Heating and cooling with a small scale solar driven adsorption chiller combined with a borehole system - recent results

Since July 2007 different prototypes of a small capacity reversible adsorption chiller/heat pump from the company SorTech AG have been operated in a heating and cooling system at Fraunhofer Institute for Solar Energy Systems ISE in Freiburg, Germany. In this paper we present an overview of the results of two different prototypes in the period from July 2007 to July 2009. The first prototype was operated successfully for one cooling and almost one complete heating season. The thermal performance was very good reaching a cooling COPth of 0.51 and a heating COPth of 1.4. We obtained a somewhat lower performance with the second prototype (COPth cooling 0.46, heating 1.25) for a years operation without any maintenance. This result can be explained through the slow degradation observed during this period. From the analysis of the electricity consumption one can draw the conclusion that in the present system, about 40% (heating) to 50% (cooling) of the electricity consumption of the whole system (excluding the solar circuit) is due to the adsorption machine and the pressure drop of its internal hydraulic circuits. These have already been reduced in the new machine ACS08 according to the technical datasheets from SorTech AG. Nevertheless, the electric COPel,ACS of the adsorption machine is still very high (16 for cooling and 45 for heating). The solar system adds only further 10% (heating) to 24% (cooling) to the total electricity demand. The primary energy ratio for cooling is low due to the low solar fraction of only 45% during this monitoring period.