Device and method for optimization of chilled water plant system operation

• US 8,774,978 B2
• Filed: 05/31/2011
• Issued: 07/08/2014
• Est. Priority Date: 07/23/2009
• Status: Active Grant

• Current Assignee: Siemens Industry Incorporated (Siemens AG)
• Original Assignee: Siemens Industry Incorporated (Siemens AG)
• Inventors: Higgins, Robert, McMasters, Brendan
• Primary Examiner(s): Ali, Mohammad
• Assistant Examiner(s): Karim, Ziaul
• Application Number:
  US13/149,563
• Publication Number:
  US 20110301766A1
• Time in Patent Office: 1,134 Days
• Field of Search: 700/282, 700/295
• US Class Current: 700/295
• CPC Class Codes: F24F 11/83 by controlling the supply of heat-exchange fluids to heat-exchangers
• CPC Class Codes: F24F 11/85 using variable-flow pumps
• CPC Class Codes: F24F 2140/12 Heat-exchange fluid pressure
• CPC Class Codes: F24F 3/06 characterised by the arrangements for the supply of heat-exchange fluid for the subsequent treatment of primary air in the room units
• CPC Class Codes: G06Q 10/06 Resources, workflows, human or project management; Enterprise or organisation planning; Enterprise or organisation modelling
• CPC Class Codes: G06Q 50/06 Energy or water supply
• CPC Class Codes: G06Q 50/08 Construction
• CPC Class Codes: G06Q 50/12 Hotels or restaurants

Abstract

A demand flow device configured to interface with a chilled water plant controller to optimize performance of one or more chilled water plant components over a range of demand conditions is disclosed. The demand flow device includes a communication device configured to receive sensor data associated with the one or more chilled water plant components, wherein the sensor data measures operational variables of the chilled water plant. The demand flow device further includes a demand flow controller in communication with the communication device. The demand flow controller is configured to utilize the received sensor data to: determine an optimal pressure setpoint as a function of a desired chilled water delta T; control a chilled water flow rate through the one or more chiller water plant components as a function of the optimal pressure setpoint and the desired chilled water delta T; and adjust, via the chilled water plant controller, the optimal pressure setpoint, in response to one or more detected triggering events, to perform a critical zone reset of the desired chilled water delta T.

Claims

1. A demand flow device configured to interface with an existing chilled water plant controller to manage performance of one of a plurality of chilled water plant subsystems with respect to remaining subsystems of the plurality of chilled water plant subsystems over a range of load conditions, the demand flow device comprising:

a communication device configured to receive sensor data associated with the one of the chilled water plant subsystems, wherein the sensor data measures operational variables of the chilled water plant;

a demand flow controller in communication with the communication device, the demand flow controller configured to utilize the received sensor data to;

determine an optimal pressure setpoint as a function of a chilled water delta T,

control a chilled water flow rate through the one of the chilled water plant subsystems as a function of the optimal pressure setpoint and the chilled water delta T; and

adjust, via the chilled water plant controller, the optimal pressure setpoint, in response to one or more detected triggering events, to perform a critical zone reset of the chilled water delta T, wherein the optimal pressure setpoint is determined as a function of a measured pressure differential, a ratio of a measured delta T to a design delta T and a site-specific exponent.

2. The demand flow device of claim 1, wherein the chilled water delta T is a function of a measured chilled water entrance temperature and a measured chilled water exit temperature sensed at one or more components of the chilled water plant.

3. The demand flow device of claim 1, wherein the function, with the measured delta T expressed as Measured Δ

T, the design delta T expressed as Design Δ

T, the measured pressure differential expressed as Measured Δ

P, and P Exponent is a pressure exponent, is defined as;

Pressure setpoit=Measured Δ

P*(Measured Δ

T/Design Δ

T)^P Exponent.

4. The demand flow device of claim 1, wherein the optimal pressure setpoint controls a flow rate provided by a circulatory pump associated with the one of the subsystems of the chilled water plant.

5. The demand flow device of claim 4, wherein the flow rate is determined to maintain the chilled water delta T across the one of the subsystems of the chilled water plant.

6. The demand flow device of claim 1, wherein the critical zone reset adjusts the optimal pressure setpoint to correspond to a different chilled water delta T.

7. The demand flow device of claim 1, wherein the one of the subsystems of the chilled water plant is selected from the group consisting of:

an evaporator;

a condenser;

a compressor and a chilled water pump.

8. The demand flow device of claim 7, wherein the optimal pressure setpoint represents an optimal component pressure setpoint for the one of the subsystems of the chilled water plant.

9. The demand flow device of claim 7, wherein the chilled water pump comprises multiple chilled water pumps in operation throughout the chilled water plant.

25. The demand flow device of claim 1 wherein the demand flow controller is configured to identify a pre-determined chilled water Delta T and setting a chilled water Delta T based on the pre-determined chilled water Delta T, the chilled water Delta T comprising a chilled water entering temperature and a chilled water leaving temperature at one or more components of the chilled water plant and wherein the demand flow controller is configured to control the chilled water flow rate to maintain the chilled water Delta T across the one or more components of the chilled water plant.

