Abstract
Refrigeration systems account for a huge share of supermarkets energy consumption. Commercial refrigeration systems with natural refrigerants are becoming more and more popular, and in particular CO2. Carbon dioxide systems are affected by efficiency and capacity reduction at high ambient temperature, due to the low critical temperature. For this reason, different options have been widely analysed and successfully implemented, such as the use of two-phase ejectors, economised cycles, flooded evaporators, etc. An additional possibility to increase the efficiency is the use of heat storages to shift the power consumption from periods of disadvantageous ambient and boundary conditions, and thus low system-efficiency, to those periods with more favourable conditions. This paper analyses the suitability of different low temperature heat storage concepts to increase the efficiency of CO2 refrigeration systems for supermarkets; in addition it evaluates their possible integration with high efficiency lay-outs intended for hot climates. Case studies of the most promising concepts comprise simulations, which use dynamic models of the storage and consider transient boundary conditions for weather and refrigeration loads.
