Patent Publication Number: US-2009234511-A1

Title: Demand control device

Description:
TECHNICAL FIELD 
     The present invention relates to a demand control device which predicts a power consumption integrated value in a demand time interval, and controls appliances based on a predicted value. 
     BACKGROUND ART 
     A demand-based contract system is available as a contract system for electricity rates, which is implemented between a store/facility owner and an electric power company. The demand-based contract system determines electricity rates based on the maximum integrated value of electric power consumed in demand time intervals in a year. In this system, a power consumption integrated value is calculated for each one of the predetermined demand time intervals, and the electricity rates are determined based on the maximum of the power consumption integrated values calculated for the respective demand time interval in a year. The demand time interval is a time period value such as 15 minutes or 30 minutes, or a time zone between 12:00 and 2:00 in which electric power consumption increases. Therefore, it is necessary to minimize the power consumption integrated value in one demand time interval. 
     To meet the necessity, a control (demand control) operation is performed which predicts a power consumption integrated value from the start of a demand time interval to the end thereof during the demand time interval, and halts the operation of a specified appliance when the predicted value exceeds the predetermined contract power amount. 
     Typical demand control is effected by predicting, for each one of demand time intervals, a power consumption integrated value only within the demand time interval, and performing a demand control operation in the demand time interval based on the predicted value. Therefore, in the case where the predicted value for the demand time interval is considerably larger than a target value, a method of operating appliances should be significantly changed compared with the case where the predicted value for the demand time interval is not more than the target value. In some cases, it is impossible to reduce the power consumption integrated value within the demand time interval to a value not more than the target value. 
     In the paragraph numbered [0014] in the publication of Japanese Patent No. 2913584, it is disclosed to measure and record a demand value (the maximum of the mean values of electric power amounts which are averaged every 30 minutes), outside air temperature data, and humidity data obtained at an air-cooled place, perform learning calculations to predict a demand control issue time and a demand control duration, calculate an excessive cooling set temperature, an excessive cooling required period, and an excessive cooling start time, and control an air conditioner based on the results of the calculations. However, it is unknown how to predict the demand control issue time and the demand control duration based on the demand value, the outside air temperature data, and the humidity data obtained at the air-cooled place. It is also unknown how to calculate the excessive cooling set temperature, the excessive cooling required period, and the excessive cooling start time. 
     An object of the present invention to provide a demand control device which calculates a predicted value of a power consumption integrated value for each one of a plurality of demand time intervals including a current demand time interval and a predetermined number of demand time intervals subsequent to the current demand time interval to allow, when the predicted value exceeds a target value in any of the demand time intervals, a reduction in power consumption integrated value in the foregoing demand time interval in which the predicted value exceeds the target value through effective use of another demand time interval in which the predicted value has a margin. 
     DISCLOSURE OF THE INVENTION 
     A demand control device according to a first aspect of the present invention is a demand control device applied in a facility provided with a plurality of power-consuming appliances, the demand control device including a unit arranged to store performance data of a power consumption integrated value for each individual environmental condition in a power database, a predicted value calculating unit arranged to calculate a predicted value of the power consumption integrated value for each one of a plurality of demand time intervals including a current demand time interval and a predetermined number of demand time intervals subsequent to the current demand time interval based on the performance data stored in the power database at a start of the demand time interval, and a control unit arranged to control the appliances based on the predicted value calculated by the predicted value calculating unit for each one of the plurality of demand time intervals and on a pre set target value, wherein the control unit includes a unit arranged to change, when the plurality of demand time intervals include the demand time interval in which the predicted value exceeds the target value and the demand time intervals in each of which the predicted value does not exceed the target value, and operation contents each scheduled in the demand time interval in which the predicted value exceeds the target value include the operation content whose operation time is changeable, the changeable operation time of the operation content such that the operation content whose operation time is changeable is executed in any of the demand time intervals in each of which the predicted value does not exceed the target value. 
     In the demand control device according to the first inventive aspect, the operation content whose operation time is, e.g., a defrosting operation of a showcase. 
     In the demand control device according to the first inventive aspect, the control unit may include a unit arranged to select, when the predicted value calculated by the predicted value calculating unit for the current demand time interval exceeds the target value, any of the appliances whose operation should be halted based on a difference between the predicted value for the current demand time interval and the target value, and halt the operation of the selected appliance. 
     In the demand control device according to the first inventive aspect, the control unit may include a unit arranged to select, when the predicted value calculated by the predicted value calculating unit for the current demand time interval exceeds the target value, any of the appliances which should be halted based on a difference between the predicted value for the current demand time interval and the target value, and halt the selected appliance, and a unit arranged to select, when the predicted value calculated by the predicted value calculating unit for the current demand time interval is not more than the target value, any of the appliances whose operation should be recovered based on the difference between the predicted value for the current demand time interval and the target value, and recover the operation of the selected appliance. 
