Solar powered water vapour/steam ejector chiller

As part of the research project “ProSolar”, a prototype of an innovative solar cooling system with water as the only working fluid was developed. The system produces up to 80 kW chilled water at 12 °C, used to cool a laboratory building at Karlsruhe University of Applied Sciences. The motive steam is provided at 3.7 bar and 140 °C by means of direct evaporation in CPC vacuum tube collectors with a total capacity of 200 kWth. The demonstration plant consists of a double stage steam ejector chiller to produce chilled water with sufficient power to cool a building. The system is designed as an open process, without hydraulic separation between the solar collector field, chiller and cold water piping system. In order to bridge short periods of cloudiness, the system is equipped with latent heat storage with polyethylene as the main PCM agent and a melting point of approximately 130 °C. In addition, a latent cold storage unit on the basis of a paraffin-water dispersion with a melting point of approximately 12 °C is situated inside the building being capable of providing cooling for approximately 6 hours. The systems’s practical application is two-fold: supplying chilled water during summer time and boosting the temperature of the district heating system of the University during the winter. Experience from the first two years of operation have shown thermal COP’s up to 0.6 (electrical COP up to 9) and about 100 MWh of heating provided over the winter 20014/15. The project consortium consisted of Karlsruhe University of Applied Sciences, Fraunhofer UMSICHT and the companies GEA Wiegand and Ritter Group