Exergoeconomic optimization of solar absorption refrigerators

Abstract

This work reports the exergoeconomic optimization of a solar heat-driven refrigeration plant. The system’s first and second law efficiencies, as well as refrigeration exergetic cost, are the selected objective functions. A dimensionless mathematical model is developed for generality, and the methodology comprises: i) Energy analysis, ii) Exergy and exergoeconomic analyses, and iii) Optimization problem formulation. The optimization process involves i) selecting the optimal collector-to-hot-exchanger coupling temperature, ii) optimizing generator-to-evaporator size ratios, and iii) distributing total thermal conductance among system components. Initially, for a specified set of model parameters (collector-absorption refrigerator sizes ratio, collector stagnation temperature, and cold space temperature), the three-way optimized parameters set was found as (τ_H, β_H, β_L)3_wo = (1.35; 0.235; 0.25) to obtain maximum efficiencies and minimum refrigeration exergetic cost. For B = 0.1, the three-way optimized parameters result in a first-law efficiency (η_Ι) of 0.42 and a second-law efficiency (η_ΙΙ) of 0.28, with the refrigeration exergetic cost reducing by 56.5 % within the third optimization parameter tested range, highlighting the importance of operating with the three-way optimized configuration. It was also determined that the absorber and condenser heat exchangers should be allocated approximately 50 % of the total thermal conductance inventory to achieve optimal performance. A parametric analysis determined that the three-way optimized parameters set is nearly invariant (“robust”) concerning changes in model parameters, with the collector coupling temperature (τ_H) varying by less than 9 % across different system configurations. These findings provide a novel, simplified mathematical model for solar absorption refrigeration, offering practical insights for efficient system design.