Method for operating variable speed heat pumps and air conditioners

• US 4,873,649 A
• Filed: 06/10/1988
• Issued: 10/10/1989
• Est. Priority Date: 06/10/1988
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: MacArthur, J. Ward, Grald, Eric W.
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US07/206,052
• Time in Patent Office: 487 Days
• Field of Search: 364/552, 364/413.3, 364/505, 62/129, 62/209, 62/215, 62/229, 62/176.1, 62/176.3, 62/176.6, 62/126, 237/2 B, 73/189
• US Class Current: 700/276
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/46 Improving electric energy efficiency or saving
• CPC Class Codes: F24F 11/63 Electronic processing
• CPC Class Codes: F24F 11/77 by controlling the speed of ventilators
• CPC Class Codes: F24F 11/86 by controlling compressors within refrigeration or heat pump circuits
• CPC Class Codes: F24F 2110/10 Temperature
• CPC Class Codes: F24F 2110/20 Humidity
• CPC Class Codes: F24F 2110/30 Velocity
• CPC Class Codes: F24F 2110/50 Air quality properties
• CPC Class Codes: F24F 2110/70 Carbon dioxide
• CPC Class Codes: F25B 2600/0253 with variable speed
• CPC Class Codes: F25B 2600/112 of evaporator fans
• CPC Class Codes: F25B 49/02 for compression type machines, plants or systems
• CPC Class Codes: G05D 23/1917 using digital means
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

A controller and a related method that maintains thermal comfort in an occupied space at a user-defined level while simultaneously maximizing the efficiency of the space conditioning equipment. The controller determines the setting of heating/cooling capacity, indoor airflow rate, evaporator superheat and other system parameters such that a comfort constraint is satisfied. The comfort index may be any arbitrarily-defined relationship of measured or inferred quantities such as air temperature, relative humidity, air velocity, mean radiant temperature, CO₂ concentration, etc. The controller ensures that the error between comfort index and the comfort setpoint is zero while the energy consumed by the space conditioning equipment is minimized.

Claims

1. A method for operating a system having variable speed equipment such as heat pumps and air conditioners while (1) achieving optimal comfort conditions in an air conditioned space and (2) maximizing the coefficient of performance (COP) of said equipment;

said equipment being characterized by having controls for varying equipment parameters thereof including compressor speed (r), indoor air flow rate (c), and evaporator superheat (t);

said system having multiple sensory inputs from which variable comfort influencing data parameters transmitted from said space to said equipment includes dry-bulb temperature (T), humidity ratio (w) and air velocity (V);

said method comprising the steps of;

providing a nonlinear measure of comfort function CI (T,w,V) based on said data parameters;

setting one of said data parameters and calculating default values for the other of said data parameters;

calculating a set point value for said comfort function;

expressing said function CI (T,w,V) in terms of said equipment parameters as a function of IC (r,c,t);

calculating a comfort error (CE) value which is set point value of CI (T,w,V) minus said CI (r,c,t);

selecting a nonlinear coefficient of performance function PE (r,c,t) based on said equipment parameters which is desired to be maximized and which is based on the same variables as said CI (r,c,t); and

setting said controls to effect maximizing said PE (r,c,t) function while maintaining said (CE) value at substantially a zero value.

2. A method according to claim 1 wherein said maximizing is effected by relating said functions through a performance index (H) wherein

3. A method as set forth in claim 1 wherein said variable comfort influencing data parameters include CO₂ concentration, particulates and other air contaminants.

4. A method as set forth in claim 1 wherein said dry-bulb temperature (T) is set.

5. A method as set forth in claim 1 wherein said other of said data parameters are initially adjustable to provide a bias thereon.

6. A method for operating a system having variable speed equipment such as heat pumps and air conditioners while (1) achieving optimal comfort conditions in an air conditioned space and (2) maximizing the coefficient of performance (COP) of said equipment;

said equipment being characterized by having controls for varying parameters thereof;

said system having multiple sensory inputs from which variable comfort influencing data parameters are transmitted from said space to said equipment;

said method comprising the steps of;

providing a nonlinear measure of comfort function CI (data) based on said data parameters;

setting one of said data parameters and calculating default values for the other of said parameters;

calculating a set point value for said comfort function CI (data);

expressing said comfort function CI (data) in terms of said equipment parameters as a comfort function CI (manipulated control variables);

calculating a comfort error (CE) value which is said set point value of said CI (data) minus said CI (manipulated control variables);

selecting a nonlinear performance function PE (manipulated control variables) based on said equipment parameters which is desired to be maximized and which is based on the same variables as said CI (manipulated control variables); and

setting said controls to effect maximizing said PE (manipulated control variables) function while maintaining said (CE) value at substantially a zero value.

7. A method according to claim 6 wherein said maximizing is effected by relating said functions CI (data) and CI (manipulated control variables) through a performance index (H) wherein

8. A method according to claim 6 wherein said comfort error (CE) and said set point value are continuously updated.

9. A method for operating a system having variable speed equipment such as heat pumps and air conditioners while (1) achieving optimal comfort conditions in an air conditioned space and (2) maximizing the coefficient of performance (COP) of said equipment;

said equipment being characterized by having controls for varying equipment parameters thereof including compressor speed (r), indoor air flow rate (c), and evaporator superheat (t);

said system having multiple sensory inputs from which variable comfort influencing data parameters transmitted from said space to said equipment includes dry-bulb temperature (T), humidity ratio (W) and air velocity (V);

said method comprising the steps of;

providing a nonlinear measure of comfort feature CI (T,w,V) based on said data parameters;

setting one of said data parameters and calculating default values for the other of said data parameters;

calculating a set point value for said comfort function;

expressing said function CI (T,w,V) in terms of said equipment parameters as a function of CI (r,c,t);

calculating a comfort error (CE) value which is said set point value of CI (T,w,V) minus said CI (r,c,t);

selecting a nonlinear coefficient of performance function PE (r,c,t) based on said equipment parameters which is desired to be maximized and which is based on the same variables as said CI (r,c,t);

representing said PE function as a performance index L(x,u) and representing said CE function as a constraint function f(x,u);

setting said controls to effect maximizing said PE (r,c,t) function while maintaining said (CE) value at substantially a zero value, said maximizing being effected by relating said functions through a performance index (H) wherein H=L(x,u)+λ

^T ·

f(x,u) with said λ

^T being a Lagrangian multiplier, and x being state parameters and said u being a decision vector; and

finding values of said decision vector at a stationary value of said L(x,u) wherein dL=0 for arbitrary du while holding df=0.

10. A method for operating a space conditioning system having equipment characterized by variable operating parameters which both (1) achieves desired comfort conditions in the conditioned space and (2) maximizes the performance efficiency of said equipment, said equipment being characterized by controls for varying operating parameters thereof, said system having multiple sensory inputs from which a plurality of actual time-variable comfort influencing data parameter values are transmitted from said conditioned space to said equipment on a real-time basis, said system also having user-determined desired data parameter values;

said method comprising the steps of;

calculating a desired comfort index set point based on said user determined desired data parameter values;

calculating an actual comfort index value based on said actual time-variable comfort influencing data parameter values;

calculating an equipment performance function based on said variable operating parameters and said desired comfort index set point; and

adjusting said variable operating parameters of said equipment so as to maximize said equipment performance function while attempting to maintain said desired comfort index set point.