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The solar absorption-subcooled compression hybrid cooling system (SASCHCS) is potentially an economical solution for high-rise buildings. The hybrid system is subjected to off-design operation frequently, owing to the changes in solar irradiance and cooling demand. However, a large amount of iterations and difficult convergence are encountered in the traditional off-design modeling. Hence, our present study contributes to the development of an off-design model that is exact and can be solved conveniently. A novel modeling method based on the combination of an absorption subsystem described by the characteristic equation and a compression subsystem modeled by the lumped parameter method is proposed. A prototype and corresponding experimental system are developed to verify the model. A good agreement between the theoretical result and test data is displayed. The maximum deviation is less than 4%. Subsequently, the performance of the facility for different operating conditions is simulated and analyzed. We found that the subcooling power relies significantly on the compressor speed, i.e., a reduction by 58.6% when the compressor speed reduces by 80%. In addition, a high temperature and low flow rate of cooling water in the compression subsystem is adverse to the performance of the hybrid system. Our study can serve as the foundation for the operational analysis of the solar absorption-subcooled compression hybrid cooling system as well as promote its development.

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Solar assisted hybrid cooling systems are promising for the energy saving of refrigeration systems. In most cases, the solar thermal gain is only able to power the heat-driven process of facilities in part of the working period. Therefore, the reduction of compressor power strongly depends upon the duration of heat-driven processes, which has not been addressed properly. Motivated by such knowledge gap, the thermodynamic understanding of solar assisted hybrid cooling systems is deepened through considering the duration in heat-driven processes. Three absorption-compression integrated cooling cycles were taken as examples. It is found that optimal parameters, e.g., inter-stage pressure and temperature, corresponding to various performance indicators trend to be identical, as the duration of heat-driven processes is taken into account. Furthermore, the optimal parameter for different working conditions was obtained. It is displayed that the dimensionless optimal intermediate temperature of layout with the cascade condensation process varies slightly, e.g., 4%, for different conditions. Moreover, the fall of compressor power in entire working periods is nearly independent upon the intermediate temperature. The paper is favorable for the efficient design and operation of solar assisted hybrid cooling systems.