Conference Year
2021
Keywords
CO2, Thermal Storage, Energy Cost
Abstract
Application of Carbon Dioxide as a natural, non-toxic, non-flammable refrigerant in refrigeration systems is steadily gaining interest, especially in locations with moderate climate, like Europe or Canada. However, it is a well-known fact that at higher ambient conditions, when CO2 system operates in transcritical mode, system efficiency is substantially reduced. Currently, there is a large variety of different techniques aimed at the CO2 refrigeration system efficiency enhancement at transcritical operation, like vapor injection, ejectors, expanders, multi-stage compression with intercooling (and combinations thereof) to name a few. On the other hand, thermal storage devices are gaining popularity in many applications including supermarkets, As an alternative approach to other CO2 system enhancement, a novel MT refrigeration CO2 system with a closed couples thermal storage battery is introduced and evaluated. Thermal storage system has a phase change temperature higher than the evaporator temperature and facilitates heat exchange between CO2 and Phase change material. Its operation is simple to be controlled and has, within limitations, very high roundtrip efficiency. The current paper provides the description of this system, explains its modes of operation, reviews experimental investigation of the system with a scaled down thermal storage device. Performance of this system is evaluated using analysis model at different modes of operation. Scaled for a typical 4TON MT REF system, its monthly energy and energy cost consumption is evaluated and compared with a similar sized ejector-enhanced CO2 system, having typical weather and load profile, while applying different energy cost models. Performance of this system is evaluated using analysis model at different modes of operation. Scaled for a typical 4TON MT REF system, its monthly energy and energy cost consumption is evaluated and compared with a similar sized ejector-enhanced CO2 system, having typical weather and load profile, while applying different energy cost models.