Control structure design for a CO2-refrigeration system with heat recovery

Abstract

In this work, we analyze a generic supercritical CO2-refrigeration system with parallel compression, based on systems used for supermarket use. In order to maximize energy efficiency, this system has a “heat-recovery” function, in which part of the heat rejected at high pressure and temperature can be recovered to provide heating. Operating conditions and active constraints are strongly affected by seasonal requirements and ambient temperature. Thus, it is necessary to find a control structure that satisfies operational constraints and maintains (near-)optimal operation with different sets of active constraints. In this paper, we use a systematic procedure to define such control structure.