Chiller controller for optimized efficiency

Abstract

Systems, methods, and computer program products for staging chillers in a chiller group. Operational data is collected on chillers in a chiller group, and performance curves indicative of chiller efficiency generated for each chiller based on the operational data. During operation, a current thermal load and a current group efficiency is determined for the chiller group. Estimated group efficiencies are also determined for the chiller group for one or more scenarios in which one or more offline chillers are brought online, online chillers are taken offline, or both online chillers are taken offline and offline chillers are brought online. If the estimated efficiency of the chiller group is higher than the current efficiency for any of the scenarios, chillers in the chiller group are brought online or taken offline so that the chiller group operates in accordance with the most efficient scenario.

What is claimed is: 
     
         1 . A method of staging a chiller group including a plurality of chillers, comprising:
 determining a thermal load on the chiller group;   determining a current efficiency of the chiller group;   determining an estimated efficiency of the chiller group after executing a staging operation including one of bringing an offline chiller online, taking an online chiller offline, or both bringing the offline chiller online and taking the online chiller offline; and   if the estimated efficiency of the chiller group is higher than the current efficiency, staging the chiller group according to the staging operation.   
     
     
         2 . The method of  claim 1 , further comprising:
 generating a performance curve for each chiller, each performance curve defining a relationship between a thermal transfer rate of the chiller and a power consumption of the chiller.   
     
     
         3 . The method of  claim 2 , wherein generating the performance curve comprises:
 determining the power consumption of the chiller at each of a plurality of thermal transfer rates;   determining a ratio of the power consumption and the thermal transfer rate of the chiller at each thermal transfer rate based the power consumption at the thermal transfer rate; and   generating a polynomial equation based on the ratio at each thermal transfer rate that defines the performance curve.   
     
     
         4 . The method of  claim 3 , wherein the ratio is of the amount of power being consumed by the chiller divided by the thermal transfer rate of the chiller. 
     
     
         5 . The method of  claim 3 , wherein the performance curve is generated for each of a plurality of operating conditions. 
     
     
         6 . The method of  claim 2 , wherein the staging operation is bringing the offline chiller online, and determining the estimated efficiency of the chiller group for the staging operation comprises:
 distributing the thermal load between the offline chiller being brought online, and one or more online chillers;   estimating an efficiency of each chiller carrying at least a portion of the thermal load based on the performance curve of the respective chiller; and   determining a weighted average of the estimated efficiency of each chiller to generate the estimated efficiency of the chiller group.   
     
     
         7 . The method of  claim 2 , wherein the staging operation is taking the online chiller offline, and determining the estimated efficiency of the chiller group for the staging operation comprises:
 distributing the thermal load carried by the chiller being taken offline between one or more remaining online chillers;   estimating an efficiency of each of the one or more remaining online chillers based on the performance curve of the respective chiller; and   determining a weighted average of the estimated efficiencies of each of the one or more remaining online chillers to generate the estimated efficiency of the chiller group.   
     
     
         8 . The method of  claim 2 , wherein the staging operation includes both bringing the offline chiller online and taking the online chiller offline, and determining the estimated efficiency of the chiller group for the staging operation comprises:
 distributing the thermal load from the chiller being taken offline to the chiller being brought online;   estimating an efficiency of each remaining online chiller and the chiller being brought online based on the performance curve of the respective chiller; and   determining a weighted average of the estimated efficiencies of the chillers to generate the estimated efficiency of the chiller group.   
     
     
         9 . The method of  claim 2 , further comprising:
 monitoring one or more operating conditions of each chiller; and   storing the one or more operating conditions in a database,   wherein the performance curve is generated based on the one or more operating conditions.   
     
     
         10 . The method of  claim 9 , wherein the one or more operating conditions include one or more of an incoming working fluid temperature, an outgoing working fluid temperature, a flow rate of the working fluid through the chiller, an incoming coolant temperature, an outgoing coolant temperature, a flow rate of the coolant through the chiller, an amount of electrical power being drawn by the chiller, a lift of the chiller, an ambient temperature, and an ambient humidity. 
     
