Structure and control co-optimization for an ejector expansion heat pump coupled with thermal storages

Abstract

Optimal design and control are often coupled tasks for improving energy system performances. There is a lack of study on the structure and control co-optimization of heat pump coupled with thermal energy storages, which can enhance the penetration levels of intermittent renewables in integrated energy systems, thus we proposed a coupled dynamic optimization method for the structure and control co-optimization of this kind of dynamic energy system, and applied it successfully to a transcritical CO2 ejector expansion heat pump coupled with hot and cold water storages for thermal energy charging. Based on a complicated nonlinear dynamic system model considering thermal stratification in thermal energy storages, the structure and control co-optimization solutions were obtained for this coupled system during energy charging by using the co-optimization method with genetic algorithm. The detailed structures of gas cooler, evaporator, hot and cold energy storage tanks were optimized, then a dynamic optimal control strategy was developed for the whole charging process. The overall coefficient of performance can be increased by 23.2% and the total power consumption can be reduced by 17.6% using this newly developed co-optimization strategy, compared to the constant control parameter strategy. This study would be helpful for a structure and control co-optimization of other dynamic or stable energy systems.