Performance analysis of heat recovery in CO2 refrigeration systems for heating electrification in supermarkets

Net-zero goals require all sectors to conduct decarbonization. Supermarkets, a significant part of the retail sector, are distinctive in opportunity to utilize heat recovery from CO2 refrigeration systems for heating load provision in attempt to electrify heating by eliminating gas consumption. This requires reliable computational models to comprehensively evaluate and analyze the heat recovery potential and the performance of different strategies before implementation. Additionally, the impact of supermarket heating electrification on electricity load variation, which would impact the connected systems and electric networks, needs to be quantified and included as a heat recovery evaluation criterion. This study, therefore, leverages a high-fidelity CO2 refrigeration system model to analyze the heat recovery performance of CO2 systems for heating electrification in a UK supermarket. Different heat recovery strategies are evaluated by energy performance, economic performance, a mismatch between recoverable heat and heating load, and the impact on electricity load variation. Results show that the instantaneous gas requirements for heating was reduced by at least 47 % using CO2 system heat recovery, with minor modifications on the default operation, up to being eliminated when the system is operated to maximize recoverable heat. Depending on the heat recovery strategies adopted, the electricity peak was shifted from midday to early-morning and summer to winter, and average and peak loads can be increased significantly. Among tested heat recovery strategies, increasing a condensing pressure to 90 bar when possible is overall the best strategy to balance low electricity consumption and costs, effective recoverable heat utilization and flat load profiles.