Augmenting the comfort heating capacities of HVAC-integrated transcritical CO₂ refrigeration systems

A characteristic of transcritical CO₂ (TCO₂) refrigeration systems that differentiates them from conventional synthetic refrigerant systems is the formation of “high-grade” heat in the rack discharge line – more specifically, non-condensing high-temperature and high mass-flow refrigerant fluid. This characteristic lends TCO₂ systems remarkably well to heat recovery for the purposes of comfort space heating.

The amount of heat that can be generated and recovered is limited by the system refrigeration load (i.e. the quantity of fridges and and cool rooms). For most Australian supermarket applications, the connected load is sufficient for integrated TCO₂ systems to maintain store comfort conditions throughout winter.

However, exceptions do exist. These include stores built in cold climate zones – such as in Australia’s alpine areas – or stores built with unusually high ceilings. Here, supplementary heating systems such as gas-fired boilers are typically employed. These run contrary to the sustainability aspirations of natural refrigerant systems. Woolworths has successfully trialled smarter methods for augmenting heating capacities, including the use of heat pump evaporators.