     A demand control device according to a second aspect of the present invention is a demand control device applied in a facility provided with a plurality of power-consuming appliances, the demand control device including a unit arranged to store performance data of a power consumption integrated value for each individual environmental condition in a power database, a predicted value calculating unit arranged to calculate a predicted value of the power consumption integrated value for each one of a current demand time interval and a demand time interval subsequent to the current demand time interval based on the performance data stored in the power database at a start of the demand time interval, and a control unit arranged to control the appliances based on the predicted value calculated by the predicted value calculating unit for each one of the plurality of demand time intervals and on a pre-set target value, wherein the control unit includes a unit arranged to control, when the predicted value for the current demand time interval does not exceed the target value, and the predicted value for the subsequent demand time interval exceeds the target value, an operation of at least one of the appliances which are continuously operated over the both demand time intervals such that an effect of operating the appliance is higher in the current demand time interval than during a normal operation. 
     In the demand control device according to the second inventive aspect, the appliance which is continuously operated over the both demand time intervals is, e.g., a temperature adjusting appliance. In this case, when the predicted value for the current demand time interval does not exceed the target value, and the predicted value for the subsequent demand time interval exceeds the target value, the control unit changes a set temperature of the temperature adjusting appliance such that an effect of operating the appliance is higher in the current demand time interval than during a normal operation. 
     In the demand control device according to the second inventive aspect, the control unit may include a unit arranged to select, when the predicted value calculated by the predicted value calculating unit for the current demand time interval exceeds the target value, any of the appliances whose operation should be halted based on a difference between the predicted value for the current demand time interval and the target value, and halt the operation of the selected appliance. 
     In the demand control device according to the second inventive aspect, the control unit may include a unit arranged to select, when the predicted value calculated by the predicted value calculating unit for the current demand time interval exceeds the target value, any of the appliances which should be halted based on a difference between the predicted value for the current demand time interval and the target value, and halt the selected appliance, and a unit arranged to select, when the predicted value calculated by the predicted value calculating unit for the current demand time interval is not more than the target value, any of the appliances whose operation should be recovered based on the difference between the predicted value for the current demand time interval and the target value, and recover the operation of the selected appliance. 
     A demand control device according to a third aspect of the present invention is a demand control device applied in a facility provided with a plurality of power-consuming appliances, the demand control device including a unit arranged to store performance data of a power consumption integrated value for each individual environmental condition in a power database, a predicted value calculating unit arranged to calculate a predicted value of the power consumption integrated value for each one of a plurality of demand time intervals including a current demand time interval and a predetermined number of demand time intervals subsequent to the current demand time interval based on the performance data stored in the power database at a start of the demand time interval, and a control unit arranged to control the appliances based on the predicted value calculated by the predicted value calculating unit for each one of the plurality of demand time intervals and on a pre-set target value, wherein the control unit includes a first unit arranged to change, when the plurality of demand time intervals include the demand time interval in which the predicted value exceeds the target value and the demand time intervals in each of which the predicted value does not exceed the target value, and operation contents each scheduled in the demand time interval in which the predicted value exceeds the target value include the operation content whose operation time is changeable, the changeable operation time of the operation content such that the operation content whose operation time is changeable is executed in any of the demand time intervals in each of which the predicted value does not exceed the target value, and a second unit arranged to control, when the operation time is not changed by the first unit, the predicted value for the current demand time interval does not exceed the target value, and the predicted value for the demand time interval subsequent to the current demand time interval exceeds the target value, at least one of the appliances which are continuously operated over both the current demand time interval and the subsequent demand time interval such that an effect of operating the appliance is higher in the current demand time interval than during a normal operation. 
     In the demand control device according to the third inventive aspect, the operation content whose operation time is changeable is, e.g., a defrosting operation of a showcase. 
     In the demand control device according to the third inventive aspect, the appliance which is continuously operated over the both demand time intervals is, e.g., a temperature adjusting appliance. In this case, when the predicted value in the current demand time interval does not exceed the target value, and the predicted value in the subsequent demand time interval exceeds the target value, the second unit changes a set temperature of the temperature adjusting appliance such that the effect of operating the appliance is higher in the current demand time interval than during a normal operation. 
