In 2001, the new energy efficient buildings of the Technology Center of FESTO AG in Berk- heim/Esslingen were completed. The area comprises 26,000 m2 of air-conditioned office and computer services area and additionally moderately air-conditioned atria area. In order to use waste heat from the production facility nearby, three thermally driven chillers are installed with a rated chilling capacity of 350 kW each (total: 1.05 MW), to supply cold for slab cooling and supply air cooling of the Tech­nology Center. The installed cooling technology are adsorption chillers from the Japanese manufac­turer Mayekawa. At rated conditions, the total heat input for the chillers is approx. 1.7 MW. However, during operation of the plant it turned out that less than the originally expected 0.8 MW of waste heat was available. Remaining heat input for the chiller operation is provided by gas boilers. Figure 4 shows the Technology Center and one of the adsorption chillers.

Within Solarthermie 2000plus, a vacuum-tube collector system is added as third heat production sys­tem to assist the chiller operation in summer and for heating support in winter. The collector system consists of 1218 m2 aperture area of CPC Star Azurro collectors from Paradigma. At present, this col­lector is the largest system operated with pure water as collector fluid. At low collector temperatures with danger of freezing, a special control allows periodically circulation of the collector fluid for some seconds in order to transport heat at a low temperature level into the collector. In winter, solar pro­duced heat is used for slab heating at temperatures < 50°C in a new office building of the company. The collector went into operation in the end of 2007; the monitoring system was installed and is operated by the University for the applied sciences Offenburg. Figure 5 provides a scheme of the system.