Energy Performance Analysis of a Solar Refrigerator Using Ecological Refrigerants
The development of sustainable energy technologies must be a priority given the rising global energy demand and global warming gases emission. In this work, the energy evaluation of a small-capacity direct-current refrigerator with internal heat exchange using R600a, R290, R717, and R134a as a base case, for autonomous solar refrigeration, is discussed. A thermodynamic model was developed to assess a 200 W refrigerator performance at evaporation temperatures of -32/-10°C, condensation temperatures of 35/46 °C, and different internal heat exchanger effectiveness values while considering the environmental conditions in the city of Barranquilla whose metropolitan and urban area presents a great potential for solar refrigeration. Results showed that the R290 system coefficient of performance was up to 2.6% higher than that of the R134a. The R600a system coefficient of performance was up to 2.7% higher than that of the R134a, but only under the most favourable conditions. The R717 system surpassed the compressor discharge temperature limits so it was found unsuitable for the present application. Moreover, the internal heat exchanger was found beneficial to reduce the exergy destruction in the compressor and expansion valve but increased that in the condenser for R134a, R600a, and R290. The internal heat exchanger recommended effectiveness should be around 0.4 for R600a or 0.3 for R290 at an evaporation temperature of -32 °C. For an evaporation temperature of -10 °C, the IHX effectiveness can be up to 0.5 for both R600a and R290. Finally, the maximum power consumption of the solar R290 refrigeration system was estimated around 4.08 kWh and 2.28 kWh at evaporation temperatures of -32 °C and -10 °C, respectively, which could be covered by a solar panel area of 3.76 m2 y 2.10 m2, respectively, while similar values were obtained for the solar R600a refrigeration system.