Air conditioning plant and control method thereof

• US 20040011066A1
• Filed: 12/19/2002
• Published: 01/22/2004
• Est. Priority Date: 07/19/2002
• Status: Active Grant

• Current Assignee: Hitachi Plant Services Co., Ltd. (Hitachi, Ltd.)
• Original Assignee: Hitachi Plant Engineering & Construction Co., Ltd. (Hitachi, Ltd.)
• Inventors: Nakajima, Tadakatsu, Oshima, Noboru, Sugiura, Takumi, Kikuchi, Hiroshige, Sakai, Hiroo, Sugihara, Yoshibumi, Miyajima, Yuuji
• Granted Patent: US 6,732,540 B2
• Time in Patent Office: Days
• US Class Current: 62/177
• 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 11/47 Responding to energy costs
• CPC Class Codes: F24F 11/62 characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
• CPC Class Codes: F24F 2110/12 of the outside air

Abstract

Provided are an air conditioning plant control method by which an air conditioning plant can be operated in a most desirable state, and an air conditioning plant so controlled. An air conditioning plant is controlled, which has at least one air conditioner, a refrigerating machine supplying cold water to the air conditioner and a cooling tower supplying cooling water to the refrigerating machine. Within an extent satisfying set conditions of air conditioning, setpoints of the draft temperature of the at least one air conditioner, the cold water temperature of the refrigerating machine and the temperature of cooling water from the cooling tower are altered and optimized so as to minimize energy consumption, operating cost or carbon dioxide emission of the air conditioning plant.

Claims

1. A control method of an air conditioning plant comprising:

at least one air conditioner;

a low/high-temperature heat generator which supplies a low/high-temperature heat transfer medium to the at least one air conditioner; and

a heat source/sink which supplies a heat discharging/absorbing medium to the low/high-temperature heat generator,

wherein setpoints of at least draft temperature of the at least one air conditioner, low/high-temperature heat transfer medium temperature of the low/high-temperature heat generator and temperature of the heat discharging/absorbing medium from the heat source/sink are optimized so as to reduce at least one of energy consumption, operating cost and carbon dioxide emission of the air conditioning plant within extent of satisfying set conditions of air conditioning.

2. The control method as set forth in claim 1, wherein the setpoint of at least one of draft air flow rate of the air conditioner, low/high-temperature heat transfer medium flow rate of the low/high-temperature heat generator and flow rate of the heat discharging/absorbing medium from the heat source/sink is optimized in addition to the draft temperature of the at least one air conditioner, the low/high-temperature heat transfer medium temperature of the low/high-temperature heat generator and the temperature of the heat discharging/absorbing medium from the heat source/sink.

3. The control method as set forth in claim 1, wherein a data table showing a plurality of combinations of the conditions of the draft temperature of the at least one air conditioner, the low/high-temperature heat transfer medium temperature of the low/high-temperature heat generator and the temperature of the heat discharging/absorbing medium from the heat source/sink and the at least one of the energy consumption, the operating cost and the carbon dioxide emission of the air conditioning plant at the time is prepared in advance, and setpoints are altered by accessing the data table.

4. The control method as set forth in claim 1, wherein piping conditions of the at least one air conditioner, piping conditions of the low/high-temperature heat generator and piping conditions of the heat source/sink are enterable.

5. An air conditioning plant, comprising:

at least one air conditioner;

a low/high-temperature heat generator which supplies a low/high-temperature heat transfer medium to the at least one air conditioner; and

a heat source/sink which supplies a heat discharging/absorbing medium to the low/high-temperature heat generator,

wherein setpoints of at least draft temperature of the at least one air conditioner, low/high-temperature heat transfer medium temperature of the low/high-temperature heat generator and temperature of the heat discharging/absorbing medium from the heat source/sink are capable of being optimized so as to reduce at least one of energy consumption, operating cost and carbon dioxide emission of the air conditioning plant within extent of satisfying set conditions of air conditioning.

6. A control method of an air conditioning plant comprising:

at least one air conditioner;

at least one low/high-temperature heat generator which supplies a low/high-temperature heat transfer medium to the at least one air conditioner;

a heat source/sink which cools or heats the at least one low/high-temperature heat generators;

a low/high-temperature heat accumulator which stores the low/high-temperature heat transfer medium during a period of a low low/high-temperature heat load;

a heat transfer medium conveying unit such as a pump, a fan and a blower which connects the aforementioned devices;

a control unit which controls temperatures of heat generated by the aforementioned devices and/or flow rate of conveying the heat transfer medium;

a group of measuring instruments with which data representing the operating states of individual units including the temperature and the flow rate are measured;

a group of control units with which the operation of individual units is controlled; and

a central monitoring device which is linked by signal lines to the group of measuring instruments and the group of control units,

wherein the central monitoring device has, built into it, at least one of an air conditioning plant operation simulator which manages the operation of the whole air conditioning plant and an air conditioning plant operational data table;

computes on the basis of real time operational data picked up by the measuring instruments the optimal operating temperature and the optimal flow rate for the constituent units of the air conditioning plant and the optimal number of operating units of at least one of the low/high-temperature heat generator to minimize the energy consumption, operating cost or carbon dioxide emission equivalent or any indicator combining two or more of these factors of the whole air conditioning plant in predetermined ranges of conditions, including the temperature and humidity, of air conditioning, ranges of energy consumption conditions with respect to electric power, fuel, water and so forth, or various permissible areas of condition setting which satisfy the ranges of requirements set by combining these two sets of conditions in a prioritized manner; and

supplies those optimal values to the group of control units as control setpoints, and the control unit group generates control signals on the basis of the control setpoints, and supplies the control signals to the constituent units of the air conditioning plant or to the pertinent control units themselves to control at least two of the constituent units of the air conditioning plant at substantially the same time.

