Heat source control system and control method

Abstract

Reduce the number of calculations required to optimize the energy consumption of the entire heat source system. [Solution] A heat source control system 100 includes an air conditioning load 104, a supply header 102 that sends chilled or hot water to the air conditioning load 104, a return header 103 that receives chilled or hot water from the air conditioning load 104, a plurality of heat source units 101 including heat source equipment 11 connected via pipes to the supply header 102 and the return header 103, and a control device 105. The control device 105 determines control target values ​​for the chilled or hot water flow rate and chilled or hot water outlet temperature for each heat source unit so as to optimize performance indicators such as overall energy consumption for the plurality of heat source units 101. In this optimization calculation, heat source units 101 including the same type of heat source equipment 11 are grouped together, and an exhaustive search is performed on combinations of chilled or hot water flow rate and chilled or hot water outlet temperature patterns for each group to determine control target values ​​for the chilled or hot water flow rate and chilled or hot water outlet temperature for each heat source unit 101 so as to optimize the overall performance indicator.

Description

[Technical Field]

[0001] The present invention relates to a heat source control system and a control method for an air conditioning facility equipped with a plurality of heat sources. [Background technology]

[0002] Conventionally, air conditioning equipment installed in buildings such as residential areas and factories, which have multiple air conditioning loads equipped with heat exchangers that exchange heat with the conditioned air, employs a heat source control system to adjust the amount of refrigeration in response to seasonal and building heat load fluctuations. However, when there are a large number of air conditioning loads, for example, adjusting the amount of refrigeration with a single large heat source unit (refrigeration unit) can be difficult. Even if adjustment is possible with a single unit, partial load characteristics can be poor. To address this situation, multiple heat source units, including heat source units, are installed and their operation or shutdown is controlled according to the amount of air conditioning load. Each heat source unit includes a chilled water pump (primary pump), a cooling tower, and a cooling water pump in addition to the heat source unit. The heat source control system increases or decreases the number of operating heat source units depending on operating conditions, such as load flow rate or load heat quantity.

[0003] Furthermore, as a method of controlling the number of operating heat source units using the above-mentioned heat source control system, in addition to controlling the start and stop of the heat source machine (refrigeration machine) itself, the idea of ​​building a heat source system that aims to further save energy as a system control item is becoming widespread, such as controlling the amount of refrigeration heat by controlling the compressor, controlling the cooling water temperature by changing the flow rate of the cooling water pump that transports cooling water circulating between the heat source machine and the cooling tower, and controlling the air volume of the cooling tower fan to control the degree of heat exchange between the outside air and the cooling water.For this reason, currently, studies are being conducted on how to combine the various variables of the equipment that make up the heat source machine to operate the entire system in response to the continuously changing outside air and air conditioning load, making optimal control of the heat source machine even more complex.

[0004] In light of this situation, the applicant has proposed a heat source control system that can calculate highly accurate control target values ​​by minimizing the amount of calculations and data in data tables during prior simulations and real-time control, while determining the minimum energy consumption of the cooling and heating source system using real-time measured values ​​and operating status information rather than prior estimated values ​​(Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6505589 Summary of the Invention [Problem to be solved by the invention]

[0006] The heat source control system described in Patent Document 1 performs real-time control during operation by continuously acquiring measurements of the outdoor wet-bulb temperature, heat generation capacity, and chilled water outlet temperature of each individual heat source unit at predetermined sampling times. It then performs real-time optimization calculations to determine the target chilled water flow rate and outlet temperature for each individual heat source unit so as to minimize the total energy consumption of each individual heat source unit. The heat source control system then calculates the target chilled water flow rate for the individual heat source unit's cooling water pump in real time based on the outdoor wet-bulb temperature, heat generation capacity, and chilled water outlet temperature acquired at predetermined sampling times during operation. In this way, the heat source control system described in Patent Document 1 changes the chilled water flow rate and outlet temperature for all operating heat source units to calculate the energy consumed by the entire heat source system, and then optimizes the water flow rate and outlet temperature to minimize energy consumption. However, while this method allows for highly accurate optimization, it has the drawback of requiring a huge number of calculations to find the optimal solution for energy consumption, and the number of calculations for energy consumption increases exponentially as the number of heat source machines increases.

[0007] Therefore, the main object of the present invention is to provide a control technology that can reduce the number of calculations compared to conventional methods when performing real-time calculations to optimize evaluation indicators such as the energy consumption of the entire heat source system. [Means for solving the problem]

[0008] The inventor of the present invention has intensively studied means for solving the problems of the conventional inventions described above, and has found that when calculating evaluation indicators such as the energy consumed by the entire heat source system by changing the chilled / hot water flow rate and chilled / hot water outlet temperature of all operating heat source units, the number of calculations can be reduced compared to the conventional method by assuming that the chilled / hot water flow rate and chilled / hot water outlet temperature are the same for heat source units of the same type and omitting the calculations. Based on this finding, the inventor has come to the conclusion that the problems of the conventional inventions can be solved, and has completed the present invention. Specifically, the present invention has the following configuration or steps.

[0009] A first aspect of the present invention relates to a heat source control system. The heat source control system according to the present invention comprises an air conditioning load, a forward header, a return header, multiple heat source units, and a control device. The air conditioning load is located on the secondary side. This air conditioning load may be provided with multiple heat exchangers that exchange heat with the air-conditioned air. The forward header sends out chilled water or hot water (hereinafter collectively referred to as "chilled or hot water") toward the air conditioning load. The return header receives the chilled or hot water sent from the air conditioning load. The multiple heat source units are located on the primary side, and each is connected to the forward header via a chilled or hot water primary forward pipe and to the return header via a chilled or hot water primary return pipe. Each heat source unit also includes a primary chilled or hot water pump and a heat source machine. The primary chilled or hot water pump controls the flow rate of the chilled or hot water in the chilled or hot water primary return pipe. A heat source machine (e.g., a chiller or a heater) cools chilled water or heats hot water delivered from a primary chilled / hot water pump via a primary chilled / hot water return pipe, and delivers the resulting chilled / hot water to a feed header via a primary chilled / hot water feed pipe. A control device controls multiple heat source units, each equipped with a heat source machine. The control device executes optimization calculations. The optimization calculations calculate an overall performance index (an index of energy consumption, running costs, or CO2 emissions) for the multiple heat source units, and determine, for each heat source unit, a control target value for the chilled / hot water flow rate delivered from the primary chilled / hot water pump to the heat source machine and a control target value for the chilled / hot water outlet temperature delivered from the heat source machine to the primary chilled / hot water feed pipe, so as to optimize the overall performance index for the multiple heat source units. In this optimization calculation, heat source units including the same type of heat source machine are considered to be in the same group. Then, for each group of heat source units, an exhaustive search is performed on multiple combinations of chilled / hot water flow rate patterns and chilled / hot water outlet temperatures, and an evaluation index for each combination is calculated. Then, the control target values ​​of the chilled / hot water flow rate and the chilled / hot water outlet temperature for each heat source unit are determined so that the evaluation index for all of the heat source units becomes an optimum value.

[0010] The evaluation index for which the present invention seeks an optimal solution is not limited to the energy consumption (unit: kWh, etc.) of the entire heat source system, but can also be the running cost (unit: yen, dollar, etc.) or the CO2 emissions (unit: kg-CO2, etc.). The energy consumption (kWh) can be calculated by power (kW) x time (h). The running cost (e.g., yen) can be calculated by energy consumption (kWh) x energy unit price (yen / kWh). The CO2 emissions can be calculated by energy consumption (kWh) x CO2 emission coefficient (kg-CO2 / kWh). As such, since the energy consumption, running cost, and CO2 emissions are all interrelated evaluation indexes, the control target values ​​of the chilled / hot water outlet temperature and chilled / hot water flow rate may be determined based on which evaluation index is optimized. Furthermore, the power source differs depending on the type of heat source machine. Constant-speed turbo chillers, inverter-controlled turbo chillers, air-cooled heat pumps, screw chillers, and exhaust heat recovery chillers are electrically powered, but absorption chiller / heat generators are internal combustion engine-powered using heavy oil or gas (city gas, propane). Therefore, when there are heat source machines with different power sources, in order to compare energy consumption in different units, such as electricity consumption and heavy oil or gas consumption, each can be converted into primary energy (MJ) and used as an evaluation index.

