Systems and methods for reducing energy consumption of a chilled water distribution system

• US 10,415,869 B2
• Filed: 08/21/2017
• Issued: 09/17/2019
• Est. Priority Date: 11/17/2011
• Status: Active Grant

• Current Assignee: Optimum Energy LLC
• Original Assignee: Optimum Energy LLC
• Inventors: Erpelding, Ben, Dempster, Ian
• Primary Examiner(s): Vazquez, Ana M
• Application Number:
  US15/682,320
• Publication Number:
  US 20170343267A1
• Time in Patent Office: 757 Days
• Field of Search: 622591
• CPC Class Codes: F24F 11/85 using variable-flow pumps
• CPC Class Codes: F25B 2400/06 Several compression cycles arranged in parallel
• CPC Class Codes: F25B 25/005 using primary and secondary systems
• CPC Class Codes: F25B 2600/13 Pump speed control
• CPC Class Codes: F25B 49/02 for compression type machines, plants or systems
• CPC Class Codes: F25D 17/02 for circulating liquids, e.g. brine
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

A chilled water distribution system includes a chilled water loop in fluid communication with a plurality of buildings and also in fluid communication with a plurality of chiller stations. A monitoring and control system communicates with one of the chiller stations, hereinafter referred to as a “controlled” chiller station because it is configured with one or more variable frequency drives that are controlled by the monitoring and control system to modulate the speed of at least one chiller station component such as, but not limited to, a pump or a fan. By way of this modulation process, a differential pressure of the chilled water loop may be maintained at a desired level so as to optimize chiller station output while minimizing chiller station energy consumption.

Claims

1. A distributed process chilled water system comprising:

a supply line having a plurality of supply line pressure sensors;

a return line having a plurality of return line pressure sensors, the return line and the supply line forming a chilled water loop, the supply line pressure sensors and the return line pressure sensors configured to provide a plurality of readings of differential pressures throughout the chilled water loop, each differential pressure reading of the plurality being associated with a respective location within the chilled water loop;

a plurality of chiller stations comprising at least one base chiller station, each chiller station in fluid communication with the return and supply lines, the chiller stations communicatively networked together, each building of a plurality of buildings having a building automation system controller, each building in fluid communication with the return and supply lines, each building having associated therewith a respective pre-determined minimum pressure set point, the controllers communicatively networked together; and

an operating system operable to process machine-readable instructions, the operating system in signal communication with at least the base chiller station, the operating system configured to receive signals indicative of the differential pressure readings throughout the chilled water loop and determine, based on the respective pre-determined minimum pressure set points, which of the differential pressures read by the sensors operates as a controlling differential pressure for the chilled water system, the operating system further configured, based on the controlling differential pressure, to determine whether to modulate a pump speed of the base chiller station, bring another chiller online or take another chiller offline to maintain the controlling differential pressure within a desired range.

2. The system of claim 1, wherein the base chiller station includes at least one chilled water pump coupled to a variable frequency drive.

3. The system of claim 1, wherein the operating system modulates the pump speed of the base chiller station by communicating instructions to the variable speed drive.

4. The system of claim 1, wherein the base chiller station includes at least one chiller unit operable to supply and receive water from at least one cooling tower.

5. The system of claim 1, wherein the operating system includes one or more relational control algorithms for determining whether to modulate the pump speed of the base chiller station.

6. The system of claim 1, wherein the operating system determines to bring another chiller online when an actual differential pressure exceeds a maximum set point pressure.

7. The system of claim 1, wherein the operating system determines to take another chiller offline when an actual differential pressure falls below a minimum set point pressure.

8. A method for controlling a chilled water distribution system, the method comprising:

determining a plurality of readings of real-time differential pressures at various locations within a chilled water loop of the distribution system;

monitoring a real-time pump speed of a base chiller station that includes a variable frequency drive coupled to a chilled water pump;

determining an energy load for a plurality of buildings served by the chilled water loop, each building having associated therewith a respective pre-determined minimum pressure set point;

modulating the pump speed of the base chiller station to stay within a desired range of pre-determined set point differential pressures of the chilled water loop; and

determining, based on a comparison between the respective pre-determined minimum pressure set points and the differential pressure readings, which of the real-time differential pressures to use as a single controlling differential pressure to decide whether to change the capacity of the distribution system by bringing a chiller either online or offline.

9. The method of claim 8, further comprising calculating a desired pump speed for at least one other chiller station based on the real-time differential pressure, real-time pump speed and energy load for the plurality of buildings.

10. The method of claim 8, wherein modulating the pump speed of the base chiller station coincides with bringing a chiller of another chiller station either online or offline.

11. The method of claim 8, wherein modulating the pump speed of the base chiller station include providing instructions to a variable speed drive coupled to the chilled water pump.

12. The method of claim 8, wherein modulating the pump speed of the base chiller station to stay within the desired range includes maintaining an output capacity of the base chiller station within a desired range, wherein said desired range comprises the range between a minimum set point and a maximum set point of said differential pressures in said chilled water loop.