The availability of an energy storage medium allows the refrigeration system operation to be decoupled from the refrigeration loads. In cold storage warehouses, the stored products themselves have the potential for use as an energy storage medium. By precooling the stored products during hours of low electricity prices, it is possible to idle or "float" the refrigeration system during periods of high electricity prices. The shift in electrical usage to low-cost periods has the potential of yielding refrigeration system operating cost savings. The primary thrust of RP-1154 was to investigate the technical and economic feasibility of utilizing products in refrigerated warehouses as thermal energy storage media to minimize refrigeration system energy costs under real-time pricing rate structures.In this paper, we present a simple method that forecasts whether or not demand shifting the refrigeration system operation on a daily basis results in operating cost savings. The method includes predicting the maximum allowable floating duration based on the outside air temperatures for the next day and establishing the floating period that yields the greatest operating cost savings. A simple price ratio criterion was found to be a good indicator of energy cost savings by demand shifting.For the utility data and cold storage warehouse cases analyzed, operating cost savings through demand shifting are relatively small compared to the annual refrigeration system operating cost. Installation of additional refrigeration capacity results in projected savings in the range of 7% to 11%. Greater cost savings are possible for utility data that have large price excursions between daytime and nighttime.

Units: Dual