[0011] As described above, in the heat source control system according to the present invention, when calculating the energy consumed by the entire heat source system by changing the chilled / hot water flow rate and chilled / hot water outlet temperature in all operating heat source units, heat source units of the same type are considered to be in the same group, and the chilled / hot water flow rate and chilled / hot water outlet temperature are calculated for each group. As a result, according to the present invention, the number of calculations required to find an optimal solution can be significantly reduced compared to conventional technology in which energy consumption was calculated for combinations of chilled / hot water flow rate and chilled / hot water outlet temperature patterns in all operating heat source units.

[0012] More specifically, for heat source units of the same type (system), the shape of the performance curve does not vary significantly, regardless of the manufacturer or the refrigeration capacity of each unit. Therefore, empirically, treating units of the same type as the same unit does not pose any significant practical problems. Furthermore, the JIS standard allows for a ±10% deviation from the performance curve for heat source unit performance. Furthermore, for example, cooling water temperature, which is closely related to the efficiency of heat source units, is typically measured primarily from the outside air wet-bulb temperature. However, because the measurement point is typically not near a cooling tower but rather a single representative location within the building, this does not necessarily accurately reflect the cooling water temperature for each unit. Therefore, this invention prioritizes reducing the number of optimization calculations over accurately measuring the chilled / hot water flow rate and chilled / hot water outlet temperature for each unit, thereby achieving a heat source control system that can be used rationally in practical applications.

[0013] In the heat source control system according to the present invention, the type of heat source equipment is two or more types selected from the group consisting of an inverter-controlled turbo chiller, a constant-speed turbo chiller, an absorption-type chilled water generator, an air-cooled heat pump, a screw chiller, and a heat recovery chiller. When the heat source equipment is an inverter-controlled turbo chiller, a constant-speed turbo chiller, an absorption-type chilled water generator, a screw chiller, or a heat recovery chiller, the heat source unit further includes a cooling tower that exchanges heat with outside air to cool the waste heat generated by the heat source equipment, and a cooling water pump that controls the flow rate of cooling water circulating between the cooling tower and the heat source equipment to transport the waste heat. Therefore, the energy consumption of these cooling towers and cooling water pumps is also calculated. On the other hand, when the heat source equipment is an air-cooled heat pump, the heat source unit does not include these cooling towers and cooling water pumps, so the calculation of the energy consumption of the cooling towers and cooling water pumps is omitted or calculated as zero. Of the above heat source models, only absorption-type hot and cold water generators and air-cooled heat pumps are capable of heating operation.

[0014] In the heat source control system according to the present invention, in the optimization calculation, the calculation of the evaluation index may be excluded for combinations that satisfy predetermined exclusion conditions. By setting the exclusion conditions in this way, the number of calculations of the evaluation index can be further reduced. Examples of the exclusion conditions are one or more of the following first to seventh conditions. First condition: When the temperature difference between the hot and cold water going to and from the heat source unit is below the specified lower limit. Second condition: When the load factor of the heat source unit exceeds a specified upper limit Third condition: When the load factor of the heat source unit is below a specified lower limit Fourth condition: When the flow rate on the primary and secondary sides exceeds the specified set value. Fifth condition: When the difference in heat value between the primary and secondary sides exceeds the specified set value. Condition 6: When the secondary supply temperature exceeds the specified allowable value. Condition 7: When the secondary supply temperature is below the specified allowable value

[0015] In the heat source control system according to the present invention, the number of patterns of the chilled / hot water flow rate and / or the number of patterns of the chilled / hot water outlet temperature used in the optimization calculation may be reduced based on the control target values ​​of the chilled / hot water flow rate and the control target values ​​of the chilled / hot water outlet temperature that were optimized in the previous optimization calculation, thereby further reducing the number of calculations of the evaluation index.

[0016] In the heat source control system according to the present invention, the number of patterns of chilled / hot water flow rates and / or the number of patterns of chilled / hot water outlet temperatures used in the optimization calculation may be increased or decreased depending on the number of groups. For example, when the number of groups to be calculated is small, the number of calculations required is reduced, so the accuracy of the optimization calculation can be improved by deliberately increasing the number of patterns of chilled / hot water flow rates and / or chilled / hot water outlet temperatures. Conversely, when the number of groups to be calculated is large, the number of calculations required is increased, so the number of optimization calculations can be adjusted by reducing the number of patterns of chilled / hot water flow rates and / or chilled / hot water outlet temperatures.

[0017] A second aspect of the present invention relates to a control method for a heat source control system. Similar to the system according to the first aspect described above, this heat source control system includes an air conditioning load, a supply header, a return header, multiple heat source units, and a control device. Each of the heat source units includes a primary chilled / hot water pump and a heat source machine. The control method includes a step of executing an optimization calculation. The optimization calculation is similar to that of the first aspect described above. Specifically, the control device calculates an evaluation index for the energy consumption, running costs, or CO2 emissions of the multiple heat source units as a whole, and determines, for each heat source unit, a control target value for the chilled / hot water flow rate sent from the primary chilled / hot water pump to the heat source machine and a control target value for the chilled / hot water outlet temperature sent from the heat source machine to the chilled / hot water primary supply pipe, so as to optimize the evaluation index for the multiple heat source units as a whole. In addition, in the optimization calculation, heat source units containing the same type of heat source equipment are grouped together, and for each group, an exhaustive search is performed on multiple combinations of chilled / hot water flow rate patterns and multiple combinations of chilled / hot water outlet temperatures to calculate the evaluation index for each combination, and the control target value of the chilled / hot water flow rate and the control target value of the chilled / hot water outlet temperature for each heat source unit are determined so that the evaluation index for all the multiple heat source units is the optimal value. [Effects of the Invention]

[0018] According to the present invention, when performing real-time calculations to optimize evaluation indices such as energy consumption of the entire heat source system, the number of calculations can be reduced compared to conventional methods. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 shows an overview of the features of the heat source control system according to the present invention. [Figure 2] FIG. 2 shows an example of the configuration of a heat source control system. [Figure 3] Figure 3 shows an example of the main flow of optimization calculations by a heat source control system. [Figure 4] Figure 4 shows an example of a subflow of optimization calculations by a heat source control system. [Figure 5]FIG. 5 shows the concept of upper and lower loop limits. [Figure 6] FIG. 6 shows an example of grouping according to the type of heat source machine. [Figure 7] FIG. 7 shows an example of an approximate formula used to calculate power. [Figure 8] FIG. 8 shows a specific example of the optimization calculation. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described below, but also includes appropriate modifications of the embodiments below within the scope obvious to those skilled in the art.

[0021] The present invention can be applied to a heat source control system equipped with a composite heat source consisting of multiple heat source units. The heat source control system according to the present invention can be used for both cooling and heating operations. Here, the explanation will be given using the cooling operation as an example. In the case of heating operation, the "cold water" described below can be read as "hot water" or "hot and cold water."

[0022] Here, each heat source unit is a group of components related to one heat source machine (refrigeration machine), and basically includes four pieces of equipment: the heat source machine, the primary chilled water pump, the cooling tower, and the chilled water pump. However, if the type of heat source machine is an air-cooled heat pump, the cooling tower and chilled water pump are not required, so these cooling tower and chilled water pump are omitted from the heat source unit. Also, a composite heat source refers to the entire system consisting of n heat source units (n is a positive integer greater than or equal to 2).

[0023] First, referring to FIG. 1, an overview of the features of the heat source control system according to the present invention will be described in comparison with the prior art. In particular, a specific example will be used for the description. As shown in FIG. 1, the heat source control system includes five heat source units R, each designated by their respective unit numbers R1, R2, R3, R4, and R5. Furthermore, of these five heat source units R, heat source units R1, R2, and R3 are all "constant-speed centrifugal chillers," and heat source units R3 and R4 are all "absorption-type chilled / hot water generators." The heat source control system performs calculations to determine the target control values ​​for the outlet temperature of the chilled water discharged from heat source unit R and the target control values ​​for the flow rate of the chilled water supplied to heat source unit R, so as to optimize the amount of energy consumed by the entire system. In this case, a full search is performed for multiple combinations of chilled water flow rate patterns and multiple combinations of chilled water outlet temperature patterns, and the amount of energy consumed by the entire system is provisionally calculated for each combination.From the provisionally calculated amounts of energy consumed, the control target values ​​for the chilled water outlet temperature and the chilled water flow rate are determined so that the amount of energy consumed becomes optimal.