7. A control method of an air conditioning plant comprising:

at least one air conditioner;

at least one low/high-temperature heat generator which supplies a low/high-temperature heat transfer medium to the at least one air conditioner;

a heat source/sink which cools or heats the low/high-temperature heat generator;

a heat transfer medium conveying unit, such as a pump, a fan and a blower which connects the aforementioned devices;

a control unit which controls temperatures of heat generated by these devices and/or flow rate of conveying the heat transfer medium;

a group of measuring instruments with which data representing the operating states of individual units including the temperature and the flow rate are measured;

a group of control units with which the operation of individual units is controlled; and

a central monitoring device which is linked by signal lines to the group of measuring instruments and the group of control units,

wherein the central monitoring device has, built into it, at least one of an air conditioning plant operation simulator which manages the operation of the whole air conditioning plant and an air conditioning plant operational data table;

computes on the basis of real time operational data picked up by the measuring instruments the optimal operating temperature and the optimal flow rate for the constituent units of the air conditioning plant and the optimal number of operating units of at least one of the low/high-temperature heat generator to minimize the energy consumption, operating cost or carbon dioxide emission equivalent or any indicator combining two or more of these factors of the whole air conditioning plant in predetermined ranges of conditions, including the temperature and humidity, of air conditioning, ranges of energy consumption conditions with respect to electric power, fuel, water and so forth, or various permissible areas of condition setting which satisfy the ranges of requirements set by combining these two sets of conditions in a prioritized manner; and

supplies those optimal values to the group of control units as control setpoints, and the control unit group generates control signals on the basis of the control setpoints, and supplies the control signals to the constituent units of the air conditioning plant or to the pertinent control units themselves to control at least two of the constituent units of the air conditioning plant at substantially the same time.

8. The control method as set forth in claim 7, wherein the central monitoring device has a device which enters from outside the priority or the indicator to be minimized and, on the basis of the external input and the various permissible areas of condition setting, controls the minimizing computation, the generation of the optimal control values and at least two of the constituent units of the air conditioning plant at substantially the same time.

9. The control method as set forth in claim 7, wherein the central monitoring device is provided in at least one of the units having devices which externally supply and display the energy consumption, the operating cost and the instantaneous value and the integrated value of the carbon dioxide emission equivalent of the whole of the air conditioning plant.

10. An air conditioning plant which performs air conditioning by supplying a low/high-temperature heat transfer medium in a circulatory manner, comprising:

simulation models of low/high-temperature heat generators, pumps and other units constituting the air conditioning plant,

wherein optimal control targets to minimize or maximize a performance criterion are determined by simulation, and the air conditioning plant is operated according to the optimal control targets.

11. The air conditioning plant as set forth in claim 10, further comprising:

a computer for computing optima, which determines optimal control targets to minimize or maximize a performance criterion by simulation; and

a monitoring/control unit which receives optimal control targets from the computer for computing optima and performs monitoring and control to ensure that constituent units of the air conditioning plant operate without abnormality,

wherein the processing period of the monitoring/control unit is shorter than that of the computer for computing optima, and the monitoring/control unit adjusts the control targets, in response to variations in the conditions of outside air, the temperature of cooling water, that of cold water and other factors, so that the operational limits of the units be not surpassed with reference to the optimal control targets determined by the computer for computing optima.

12. An air conditioning plant which performs air conditioning by supplying a low/high-temperature heat transfer medium in a circulatory manner, comprising:

an equipment characteristics database which stores characteristics data on constituent units of the air conditioning plant, an air conditioning plant simulator which computes power consumptions and fuel consumptions in partial loads from the equipment characteristics data of constituent units stored in the equipment characteristics database, and computes performance functions by using conversion coefficients; and

an optimizing device which computes the optimal control targets for the constituent units of the air conditioning plant by using the air conditioning plant simulator,

wherein the constituent units of the air conditioning plant are operated according to the optimal control targets.

13. The air conditioning plant as set forth in claim 12, further comprising:

a computer for computing optima, which determines optimal control targets to minimize or maximize a performance criterion by simulation; and

a monitoring/control unit which receives optimal control targets from the computer for computing optima and performs monitoring and control to ensure that constituent units of the air conditioning plant operate without abnormality,

wherein the processing period of the monitoring/control unit is shorter than that of the computer for computing optima, and the monitoring/control unit adjusts the control targets, in response to variations in the conditions of outside air, the temperature of cooling water, that of cold water and other factors, so that the operational limits of the units be not surpassed with reference to the optimal control targets determined by the computer for computing optima.

14. The air conditioning plant as set forth in claim 12, wherein parameters required for air conditioning plant simulation by the air conditioning plant simulator are identified on the basis of measurements by sensors, the air conditioning plant is simulated using the identified parameters, and the parameters to be identified are the resistance coefficients of piping and ducting.