Patent Publication Number: US-2017363315-A1

Title: Heat source system operation management apparatus, heat source system operation management method and computer program

Description:
TECHNICAL FIELD 
     The present invention relates to a heat source system operation management apparatus, a heat source system operation management method, and a computer program. 
     BACKGROUND ART 
     In recent years, influence on environment due to power shortage associated with an increase in energy consumption and an increase in greenhouse gas emission has been a problem. For that reason, efforts of efficient energy use to realize energy saving and CO2 emission reduction have been progressed. As one of the measures, there is utilization of a heat source system including a heat storage tank. The heat storage tank of the heat source system supplies heat stored in advance to an air conditioner in accordance with fluctuation of a heat load (air conditioning load). A peak of power demand can be shifted by using the heat storage tank during a high heat load time zone. 
     As a conventional technique relating to the heat source system, a technique has been known for providing a control apparatus that performs optimal operation of the heat source system including the heat storage tank (PTL 1). In the conventional technique according to PTL 1, the heat load is predicted with reference to actual weather data, operation result data, and characteristics of the building, and operation plan data is generated for making maximum use of the heat storage tank from the predicted heat load, and operation of the heat source system is controlled. In the conventional technique, when a difference between a remaining amount of heat storage and the heat load due to a difference between an operation plan and an operation result is out of a predetermined range, the operation plan is reviewed. 
     In addition, a technique also has been known that reduces an operator&#39;s burden and secures stable supply of a heat source and safe operation, and appropriately performs start and stop of the heat source in an emergency (PTL 2). In the conventional technique according to PTL 2, the heat load is predicted based on temperature distribution of the heat storage tank, inlet/outlet temperature of a heat source device, flow rate, measurement value of circulating water temperature, weather information, and day of week information, and a heat storage tank operation plan and a heat source device operation plan are created based on the predicted heat load, and the heat source device is controlled. When a shift occurs between a planned value and an actual value due to accumulation of prediction errors, the operation plan is corrected. 
     CITATION LIST 
     Patent Literature 
     PTL 1: JP 2008-82642 A 
     PTL 2: JP H5-88715 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the conventional technique, during creation of an operation plan for storing/releasing heat to/from the heat source device, the plan is created based on a predetermined heat storage capacity (it is also an amount of releasable heat. The same applies to the following). The heat storage capacity is determined by a heat storage tank capacity, a cold water feed temperature (set value) from the heat source device such as a chiller, and a cold water return temperature from a consumer side (such as an air conditioner). In the conventional technique, either of a design value, or a cold water return temperature measured at the time of operation planning is used as the cold water return temperature, and the heat storage capacity is evaluated with the cold water return temperature. 
     However, depending on seasons, weather conditions, and the like, the cold water return temperature during heat release differs from the design value (assumed value) or actual measured temperature at the time of operation planning, in many cases. When the cold water return temperature changes outside an assumed range, the heat storage capacity also differs, so that an appropriate operation plan cannot be created. 
     For example, when an actual cold water return temperature is lower than the assumed value, the heat storage capacity has been overestimated, so that an amount of cold heat to be supplied during heat release becomes insufficient. Conversely, when the actual cold water return temperature is higher than the assumed value, the heat storage capacity has been underestimated, so that the amount of cold heat becomes in excess. 
     The present invention has been made in view of the above problem, and it is an object to provide a heat source system operation management apparatus, a heat source system operation management method, and a computer program that are capable of predicting a refrigerant return temperature and estimating a heat storage capacity, to create an appropriate operation plan for a heat source system. 
     Solution to Problem 
     To solve the above problem, a heat source system operation management apparatus according to the present invention is an operation management apparatus for managing operation of a heat source system that supplies a refrigerant to an air conditioner, and the apparatus includes: a refrigerant return temperature prediction unit that predicts a refrigerant return temperature that is a temperature of the refrigerant returning from the air conditioner to the heat source system; a heat storage capacity estimation unit that estimates a heat storage capacity of the heat source system, based on the predicted refrigerant return temperature; and an operation plan creation unit that creates an operation plan for the heat source system, based on the estimated heat storage capacity. 
     An operation control data creation unit can be further included that creates operation control data for controlling the operation of the heat source system in accordance with the operation plan created by the operation plan creation unit. 