[0024] In this case, in the example shown in Figure 1, the chilled water outlet temperatures to be searched for are five patterns: 7°C, 8°C, 9°C, 10°C, and 11°C, with a lower limit of 7°C and an upper limit of 11°C, in increments of 1°C. The chilled water flow rates to be searched for are six patterns: 100%, 90%, 80%, 70%, 60%, and 50%, in increments of 10%, with an upper limit of 100% and a lower limit of 50%. In such a case, the conventional algorithm would exhaustively search through five combinations of chilled water outlet temperatures and six chilled water flow rates for five heat source units R, so the number of calculations for the energy consumption of the entire system would be (5 x 6) 5 = 24.3 million times. Then, the optimal value is identified from the amount of energy consumption calculated in each of these 24.3 million calculations. As such, conventional algorithms required a huge number of calculations. If the number of heat source machines is n, the number of patterns for chilled water outlet temperature is N, and the number of patterns for chilled water flow rate is M, the number of calculations required is (N x M) n It can be defined as:

[0025] On the other hand, in the present invention, heat source units R of the same type are considered to be in the same group. That is, as shown in FIG. 1, heat source units R1, R2, and R3 are considered to belong to one group because they share the common type of "constant-speed centrifugal chiller." Similarly, heat source units R3 and R4 are considered to belong to one group because they share the common type of "absorption-type chilled / hot water generator." Then, for each group, a full search is performed on combinations of multiple patterns of chilled water flow rate and multiple patterns of chilled water outlet temperature, and the energy consumption of the entire system is provisionally calculated for each combination. From the provisionally calculated energy consumption, the control target values ​​of the chilled water outlet temperature and the chilled water flow rate that optimize the energy consumption are determined. That is, in such a case, the algorithm of the present invention exhaustively searches five patterns of combinations of chilled water outlet temperature and six patterns of chilled water flow rate for two groups, so the number of calculations of the energy consumption of the entire system is (5 × 6) 2 = 900 times. Then, the optimal value is identified from the amount of energy consumption calculated in each of these 900 calculations. While the number of calculations in the conventional algorithm described above was 24.3 million, the number of calculations can be reduced to 900 in accordance with the algorithm of the present invention. Note that, when the number of groups of heat source machines R is g, the number of patterns of chilled water outlet temperature is N, and the number of patterns of chilled water flow rate is M, the number of calculations required is (N x M) g It can be defined as:

[0026] Next, the configuration of a heat source control system according to one embodiment of the present invention will be described. The heat source control system may be either a primary pump system or a primary-secondary pump system. Below, the configuration of a primary-secondary pump system heat source control system will be described using FIG. 2. The configuration of the heat source control system shown in FIG. 2 is basically the same as the configuration shown in FIG. 1 of Patent Document 1 (Patent No. 6505589).

[0027] FIG. 2 shows an example configuration of a primary-secondary pump type heat source control system 100. The primary-secondary pump type heat source control system 100 employs a piping system that can optimize the bypass flow rate between headers by eliminating the need to make the chilled water flow rates on the chiller 11 (heat source machine R) side and the air conditioner 104 side identical, with a feed header 102 and a return header 103 as the boundary. That is, this heat source control system 100 includes a chilled water primary feed pipe 15 that connects the chiller 11 and the feed header 102, and a chilled water primary return pipe 16 that connects the return header 103 and the chiller 11. The pressure losses in the chilled water primary feed pipe 15 and the chilled water primary return pipe 16 are handled as heads. The heat source control system 100 also includes a primary chilled water pump 12 to circulate chilled water on the primary side. Furthermore, the heat source control system 100 is equipped with a chilled water secondary pump (85a, 85b) that is responsible for the total head of the pressure losses in the feed header 102, the chilled water secondary feed pipe 39, the chilled water secondary return pipe 41, and the heat exchanger section of the air conditioner 104 in order to circulate chilled water to the air conditioning load side such as the air conditioner 104.

[0028] As shown in Fig. 2, the heat source control system 100 includes n heat source units 101(1) to 101(n), a forward header 102, a return header 103, an air conditioner (AHU) 104, a real-time controller 105, and an outdoor temperature and humidity sensor 106 that measures the outdoor wet-bulb temperature. Here, the outdoor temperature and humidity sensor 106 outputs the measured outdoor wet-bulb temperature as a signal to the real-time controller 105. Note that in the example of Fig. 2, for simplicity, only one air conditioner (AHU) 104 is shown, but generally there are multiple air conditioners (AHU) 104 as the air conditioning load.

[0029] In this embodiment, the n heat source units 101 may differ in the performance of each element, but have the same or similar basic configuration. As will be described in detail later, the heat source units 101 differ depending on the type (method or model) of the chiller 11. However, here, the configuration of one heat source unit 101(n) will be described, and redundant explanations regarding each individual heat source unit 101 will be omitted. As shown in FIG. 2, the heat source unit 101(n) has a chiller 11 (heat source unit R), a primary chilled water pump 12, a cooling tower 13, and a chilled water pump 14.

[0030] Examples of the chiller 11 (heat source machine R) are an inverter-controlled turbo chiller, a constant-speed turbo chiller, an absorption-type hot and cold water generator, and an air-cooled heat pump. Other chillers such as a screw chiller can also be used as the chiller 11, and if partial load characteristics can be confirmed, an exhaust heat recovery chiller can also be used.

[0031] An inverter-controlled turbo chiller is a chiller whose main components are a compressor, evaporator, condenser, and expansion valve. By controlling the compressor's rotation speed with an inverter, it is possible to operate it optimally according to the load. This improves energy efficiency and maintains high performance even under partial load. Furthermore, the inverter also plays a role in suppressing inrush current at startup, reducing the burden on the power supply equipment.

[0032] A constant-speed centrifugal chiller is a standard centrifugal chiller equipped with a compressor, evaporator, condenser, and expansion valve, and the compressor operates at a fixed speed. The refrigerant circulation is designed to maximize efficiency under certain conditions. Constant-speed operation simplifies the system configuration and improves reliability.

[0033] An absorption chilled / hot water generator is a device that uses the absorption cycle to achieve a refrigeration effect, consisting of a system including a generator, absorber, evaporator, condenser, and heat exchanger. Water is used as the main refrigerant, and lithium bromide solution is used as the absorbent. The generator uses thermal energy supplied from a heat source (steam, hot water, etc.) to evaporate the refrigerant, and the cooling effect is achieved in the process of absorption by the absorber. This method makes effective use of waste heat and renewable energy, so it has a low environmental impact and is very quiet when operating.

[0034] An air-cooled heat pump is a refrigerator equipped with a compressor, air-cooled condenser, evaporator, and expansion valve, and uses outside air to provide heating, cooling, and hot water. The refrigerant absorbs heat from the outside air in the evaporator, is compressed by the compressor to become a high-temperature, high-pressure gas, and is then liquefied again in the air-cooled condenser, releasing heat. This cycle is repeated, allowing for efficient extraction of thermal energy from the air. As it is an air-cooled system, installation and maintenance are simple, and no piping or cooling water system is required, contributing to shorter construction times and reduced costs.

[0035] A screw chiller is a type of refrigeration equipment whose main components are a screw compressor, an evaporator, a condenser, and an expansion valve. The screw compressor compresses the refrigerant using two intermeshing spiral rotors. This method is highly efficient and reliable, and allows for stable operation over a wide load range. Screw chillers are suitable for medium- to large-sized air conditioning equipment and industrial cooling processes, and are also suitable for continuous operation.

[0036] A waste heat recovery chiller is a chiller that incorporates a system that effectively utilizes waste heat generated by other processes and equipment in addition to the normal refrigeration cycle. This device is equipped with a heat exchanger for waste heat recovery in addition to a compressor, evaporator, condenser, and expansion valve. By using waste heat from factories, power plants, etc. to heat or evaporate the refrigerant, the energy efficiency of the entire system is improved. This reduces power consumption and operating costs, while also contributing to a lighter environmental load. High energy-saving effects can be achieved by optimizing the system design according to the temperature and amount of waste heat.

