Comparison of energy consumption: Glycol chiller versus CO₂ rack system for refrigerated cabinets

Continuous research into new and more environmentally friendly solutions in commercial refrigeration has brought the industry to use refrigerant gases like HFOs, natural gas and CO₂. On the other hand, the HVAC&R industry is familiar with glycol chillers (charged with a low quantity of R290 or HFO) used to cool down a secondary fluid at negative temperatures (as in process cooling). But can this solution be as efficient as a transcritical CO₂ (TCO₂) rack with parallel compressors in a medium-temperature supermarket application?

This analysis compares energy consumption between installations in different climate regions of Italy (Genova, Padova, Roma, Catania) and gives some indications of where a glycol chiller solution can be more competitive than a refrigeration TCO₂ rack (medium-temperature supermarket applications). The presentation also includes a description of a glycol chiller system connected to medium-temperature refrigerated cabinets for the “cold distribution” of glycol water at a temperature of -8°C (chiller supply temperature).

The analysis refers to a glycol chiller equipped with a semi-hermetic compressor, an aluminum condenser with a micro-channel that allows for a reduced-volume refrigerant circuit, an electronic fan with variable speed and an electronic pump with constant Delta T (water in–water out) operation of the glycol. This solution is easy to install and maintain.

The glycol chiller system’s strengths compared to a TCO₂ rack system are its low refrigerant charge (the analysis refers to chillers charged with R290 or R448A refrigerant gases), lower working pressure, modularity and flexibility using a glycol secondary fluid, and most important its lower energy consumption in hot ambient conditions.