Hybrid solar energy and waste heat driving absorption subcooling supermarket CO2 refrigeration system: Energetic, carbon emission and economic evaluation in China

A novel hybrid solar energy and waste heat driving absorption subcooled carbon dioxide (CO2/R744) booster refrigeration system (SE + WH) is proposed to improve the energy efficiency of the traditional CO2 refrigeration system used in supermarkets. The thermodynamic and energy conversion model of the system is established. Then, the optimization method of the two-dimensional golden section search algorithm is introduced to optimize the system energy efficiency taking the variation of ambient temperature and solar radiation intensity into ac-count. Moreover, considering the maldistribution of solar energy and the influence of meteorological conditions in China, eight typical cities are selected to assess the annual performance factor and life cycle carbon emissions to achieve energy saving and carbon emission potentials. The performance of hybrid solar energy and waste heat driving absorption subcooled CO2 booster refrigeration system is the best with the COP enhanced by 3.05-42.30 % at the solar radiation intensity of 1200 W/m2 and the temperature of 0-35 degrees C in contrast to the baseline system. In addition, the discharge pressure of the new proposed hybrid system can be reduced by 7.86 % when the ambient temperature is 34 degrees C. The annual performance factor of the new proposed hybrid system in Haikou can be increased by 14.47 %, and the life cycle carbon emissions are effectively reduced by 39.54 %. The payback period is also reduced by 4.01 % and 3.37 % for Beijing and Shanghai. Consequently, the novel configuration of the hybrid absorption subcooling subsystem is recommended, particular in hot or warm climate areas with rich solar energy.