Solar cooling with parabolic trough collectors and steam jet ejector chiller

The cooling need is growing not only in offices but also in the production sector. Cold is needed for cooling of production halls where sensitive machines are operated or where sensitive products are handled as well as for cooling within the production processes. Just like for air-conditioning in the building sector, these cooling needs are higher in summer than in winter due to passive solar gains and higher ambient temperatures in general.

The goal of this project is to realize industrial solar cold production with a solar thermal powered steam jet ejector chiller. A steam jet ejector chiller uses steam as refrigerant and has a higher coefficient of performance than conventional absorption chillers when operated at high primary temperatures and pressures. Therefore, concentrating collectors, that still operate at high efficiencies at higher temperatures are ideal for solar thermal cold production. Parabolic trough collectors can produce the motive steam needed directly when operated in direct steam generation mode. Therefore, a direct coupling of the two technologies is very promising.

The first part of the project is dedicated to finding a heat transfer medium that provides freezing protection for the collector field in winter but is also suitable for the steam jet ejector chiller. Then, a system concept is elaborated depending on the chosen heat transfer medium.

Both components are further developed to meet the requirements of a direct coupling of the technologies. As for the parabolic trough collectors the focus is on direct steam generation that works satisfactorily under laboratory conditions. It is now being further developed and tested under realistic operating conditions. The steam jet ejector chiller will be adapted to the chosen heat transfer medium and the steam transfer interface between collector and chiller will be treated.

A detailed system and control concept will be developed. The separate components will be built and tested separately. After the successful separate tests, a complete system with a cooling capacity between 5 and 10 kW will be installed at the test facility and monitored. Both the system and the control concept will then be tested under real operating conditions and can be optimized throughout the test period. At the end of the project, a functioning pilot plant will serve as a showpiece helping to realize first demonstration plants in the near future.