Simulation Assessment of a Near-Optimal Control Algorithm for Central Cooling Plants with Chilled Water Storage

This paper presents the results of the evaluation of a control algorithm for minimizing energy costs in cooling plants with chilled water storage. The control approach requires very little plant information, is computationally simple, and is general in the sense that it is applicable to different types of utility rate structures including real-time pricing (RTP), time-of-use (TOU) and TOU with demand charges. The control algorithm was evaluated using a model of an existing chiller plant of significant complexity built in a simulation testbed for different combinations of storage sizes, load profiles and electricity rates. The performance of the near-optimal algorithm was compared with three different approaches: optimum control (baseline), and two heuristic control strategies commonly used for thermal energy storage. The energy costs obtained with the near-optimal control algorithm were within approximately 2% of the costs associated with optimal control. Comparison with the heuristic control strategies shows that significant energy savings can be achieved with the proposed control method.