A CO2 refrigeration system comprises a
refrigeration circuit in which circulates CO2 refrigerant
between a compression stage in which the CO2 refrigerant
is compressed. A condensation stage is provided in which
the CO2 refrigerant releases heat and is accumulated in a
condensation reservoir. An evaporation stage is provided
in which the CO2 refrigerant is expanded to a gaseous
state to absorb heat from a fluid for refrigeration, with
at least a portion of CO2 refrigerant exiting the
evaporation stage being directed to a supra-compression
circuit comprising a supra-compression stage in which the
portion of CO2 refrigerant is compressed. A heat
exchanger is provided by which the compressed CO2
refrigerant is in a heat-exchange relation with a
secondary-refrigerant circuit, such that the compressed
CO2 refrigerant releases heat to a secondary refrigerant
used for heating purposes. Pressure-regulating means
control a pressure of the compressed CO2 refrigerant
being returned to the condensation stage.