Model predictive control for heat transfer to fluids

• US 10,378,805 B2
• Filed: 03/09/2015
• Issued: 08/13/2019
• Est. Priority Date: 03/07/2014
• Status: Active Grant

• Current Assignee: Alliance For Sustainable Energy LLC
• Original Assignee: Alliance For Sustainable Energy LLC
• Inventors: Jin, Xin, Maguire, Jeff, Christensen, Dane
• Primary Examiner(s): Atkisson, Jianying C
• Assistant Examiner(s): Shaikh, Meraj A
• Application Number:
  US14/642,581
• Publication Number:
  US 20150253051A1
• Time in Patent Office: 1,618 Days
• CPC Class Codes: F24D 19/1054 the system uses a heat pump
• CPC Class Codes: F24D 19/1063 counting of energy consumption
• CPC Class Codes: F25B 2500/19 Calculation of parameters
• CPC Class Codes: F25B 49/02 for compression type machines, plants or systems

Abstract

Model predictive control methods are disclosed which provide, among other things, efficient strategies for controlling heat-transfer to a fluid.

Claims

1. A method for controlling a temperature of a fluid, the method comprising:

an minimizing energy required to heat the fluid, wherein the method includes a model predictive controller configured to achieve the minimizing using a objective function defined by

R^opt∝

C_rate[P₁(R(i))+P₂(R(i))], wherein;

R^opt is an optimized fluid temperature set-point,

P₁ is the first power consumed by a first heating element to achieve a fluid temperature set-point (R(i)),

P₂ is the second power consumed by a second heating element to achieve the fluid temperature set-point (R(i)), and

C_rate is an electricity rate;

changing the fluid temperature set-point; and

heating the fluid utilizing the first heating element and the second heating element to the optimized fluid temperature set-point;

solving the objective function for the optimized fluid temperature set-point with the changed fluid temperature set-point;

repeating the changing and the solving until the minimizing is achieved;

adjusting at least one of the first power consumed by a first heating element or the second power consumed by a second heating element so that the fluid attains the optimized fluid temperature set-point; and

heating the fluid utilizing the first heating element and the second heating element to the optimized fluid temperature set-point.

2. The method of claim 1, wherein the objective function is also a function of a future fluid usage prediction, and the future fluid prediction is at least partially determined by historical fluid usage data.

3. The method of claim 2, wherein the historical fluid usage data are determined by

defining a first time period (T);

defining a second time period (t) by dividing T by an integer value (N) such that T is divided into N equal and consecutive time intervals (t_n), wherein T restarts and repeats upon completion of the last t_n; and

collecting consecutive measurements of actual fluid usage data (F_n) for each consecutive t_n as the historical usage data.

4. The method of claim 3, further comprising storing on a data storage medium no more than N sets of consecutive measurements.

5. The method of claim 4, wherein the historical fluid usage data comprises a measurement of least one of a fluid flow or a fluid temperature.

6. The method of claim 1, wherein the first heating element and the second heating element comprise at least one of a resistive heating element or a heat pump.

7. The method of claim 1, wherein the fluid is a liquid.

8. The method of claim 7, wherein the liquid is water.

9. The method of claim 1, wherein the optimized fluid temperature set-point ranges from about 0°

F. to about 500°

F.

10. A method for controlling a temperature of water utilizing a resistive heating element and a heat pump, the method comprising:

minimizing the sum of the first power consumed by a heat pump and a second power consumed by a resistive heating element, wherein the minimizing is achieved using an objective function defined by

R^opt∝

C_rate[P_hp(R(i))+P_elec(R(i))], wherein;

R^opt is an optimized water temperature set-point for the water,

P₁ is the first power consumed by a heat pump to achieve a water temperature set-point (R(i)),

P₂ is the second power consumed by a resistive heating element to achieve the water temperature set-point (R(i)), and

C_rate is an electricity rate;

changing the water temperature set-point;

solving the objective function for the optimized water temperature set-point with the changed water temperature set-point;

repeating the changing and the solving until the minimization is achieved; and

adjusting at least one of the resistive heating element or the heat pump to heat the water to the optimized water temperature set-point.

11. The method of claim 10, wherein the objective function is also a function of a future water volume usage prediction, and the future water volume usage prediction is at least partially determined by historical water volume usage data.

12. The method of claim 11, wherein the historical water usage data are determined by defining a first time period;

defining a second time period by dividing the first time period by an integer (N);

defining a third time period by dividing the second time period by an integer (I) to create N*I consecutive time intervals, wherein each time interval is about equal to the third time period; and

collecting consecutive measurements of actual water flow and water temperature data for each consecutive time interval as the historical usage data.

13. The method of claim 12, wherein the first time period equals about 14 days, the second time period equals about 1 day for an N of about 14, and the third time period is about 30 minutes for an I of about 48.