     The heat source system may include a heat storage tank that supplies the stored refrigerant to the air conditioner; a refrigerant generation unit that cools the refrigerant returning from the air conditioner via the heat storage tank, and supplies the cooled refrigerant to the heat storage tank; a refrigerant feed temperature detection unit that measures and outputs a temperature of the refrigerant fed from the refrigerant generation unit to the heat storage tank; and a refrigerant return temperature detection unit that measures and outputs a temperature of the refrigerant returning from the heat storage tank to the refrigerant generation unit. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to predict a return temperature of the refrigerant returning from the air conditioner to the heat source system, and estimate the heat storage capacity of the heat source system, based on the predicted refrigerant return temperature, and create the operation plan for the heat source system, based on the estimated heat storage capacity. Thus, the heat stored in the heat storage tank can be efficiently used. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an overall configuration diagram including a heat source system and an operation management apparatus. 
         FIG. 2  is a block diagram of the operation management apparatus. 
         FIG. 3  is a flowchart of an operation plan creation process. 
         FIG. 4  is a flowchart of a cold water return temperature prediction process. 
         FIG. 5  is a configuration example of operation result data. 
         FIG. 6  is a flowchart of a process of calculating a cold heat unit price. 
         FIG. 7  is a graph illustrating an example of energy consumption characteristics of a chiller. 
         FIG. 8  is a graph illustrating time change of a power unit price. 
         FIG. 9  illustrates an example of an operation plan. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an embodiment of the present invention is described with reference to the drawings. In the present embodiment, a description is made where water is used as a refrigerant, as an example. Further, in the present embodiment, the description is made where an air conditioner  3  is caused to perform cooling operation, as an example. However, the present embodiment can be applied not only to a case of cooling operation, but also to a case of heating operation. 
     A heat source system operation management apparatus  1  of the present embodiment predicts a cold water return temperature that meets conditions at a scheduled heat release time on an operation plan date, based on previous operation result data  102  (season, date and time, day of week, environmental conditions such as temperature, humidity and weather, amount of cold heat, cold water return temperature), in a heat source system  2  that provides cold water to a plurality of the air conditioners  3 , as described in detail below. The heat source system operation management apparatus  1  estimates a heat storage capacity (amount of releasable heat), based on the predicted cold water return temperature, and creates an operation plan (heat storage and heat release plan) of a heat source device  22 , based on the estimated heat storage capacity. 
     Further, the heat source system operation management apparatus  1  creates operation control data for controlling a chiller  22  as the heat source device, based on the created operation plan. The heat source system operation management apparatus  1  can also include an apparatus  13  for referring to the operation plan and a creation result of the operation control data. Further, the heat source system operation management apparatus  1  stores result data of the chiller  22  as the operation result data, and utilizes the result data for a prediction process of cold water return temperature on a later date. 
     According to the present embodiment thus configured, in the heat source system  2  including a heat storage tank  20 , it is possible to estimate the heat storage capacity corresponding to the fluctuating cold water return temperature, and create the optimal operation plan to appropriately control the chiller  22 . Thus, energy saving operation can be achieved, and an operation cost can be reduced. 
     Example 1 
     An example is described with reference to  FIG. 1  to  FIG. 9 .  FIG. 1  illustrates an overall configuration example of an energy network system including the heat source system  2  and the operation management apparatus  1 . 
     The energy network system includes the heat source system operation management apparatus  1  (hereinafter, the operation management apparatus  1 ), the heat source system  2 , and at least one air conditioner  3 . As described above, here, a case is described where cold water is supplied to the air conditioner  3  for cooling. 
     A configuration of the heat source system.  2  is described. The heat source system  2  includes, for example, the heat storage tank  20 , a primary side water feed pump  21 , the chiller  22  that is the heat source device, a secondary side water feed pump  23 , a cold water feed temperature detection unit  24 , a cold water return temperature detection unit  25 , and piping L1, L2, L3, L4, L5. 
     A discharge port of each of a plurality of the primary side water feed pumps  21  is connected to the chiller  22  via the first piping L1. Each chiller  22  is an example of the heat source device, and corresponds to a “refrigerant generation unit.” The cold water generated by each chiller  22  is supplied to the heat storage tank  20  via the second piping L2. 
     The heat storage tank  20  is configured as a single temperature stratified heat storage tank, for example. In the heat storage tank  20 , two layers  20 L,  20 H are formed depending on a density difference of the cold water. One layer is the low temperature portion  20 L in which cold water  26  with relatively low temperature from each chiller  22  is positioned. The other layer is the high temperature portion  20 H in which cold water  27  with relatively high temperature returning from the air conditioner  3  is positioned. 
