CONTROL OF COOLING TOWERS FOR CHILLED FLUID SYSTEMS

• US 20110276182A1
• Filed: 05/10/2010
• Published: 11/10/2011
• Est. Priority Date: 05/10/2010
• Status: Active Grant

• Current Assignee: Tyco Fire & Security GmbH (Johnson Controls International plc)
• Original Assignee: Johnson Controls Technology Company (Johnson Controls International plc)
• Inventors: Seem, John E., Li, Yaoyu
• Granted Patent: US 8,473,080 B2
• Time in Patent Office: Days
• US Class Current: 700/276
• CPC Class Codes: F25B 2600/11 Fan speed control
• CPC Class Codes: F25B 49/027 Condenser control arrangements
• CPC Class Codes: G05B 13/021 in which a variable is automatically adjusted to optimise the performance

Abstract

A system for controlling a cooling tower that cools condenser fluid for a condenser of a chiller includes a cooling tower fan system that controllably varies a speed of at least one fan motor. The system further includes an extremum seeking controller that receives inputs of power expended by the cooling tower fan system and of power expended by the chiller. The extremum seeking controller provides an output to the cooling tower fan system that controls the speed of the at least one fan motor. The extremum seeking controller determines the output by searching for a speed of the at least one fan motor that minimizes the sum of the power expended by the cooling tower fan system and the power expended by the chiller.

Claims

1. A system for controlling a cooling tower that cools condenser fluid for a condenser of a chiller, comprising:

a cooling tower fan system that controllably varies a speed of at least one fan motor; and

an extremum seeking controller that receives inputs of power expended by the cooling tower fan system and of power expended by the chiller;

wherein the extremum seeking controller provides an output to the cooling tower fan system that controls the speed of the at least one fan motor;

wherein the extremum seeking controller determines the output by searching for a speed of the at least one fan motor that minimizes the sum of the power expended by the cooling tower fan system and the power expended by the chiller.

2. The system of claim 1, wherein the extremum seeking controller does not utilize temperature of the condenser fluid as an input.

3. The system of claim 1, wherein the extremum seeking controller is the only controller that controllably varies the speed of the at least one fan motor.

4. The system of claim 1, wherein the extremum seeking controller uses only the inputs of the power expended by the cooling tower fan system and the power expended by the condenser to determine the control signal.

5. A method for controlling a cooling tower that cools condenser fluid for a condenser of a chiller, comprising:

receiving, at an extremum seeking controller, an input of power expended by a cooling tower fan system;

receiving, at an extremum seeking controller, an input of power expended by the chiller; and

determining, using the extremum seeking controller and the inputs of power expended by the cooling tower fan system and the power expended by the chiller, a control signal representative of the speed of at least one fan motor for the cooling tower fan system.

6. The method of claim 5, wherein the determining step comprises searching for a speed of the at least one fan motor that minimizes the sum of the power expended by the cooling tower fan system and the power expended by the condenser.

7. The method of claim 6, wherein the extremum seeking controller does not utilize temperature of the condenser fluid as an input.

8. The method of claim 7, wherein the extremum seeking controller is the only controller that controllably varies the speed of the at least one fan motor.

9. The method of claim 5, wherein the extremum seeking controller uses only the inputs of the power expended by the cooling tower fan system and the power expended by the condenser to determine the control signal.

10. The method of claim 5, wherein the inputs are at least one of summed and combined prior to use by the extremum seeking controller.

11. A device for controlling a cooling system having a cooling tower that cools condenser fluid for a chiller, comprising:

an extremum seeking control module configured to seek a fan speed for the cooling tower that minimizes the power demand of the cooling system; and

an output interface for outputting the fan speed for the cooling tower to the cooling system.

12. The device of claim 11, further comprising a processor and a memory device, wherein the extremum seeking control module is stored in the memory device and executable by the processor.

13. The device of claim 11, wherein the device is at least one of a chiller controller, a cooling tower controller, a building management system controller, and a special purpose controller external a cooling tower controller and a chiller controller.

14. The device of claim 11, wherein the cooling tower is a part of a cooling tower array and the fan speed provided to the cooling tower is also provided to the other cooling towards of the cooling tower array.

15. The device of claim 11, wherein the cooling tower is a part of a cooling tower array and the fan speed is provided to a fan array controller configured to control the individual cooling towers of the cooling tower array.

16. The device of claim 11, wherein the device further includes a module for summing the power demand of the cooling tower and the power demand of the chiller and wherein the extremum seeking control module seeks the fan speed for the cooling tower based on the resulting sum.

17. The device of claim 11, wherein the device further includes a module for summing the power demand for the cooling tower, the power demand of the chiller, and the power demand of a condenser fluid pumping system;

and wherein the extremum seeking control module seeks the fan speed for the cooling tower based on the resulting sum.

18. The device of claim 17, wherein the extremum seeking control module is further configured to seek a speed for the condenser fluid pumping system that reduces the sum.

19. The device of claim 11, wherein the extremum seeking control module comprises a fan speed limiter configured to place an upper and lower limit on the fan speed output by the output interface.

20. The device of claim 19, wherein an output from the limiter is provided to a saturation control module for the extremum seeking control module.