Operation of supermarket refrigeration units: a coupled district heating and electric network approach

Energy system integration between district heating and electrical domains is required for harvesting potential flexibility arising from sector coupling and support the transition to smart energy systems. This work presents a use case for using excess compressor capacity in refrigeration systems to locally couple district heating and electrical distribution networks by providing heat peak-shaving services to the district heating network. A tool-chain for explicit modelling of the electrical, thermal, and control domain using co-simulation is presented. It is based on a quasi-static electrical load flow model, a dynamic thermal-hydraulic district heating model and dedicated controller simulators integrated into the co-simulation information flow. The use case is implemented using the tool-chain and studied for different peak-shaving services request levels. The result shows that the proposed tool-chain is suitable for studying operational aspects of domain-linking components both at the network and the unit level. It is shown that the refrigeration unit can provide peak-shaving services while satisfying the primary cooling needs. Providing heat peak-shaving services allows distributed feed-in into the district heating network and potential new revenues. However, the refrigeration cycle coefficient of performance decreases as its operation changes from air/air to air/water mode.