Solar Info Center SIC in Freiburg, Germany

Description of the application

The Solar Info Center at Freiburg hosts companies, active in solar energy business. A part of the building is rent to Fraunhofer ISE. Within this part, an area of offices and a seminar room is air-conditioned by a liquid dessicant cooling system, driven in a solar thermal autonomous cooling mode. It is a pilot system to demonstrate the applicability of this technology.

General description of the system

The system technology is an open cycle liquid desiccant evaporative cooling system, using solar thermal heat for regeneration of the diluted LiCl solution. Solar thermal heat is provided by a flat-plate collector. The sorption process is cooled, thus increasing the sorption efficiency. An advantage of the system is the storage of diluted and concentrated solution in separate storages, which allows a decoupling in time between the dehumidification and regeneration process to a certain degree. No back-up heating systems for the regeneration of the solution is applied. During winter, heat from the district heat network from the University hospital is applied for supply air heating.

Central air-conditioning unit


open cycle (DEC)

Nominal air volume flow rate

1,500 m3/h

Minimum air volume flow rate

600 m3/h

Desiccant cooling system type

liquid desiccant

Desiccant type

Lithium Chloride

Cooling capacity

10 kW

Brand of desiccant unit


Solar thermal

Collector type


Brand of collector

Ufe Ecostar

Collector area

16.8 m2 aperture

Tilt angle, orientation

30 , south

Collector fluid


Typical operation temperature

5570 C regeneration temperature


Heat storage

1.5 m3

Cold storage

solution storages

Auxiliary heating support

district heating network

Use of auxiliary heating system

supply air heating in winter

Auxiliary chiller


System performance

Considering the overall cold production of the air handling unit (all operation modes: desiccant cooling, free cooling, adiabatic cooling) with relation to the total regeneration heat input, an average coefficient of performance (COP) of 1.0 was achieved. The specific annual collector yield was approx. 270 kWh/ma.

System reliability and overall success of the installation

Many improvements in the system control were applied within the first year of operation, mainly adressing an optimised operation of pumps and fans. In between, the system operation is reliable and promising and the availability of the system is very high. A transfer of the solution into the supply air has never occurred.

General information

Type of building  Seminar room and office area within the SIC
Location  Freiburg, Germany (48 North, 750 East)
In operation since  2004
System operated by  Fraunhofer ISE
Air-conditioned area  300 m2


Collector area

DEC unit
Collector area
Cooled area
DEC unit
Building view
Cooled area

Clicking an image opens the gallery view.

Specific information

Further specific information about the system are included in the filled in technical questionnaire.



For more information on the project please feel free to contact:

Edo Wiemken