Conceptual Design and Analysis of Hydrocarbon-Based Solar Thermal Power and Ejector Cooling Systems in Hot Climates

A combined thermal power and ejector refrigeration cooling cycle is proposed in this paper to harness low-grade solar energy. It explores the possibility of utilizing abundant and low-cost hydrocarbon as the working fluid. Hydrocarbon fluid has been identified as a promising alternative to existing high global-warming-potential (GWP) refrigerants (i.e., HFCs) in next-generation cooling and organic thermal power systems. Several typical alternative refrigerants are evaluated by considering their fundamental thermophysical properties: absolute pressure level, volumetric cooling capacity, surface tension, saturated liquid/vapor density ratio, and kinematic viscosity. Comparing with R1234yf, R1234ze, and R744 (CO2), hydrocarbon refrigerants, such as R290 (propane) and R601 (pentane), do have inherent advantages for either cooling or power generation purposes in hot climates. Fundamental phase stability and transition issues have been considered in designing hydrocarbon ejectors for combined power and cooling cycles operating at high ambient temperature. Thermodynamic energy and exergy analysis has indicated that the proposed stand-alone solar thermal system offers an effective way to sustainable energy production in hot and dry climates.