     The cold water  26  of the low temperature portion  20 L of the heat storage tank  20  is fed to a heat load apparatus  30  in the air conditioner  3  via the third piping L3 by the secondary side water feed pump  23 . The cold water  27  warmed by heat exchange by the heat load apparatus  30  returns to the high temperature portion  20 H of the heat storage tank  20  via the fourth piping L4. 
     The cold water  27  of the high temperature portion  20 H of the heat storage tank  20  is fed to a suction port of each primary side water feed pump  21  via the fifth piping L5. As described above, the cold water  27  with high temperature is fed to the chiller  22  and its temperature is decreased, and supplied to the heat storage tank  20  as cold water with low temperature. In this way, the heat source system  2  circulates the cold water stored in the heat storage tank  20  with the air conditioner  3 . A temperature boundary  20 B between the low temperature portion  20 L and the high temperature portion  20 H of the heat storage tank  20  fluctuates depending on an operation condition of the heat source system  2 . 
     In the middle of the second piping L2 that connects each chiller  22  and the heat storage tank  20  together, the cold water feed temperature detection unit  24  is provided to measure a temperature Ts of the cold water  26  supplied from each chiller  22  to the heat storage tank  20  and output the temperature to the operation management apparatus  1 . In the middle of the fifth piping L5 that connects the heat storage tank  20  and each primary side water feed pump  21  together, the cold water return temperature detection unit  25  is provided to measure a temperature Tr of the cold water  27  supplied from the heat storage tank  20  via each primary side water feed pump  21  to each chiller  22  and output the temperature to the operation management apparatus  1 . An installation position of each of the temperature detection units  24 ,  25  is not limited to the example illustrated in  FIG. 1 . 
     Further, in  FIG. 1 , three primary side water feed pumps  21  and three chillers  22  are illustrated; however, not limited thereto, the number of each of the primary side water feed pumps  21  and the chillers  22  may be one, two, or four or more. The number of the primary side water feed pumps  21  and the number of the chillers  22  do not need to match each other. The heat source system  2  can supply the cold water to the plurality of air conditioners  2 , and each air conditioner  3  can include a plurality of the heat load apparatus  30 . 
     As described above, in the heat storage tank  20 , there are the low temperature portion  20 L including low temperature cold water with low temperature and a high density, and the high temperature portion  20 H including high temperature cold water with high temperature and a low density. When the low temperature cold water  26  is fed into the heat storage tank  20  to store heat, a region of the low temperature portion  20 L increases, and the temperature boundary  20 B rises. When the low temperature cold water  26  is discharged from the heat storage tank  20  to release heat, the region of the low temperature portion  20 L decreases, and the temperature boundary  20 B falls. 
     The operation management apparatus  1  is an apparatus for controlling cold water supply by the heat source system  2 , and configured as a computer apparatus including a microprocessor unit  10 , a memory unit  11 , an input/output unit  12 , and a user interface unit  13 , for example. 
     The memory unit  11  stores predetermined computer programs for implementing functions  106 ,  107 ,  108 ,  109  described later in  FIG. 2 . The microprocessor unit  10  reads and executes those computer programs to implement the functions  106  to  109 . 
     The input/output unit  12  is an apparatus for electrically connecting the operation management apparatus  1  and the heat source system  2  to each other. The user interface unit  13  is an apparatus for exchanging information with a user (for example, a system administrator) that manages the operation management apparatus  1 . The user interface unit  13  includes an information input apparatus for the user to input the information into the operation management apparatus  1 , and an information output apparatus for providing the information from the operation management apparatus  1  to the user. Examples of the information input apparatus include a keyboard, a mouse, a touch panel, a voice input apparatus, and a line-of-sight detection apparatus. Examples of the information output apparatus include a display, a printer, and a voice synthesis apparatus. Incidentally, the operation management apparatus  1  can also provide the information to the user by using an e-mail or the like. 
     The operation management apparatus  1  is electrically connected via the input/output unit  12  to each primary side water feed pump  21 , each chiller  22 , the secondary side water feed pump  23 , and each of the temperature detection units  24 ,  25 . The operation management apparatus  1  receives a temperature signal measured by each of the temperature detection units  24 ,  25 , and creates operation control data according to the operation plan, to control each primary side water feed pump  21 , each chiller  22 , and the secondary side water feed pump  23 . 
