At the radiological practice Dr. Reichel & Dr. Gehrmann, a solar assisted cooling system in order to remove mainly the loads from the tomography equipment of the practice went recently into operation in July 2008. The practice is located in the Rheineck-building, a landmarked and refurbished building, used by several commercial companies (figure 6). A central chilled water network, operated by an electrically driven compression chiller, distributes chilled water to the enterprises in the building. Cooling demand in the radiological practice occures day and night and throughout the year, since the supra-conductive solenoid has to be cooled continuousely. With the installation of the additional solar cooling system, cold consumption from the chilled water network is reduced during the day.

Absorption chiller

10 kW

The solar cooling system consists of 40 m2 vacuum tube collectors of the company Phonix Sonnen — warme AG, and of the high efficient suninverse absorption chiller from Sonnenklima, Berlin, with 10 kW rated chilling capacity. In this application, the collector fluid is pure water as well. The chiller is combined with dry heat rejection with water spray option in case of high ambient temperatures. During winter, the heat rejection system will be used for free cooling at sufficient low ambient tempe­ratures in order to contribute to the cooling load coverage. Due to the limited installation area, the whole plant is a roof-top installation. The monitoring system is going to be installed and operated by the Technical University Chemnitz. A scheme of the system is shown in figure 7.

As a consequence of the continuous cooling demand of the practice throughout the year and due to the limited size of the plant, the coverage of the cooling load by the solar thermally driven system will be quite small; simulation calculations have revealed primary energy savings in the order of 15% annually

with some uncertainty, since by the time of the calculations the final type of the tomographic equipment was not known precisely. Nevertheless, the concept is promising in order to demonstrate the general applicability of process cooling with a high efficient absorption chiller and dry cooling as well as with free cooling via the hybrid re-cooling system.