10. A demand flow control system for the implementation of variable pressure control logic in an existing chilled water plant controller to synchronize the performance of one or more chilled water plant components over a range of demand conditions, the demand flow control system comprising:

a demand flow controller in communication with the existing chilled water plant controller, the demand flow controller configured to;

receive sensor data from one or more chilled water plant components coupled to the existing chilled water plan controller;

determine an optimal pressure setpoint as a function of a desired chilled water delta T and the received sensor data for each of the one or more chilled water plan components, wherein the optimal pressure setpoint is determined iteratively for each of the one or more chilled water plant components;

communicate the optimal pressure setpoint to the existing chilled water plant controller; and

control, via the existing chilled water plant controller, a chilled water flow rate through each of the one or more chilled water plant components as a function of the optimal pressure setpoint and the desired chilled water delta T;

wherein the optimal pressure setpoint is determined as a function of a measured pressure differential, a ratio of a measured delta T to a design delta T and a site-specific exponent.

11. The demand flow control system of claim 10, wherein the demand flow controller is further configured to:

adjust the optimal pressure setpoint, in response to one or more detected triggering events, to perform a critical zone reset of the desired chilled water delta T.

12. The demand flow control system of claim 11, wherein the triggering event is selected from the group consisting of:

opening of a chilled water valve;

a change in a sensed chilled water temperature;

a change in flow rate of a pump; and

a change in a humidity level within a sensed space.

13. The demand flow control system of claim 11, wherein the critical zone reset adjusts the optimal pressure setpoint to correspond to a different desired chilled water delta T.

14. The demand flow control system of claim 10, wherein the desired chilled water delta T is evaluated with respect to a measured chilled water entrance temperature and a measured chilled water exit temperature sensed at one or more components of the chilled water plant.

15. The demand flow control system of claim 10, wherein the desired chilled water delta T at the one or more chilled water plant components is maintained by:

increasing the optimal pressure setpoint and consequentially the chilled water flow rate to reduce a sensed chilled water delta T with respect to the desired chilled water delta T; and

decreasing the optimal pressure setpoint and consequently the chilled water flow rate to increase the sensed chilled water delta T with respect to the desired chilled water delta T.

16. The demand flow control system of claim 10, wherein the one or more components of the chilled water plant are selected from the group consisting of:

an evaporator;

a condenser;

a compressor and a chilled water pump.

17. The demand flow control system of claim 16, wherein the optimal pressure setpoint represents an optimal component pressure setpoint for each of the one or more components of the chilled water plant.

18. A method of demand flow control utilizing variable pressure control logic to manage the performance of one or more chilled water plant components over a range of demand conditions operable in an existing chilled water plant, the method of demand flow control comprising:

sensing a chilled water entrance temperature and a chilled water exit

temperature at one or more components of the chilled water plant;

communicating the sensed chilled water entrance temperature and the

sensed chilled water exit temperature to a demand flow controller;

calculating an optimal pressure setpoint at the demand flow controller,

wherein the optimal pressure setpoint is calculated as a function of a desired chilled water delta T and the sensed chilled water entrance temperature and the sensed chilled water exit temperature to a demand flow controller;

communicating the optimal pressure setpoint to an existing chilled water plant

controller; and

controlling a chilled water flow rate through the one or more components of the chilled water plant as a function of the communicated optimal pressure setpoint;

wherein the optimal pressure setpoint is determined as a function of a measured pressure differential, a ratio of a measured delta T to a design delta T and a site-specific exponent.

19. The method of demand flow control of claim 18, wherein calculating the optimal pressure setpoint is a function of a design characteristic of the one or more components of the chilled water plant.

20. The method of demand flow control of claim 18, wherein sensing the chilled water entrance temperature and the chilled water exit temperature further comprises sensing a chilled water flow rate through one or more components of the chilled water plant.

21. The method of demand flow control of claim 18 further comprising:

iteratively calculating the optimal pressure setpoint for each of the one or more chilled water plant components.

22. The method of demand flow control of claim 18, wherein controlling the chilled water flow rate further comprises:

increasing the optimal pressure setpoint and consequentially the chilled water flow rate to reduce a sensed chilled water delta T with respect to the desired chilled water delta T; and

decreasing the optimal pressure setpoint and consequently the chilled water flow rate to increase the sensed chilled water delta T with respect to the desired chilled water delta T.

23. The method of demand flow control of claim 18 further comprising:

adjusting the optimal pressure setpoint, in response to one or more detected triggering events, to perform a critical zone reset of the desired chilled water delta T.

24. The method of demand flow control of claim 23, wherein the triggering event is selected from the group consisting of:

opening of a chilled water valve;

detecting a change in a sensed chilled water temperature;

detecting a change in flow rate of a pump; and

detecting a change in a humidity level within a sensed space.