     Here, a primary side amount of cold heat Q1 to be supplied from each chiller  22  to the heat storage tank  20 , a secondary side amount of cold heat Q2 to be supplied from the heat storage tank  20  to the air conditioner  3 , an amount of heat storage Qs to the heat storage tank  20 , and an amount of heat release Qr from the heat storage tank  20  are given as follows. 
         Q 1 =ρ·C·W 1·( Tr−Ts )  [Formula 1]
 
         Q 2 =ρ·C·W 2·( Tr−Ts )  [Formula 2]
 
         Q 1= Q 2+ Qs   [Formula 3]
 
     Therefore, when Q1&gt;Q2, the amount of heat storage is Qs (Qs=Q1−Q2). 
         Q 2= Q 1+ Qr   [Formula 4]
 
     Therefore, when Q2&gt;Q1, the amount of heat release is Qr (Qr=Q2−Q1). 
     In the above formulas, ρ [kg/m3] is a density of the cold water, and C [J/(kg·° C.)] is a specific heat of the cold water. Tr [° C.] is the cold water return temperature, Ts [° C.] is the cold water feed temperature, W1 [m3/s] is a primary side flow rate (a water feed flow rate from the chiller  22  to the heat storage tank  20 ), W2 [m3/s] is a secondary side flow rate (a water feed flow rate from the heat storage tank  20  to the air conditioner  3 ). 
     The operation management apparatus  1  uses the predicted cold water return temperature Tr, the estimated heat storage capacity, weather data such as a temperature and a humidity by a weather forecast for an operation target date of the chiller  22  that is the heat source device, and demand prediction data of the amount of cold heat relating to the air conditioner  3  and the like, to create an operation plan, and controls driving of the chiller  22  and the like in accordance with the operation plan, as described later. 
       FIG. 2  is a block diagram illustrating a system configuration example of the operation management apparatus  1 . The operation management apparatus  1  includes a weather data management unit  101 , an operation result data management unit  102 , a demand prediction data management unit  103 , a device specification and device characteristics data management unit  104 , a data input apparatus  105 , a cold water return temperature prediction unit  106 , a heat storage capacity (amount of releasable heat) estimation unit  107 , an operation plan creation unit  108 , an operation control data creation unit  109 , an output display unit  110 , and a heat source device control unit  111 , for example. 
     The weather data management unit  101  is configured to be capable of using weather forecast data delivered by, for example, Japan Meteorological Agency or a weather forecast service company, and manages the weather forecast on a target date of the operation plan. The weather forecast includes temperature and humidity, for example. If necessary, an amount of solar radiation, a wind speed, and a wind direction may be included. Hereinafter, the data managed by the weather data management unit  101  may be referred to as weather data  101 . 
     The operation result data management unit  102  manages the operation result data of the chiller  22  that is the heat source device in the heat source system  2 , and each apparatus relating to the heat storage tank  20  and the air conditioner  3 . The operation result data is configured to associate the measurement date and time and the like with measurement values such as the amount of cold heat, the temperature, the humidity, and the flow rate relating to the chiller  22 , the heat storage tank  20 , the air conditioner  3 , and the like, for example. Hereinafter, the data managed by the operation result data management unit  102  may be referred to as operation result data  102 . 
     The demand prediction data management unit  103  manages the demand prediction data predicting the amount of cold heat and the like in a demand side such as the air conditioner  3 . Hereinafter, the data managed by the demand prediction data management unit  103  may be referred to as demand prediction data  103 . 
     The device specification and device characteristics data management unit  104  manages device specification and device characteristics data relating to the chiller  22  and the heat storage tank  20 . The device characteristics include energy consumption characteristics, and a power unit price, for example. Hereinafter, the data managed by the device specification and device characteristics data management unit  104  may be referred to as device specification and device characteristics data  104 . 
     The data input unit  105  is a function that takes in the data of each of the data management units  101 ,  102 ,  103 ,  104  described above, and provides the data to each of the process units  106 ,  107 ,  108 ,  109 . 
     The cold water return temperature prediction unit  106  is a function that uses the weather data  101  and the operation result data  102  to predict the cold water return temperature at a scheduled heat release time on an operation plan target date. In the following description, the operation plan target date may be referred to as an operation plan date, and the scheduled heat release time may be referred to as a heat release time. 
     The heat storage capacity estimation unit  107  is a function that uses the cold water return temperature predicted by the cold water return temperature prediction unit  106 , and the device specification and device characteristics data  104 , to estimate the heat storage capacity (amount of releasable heat) required during operation control based on the operation plan. 