     In the demand control device according to the third inventive aspect, the control unit may include a third unit arranged to select, when the predicted value calculated by the predicted value calculating unit for the current demand time interval exceeds the target value, any of the appliances whose operation should be halted based on a difference between the predicted value for the current demand time interval and the target value, and halt an operation of the selected appliance. 
     In the demand control device according to the third inventive aspect, the control unit may include the third unit arranged to select, when the predicted value calculated by the predicted value calculating unit for the current demand time interval exceeds the target value, any of the appliances whose operation should be halted based on the difference between the predicted value for the current demand time interval and the target value, and halt the selected appliance, and a fourth unit arranged to select, when the predicted value calculated by the predicted value calculating unit for the current demand time interval is not more than the target value, any of the appliances whose operation should be recovered based on the difference between the predicted value for the current demand time interval and the target value, and recover the operation of the selected appliance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  is a block diagram showing power-consuming appliances provided in a store such as a supermarket, and a controller for centralized control of those appliances; 
         FIG. 2  is a schematic diagram for illustrating each environmental condition specified by a time zone and an outside air temperature; 
         FIG. 3  is a schematic diagram showing a part of the content of a power database  24 ; 
         FIG. 4  is a schematic diagram showing an example of the content of an operation state database  25 ; 
         FIG. 5  is a schematic diagram showing an example of the content of a halt/recovery table 26; 
         FIG. 6  is a flow chart showing the procedure of a demand control process executed by a controller  20  (CPU  21 ); 
         FIG. 7  is a flow chart showing the procedure of a prediction control process at the start of the demand time interval in step S 5  of  FIG. 6 ; 
         FIG. 8  is a flow chart showing a detailed procedure of a process in step S 510  of  FIG. 7 ; 
         FIG. 9  is a flow chart showing a detailed procedure of a process in step S 520  of  FIG. 7 ; 
         FIG. 10  is a flow chart showing the procedure of a prediction control process during the demand time interval in step S 6  of  FIG. 6 ; and 
         FIG. 11  is a flow chart showing a detailed procedure of a process in step  620  of  FIG. 10 . 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Referring now to the drawings, an embodiment of the present invention will be described hereinbelow. 
       FIG. 1  shows power-consuming appliances provided in a store such as a supermarket, and a controller for centralized control of those appliances. 
     The controller  20  is connected to each of the power-consuming appliances arranged in the store, e.g., a showcase  1 , a refrigerator  2 , an air conditioner  3 , and the like. The controller  20  is also connected to a power meter  11  which measures electronic power consumption. The controller  20  is further connected to a temperature sensor  12  for measuring an outside air temperature. 
     The controller  20  includes a CPU  21 . The CPU  21  is connected to a ROM  22  which stores a program thereof or the like, a RAM  23  which stores necessary data, a power database  24 , an operation state database  25 , a halt/recovery table 26, a timer  27 , and the like. The power database  24 , the operation state database  25 , and the halt/recovery table 26 are created in, e.g., a rewritable nonvolatile memory. 
     The power database  24  stores power consumption integrated value data (previous performance data) for each individual environmental condition. In this example, as shown in  FIG. 2 , the environmental condition is specified by a time zone and an outside air temperature. Each square in  FIG. 2  shows an individual environmental condition. In the example of  FIG. 2 , the time zone and the outside air temperature are divided at intervals of 10 minutes and 5 degrees, respectively. The diagonally hatched square shown in  FIG. 2  indicates the environmental condition where the time zone is from 0:30 to 0:40, and the outside air temperature is from 5° C. to 10° C. In  FIG. 2 , (N−1), N, and (N+1) represent demand time intervals. 
       FIG. 3  shows a part of the content of the power database  24 , which is the power consumption integrated value data stored in association with the environmental condition where the time zone is from 0:30 to 0:40, and the outside air temperature is from 5° C. to 10° C. 
     A maximum of ten performance data (power consumption integrated value data) can be stored for each individual environmental condition. When the number of performance data exceeds ten for one environmental condition, the oldest data is deleted, and the latest data is newly added. 
     As shown in  FIG. 4 , the operation state database  25  stores an outside air temperature, and a power consumption integrated value from the start of a demand time interval up to the current time on a per time basis. At the start of the demand time interval, the power consumption integrated value is set to 0. 
     As shown in  FIG. 5 , the halt/recovery table 26 stores an appliance name, an operation state (in operation or at a halt), an order of halt, an order of recovery, and an expected power reduction for each one of haltable appliances. 
     The order of halt indicates a priority in halting the operation of an appliance. The order of recovery indicates a priority in activating an appliance at a halt. The expected power reduction indicates the electric power consumption expected to be reduced at the time when the operation of the appliance is halted. The expected power reduction is assumed to be, e.g., mean power consumption during immediately previous 30 minutes. Alternatively, when power measurement is not performed for each individual appliance, the expected power reduction may also be calculated from the rated power of an appliance. The expected power reduction is assumed to be, e.g., 50% of the rated power. 
