Continuous production of cryogenic energy at low-temperature using two-stage ejector cooling system, Kalina power cycle, cold energy storage unit, and photovoltaic system

摘要

Continuous cryogenic refrigeration is the need for different industries. The purpose of this study is to produce continuous refrigeration at a temperature of 171 K. To this end, a two-stage ejector cooling system is used. The first ejector cycle with propane as working fluid provides the refrigeration up to a temperature of 233 K. The second ejector cycle with ethylene as working fluid utilizing the refrigeration provided at the previous cycle, as a heat source, provides refrigeration up to a temperature of 171 K as the final product of the cycle. Kalina power cycle is used to reduce the cycle's consumed power, so that utilizing the ejector cycle's excess heat produces a power of 2753 kW and, as a result, the coefficient of performance of the refrigeration cycle increases from 0.7821 to 0.8277. By employing solar energy through the photovoltaic panels, the power required by the system is provided. With the use of photovoltaic system software, a 48 MW grid-connected monocrystalline photovoltaic unit for a geographical location of Chabahar, Iran is simulated. This system has an annual performance ratio of 79.3% and, on average, produces energy of 80,224 MWh per year. Phase change material is used to provide end user cold duty continuously; so that during the day the half of produced cold duty is delivered to the end-user, and the remaining is stored at phase change material, and during the night, this stored cold duty is recovered and delivered to the end-user. The exergy analysis shows that the maximum share dedicated to photovoltaic panels is 84.45% of the total exergy destruction of the system, which followed by compressors, heat exchangers, and ejectors with a value of 7.710%, 4.270%, and 1.24% of total exergy destruction of the system. The exergy efficiency of the total system is 28.97%. The results obtained from sensitivity analysis indicate that by increasing the operating pressure of the Kalina cycle up to 1500 kPa, the consumed power of the total system decreases by 12.37%. Besides, the coefficient of performance of the refrigeration cycle reaches to 0.9150.