Passive thermal energy storage in refrigerated warehouses

This paper investigates operational strategies that use stored products as thermal mass to shift refrigeration loads to more favorable operational periods (low energy cost periods, lower outdoor air conditions, etc.) allowing an opportunity to reduce system operating costs. An integrated model of the stored product, warehouse air, and warehouse structure is developed and thermal response characteristics are predicted for a selected warehousing facility. Simulated results are validated with experimental measurements. Food quality impacts associated with the temperature cycling caused by potential operating strategies are discussed. Results from this investigation indicated that a full load-shifting control strategy would save $82,000 (US) ($0.40/ft2/year or $4.28/m2/year) annually over the test facilityʹs current operational strategy, representing 53% of the total cooling cost. Predicted maximum warehouse temperature variation is 5.6°C, which is not expected to cause significant product quality changes in the temperature range (below−18°C) studied.