       FIG. 6  shows the procedure of a demand control process executed by the controller  20  (CPU  21 ). 
     This process is executed every given period of time, e.g., every one minute. 
     First, a current time, an outside air temperature, and a power consumption integrated value from the start of a demand time interval up to the current time are stored in the operation state database  25 , while the operation states of appliances are stored in the halt/recovery table 26 (step S 1 ). The outside air temperature is acquired from the temperature sensor  12 . The power consumption integrated value from the start of the demand time interval up to the current time is calculated based on the power consumption acquired from the power meter  11 , and the power consumption integrated value stored in the operation state database  25 . 
     Next, it is determined whether or not the time is immediately after the change of the time zone that specifies the environmental condition (step S 2 ). Since the time zone is divided at intervals of 10 minutes, it is determined whether or not the time is immediately after M:00 (M is a natural number of 0 to 23), M:10, M:20, M:30, M:40, or M:50. When it is determined that the time is not immediately after the change of the time zone that specifies the environmental condition, the current process is ended. 
     In step S 2  mentioned above, when it is determined that the time is immediately after the change of the time zone that specifies the environmental condition, the power consumption integrated value in the preceding time zone is stored in the power database  24  as the performance data for the environmental condition which coincides with the environmental condition in the preceding time zone (step S 3 ). In this case, the power consumption integrated value data in the preceding time zone is obtained from the power consumption integrated value in the corresponding time zone stored in the operation state database  25 . The outside air temperature is obtained by calculating the mean value of the outside air temperature data in the preceding time zone stored in the operation state database  25 . After the process in step S 3 , the whole process flow advances to step S 4 . 
     In step S 4 , it is determined whether or not the time is when the demand time interval starts. When it is determined that the time is when the demand time interval starts, the prediction control process at the start of the demand time interval is performed (step S 5 ). The details of the prediction control process at the start of the demand time interval will be described later. Then, the current process is ended. 
     In the step S 4  mentioned above, when it is determined that the time is not when the demand time interval starts, the prediction control process during the demand time interval is performed (step S 6 ). The details of the prediction control process during the demand time interval will be described later. Then, the current process is ended. 
       FIG. 7  shows the procedure of the prediction control process at the start of the demand time interval in step S 5  of  FIG. 6 . 
     It is assumed that N represents the current demand time interval, (N−1), (N−2), . . . represent the time intervals previous thereto, and (N+1), (N+2), . . . represent the time intervals subsequent thereto. It is also assumed that a target value Y in the demand time interval has been predetermined. At the start of the demand time interval, the expected value of the power consumption integrated value is calculated for each one of the plurality of demand time intervals including the current demand time interval and the predetermined number of demand time intervals subsequent to the current demand time interval. In this embodiment, the predicted value of the power consumption integrated value is calculated for each one of the plurality of demand time intervals N, (N+1), and (N+2) including the current demand time interval and the two demand time intervals subsequent to the current demand time interval, as will be shown in step S 502  described later. It is assumed in this embodiment that the showcase  1  and the air conditioner  3  are continuously operated over both the current demand time interval N and the subsequent demand time interval (N+1). 
     In the prediction control process at the start of the demand time interval, when the set temperature of the showcase or the air conditioner lo has been changed by the demand control process in the preceding time interval (N−1), the changed set temperature is returned to the original value (step S 501 ). Specifically, when the set temperature of the showcase has been changed in step S 514  (see  FIG. 8 ) described later in the preceding time interval (N−1), or when the set temperature of the air conditioner has been changed in step S 517  (see  FIG. 8 ) described later in the preceding time interval (N−1), the settings are returned to the original ones. 
     Next, the power consumption integrated value in each of the time intervals N, (N+1), and (N+2) is predicted (step S 502 ). For example, the predicted value of the power consumption integrated value in the time interval N is calculated as follows. That is, performance data corresponding to an environmental condition where the time zone is the first 10 minute time zone in the time interval N, and the outside air temperature coincides with the current outside air temperature is extracted from the power database  24 , and a mean value xi of the performance data is calculated. In addition, performance data corresponding to an environmental condition where the time zone is an exactly middle  10  minute time zone in the time interval N, and the outside air temperature coincides with the current outside air temperature is extracted from the power database  24 , and a mean value x2 of the performance data is calculated. 