[0037] The chiller 11 is connected to the supply header 102 by a chilled water primary supply pipe 15, and is also connected to the return header 103 by a chilled water primary return pipe 16. Here, the chilled water primary supply pipe 15 is a pipe on the primary side of the chilled water, and sends the chilled water cooled (referred to as "frozen") by the chiller 11 (heat source machine R) to the supply header 102. The chilled water primary return pipe 16 is also a pipe on the primary side of the chilled water, and when the chilled water whose temperature has increased through heat exchange in the air conditioner 104 returns to the return header 103, the return chilled water is sent from the return header 103 to the chiller 11.

[0038] Information on the chilled water outlet temperature SP (Set Point: set value) is input to the chiller 11 from the real-time controller 105. Information indicating the heat source operating state is output to the real-time controller 105 from the chiller 11 (heat source machine R).

[0039] A temperature sensor 17 that measures the chilled water outlet temperature of the chiller 11 is provided in the chilled water primary supply pipe 15. The temperature PV (Process Value: measured value) of the chilled water outlet temperature measured by the temperature sensor 17 is output to the real-time controller 105.

[0040] A flow meter 18, a primary chilled water pump 12, and a temperature sensor 19 are provided in this order in the chilled water primary return pipe 16, from the return header 103 toward the chiller 11 (heat source machine R). The flow meter 18 measures the chilled water flow rate sent from the primary chilled water pump 12 to the chiller 11. The temperature sensor 19 measures the chilled water inlet temperature of the chiller 11. The flow rate PV of the flow meter 18 is output to a real-time controller 105. The temperature PV of the chilled water inlet temperature measured by the temperature sensor 19 is also output to the real-time controller 105. The primary chilled water pump receives power via an inverter (INV). The inverter (INV) controls the frequency of the power supply to the primary chilled water pump 12 based on instructions from the real-time controller 105. This makes it possible to vary the rotation speed of the primary chilled water pump 12.

[0041] The chiller 11 is also connected to a cooling tower 13 via a circular cooling water pipe 21. The circular cooling water pipe 21 is connected to an inlet and an outlet of a heat exchanger, such as a condenser, that exchanges heat with the chiller 11, so that cooling water can be introduced and discharged. The cooling tower 13 is also equipped with a cooling tower fan, which exchanges heat between the chiller and outside air and the cooling water, thereby releasing heat and lowering the temperature of the cooling water. A chilled water pump 14 is provided in the path of the circular cooling water pipe 21 on the outlet side of the cooling tower 13. The conveying force of the cooling water pump 14 transports the cooling water, whose temperature has been increased by the exhaust heat of the chiller 11, from the chiller 11 to the cooling tower 13 through the cooling water pipe 21. The conveying force of the cooling water pump 14 also transports the cooling water, whose temperature has been lowered by heat exchange with outside air in the cooling tower 13, from the cooling tower 13 to the chiller 11 through the cooling water pipe 21.

[0042] The cooling tower 13 cools the cooling water, whose temperature has risen due to the exhaust heat from the chiller 11, by direct or indirect contact with outside air via a cooling tower fan. The cooling water pump 14 sends the cooling water cooled in the cooling tower 13 to the chiller 11. The cooling tower fan of the cooling tower 13 and the cooling water pump 14 each have an inverter (INV) as a power source for each motor. This makes the rotation speed of the cooling tower fan and the cooling water pump 14 variable.

[0043] In addition, the supply header 102 and the return header 103 are connected via a bypass path 31. By providing this bypass path 31, it is possible to absorb any imbalance in the flow rate between the primary and secondary sides and adjust the pressure and flow rate within the system, thereby enabling efficient circulation of the fluid.

[0044] As described above, the heat source control system 100 according to this embodiment is configured such that the primary side of the heat source machine R is composed of n heat source units 101, a forward header 102, a return header 103, a chilled water primary side forward piping 15 and a chilled water primary side return piping 16 connecting these, and a bypass path 31.

[0045] Meanwhile, on the secondary side of the heat source unit R in the heat source control system 100, a second forward header 83 is arranged downstream of the forward header 102, sandwiching secondary chilled water pumps 85a and 85b arranged in parallel. The forward header 102 and the second forward header 83 are connected by two short pipes, and secondary chilled water pumps 85a and 85b are provided in each of the short pipes.

[0046] Between the second supply header 83 and the return header 103, there are provided a chilled water secondary supply pipe 39 that connects the second supply header 83 to an air conditioner 104 (AHU), and a chilled water secondary return pipe 41 that connects the air conditioner 104 to the return header 103. Here, the chilled water secondary supply pipe 39 is the secondary side of the chilled water, and is a pipe that sends chilled water cooled by the chiller 11 (heat source machine R) from the second supply header 83 to the air conditioner 104. This chilled water secondary supply pipe 39 is provided with a temperature sensor 43 that measures the temperature of water sent to the air conditioning load made up of multiple air conditioners 104. Furthermore, the chilled water secondary return pipe 41 is the secondary side of the chilled water, and is a pipe that sends chilled water that has been heat exchanged in the air conditioner 104 and has its temperature increased from the air conditioner 104 to the return header 103. This chilled water secondary return pipe 41 is provided with a temperature sensor 51 that measures the temperature of the chilled water that returns to the return header 103 after heat exchange in the air conditioning load formed by multiple air conditioners 104, and a flow meter 53. The measured values ​​of each of the temperature sensors 43, 51 and the flow meter 53 are output to a real-time controller 105.

[0047] As such, in the heat source control system 100 of this embodiment, the secondary side of the heat source unit R is composed of a forward header 102, a return header 103, a second forward header 83, an air conditioner (AHU) 104, and piping connecting these.

[0048] The real-time controller 105 is configured with a control device such as a computer. The main device that configures the hardware of the real-time controller 105 is a PLC (Programmable Logic Controller) or the like. The real-time controller 105 comprehensively controls the operation of the heat source control system 100 by executing a program. For example, the real-time controller 105 performs variable flow rate control of the primary flow rate to adjust the flow rate of the primary chilled water, and control to change the setting of the chilled water outlet temperature of the heat source unit R. The real-time controller 105 also has a memory unit 107 that stores programs and various data tables. The memory unit 107 is, for example, a non-volatile semiconductor memory or a hard disk.

[0049] Next, we will explain one embodiment of a control method for the heat source control system 100. Fig. 3 is a main flow showing the control process of the heat source control system 100, and Fig. 4 is a subflow showing details of the loop lowest layer calculation shown in Fig. 3.

[0050] As shown in FIG. 3, information from each device and sensor constituting the heat source control system 100 is first input to the real-time controller 105 (step S1). Examples of information input to the real-time controller 105 include the operating status of the chiller 11 (heat source machine R) and its auxiliary machines, outdoor air conditions such as the outdoor wet-bulb temperature measured by the outdoor air temperature and humidity sensor 106, the chilled water temperature measured by each temperature sensor 17, 19, 43, and 51, and the chilled water flow rate measured by each flow meter 18 and 53. Note that Tcs (Chilled Supply Temperature) in FIG. 3 refers to the supply temperature of chilled water, which is the temperature of the chilled water cooled by the chiller 11 and supplied to the air conditioner 104, and corresponds mainly to the chilled water outlet temperature measured by the temperature sensor 17. Also, Tcr (Chilled Return Temperature) in FIG. 3 refers to the return temperature of chilled water, which is the temperature of the chilled water returning to the chiller 11 via the air conditioner 104, and corresponds mainly to the chilled water inlet temperature measured by the temperature sensor 19.

[0051] In addition, arbitrary setting conditions related to the operation of the heat source control system 100 are input to the real-time controller 105 (step S2). Examples of setting conditions include upper and lower limits for the heat quantity, temperature, flow rate, etc. of the heat source machine R, characteristic values ​​of each device such as the heat source machine R, pump, fan, etc., timer settings related to operation time, piping configuration, configuration of the heat source machine R (including the type of heat source machine R), and various calculation coefficients. Types of heat source machine R include, for example, inverter-controlled turbo chillers, constant-speed turbo chillers, absorption-type hot and cold water generators, and air-cooled heat pumps, and the user can also set any type. Note that if there is a heat source of the same type whose performance characteristics differ significantly from others, the heat source may not be grouped but input by the user, and a performance curve obtained from the manufacturer or the like may be used instead of a representative characteristic prepared in advance. In addition, the rated value of each device can be input as the specific value of the device. Examples of rated values ​​of each device include the cooling / heating capacity rated value (kW), the CP (primary pump) flow rate rated value (m 3 / h), CDP (cooling water pump) flow rate rating (m 3 / h), power (electricity, gas, heavy oil, etc.) rated value (kW, m 3 / h), CP (primary pump) power rating (kW), CDP (cooling water pump) power rating (kW), and CT (cooling tower fan) power rating (kW). In the present invention, heat source machines R of the same type are considered as one group and calculations of power, etc. are performed. At this time, for each group, setting values ​​such as upper and lower limits and coefficients of specific formulas to be used in calculations for the group can be input. Examples of setting values ​​for the group are upper and lower limits of flow rate (CP, CDP) (%), upper and lower limits of outlet temperature (°C), step width and change width (%) for upper and lower limits and flow rate / temperature calculation, CP power characteristics (coefficient of cubic function), CDP power characteristics (coefficient of cubic function), and CT power characteristics (coefficient of cubic function).

