Comparative study on two low-grade heat driven absorption-compression refrigeration cycles based on energy, exergy, economic and environmental (4E) analyses

Absorption-compression refrigeration cycle is widely studied for its energy saving potential. In this paper, a comparative study on a novel absorption-compression cycle with an evaporator-subcooler (ES) and a conventional absorption-compression refrigeration cycle with an evaporator-condenser (EC) has been done for the first time. The comparative investigation is based on energy, exergy, economic and environmental (4E) analyses. The results show EC saves 22.5% more electric energy than ES at the cost of consuming 4.6 times more low-grade heat energy than ES. EC has a higher COP, but has a lower COPg, which takes into account both electric power and low-grade heat power. From the exergy analysis, the exergy efficiency of ES is 31.6%, 54.1% higher than EC's (20.5%), indicating ES has a much better exergy performance. The economic analysis shows that when waste heat is used, EC has a better economic performance and when solar heat is used, ES has better practical application potential. The effect of electricity price and CO2 tax rate on economic performance is also studied. The better cycle for different electricity price and CO2 tax rate are recommended. The results and understanding of the two cycles can be used as the basis for cycle selection and design.