Solar driven ejector cooling system employing natural refrigerants: thermo-economic analysis and optimization strategy

Solar heat driven ejector cooling systems are interesting solutions for air conditioning, since they offer the possibility to use low-grade solar energy, by also saving the considerable electric energy required by conventional vapor compression cycles. This paper presents a thermodynamic and economic analysis of a medium size (10 kW) hybrid multi-ejector compressor assisted cooling system, driven by solar energy. The system is investigated from an energetic and economic point of view, employing real component models for heat exchangers, compressors, pumps and ejectors, by adopting ammonia and propane as refrigerants. The system has been designed at the maximum cooling load as best compromise between performance and costs, analysing different climate conditions in terms of ambient temperature and solar radiation. The compressor is integrated to guarantee the proper system operation when the solar source is not sufficient to satisfy the cooling load. The seasonal performance in terms of SEER is evaluated and compared to that of a traditional vapor compressor cycle. Also, an economic comparison between the proposed system and the reference one has been carried-out, defining the cost-effectiveness and the pay-back period.