The existence of a 1.4-million-gallon chilled water thermal storage tank greatly increases the operational flexibility of a campus-wide chilled water system under a four-price timeof- use electricity rate structure. While significant operational savings can be expected, the complication in the rate structure also requires more sophisticated control over the charging and discharging processes of the thermal storage tank.

A chiller start-stop optimization program was developed and implemented into the energy management and control system (EMCS) to determine the number of chillers that need to be brought on line and the start and stop times for each chiller every day, based on the prediction of the campus cooling load within the next 24 hours. With timely and accurate weather forecasting, the actual tank charging and discharging process closely matches the simulated process. The chiller plant’s operating schedules are dynamically optimized to deliver required cooling capacity at lowest possible operating costs.

Units: Dual