     The operation plan creation unit  108  is a function that uses the estimated heat storage capacity, the demand prediction data  103 , and the device specification and device characteristics data  104 , to create the operation plan for heat storage or heat release on the operation plan target date. The operation control data creation unit  109  is a function that uses the created operation plan and the device specification and device characteristics data  104 , to create the data for controlling driving of the chiller  22  as the heat source device. Incidentally, during operation control of the chiller  22 , it is necessary to control the water feed pumps  21 ,  23 , and the like. Here, it is described assuming that control data relating to those additional apparatuses are also included in the operation control data. 
     The output display unit  110  is a function generated by using the user interface unit  13 , and displays the operation plan created by the operation plan creation unit  108 , the operation control data created by the operation control data creation unit  109 , a result of the operation plan, and the like. The heat source device control unit  111  is a function that outputs the operation control data created by the operation control data creation unit  109  to the chiller  22  that is a control target, and is generated by using the input/output unit  12 . 
       FIG. 3  is a flowchart illustrating a process of creating the operation plan. The cold water return temperature prediction unit  106  of the operation management apparatus  1  predicts the cold water return temperature at the scheduled heat release time on the operation plan target date, based on the weather data  101  and the operation result data  102  (S 10 ). A prediction procedure of the cold water return temperature is described later with reference to  FIG. 4 . 
     The heat storage capacity estimation unit  107  estimates a heat storage capacity Qsp and an amount of releasable heat Qrp of the heat storage tank  20  at the time of operation planning, based on the predicted cold water return temperature (S 11 ). “At the time of operation planning” means when the operation control of the heat source system  2  is performed in accordance with the operation plan. 
     The heat storage capacity Qsp and the amount of releasable heat Qrp are given by Formula 5. In Formula 5, V [m3/s] is a capacity of the heat storage tank  20 . 
         Qsp=Qrp=ρ·C·V ·( Tr−Ts )  [Formula 5]
 
     The operation plan can be divided into a heat storage plan for storing heat for the heat storage capacity in the heat storage tank  20 , and a heat release plan for releasing heat for the amount of releasable heat from the heat storage tank  20 . In the heat storage plan, heat is stored using nighttime power that is inexpensive. For this reason, for the heat storage plan, a time zone in which a cold heat unit price is low is set in a period from 0:00 to 8:00, for example. On the other hand, in the heat release plan, a time zone in which the chiller  22  is operated and the air conditioner  3  is used is set. For example, in a period from 8:00 to 24:00, a higher charge time at which the cold heat unit price is high is set for the heat release plan. 
     The operation plan creation unit  108  uses the weather data  101 , the demand prediction data  103 , and the device specification and device characteristics data  104 , to calculate the cold heat unit price of a scheduled heat storage time (in the heat release plan, the scheduled heat release time) (S 12 ). A calculation procedure of the cold heat unit price is described later with reference to  FIG. 6 . 
     The operation plan creation unit  108  evaluates a remaining amount of heat storage before execution of the operation plan (S 13 ), and determines whether or not it is necessary to correct the heat storage capacity Qsp and the amount of releasable heat Qrp that are estimated in step S 11 , based on the evaluated remaining amount of heat storage (S 14 ). 
     There may be a case where the chiller  22  has operated or the air conditioner  3  has operated before the time at which execution of the operation plan is scheduled. In this case, heat that has not been assumed in step S 11  has been stored in the heat storage tank  20 , or heat release that has not been assumed in step S 11  has already been performed. Therefore, there is a possibility that an error occurs in an estimation result in step S 11 . 
     Therefore, the operation plan creation unit  108  evaluates the remaining amount of heat storage, based on the operation result data  102  (S 13 ), and determines whether or not correction is necessary for the estimation result in step S 11  (S 14 ). The operation plan creation unit  108 , when determining that correction is necessary (S 14 : YES), corrects the heat storage capacity or the amount of releasable heat (S 15 ), and implements the operation plan (S 16 ), and then ends the present process. 
     On the other hand, the operation plan creation unit  108 , when determining that correction is not necessary (S 14 : NO), implements the operation plan without correcting the heat storage capacity or the amount of releasable heat (S 16 ), and then ends the present process. 