[0052] Next, the real-time controller 105 checks the status of the heat source control system 100 (step S3). Here, the real-time controller 105 checks the individual status of each heat source unit R, such as whether it is in operation, stopped, pre-cooling, or additional startup state. The real-time controller 105 also checks the group status for each group of heat source units R. That is, even among the multiple heat source units belonging to one group, there are heat source units with different individual statuses, such as operating units, stopped units, and units that have just started up. Therefore, when calculating the power for each group, the real-time controller 105 performs processing such as including operating heat source units in the calculation and excluding stopped heat source units from the calculation. The real-time controller 105 also determines whether there is a group of heat source units that requires settings other than the optimal control value, such as issuing an instruction value to operate the primary flow rate at the minimum flow rate, for example, for a group that includes a heat source unit that has just started up.

[0053] Next, the real-time controller 105 sets upper and lower limits for the loop calculation (step S4). The concepts of the loop upper and lower limits are shown in FIG. 5. The real-time controller 105 repeatedly searches for a combination of chilled water outlet temperature and chilled water flow rate that optimizes the amount of energy consumed and other factors throughout the system. Assume that the previous optimization calculation determined the combination of chilled water outlet temperature and chilled water flow rate that optimizes the amount of energy consumed and other factors. The next optimization calculation often does not significantly change the chilled water outlet temperature and chilled water flow rate determined in the previous optimization calculation. Therefore, in the current optimization calculation, it is advisable to narrow down the chilled water outlet temperature and chilled water flow rate patterns to be searched for in the current optimization calculation by referring to the set points (SPs) for the chilled water outlet temperature and chilled water flow rate determined in the previous optimization calculation. Specifically, the upper and lower limits for the loop calculation are set for the chilled water outlet temperature and chilled water flow rate patterns to be searched for in the current optimization calculation, centering on the optimal chilled water outlet temperature and optimal chilled water flow rate determined in the previous optimization calculation.

[0054] For example, in the example shown in FIG. 1, there are five chilled water outlet temperature patterns: 7°C, 8°C, 9°C, 10°C, and 11°C, with a lower limit of 7°C and an upper limit of 11°C. Here, assume that in the previous optimization calculation, the chilled water outlet temperature at which the overall system energy consumption, etc., was optimized was 9°C. Therefore, in the next optimization calculation, the chilled water outlet temperature at which the overall system energy consumption, etc., was optimized is likely to be around 9°C. Therefore, in the current optimization calculation, the range from the upper limit to the lower limit of the chilled water outlet temperature to be searched (the current SP movable range shown in FIG. 5) can be set narrower than the range from the maximum lower limit to the lower limit (the SP movable range shown in FIG. 5) based on the results of the previous optimization calculation. For example, if the chilled water outlet temperature was determined to be 9°C in the previous optimization calculation, the upper limit and lower limit of the chilled water outlet temperature can be set to 10°C and 8°C, respectively, in the current optimization calculation. As a result, the chilled water outlet temperature patterns will be limited to three patterns: 8°C, 9°C, and 10°C, and the search range in the optimization calculation will be narrowed, making it possible to reduce the number of calculations. As shown in Figure 5, the range of change in the upper and lower limit values ​​of the current optimization calculation, which is centered on the result of the previous optimization calculation, can be set arbitrarily by the user, for example, in step S2 described above.

[0055] In addition, to improve the accuracy of the optimization calculation, the number of patterns of the chilled water flow rate and / or the chilled water outlet temperature can be increased. For example, when the number of groups of heat source units to be calculated is small, the number of calculations required is small. In this case, the accuracy of the optimization calculation can be improved by increasing the number of patterns of the chilled water flow rate and / or the chilled water outlet temperature. For example, in the example shown in Figure 1, the chilled water outlet temperature patterns are five patterns in 1-degree increments: 7°C, 8°C, 9°C, 10°C, and 11°C. However, when the number of groups of heat source units is small, it is possible to increase the number of chilled water outlet temperature patterns to be searched, for example, to 10 patterns in 0.5-degree increments: 7°C, 7.5°C, 8°C, 8.5°C, 9°C, 9.5°C, 10°C, 10.5°C, 11°C, and 11.5°C. The same applies to the chilled water flow rate. Conversely, when the number of groups to be calculated is large, the number of calculations required increases. Therefore, the number of optimization calculations can be adjusted by reducing the number of patterns of the chilled water flow rate and / or the chilled water outlet temperature.

[0056] Next, the real-time controller 105 calculates the rated value for each group of heat source units R (step S5). The rated value for each group is basically calculated by adding up the rated values ​​of the heat source units R that are in operation in each group. FIG. 6 shows an example of grouping according to the type of heat source units R. The example in FIG. 6(a) shows a case where there are five heat source units R in the heat source control system, and all of the heat source units R are in operation. For example, the heat source units R1 and R2 are of the type "constant-speed centrifugal chiller," the heat source units R3 and R4 are of the type "absorption-type chilled / hot water generator," and the heat source unit R5 is of the type "inverter-controlled centrifugal chiller." Furthermore, the heat source units R1 to R5 have individual rated capacities of 1,758 kW, 1,406 kW, 879 kW, 879 kW, and 1,055 kW, respectively. In such a case, the real-time controller 105 considers the same type of heat source units R1 and R2 to be in the same group, and performs subsequent calculations assuming that the rated capacity of the group is 3,164 kW, which is the sum of the individual rated capacities of these heat source units R1 and R2. Similarly, the real-time controller 105 considers the same type of heat source units R3 and R4 to be in the same group, and performs subsequent calculations assuming that the rated capacity of the group is 1,758 kW, which is the sum of the individual rated capacities of these heat source units R3 and R4. Note that heat source unit R5 is not grouped because there are no heat source units of the same type in the system.

[0057] In addition, the example of Figure 6(b) shows a case where there are five heat source units R in the heat source control system, but only some of the heat source units R are in operation. In this case, the rated capacity of each heat source unit R1 to R5 is the same as that shown in Figure 6(a), but of these heat source units R1 to R5, only heat source units R1, R2, and R4 are in operation, and heat source units R2 and R4 are stopped. In this case, as in the example shown in Figure 6(a), heat source units R1 and R2 are grouped together, and heat source units R3 and R4 are grouped together, but in the group of heat source units R1 and R2, the rated capacity of the stopped heat source unit R2 is calculated as zero. Therefore, the rated capacity of the group of heat source units R1 and R2 is calculated as 1,758 kW, referring only to the individual rated capacity of the operating heat source unit R1. In addition, since heat source unit R5, which does not belong to a group, is also stopped, its rated capacity is calculated as zero.

[0058] Next, the real-time controller 105 reads out an approximation formula required for calculating the power of the heat source machine R, etc. (step S6). This approximation formula is created in advance based on the past operating records of the heat source machine R, etc., and indicates the tendency of the capacity of the heat source machine R, etc. Information about this approximation formula is stored in the memory unit 107 in the real-time controller 105.