     
         11 . A system comprising:
 a chiller group including a plurality of chillers;   one or more processors operatively coupled to the plurality of chillers; and   a memory coupled to the one or more processors and including program code that, when executed by the one or more processors, causes the system to:   determine a thermal load on the chiller group;   determine a current efficiency of the chiller group;   determine an estimated efficiency of the chiller group after executing a staging operation including one of bringing an offline chiller online, taking an online chiller offline, or both bringing the offline chiller online and taking the online chiller offline; and   if the estimated efficiency of the chiller group is higher than the current efficiency of the chiller group, stage the chiller group according to the staging operation.   
     
     
         12 . The system of  claim 11 , wherein the program code further causes the system to:
 generate a performance curve for each chiller, each performance curve defining a relationship between a thermal transfer rate of the chiller and a power consumption of the chiller.   
     
     
         13 . The system of  claim 12 , wherein the program code further causes the system to generate the performance curve by:
 determining the power consumption of the chiller at each of a plurality of thermal transfer rates;   determining a ratio of the power consumption and the thermal transfer rate of the chiller at each thermal transfer rate based the power consumption at the thermal transfer rate; and   generating a polynomial equation based on the ratio at each thermal transfer rate that defines the performance curve.   
     
     
         14 . The system of  claim 13 , wherein the program code causes the system to generate the performance curve for each of a plurality of operating conditions. 
     
     
         15 . The system of  claim 12 , wherein the staging operation is bringing the offline chiller online, and the program code causes the system to determine the estimated efficiency of the chiller group for the staging operation by:
 distributing the thermal load between the offline chiller being brought online, and one or more online chillers;   estimating an efficiency of each chiller carrying at least a portion of the thermal load based on the performance curve of the respective chiller; and   determining a weighted average of the estimated efficiency of each chiller to generate the estimated efficiency of the chiller group.   
     
     
         16 . The system of  claim 12 , wherein the staging operation is taking the online chiller offline, and the program code causes the system to determine the estimated efficiency of the chiller group for the staging operation by:
 distributing the thermal load carried by the chiller being taken offline between one or more remaining online chillers;   estimating an efficiency of each of the one or more remaining online chillers based on the performance curve of the respective chiller; and   determining a weighted average of the estimated efficiencies of each of the one or more remaining online chillers to generate the estimated efficiency of the chiller group.   
     
     
         17 . The system of  claim 12 , wherein the staging operation includes both bringing the offline chiller online and taking the online chiller offline, and the program code causes the system to determine the estimated efficiency of the chiller group for the staging operation by:
 distributing the thermal load from the chiller being taken offline to the chiller being brought online;   estimating an efficiency of each remaining online chiller and the chiller being brought online based on the performance curve of the respective chiller; and   determining a weighted average of the estimated efficiencies of the chillers to generate the estimated efficiency of the chiller group.   
     
     
         18 . The system of  claim 12 , wherein the program code further causes the system to:
 monitor one or more operating conditions of each chiller; and   store the one or more operating conditions in a database,   wherein the performance curve is generated based on the one or more operating conditions.   
     
     
         19 . The system of  claim 18 , wherein the one or more operating conditions include one or more of an incoming working fluid temperature, an outgoing working fluid temperature, a flow rate of the working fluid through the chiller, an incoming coolant temperature, an outgoing coolant temperature, a flow rate of the coolant through the chiller, an amount of electrical power being drawn by the chiller, a lift of the chiller, an ambient temperature, and an ambient humidity. 
     
     
         20 . A computer program product comprising:
 a non-transitory computer-readable storage medium; and   program code stored on the non-transitory computer-readable storage medium that, when executed by one or more processors, causes the one or more processors to:   determine a thermal load on the chiller group;   determine a current efficiency of the chiller group;   determine an estimated efficiency of the chiller group after executing a staging operation including one of bringing an offline chiller online, taking an online chiller offline, or both bringing the offline chiller online and taking the online chiller offline; and   if the estimated efficiency of the chiller group is higher than the current efficiency of the chiller group, stage the chiller group according to the staging operation.