     When the heat storage plan is corrected, operation time of the chiller  22  is allocated until the set heat storage capacity is reached, in order of the time at which the cold heat unit price is low. Thus, the heat produced in the time zone in which the electricity price is low can be stored in the heat storage tank  20  for the heat storage capacity. When the heat release plan is corrected, operation stop time of the chiller  22  is allocated until the set amount of releasable heat is reached, in order of the time at which the cold heat unit price is high. Thus, the heat of the heat storage tank  20  can be released in the time zone in which the electricity price is high, and operation of the chiller  22  can be stopped to reduce the electricity bill. 
       FIG. 4  is a flowchart illustrating an example of a process of predicting the cold water return temperature described in step S 10  in  FIG. 3 . The cold water return temperature prediction unit  106  sets data for searching data necessary for predicting the cold water temperature from the operation result data  102  (S 20 ). Specifically, the cold water return temperature prediction unit  106  sets the date and time, predicted outside air temperature, predicted outside air humidity, and the like relating to the operation plan date that is a prediction target for the cold water return temperature, as data to be searched. The data to be searched can also be referred to as a search condition or an operation result data extraction condition. 
     The cold water return temperature prediction unit  106  initializes a variable I for switching a data search range (S 21 ), and increments the variable I by one (S 22 ). The cold water return temperature prediction unit  106  searches the operation result data  102  within the search range (S 23 ), and extracts the data that meets all the following extraction conditions (S 24  to S 28 ). Inspection order of each of the extraction conditions does not matter. 
     A first extraction condition is whether or not a season code to which the extracted operation result data  102  belongs and a season code to which the operation plan target date belongs are the same as each other (S 24 ). The codes are set for each season beforehand, such as the season code “1” for from January to March, the season code “2” for from April to June, the season code “3” for from July to September, and the season code “4” for from October to December, for example. 
     A second extraction condition is whether or not a day of week code of the extracted operation result data  102  and a day of week type code of the operation plan target date are the same as each other (S 25 ). The codes are set in advance in accordance with a day of week type, such as the day of week type code “1” for Monday that is the beginning of the week, the day of week type code “2” for from Tuesday to Friday, and the day of week type code “3” for Saturday, Sunday, and national holidays, for example. 
     A third extraction condition is whether or not an operation time of the extracted operation result data  102  is within the scheduled heat release time plus-minus of [hours “on the operation plan target date (S 26 ). 
     A fourth extraction condition is whether or not the outside air temperature of the extracted operation result data  102  is within the predicted outside air temperature plus-minus σ2 [ ° C.] at the scheduled heat release time on the operation plan target date (S 27 ). 
     A fifth extraction condition is whether or not the outside air humidity of the extracted operation result data  102  is within the predicted outside air humidity plus-minus σ3[%] at the scheduled heat release time on the operation plan target date (S 28 ). The above-described σ1, σ2, σ3 are values indicating similarity allowable ranges of parameters under each extraction condition. 
     The operation result data  102  that meets all of the first to fifth extraction conditions is the data in which the environmental condition is similar to the environmental condition (prediction value) at the scheduled heat release time on the operation plan target date. The operation result data  102  under the similar environmental condition corresponds to “predetermined operation result data.” The predetermined operation result data  102  is useful for predicting the cold water return temperature at the scheduled heat release time on the operation plan target date. 
     The cold water return temperature prediction unit  106  determines whether or not the number of extracted items of the predetermined operation result data  102  obtained by this search is greater than zero and less than a predetermined upper limit value N (S 29 ). The cold water return temperature prediction unit  106 , when determining that the number of extracted items of the predetermined operation result data  102  is one or more and less than N (S 29 : YES), for example, calculates an average value of those less than N predetermined operation result data  102 , to predict the cold water return temperature at the scheduled heat release time on the operation plan target date (S 31 ). Instead of obtaining a simple average value, for example, weighting may be added for each parameter to calculate a weighted average. In addition, the values of the similarity allowable ranges σ1 to σ3 can be changed in accordance with the operation plan target date and the scheduled heat release time, and prediction accuracy specified by the user, for example. The values of the similarity allowable ranges σ1 to σ3 can be changed by reading a fixed value that matches a change condition or a table prepared in advance, or by calculation using a similarity allowable range calculation formula prepared in advance. 
     The cold water return temperature prediction unit  106 , when none of the predetermined operation result data  102  can be extracted or when the upper limit value N or more predetermined operation result data  102  are extracted (S 29 : NO), changes a search range αi (S 30 ), and returns to step S 21  and searches the operation result data  102  again. For example, i varies in a range from 1 to 3. 
