Refrigerated display case defrosting using inferential ice sensing

By avoiding unnecessary defrosting cycles in refrigerated display cases, it may be possible to reduce the energy used in supermarkets by 720 kWh/month per case. We propose a strategy to achieve these savings with new technology for performing automatic, as needed defrosting. This new defrosting system will use temperature sensors that already exist within most commercially available refrigerated display cases to infer the formation of ice and, hence, the need for defrosting. Because we propose to use sensors that are already installed, the application of this new defrost technology requires only software modifications and is therefore amenable to both low cost retrofits and use in new refrigeration systems with little, if any, additional cost to the manufacturer. In this paper we describe the theoretical basis for our inferential ice sensor and demonstrate its effectiveness on refrigeration equipment in a laboratory setting. From this theoretical analysis and measurements of energy used in defrosting we show the basis for the anticipated energy savings.