Evaluation of Energy Savings by Optimization Control in Thermal Energy Storage System

By using both passive and active thermal energy storage (TES) systems, a significant portion of the on-peak cooling can be shifted to the off-peak period and thus the energy costs associated can be considerably reduced. This paper summarizes the results of a comprehensive evaluation of the performance of optimal and conventional control strategies for combined passive (i.e., pre-cooling building thermal mass) and active (i.e., charging ice storage tanks) TES systems for typical commercial buildings in the US. Specifically, the paper examines the impact of selected design and operating factors on the performance of optimal control strategies for combined passive and active TES systems. Among the factors analyzed include building shape, climate, adaptation of optimization control, TES systems control, and utility rate structure. The analysis is performed using a detailed simulation energy program (EnergyPlus) modified to incorporate TES models and various optimization algorithms. The results of the analysis indicate that optimal TES priority controls can achieve up to 35% in on-peak electricity demand reduction and up to 30% in total electrical energy cost savings.