       FIG. 5  illustrates an example of the operation result data  102  to be referenced during cold water return temperature prediction described in  FIG. 4 . Examples of items of the operation result data  102  include a season code C1, a date, a day of week, a day of week type code C2, a time C3, an outside air temperature C4, an outside air humidity C5, and a cold water return temperature C6. The operation result data  102  may include an item other than the items indicated in  FIG. 5 . 
     Here, for example, it is assumed that the operation plan target date that is a prediction target for the cold water return temperature is September 25 (Thursday), the predicted heat release time is 15:00, the predicted outside air temperature is 24.5[° C.], the predicted outside air humidity is 40[%], σ1=2 [hours], σ2=1.5[° C.], and σ3=10[%]. 
     The operation result data  102  stores data A1 for previous 24 hours a day for a plurality of days. In a range A1, data in which the season code C1 is “3” (from July to September) are data in a range A2 and data in a range A3, for example. Data in which the day of week type code C2 is “2” (Tuesday to Friday) are data in the ranges from A1 to A3, for example. Among the data in the ranges from A1 to A3, data that match the condition of the season code C1 are data in the ranges A2 and A3. 
     Data in which the time C3 is a predetermined range (13:00 to 17:00) of the scheduled heat release time are data D3, D4, D5. Among these data D3 to D5, the data D4 and D5 satisfy both conditions of the season code C1 and the day of week type code C2. 
     Data that satisfy the condition of the outside air temperature C4 (23 to 25° C.) are data D6, D7, D8, D9. Among the data D6 to D9, some data of the data D9 satisfy all of the condition of the season code C1, the condition of the day of week type code C2, and the condition of the time C3. 
     Data that satisfy the condition of the outside air humidity C5 (30 to 50%) are data D10. Some of the data D10 satisfy all of the condition of the season code C1, the condition of the day of week type code C2, the condition of the time C3, and the condition of the outside air temperature C4. 
     In the example of  FIG. 5 , data that satisfy all conditions of the parameters C1 to C5 are data D11. The data D11 includes two data, the data of September 18 (Thursday) 16:00 and the data of the same date 17:00. The cold water return temperature prediction unit  106  extracts these two data as the predetermined operation result data similar to the environmental condition at the scheduled heat release time on the operation plan target date for which the cold water return temperature is tried to be predicted. 
     The cold water return temperature prediction unit  106  uses the cold water return temperatures C6 of these two extracted data to predict the cold water return temperature at the scheduled heat release time on the operation plan target date. The cold water return temperature prediction unit  106 , for example, calculates an average value of the cold water return temperatures of the two data, and obtains a value of 9.645° C. (=(10.03+9.26)/2). This 9.645° C. is the cold water return temperature predicted by the cold water return temperature prediction unit  106 . 
       FIG. 6  illustrates an example of a procedure content of cold heat unit price calculation (S 12 ) described in  FIG. 3 . The operation plan creation unit  108  reads the predicted outside air temperature and predicted outside air humidity at an operation plan target time from the weather data  101 , and calculates a wet bulb temperature (S 120 ). 
     The operation plan creation unit  108  estimates an operation state of each chiller  22 , and sets an amount of cold heat and a load factor (S 121 ). At the time of heat storage planning, based on the device specification and device characteristics data  104 , the operation plan creation unit  108  assumes a state in which the chiller  22  is operated at the rated load or the most efficient load at each time of the heat storage plan target time. At the time of heat release planning, based on the demand prediction data  103 , the operation plan creation unit  108  assumes a state in which the chiller  22  is operated to satisfy the predicted demand amount of cold heat at each time of the heat release plan target time. In this way, the operation plan creation unit  108  sets the amount of cold heat and the load factor for each operation plan target time (S 121 ). 
     The operation plan creation unit  108  uses a result of warm bulb humidity calculation and energy consumption characteristics included in the device specification and device characteristics data  104 , to calculate power consumption at each time (S 122 ). Finally, the operation plan creation unit  108  uses a calculation result of the power consumption and a power unit price included in the device specification and device characteristics data  104  to calculate a power cost at each time, and calculates the cold heat unit price from the calculation result (S 123 ). Here, the cold heat unit price indicates a cost for a unit amount of cold heat. As described above, based on the cold heat unit price at each time, order of priority for determining a heat storage time and a heat release time at the time of operation planning is determined. When there are multiple chillers  22 , the device specification and device characteristics data  104  of each chiller  22  is considered. 
