Energy, exergy, economy analysis and multi-objective optimization of a novel cascade absorption heat transformer driven by low-level waste heat

To solve the increasingly serious global energy problem, an innovative cascade absorption heat transformer system using industrial low-level waste heat is presented in this paper. Based on an accurate model and simulations, the cascade system is studied in terms of an energy, exergy, and economy analysis. To achieve a trade-off between the thermodynamic and economic performance, a multi-objective optimization method is used to optimize the system. The thermodynamic performance (total exergy destruction) of the multi-objective optimized design is 3.64% higher than its ideal minimum value, while the economic performance (total annual cost) is 2.74% higher than its ideal minimum value. This indicates that the multi-objective optimization scheme can provide better comprehensive performance than single optimization schemes for the cascade absorption heat transformer system. In addition, the results show that the exergy destruction rate is 74.30%. The exergy destruction of the NH3/H2O system accounts for 55.62% of the total input exergy; thus, improvements of this system should be prioritized.