Improving Demand Response Potential of a Supermarket Refrigeration System: A Food Temperature Estimation Approach

In a smart grid, the load shifting capabilities of demand-side devices such as supermarkets are of high interest. In supermarkets, this potential is represented by the ability to store energy in the thermal mass of refrigerated foodstuff. To harness the full load shifting potential, we propose a method for estimating food temperature based on measurements of evaporator expansion valve opening degree. This method requires no additional hardware or system modeling. We demonstrate the estimation method on a real supermarket display case, and the applicability of knowing food temperature is shown through tests on a full-scale supermarket refrigeration system made available by Danfoss A/S. The conducted application test shows that feedback based on food temperature can increase the demand flexibility during a step by approximately 60% the first 70 min and up to 100% over the first 150 min, thereby strengthening the demand response potential of supermarket refrigeration systems.