     Further, performance data corresponding to an environmental condition where the time zone is the last 10 minute time zone in the time interval N, and the outside air temperature coincides with the current outside air temperature is extracted from the power database  24 , and a mean value x3 of the performance data is calculated. Then, (x1+x2+x3) is calculated, and the result of the calculation is designated as a predicted value X N  of the power consumption integrated value in the time interval N. 
     Likewise, predicted values X N+1  and X N+2  of the respective power consumption integrated values in the time intervals (N+1) and (N+2) are also calculated. 
     Next, it is determined whether or not the predicted value X N+1  of the power consumption integrated value in the time interval (N+1) exceeds the target value Y (step S 503 ). When X N+1 ≦Y is satisfied, the process (prediction control process in the time interval N) in step S 520  is performed, and then the current process is ended. The details of the process in step S 520  will be described later. 
     When X N+1 &gt;Y is satisfied, it is determined whether or not a defrosting operation of the showcase  1  is scheduled in the time interval (N+1) (step S 504 ). When the defrosting operation of the showcase  1  is not scheduled, the process in step S 510  (control process for the showcase or the air conditioner) is performed, and then the whole process flow moves to step S 520 . The details of the process in step S 510  will be described later. 
     When the defrosting operation of the showcase  1  is scheduled, the margin of the predicted value X N  with respect to the target value Y in the time interval N, and the margin of the predicted value X N+2  with respect to the target value Y in the time interval (N+2) are calculated (step S 505 ). Specifically, the margin in the time interval N is calculated based on Δ N =(Y−X N ), and the margin in the time interval (N+2) is calculated based on Δ N+2 =(Y−X N+2 ). 
     Then, it is determined whether or not at least one of the predicted values in the time interval N and the time interval (N+2) has a margin with respect to the target value (step S 506 ). Specifically, it is determined whether or not at least one of Δ N  and Δ N+2  is more than 0. When at least one of Δ N  and Δ N+2  is more than 0, it is determined that at least one of the predicted values in the time interval N and the time interval (N+2) has a margin with respect to the target value. On the other hand, when each of Δ N  and Δ N+2  is not more than 0, it is determined that neither the predicted value in the time interval N nor the predicted value in the time interval (N+2) has a margin with respect to the target value. 
     When it is determined that at least one of the predicted values in the time interval N and the time interval (N+2) has a margin with respect to the target value, an operation pattern is changed such that the defrosting operation scheduled in the time interval (N+1) is performed in the time interval with a larger margin (step S 507 ). Then, the whole process flow moves to step S 520 . 
     In the step S 506  mentioned above, when it is determined that the power consumption has no margin in each of the time interval N and the time interval (N+2), the whole process flow moves to step S 520 . 
       FIG. 8  shows a detailed procedure of a process in step S 510  of  FIG. 7 . 
     It is determined whether or not the predicted value X N  of the power consumption integrated value in the time interval N exceeds the target value Y (step S 511 ). When X N &gt;Y is satisfied, the whole process flow moves to step S 520  of  FIG. 7 . 
     When X N ≦Y is satisfied, the current cooling state of the showcase  1  is examined (step S 512 ). That is, the set temperature of the showcase  1  and the actual temperature of the showcase  1  are examined. Then, it is determined whether or not the actual temperature of the showcase  1  is not more than a temperature obtained by adding a predetermined value a to the set temperature (step S 513 ) 
     When the actual temperature of the showcase  1  is not more than the temperature obtained by adding the predetermined value a to the set temperature, it is determined that the showcase  1  is normally performing the cooling function, and the set temperature of the showcase  1  in the time interval N is reduced to a value lower than a normally set value (step S 514 ). This is for achieving a reduction in power consumption integrated value in the time interval (N+1) by reducing the set temperature in the time interval N to extremely cool the showcase  1  till the internal temperature thereof reaches a value lower than the normally set value, and returning the set temperature to the original value at the start of the time interval (N+1). Then, the whole process flow moves to step S 520  of  FIG. 7 . 
     When the actual temperature of the showcase  1  exceeds the temperature obtained by adding the predetermined value a to the set temperature, it is determined that the temperature of the showcase  1  cannot be effectively reduced even though the set temperature of the showcase  1  is reduced because of an air curtain which does not function due to a problem associated with a display condition, an air flow, or the like, and the whole process flow moves to step S 515 . 
