Chiller Start/Stop Optimization for a Campus-wide Chilled Water System with a Thermal Storage Tank Under a Four-Period Electricity Rate Schedule

Abstract

The existence of a 1.4-million-gallon chilled water thermal storage tank greatly increases the operational flexibility of a campuswide chilled water system under a four-part electricity rate structure. While significant operational savings can be expected, the complication in the rate structure also requires more involved control over the tank charging and discharging processes. A chiller start-stop optimization program has been 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 daily, based on the prediction of the campus cooling load within the coming 24 hours. With timely and accurate weather forecasting, the actual tank charging and discharging process closely matches the simulation.