Heat Conversion - HCV -

The Heat Conversion group researches and further develops the field of heat conversion via chillers and heat pumps. Its range of research extends from the development and optimisation of individual components to their integration into complex energy systems. Many years of expertise have accumulated in the group, particularly on sorption heat pump and cooling systems (closed absorption, open adsorption), sorption storage systems, and innovative compression refrigeration applications.

The main work focuses are:

  • Research on thermal fluid dynamics, heat transfer, and fluid process engineering
  • Heat pump cycle design, optimised circuits, methods for increasing efficiency
  • Design, construction, and testing of thermally or electrically driven chillers and heat pumps
  • Identification of promising applications for innovative heat pump solutions and adaptation or adapted development of such
  • Planning and integration of innovative heat pump solutions into complex energy systems, including operational support and optimisation
  • Design of plants and energy systems for cooling and heating in the fields of trigeneration, solar air conditioning, waste heat utilisation, cooling with biomass, and cooling with district heat

Head of Group:
Manuel Riepl, M.Sc
Walther-Meißner-Str. 6
85748 Garching
Tel.: +49 89 329442-43
Fax: +49 89 329442-12

Deputy Head of Group:
Andreas Krönauer, M.Eng.
Walther-Meißner-Str. 6
85748 Garching
Tel.: +49 89 329442-13
Fax: +49 89 329442-12

Services & Equipment


  • Modelling and simulation of thermodynamic cycle processes
  • Basic process engineering of components, systems, and plants as well as their practical implementation
  • Basic theoretical and experimental investigations, all focused on application
  • Identification of promising applications for innovative heat transformation methods and their implementation
  • Highly developed prototyping
  • Energy system analysis, source-sink analysis, integrability of storages and heat pumps for waste heat utilisation
  • Planning support and metrological monitoring for demonstration projects
  • Economic feasibility studies


  • Thermal analysis laboratory for static and/or dynamic measurement of heat pumps and chillers up to approx. 200 kWth (hardware in the loop)
  • Vacuum testing systems for measuring components under sub-atmospheric conditions
  • Test setup for determination of vapour-liquid equilibria of aqueous solutions
  • Leakage testing of vacuum systems or high vacuum systems (helium leakage testing system)
  • System for corrosion testing in aqueous salt solution environments
  • Comprehensive software models for static and dynamic modelling of sorption and compression heat pumps at component and system level


BioWap – Biomass-Driven Absorption Heat Pump and Chiller System

ZAE Bayern KopernikusPower2X Projekt

In the BioWap project, a functional model of a highly efficient absorption heat pump system fired directly with wood pellets at a heating capacity of about 90 kWth and a cooling capacity of up to 75 kWth was developed. The system efficiency is expected to reach up to 200 %.

The direct coupling of combustion and an absorption heat pump (working media: water and aqueous solution of lithium bromide) renders a low-temperature heat source usable. To keep the cost of planning and installation as low as possible, an integral hydraulic and control module was developed as well.

The project's core objective was to develop and illustrate a functional model of an absorption heat pump directly fired with wood pellets at a heating capacity of around 90 kWth (firing capacity around 50 kWth). This aimed to open up a new technological path for providing highly efficient low-emission heat. HDG Bavaria GmbH acted as the joint partner.

Head of Project: Manuel Kausche, M.Sc., manuel.kausche@zae-bayern.de
Project Duration: 09/2016–08/2020


GALuWap - Gas-Fired Air-Source Absorption Heat Pump with Optimised Heat Exchanger Geometries

ZAE Bayern-open_BEA Projekt -  Graphik

In project GALuWap, a compact, (bio)gas-fired absorption heat pump system for a maximum heating capacity of 50 kW is being developed. It uses outside air as a heat source and an environmentally neutral combination of water and an aqueous lithium bromide solution as a working medium.

Multi-stage absorption heat pumps can generate temperature lifts of up to 70 K, even using fairly cold outside air at a minimum temperature of -10 °C. They are therefore suitable to heat existing buildings and provide domestic hot water at up to 60 °C.

Thus, the typical demand for heat and domestic hot water in Germany can be almost completely covered through a heat pump. The seasonal thermal efficiency of the system reaches up to 1.3. So compared to gas condensing boilers, up to 25 % of the primary energy consumption may be cut. If cooling and heating are provided simultaneously, e.g. in mixed residential and commercial buildings, seasonal efficiency may increase to 1.6. Compared to a gas condensing boiler with compression chiller, this represents a reduction in consumption of up to 40 %.

To reduce cost and volume, plate heat exchangers developed in an earlier project are being examined to see if they can replace the shell-and-tube heat exchangers commonly used in heat pumps. Also, an integral hydraulic and control module is being developed to reduce the effort required for planning and installation. The greatest challenges lie in an operationally reliable implementation of the innovative cycle concept, including special precautions for operation below the freezing point of the water in use, as well as in the implementation of the gas-fired expulsion system.

Head of Project: Manuel Kausche, manuel.kausche@zae-bayern.de
Project Duration: 12/2019–11/2022

KIG - Highly Efficient Trigeneration for Industry and Commerce, Phase I: Development

ZAE Bayern ELVABATTslim - Apparatur Aufbau

Development of a highly efficient and economical trigeneration system for smaller outputs (approx. 20 kWel ) with highly efficient direct utilisation of the CHP's exhaust gas heat (450 °C) to drive a multi-stage absorption chiller and thus achieve a 25 % higher cooling yield than conventional cogeneration systems. The pre-assembled system with matched components cuts investment costs, making it economically attractive.

In the project, the integrated system is being designed and set up for extensive practical testing at the Kompetenzzentrum KWK in Amberg. At the component level, this involves the refinement of a high-temperature desorber with vertical boiling tubes, the development of a compact unit design for highly automated production, and matched components (CHP, multi-stage absorption chiller, hydraulics) as well as higher-level controls for the CHP system which interface with the building management system.

Head of Project: Christian Wuschig, christian.wuschig@zae-bayern.de
Project Duration: 03/2017–05/2021

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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