     In step S 515 , the air conditioning state of the air conditioner  3  is examined. That is, the set temperature of the air conditioner  3  and the actual room temperature are examined. Then, it is determined whether or not the actual room temperature is close to the set temperature (step S 516 ). Specifically, when the air conditioner  3  is performing a cooling operation, it is determined whether or not the actual room temperature is not more than a temperature obtained by adding a predetermined value B to the set temperature. When the actual room temperature is not more than the temperature obtained by adding the predetermined value  1  to the set temperature, it is determined that the actual room temperature is close to the set temperature. When the air conditioner  3  is performing a heating operation, it is determined whether or not the actual room temperature is not less than a temperature obtained by subtracting the predetermined value β from the set temperature. When the actual room temperature is not less than the temperature obtained by subtracting the predetermined value β from the set temperature, it is determined that the actual room temperature is close to the set temperature. 
     When it is determined that the actual room temperature is close to the set temperature, the set temperature of the air conditioner  3  is changed to enhance the air conditioning effect in the time interval N (step S 517 ). That is, when the air conditioner  3  is performing a cooling operation, the set temperature is reduced to a value lower than a normally set value and, when the air conditioner  3  is performing a heating operation, the set temperature is increased to a value higher than a normally set value. Then, the whole process flow moves to step S 520  of  FIG. 7 . 
       FIG. 9  shows a detailed procedure of a process in step S 520  of  FIG. 7 . 
     It is determined whether or not the predicted value X N  of the power consumption integrated value in the time interval N exceeds the target value Y (X N &gt;Y) (step S 521 ). When X N ≦Y is satisfied, the prediction control process at the start of the current demand time interval is ended. 
     When X N &gt;Y is satisfied, the difference Z=(X N −Y) therebetween is calculated (step S 522 ). The calculated difference Z serves as the amount of power consumption to be reduced (target reduction value). Additionally, a predicted reduction value Q of the power consumption is set to 0 (step S 523 ). 
     Next, the appliance having the highest priority to be halted is selected from among the currently operated appliances in the halt/recovery table 26, and a power consumption reduction amount q at the time when the operation of the appliance is halted is also calculated (step S 524 ). The power consumption reduction amount q can be obtained by multiplying the expected power reduction stored in the halt/recovery table 26 by the remaining period (which is 30 minutes in this example) of the demand time interval. 
     The power consumption reduction amount q calculated in step S 524  is added to the predicted reduction value Q, and the result of the addition is designated as the predicted reduction value Q (step S 525 ). Then, it is determined whether or not the predicted reduction value Q is not less than the target reduction value Z (Q≧Z) (step S 526 ). 
     When the predicted reduction value Q is less than the target reduction value Z (Q&lt;Z), it is determined whether or not all the currently operated appliances of the haltable appliances recorded in the halt/recovery table 26 have been each selected as a target appliance for which the power consumption reduction amount q is to be calculated (step S 527 ). 
     When all the currently operated appliances of the haltable appliances recorded in the halt/recovery table 26 have not been each selected as the target appliance for which the power consumption reduction amount q is to be calculated, the whole process flow returns to step S 524  where the appliance having the highest priority to be halted except for the appliances already selected in step S 524  is selected, and the power consumption reduction amount q at the time when the operation of the selected appliance is halted is calculated. Then, the process in and subsequent to Step  525  is performed. 
     In the step S 526  mentioned above, when it is determined that the predicted reduction value Q is not less than the target reduction value Z (Q≧Z), all the appliances selected in the step S 524  mentioned above are brought into an operation halted state (step S 528 ). Then, the prediction control process at the start of the current demand time interval is ended. 
     In the step S 527  mentioned above, when it is determined that all the currently operated appliances of the haltable appliances recorded in the halt/recovery table 26 have been each selected as the target appliance for which the power consumption reduction amount q is to be calculated, all the appliances selected in the step S 524  mentioned above are brought into the operation halted state (step S 528 ). Then, the prediction control process at the start of the current demand time interval is ended. 
       FIG. 10  shows the procedure of the prediction control process during the demand time interval in step S 6  of  FIG. 6 . 
     In the prediction control process during the demand time interval, the actual power consumption integrated value from the start of the current time interval up to the current time is determined, and the predicted value of the power consumption integrated value from the current time up to the end of the demand time interval is also determined from the performance data stored for each individual environmental condition in the power database  24 . The sum of the actual power consumption integrated value and the predicted value is designated as the predicted value X N  of the power consumption integrated value in the current demand time interval. Appliance control is performed based on the predicted value X N  and the predetermined target value Y 
     First, based on the data stored in the operation state database  25 , an actual power consumption integrated value p from the start of the demand time interval up to the current time is determined (step S 601 ). 
     Next, the performance data (power consumption integrated value data) corresponding to the same environmental condition as the current environmental condition (the time zone and the outside air temperature) is extracted from the power database  24 , and the mean value of the performance data is calculated (step S 602 ). 
