Fraunhofer ISE, Freiburg, Germany

Solar air-conditioning with adsorption chiller of the canteen kitchen area at Fraunhofer ISE, Freiburg, Germany

Description of the application

The Fraunhofer Institute for Solar Energy Systems (ISE) institute building is an energy efficient building with passive cooling measures. An exception is the canteen kitchen area, where due to high internal loads active cooling of the supply air is appropriate. This is done by means of a small size thermally driven chiller.

General description of the system

The system technology is a closed cycle chilled water system with an adsorption chiller. Heat is provided by a solar thermal system and by the heat network of the institute. During summer, the system runs in cooling mode. The medium temperature heat of the chiller is rejected by three ground tubes of 80 m each. In winter, the heat pump function of the machine is activated and the ground tubes act as low-temperature energy source. The system thus cools and heats the supply air into the kitchen.

Central air-conditioning unit

Technology

closed cycle

Nominal capacity

5.5 kWcold

Type of closed system

Adsorption

Brand of chiller unit

SorTech ACS 05

Chilled water application

supply air cooling

Dehumidification

occasionally

Heat rejection system

dry, ground tubes

Solar thermal

Collector type

flat-plate

Brand of collector

Solvis FF 35s 3/2 FKY

Collector area

22 m2 aperture

Tilt angle, orientation

30, south

Collector fluid

water-glycol

Typical operation temperature

75 C driving temperature for chiller operation

Configuration

Heat storage

2 m3 water

Cold storage

none

Auxiliary heating support

Institute heat network, operated by CHP and gas boiler

Use of auxiliary heating system

Auxiliary driving source for chiller, auxiliary driving source for heat pump operation in winter

Auxiliary chiller

no

System performance

For one year of operation (August 2008 until July 2009) an average seasonal Coefficient of Performance of COP = 0.43 was observed. The solar thermal coverage of the total heat input for cooling and heating was 30%. The chiller was newly evacuated before the monitoring period. During winter, the machine runs in heat pump mode; the resulting COP in this operation mode for the whole heating season was 1.25.

System reliability and overall success of the installation

After a decrease in performance during the first operation months (inert gasses), the chiller was newly evacuated in August 2009. Apart from this, the operation was very reliable. The system concept is promising: no cooling tower is required, and a fraction of the rejected heat in summer in the borehole may be available in the low-temperature heat source during the heat pump operation mode in winter. Another advantage is the noiseless operation of the chiller.


General information

Fraunhofer ISE institute building. In the foreground: installation of ground tubes.
Fraunhofer ISE institute building. In the foreground: installation of ground tubes.

Type of building  kitchen area of Institute
Location  Freiburg, Germany
In operation since  2007
System operated by  Fraunhofer ISE
Air-conditioned area
  42 m2

Figures

22m2 of Solvis flat-plate collectors on the instute's rooftop
22m2 of Solvis flat-plate collectors on the instute's rooftop
SorTech ACS 05 chiller unit
SorTech ACS 05 chiller unit
Fraunhofer ISE institute building. In the foreground: installation of ground tubes.
Fraunhofer ISE institute building. In the foreground: installation of ground tubes.

Clicking an image opens the gallery view.


Specific information

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

DE04_FhG-ISE.pdf

Contact

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

Edo Wiemken
edo.wiemken(at)ise.fraunhofer.de