Strategy for Energy Savings in a Commercial Building Air-conditioning System with Chilled Water Storage: A Case Study in a Retail Mall in Thailand

In this study, a commercial retail mall is used as a case study to integrate a chilled water storage (CHWS) with the existing chilled water system to reduce electrical energy consumption and capitalize on the economic benefits of electrical energy saving cost and the differential between on-peak and off-peak tariffs. This study aims to improve the chiller efficiency in three operating strategies: full storage, partial storage load leveling, and partial storage demand limiting, by operating the chillers at optimal part load conditions. Technical and economic assessments were conducted to determine the necessary storage capacity and appropriate operational strategies. In comparison to the existing operation, which uses two 800 RT chillers continuously during on-peak hours and one chiller operating at 20-30% capacity during off-peak hours, the proposed systems: three 800 RT chillers with a 9,150 m³ tank for full storage, one 800 RT and one 260 RT chiller with a 3,292 m³ tank for partial load leveling, and two 800 RT chillers with a 4,987 m³ tank for partial demand limiting, demonstrate significant potential to reduce electrical energy consumption. The full storage strategy achieves the lowest electrical energy consumption, followed by partial demand limiting and partial load leveling. Economically, partial demand limiting strategy emerges as the most feasible, providing a payback period of 7.42 years and an internal rate of return (IRR) of 14.92%. This is more favorable compared to payback periods of 8.6 and 9.65 years and internal rate of return of 12.08 and 10.33% for partial load leveling and full storage strategies, respectively.