Supermarket demand response using the CO2 booster cycle: model development, validation, and simulations of load shed events with CO2 booster systems.

Transcritical CO2 booster systems are becoming more popular in North America, as federal and state regulations push the phase-down of HFC refrigerants. At the same time, the use of refrigeration systems for demand response – functions to increase, decrease, or shift electric load in response to utility needs – is gaining interest as better and less expensive communication and controls become more common. In the Booster cycle, the medium temperature and low temperature stages of the booster cycle are inherently interlinked, so a temporary interruption of one stage may impact the other. This paper describes the use of a transient CO2 booster cycle model to study the impact of load-shed events on overall cycle performance and behavior. The results show the relative “return” (kW total power reduction per kW of load shed) for demand response on each stage and the impact of sheds on each stage on overall behavior. In a system with a roughly 2:1 load ratio, the power reduction of 0.85-0.91 kW per kW of load shed was seen with LT capacity reductions, compared to 0.59-0.60 kW per kW of load shed with MT capacity reductions.