Energetic, exergetic and financial evaluation of a solar-powered absorption chiller integration into a CO2 commercial refrigeration system

Abstract

This study investigates the integration of a solar absorption chiller by means of subcooling to a CO2 booster system that serves the refrigeration needs of a supermarket refrigeration plant with an installed capacity of 80 kW and 20 kW for medium and low-temperature regimes, respectively. The proposed energy saving configuration is analyzed in an energetic, exergetic, and financial manner, using the climatic data for the city of Athens, Greece. The current approach constitutes the theoretical reference for the actual implementation of this novelty either in new plants or as a retrofit in existing ones. The proposed solution includes the employment of a single-stage absorption chiller operating with LiBr–H20 working pair, which is driven by heat produced in evacuated tube collectors installed in the store’s rooftop. The energy analysis is conducted with validated numerical models that are developed in MATLAB using the CoolProp library. The collecting area and the corresponding chiller capacity of the proposed configuration are selected through financial evaluation. More specifically, the collecting area is analyzed parametrically from 25 m2 to 200 m2. Finally, 100 m2 of collecting area with 60 kW of chiller capacity are proved to be the optimum solution financially with 8.4 years payback period and 44.57 k€ net present value. This optimum solution results in an annual power consumption decrease of 8.12% which leads to energy savings of 27.45 MWh/year.