[0059] FIG. 7 illustrates the concept of the approximation formula used here. As shown in FIG. 7, the approximation formula uniquely defines the correspondence between the load factor (%) and the power ratio for heat source unit R and its auxiliary equipment (primary chilled water pump, cooling water pump, and cooling tower fan). For example, the approximation formula for heat source unit R is created by dividing the chilled water temperature into patterns for each chilled water outlet temperature. In the example shown in FIG. 7, for a chilled water outlet temperature of 7°C, approximation formulas for a chilled water temperature of 20°C, a chilled water temperature of 26°C, and a chilled water temperature of 32°C are shown. Note that similar patterns are also used for a chilled water outlet temperature of 11°C. Similarly, approximation formulas uniquely defining the correspondence between the load factor (%) and the power ratio for the auxiliary equipment of heat source unit R are created. Here, the load factor is an index that indicates the load at which heat source unit R and its auxiliary equipment are operating relative to their maximum capacity (rated capacity). The real-time controller 105 calculates the load factor of each group of heat source units for each condition based on the allocated chilled water outlet temperature and chilled water flow rate. After identifying the load factor of the heat source units R, etc., the real-time controller 105 identifies the power ratio of the heat source units R, etc. corresponding to the load factor by referring to an approximation formula such as that shown in FIG. 7. The power ratio represents the ratio of actual power consumption (kW) to the rated value (rated output) of the heat source units R and their auxiliary units. Therefore, the real-time controller 105 can determine the power (kW) of each heat source unit R, etc. by multiplying the power ratio identified by referring to the approximation formula by the rated value of each heat source unit R, etc. In other words, the power (kW) can be calculated by multiplying the power ratio identified by referring to the approximation formula by the rated value of each heat source unit R, etc. When calculating the power (energy consumption) of each heat source machine R, etc., by multiplying the power ratio determined by referring to the approximate formula shown in Figure 7 by the rated value of each heat source machine R, etc., the performance curve of any heat source machine R, etc. can be used as long as it is the same type of heat source machine.In addition to creating an approximate formula based on the past operating history of the heat source machine R, etc., it is also possible to create an approximate formula from the performance curve of the heat source machine R, etc. that has been obtained as appropriate, and use it as a representative characteristic prepared in advance.

[0060] Next, the real-time controller 105 performs a power calculation for the entire system (i.e., a composite heat source consisting of multiple heat source units) (step S7). In this power calculation, a calculation (optimization calculation) is performed to determine what values ​​the control target values ​​of the chilled water outlet temperature and the control target values ​​of the chilled water flow rate should be set to for each of the multiple heat source units included in the system to optimize the amount of energy consumed, etc., for the entire system. For this reason, this power calculation is performed in the lowest layer of a multiple loop (N×M) that combines a loop corresponding to the number of patterns (N) of the chilled water outlet temperature with a loop corresponding to the number of patterns (M) of the chilled water flow rate. Furthermore, this power calculation needs to be performed as many times as there are groups of heat source units. Therefore, as explained with reference to FIG. 1, the number of times the power calculation in the lowest layer of the loop is performed is (N×M) where g is the number of groups of heat source units, N is the number of patterns of the chilled water outlet temperature, and M is the number of patterns of the chilled water flow rate. g This becomes:

[0061] FIG. 4 shows an example of a subflow of the power calculation (step S7) in the lowest loop shown in FIG. 3. When this power calculation starts, the real-time controller 105 first checks the current number of operating heat source machines R and checks the number of power calculations (steps S7-1 and S7-2). For example, if the number of operating heat source machines R becomes zero during the calculation of the lowest loop, the calculation of the multiple loops can be omitted. Therefore, it is preferable to check the number of operating heat source machines in the calculation of the lowest loop in each loop. Furthermore, if the result of checking the number of calculations shows that the number of required calculations exceeds a predetermined value, the calculation of the multiple loops may be stopped. For example, if the number of patterns for the chilled water outlet temperature and chilled water flow rate is too large, the number of calculations becomes enormous, and the calculation of the multiple loops will not be completed. Therefore, if the number of calculations exceeds a predetermined value, the calculation is stopped and the number of patterns is reset.

[0062] Next, real-time controller 105 calculates the total provisional chilled water flow rate on the primary side (step S7-3). For example, as shown in FIG. 1, assume that there are five heat source units R1 to R5 on the primary side, and that the heat source units including heat source units R1 to R3 are in the same group, and that the heat source units including heat source units R4 and R5 are in the same group. In this way, the number of groups (g) is 2. Also, assume that there are six chilled water flow rate patterns: 100%, 90%, 80%, 70%, 60%, and 50%. Also, in this loop's lowest-level calculation, the chilled water flow rates of the two groups are 50% and 100%, respectively. In this case, the total provisional chilled water flow rate is calculated as [(50 + 100) / (100 × g)] × 100 (%) (g is the number of groups). In this case, the total provisional chilled water flow rate on the primary side is 75%. The real-time controller 105 stores the calculated total provisional chilled water flow rate in the storage unit 107 .

[0063] Next, real-time controller 105 calculates the virtual temperature (chilled water inlet temperature of the heat source machine, chilled water secondary return temperature) and virtual flow rate in the case of forward flow (primary rich) (step S7-4(1)), or calculates the virtual temperature (chilled water inlet temperature of the heat source machine, chilled water secondary return temperature) and virtual flow rate in the case of reverse flow (secondary rich) (step S7-4(2)). Forward flow (primary rich) refers to a state in which the total value of the virtual chilled water flow rate on the primary side is relatively large compared to the secondary side, and conversely, reverse flow (secondary rich) refers to a state in which the total value of the virtual chilled water flow rate on the secondary side is relatively large compared to the primary side. Real-time controller 105 determines whether it is forward flow (primary rich) or reverse flow (secondary rich) by comparing the total value of the virtual chilled water flow rate on the primary side calculated in the previous step S7-3 with the measured value of the chilled water flow rate on the secondary side. Then, the real-time controller 105 separately calculates the virtual temperature and virtual flow rate when the system is in forward flow (primary rich) and the virtual temperature and virtual flow rate when the system is in reverse flow (secondary rich), and stores these results in the storage unit 107. This determines the chilled water inlet and outlet temperatures of the heat source machine.

[0064] Next, the real-time controller 105 calculates a provisional chilled water heat quantity and a provisional chilled water heat quantity ratio for each heat source machine (step S7-5). The provisional chilled water heat quantity of the heat source machine is calculated by: Heat quantity = inlet / outlet temperature difference of the heat source machine × flow rate. The inlet / outlet temperature difference of the heat source machine is the difference between the chilled water inlet and outlet temperatures of the heat source machine determined in step S7-4(1) or S7-4(1). The provisional chilled water heat quantity ratio is calculated by: Chilled water heat quantity ratio = chilled water heat quantity of the heat source machine / total chilled water heat quantity. The total chilled water heat quantity is the sum of the chilled water heat quantities of each heat source machine. The real-time controller 105 stores the provisional chilled water heat quantity and provisional chilled water heat quantity ratio calculated here in the memory unit 107. The real-time controller 105 also calculates the chilled water heat quantity of each group ÷ the rated heat quantity of each group = the load factor of each group to calculate the load factor of each group of the heat source machine.

[0065] Next, the real-time controller 105 determines whether or not a calculation exclusion condition is met (steps S7-6 to S7-13). If the calculation exclusion condition exemplified here is met, the subsequent processing (steps S7-14 to S7-20) is not performed and one loop of the lowest-level calculation is terminated. The calculation exclusion conditions exemplified here mainly relate to checking the operating conditions (range) of the heat source units, including the heat source equipment, checking the flow rate balance between the primary and secondary sides, checking the heat quantity balance, and checking the secondary feed temperature. By setting these calculation exclusion conditions in this lowest-level loop calculation, for example, physically impossible conditions can be excluded early, thereby eliminating unnecessary loop calculations. Examples of calculation exclusion conditions are given below, but it is not necessary to adopt all of the conditions exemplified below as calculation exclusion conditions, and additional exclusion conditions can also be added.

[0066] The first exclusion condition is when the temperature difference (ΔT) between the primary chilled water flowing to and from the heat source unit falls below a predetermined lower limit (step S7-6). In other words, if the difference (ΔT) between the temperature of the chilled water leaving the heat source unit and the temperature of the chilled water returning to the heat source unit falls below a predetermined lower limit, the system is deemed to be operating inefficiently, and subsequent power calculations are skipped. Maintaining an appropriate ΔT enables efficient operation of the heat source unit. Furthermore, if ΔT is too small, an excessive amount of water is required to achieve the required cooling capacity, which can result in wasteful pump power consumption or unstable operation of the heat source unit. Therefore, by setting the first exclusion condition, calculations under conditions where such problems may occur can be excluded. Note that this first exclusion condition applies only to heat source units that are in operation.