     Then, the power consumption integrated value p determined in step S 601  and the mean value xa calculated in step S 602  are added up, and the result of the addition is designated as the predicted value X N  (step S 603 ). 
     Next, it is determined whether or not the time zone subsequent to the time zone in which the mean value of the performance data is calculated belongs to the same demand time interval (step S 604 ). When the time zone subsequent to the time zone in which the mean value of the performance data is calculated belongs to the same demand time interval, the performance data (power consumption integrated value data) corresponding to the environmental condition where the outside air temperature coincides with the current outside air temperature in the subsequent time zone is extracted from the power database  24 , and the mean value xb of the performance data is calculated (step S 605 ). Then, the mean value xb of the calculated performance data is added to the predicted value X N , and the obtained result is designated as the predicted value X N  (step S 606 ). Then, the whole process flow returns to step S 604 . 
     In the case where the time is immediately after a lapse of 10 minutes from the start of the demand time interval, the actual power consumption integrated value p from the start of the demand time interval up to the current time is calculated in step S 601 , the mean value xa of the performance data in the time zone from the time point after the lapse of 10 minutes from the start of the demand time interval till a lapse of 20 minutes therefrom is calculated in step S 602 , and the arithmetic operation of X N =p+xa is performed in step S 603 . The first-time step S 604  results in YES, the mean value xb of the performance data in the time zone from the time point after the lapse of 20 minutes from the start of the demand time interval till a lapse of 30 minutes therefrom is calculated in step S 605 , and the arithmetic operation of X N =X N +xb is performed in step S 606 . Then, the second-time step S 604  results in NO. 
     In the case where the time is immediately after the lapse of 20 minutes from the start of the demand time interval, the actual power consumption integrated value p from the start of the demand time interval up to the current time is calculated in step S 601 , the mean value xa of the performance data in the time zone from the time point after the lapse of 20 minutes from the start of the demand time interval till the lapse of 30 minutes therefrom is calculated in step S 602 , and the arithmetic operation of X N =p+xa is performed in step S 603 . The first-time step S 604  results in NO. 
     In the step S 604  mentioned above, when it is determined that the time zone subsequent to the time zone in which the mean value of the performance data is calculated does not belong to the same demand time interval, step S 604  results in NO so that the whole process flow moves to Step S 607 . 
     In step S 607 , it is determined whether or not the predicted value X N  exceeds the predetermined target value Y (X N &gt;Y). 
     When X N &gt;Y is satisfied, the same process as performed in steps S 522  to S 528  of  FIG. 9  is performed. That is, the difference Z=(X N −Y) therebetween is calculated (step S 608 ). The calculated difference Z serves as the amount of power consumption to be reduced (target reduction value). Additionally, the predicted reduction value Q of the power consumption is set to 0 (Step S 609 ). 
     Next, the appliance having the highest priority to be halted is selected from among the currently operated appliances in the halt/recovery table 26, and the power consumption reduction amount q at the time when the operation of the selected appliance is halted is calculated (step S 610 ). The power consumption reduction amount q can be obtained by multiplying the expected power reduction stored in the halt/recovery table 26 by the remaining period (which is either 20 minutes or 10 minutes in this example) of the demand time interval. 
     The power consumption reduction amount q calculated in step S 610  is added to the predicted reduction value Q, and the result of the addition is designated as the predicted reduction value Q (step S 611 ). Then, it is determined whether or not the predicted reduction value Q is not less than the target reduction value Z (Q≧Z) (step S 612 ). 
     When the predicted reduction value Q is less than the target reduction value Z (Q&lt;Z), it is determined whether or not all the currently operated appliances of the haltable appliances recorded in the halt/recovery table 26 have been each selected as the target appliance for which the power consumption reduction amount q is to be calculated (step S 613 ). 
     When all the currently operated appliances of the haltable appliances recorded in the halt/recovery table 26 have not been each selected as the appliance for which the power consumption reduction amount q is to be calculated, the whole process flow returns to step S 610  where the appliance having the highest priority of being halted is selected from among the currently operated appliances except for the appliance already selected in step S 610 , and the power consumption reduction amount q at the time when the operation of the selected appliance is halted is calculated. Then, the process in and subsequent to step S 611  is performed. 
     In the step S 612  mentioned above, when it is determined that the predicted reduction value Q is not less than the target reduction value Z (Q&gt;Z), all the appliances selected in the step S 610  mentioned above is brought into the operation halted state (Step S 614 ). Then, the prediction control process during the current demand time interval is ended. 