       FIG. 7  illustrates an example of power consumption characteristics of the chiller  22 . The power consumption characteristics can be used during calculation of the power consumption in step S 122  in  FIG. 6 . In  FIG. 7 , the vertical axis indicates the power consumption, and the horizontal axis indicates the load factor. Each line graph indicates a wet-bulb temperature. As illustrated in  FIG. 7 , the power consumption is determined by the load factor for each wet-bulb temperature. The load factor is set in step S 121  in  FIG. 6 , as described above. 
       FIG. 8  illustrates an example of the power unit price. The power unit price illustrated in  FIG. 8  can be used when the power cost and the cold heat unit price are calculated in step S 123  in  FIG. 6 . In  FIG. 8 , the vertical axis indicates the power unit price, and the horizontal axis indicates the time. Among bar graphs in FIG.  8 , the hatched bar graph indicates the power unit price in a summer season, and the outlined bar graph indicates the power unit price in seasons other than the summer season. 
     As illustrated in  FIG. 8 , in general, the power unit price is higher in the summer season, and lower in the other seasons. In addition, in general, the power unit price at nighttime (for example, a time zone from 22:00 to 7:59) is low, and the power unit price at daytime (for example, a time zone from 8:00 to 21:59) is high. Further, in the summer season, the power unit price at a power demand peak time zone (for example, a time zone from 13:00 to 15:59) is particularly high. Incidentally, the graphs illustrated in  FIGS. 7 and 8  are examples for understanding the present example, and the present example is not limited to the illustrated examples. 
       FIG. 9  illustrates an example of the operation plan created by the operation management apparatus  1 . In  FIG. 9 , the vertical axis indicates the amount of cold heat, and the horizontal axis indicate the time. The outlined bar graph indicates the amount of heat release. The black bar graph indicates the amount of cold heat due to operation of the chiller  22 . The hatched bar graph indicates the amount of heat storage. The thick polygonal line on which white ellipses are placed indicates the predicted amount of heat demand. The polygonal line indicated as a series of outlined ellipses indicates the remaining amount of heat storage of the heat storage tank  20 . 
     In the heat storage plan, the heat storage capacity estimated by predicting the cold water return temperature is allocated to store heat at the time at which the cold heat unit price is low. In the example of  FIG. 9 , inexpensive power at 6:00 and 7:00 is used to operate the chiller  22 , and heat is stored in the heat storage tank  20 . 
     After the heat storage is completed in the time zone in which the unit price is low, the operation management apparatus  1  operates the chiller  22  in accordance with the predicted amount of heat demand. When the scheduled heat release time set in the heat release plan arrives, the operation management apparatus  1  releases heat from the heat storage tank  20 , and shortens the operation time of the chiller  22 . In the example of  FIG. 9 , each of 15:00 and 16:00 at which the cold heat unit price is high is the scheduled heat release time. At the scheduled heat release time, all or some of the predicted amount of heat demand can be satisfied by releasing heat from the heat storage tank  20 , and the operation time and the load factor of the chiller  22  can be reduced by that amount. 
     According to the present example thus configured, it is possible to predict the return temperature Tr of the cold water returning from the air conditioner  3  to the heat source system  2 , estimate the heat storage capacity of the heat source system  2 , based on the predicted cold water return temperature, and create the operation plan for the heat source system  2 , based on the estimated heat storage capacity. Therefore, according to the present example, heat stored in the heat storage tank  20  can be efficiently used. 
     According to the present example, it is possible to operate the chiller  22  in the time zone in which the cold heat unit price is low to store heat in the heat storage tank  20 , and stop or reduce operation of the chiller  22  in the time zone in which the cold heat unit price is high. Therefore, according to the present example, energy saving operation is possible. 
     Incidentally, the present invention is not limited to the above-described embodiment. Those skilled in the art can perform various additions and modifications within the scope of the present invention. In the example, a case has been described where cold water is supplied to the air conditioner for cooling; however, the present invention can also be applied to heating. In this case, as the heat source device of the heat source system, a hot heat source device such as a boiler or a heat pump may be used. Further, a configuration may be used in which a chiller and a hot heat source device are combined as the heat source device. 
     REFERENCE SIGNS LIST 
     
         
           1 : heat source system operation management apparatus,  2 : heat source system,  3 : air conditioning apparatus,  20 : heat storage tank,  22 : chiller,  24 : cold water feed temperature detection unit,  25 : cold water return temperature detection unit