Document Type

Conference Paper

Date of this Version




author = {Madhur Behl and Truong X. Nghiem and Rahul Mangharam},

title = {Green Scheduling for Energy-Efficient Operation of Multiple Chiller Plants},

booktitle = {33rd IEEE Real-Time Systems Symposium (RTSS)},

year = {2012},

address = {San Juan, Puerto Rico},

month = {December},



In large building systems, such as a university campus, the air-conditioning systems are commonly served by chiller plants, which contribute a large fraction of the total electricity consumption of the campuses. The power consumption of a chiller is highly affected by its Coefficient of Performance (COP), which is optimal when the chiller is operated at or near full load.

For a chiller plant, its overall COP can be optimized by utilizing a Thermal Energy Storage (TES) and switching its operation between COP-optimal charging and discharging modes. However, uncoordinated mode switchings of chiller plants may cause temporally-correlated high electricity demand when multiple plants are charging their TES concurrently.

In this technical report, a Green Scheduling approach, proposed in our previous work, is used to schedule the chiller plants to reduce their peak aggregate power demand while ensuring safe operation of the TES. We present a scheduling algorithm based on backward reach set computation of the TES dynamics. The proposed algorithm is demonstrated in a numerical simulation in Matlab to be effective for reducing the peak power demand and the overall electricity cost.


Energy efficient buildings, cyber physical systems, peak power reduction, green scheduling, scheduling algorithms, control systems



Date Posted: 02 June 2012

This document has been peer reviewed.