     In the step S 613  mentioned above, when it is determined that all the currently operated appliances of the haltable appliances recorded in the halt/recovery table 26 have been each selected as the target appliance for which the power consumption reduction amount q is to be calculated, all the appliances selected in the step S 610  mentioned above are brought into the operation halted state (step S 614 ). Then, the prediction control process during the current demand time interval is ended. 
     In the step S 607  mentioned above, when X N ≦Y is satisfied, the recovery process is performed (S  620 ), and then the prediction control process during the current demand time interval is ended. The recovery process will be described later. 
       FIG. 11  shows a detailed procedure of a process in step S 620  of  FIG. 10 . 
     In the recovery process, the difference V=(Y−X N ) between the target value Y and the predicted value X N  is calculated (step S 621 ). The calculated difference V serves as the amount of power consumption to be recovered (target recovery value). Additionally, a target recovery value R of the power consumption is set to 0 (step S 622 ). 
     Next, the appliance having the highest priority to be recovered is selected from among the currently halted appliances in the halt/recovery table 26, and a power consumption increase amount r at the time when the selected appliance is operated is calculated (step S 623 ). The power consumption increase value r can be obtained by multiplying the expected power reduction stored in the halt/recovery table 26 by the remaining period (which is either 20 minutes or 10 minutes in this example) of the demand time interval. 
     The power consumption increase amount r calculated in step S 623  is added to the predicted recovery value R, and the result of the addition is designated as the predicted recovery value R (step S 624 ). Then, it is determined whether or not the predicted recovery value R is not less than the target recovery value V (R≧V) (step S 625 ). 
     When the predicted recovery value R is less than the target recovery value (R&lt;V), it is determined whether or not all the currently halted appliances of the haltable appliances recorded in the halt/recovery table 26 have been each selected as the target appliance for which the power consumption increase amount r is to be calculated (step S 628 ). 
     When all the currently halted appliances of the haltable appliances recorded in the halt/recovery table 26 have not been each selected as the target appliance for which the power consumption increase amount r is to be calculated, the whole process flow returns to step S 623  where the appliance having the highest priority to be recovered is selected from among the currently halted appliances except for the appliance already selected in step S 623 , and the power consumption increase amount r at the time when the selected appliance is operated is calculated. Then, the process in and subsequent to S 624  is performed. 
     In the step S 625  mentioned above, when it is determined that the predicted recovery value R is not less than the target recovery value V (R≧V), all the appliances selected in the step S 623  mentioned above, except for the finally selected one, are each designated as the recovery target appliance (step S 626 ). Then, the whole process flow moves to step S 627 . 
     In the step S 628  mentioned above, when it is determined that all the currently halted appliances of the haltable appliances recorded in the halt/recovery table 26 have been each selected as the target appliance for which the power consumption increase amount r is to be calculated, all the appliances selected in the step S 623  mentioned above are each designated as the recovery target appliance (step S 629 ). Then, the whole process flow moves to step S 627 . 
     In step S 627 , the recovery target appliance is brought into an operated state. Then, the prediction control process during the current demand time interval is ended. 
     In the embodiment described above, the environmental condition is specified by the time zone and the outside air temperature. However, the environmental condition may also be specified by other elements, e.g., the time zone and a temperature (or humidity) inside a store. 
     According to the embodiment described above, the predicted value of the power consumption integrated value is calculated for each one of the plurality of demand time intervals including the current demand time interval and the predetermined number of demand time intervals subsequent to the current demand time interval and, when the predicted value exceeds the target value in any of the demand time intervals, another demand time interval in which the predicted value has a margin is effectively used to allow a reduction in power consumption integrated value in the demand time interval in which the predicted value exceeds the target value. 
     Specifically, in the case where an operation content whose operation time is changeable, such as a defrosting operation, exists in the subsequent demand time interval in which the target value is exceeded, the changeable operation time of the operation content is changed such that the operation content whose operation time is changeable is executed in another demand time interval in which the predicted value has a margin. In the case where the predicted value has a margin in the demand time interval immediately preceding the demand time interval in which the target value is exceeded, subsequent to the current demand time interval, operation control is performed with respect to an appliance such as a showcase or an air conditioner such that the effect of operating the appliance is higher in the immediately preceding demand time interval than during a normal operation. 
     In accordance with the present invention, the predicted value of the power consumption integrated value is calculated for each one of a plurality of demand time intervals including a current demand time interval and a predetermined number of demand time intervals subsequent to the current demand time interval and, when the predicted value exceeds the target value in any of the demand time intervals, another demand time interval in which the predicted value has a margin is effectively used to allow a reduction in power consumption integrated value in the demand time interval in which the predicted value exceeds the target value, subsequent to the current demand time interval.