A modern supermarket energy control system has a concurrent need for electricity, food refrigeration and
space heating or cooling. Approximately 10% of this energy is for conventional gas-powered heating. In
recent years, the use of CO2 as a refrigerant in supermarket systems has received considerable attention
due to its negligible contribution to direct greenhouse gas emissions and excellent thermophysical and
heat transfer properties. CO2 refrigeration systems also offer more compact component designs over a
conventional HFC system and heat recovery potential from compressor discharge. In this paper, the heat
recovery potential of an all-CO2 cascade refrigeration system in a supermarket has been investigated
using the supermarket simulation model ‘‘SuperSim’’ developed by the authors. It has been shown that
at UK weather conditions, the heat recovery potential of CO2 refrigeration systems can be increased by
increasing the condenser/gas cooler pressure to the point where all the heat requirements are satisfied.
However, the optimum level of heat recovery will vary during the year and the control system should be
able to continuously optimize this level based on the relative cost of energy, i.e., gas and electricity.