Thermal power up to 25 kW heating/cooling
  • Polarisation microscope
    • Programmable heating and cooling stage for measurements from -190 to 400 °C
  • Microbalance for determination of the water absorption capacity of solid sorbents
    • Temperature range from 20 to 350 °C with -15 to 80 °C dew point temperature
    • Sample size: several grams
  • Self-developed testing rigs for determination of the water absorption capacity of solid sorbents
    • Dew point temperatures from 5 to 70 °C
    • Ambient air temperature up to 300 °C
    • Sample size in kilogram range
  • Testing rig for mass transfer surfaces for liquid sorbents
  • Cycling apparatus for solid sorbents
    • Dew point temperatures from 5 to 70 °C
    • Ambient air temperature up to 300 °C
    • Sample size of several hundred grams
    • Adaptations to real process conditions possible


coCO2vac – Development of Cold Storage Materials for the Dry-Ice-Free Transport of Vaccines


Current COVID-19 vaccines require a storage temperature of about -70 to -60 °C. Since the vaccines need to be distributed worldwide in large quantities, maintaining these temperature limits is a logistical challenge. Temperature control using dry ice is questionable from a safety and environmental perspective and heavily regulated, not only in cargo aircraft. Special transport containers equipped with cold storage materials (phase change materials, PCM) may be used to ensure an uninterrupted and energy-efficient cold chain. In the coCO2vac project, va-Q-tec AG and ZAE Bayern are to develop PCMs for the temperature range between -70 and -60 °C. The project includes the evaluation of potential PCMs on a laboratory scale, application-oriented testing of the materials in cold packs, and the transfer of the results to production scales. The project is to facilitate the dry-ice-free and energy-efficient temperature control of potential vaccines against COVID-19 and other pharmaceuticals with similar temperature requirements during transport and storage.

Head of Project: Stefan Hiebler,
Project Duration: 12/2020–12/2021

MINAKRIP – Nucleation and Crystallisation in Microencapsulated and Nanoemulsified PCM

Simulation: Organische PCM

One of the fundamental issues preventing the wider use of latent heat storages using phase change materials (PCM) is the effect of supercooling. Supercooling means that materials may be brought below their melting temperature without crystallising. The MINAKRIP project aims to investigate and systematise heterogeneous nucleation caused by nucleation agents in PCM. This way, the nucleation of microencapsulated and emulsified PCM is to be improved, and the applicability of these systems when using different organic PCM is to be increased. The research methods used are based on visual assessment using a transmitted polarised light microscope as well as molecular dynamics simulations on the atomic level.

Head of Project: Stefanie Tafelmeier,
Project Duration: 10/2018–09/2022

AMThES – Application-Oriented Characterisation of Materials for Thermochemical Energy Storages


Currently, the research and development of materials for innovative thermal energy storages is often carried out without regard to the actual requirements of applications. Yet, thermochemical energy storage systems are particularly dependent on the operating conditions specified by their respective application. Under application conditions, the energy storage density of thermochemical storage materials is often significantly lower than the value calculated from equilibrium measurements. Thus, it makes sense to test materials under actual application conditions early on. The AMThES project aims to identify suitable sorption processes for relevant thermal energy storage applications in the building and industrial sectors. Suitable meaning in this context, that the storage material meets the technical requirements of the application - storage capacity, charging and discharging performance, and stability - over the expected number of cycles while at the same time allowing economic use. Moreover, ZAE Bayern is to lead an International Energy Agency (IEA) working group in the field of Energy Storage ES, which focuses on new storage materials for thermochemical and latent heat storage systems.

Heads of Project:
Christoph Rathgeber,
Andreas Krönauer,
Project Duration: 01/2021–12/2024

ZAE Bayern

We conduct applied research at the interface between basic science and industrial application. Our methods and systems aim to achieve CO2 neutrality and thereby counteract climate change through the intelligent and efficient use of renewable energies.

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