[0067] The second exclusion condition is when the load factor of the heat source machine is equal to or greater than a predetermined upper limit (step S7-7). The upper limit of the load factor of a heat source machine is generally 100% or close to it, but may be set slightly lower, for example, in the range of 95 to 100%, depending on the characteristics of the machine and a safety margin. By setting the second exclusion condition, the heat source machine can be protected from excessive load and the life of the machine can be extended. Furthermore, since many heat source machines operate most efficiently near their rated load, avoiding operation at excessive loads can avoid a decrease in energy efficiency, etc.

[0068] The third exclusion condition is when the load factor of the heat source machine is below a predetermined lower limit (step S7-8). It is generally preferable to set the upper limit of the load factor of a heat source machine to approximately 20-30% of its rated capacity, but this value can vary depending on the characteristics of the machine. Many heat source machines become unstable or their energy efficiency decreases when operated at an extremely low load factor. Operating a heat source machine at a low load factor can cause frequent start-stops, which can shorten the machine's lifespan. Furthermore, an extremely low load factor makes accurate temperature control difficult. Therefore, by setting the third exclusion condition, calculations under conditions where such problems may occur can be excluded.

[0069] The fourth exclusion condition is when the flow rate values ​​on the primary and secondary sides exceed predetermined set values ​​(step S7-9). Piping and pumps have maximum flow rate limits, and flow rates exceeding these limits are physically impossible. Furthermore, excessive flow rates can unnecessarily increase the power consumption of the pump, reducing the efficiency of the entire system, or disrupt the hydraulic balance of the entire system, causing control instability. For this reason, by setting the fourth exclusion condition, calculations under conditions where such problems may occur can be excluded.

[0070] The fifth exclusion condition is when the difference between the calorific values ​​of the primary and secondary sides exceeds a predetermined set value (step S7-11). Prior to this, the real-time controller 105 calculates the deviation between the provisional primary chilled water calorific value and the effective secondary chilled water calorific value (step S7-10). The provisional primary chilled water calorific value is the calorific value of the primary chilled water, calculated based on the design and operating conditions and assuming how much heat the primary side can remove. The effective secondary chilled water calorific value is the calorific value of the chilled water actually used effectively by the secondary side, and is a measured value used to evaluate the efficiency of the system based on the actual calorific value used for cooling. The real-time controller 105 determines whether the difference between the provisional primary chilled water calorific value and the effective secondary chilled water calorific value exceeds a predetermined set value. This predetermined set value is the maximum calorific value difference between the primary and secondary sides allowed by the system design and operation. Ideally, the heat output of the primary and secondary sides should be roughly equal; a large difference between the two can result in wasted energy and problems with the system. A large difference between the heat output of the primary and secondary sides also means that the generated cold energy is not being used effectively and the system is operating inefficiently, resulting in large energy losses and wasted operating costs. Therefore, by setting the fifth exclusion condition, calculations under conditions where such problems may occur can be excluded.

[0071] The sixth exclusion condition is when the secondary side delivery temperature exceeds a predetermined set tolerance (step S7-12). Note that this predetermined set tolerance is the maximum temperature allowed for the secondary side delivery temperature in terms of system design and operation. If the secondary side delivery temperature is too high, for example, it may not be possible to provide the required cooling capacity, making it impossible to maintain comfort in a room, factory, etc. Furthermore, if the delivery temperature is too high, more energy may be consumed to achieve the required cooling effect. For this reason, by setting the sixth exclusion condition, it is possible to exclude calculations under conditions where such problems may occur.

[0072] The seventh exclusion condition is when the secondary-side delivery temperature is below a predetermined set tolerance (step S7-13). The predetermined set tolerance is the minimum temperature allowed for the secondary-side delivery temperature in terms of system design and operation. If the secondary-side delivery temperature is too low, for example, the cooling capacity may be excessive, which could lead to energy waste and equipment overload. Furthermore, if the delivery temperature is too low, there is a higher risk of condensation occurring within the system, which could cause operational problems such as deterioration of piping and equipment, and even mold growth. Therefore, by setting the seventh condition, it is possible to exclude calculations under conditions where such problems may occur.

[0073] If none of the above exclusion conditions apply, the real-time controller 105 performs a power calculation for each group of heat source units for a combination of a certain chilled water flow rate and a certain chilled water outlet temperature.

[0074] The real-time controller 105 calculates the tentative power of the heat source machines included in the heat source unit for each group (step S7-14). As described above, an approximation formula showing the correspondence between the load factor and the power ratio as shown in FIG. 7 is used to calculate the power of the heat source machines included in the heat source unit. For example, the real-time controller 105 identifies the power ratio of a heat source machine by referencing the approximation formula based on the load factor of the heat source machine. The tentative power (kW) of the heat source machine can be calculated by multiplying the identified power ratio by the rated value of the heat source machine.

[0075] Similarly, the real-time controller 105 calculates the virtual power of the cooling tower fan, cooling water pump, and primary chilled water pump included in the heat source unit for each group (steps S7-15 to S7-17). As with the heat source unit, the calculation of the power of these auxiliary equipment of the heat source unit can also be done using an approximate formula showing the correspondence relationship between the load factor and the power ratio, as shown in Figure 7. Note that if the heat source unit is an air-cooled heat pump, the heat source unit does not include a cooling tower or cooling water pump, so calculations of the energy consumption of the cooling tower and cooling water pump are omitted or are calculated as zero.

[0076] Next, the real-time controller 105 calculates the total value of the provisional secondary energy (power) (steps S7-18). The secondary energy here refers to energy such as electricity and city gas obtained by converting and processing primary energy sources directly extracted from nature, such as coal, oil, natural gas, firewood, hydroelectric power, nuclear power, wind power, tidal current, geothermal heat, and solar energy. The real-time controller 105 calculates the total amount of electricity consumption (kWh) and gas consumption (Nm 3 ) and calculate the provisional sum of secondary energies.

[0077] The real-time controller 105 also calculates the total value of the tentative primary energy (power) (step S7-19). The total value of the primary energy is calculated by multiplying the amount of electricity consumed (kWh) and the amount of gas consumed (Nm 3 It can be calculated by converting secondary energy such as 1000kJ into primary energy (MJ) using a specified conversion factor and then adding up the converted primary energy values. This makes it possible to compare different units such as electricity consumption and gas consumption.

[0078] Next, the real-time controller 105 further adds up the total secondary-side energy calculated in step S7-18 and the total primary-side energy calculated in step S7-19 to calculate the total system energy. The real-time controller 105 then determines whether the total system energy calculated in the current loop's lowest-level calculation (power calculation) is lower than the total system energy produced in the previous loop's lowest-level calculation. If it is lower, the real-time controller 105 sets the value calculated in the current loop's lowest-level calculation as the optimal value (step S7-19). If the value calculated in the current loop's lowest-level calculation is equal to or greater than the value calculated in the previous loop's lowest-level calculation, the real-time controller 105 maintains the value calculated in the previous loop's lowest-level calculation as the optimal value and discards the value calculated in the current loop's lowest-level calculation. This ends the current loop's lowest-level calculation.

[0079] Next, the explanation will return to the main flow shown in FIG. 3. As described above, the real-time controller 106 performs the above-mentioned loop bottom-level calculation for all combinations of chilled water outlet temperature patterns and chilled water flow rate patterns for all groups of heat source units in a brute-force manner. When all loop bottom-level calculations are completed, a combination of chilled water outlet temperature and chilled water flow rate that optimizes (e.g., minimizes) the total energy value of the entire system is determined (step S8). The real-time controller 106 then sets the determined chilled water outlet temperature and chilled water flow rate as control target values, respectively, and determines output values ​​for controlling the various devices that make up the system so that they approach these control target values ​​(step S9). These output values ​​are transmitted from the real-time controller 106 to each device in the system as a control signal. This allows each device in the system to operate so as to minimize energy consumption. Furthermore, this optimization calculation is not performed for each heat source unit, but is performed for each group of heat source units having the same type of heat source equipment. This significantly reduces the number of power calculations.

[0080] Here, a specific example will be described with reference to Figure 8 to further deepen understanding of the optimization calculation. In this example, group R1, which is made up of multiple heat source units including the same type of heat source equipment, and group R2, which is made up of multiple heat source units including the same type of heat source equipment but different from group R1, are arranged on the primary side. The rated conditions for groups R1 and R2 are a chilled water outlet temperature of 7°C, a chilled water flow rate of 150m 3 / h, and the refrigeration capacity is 250RT (refrigeration tons). Also, on the secondary side, an air conditioning load of 330RT is placed, the temperature of the chilled water going to this air conditioning load (secondary outgoing temperature) is 9°C, and the temperature of the chilled water discharged from this air conditioning load (secondary return temperature) is 14°C.

