Project meeting of STEP at the site of the company ATS - Agro Trading & Solutions in Hardegsen (Photo: DBFZ)

Biomass gasification Biomass furnace

Project ID 03KB056

HTBioStir - Development of a high temperature heat exchanger for coupling biomass boilers to Stirling engines

Stirling engine (Photo: CUTEC Institut GmbH)


  • 01.07.2011 – 31.12.2014


CUTEC Clausthaler Umwelttechnik Forschungszentrum
Leibnizstraße 23
38678 Clausthal-Zellerfeld

Dipl.-Ing. Werner Siemers – project manager
Telephone: +49 5323 933-240

Dipl.-Ing. Nadine Senkel


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Results only available in German.


The choice of technologies for the decentralised use of biomass for combined heat and power generation is still limited and the plants available are of limited reliability only. A technical alternative is available in the form of the Stirling engine, which is supplied with the required enthalpy by an external heat supply and not by an internal combustion process (as with reciprocating engines). The high system temperatures required for high degrees of electrical efficiency leave behind traces (soiling, tar, fused ash etc.) of the required thermal transport of a release of energy fed by biomass to the Stirling complex. Direct couplings have not been successful. An indirectly operating heat transmission system is therefore to be developed which is fed on the one hand by burning biomass in a boiler and which on the other hand transmits heat to the Stirling engine as a hot gas. This enables a lower grade of fuel to be used, optimises combustion and should enable the Stirling engine to operate for longer periods without technical problems.


In an initial step the possible heat transmission concepts are to be systematically re-appraised at a temperature range of 850°C to 1200°C and adapted to the actual task of coupling a Stirling engine to a biomass boiler. The knowledge gained in this process is then to be converted into a technical concept in the second phase and tested. If successful, this concept will provide a highly efficient conversion technology, low emissions and great potential for reducing climate gas emissions by the effective use of the renewable energy source, biomass. Biomass can then be used decentrally for combined heat and power generation.


  • Evaluation of the different heat transfer mechanisms such as regenerative, recuperative or heat pipe
  • Determination by measurements and models of the boundary conditions at the boiler and Stirling engine
  • Design and calculation of one or more heat exchangers
  • Manufacture of the heat exchanger, installation and test phase
  • Concluding economic and technical evaluation


  • Development of a high temperature heat exchanger for couplings biomass boilers to Stirling engines


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