Methodology for determining the optimal operating strategies for a chilled-water-storage system - Part II: Project application

摘要

A new methodology for determining the optimal operating strategies for a chilled-water-storage system under a time-of-use electricity rate structure is introduced in Part I. In Part II, a practical project is introduced to illustrate the application of this methodology. It is a large-scale chilled-water system with a 5.4 million gallon water storage tank and an advanced control system. The methodology proposed in this dissertation is successfully applied in this system to search the optimal operations of the thermal energy storage (TES) and chiller plant. The profiles of system cooling load and weather conditions between March 2007 and February 2008 are selected as the baseline. The utility rate structure is introduced and analyzed to define the off-peak and on-peah periods for the summer and winter months. Each component is modeled based on the trended data, and an hourly simulation is performed month by month. Six scenarios are designed and simulated to study the savings due to TES application, TES optimization, and plant optimization. The chiller chilled water leaving temperature and cooling tower approach temperature are optimized to further improve the plant performance. The simulation results show that the savings due to TES operation optimization and plant optimization could be very significant compared with the savings due to TES application. Many of these optimal control strategies have been implemented in the actual optimization performed on the system and achieved significant savings.