Solar Thermal Energy

Solar cooling based on adsorption cooling technology

The project partners aim to install and analyse an innovative solar thermal cooling technology at the Universitätsklinikum Freiburg. This is to be based on adsorption cooling technology and the adsorption chiller is to be supplied with the required thermal power by a solar collector field.


As part of the project, an innovative, CFC-free technology for solar thermal cooling is to be installed and subjected to extensive measurements and analysis.

The project was begun by first installing an adsorption chiller with a nominal cooling output of 70 kW as well as additional system components in one of the Universitätsklinikum Freiburg's laboratory buildings. A major part of the chiller's thermal power was supplied by a 171-m² evacuated-tube collector field. An integrated monitoring system visualised all relevant data and saved it in a daily file. The measured data were to be examined in regard to various issues:

  • Evaluation of the components (solar collector, thermal storage, adsorption chiller)
  • valuation of the system as a whole (solar coupling, operation, control concepts, energy balances)
  • Development and validation of simulation programs

The data recorded provided the project partners with valuable information regarding optimisation of control concepts and operation of the adsorption chiller system.


  • The collectors produced 8,780 kWh in August 2002. With roughly 16,700 kWh of incident sunlight falling onto the 171-m² collector field, a net collector efficiency of more than 52% was achieved.
  • In August 2002, the adsorption chiller consumed a power of approximately 7,925 kWh. The evacuated-tube collectors thus produced a de-facto surplus of solar thermal energy.
  • Installation of a buffer store in the adsorption chiller's return feed on the hot-water side compensates temperature fluctuations that would otherwise occur in the system due to the adsorption chiller's cyclic operating principle. Heat transfer from the solar power system is stable.
  • Potential for optimisation remains given in respect to the input auxiliary electrical power, which displayed unexpectedly high annual values.

More Project Information

Project number: 0329796A2

Project period: 1997 - 2001

Project region: Germany (Baden-Württemberg)

Project contact:

Herr Dipl.-Ing. Glaser

Herr Dr. Henning
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Source: German National Library of Science and Technology Hannover (TIB)