Solar-driven hybrid refrigeration systems based on thermochemical processes

Identifier:  TDX:2717

Handle: https://hdl.handle.net/20.500.11797/TDX2717

Authors:  Fitó de la Cruz, Jaume

Abstract:
This doctoral thesis proposes two solar-based hybrid refrigeration systems where the central piece is a thermochemical process: an absorption / thermochemical hybrid system driven by low-grade solar thermal energy (< 120 ºC), and a compression / thermochemical hybrid refrigeration system driven by solar-PV energy and waste heat. The absorption / thermochemical hybrid system is presented in its most simple configuration, and its components and operating conditions discussed. A preliminary performance estimation is carried out with some ammonia-based working pairs finding the NH3/NaSCN and NH3/BaCl2 as interesting working pairs. A preliminary simulation of the hybrid system shows that it increases the solar coverage. The compression / thermochemical hybrid system is also defined and simulated in its refrigerant storage phase assisted with compression. A 2-front quasi-steady reaction model which accounts for heat and mass transfer limitations is used to preliminarily study the influence of some operating conditions and design parameters on the system’s reaction curve with the NH3/BaCl2 working pair. An experimental setup has been built to obtain experimental data from the compression-assisted refrigerant storage phase, and confront this data with the predictions obtained from the 2-front reaction model, with the objective of adjusting some parametres of the model. It is concluded that the adjusted model predicts the reaction curve with acceptable accuracy for almost all experiments, with small discrepancies. The proposed hybrid systems are expected to operate with solar energy, be relatively compact, store energy with reduced storage volume, and have a small degree of autonomy (a few hours within a daily operating cycle). These systems are promising for further study.