[0081] In this case, Figure 8 shows an excerpt of a pattern in which the secondary inlet temperature is 9°C. In other words, the pattern in which the secondary inlet temperature is 9°C means that the temperature becomes 9°C when the chilled water cooled by the heat source units of group R1 and the chilled water cooled by the heat source units of group R2 are mixed on the secondary side. Pattern 1 is a pattern in which the chilled water outlet temperature of group R1 becomes 9°C and the chilled water flow rate is 100m 3 Assuming operation is performed in a pattern where the chilled water outlet temperature is 1 / h, the secondary supply temperature will be 9°C. This secondary supply temperature can be calculated using a weighted average calculation to determine the temperature of the mixed water from multiple groups R1 and R2. In the calculation formula for pattern 1 shown in Figure 8, the numerator represents the sum of the heat values ​​(predetermined coefficient x temperature difference x flow rate) of the water supplied by each group R1 and R2 (9 x 100 + 9 x 100), and the denominator represents the sum of the flow rates of both groups R1 and R2 (100 + 100). Assuming operation is performed using this combination of chilled water outlet temperature and chilled water flow rate, the load factor of group R1 will be 67%, and the load factor of group R2 will be 67%. Patterns 2 to 4 have different combinations of chilled water outlet temperature and chilled water flow rate from pattern 1 described here, but all of them have a secondary supply temperature of 9°C.

[0082] Next, based on the load factors of groups R1 and R2 calculated for each pattern, the power (kW) for each group R1 and R2 is calculated by referencing the approximate formula shown in Figure 7. Then, a determination is made as to which pattern requires the lowest power, and the pattern with the lowest combination of chilled water outlet temperature and chilled water flow rate is determined as the optimal value. In pattern 2, the load factor for group R1 is 80% and the load factor for group R2 is 53%. In pattern 3, the opposite is true: the load factor for group R1 is 53% and the load factor for group R2 is 80%. Comparing patterns 2 and 3, for example, if group R1 is more efficient, and the power for each group R1 and R2 is calculated by referencing the approximate formula, pattern 2 will require less power (i.e., be more energy-efficient).

[0083] In the above description of the present invention, the embodiments of the present invention have been described with reference to the drawings in order to express the contents of the present invention. However, the present invention is not limited to the above embodiments, and includes modifications and improvements that are obvious to those skilled in the art based on the matters described in the present specification. [Explanation of symbols]

[0084] 11...Refrigerator (heat source machine R) 12...Primary chilled water pump 13...Cooling tower 14...Cooling water pump 15...Cold water primary outgoing piping 16...Cold water primary return piping 17...Temperature sensor 18...Flow meter 19...Temperature sensor 21...Cooling water piping 31...Bypass 39...Cold water secondary forward piping 41...Cold water secondary return pipe 43...Temperature sensor 51...Temperature sensor 53...Flow meter 85a, 85b...Cold water secondary pump 100...Heat source control system 101...Heat source unit 102...Outbound header 103...Return header 104...Air conditioner (AHU) 105...Real-time controller (control device) 106...Outside temperature and humidity sensor 107...Memory unit

Claims

1. The air conditioning load located on the secondary side, a forward header for sending out chilled water or hot water (hereinafter collectively referred to as "chilled or hot water") toward the air conditioning load; a return header for receiving cold or hot water delivered from the air conditioning load; a plurality of heat source units located on a primary side connected to the supply header via a primary supply pipe for chilled or hot water and connected to the return header via a primary return pipe for chilled or hot water; a control device that controls the heat source unit, Each of the heat source units is a primary cold / hot water pump for controlling the flow rate of the cold / hot water in the primary cold / hot water return pipe; a heat source machine that cools the cold water or heats the hot water sent from the primary cold / hot water pump through the primary cold / hot water return pipe, and sends the obtained cold / hot water to the send header through the primary cold / hot water send pipe, The control device The energy consumption, running costs, and CO ２ and performing an optimization calculation to determine, for each heat source unit, a control target value for the chilled / hot water flow rate sent from the primary chilled / hot water pump to the heat source machine and a control target value for the chilled / hot water outlet temperature sent from the heat source machine to the chilled / hot water primary inlet pipe, so that the evaluation index for all of the plurality of heat source units is optimized; In the optimization calculation, the heat source units including the heat source machines of the same type are grouped, and for each group, a combination of a plurality of patterns of chilled / hot water flow rates and a plurality of patterns of chilled / hot water outlet temperatures is exhaustively searched to calculate the evaluation index for each of the combinations, and a control target value of the chilled / hot water flow rate and a control target value of the chilled / hot water outlet temperature for each of the heat source units are determined so that the evaluation index for all of the plurality of heat source units becomes an optimal value. Heat source control system.

2. The type of the heat source machine is two or more types selected from the group consisting of an inverter-controlled turbo refrigerator, a constant-speed turbo refrigerator, an absorption-type hot and cold water generator, an air-cooled heat pump, a screw chiller, and an exhaust heat recovery refrigerator. The heat source control system according to claim 1 .

3. In the optimization calculation, the combinations that satisfy a predetermined exclusion condition are excluded from the calculation of the evaluation index. The heat source control system according to claim 1 .

4. The exclusion conditions are: a first condition that the temperature difference between the hot and cold water going to and returning from the heat source unit is below a lower limit value; A second condition in which the load factor of the heat source machine is equal to or greater than an upper limit value; A third condition in which the load factor of the heat source machine is equal to or lower than a lower limit value; a fourth condition that the flow rate values ​​on the primary side and the secondary side exceed set values; a fifth condition in which the difference between the heat quantity values ​​on the primary side and the secondary side exceeds a set value; A sixth condition in which the secondary side supply temperature exceeds a set allowable value; and a seventh condition that the secondary side supply temperature is lower than a set allowable value; Contains one or more of the following conditions: The heat source control system according to claim 3 .

5. In the optimization calculation, the number of patterns of the chilled / hot water flow rate and / or the number of patterns of the chilled / hot water outlet temperature used in the current optimization calculation is reduced based on the control target value of the chilled / hot water flow rate and the control target value of the chilled / hot water outlet temperature that became the optimal values ​​in the previous optimization calculation. The control system of claim 1 .

6. In the optimization calculation, the number of patterns of the chilled / hot water flow rate and / or the number of patterns of the chilled / hot water outlet temperature used in the optimization calculation is increased or decreased depending on the number of groups. The heat source control system according to claim 1 .

7. A control method for a heat source control system, comprising: The heat source control system includes: The air conditioning load located on the secondary side, a forward header for sending out chilled water or hot water (hereinafter collectively referred to as "chilled or hot water") toward the air conditioning load; a return header for receiving cold or hot water delivered from the air conditioning load; a plurality of heat source units located on a primary side connected to the supply header via a primary supply pipe for chilled or hot water and connected to the return header via a primary return pipe for chilled or hot water; a control device that controls the heat source unit, Each of the heat source units is a primary cold / hot water pump for controlling the flow rate of the cold / hot water in the primary cold / hot water return pipe; a heat source machine that cools the cold water or heats the hot water sent from the primary cold / hot water pump through the primary cold / hot water return pipe, and sends the obtained cold / hot water to the send header through the primary cold / hot water send pipe, The control method includes: The control device calculates the energy consumption, running costs, and CO ２ and performing an optimization calculation to determine, for each heat source unit, a control target value for the chilled / hot water flow rate sent from the primary chilled / hot water pump to the heat source machine and a control target value for the chilled / hot water outlet temperature sent from the heat source machine to the chilled / hot water primary inlet pipe, so that the evaluation index of the entire plurality of heat source units is optimized. In the optimization calculation, the heat source units including the heat source machines of the same type are grouped, and for each group, a combination of a plurality of patterns of chilled / hot water flow rates and a plurality of patterns of chilled / hot water outlet temperatures is exhaustively searched to calculate the evaluation index for each of the combinations, and a control target value of the chilled / hot water flow rate and a control target value of the chilled / hot water outlet temperature for each of the heat source units are determined so that the evaluation index for all of the plurality of heat source units becomes an optimal value. Heat source control method.

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